A3 IBI'BESTLGATIOB OF THE HEAbTH A N D P A T I G U E EFf ECTS B E S U L T I N G

P R C B V I C E 0 XISPLAY TEWWINAL USAGE

Helen Dorothy Bard

3,Sc. Honors [Kines io luyy) S imcn fraser U n i v e r s i t y 1980

THESIS SUBflfTTED If4 Pi iRTIAL FOtPZLLHERT OF

THE REQTJIitEHENTS PO3 THE DEGWEE OF

MASTER OF SCf BMCE {RINESXEIIICGY)

in the Degartment

of

Kines i o l o g y

@ Helen Dorothy Ward 1983

S f H C N FRASEP U N I V E R S I T Y

November 1983

A f f r i g h t s reserved. This work m y n o t be r e p r o d u c e d i n whale or in part, b y photocopy

ar other means, a i t h o u t p@rmiss ion of the author,

APPROVAL --

Name: Helen Dorothy Ward

Degree: Mas te r of S c i e n c e ( K i n e s i o l o g y )

T i t l e o f T h e s i s : An I n v e s t i g a t i o n o f t h e H e a l t h and F a t i g u e

E f f e c t s R e s u l t i n g from Video D i s p l a y

Terminal Usage

Examining Committee:

Chairman: D r . D . Goodman

~d J. Dickinson S e n i o r S u p e r v i s o r

D r . T . J . Sfnith

D r . ?3?-heyerstein E x t e r n a l Examiner Psychology Department Simon F r a s e r U n i v e r s i t y

Date Approved: i

PART I AL COPYR I GHT L I CENSE

I hereby g ran t t o Simon Fraser U n i v e r s i t y the r i g h t t o lend

my thes is , proJect o r extended essay ( t h e t i t l e o f which i s shown below)

t o users o f t he Simon Fraser Un ive rs i t y L ibrary, and t o make p a r t i a l o r

s i n g l e copies on ly f o r such users o r i n response t o a request from t h e

l i b r a r y o f any o the r un ive rs i t y , o r o the r educational i n s t i t u t i o n , on

i t s own behalf o r f o r one o f i t s users. I f u r t h e r agree t h a t permission

f o r m u l t i p l e copying o f t h i s work f o r scho la r l y purposes may be granted

by me o r the Dean o f Graduate Studies. I t i s understood t h a t copying

o r p u b l i c a t i o n o f t h i s work f o r f i n a n c i a l gain sha l l no t be allowed

w i thou t my w r i t t e n permission.

T i t l e o f Thesis/Project/Extended Essay

Author:

( s igna tu re )

(name

(date)

B BS"I&CT

Tire v i d e o d i s p l a y t e r ~ i n a l 4VL)T) h a s become an i n t e g r a l

p a r t of t h e n o d e r n o f f i c e , While i n c r e a s e d p r o d u c t i v i t y h a s b e e n

e m ~ h a s i z e d , t h e needs cf t h e o p e r a t o r h a v e o f t e n b e e n

o v e r l o o k e d . C o a p l a i n t s from VDT w o r k e r s i n c l u d e symptoms o f

v i s u a l d i s c o s f o r t d u e t o poor image q u a l i t y a n d g l a r e ,

m u s c n l o s k e l e t a l d i s c o m f o r t due t o p o o r v o r k s t a t i o n d e s i g n and

s o m a t i c d i s c o a f o r t due t o stress,

A work e n ~ i r o n ~ e n t suf a e y g n e s t i c n n a i r e bas d e s i g n e d t o

assess t h e p h y s i c a l a n d p s y c h o s o c i a l i n f l u e n c e s o n t h e h e a l t h o f

1100 V D T operators in the ' B e % York district. A h i g h e r percentage

of p r o f e s s i o n a l V D T o p e r a t o r s e x p e r i e n c e d t h e g r e a t e s t number of

h e a l t h - r e l a t e d c o m p l a i n t s , S t r e s s f a c t o r s were p a r t i c u l a r l y

r e l e v a n t t o the ~ r o f e s s i o n a l workers, C o m p l a i n t s a b o u t t h e

-t. - - 1 - - p z i y a i ~ u 1 env i ion i i t ent , p a r t i c u i a z i y t h e q u a l i t y o f room a i r , were

e x p r e s s e d b y p r o f e s s i o a a l VDT o p e r a t o r s , Whea d a t a frcm o n e

buildins which housed e a c h ~ r o f e s s i o n a l a n d clerical V D T a n d

non-VDT g r o u p were a n a l y z e d , differences i n c o m p l a i n t s o f t h e

physical environment and h e a l t h s y r ~ p t o ~ s sere aiainized. On1 y

for stress f a c t o r s was t h e r e a s i g n i f i c a n t d i f f e r e n c e i n t h e

r e s p o n s e s [ c h i - s q u a r e d a n a l y s i s , p<0-05) i n rahicti p r o f e s s i o n a l

w o r k e r s h a d a h i g h e r p e r c e n t a g e ~f c o m p l a i n t s , An o v e r v i e u of

t h e d a t a r e v e a l s t h a t sy ra~ tc rn t s GL p o o r h e a l t h a p p e a r related t o

a i r q u a l i t y c o ~ p l a i n t s .

The e x p e r i m e n t a l s e s s i o n c o n s i s t e d of a two-hour VET work

p e r i o d f o l l o a e d by a f i f t e e n n i n u t e rest b r e a k . T h e same t w e l v e

s u k j e c l s served a s controls d u r i u g another two-hour p e r i o d

v i t h o u t VDT exposure. Critical. f ficker fusion f r e q u e n c y ,

c o n t r a s t t h r e s h o l d a t YO c y c l e s p e r eleven citt and accommodative

f a c i l i t y s h o w e d s i g ~ k f i c a n t l y d i f f e r e n t d e c r e m e n t s i n v i s u a l

f u n c t i o f i af ter t h e two-hour s e s s i o n a s compared to before

( r e p e a t e d m a s n r e s B B O V B , p<0.05), for c o n t r a s t t h r e s h o l d a t 30

c y c l e s per f l i e v e n ca, accommodative respnse and the c o n t r o l

s e s s i o n s no s i g n i f i c a n t d i f f e r e n c e s were d i s c e r n e d , Ten of

fourteen d i p o l a r p s y c h o l o g i c a l f a t i g u e indicators showed

s i g n i f i c a n t d i f f e r e n c e s a f t er the experintental s e s s i o n f rorn

before w h i l e none of t h e c o n t r o l a e a s u r e s d i d {repeated measures

ANOVA, ~ < Q . 0 5 ] . B o ~ o v e r y was evident i n t h a t n o s t emperimentaf

v i s u a l f u n c t i o n and p s y c h o l o g i c a l f a t i g n e sar iabf es r e t u r n e d t o

prev ious l e v e l s . The r e s u l t s of t h e experinaent indicate t h a t the

recommendation of a two-hour VDT e x p o s u r e p e r i o d may b e too

lonrj.

8C$jgDOlPsLEDGEaE%TS

I would like to thank all t h e members of my t h e s i s

c o ~ a i ttee f o r their invaluable support and encouragtrrtent. I am

indebted to Dr. Jantzi f o r h i s advice on visual function

measurement. TlfS L t d . ~ r o v i d e d needed s u p p o r t by allowing me to

c o n t r i b u t e majar i n p u t i n t o the H e a l t h and Uork Environaent

survey conducted i n cooperation with local 90 of the Office and

~ r o f e s s i o n a l Employees faternat ional Union, I thank Diane

Hartell-Rokayashi ia particular f o r a d m i n i s t e r i n g the

questionnaire i n He% York. B y husband, Richard gave Be hope and

love w h e n I needed it ~ o s t . Thank you,

B a t i o n a l e for t h e E x p f r i m e n t ......................... 6 8

Purpose ........................*..................... 8A

Raterials and HeLhods .......................*...*..* -82 Results .............................................. 86

D i s c u s s i c n .................. . ~ o . . t . w . . . ~ . . . . I . t L . ~ . ~ . 9 9

References .................................................. 103 A ~ p e n d i x e s .............................................. * . . * I l Q

LIST QP TABLES

TABLE

1 3ob Type by Percent C o ~ p f a i n i n g of Health Problems at Least O n c e a feek ,,,,,..,,,..., ...... ,,..,.,,, 49

~ o b Type C y Eercent C o i q h i n i n y of Stress ,, ., , , .. , , , , 54

Job Type by Ability to Control Eavircnroent ,,,.,,,..,, 57

Frequency of VDT U s e by Complaints Found to be Significantly Different Eetweea Groups b y Chi-Squared Analysis {p<O,O5) . , , , . . . , , , , . . , , , . , , , 59

~ o b T y p e versus Stress in a L j u i l d i n g where Stress was Significantly Different Eetueea Groups [Chi-squared Analysis, p<0-05 ) .-.,., -.*,,,, .,,.-', 62

v i i i

5 Mean Expsr itnenta 1 Changes in Accoa&~dat ive F a c i l i t y , , , , , , , . , , , , , . , , , ,, ,. ,, , , , , , , , . . . ,, ,, , . , . 91

6 Hean Contrast Threshold at 40 cycles/llcm - E x p e r i a ~ n t a i vs Contro l , , . , , , , , ,, , , . , , , , . ., *, . . 95

A, The Health E f f e c t s of VD'E Ose

The c h a r a c t e r o f . t r a d i t i o n a l office work h a s u n d e r g o n e a

m e t d ~ o r p h o s i s nct unlike t h e one created t h r o u g h the

i n t r o d u c t i o n of t h e t y p e w r i t e l c o v e r a h a l f c e n t u r y ago , T h e

v i d e o d i s p l a y t e r ~ i n a l [PDT or VDD) , t h e T s V . - l i k e c o m p u t e r

tertninal, has becore an integral part o f t h e sodern o f f i c e , With

i t s e v e r e x p a n d i n g r a n g e of a p p l i c a t i o n s t h e VDT has p e r m e a t e d a

w i d e r a n g e of g o v e r n m e n t a n d p r i v a t e i n d u s t r i e s . P u b l i s h i n g ,

c o t r r a u n i c a t i o n s , b a n k i n g a n d a i r l i n e c o n c e r n s are b u t few

exaiiiples. y"uTs even beg.Gn to invridz "L- ----A. ..--.. -' ' " A

CUT a a ~ i t - ~ u a ~ l W L L U C

hotrre a s a t t e s t e d t o by t h e r e c e n t p r o l i f e r a t i o n of p e r s o n a l home

computers a n d c o m p u t e r garaes, T h e r e a r e currently a t l e a s t

250 ,000 o f t h e v i d e o d i s ~ l a y t e r n t i n a l s i n use across this

c o u n t r y [Donoghue, 1 9 8 3 ) - T h e Hational I n s t i t u t e f o r

O c c u p a t i o n a l S a f e t y and B e a l t h (MIDSH) e s t i n a t e s t h a t s e v e n

a i l l i o n workers in t h e U,S. now o p e r a t e Y D T s {Bergntan, 1980). By

1935 the nuinber of c o o p u t e r s , t e r m i n a l s a n d e l e c t r o n i c o f f i c e

machines i n t h e U n i t e d States is expected t o grow t o 35 & i l l i o n ,

which w i l l amonrtt t o a b o u t one c o ~ p u t e r - b a s e d maaltine f o r e v e r y

th ree persons employed i n t h e w h i t e - c o l l a r work force [ E i h i s e a n d

R i n a l d u c c i , 1981), W i t h t h e c o n t i n u a t i o n of t h i s trend we s h a l l

see, a s Ustberg s u c c i n c t l y p u t s it, t h e **rapid e v o l u t i o n of t h e

s p e c i e s honro t e r m l n o - v i d e n s { t h e VDT-viewing man)*i {(Ostberg ,

1980)

The ina jos s e l l i n g point cf t h e V D f s h a s been t h e p o t e n t i a l

i n c r e a s e i n p r o d u c t i v i t y which t h e y a f f o r d , U n f o r t u n a t e l y , t h e

needs of t h e huaan o p e r a t o r have o f t e n b e e n o v e r l o o k e d . Almost

u n i v e r s a l l y the v i d e o display t e r a i n a l s a r e i n s t a l l e d i n t o

e s t a t l i s h e d o f f i c e s u r r o u n d i n g s rather t h a n w i t h i n a n

e n v i s o n ~ e n t sore colltpatible v i t h opsratcr colrmfort and

~ r o t e c t i o a . As a r e s u l t "the d i a l o g u e w i t h t h e c o m p u t e r i m p l i e s

n o t o n l y uncomfortable p h y s i c a l c o a d i t i o n s a t work i v i s u a l ,

a c o u s t i c , c l i a a t i c c o n d i t i o n s ) b u t a l s o i n e n t a l strain and a aev

t y ~ e of c o n s t r a i n t on p r o d u c t i v i t y 1 * [Bey e t aL,, 1977).

Bore i l l u s t r a t i v e of t h i s f a i l u r e is t h e g r o w i n g

d i s e n c h a n t a e n t aad r e s i s t a n c e of the o p e r a t o r s t o m r d s u s i n g t h e

uui ts. I n c r e a s i n g concera oves t h e potential health h a z a r d s

w h i c h Bay accrue t h r o u g h f u l l - t i e t e u s e of t h e e t a c h i n e s is b e i n g

voiced, For i n s t a n c e , 250 ccnference t y p i s t s a n d t r a n s l a t o r s a t

t h e U n i t e d N a t i o n s s t a g e d a w a l k o u t t o p r o t e s t t h e m a n a g e m e n i t s

refusal t o s h u t dovn t h e VDTs u n t i l a h e a l t h study had keen

c a r r i e d out ( O s t b e r g , 3979) . A c c o r d i n g t o t h e Director of

Research a n d P n f o r s a t i a r at t h e Bewspaper Guild i n t h e O,S,, nNo

o t h e r f a c t o r i n t h e work e n v i r o n ~ e n t n o t i n d e e d , all o t h e r s

c o a b i n e d - has e v e s created such a torrent o f h e a l t h c o ~ p l a i n t s

a n d problelr ts a s h a v e V D T s w {Berginan, 1980),

T h e v i s u a l d i s ~ l a y t e r m i n a l . p r o v i d e s a quick a n d c c n v e n i e n t

means o f a c c e s s i n g and z u a n i g u l a t i a g t h e s t o r a g e o f a c e n t r a l

c o m ~ u t e r . It c a a ~ r i s e s t h r e e main e l e m e n t s : a d i s p l a y screen, a

k e y b o a r d a n d a n e l e c t r o n i c s p a c k w i t h p c v e r s u p p l y . These may

a l l h e c o n t a i n e d w i t h i n a metal, f i b r e g l a s s o r p l a s t i c housing

w i t h t h e o p e r a t i n g t e m F e r a t u r e k e p k stabilized by means o f a n

internal fan ,

T h e c a t h o d e r a y t u b e , o r CBT, is the b a s i c e l e m e n t a r o u n d

u h i c h d i s p l a y terminals a re c o n s t r u c t e d . The CRT is b a s i c a l l y a n

e v a c u a t e d g l a s s t u k e w i t h a n e l e c t r o n gun a t one e n d a n 8 a

screen which is c o a t e d v i t h a l i g h t e a i t t i n g phosphor a t t h e

o t h e r , When a h i g h v o l t a g e is a g ~ l i e d t o t h e e l e c t r o n gun the

s t r e a m cf e l e c t r o n s produced is f c c u s s e d a n d d e f l e c t e d ky a n

e l e c t r o n i c l e n s s y s t e ~ t o t h e f a c e of the s c r e e n by means of a n

e l e c t r o s t a t i c o r e f e c t r o a a g n e t i c force. T h i s moving e l e c t r o n

beaa s c a n s a c r o s s t h e e n t i r e s c z e e a i n a series of r e g u l a r l y

s p a c e d h o r i z o n t a l l i n e s , a c t i v a t i n g tiny g l o w i n g g h o s ~ h o r dots.

Poc t h e cotnmonly used "ref resherw CCWTs t h e e l e c t r o n beam

s w i t c h e s on a n d off s o t h a t a m a t r i x o f dots is S o r ~ e d a c c o r d i n g

t o t h e d e s i r e d s h a g € of t h e c h a r a c t e r , The r a t i o of t h e h e i g h t

t o width of t h i s m a t r i x r a n g e s from a 5 x 7 d o t ~ a t r i x to a 7 x

9 d o t m a t s i x , Host 'VDT s c r e e n s a r e a b o u t 15 t o 20 cm h i g h and 20

t o 2 5 c~ wide a n d h a v e a n o r m 1 c a p a c i t y of u p t o 80 c h a r a c t e r s

p e r ' l i n e { C a k i r e t a l , , 1979; RcGra th , 1981).

11. A Literatare Beview of VDT B r j a l t L Efdects

T h e t o p i c a l i s s u e o f w h e t h e r VDTs pose a r a d i a t i o n h a z a r d

w i l l n o t k f c o v e r e d i n detail, The e x p e r i m e n t a l p r o t o c o l a n d

q n e s t i o n n a i r e s u r v e y u s e d f o r t h i s t h e s i s d o n o t ~ r o v i d e t h e

scope t o c o v e r t h e r a d i a t i o n i s s u e . I n a d d i t i o n , numerous r e c e n t

s t u d i e s of t h i s p o t e n t i a l h a z a r d have been unan imous i n t h e i r

c o a c l u s i o n t h a t no h a r m f u l l e v e l s o f x-ray aad n c n - i o n i z i n g

r a d i a t i o n e x i s t . A f o c a l i s s u e i s t h e e f f e c t of l o n g t e r ~

exposure t o low l e v e l s of elect r o w a g n e t i c r a d i a t i o n , P o r

- - - - - a n a ~ p ~ e , the 6.5, ci i frent iy hds a11 e x p ~ u r e ~ t d n d a r d t o

n o n i o n i z i n g r a d i a t i o n of 10 mu/c~2, Yet, a c c o r d i n g t o D r . R o r r i s

S h o r e , Director of t h e D i v i s i o n o f B i o l o g i c a l Effects a t t h e

Enreau o f R a d i o l o g i c a l H e a l t h i a 1977, [ c i t e d i n l i l e w e l l i n g ,

19 80)

Vhere are m i s t a k e s t h a t h a v e b e e n ~ a d e i n t'fie past, a n d f would hope t h a t t h e s e could be a v o i d e d , A s p e c i f i c exaiiiple i s t h e c e r t i f i c a t i o n o f s a f e t y o f 30 m v / c d f o r i n d e f i n i t e humaa e x C o s u r e i n t h e a b s e n c e of a n y s t u d i e s i n a n i m a l s o r i n man t h a t tested t h e c h f o n i c o r l i f e t i m e effects of e x p o s u r e t o 70 mv/cn2, S u c h c e r t i f i c a t i o n , based o n i g n o r a n c e , s t r a i n s t h e c r e d i b i l i t y of a l e v e l that is recolatntended as being a d e q u a t e t o F r o t e c t h e a l t h a n d s a f e t y p a r t i c u l a r l y of t h e general p o p u l at ioa .-

I n Canada , r e c e n t p u b l i c i t y h a s c e a t r ~ d on group3 o r f l c l a s t e r s q z

of a b n o r m a l p r e g n a n c i e s [ m i s c a r r i a g e s a n d b i r t h d e f e c t s ) a mong

some V U T r o r k e r s w h i c h may be doe t o c h a n c e a l o n e , T h e

c o n t r o v e r s y still b a s n o t heen s e t t l e d ; c u r r e n t l y unde r

c o n s i d e r a t i o n a r e a ~ ~ c n d m e n t s t o the Canada L a b o r c o d e which

would a l f o u p r e g n a n t wosen to transfer away from V D T s [Labour

Canada. 1982)

T h e Svia~torng qf V i s u a l D i s c c n f o r t --

T h e c o m p l a i n t s e x g r e s s e d by o p e r a t o r s of VDTs h a v e i n c l u d e d

s u c h o c u l a r sylaptoms a s t h e e y e s f e e l i n g t e n s e , h e a v y , d r y ,

i t c h y 03: u n c o n a f o r t a b l e . A burai i iy p a i n gap be f e l t and t h e e y e s

may h e g e n e r a l l y t e n d e r on F r e s s u r e , There may a l s o be a n a c h e

f roa w i t h i n o r b e h i n d t h e e y e s o r t w i t c h i n g of t h e e y e a u s c l e s ,

The v i s u a l symptons may i n c l u d e soae d i f f i c u l t y i n f i x a t i n g

o b j e c t s and i n gazing i n c e r t a i n d i r e c t i o n s f o r more t h a n a

short p e r i o d , V i s i o a Bay be b l u r r e d , s i n g l e o b j e c t s may seem t o

h a v e c o l o r f r i n g e s o r a p p e a r d o u b l e a n d t h e r e m y b e subsequent

p r o b l e m s i n watching a t e l e v i s i o n o r ~ o v i e s c r e e n {Ostberg,

l 9 7 5 ) ,

C u n n a r s o n a n d C s t b e r g 11977) f o r example, found 755 of the

i n t e r v i e w e d VDT o p e r a t o r s ( t o t a l l ing 48 perscas) e x p e r i e l a c e d

some s o r t o f e y e p r o b l e m e v e r y d a y or a few times p e r w e e k , O f

t h e s e , 46% r e p a r t e d that t h e p r o b l e m s were great o r ve ry g r e a t ,

T h e c o m p l a i n t s were d e f i n e d p r i m a r i l y a s e y e f a t i g u e (60W),

b u r n i n g , f e e l i n g of g r a v e l cr i t c h i n g i n t h e i y e s (483). d o u b l e

o r 'Dl ursed v i s i o n (19%) a n d e y e r e d n e s s (155%) T h e jot: f a c t o r s

perceive3 a s t h e m o s t e y e s t r a i n i n g were l o o k i n g a t the d i s p l a y

screen (F iBX) , shiftiny from s c r e e n r e a d i n g t o m a n u a l s ( 1 5 % ) . a n d

r e a d i n g m a n u a l s (294). More c o n s e r v a t i v e estimates of v i s u a l

p r o b l e m s were g i v e n t y Grandjean (1980) . He e s t i m a t e d t h a t i n

g e n e r a l , 10 t o 1 5 % of t h e VDT o ~ e r a t o r s had a l m o s t d a i l y p a i n s

o r i r r i t a t i o n s i n t h e i r e y e s , w h i l e Y O t o 5 0 1 r e p o r t e d

o c c a s i o n a l i m p a i r a r e o t s . L a u t l i et a l . (1980) d e m o n s t r a t e d t h a t

t h e s e o c u l a r S y n F t a E s may p e r s i s t d u r i n g t h e e v e n i n g u n t i l

bedt ime .

" A l l t h e s e a u t h o r s c o n c l u d e t h a t c o n t i n u o u s work o n VDUs is f o r a r e l e v a n t p a r t of t h e o p e r a t o r s - a s s o c i a t e d w i t h a p r o n o u n c e d i m p a i r m e n t of t h e w e l l - b e i n g i n t h e sense o f e x c e s s i v e f a t i g u e of t h e e y e s of ten a s s o c i a t e d w i t h p a i n f u l r e a c t i o n s a n d d e c r e m e n t s cf v i s u a l p e r f o r m a n c e s , I n g e n e r a l , t h e s e i m p a i r m e n t s are c o n s i d e r e d r a t h f r a s r e v e r s i b l e a n d f u n c t i o n a l t r o u b l e s t h a n a s p e r s i s t a n t i n j u r i e s t o h e a l t h " { G r a n d j e a n , 1980) .

C l i n i c a l e v i d e n c e ( as ci ted i n D a i a o f f , 1979) is p s o v i d e d

by S p a r k s a n d Hebert B o t h r e s e a r c h e r s i n d i c a t e d t h a t a l a r g e

n u m b e r of v i s u a l c o m p l a i n t s a n d r e q u e s t s f o r c o r h e c t i v e l e n s e s

h a v e b e e n made by YDT workers,

It is i m p o r t a n t t o d e t e r m i n e w h e t h e r e y e p r o b l e m s a p p e a r

w i t h a g r e a t e r t h a n n o r m a l i n c i d e n c e among V D T o p e r a t o r s . For

e x a m p l e , S t o n e (1481) c i t e d B r u a d r e t t S s study i n w h i c h 40% o f

g e n e r a l o f f i c e w o r k e r s c o m p l a i n e d o f o c u l a r d i s c o m f o r t ,

All t h e r e s e a r c h o n YDT o p e r a t o r s to d a t e h a s c o n c u r r e d

w i t h Rey and f l e y e r l s (1980) c o n c l u s i o n t h a t y*VDU o p e r a t o r s

c o m p l a i n e d more of t e n of v i s u a l i l apa i r r aen t t h a n o t h e r o p e r a t o r s

o f ' t h e same ageM. T h i s d i f f e r e n c e was i n c r e a s e d w i t h work

d u r a t i o n a n d 75% of the VDU o p e r a t o r s caaaplained after working 6

t o 9 h o u r s i n f r o n t of t h e screen.

Gunnarsson a n d O s t b e r g 11977) showed t h a t t h e r e was a l a r g e

v a r i a t i o n i n v i e w i n g d i s t a n c e s r e q u i r e d d u r i n g t h e c o u r s e of a

w o r k day. A p p r o x i ~ a t e l y 38% of o p e r a t o r v i e w i n g time was

a l l o c a t e d t o the wclose v i s i o a n r a n g e o f d i s t a n c e s (0-45 cm) ;

4 7 % t o t h e trtedian r a n g e (45-100 ca) a n d 1594 t c the f a r r a n g e

[ g r e a t e r t h a n clae ~treter) , The a u t h o r s s u g g e s t e d t h a t t h i s d e g r e e

of s a r i a t i c n i n v i e w i n g d i s t a n c e s p l a c e d a heavy delaand on t h e

v i s u a l c a p a c i t i e s of t h e o p e r a t o r s . C a k i r e t a l , (1979) a l s o

p o i n t out t h e b u r d e n i n v c f wed i n c h a n g i n g v iewing d i s t a aces

b e t v e e n the s c r e e n , keyboa rd and document, They r e c o ~ a e n d e d t h a t

v i s u a l o b j e c t s s h o u l d be i d e a f l y s i t u a t e d a t t h e same d i s t a n c e

f r o n t h e users-yes . R e c e n t f i n d i n g s i n a study b y Quebec

o p h t h a l ~ o l o g i s t s s u p p o r t e d t h i s o b s e r v a t i o n , T h e n o s t common

v i s u a l c o m ~ l a i n t s by VPZ' o p e r a t o r s were found t o &crease when

the users l e a r n e d t o glance back and forth less o f t e n from t h e

screen to t h e hard copy (The P r o v i n c e , 1982).

This notion o f l o o k i n g a t f i x e d distances h a s no t r e c e i v e d

unanimous s u p p o r t , C u r l e n 11982) e ~ p h a s i z e d t h a t s t a r i n g a t a

fixed d i s t a n c e can cause c i l i a r y auscle spasm and s u b s e q u e n t

v i s u a l f a t i g u e . R e reconasends % x e r c i s i n g W the a c c o m o d a t i v e

s y s t e m by s h i f t i n g one8s g a z e t o o b j e c t s a t d i e f e r i n g d i s t a n c e s -

According t o Krueger ('1930) t h e common recoiamendat ion o f a n

equal v i e w i n g d i s t a n c e for t h e display, keybo&d and document

d e r i v e s f rout t h e f a c t t h a t acconamodat i o n a n d c o n v e r g e n c e dentand

for d i f f e r e n t d i s t a n c e s r e q u i r e time, A t t h e same time such a

r e c o m w ~ n d a t i o n means t i r i n g s t a t i c muscu l ar work for t h e c i l i a r y

A prolslent t h a t r e s u l t s when t h e VDT o l e r a t o r s p e n d s a

p r o l o n g e d a m u n t o t time f o c u s s i n g a t a f i x e d d i s t a n c e and n o t

p e r i o d i c a l l y s h i f t i n g h e r gaze t o a fas point, is f a t i g u e of the

intrinsic a n d e x t r i n s i c e y e i i tuscfes. E v e n t u a l l y t h i s f a t i g u e Bay

cause a d e c r e a s e d a b i l i t y t o a a i n t a i n a f i x e d g a z e o r f o c u s o n

distant o b j e c t s , Double v i s i o n nay b e a r e s u l t i n t h e more

e x t r e m e cases [Arnd t , 19801, The e y e s must b e a l l o w e d t o '3resl;'f

a n d a n e x p t y field s u r r o t t n d i n g t h e i m e d i a t e t a s k is t o b e

a v o i d e d [ O s t b e r g , 49753= Coe e t al, j1980) i n d i c a t e d t h a t t h e

v o r k p l a c e s of i n p u t V E T o p e r a t o r s had a r e l a t i v e l y low

p e r c e n t a g e [ 5 2 % ) of d i s t a n t l o c a t i o n s w h e r e t h e y could l o o k i n

o r d e r t o rest their e y e s Eroet close work, T h e s e o p e r a t o r s a l s o

r e p u r t e d higher l e v e l s of t h e i r r i t a n t c o m g a n e n t of a s t h e n o p i a ,

L i g h t / r d a r k a d i a ~ t a t i o n is t h e a b i l i t y o f t h e r e t i n a t o

change its s e n s i t i ~ i t y w i t h v a r y i n g i l l m i n a t i o n l e v e l s , It is

s u g g e s t e d t h a t t h i s c a n be a d v e r s e l y a•’ f e c t e d By the l a r g e

c o n t r a s t s of t h e s u r f a c e f u r a i n a n c e s b e t w e e n s c r e e n a n d s o u r c e

d o c u n e n t s , a s well a s b e t w e e n t h e s c r e e n a n d s u r r o u n d i n g

e l e i n e n t s , l i k e windows, rsalls a n d l i g h t s o u r c e s ( G r a n d j e a n ,

3980) - D u r i n g r e a d i n g , and most p r o b a b l y , VDT-vievirg , t h e b l i n k

r a t e decreases fro@ a n o r m a l r a t e o f t v e l ~ e t i n e s pe r m i n u t e t o

a b o u t f i v e times p e r m i n u t e , which r e s u l t s i n c o r n e a l a n d

con'junctival d e s s i c a t i o a . This a c c o u n t s f o r t h e sy~~ torns of

! * b u r n i n g , g r i t t i n e s s * " and. a l s o p a r t l y for "tirednessii .

The isage q u a l i t y of t h e VDT i s d e t e r ~ t t i n e d b y a numbes of

i n t e r a c t i n g p a r a n e t o r s , T h e s e i n c l u d e : (1) c h a r a c t e r p a t t e r n s

(2) c h r o m a t i c i t y 33) l u r t l i n a n c e a n d c o n t r a s t a n d {4) s t a b i l i t y .

C h a r a c t e r Pa t t ~ s n s

Dot m a t r i x c h a r a c t e r g a t e r a t i o n is mcst c c a t ~ o n l y d e f i n e d b y

a selected set of d c t s Erotg a r e c t a n y t l l a c m a t f i x o f d o t s a s t h e

e l e c t r o n beaa s c a n s t h r a u g h i t s rcster p a t t e r n , Por v i e v i n g a t a

clcse r a n g e , d o t i a a t r i c e s o f 5 x 7 o r 7 x 9 are c o n s i d e r e d t o be

l_ - - - A u e s r ~ O E t h e r e c u y u i t i c n oS smii iet iers , the 7 x 9 m a t r i x

being p r e f e r a b l e (fiosenbaum, ? 9 8 l ) , If t h e c h a r a c t e r s are too

l a r g e t h e d o t s will a p p e a r t o separate* T h e o p t i m l c h a r a c t e r

s i z e w o u l d subtend a b o u t 20 - 25 a inute s of arc a t the eye

( a b o u t 3,0 m a t a 50 cnt v i e ~ r i n g distance), A w i d t h of 70-809: of

character h e i g h t is r e c o a a e n d e d , C h a r a c t e s and fine spacing i s

a l s o i m p o r t a n t for good l e g i b i l i t p , B e t w e e n 20% a n d 5 0 % of t h e

c h a r a c t e r w i d t h is recommended for c h a r a c t e r spacing whereas

i n t e r l i n e spacing s h o u l d be b e t w e e n 1001 and 150% of t h e

c h a r a c t e r height, I h e display c a p a c i t y of moss t e x t i n p u t a n d

e d i t i n g V D T s t h u s t y p i c a l l y conta ins 25 t o 30 e i g h t y c h a r a c t e r

lines (Cakir e t a l , , 1979; Stewart, 1979; Hart, l W 6 ) ,

The backgsouad c o l o r o f t h e display ,%reen i s d e t e r m i n e d b y

t h e e m i s s i o n c h a r a c t e r i s t i c s of the phosphor w i t h which t h e

i n n e r s u r f a c e of the s c r e e n i s c o a t e d . Color a f f o r d s a c o n t r a s t

component w h i c h i n c r e a s e s t h e d i s t i n c k i o n of t h e c h a r a c t e r s

a g a i n s t t h e f e f l e c t i o n on t h e g l a s s p l a t e . S i n c e r e t i n a l

s e n s i t i v i t y i s g r e a t e s t f o r wave leng ths from t h e middle part of

t h e spectruna f555 nm), y e l l c w f g r e e n c h a r a c t e r s on a d a r k e r

background are favored [Dirnbaus , 1978) . A b l a c k i v h i t e

contbinat i o n is sonet i l t l es p r e f e r r e d a s i t e n s u r e s good l e g i b i l i t y

and c o n t r a s t w i t h less s t r a i n on the e y e due t o glare. C t h e f

c o l o r c o m b i n a t i o n s w h i c h have been used i n c l u d e bf ue/greg ,

green{tfack aii9 rlranyejd~tirer jiiart, i 9 7 6 j -

Dr. Herril l A l l e n has even s u g g e s t e d t h a t t h e t y p i c a l

display of b r i g h t le t ters on a d a r k s c r e e n is h a r ~ f u l , R e v e r s i n g

t h e d i s p l a y t o a n e g a t i v e contrast *is alsu laore n a t u r a l ,

c o a p a r i a g f a v o a a b l g w i t h a t y p e w r i t t e n page on w h i t e papern

($racd P ~ o c e s s i n g @or la , 1976)- V i s u a l acuity was fouad t o b e

fouer w i t h the p o s i t i v e c o n t r a s t of l i g h t c h a r a c t e r s on a da rk

background, t h a n w i t h a e g a t i v e c o n t r a s t [ B e y , Eleyer a n d

Cegourtiois, 1973) . These researcfiers found, h o ~ e v e r , t h a t

s c i n t i l l a t i o n of v i d e o white can i n d u c e o c u l a ~ f a t i g u e o v e r t h e

l o n g run . Yek r e c e n t improvements have r e s u l t e d i n t h e R e s t

German governinent a p p r o v i n g new e g u i p ~ n t s a f e t y fags i n w h i c h

the m a j o r t e r m i a a l d e s i g v r e q u i r e m e n t s i n c l u d e n e g a t i v e images

of d a r k c h a r a c t e r s on a l i g h t b a c k g s o u n d (Pllanuel, 1982) .

Lu a i n a n c e and C o n t r a s t

T h e q u e s t i o n of s c r e e n l u a i n a n c e and t h u s b r i g h t n e s s

c o n t r a s t between t h e c h a r a c t e r s and t h e background must b e

c o n s i d e r e d i n r e l a t i o n t o the o v e r a l l i l l u z i i n a t i o n oT the room

a t t h e t e r t a i n a l s t a t i o n - Gould i n 1968 [as r e p o r t e d i n D a i n o f f ,

1979) p o i n t e d o u t t h a t i n t h e o r y , t o a c h i e v e a c o r n p a s a b l e

c o n t r a s t r a t i o t h a t is f ~ u a d f o r c l e a r l y t y p e d l e t t e r s [1:7) the

measured s c r e e n / l e t t e r c o n t r a s t r a t i o s h o u l d be 30: 1. T h i s is

b e c a u s e t h e face o f t h e s c r e e n reffects a m b i e n t l i g h t b a c k t o

t h e o b s e r v e r ( v e i l i n g g l a r e ) , H c s e v e r Grand j e a n (19 81)) r e p o r t e d

t h a t c c a t r a s t r a t i o s found v a r i e d E r o ~ 2: 1 t o 30: 1, the a e d i a a

-- 'I .. vaiue being 9; i , iu'eclil- r ivt la i a c u i t y i n l o r contrast c o n d i t i o n s

c a u s e s o c u l a r f a t i g a e when r e a d i n g screens,

The a v e r a g e b r i g h t n e s s i n t h e t o t a l v i s u a l . field d e t e r m i n e s

t h e level o f r e t i n a l a d a p t a t i o n a n d gust t h u s be oaatched t o t h e

b r i g h t n e s s of the s u r r o u n d i n g v i s u a l objects, Po a v o i d

d i s t u r b i n g coatras t c h a n g e s i n t h e p e r i p h e r a l v i s i o n of the

o p e r a t of, t h e r e c o m e n d e d r a t i o f jekveen s c r e e n b r i g h t n e s s t o

t h a t o f t h e s u r r o u n d i n g s s h o u l d be 3:3 for areas i m m e d i a t e l y

s u r r o u n d i n g t h e BDT ( n e a r f i e l d ) and 1: 1 f o r o t h e r areas l f a f

f i e l d , Da inof •’ , 1985)a). P i e 1 d t r i a l s h a v e r e v e a l e d lnuch h i g h e r

l u ~ i n a n c e r a t i o s , Pcz e x a a p l e L a u t r l i e t al. (1980) a p o n

m e a s u r i n g 162 YDT w o r k p l a c e s f o u n d t h a t c o a t r a s t ra t ios o f

scfeen b a c k g r o u n d t o s o u r c e dscunent (neaf field conditions)

were i n t h e o r d e r o f 1:25 w h e r e a s a v e r a g e v a l u e s of 1 ~ 3 0 0 were

o b s e r v e d for screen b a c k g r o u n d t o window ( f a r f i e l d ) r a t i o s .

S i y n i f i c a n t co r re la i im c o e f f i c i e n t s i n t h e o r d e r of 0.25 were

found b e t w e e n t h e c o n t r a s t r a t i o s a n d e y e i 9 t ~ a i r n s - e n t s . X a u b l i e t

a l , (1901) f o u n d h i g h l u a i n a n c e c o n t r a s t s b e t w e e n screen, source

docullrent and t h e s u r r o u n d i n g s p a c e t o b e a s s o c i a t ~ d w i t h a n

i n c r e a s e i n e y e prohlers, T h e y c o n c l u i i e d t h a t h i g h c o n t r a s t ,

e s p e c i a l l y b e t w e e n t h e s o u r c e docuraent and the s c r e e n , can

c o n t r i b n t e t o l o n g l a s t i n g o c u l a r symptoms,

S t a b i l i t y

D i s p l a y i n s t a b i l i t y d i s t r a c t s and f a t i g u e s t h e viewer. I n

s"@e t'ET'&, interlaced scan l i n e s are n s e d to i ~ p r o v e s m a l l

matrix characters b y f i l l i n g i n a d o t where two d o t s meet

d i a g o n a l l y . If t h e refresh ra te is 50 Hz, t h e n e a c h i n t e r l a c e d

f i e l d u i l l be reireshed a t 25 Hz w i t h a d j a c e n t s can l i n e s

r e f r e s h e d alternately, A d i s t n r b i n g " j i t t e r i n g " f effect nay

result . Plains i n t e r f e r e n c e i a t h e D,C, s u p p l y c i r c u i t r y Bay

c a u s e nilrift". T h i s is r e d u c e d by c a r e f u l ~ o s i t i o n i a g o f t h e

c o m p n e n t s . Bore s g c r a d i c types o f i m a g e i n s t a b i l i t y c a n a l s o

o c c u r a s t h e r ~ s u l t o f s h o r t term s u r g e s of power i n a n

u n s t a b i l i z e d power s u p p l y .

T h e nsual. t y p e of i n s t a b i l i t y e n c o u n t e r e d is m f l i c k e r 8 t due

t o the decay o f t h e p h o s p h o r e s c e n t i m a g e b e f o r e i t is r e f r e s h e d

by t h e e l e c t r o n s c a n . While increasing t he p e r s i s t a n c e of the

~ h c s ~ h c r c o u l d o v e r c o m e flicker, probkms w i t h t u b e l i f e , b u r n

r e s i s t a n c e and smear c o o l d EBerge, The r e f r e s h rate is c u r r e n t l y

f i x e d a t between 50 a n d 60 Rz d u e t o bandwid th a n d o t h e r

t e c b a i c a l c o n s t r a i n t s .

I n genera l , t h e b r i g h t e r , t h e more dense a n d the l a r g e r t h e

d i s p l a y , t h e s o r e n o t i c e a b l e is t h e f l i c k e r . @it& i n c r e a s i n g a g e

t h e a b i l i t y t o d e t ~ c t r a p i d l y f l i c k e r i n g o b j e c t s d i s i n i s h e s

( C a k i r e t al. , 1979). S u b j e c t i v e d i s c c n f o r t t o f l i c k e r is q u i t e

v a r i a b l e , Ostberg (1977) found t h a t of a g r o u p of p r o o f r e a d e r s

u s i n g V D T s , 4 0 % f o u n d ~ e g e n e f a t i o n rates less t h a n 60 Hz

u n c c n f a r t a b l e . R e s u l t s f roe a q u e s t i o n n a i r e a s r e p o r t e d by

S t a m r a e r j o h n e t a l , (1981) show t h a t 68% o f t h e VDT o p e r a t o r s

c o a n p l a i n e d a b o u t f ficker w i t h 26% o f the@ i n d i c a t i n g t h a t i t was

"of ten bo t h e r ~ o a t e * ~ , C a k i r e t a 1. (1 979) f o u n d s i g n i t i c a n t

c o r r e f a t i c n s of p e r c e i v e d f l i c k e r w i t h c h a r a c t e r

r e c o g n i z a b i l i t y , eye s t r a i n , h e a d a c h e and f a t i g u e . Laub f i e t a l .

/ 1981) f o u n d i n c r e a s e d o s c i l l a t i n g l u m i n a n c e of s c r e e n

c h a r a c t e r s t o b e a s s o c i a t e d w i t h l o n e r visual a c u i t y and a

b i g h e r i n c i d e n c e of s u b j e c t i v e ~ y ~ p t o m s of eye i r r i t a t i o n

i n c l u d i n g a o r e f r equen t u s e of eye d r o p s f o r refief of sore

eyes.

E s s e n t i a l l y , u s e o f a s h o s t os m ~ d i u ~ ~ e r s i s t e n c e ~ h o s p h o r

a n d ~ e l i a n c e o n a h i g h e r s e f r e s h rate of the o r d e r o f 50 t o 60

Hz a l l e v i a t e s the p r o b l e m s cf f l i c k e r [ C a k i r et al. , 1979;.

Gra'ftd-jean, 1980 ) . As an a l t e r n a t i v e a West German fir@ h a s

d e v e l o p e d a f l a t 2 l / 4 i n c h t h i c k d i s ~ l a y ~ The s h o r t e l e c t r o n

a c c e l e r a t i o n d i s t a n c e , t h e a b s e n c e of d e f l e c t i o n s y s t e m s a n d the

h i g h ~ i c t u r e - r e p e t i t i o n rate of 80 Hz r e s u l t in a no-jitter

f 1 i c k e s - f r e e display (f lanuel , 1982) .

A n o t h e r p r o b l e ~ of p l a c i n g a BDT i n a modern o f f i c e r e s u l t s

from u n s u i t a b l e l i g h t i n g c o n d i t i o n s s u c h a s large b r i g h t

windows, h i g h l e v e l o f i l l u m i n a t i o n a n d w h i t e or p a s t e l painted

g a l l s and c e i l i n g s .

"What is good l i g h t i n g d e s i g n fo r a clerical p a p e r - h a n d l i n g task is n o t n e c e s s a r i l y good for a clerical CRT-viewing task and Bay a c t u a l l y be b a d n { O s t b e r g , 1975) .

A c c o r d i n g t o Ostbery (1978) g l a r e [ r e f l e c t e d 1 i g h t n o t

i i i s d d i i ~ pfo~esse3j is a major source oE di s trac t ion a n d

d i s c o m f o r t t o VDT o p e r a t o r s . The d i f f u s e r e f l e c t i o n of the

s c r e e n surface may be as high as 22% t o 27% a n d w i t h t h e s m o o t h

g l d s s o u t e r s u r f a c e a i r e c t l y r e f l e c t i n g a b o u t 4% of t h e l i g h t

uhich f a l l s o n it, t h e i m a g e of the o p e f a t a r is u s u a l l y clearly

v i s i b l e o n t h e screen* T h i s r e d u c t i o n i n c o n t r a s t b e t w e e n t h e

c h a r a c t e r s a n d ttxe b a c k g r o u n d r e d u c e s l e g i b i l i t y { S t e w a r t ,

1 9 7 9 ) -

R e f l e c t e d l i g h t f r o m uindows, f l o o r s , work s u r f a c e s a n d t h e

keyboard may ar ise when the d i s ~ l a y units are set a b o v e a n d a t

a n a n g l e t o t h e f l a t work s u s f a c e . A c c a r d i n y t o O s t b e r g (1975)

a n d B u s c h 13976) many VDTs a r e used i n o f f i c e s w i t h a n e f f e c t i v e

g l a r e index o f 24 rather t h a n the a c c e p t a b l e l e v e l of 16. T h i s

r e s u l t s i n 50% o f t h e o p e r a t o r s e x p e r i e n c i n g d i s c o a f o r t , With

a d v a n c i n g age, s e n s i t i v i t y t o g l a r e i n c r e a s e s [ C a k i r et al.,

1939 ) - S t a ~ n t e r j o h n et a l . f 1981) found t h a t g l a r e s o u r c e s were

o b s e r v e d i n 87% o f t h e 22 weasured work stations and on 77% of

t h e t e r a i n a l s r e f l e c t e d glare was s o h igh t h a t r e a d i n g was

d i f f i c u l t ,

IB order t o a v o i d vindow r e f l e c t i o n on t h e VDT s c r e e n , one

p o s s i b i f i t y is t o p o s i t i o n t h e hack of t h e VDT t o w a r d s t h e

window. However, t h i s r e s u l t s i n c o n t r a s t g l a r e , R u l t g r e n and

Riiave (1974) fuuud ext re l t l e ly h i g h c o n t r a s t s i n luaa inances of u p

t o l : • ˜ i )D b e t w e e n t h e screen a n d t h e u i n d o p background. # i t b a

t a c k g r o u n d of wal ls and f u r n i t u r e , l u ~ i n a n c e ratios r a n g e d f o r

1:3 to 1:2tC, Accord ing t c t h e s e r e s e a r c h e r s a r a t i o of d:10

b~tween the f i x a t i o n p o i n t of t h e v i s u a l f i e l d a n d its p e r i p h e r y

is r~cc@mended,

T h e U.3, I l f u r t t i n a t i n g Engineering S o c i e t y recomrrtends a n

i l l u ~ i a a t i o n l e v e l o f 1000 l u x for l a r g e o f f i c e s .

Recoamenda t ions of ar t i 2 i c i a l i l l u ~ i a a t i o n for VDT workpfaces

range f rom 100 f n x t o 1600 l u x [ S t a m ~ t e r j o h n et al, 1981) . The

r a t i c n a l e Tor t h e l o w e r v a l u e is t h a t r e f l e c t i o n s on t h e s c r e e n

c a n be a v o i d e d . However mos t s u g g e s t i o n s concur w i t h t h e

a s s e r t i o n t h a t i t f i e l d s t u d i e s h a v e a l s o r e p e a t e d l y shown t h a t

VDT o p e r a t o r s , where it is ~ o s s i b f e f o r t h e @ t o do s o , t a r n down

the l i g h t i n g t o l e v e l s c o r r e s p o n d i n g t o t h e f a n g e 300 t o 500

Lux" [ C a k i r e t al,,1979), Yet e v e n a t t h i s reduced i l l u s i n a t i o n

l e v e l , G u n n a r s o n a n d O s t b e r g 113377) f o u n d i n their field

i n v e s t i g a t i o n s t h a t t h e l i g h t i n g was r e ~ o r t e d t o be s t r o n g . ~t

the w o r k p l a c e s where ceiling i l l u m i n a t i o n was c o n s i d e r e d t o b e

s a t i s f a c t o r y , l i g h t intensities b e t w e e n 350 a n d 300 l u x were

measured on t h e w o t k i n g s u r f a c e s .

S t a m r a e r j o h n e t af. (1981) upon s u r v e y i n g t h e i l l u m i n a t i o n

l e v e l s o f 22 VDT w o r k s t a t i o n s i n the U. S, f o u n d t h a t o n l y 17%

f e f l w i t h i n t h e 300--500 Pax r a n g e . S e v e a t y - f i v e p e r c e n t of t h e

o b s e r v e d s i tes f e l l w i t h i a t h e 500-700 l u x r a n g e w h i l e 1041, were

o b s e r v e d t o be g r e a t e r t h a n 1000 l u x . In contrast C o e e-t a l ,

(1980) i n Edew Zealand found that t h e @a josity (6 3%) of t h e B D T

w o r k p l a c e s s u r v e y e a , s h o v e d i l l u m i n a t i o n l e v e l s b e t w e e n 250 and

5130 lux , 31% were lcwer than 250 l u x and o n l y 70% were h i g h e r

t h a n 500 lux. D a i n o f f et a1. (7984) f o u n d 37% of t h e BDT

o p e r a t o r s s u r v e y e d c o m p l a i n e d of l i g h t i n g . C c a ~ l a i n t s of v i s u a l

f a t i g u e a n d l i g h t i n g wese p c s i t i v e l y c o r r e l a t e d w i t h the a m o u n t

o f t ine spent l o o k i n g a t t h e VDB, Snnitft et al, (1982) a l so found

t h a t VDP n s e r s Bore often f o u n d t h e main lighting t c be too

b r i g h t a n d t o cause g l a r e .

A nuaber of s u g g e s t ions have b e e n o f f e r e d as m a n s of

a v o i d i n g glare . Dp t i m a l l y , light s o u r c e s s h o u l d b e i n s t a l l e d i n

a d i r e c t i o a w h i c h is p a r a l l e l t o the w o r k s t a t i o n while c o n c e a l e d

f i g h t i n g r e f l e c t i n g f rcra u p p r val ls is p r o b a b l y best (ASTB S ,

1 9 7 9 ) , Ambient i l l u n t i r n a t i o n of VDTwworLs ta t ions s h o u l d n o t

exceed 300 l u x , w h i l e l o c a l d e s k i l l u ~ i n a t i e n s h c u l d be n o more

t h a n 500 l u x l D e s k l a ~ ~ s should be fitted with dimmer s w i t c h e s

t o a d j u s t the ambient fuminance t o t h e m a n u s c r i p t , S u r r o u n d i n g

e q u i p m n t and f u f a i t u r e s h o u l d have a a t t e s u r f a c e s o r be d a r k o r

muted t o a v o i d r e f l e c t i o n f rom t h e s e s o u r c e s , R e y t o p s a r e o n e

o b v i o u s s o u r c e s of r e f l e c t i c n s which may h e r ~ d u c e d w i t h a m a t t e

f i n i s h . C a k i s 41978) found t h a t o n e - t h i r d more p e o p l e felt

s t e a i n and 50% Bore had h e a d a c h e s i f t h e y o p e r a t e d a keyboard

v i t h s h i n y t o p s compared t o t h o s e using B a t t e keys. Windows

s h o u l d be f i t t e d w i t h a d j u s t a k f e b l i n d s or c u r t a i n s . S t e w a r t

(198 1) s u r v e y e d 34 d i f f e r e n t workp lace e n v i r c n l a e n t s and found

g l a r e s o u r c e s s u c h as l i g h t s a n d windows i n t h e o p e r a t o r s f i e l d

of v i s i o n i n 66% of t h e cases. Only i n 65% of t h e c a s e s were t h e

w i n d o w s f i t t e d v i k h i n t e r n a l blinds. T h e need t o modify l i g h t i n g

was recoaimetnded in 30% of t h e c3instances,

S c r e e n r e f l e c t i o n s a y be reduced b y means of a f i l t e r , b u t

u s u a l l y a t t h e e x p e n s e of r e s o l u t i o n a n d i m g e b r i g h t n e s s , T h e

GRT t u b e u s u a l l y h a s a n e u t r a l d e n s i t y f i l t e r b u i l t i n t o its

i a c e ~ l a t e , Though i t u n i f o r m l y r e d u c e s t h e amount o f l i g h t

p a s s i n g t h r o u g h a n d so r e d u c e s i n t e r n a l r e f l e c t i o n s , t h e i a a g e

b r i g h t n e s s is reduced, The d i f f u s i n g snrface rartthud i n v o l ~ e s

e t c h i n g , c c a t i n g o r r o u g h e n i n g t h e s u r f a c e i n o r d e r t o b r e a k u &

t h e r e f l e c t e d image, However, d e g r a d a t i o n of t h e s c r e e n iwage o r

a a a s k i a g i f l u a i n a t i o n uh ich itself causes g l a r e c o u l d a p p e a r ,

S p e c i a l t h i n - f i l ~ o p t i c a l c o a t i n g s B a y be vacuura-deposited oat

g l a s s t o a l t e r t h e p h y s i c s of t h e a i r l g l a s s i n t e r f a c e s o t h a t

less l i g h t is r e f l e c k e d . Crane (1979, cited i n D a i n o f f , 1980b)

conipared e l e v e n o p e r a t o r s %hose s c r e e n c o n t a i n e d a m t t e s u r f a c e

a n t i - g l a c e c o a t i n g , and twenty o ~ e r a t o r s % h o s e s c r e e n s had n o

c o a t i n g s . L e v e l s o f complaints ufre l o u e r f o r t h e o ~ e r a t o r s u i t h

c o a t e d s c r e e n s ; 45X c o s p l a i n e d a b o u t glare a n d lighting a n d 36

of eyestrain; this c o m p a r e s t o f i g u r e s of 80% and 60% f o u n d f o r

t h e clear g l a s s g r o u p ,

T h e o c c u r r e n c e of o c u l a r s y ~ ~ t o i ~ s w h i l e w o r k i n g vi t h BDTs

c a n n o t n e c e s s a r i l y b e a t t r i b u t e d c o ~ p l e tel y t o environments 1

s o u r c e s . P e r s o n a l s o u r c e s may be involved. These i n c l u d e such

g e n e r a l s y s t e m i c f a c t o r s as f a t i g u e , s u b n o r a a l h e a l t h a n d the

use of a f c o h o l a n d d r u g s ( P e r g u s o n e t a l . 1974 a s cited i n

Caiacff , 1 9 7 9 ) - I t i s e s t i ~ a t e d that u p t o one-third of the

e a g l o y e e p o p u l a t i o n h a v e u n c o r r ~ c t e d or i n s u f f i c i e n t l y c o r r e c t e d

visual d e f e c t s w h i c b a f f e c t b o t h visual and g e n e r a l c o a f o r t

(Colcver and Wsrr, 7979 ) - R e s i d u a l nncorlcect led r e f r a c t i v e errors

c a u s e d b y t h e use of i n a p p r o p r i a t e e y e g l a s s e s may c a u s e eye

p r o h l e ~ s . I n p a r t i c u l a r , b y p e r m t r o p i c i n d i v i d u a l s r e q u i r e

g r e a t e r t h a n n o r m 1 a c c o m m o d a t i v e e f f o r t f o r close work, p u t t i n g

e x c e s s i v e s t r a i n o n t h e c i l i a r y m u s c l e s , Abont h a l f the g e n e r a l

p o p u l a t i o n are e s t i m a t e d t o be a f f l i c t e d w i t h h y p e r a e t r o p i a

[Dainof f , 1979) , f i e t e r o p h o f i a is a r a u s c u l a r c o n d i t i o n i n g h i c h

there is a l a t e n t t e n d e n c y o f t h e eyes t o d e v i a t e f s o ~ t h e i r

%orrect* o r i e n t a t i o n t o m a i n t a i n b i f a v e a l f i x a t i o n , T h i s is a

coxs@oa c o n d i t i o n a n d a o d e r a t e h e t e r o ~ h o r i a i s p r o b a b l y a l s o a

f a c t o r u h i c h Bay accelerate t h e o n s e t of o c u l a r f a t i g u e i n

terraisal o p e r a t o r s , especially when t h e r e ds an e x o p h o r i c

[ d i ' v e r g i n g ) t e n d e n c y { O s t b e r g , 1978) ,

,

A p a r t i c u l a r v i s u a l p r s b l e s a s s o c i a t e d w i t h the ~ r e s b y o p i c

o r d g i n g e y e is a ncrmal p r o c e s s of a g i n g i n which the l e n s

loses its f f e x i b i l i t y thereby reducing its range of f o c u s -

P r e s b y o p i a , o r t h e Beginning o f i t , map w e l l be one o f t h e main

c o n t r i b u t o r s to visual s t r e s s o A i l e d o i n g near work (1. E , P I . ,

1978) e s p e c i a l l y in those g r e a t e r t h a n 40 pears o f age. Between

t h e a g e s o f 20 to 60 y e a r s o f age t h e a m p l i t u d e of accommodat ion

is r e d u c e d froln about +10 tc +12 f). t o 0 t o 0.5 Do Accoamoda t ive

f a t i g u e is o f t e n e n c o u n t e r e d i n t h e 35-45 age g r o u p , s i n c e t h e s e

s u b j e c t s m y not y e t wear g l a s s e s [Bey, @ e y e r and Degoumois,

l 9 7 7 ) , T h e n e a r p o i n t of accomtacda t ion r e c e d e s f r o m a b o u t 10 cm

[+ID 8 , ) to 2013 cm f+S D,) i n t h e course of a n o r m a l w o r k i n g

l i f e t i m e [Hart, 1976). T h e p r e s b y o p i c p e r s o n poses a s p e c i a l

proiilea of o p t i c a l c o r r e c t i c n , Good v i s i o n a t t h r e e d i s t a n c e s - the screen, a a n u s c r i p t and keyboard - i s needed. While reading

glasses, b i f o c a l s o r t r i f o c a l s nay b e p r e s c s i b e d they are not

a l w a y s adequate, Abnorneaf ~ o s t u r e i n v o f v i n g v e r y r i g i d

p o s i t i o n i n g o f t h e h e a d aay o c c n r - Frequent reading o f u p p e r

f i n e s of the display screen through t h e lower: p r t of b i f o c a l

s p e c t a c l e s m y s e s u l t i n aeck and s h o u l d e r r auscu la f p a i n

a s s o c i a t e d u i t h t h e c e r v i c a l . s y n d r o ~ e ( e , go Johnson a n d Wolfe,

1972 a s cited h y O s t b e r g , 19783,

Barf (79811 quctes Reading 11979) a n d Grundy a n d Roseatha1

11980) a s putting g r e a t esphas is cn t h e presence of **zrisnal

d e f i c i e n c i e s " i n workefs b e f o r e o p r a t i n g ' Y D l s . They m a i n t a i n e d

t h a t only t h e u n h e a l t h y cl: u n c o r r e c t e d e y e e x h i b i t s symgtcms of

ocular d i s c o a f o r t , t h u s they emphasized p r e - s c r e e n i n g , Yet

L a u b f i et al, l'f981) f o u n d t h a t work a t Y D I s c a u s e d o c u l a r

s y m g t o a s i n o p e r a t o r s b o t h w i t h o r w i t h o u t eye d e f e c t s . T h e y

were not a b l e t o p r e d i c t whc w o u l d e x p e r i e n c e s u c h sy f sp toms b y

t h e u s u a l s c r e e n i n g tests, HacKay t1982) p r e s e n t s G i l b e r t s s

i n t e r i a r e p o r t i n w h i c h t e s t s o n u n a i d e d v i s i o n , v i s u a l

r e s o l u t i o n ( a c u i t y ) , s p h e r i c a l a n d c y l i n d r i c a l r e f r a c t i o n s a n d

t h e a r a p l i t u d e of a c c o m m o d a t i o n were assessed o n BDT u s e r s and

n o n - u s e r s , Over t w o pears l a k e r , "very l i t t l e change" had t a k e n

place i n € i t h e r t h e test or c c n t r o l g r o u p s . However i t was

ad mi t t ed t h a t t h e VDTs were used f o r only r e l a t i v e l y s h o r t

p e r i o d s ,

A s e c c n d aa jor p o t e n t i a l s o u r c e of f a t i g u e i s d u e t o the

awkward p o s t u r e s a n o ~ e r a t o r may be f o r c e d t o a d o p t b e c a u s e of

i n a d e q u a t e workstat i o n design, A p r e v i o n s l y a c c e p t a b l e w o r k p l a c e

rPay g r o v e u n c o r a f ~ r t a t ? l e u p o n t h e i a s t a l h t i o s of a VDT. T h e

h e a v y and b u l k y Y D T u n i t i s r e s i s t a n t t o r r t a n i p u l a t i u n ; a s a

r e s u l t , i n d i v i d u a l o p e r a t o r s m y c o a p r o m i s e t h e i r own ccaifort i n

c r d e r t o view t h e s c r e e n c l e a r l y .

N u a e r o u s s t u d i e s g i v e e v i d e n c e t h a t l s u s c u l o s k e l e t a l

discomtort is a c o z m o a e x p e r i e n c e of t h e m a j o r i t y of VDT

o p e r a t o r s . For i n s t a n c e , Guana r s son a n d Ostberg (1977) r e p o r t e d

tha'a: 65% o f m o s t l y young t e r a i i n a l o p e r a t o r s c c a p l a i n e d of some

s o r t of auscular d i s c c m f o r l ; of these, 19% indicated t h a t t h e

d i s c o i a f o r t was s e v e r e . T h e l o c a t i o n of t h e m u s c u l a r aches

i n e l uded t h e shoulders (54%), t h e lower back (328) , t h e l e g s

(2Q$), t h e n e c k (183) a n d t h e h e a d , arms a n d h a n d s (641) .

C a k i r i 1978 ) r e p o r t e d t h a t 60% of t h e i r YDT u p e r a t o r s h a d

back pains while 5 1% e x p e r i e n c ~ d n e c k pains. Grieco et a l ,

f1980) a l s o found t h a t Bore t h a n 50% of VDT u s e r s compla ined of

a c h i n g necks a n d backache d u r i n g and a t t h e end of t h e i r shift,

Tenderness and p a r e s t i h e s i a s of t h e legs were also r e p o r t e d . T h e

h i g h e r i n c i d e n c e o f back and neck pains shown i n t h e s e t w o

s t u d i e s a s coapared t o G u n n a r s s o n a n d O s t b e r g s s 11977) s t u d y

may, i n p a r t , he a t t r i b u t e d t o possible w o r k s t a t i o n d e s i g n

d i f f e r e n c e s . Carfscn (1975, as c i t e d i n D a i n o f f , 1979) c o n d u c t e d

e l e c t r o m y o g r a p h i c s t u d i e s of n e u r a l a c t i v i t y i n ~ u s c l e fibres

w h i c h i n d i c a t e d t h a t t h e cause of u p p e r back f a i n l a y i n t h e

w o r k i n g postures deaanded b y t h e v i s u a l and w t o r i n t e r a c t i o n s

H u n t i n g e t a l . E1980) ~ r o v i d e d soae controls a n d showed

t h a t w h i l e a l l t y p e s of o f f ice workers c o m p l a i n e d of almost

d a i l y l izuscular p a i n s , the h i g h e s t p e r c e n t a g e w i t h s e r i o u s

i m ~ a i r r a l j n t s were t h a s f o p e r a t i n g d a t a - e n t r y VDTs i l h i l e . the

lowest f i g u r e s uere found among t h o s e occuppied w i t h t r a d i t i o n a l

office work. A t f i r s t , s t a t i c efforts Bay ~ r o d u c e p a i n f u l

l o c a l i z e d f a t i g n e i n t h e auscles c o n c e r n e d . These p r o b l eas a r e

a c u t e a n d r e v e r s i b l e . However, a c c o r d i n g t'o H u n t i n g ef: al.

(IQBO), if t h e s t a t i c l o a d a s s o c i a t e d w i t h h i g h work - speed i n

f i n g e r s a n d h a n d s is r e p e a t e d d a i l y o v e r a l o n g p e r i o d of tirw,

mare o r less peci r tanent aches w i l l a p p e a r w i t h p o s s i b l e damage t o

t h e t e n d o n s a n d j o i n t s .

Two characterist ics o f t h e VET i n p a s i c u l a r c a u s e p o s t u r a l

p r o b l e n s f o r many o p e r a t o r s , T h e y a x e t h e f i x e d s i ze of t h e u n i t

used b y o p e r a t o r s of v a r i o u s sizes, p l u s the lack o f a docuraen t

h o l d e r . T h e f i x e d s i z e of t h e u n i t , e s p e c i a l l y when t h e k e y b o a r d is

a t t a c h e d t o t h e s c r e e n , c a u s e s many p r o b l e m s f o r the

" n c n - s t a n d a r d s 3 s i z ~ d o p e r a t o r s , T h e optinturn h e i g h t for t h e

s c r e e n is s u c h t h a t t h e line of sight of t h e ~ p e r a t a r i s a b o u t

35 t o Y O d e g r e e s below t h e h o r i z o n t a l . The o p t i ~ u a h e i g h t of a

k e y t o a r d is s u c h t h a t t h e fcrearms are a p p r o x i m a t e l y h o r i z o a t a l

( S t e k s a r t , 3979). O b v i o u s l y , as t h e o p t i i s a are d e p e n d e n t o n the

s i z e of t h e o p e r a t o r , many o p e r a t o r s w i l l e n c o u n t e r d i f f i c u l t i e s

e i t h e r i n keying or v i e w i n g c o m f o r t , Due t o its p s i t i o n the

k e y b o a r d v i e w i n g a n g l e c a n neoes be o p t i m a l , The p o t e n t i a l neck

a n d t a c k s t r a i n r e k e s i t a n e c e s s i t y to touch type w h e n e v e r

p o s s i b l e , O s t b e r g f1975, a s c i t e d i n Dair~off , 2979)

p h c t o g r a p h i c a l 3 . p surveyed t p i c a 1 BDT operator working p o s t u r e s ,

Be observed t h a t t h e ~ o s i t i c n s of arms, neck a n d d i r e c t i o n of

g a z e were a l l t o o h i g h a s a r e s u l t of the keyboard a n d d i s p l a y

s c r e e n being h i g h e r t h a n was a p p r c p r i a t e ,

T h e w o r k i n g l e v e l , d e f i n e d a s t h e d i s t a n c e b e t w e e n the

u n d e r s i d e of t h e t b i g h s a n d t h e p a l m of t h e hand is one of t h e

mcst i n p o r t a n t c h a r a c t e r i s t i c s of working p o s t u r e w h i l e i n t h e

sitting p o s i t i o n , The d e s k t o p , i f s k Eram and k e y b o a r d s h o u l d

k e a s t h i n a s ~ o s s i b f e i n ofden: t o ensure a v o r k i n g level of

between 220 and 250 ma, w h i c h is comfortafife f o r most people- T o

satisfy requirements f a r s u f f i c i e n t knee c l e a r a n c e the k e y b o a r d

h e i g h t s h o u l d b e a b o u t 30 ram, yet they t y p i c a l l y are between 50

and 120 mrit. A s a r e s u l t , C a k i r eit ai. (1979) f a v o r s a p a r t i a l l y

a d justable d e s k t o p which p e r n i t s a d j o s t m e n t of t h e k e y t o a r d a n d

screen h e i g h t , Tables axe now a v a i l a b l e that n o t only s a t i s f y

this r e q u i r e ~ e n t b u t a l s o have ~rovisicns f o r mtating t h e

s c r een cr m o v i n g i t c l o s e r to o r f a r t h e r f rota t h e o p e r a t o r , as

d i f f e r i n g v i s u a l needs d i c t a t e (APC-CLO,CLC, 198 1 ) .

A d j u s t a b l e f o o t rests f o r shorter VDT o p e r a t o r s s h o u l d a l s o

be i n c l u d e d i n t h e workstation. O f 24 d i f f e r e n t t y p e s o f BDT

w o r k p l a c e s s u r v e y e d by Stewart 11901) o n l y i n 8% o f t h e cases

were f o o t r e s t s p s o v i d e d t o i n d i v i d u a l s t h a t n e e d e d t h e m , They

s h o u l d be a d jus table i n b o t h h e i g h t and a n g l e , wide e n o u g h t o

cover t h e entire l e g rooa area and d e s i g n e d t o a l l o w changes i n

f o o t position,

A s e c a n d s o u r c e of gxobless is t h e d o c u ~ e n t h o l d e r - o r

&ore t y p i c a l l y the lack of a d o c u ~ e n t h o l d e r , C a k i r e t al,

(1979) estimated t h a t a b o u t 81) of VDT o p e r a t o r s also work w i t h

h a r d c o p y , P l a c i n g documents o n t h e f l a t desk s u r f a c e a t t h e s i d e

of t h e VOT where t h e y can be e a s i l y h a n d l e d r e s u l t s i a awkward

twisting aad bending i a order t o reduce t h e v i ewing distance,

The p r o v i s i o n of an a d j u s t a b l e l e c t u r n t ype d o c u ~ e n t h o l d e r a t

the'side of the u n i t h e l p s to a l l e v i a t e the ~foblera. I f

c o r r e c t l y p o s i t i o n e d , its use w i l l r e d u c e u n n e c e s s a r y n e c k

s t r a i n . T h e n e c k is t h e n o s t highly s t r e s s e d p a r t of t h e body

a n d more e f f o r t is expended when t h e h e a d i s moved i n t h e

vertical p l a n e t h a n when t h e h e a d is r o t a t e d s i d e t o s i d e , T h u s

t h e h o l d e r s h o u l d a l l c w for p l a c i n g t h e d o c u ~ e n t on t h e same

l e v e l a s t h e d i s p l a y s c r e e n a n d i n c l i n e d a t a b o u t 20 d e g r e e s

away frors t h e v e r t i c a l t o c o a p e n s a t e f o r t h e f o r w a r d t i l t of t h e

head, Not o n l y d o e s t h i s t i l t of t h e d o c u a e n t o p t i a i z e t h e l i n e

o f s i g h t t o b e a t r i g h t a n g l e s t o t h e plaae of t h e pape r , it

a l s c a p p r o x i m a t e l y h a l v e s t h e l u ~ i n a n c e of t h e c o p y . T h i s

r ~ d u c e s t h e c o n t r a s t b e t w e e n t h e d i s p l a y s c r e e n a n d t h e

doc omen t,

The i m p o r t a n c e of h a v i n g a source d o c u m e n t h o l d e r was

i n d i r e c t l y b r o u g h t o u t i n t h e f i e l d s t u d y c o n d u c t e d b y H u n t i n g

e t al, [ 1 9 8 0 j , 9 h e y f o u n d t h e s u r p r i s i n g r e s u l t t h a t t h e

i n c i d e n c e of physical i m p a i r ~ e n t s i n 152 VDT o p e r a t o r s was

l e s s e n e d when w o r k i n g l e v e l s Mere h i g h e r t h a n t h e r e c o m ~ e n d e d

l e v e l s , Hovever , upon o b s e r v a t i o n o f t h e q o r k p f a c e s t h e y f o u n d

t h a t n e a r l y a l l o p e r a t o r s had t h e i r s o u r c e d o c n a e n t s lying o n

t h e d e s k . The researchers c o n c l u d e d t h a t t h e h i g h e r t h e d e s k

l e v e l , the h i g h e r were t h e s o u r c e d o c u m e n t s , t h u s t h e be t t e r t h e

p o s t u r e of h e a d and t r u n k . T h e y sti l l recoearaended t h e l o v e r

w o r k i n g l e v e l s , however, only i f a n a d e q u a t e s u p p o r t f o r t h e

s o u r c e d o c u m e n t s w i t h i n d e p e n d e n t l y a d j u s t e d height is p r o v i d e d .

P o c r p o s t u r e becoeaes an even g r e a t e r ~roblers i f t h e

o p e r a t o r h a s u n c o r r e c t e d v i s u a l d e f e c t s o r wears bifoca 1 l e n s e s .

O n e m a n u f a c t u r e r o f CBT d i s p l a y s f o r offices h a s g o n e s o f a r as

t i a f n i n g a g a i n s t the u s e o f t i f o c a l g l a s s e s d u r i n g l o n g - t e r m YDT

work b e c a u s e p e o p l e with s u c h g l a s s e s t e n d t o a d o p t a f a t i g u i n g

h e a d p o s t u r e which r e q u i r e s e l e v a t e d l e v e l s of s t a t i c m u s c l e

efforts of t h e neck a n d t r u a k ,

4 w e l l - d e s i g n e d c h a i r c a n f a v o r a b l y affect t h e o p e r a t o r * s

p o s t u r e a n d t h e a m u n t of e f f o r t r e q u i r e d t o m a i n t a i n i t , a n d a s

a c c n s e g u e n c e t h e c i r c u l a t i o n and amount of p r e s s u r e on t h e

spine. A good a d j u s t a b l e b a c k r e s t h e l p s a a i n t a i n t h e n a t u r a l

i nward c u r v e o f the l o w e r s ~ i n e a n d Bay t a k e soate body w e i g h t

0g.f t h e s p i n e , Good sitting p o s t u r e w i l l r e s u l t i n even p r e s s u r e

o n the s ~ i n a l discs. The uneven p r e s s u r e r e s u l t i n g frcm p o o r

p o s t u r e , i f maintained too l o n g , say result i n back p r o b l e m

c a u s e d by the d e f o r m a t i o n of t h e d i s c s ( C a k i r et a l , , I?J'?g),

The s h a p e of t h e c h a i r s e a t s h o u l d facilitate f r e g n e n t

changes of p o s i t i o n and , i n c a n b i n a t i o n w i t h seat h e i g h t s h o u l d

~ e r m i t raost o f t h e body w e i g h t to be t r a n s f e r r e d t o t h e s e a t

t h r o u g h the b u t t o c k s , n o t t b e t h i g h s , S e a t h e i g h t s h o u l d b e

a d j u s t a b l e ( f r o m t h e s e a t e d p o s i t i o n ) s o that t h e o p e r a t o r s '

t h i g h s are h o r i z o n t a l a n d t h e f e e t are f l a t on t h e f l o o r , I n

t h i s p o s i t i o n the s t a b i l i s i a g work r e q u i r e d to m a i n t a i n tbe

s i t t i n g p o s i t i o n i s k e p t t o a ~ i n i i a u m a s is t h e s t a t i c stress i n

t h e k a c k a n d l e g ~ u s c l e s , A c h a i r t h a t is too h i g h @ay r e s u l t i n

e x t r a p r e s s u r e o n t h e l o w e r t h i g h s which gay i s p a i r c i r c u l a t i o n

whereas i f i t is t o o low t h e p e l v i s w i l l tend to r o t a t e a n d

p r o ' s c t e a n o u t w a r d c u f v e df t h e lower s p i n e . X f t h e s e a t s u r f a c e

is too hard, p r e s s u r e may become too c o n c e n t r a t e d a n d c a u s e

d i s c c m f o r t and p o s s i b l y h e l a o c r h c i d s due t o t h e p o o l i n g o f b l o o d .

A r e a s o n a b l y firm s e a t w h i c h c o m p r e s s e s a b c u t twc ern is

recorrtmended. I f it is t o o s o f t , extra muscle activity i s

r e q u i r e d t o maintain a g i v e a p o s i t i o n ( I , B . f l , , 39781, S e a t i n g

p o s t u r e i s so i n t p o r t a a t to t h e o p e r a t o r s * c o ~ f o r t and h e a l t h

t h a t i n S c a n d i n a v i a p h y s i o t h e r a p i s t s a r e o E t e n u sed t o train

o p e r a t o r s how to sit a n d adjust t h e i r c h a i r s ,

Whi fe v a r i o u s r o r k p l a c e d e s i g n c o n s i d e r a t i o n s p a r t i c u l a r l y

r e l e v a n t t o VDT use h a v e been recommended, i n p r a c t i c e t h e y arc;

seldom followed. S t e u a r t (1903) susveyed 17 d i f f e r e n t t y p e s of

work~lace d e s i g n s a n d found typical w o r k p l a c e d e s i g n f a u l t s

i n c l u d i n g t h e k e y b o a r d being a o n - d e t a c h a b l e 150% of 10 ~ o d e l s ) , t o o h i g h 167%) a n d vith no ad j u s t a b i l i t y f94X)- I n s u f f i c i e n t leg

r o o @ was e n c o u n t e r e d i n 59% of t h e cases due t o o b s t r u c t i o n s

v a d e r t h e desks or t h e d e s k t o p s being t o o t h i c k , P c o r chair

ad j u s t a e n t was f o u n d i n a l m o s t a l l the cases [951JK) v i t h 27% of

the c h a i r s having a b s o l u t e l y no a d j u s t a b i l i t y , The c h a i r s w i t h

p o o r ad j u s t a b i l i t y vere s e l d o ~ aadjnsted a s t y p i c a l l y i t i n v o l v e d

g e t t i n g off t h e c h a i r a n d e x e r t i n g c o n s i d e r a b l e force o n a

k n u r l e d knob. Stewart (1981) a d d e d tha t i n a l l of the 2 4

d i f f e r e n t t y p e s of w o r k p l a c e s s u r v e y e d i n t h e T J , K . , t h e r e was no

guidance a v a i l a b l e to the i a d i v i d u a l o p e r a t o r s t o h e l p the^ t o

a c h i e v e a n optimal a d j u s t a e n t of t h e c h a i r . Coe ( 3 9 8 0 ) found

t h a t 643 of m a - a d j u s t a b l e seats vere o f i n c o r r e c t height* More

s u r $ r i s i n g l y , 9 9 % of t& seats ia which o n l y height was

a t l j u s t a b l e a n d 71% o f the fully a d j u s t a b l e seats %ere i n c o r r e c t

i n h e i g h t .

E v e n when t h e IODT o w r a t o r i s p r o v i d e d wi th a ~ r o p e r l y

d e s i g n e d w o r k p l a c e , any p o s t u r e b e c o a e s bad when it h a s t o be

f i x e d o x i n a i n t a i n e d for too l c n g a p e r i o d . The freedontr and

ability t o c h a n g e p o s t u r e at f r e q u e n t intervals c o n t r i b u t e s

g r e a t l y towards d e l a y i n g s u b j e c t i v e f e e l i n g s of f a t i g u e . F o r

instance, t h e k e y b o a r d s h o u l d be ~ttoveable so a s t o p e r ~ i t

f r e q u e n t changes of a m , shoulder, and s p i n e p o s i t i o n . H u n t i n g

et al , (1980) o b s e r v e d t h a t d i a l o g u e o p e r a t o r s using moveable

keyboards and t a k i n g advar~taye cf shor t w a i t i n g periods by

resting t h e i r h a n d s o r f o r e a r ~ s on t h e d e s k s o r k e y b o a r d s , had a

lower i n c i d e n c e cf ~rcbk?&tttls l t i t h t h e hands a n d arms, T h e

researchers theref o r e recorninended t h a t a l l VDT workplaces w i t h

k e y b o a r d s s h o n l d a l s o p r o v i d e s p e c i a l f osea rm/haad s u p p o r t s ,

U r i j h t 11982) a d d s t h a t this a l s o reduces o p e r a t o r error, n b i c h

is the ~ r i n c i p a l b a r r i e r to increased p r o d o c t i v i t y. On a Bore

general note S t e w a r t {1979) s u g ~ e s t e d t h a t 8scvement c a n a l s o be

e n c o u r a g e d by a s u i t a b l e task d e s i g n . R h e r e v e r p o s s i b l e , 'VDT u s e

s h o u l d be part o f t h e users jab rather t h a n a l l of i t ,

CoapLaints c o n c e r n i n g general body d i s c o m f o x t as a r e su l t

of YDT ase have a l s o keen v o i c e d .

[I) Skin rashes - D u r i n g 1979 aad I980 d o c t o r s i n Norway

notified t h e D i r e c t o r a t e of Labor I n s p e c t o r a t e o f about 35 cases

of facial . rashes aaong VBT operators [Tjortn, 1980). T h i s

llexanthenaau d e v e l o p e d af ter less t h a n t w o h o u r s of vo fk - up t o

a b o u t f i v e t o s i x h o u r s - and t h e n u s u a l l y disappeared dur ing

the f i r s t few h o u r s a f t e r work. A g r e a t d e a l of s t a t i c

e l e c t r i c i t y was o b s e r v e d i n t h e work a r e a s . T h e r e s e a r c h e r s t h u s

h y p o t h e s i z e d t h a t t h e w i n t e r a i r c o n d i t i o n i n g around t h e B D T s

c o u l d h a v e c r e a t e d s t a t i c electr ic fields which a t t r a c t e d d u s t

t o t h e skin,

{Xi) E p i l e p s y - O f a such @ore ser ious nature is the

p o s s i b i l i t y for susceptible v i c t i n s of VDT-iaduced e p i l e p s y ,

T h i s problelzt i s rare however {BSTffS, 1979) . I n particular, t h i s

problera may surface when i n t e r l a c e d s c a n l i n e s are used to found

out charac te r c o r n e r s , P h i s e f f e c t i v e l y r e d u c e s t h e r e f r e s h rate

f r o g S O Hz t o 2 5 Hz, T w e n t y - f i v e hertz is e x t r e n e l y effective i n

i n d u c i n g a s e i z u r e in p h o t o - s e n s i t i v e epileptic i n d i v i d u a l s .

[IXX) S y s t e ~ i c syregtoms - S y s t e m i c s yaptoerrs of h e a d a c h e a n d

f a t i g u e a x e common1 y found, especially aaong f u l l - t h e BDT

o p e r a t o r s . T h e headaches a r e o f t e n I c c a l i z e d i n t h e f o r e h e a d

a r e a a b o v e t h e eyes and are s o ~ e t i n e s a c c o n p a n i e d by s t a b b i n g

pa ins . Cakir (1978) found that t h e i n c i d e n c e s of headache were

highest i n t h e h i g h i n p u t a c q u i s i t i c n workers (45%) , i n t e r m e d i a t e f o r clerical workers (30%) a n d l o w e s t f o r

programmers, Elelat i v e l y l a r g e s i g n i f i c a n t c o r r e l a t i o n s were

f otind between headache; backache and e y e s t r a i n , T h i s i s not

u n e x p e c t e d a s a f f t h e symptoms are f a t i g u e r e a c t i o n s .

G e n e r a l f a t i g u e is a mcre ~ s y c h o l o g i c a f form of r e a c t i o n t o

stress, T h e s t r e s s - f a t i g u e r e l a t i c n s h i p i s a d d i t i v e . 9hs

s u b j e c t i v e r e a c t i o n s s u c h a s "boredo&, w e a r i n e s s , d e p r e s s i o n ,

l a s s i t u d e , a n g e r and e x h a n s t i o n a l s o c a u s e d i a i n i s h e d s k i l l i n

p e r f o r a i n y t h e tasks r e g u i r e d o f t h e m , , . f a t i g u e d v o r k e r s pay

less a t t e n t i o n , r e c e i v e new visual i n f o r m a t i o n more s l o w l y , need

l o n g e r r e a c t i o n t i a e s and show m r k e d d e c r e a s e s i n m o t i v a t i o n

and ~ e r f ormancejg { B u s c h , 1976) , Repea t ed d a i l y f a t i y u e often

l e a d s t o c h r o n i c f a t i g u e which is c h a r a c t e r i z e d by s n c h c h a n g e s

a s loss of a p p e t i t e , headache, d i z z i n e s s , indigestion, insontnia ,

d e ~ r e s s i o n , i r r i t a b i l i t y , acger and ne rvousnes s ,

L a u b l i e t a l , (1980) found that c u n t i n u o u s work a t VDTs was

a s s o c i a t e d w i t b a h i g h work l ead , v h i c h p r o d u c e s excessive

fatigue i n some o p e r a t o r s . S o ~ e data entry t e r ~ i n a l o p e r a t o r s

r e p o r t e d t h a t f a t i g u e symptoets may n o t only p e r s i s t i n l e i s u r e

t i n e b u t even after s l e e p t h e y do n o t find c o r s p l e t e r e c o v e r y ,

Snrtith et al. f19f31) showed t h a t c l e r i c a l VDT o p e r a t o r s were

s i g n i f i c a n t l y h i g h e r i n t h e f a t i g u e sca le t h a n were p r o f e s s i o n a l

YDT o p e r a t o r s and non-ope ra to r c o n t r o l s ,

[IV) P h y s i c a l S t r e s s o r s - Stress is a c e n t r a l e l e m e n t i n

the VDT h e a l t h problem, Eve ry e r r o r i n the design o f t h e

mich ine , and t h e workp lace job d e s i g n a d d s directly and

i n d i r e c t 1 y to t h e t o t a l stress of t h e job. S i n c e stress

i n c r e a s e s w i t h t h e i n t e r a c t i o n of c o ~ b i n e d effects; a t t c n t i o n

must be p a i d t o s t r e sg however i n s i g n i f i c a n t each may s e e m

i n d i v i d u a l l y {3ergaran, 19881. Stress b e g i n s Even before t h e VDTS

a re i n t r o d u c e d . A u t o m a t i o n of t h e office r e p r e s e n t s t o t h e

o p e r a t o r t h e th rea t o f being r e p l a c e d b y a ~ a c h i n e , An

u n c o m f o r t a b l e work e n v i r o n m e n t , i n c l u d i n g such p h y s i c a l h a z a r d s

a s ncise a n d hea t , r e p e t i t i o u s o r mono tonors t a s k s , i n e d f i c i e n t

m a c h i n e r e s p o n s e a n d work pressure a r e all c o n t r i b u t o r s t o

stress. P o s exar t lp le , D a i n o f f e t al. (1981) founrl. 42% o f t h e VDT

w o r k e r s s u r v e y e d s u f f e r e d fro@ ~ h ~ s i c a f a n d a e n t a l stress,

(1) Noise - V C I k e y b o a r d s are r e l a t i v e l y silent i n

c o a e p a s i s o n t o t y p e w r i t e r s , The c o d i n g f a n w i t h the n n i t m y hum

a n d the h i g h tans i . cn electric circuitry Eaay cause a h i g h p i t c h e d

whine . G l h i l e t h e levels are too law t o cause hearing danrage,

h i g h f r e q u e n c i e s [18,000 t o 20,000 Hz) may b e d i s t r a c t i n g o r

i r r i t a t i n g , especially t o younger geople who are aore s e n s i t i v e

(Turner, 1979). S t a n d i n g wave o r focussing effects raight f u r t h e r

i n c r e a s e sound l e v e l s i f t h e YCT i s i n a corner or alcove

( S c i Q u e s t , 1811, I n a d d i t i o n , e x c e s s i v e background n o i s e can be

produced by other neafky office equ ip i f t en t , s u c h a s t y p e w r i t e r s

and t e l e p h o n e s ,

F o r e x a a p l e , Stewart (1980) surveyed 16 VDT o f f i c e s axid

found t h a t 63% of t h e o p e r a t o r s c o r t l p l a i n e d of t o o much n o i s e

w h i c h o f t e n i n t e f f e r e d v i t h coamunica t i o n or c o n c e n t r a t i o n .

Fatigue a n d e a a t i o n a l stress can lead t o e v e n t u a l h e a r i n g lass*

An acce~ tab l e n o n - s t r e s s level is i n t h e range of 50-70

d e c i h f s . However office t a b u l a t i n g t n a c b i n e s for e x a m p l e h a v e a

d e ' c i k e l l e v e l of e i i j h t y (Love, 1 9 7 8 ) . Grandjean 11978) f o u n d

that 35% of t h e respondents i r nd ica t ed t h a t they were g r e a t l y

d i s t u r b e d by n o i s e i n t h e i r o f f i c e s , However: t h e r e was no

c o r r e l a t i o n between n o i s e i n t e n s i t y and f r e q u e n c y o f c o m p l a i n t s ,

Ra t h e r , d i s t u r k i n g c o n v e r s a t i o n s s e e a e d t o be t h e p r i n c i p a l

c u l ~ r i t .

(2) Heat - 813. V D " S sand related eyujlpment ernit heat, o f t e n

as ~ u c h as @00 Watts f r o n a s i n g l e unit, The t h e r ~ a l o u t p u t of a

number of u n i t s close t o g e t h e r Bay create u n p l e a s a n t hot s p o t s ,

Accord ing t o C a k i r e t a L 11979) air c o n d i t i o n i n g c a l c u l a t i o n s

have shown that t h e t b e r ~ a l l o a d i n g at VDT w o r k s t a t i o n s Bay be

be tween 30 - 150% g r e a t e r than t h e s i t u a t i o n without VDSs, This

s t a t e r a e n t differs d r a n t a t i c a l l y f rora BacArtbur * s (7980) a s s e r t i o n

t h a t * * t h e 100 u or s o froin a t y p i c a l V D U can n o r m a l l y b e handfed

by c o n v e c t i o n , For comparison, a human body a l s o dissipates

a b o u t 100 uw,

T h e t h e r a a l load imposed t h r o u g h t h e ope ra t i on of VDTs is a

p e r v a d i n g ~ s o b l e m , Stewart 11980) surveyed eight; workplaces and

found that 100% of t h e operatoss coaplaiaed of a poor thermal

environ~ent. "The b e a t i n g and v e n t i l a t i o n systems evaluated v e r e

seldom c a ~ a b l e of con trolling the te~pera t u r e , a i r f l o w and

h u m i d i t y to a n a d e q u a t e d e g r e e e v e n when operating p e r f e c t l y

( w h i c h is seidoat the case) ' a . Thus C a k i r et a3.. f1979)

seccmntcnded t h a t t h e c a u s e s ra ther t h a n t h e e f f e c t s of t o o great

a t h e r m a l load be c o n t r o l l e d by u s i n g V D T s with lollr t h e r m a l

e m i s s i o n , d i r e c t i n g t h e heal d i s s i p a t e d by t h e u n i t away from

t h & operator or n e i g h b o r i n g o p e r a t o r s , and by e v e n l y

d i s t r i b u t i n g a n d l i ~ i t i n g t h e number of VDTs i n s t a l l e d i n a room

a s much a s p o s s i b l e .

( 3 ) Wachine P a c i n g - Stress may a l s o a r i se from t h e i n t e n s e

c o n c e n t r a t i o n often r e q u i r e d i n work ing with VDTs. P a r t i c u l a r l y

sZressful is t h e adjunct u s e o f the t e r l a i n a l f o r error d e t e c t i o n

a n d p r o d u c t i o n ~ o n i t o r i n g . Cne of t h e s e v e r e s t r a i n s i n t h e work

e a v i r o n ~ e n t i s sheer i n f o r m a t i o r , load, The degree of

s t r e s s - i n d u c e d fatigue is d i r e c t l y p r o p o r t i o n a l t o the rate of

processing t h e d a t a * The c r u c i a l matter i s t h e lack of relief

p a u s e s . During the c o u r s e of t h e o p e r a t i o n oE d i s p l a y u n i t s

t h e r e are frequent Fauses a s t h e c o a p u t e r searchers for and

r e t r i e v e s material f o r d i s p l a y - R a t h e r than being r e s t f u l , t h e

o p g o s i t e i s t r u e . These d e l a y s act a s stressors b e c a u s e t h e

o p e r a t o r s d o n o t know e x a c t l y when t h e y will o c c u r and how l o n g

t h e p a u s e s w i l l be. W a i t i n g and p r e p a r i n g for t h e c o m p u t e r

r l e s p n s e creat~s Ittore r a t h e x t h a n less f a t i g a e (Warr, f 9 8 l ) .

a n x i e t y is also liable t o occur whenever t h e VDT c l e r k acts

a s t h e i n t e r f a c e between t h e o r g a n i z a t i o n a n d its o u t s i d e

c l i e n t s and d o e s n o t fully unders tand t h e p e c u l i a r i t i e s of t h e

c o m F u t e r s y s t e m { O s t b e r g , 1975) .

B, Evaluat ion af WIT Psoblems by Quest ionnaire

I. Bhe Qaestioanaire Stndy

T o a d d r e s s t h e question of k f i e t h e r t h e VDT p e r se is

responsible for the h e a l t h c o m ~ l a i n t s r e p o r t e d , an a d e q u a t e

e v a l u a t i o n should c o v e r the p h y s i c a l e n v i r o n m e n t a n d t h e

p s y c h o s o c i a f i n f l u e n c e s of the w o r k p l a c e i n a d d i t i o n t o t h e

ergonomics of t b e VDT u n i t itself.

I n c r e a s i n g concern i s b e i n g v o i c e d over t h e harden of

i n d o o r a i r p o l l n t i o n {see S t e r l i n g and K o k a y a s h i , 1977, f o r

exarrrple) . B o s t of f i ces t o d a ~ u s e m e c h a n i c a l v e n t i l a t i o n systems.

These a i r - c o n d i t i o n i n g s y s t e ~ s o f t e n p i c k up w h a t e v e r is b e i n g

emitted i n t o the air and c o n t i n u o u s l y recycle it* T h u s workers

are c o n s t a n t l y exposed t o t o b a c c o sraoke, dusts and fumes ( l o v e ,

197E), Grieco e t a f . (1980) for i n s t a n c e fouad a s o u r c e o f

c o ~ p l a i n t s t o b e t be a i r - c c n d i t i o n i a g s y s t a . VDT opera t o r s

con~lained of "stagnating air and t h e presence of o d o r s " ,

P o t e n t i a l c h e i n i c a l e x g o s u r e s include a m m n i a , w t h a n a l and o z o n e

f r o m copying ~ a c h i n e s , t h e h i g h l y t o x i c s o l v e n t

tr i e h l o r o e t h y l e n e which is c o n t a i n e d i n o p a q u e c o r r e c t i o n f h i d ,

and o t h e r s o l v e n t s i n stencil a a c h i x e s ,

F i e l d i n d u s t r i a l hygiene a e a s u r e r t l e n t s have b e e n c o n d u c t e d

by qr team o f EslOSfi i n v e s t i g a t o r s i n S a n P r a n c i s c o (see H u r r a y e t

a l . , 1 9 8 1 , f o r d e t a i l s ) , T h e a c c u p a t i o n a l s o u r c e s of a i r b o r n e

c h e m i c a l c o n t a m i n a n t s that the r e s e a r c h e r s i d e n t i f i e d were

p h c t o g r a p h i c d a r k r o o l e s , photoccpiers, o t h e r reproduction

e q u i p m e n t a n d s a o k i n g , Tbe c h e m i c a l s on which m e a s u K e m s n t s were

a t t e m p t e d i n c l u d e d h y d r o c a r k o n s , c a r b o n m n o x i d e , acetic a c i d

a n d f o r m a l d e h y d e . Geeeral V C T area h y d r o c a r b o n l e v e l s ranged

from 1,4 to U - 4 ppro. The p e a k levels n e a r soate t e r m i n a l s were a s

h i g h a s 10.5 ppm. C a r b o n inonox ide l e v e l s r a n g e d f rca 1.0 t o 3 - 0

ppm. N e i t h e r acetic acid or fo frna ldebyde were present i n

d e t e c t a b l e q u a n t i t i e s , A l l t h e c h e a i c a l p o l l u t a n t s m e a s u r e d were

b e f a u a n y h a z a c d o u s l e v e l .

Heating a n d v e n t i l a t i o n sys t ec t t s are s e l d o m c a p a b l e of

c o n t r o l l i n g t h e t e m p e r a t u r e , a i rf low and h u m i d i t y t o an a d e q u a t e

d e g r e e . Grand jean 47978) f o u n d t h a t g e n e r a l r r t ea su remen t s of

l a r g e sca le o p e n p l a n of f i ce s were f o u n d t o be within s t a n d a r d

c o n d i t i o n s . Wouever t e ~ p e r a t u s e s g r e a t e r t h a n 24 d e g r e e s

c e n t i g r a d e were j u d g e d a s b e i n g t o o warn. B l ~ o s t 3 3 1 of t h e

w o r k e r s c o ~ p f a i n e d of draZts b u t t h e r e was n o a p p a r e n t

r e l a t i o n s h i p b e t w e e n d e g r e e of a e a s u r e d a i r movement a n a

f r e q u e n c y cf c o i t t p l a i n t s ,

C a k i r e t al. (1979) f o u n d t h a t e x c e s s i v e h e a t was p e r c e i v e d

a s a problem b y 50% of YDT o p e r a t o r s uho w o r k e d i n

n o n - a i r - c a n d i t i o n e d o f f i c e s , a n d b y 3 0 % of o p e r a t o r s who worked

i n a i r - c o n d i t i o n e d cf fices. A h i g h c o r r e f a t i c n {r=0,54) was

f o u n d between c o ~ p l a i n t s of d r a f t s a n d neck pain among those who

worked in a i r - c o n d i t i o n e d o f f ices, With r e g a r d t o r e l a t i v e

h u a i d i t p , two-2hisds o f t h e p a r t i c i ~ a n t s believed t h e a i r i n

t h e i r o f f i ces was tco d r y . However o b j e c t i v e nteasurentents of

x e f a t i v e h u i a i d i t y i n these o f f i c e s v a r i e d i n the 30-70% r a n g e

considered a s comfoztatrle. A c c o r d i n g l y , the authors s u g g e s t e d

t h a t the lower liltfit f a r corafort b e raised t o 50%*

Cae et al. {1980) stated that a r e l a t i v e humidity of over

45% i s recaamended so t h a t drying out of t h e ltfucous membranes of

t h e respiratory trac t a n d conjunctival and c o r n e a l e p i t h e l i a are

a v o i d e a , S t o n e (1981) f o u n d t h a t d e h y d r a t i o n of t h e cornea

o c c u r r e d w i t h h i g h a ~ b i e n t temperatures, low b u s i d i t y and h i g h

a i r wovemefit c a u s i n g drafts , According to Cakir et a l , 31979)

a i r ltforreraents of o n l y 0.01 @/see give r i s e to an unco lx l for tab le

d r a f t for 23% of people p u e s t i c n e d and cause i n some c a s e s

dryness and burning sensations i n t h e e y e s ,

C a k i r et d l , (1979) surveyed eight h u n d r e d VDT operators.

O f t h o s e ~ h o made a large nufttber cf c o m p l a i a t s related to back,

n e c k and headache , 75% worked i n air-conditiofed of •’ices-

L i k e w i s e 74% of those who had h i g h rates of room climate

c u r p l a i n t s rrorked i n a i r - c o n d i t i o n e d of •’ices, The authors

a d v i s e d t h a t due t o the c i r c u l a t i o n of a ir , d r y a i r i s f e l t t o

b e even more d r y , To ensure t h e w o r k e r s * coafort, i t is

n e c e s s a f y to avoid even v e r y s m a l l a i r c u r r e n t s i n t h e room a t

head and neck height. Coe et al. 11980) provided s v ~ ~ o r t i n g

evidence. Only 1 7 % ..of t h e BDT group and 2 5 % of t h e control g r o u p

r e p o r t e d u a c o m f o r t a k l e tentperatures, O f t h o s e who found t h e

e n v i r c n a e n t u n c o a f o r t a l l e 45% of t h e VDT u s e r s c o m g l a i n s d o f

t e m ~ e r a t u r e v a r i a b i l i t y , Hobever t h e y could f i n d no r e l a t i o n s h i p

b e t w e e n dry a i r and t h e p r e s e n c e cf s y n t ~ t o a r s of a s t h e n o p i a .

P s y c h o s o c i a l I n f l u e n c c s

While n a n y studies h a v e concentrated cn t h e e ~ g o n o m i c

a s p e c t o f t h e VDT g r o k l e a c o m p a f a t i v e l y few have r e s e a r c h e d t h e

p s y c h o l o g i c a l stresses involved i n t h e c o m p u t e r i z e d workplace,

Gnnnarson and Cstberg I1 977) q u e r i e d VDT o p e r a t o r s abou t

s t r e s s f u l elements i n t h e i r jobs. A b o u t o n e - t h i r d o f all t h e '

o p e r a t o s s felt t h a t t h e u o r k p a c e h a s too fas t . I n a d e p a r t m e n t

w h e r e o p e r a t o r s had little c o n t r o l aver t h e i r j o b t a s k s , 72%

e e ~ p h i n e i l ij-t" iiioi?oiofiy. ahen a s k ~ r i if t h e i r job was s t s e s s f u i

641 s a i d yes, U a f o r t u a a t e l y , n o c o a t p a r i s o n c o n t r o l g r o u F was

used. For exarapfe, G r a n d j e a n f1979) c i t e s t h e study by C a k i r e t

af. (1978) i n wh ich t h e y f o u n d t h a t t h e f e e l i n g s of stress

e x p r e s s e d b y VD2 o p e r a t o r s d i d n o t d i f f e r i n a a g n i t u d e from

those e x p r e s s e d by o t h e r w o r k e r g r o u p s e x a m i n e d i n p r e v i o u s

studies. However a n o t h e r s e t o f job stress q u e s t i o n n a i r e item

c o r r e l a t i o n s r e v e a l e d t h a t t h e a a o u n t of t i iw spent working a t

t h e VDT %as c o r r e l a t e d v i t h b o r e d o a , f a t i g u e , a o n o t o n y and

p e r c e i v e d j o b s a t i s f a c t i o n . On t h e o t h e r h a n d , Coe et al, (3'380)

f o u n d n o d i f f e r e n c e s b e t w e e n VDT a n d c o n t r o l w o r k e r s v i t h

r e s p e c t t o q u e s t i o n s c c n c e f n i n y job stress, S a u t e r et a l . (1983)

38

shoared a s t r o n g i n d i c a t i o n of i n c r e a s e d stress f o r t h e VDT

users.

T h e study by C a k i r et al. f 1979) s h o u e d t h a t BDT o p e r a t o r s

working on a p i e c e - r a t e pay s y s t e e h a d p u r e r scores i n

s o c i a b i l i t y , fraiw of mind, and s t a t e of stress, f a t i g u e and

i n n e r s e c u r i t y rhen ccspared w i t h h o u r l y p a i d VDT workers, After

work, bc-th g r o u p s s h o w e d s i g n i f i c a n t l y h i g h e r l e v e l s o f stress

a n d sleepiness and lower levels of well-being, p o s i t i v e frarae of

mind , s e l f - c o n f i d e n c e , soc ia l a w a r e n e s s , s o c i a b i l i t y a n d

w i l l i n g n e s s t o u n d e r t a k e f u r t h e r a c t i v i t y t h a n t h e y d i d b e f o r e

w o r k , Of c l e r i ca l VDT o p e r a t o r s uho had been reduced i n s t a t u s

t o copy t y p i n g , 85% f e l t t h e i r j o b was a o n o t o n o u s while 90%

f o u n d i t e x t r e a e l y f a t i g u i n g ,

P s y c h o f o g i c a l r e a c t i o n s to VDTs will d e p e n d on the t y p e of

work, t h e way the new -job i s o r g a n i z e d a n d i n t r o d u c e d and o n

p e r s o n a l a t t i t ndes [Grand jears, 1980) . f n g e n e r a l ,

c o ~ ~ u t e r i z a t i o n h a s raade t h e o p e r a t o r t a s k s h i g h l y s p e c i a l i z e d

a n d r o u t i n e , A c c o r d i n g t o Ostbery (1975) clerical c o m p u t e r

t e r m i n a l o p e r a t o r s a r e someti~es more a l i e n a t e d t h a n s h o p - f l o o r

a s s e a n b l y line ~orkers . S i r a p l e, r e p e t i t i v e work, l a c k i n g i n t e r e s t

a n d full u s e o f t h e o g e r a t o r s q c a p a c i t i e s , a n d i t s p s p c h o l o g i c a l

c o n s e q u e n c e s explain i n l a r g e p a r t t h e j o b d i s s a t i s f a c t i o n

e x p r e s s e d b y t h e ma- jos i ty of o p e r a t o r s . T h i s a l so e x p l a i n s t h e

h i g h e r f ~ e q u e n c y of p s y c h o s o a a t i c d i s o r d e r s , nervous

d i s t u r b a n c e s and i n a d e q u a t e s l e e ~ p a t t e r n s [E l ia s e t a l , , 1989) ,

T h e d e g r e e of f a t i g u e is d i r e c t l y p r o p o r t i o n a l to t h e s a t e of

p r o c e s s i n g d a t a . F a t i g u e - i n d u c i a g jobs are s p r e a d i n g w i t h the

same p a c e a s t e c h n o l o g i c a l advances. ltdis a r e s u l t , i n t h e n e a r

f u t u r e ii will be n e c e s s a r y t o select chrfrs t r om among those

~ e o ~ l e hav ing a h i g h stress t o l e r a n c e f r ( E l i a s et a l , , 1980) .

According t o Snyder [ S c i g u e s t , 3981) much bad design can f;e

traced t o e m p l o y e r s w h o a r e l o o k i n g f o r t h e c h e a ~ o s t p o s s i b l e

s y s t e a and d r i v e workers i n a d e h u ~ a n i z i n g f a s h i o n t r y i n g to g e t

t h e most r e t u r n f o r t h e l e a s t c o s t o u t of VDT i n s - t a . l l a t i o n s a n d

employees a l i k e , S h i f t v o r k has a p ro found effect on t h e bodyls

c i r c a d i a n rhythms, The p h a s e s h i f t i n g of waking and s l e e p i n g

t i n e s t a k e s place w i t h o u t a c o r r e s p o n d i n g shift i n t h e phas ing

of t h e donrinant s y n c h r o n i z e r s (Coe e t a l , , 1980). The resu l t atay

be s u b j e c t i v e f a t i g u e and s o m a t i c c o m p l a i n t s a s well as a

d i s r u p t i o n in p e r f o r ~ a n c e [see t h e September 1979 i s s u e of

Ergonomics f o r a t h o r o u g h r ev i ew of s h i f t w o r k e f f e c t s ) . Stress a n d f a t i g u e is a coaBon proklem i n any o f f i c e

e n v i r o n m e n t and t h u s i t is n o t c o n f i n e d t c VDT c a u s e s , A NI05H

r e s e a r c h tea@ was asked t o e v a l u a t e f i v e p a r t i c i p a t i n g work

s i t e s i n San F r a n c i s c o i n w h i c b VDTs %ere r o n t i n e l y u s e d (Smith

e t al., 1981) , A q u e s t i o n n a i r e d e a l i n g w i t h working c o n d i t i o n s ,

j o b stress f a c t o r s , h e a l t h c o m p l a i n t s and p s y c h o l o g i c a l m o d

s t a t e was f i l l e d out by a p p r o x i m a t e l y 250 VDT o p e r a t o r s and 150

nun-ope ratars . F o r s t a t i s t i c a l F u r p s e s , t h e r e s u l t s f ram a l l

f i v e w o r k p l a c e s were ~ o o . l e d . The r e s p o n d e n t s t o t h e

g u e S t i o n n a i r e s u r v e y were p u t i n t o t h r e e g r o u p s based o n t h e i r

WOE k a c t i v i t i e s . These were { f ) p r o f e s s i o a a l s u s i n g VDTs s u c h as

r e p o r t e r s , e d i tars, c o p y e d i t o r s and p r i n t e r s - T h e s e jobs

a f f o r d e d a g r e a t deaf o f s e l f - c c n t r o l o ~ e r work a c t i v i t i e s which

p r c v i d e d v a r i e t y a n d c h a l l e n g e , T h e o p r a t o r s were not t i e d t o

t h e i r V D T s f o r any set t i n e p e r i o d a n d c o u l d set their own

uorkpace w i t h i n d e a d l i n e limits, [Z) T h e c ler ical VDT o p e r a t o r s

i n c l u d e d data e n t r y c l e r k s , d a t a r e t r i e v a l . c l e r k s , c l a s s i f i e d

a d v e r t i s i n g c l e r k s , c i r c u l a t i o n a n d d i s t r i b u t i o n clerks a n d

t e l e p h o n e inquiry c l e r k s . T h e s e j o b s were h i g h l y r e g i m e n t e d ,

w i t h l i t t l f o p e r a t o r c c n t r ~ l o v e r work a c t i v i t y . The o p e r a t o r s

were t i e d t o the i r w o r k s t a t i o n for f i x e d time p r i o d s e x c e p t f o r

f o r m a l i z e d w o r k / r e s t b r e a k s a n d h a d l i t t l e c o n t r o l o v e r t h e i f

workpace , 13) Non-VDT u s e r s s e ~ v e d a s c o n t r o l s u b j e c t s , T h e i r

j o b s were i d e n t i c a l t o t h o s e of t h e c lerical VDT o p e r a t o r s ,

except they d i d not u s e t h e VDT i n p e r f o r m i n g t h e i r job tasks.

T h e i r w o r k i n g c o n d i t i o n s were a l m s t i d e n t i c a l t o t h o s e of t h e

clericaf VDT o p r a t o r s .

Significantly Bore clericaf VDT operat crs r e g o r t e d job

stress p r o b l e r a s t h a n d i d p r c f e s s i o r n a l s using VDTs or c o n t r o l

s u b j e c t s , while both clerical and p r o f e s s i o n a l VDT o p e r a t o r s

r e p o r t e d more career problems t h a n d i d c o n t r o l s u b j e c t s , I n

t f r a s o f t h e t e r d i n e n s i o n s of t h e work e n v i r o n m e n t a l scale a l l

groups r e p o r t e d 1 e s s i n v o l v e m e n t , less c o h e s i o n , less s t a f f

s u ~ ~ o r t , less aotonoay, g r e a t e r ucrk p r e s s u r e , less t a s k

o r i e n t a t i o n , less c l h r i t y , less i n n o v a t i o n and less p h y s i c a l

comfdrt t h a n t h e norms. O n l y t h e ~ r o f e s s i s n a l VDT w o r k e r s

r e p o r t e d positively w i t h r e s p e c t to test n o r @ s i n t h a t t h e y

r e ~ o r t e d less s u p e r r r i s c r y c c a t r o l t h a n t h e nor@, Also, the

cler ica l VDT o p e r a t o r s bad s i g n i f i c a n t l y less p e e r c o h e s i o n a n d

job autonomy, more work p r e s s u r e a n d g rea t en : c o n t r o l by t h e i r

s u p e r v i s o r s t h a n e i t h e r ~ r o f e s s i o n a l L s u s i n g V D T s o r c c n trol,

s u b j e c t s . T h e y r e p o r t e d less i n v o l v e m e n t and s t a f f s u p p o r t t h a n

t h e p r o f e s s i o n a l s u s i n g VDTs,

T h e n i n e job d e m n d d i m n s i o n s d e v e l o p e d by t h e I n s t i t u t e

f o r S o c i a l R e s e a r c h a g a i n showed s y s t e m a t i c n e g a t i v e r e s p o n s e s

when compared u i t h n o r a s , Cler ical VDT o p e r a t o r s r e p o r t e d h i g h e r

workload, a o r e boredom, g r e a t e r work d i s s a t i s f a c t i o u , greater

j o t f u t u r e ambiguity and l o u e r self-esteem than e i t h e r t b e

p r o f e s s i o n a l s using VDTs o r t h e c c n t r o l s u b j e c t s , They a l s o

r e p o r t e d inore r o l e ambiguity t h a n t h e p r o f e s s i o n a l s u s i n g YDTs

w h i l e the l a t t e r r e ~ O r t @ d less boredom t h a n the c o n t r o l s . Again

t h e sage g e n e r a l p a t t e r n of stress r e s y o n s % a s o k s a v e d i n t h a t

c l e r i c a l BCT o p r a t o r s showed t h e h i g h e s t stress levels,

f o l l o w e d by c o n t r o l s u b j e c t s a n d t h e p r o f e s s i o n a l QDT o p e r a t o r s .

O f t h e s i x s c a l e s o f t h e ~ r o f i f e of mood s t a t e s , o n l y f o r

the f a t i g u e s c a l e uas t h e r e a s i g n i f i c a n t d i f f e r e n c e - the cler ica l VDT uarkecs repor ted more f a t i g u e t h a n d id e i t h e r the

p r o f e s s i o n a l s using V D T s o r t h e c o n t r o l s u b j e c t s . H e a l t h

c o r n ~ l a i n t s by t h e VDT o F e r a t o r s uere of a v i s u a l ,

t i l u scu foske l e t a f and e m o t i o n a l n a t u r e , T w e n t y- s ix of 59 h e a l t h

c o m p l a i n t s examined were s i g n i f i c a n t l y h i g h e r for the c l e r i c a l

VOT w o r k e r s ttaa'n f o r t h e c o n t r o l s .

T h e p r o f e s s i o n a l V D T o p e r a t o r s d i f f e r e d s i g r i f icarn tl y from

t h e controls i n t h a t c o ~ ~ l a i n k s of b u r n i n g e y e s , eye s t r a i n a n d

i r r i t a b i l i t y v f r o h i g h e r w h i l e c c m p l a i n t s of f a i n t i n g , pain down

t h e arm, a n d c o l d s were fewer i n number , Sowever a c u r i o u s

f i n d i n g p o i n t e d o u t by these r e s e a r c h e r s is that t h e m were e v e n

a o r e d i f f e r e n c e s i n t h e number of h e a l t h complaints b e t u e e n the

cler ical a n d p r o f e s s i o n a l V D T o ~ e r d t o r s (33 i n n u m b e r ) . T h i s f e d

t h e a u t h o r s t o c o n c l u d e t h a t r e s u l t s i n d i c a t e t h a t job

c o n t e n t factors and BDT u s e i n t e r a c t t o c o n t r i b u t e t o VDT

o p e r a t o r prof;i lents, , .The p r o b l e m d a e s n o t l i e s o l e l y w i t h VDT

nsen {Sra i th e t a l - , 1981)-

T h e authors r e a d i l y adreit saw p r o k f em w i t h t h e s t u d y

des ign:

Y P h i s e v a l u a t i o n Bay h a v e l i m i t e d g e n e s a . l i z a b i l i t y , s i n c e t h e study sites were n o t selected a t randona, hat r a t h e r were knom so n r c e s of unicn c o m p l a i n t s a b o u t h n % l & L m r - h l ~ a - r * r ; u r ~ r k ysvltrzcua, 8 0 ~ ~ 0 F f ~ , ~ i i ~ k i ~ i p d i i t ~ were n o t selected r a n d o a f y , b u t uerc v o l u n t e e r s , and d i f f i c u l t : l a b o r n e g o t i a t i o n s were u n d e r w a y a t the time of d a t a c o l l e c t i o n .tt

A l l g r o u p s e v a l u a t e d , i n c l u d i n g t h e c o n t r tf. s u b j e c t s , r e p o r t e d

h i g h l e v e l s of p s y c h o s o c i a l job stress when coapared t o worker

groups e x m i n e d u s i n g s imilar masafes i n previous s t u d i e s , The

s t r a i n e d l a b o r a e g o t l a t i o a s p r o d u c e d by d i f f i c a l t e rap loyee /

managemen t r e l a t i o n s w h i c h were a l l u d e d t o above, way h a v e

c o n t r i b u t e d t o t h i s h e i g h t e n e d stress l e v e l . T h e c o n t r o l

s u b j e c t s i n p a r t i c u l a r h a d the p t e n t i a l for g r e a t stress i n

t h a t t h e y uere a u a r e t h a t they w u l d b e c o n v e r t i n g t o V E T S

w i t h i l a months, his e l e v a t i c n Bay a c c o u ~ t for the l a c k of

extensive d i f f e r e n c e s i n stress l e v e l and h e a l t h c o l n p l a i n t s

between t h e p r o f e s s i o n a l s u s i n g VDTs a n d t h e c o n t r o f s u b j e c t s ,

T h e a u t h o r s a l s c a d ~ i t t o d i f f e r e n c e s i n t h e d e m o g r a p h i c s

of t b e t h r e e groups, Significant d i f f e r e n c e s v e r e f o u n d i n t h e

p e r c e n t a g e s o f r e s ~ o n d e n t s i n t h e v a r i o u s c a t e g o r i e s f o r age,

s e x , e t h n i c b a c k g r o u n d , level o f s c h o o l i n g , m a r i t a l sta tus ,

y e a r s with c u r r e n t ~ m p l o y e r a n d y e a r s a t tfae c u r r e n t j o t ,

W h e t h e r t h e r e vere d i f f e r e n c e s i n e n v i r o n m e n t a l a n d V D T

v a r i a b l e s aaong t h e t h r e e g r o u p s i s a p e r t i n e n t lnatter,

Staamerjohn e t al, (1981) c o n d u c t e d a n o n - s i t e e v a l u a t i o n o f YDZ

v o r k s t a t i o n d e s i g n a t the same jive e s t a b l i s h s e n i s ,

U n f o r t u n a t e l y b e c a u s e t h e survey bas anonymous, it gas n o t

p o s s i b l e t o l i n k g u o s t i o n n a i r e r e s p o n s e s t o s p e c i f i c d e s i g n

f e a t u r e s . However, i a p o r t a n t p h y s i c a l env i rcn t r ren t a n d VDT

workstation v a r i a b l e s which a a y h a v e i n f l u e n c e d t h e sywptomologp

were present,

T h e i l l u a i n a t i o n l e v e l s fcauad were b e t w e e n 300 and 1200

l u x . A r a n g e of 300 t o 500 lux is r e c o ~ ~ e a d e d * R e f l e c t e d g l a r e

frrsrr windows a n d l i g h t f i x t u r e s was fcvnd i n most o f t h e VDT

s c r e e n s s u r v e y e d , Eilany of t h e viewing a n g l e s v e r e l a r g e r t h a ~

r e c o m e n d e d e s p e c i a l l y f o r @ale o p e r a t o f s o f g r e a t e r than median

d i l n e n s i o n s . F e u c h a i r s had a n y f o r m of arm rest,

I n r e s p o n s e t o a g r o u p of q u e s t i o n s concerning t h e o f f i c e

e n v i r o n m e n t , most e l a p l o y e e s ( 6 3 3 ) r a t e d surnaer t e l n p e r a t u r e s a ~ d

l e v e l o f d i s % x a c t i o n a s t o o h i g h , A s i g n i f i c a n t l y l a r g e r

~ r d ~ c r t i o n o f t h e VET o p e r a t o r s (80%) t h a n t h e n c n - o p e r a t o r s

(62%) reported glare from workstation l i g h t i n g . The most

frequent complaints were screen g l a r e (85%) . charac ter

brightness (70%). r e a d a b i l i t y [6'3%), f P i c W r 168%) and screen

It i s i n t e r e s t i n g t o ?note t h a t while Swi t f i ' s r epor t

e a p h a s i z e d VDP clerical v e r s u s professicna l cge ra tor

dif ferences , Starmerjcfinas repost only gave a cursory

comparison. T h e clerical VD'I. workers found t h e i r c h a i r s

s i g n i f i c a a t l y less coafor table t h a n d i d e i t h e r t h e profess ional

V D T workers o r t h e non-VDT o p e r a t o r s , It is noted that f o r both

profess ional and clerical VET opera tors, a significant

r e l a t i o n s h i p e x i s t e d between visual function c o a p l a i n t s and t h e

enployee r a t i n g of the u o r k ~ l a c e design g a r a a e t e r s including

glare, screen angle, noise fro^ t h e BDTs a n d screen f l i c k e s ,

A lnost important d i s t i n g u i s h i n g f a c t o r appears t o sepa ra te

c l e r i c a l fro@ ~ r o f e s s i o n a l VDT work. T h a t i s t h e workload, a s

defined by the arttcunt of tinre spent d o i n g VDT work and t h e

nuaber of f o r a a l and iaf ormal rest b r e a k s a f lowed, Prof e s s i o a a l

VDT ope ra to r s "were n o t t i e d t o t h e i r VOTs for a n y set ~ e r i o d

a n d c o u l d set t h e i r own workpace", I n c o n t r a s t , c l e r i c a l V03:

opera to r s " w e s ~ t i e d t o their workstat ions for f i x e d time

periods e x c e p t f o r f ornsalizfd uorkJrest breaks*', Pn fact these

r e sea rcher s shcwed a s t a t i s t i c a f l y significant p o s i t i v e

c o r r e l a t i o n between the number of h o u r s worked on the VDT and

t h e t c t a l aunber. of heal th contpfaints. The researchers conceded

t h i t the reporting cf s i g n i f i c a n t l y more vision ~ r o b l e m s t b a n

S u b j e c t s

TBe subjects f o r t h e q u e s t i o n n a i r e stuBy were 1100 u o r k e r s

belonging t o t h e Office and P r o f e s s i o n a l E m p l o y e e s U n i o n i n Neu

York. Pour hundred n i n e t y - s e v e n males and s i x huadred one

ffmafes p a r t i c i p a t e d , T h e s u b j e c t s raaged i n age f r o n 19 t o 5 5

y e a r s , t h e a v e r a g e a g e being 35.5 y e a r s ,

For the p u r p o s e s of t h i s analysis s u b j e c t s were d i v i d e d

into p r o f e s s i o n a l or cf e r i c a l BDT or non-VCT categories. The

C i c t i o n a r y of O c c u ~ a t i c n a l Titles j 1977) was used to classify

e a c h job t i t l e a s belonging i n t h e $ * P r o f e s s i o n a l , ' t e c h n i c a l and

m a n a g e r i a l o c ~ u p - t i c n s * ~ c a - t c g o r y or t h e -Clerical a n d sales

ccci i~at ions" zatagory, In l i ~ p e n d i ~ B t h e a p p r o p r i a t e iE%

t h r e e - d i g i t o c c u p a t i o n a l g r c u p d e s i g n a t i o n for each job t i t l e is

listed, VDT cases were chosen f r o @ t h o s e a n s w e r i n g * * u s u a l f y o r

a l w a y s J s fof t h e VD'I/CRT section of t h e q u e s t i o n o n t h e type of

e q u i p m e n t u sed f o r u o s k , w h i l e on-VDT cases a re those

indicating f l r a r e l y " or p r o v i d i n g no indication a t a l l ,

A d m i n i s t c a t i o n of t h e Q u e s t i o n n a i r e

The g u e s t i o n n ' a i r e was h a n d e d o u t i n J a n u a r y 1982 by u n i o n

s t e v a r d s to 0 , P I E , 3 C , U , unicn raewbers working in gen York and New

Jersey off ices . E l e v e c h u n d r e d r e p l i e s %ere r e c e i v e d b y mail,

The q u e s t i o n n a i r e used c o v e r e d d e m o g r a p h i c v a r i a b l e s , j o b

d e s c r i p t i o n , p s y c h o s o c i a l aspects o f the trork e n v i r o n m e n t ,

p h y s i c a l e n v i r o n w e n t f ea tu res , VDT p a s t i c u l a r s , p e r s o n a l h a b i t s ,

h e a l t h symFtoms a n d h e a l t h h i s t o r y , See Append ix A f o r a c o p y of

t h e # a r k E n v i r o n r a e n t S u r v e y q u e s t i o n n a i r e , for the ~reliminary

a n a l y s e s a 1 l q u e s t i o n a i r e s received were e v a l u a t e d , regard less

o f t h e t y p e of o f f i c e or b u i l d i n g the r e s p o n d e n t worked i n *

R e s u l t s -----

W hethes y u e s t i c n n a i r e r e s p o n d e n t s were 6 r a f e s s i o n a . f or

clerical VDT 5s nun-VDT workers %as c r o s s - t a b u l a t e d with s u c h

c h a r a c t e r i s t i c s a s beafth s y m ~ t o m s , stress factors , e r g o n o m i c

c o m p l a i n t s arnd s m o k i n g h a b i t s , The n u l l h y p o t h e s i s #as t h a t

t h e r e would b e no d i f f e r e n c ~ s i n p h y s i c a l , ~ s y c h o l o g i c a l and

b e h a v i o u r a l p a r a m e t e r s b e t w e e n VDT workers a n d t h e i r c o n t r o f s ,

It became c l e a r l y e v i a e n t that p s a f e s s i o n a l VDT w o r k e r s

e x p e r i e n c e d t h e g r e a t e s t nuaaber o f h e a l t h - r e l a t e d c o r a ~ l a i n ts,

T a k l e 1 e x h i b i t s t h e h e a l t h symgtams u h i c h were e x p e r i e n c e d a t

least o n e t o t h r e e tiws a week. The p e r c e n t a g e s a n o n g the types

of wrkers which are indicated b y an asterisk were s i g n i f i c a n t l y

different ( C h i - s q u a r e d a n a l y s i s , p<d),05) ,

T a b l e la: Job T y p e b y Fercent C o m p l a i n i n g o f Health

P r o f l e r a s a t Least Once a Week

prof , c l e r i c a l prof, c ler i c a 1

V D P VDT non-V DT non -V DT

V i s u a l --- *Blurred v i s i o r 35 .5

* E y e i r r i t a t i o n U2 - 9

S p l i t or d o u b l e v i s i o n 12.7

+Trouble f o c u s s i n j 30.2

C a r d i o r e s g i ---- ratory

*Hose irritation 28,4

Brea th ing difficulty 14,3

C h e s t p a i n or t i g h t n e s s 12.7

*Racing heart l 4 , 3

S o m a t i c ------- *Nausea 1Y.3

S k i n r a s h e s 7 -9

R i n g i n g in e a r s 19 -0

*Sore t h r o a t , cold 25 .4

* F r e q u e n t u r i n a t i c n 25-U

* p<0,115 b y C h i - s q u a r e d a n a l y s i s

F a b l e Ib : Job Type by Percent C o n p l a i n i n g of Health

E ~ a b l e ~ s at Least Once a Week I I

prof*

VffS

clerical prof. clerical. 1 I

V DT now Y DT ma-VDT

Musculo~&eletal

*Beck a c h e 42.9 31.6 3U-9 21.1

*Backache

Ps ~ p s oiaa ti.^ -- *Headache

*Dizziness

*Pat i g u e

*Sf eepiness

*Moodiness

*D~pressiofi

* L i g h t h e a d e d n e s s

*Confusion

* p < Q . 0 5 by Chi-squarei f a n a l y s i s

P r o f e s s i o n a l VDT w o r k e r s e x h i 3 i t e d t h e h i g h e s t p e r c e n t a g e

o f h e a l t h c o i a p l a i n t s for 17 o u t of 39 s y m ~ t o a s which were

s i g n i f i c a n t l y d i f f e r e n t - V i s u a l , c a r d i o r e s p i r a t o r y a n d

p s y c h o s o & a t i c s y s p t o m s s h o v e d a d e c r e a s i n g p a c e n t a g e i n

r e s F o n s e f o r p r o f e s s i o n a l f o f l o w e d by c l e r i c a l VDT ~ o r k ~ r s a n d

n e x t f o r p r o f e s s i o n a l f o l l o w e d by clerical non-BDP w o r k e r s . The

e x c e p t i o n s were t h e c o ~ p l a i n t s of r a c i n g h e a r t a n d conf u s i o a ,

w h i c h were h i g h e s t f o r professional non-VDT w o r k e r s , As well,

t h e c o m p l a i n t s of a o o d i a e s s and d e p r e s s i o n f o l l o w e d a p a t t e r n

whereby n e x t a f t e r p r o f e s s i o n a l VDT w c r k e r s , g r o f e s s i o n a f

non-U DT w o r k e r s showed a h i g h e r ~ e r c e n t a y e of coraplaints t h a n

clerical VDT workers, T h i s p a t t e r n u a s r e p e a t e d f o r

i g u s c u l o s k e l e t a l a n d somatic s y m ~ t o m s , f t is of i n t e r e s t t o n o t e

t h a t a l l m u s c u l o s k e l e t a l and p s y c h o s o ~ a t i c synrptoms showed a

s i g n i f i c a n t d i f ferentiaf r e s p o n s e a c c o r d i n g to jok category,

This i n d i c a t e s t h a t these t y p e of syniptoms i n p a r t i c u l a r are

a f f e c t e d by VDT u s e a s well a s job d e f i n i t i o n . The p a t t e r n of

h e a l t h c c l a g l a i n t s i s r e f l e c t e d i n a b s e n t e e i s a i n t h a t

p r o f e s s i o n a l n o r k e r s h a d t h e l o n g e s t p e r i o d s off work. The

frequency found f o r n i n e o r more d a y s o f f work was 45-03 of

p r o f e s s i o n a l nun-VDT v o ~ k e r s a nd 9.5 R of p r o f e s s i o n a l B EIT

workers. I n c o n t r a s t , c l e r i c a l w o r k e r s had a f r e q u e n c y of 5% a n d

less,

V a r i o u s e l e m e n t s which c o u l d c o n t r i b a t e t o t h e d i f f e r e n t i a l

response t o h e a l t h g r tA3ems were c o n s i d e r e d . Stress f a c t o r s were

p e r c f i w e d a s p l a y i n g a ~ r i r n a c y role in the j o b d i s c o m f o r t

e x p r i e n c e d by profess ional workers, b o t h in t h e BDT a n d nOn-VDT

categories. The f o l l o w i n g stress factors, as i n d i c a t e d ty an

a s t e f i s k in T a b l e 2, yere found to d i f f e r s i g n i f i c a n t l y Tor each

job t y p e as a result of ch i - squared a n a l y s i s [p<O=O5).

T a b l e 2 : J o b Type by P e r c e n t Compla in ing of Stress

s t r e s s o r s prof, c l e r i c a l p r o f , clerical

YDT YDT non-vdt non-vd t

*No d e c i s i o n - a a k i n g 31 .7 12-3 3 7 , '? 15.9

*Mu job f z e e d o ~ 41.3 22 -2 33 .8 19-2

*Canit set work s p e e d 38. 3 20-6 44 - 7 13.3

Canat a f f e c t work policy 72-1 72.7 70-6 6 4 . 3

*Pots job security 9.7 5 . 3 22-2 6* 6

*Job requifes fast work 61-9

*Requires concentration 58.3

*Job is monotonous 30.6

Bust exert physical effort 7 . 9

*Awkward work motions used 1 4 . 3

No help f roa co-uorkers 74-5

l o help from s u p e r v i s o r 12-9

*Abuse frog customers 2 2 . 4

Abuse from s u ~ e r v i s o r s 5 - 2

Atuse from co-uorkers 7 - 3

*Met enough p e o p l e 22-2

*Remain i n one l o c a t i o n 73-0

* p<D.fafi by Chi-squared ana lys i s

Two-thirds of t h e 18 potential stressors were found t o

d i f f e r significantly a c c o r d i n g t o t h e t y p e of job- T h e stress of

b e i n g r e q u i r e d to work f a s t showed the g r e a t e s t d i f f e r e n t i a l

response with t~ 1.9% of p r o f e s s i o n a l VDT w o r k e r s c o m p l a i n i n g i n

c o m ~ a r i s o n t o t h e n e x t h i g h e s t rate of 3QX f o r clericaf VDT

workers, Only for the s t r e s s o r s of not h a v i n g e n o u g h people ia

t h e diepartrrrenl and f a c i n g job l o s s o r layoffs uas t h e r e a

g r e a t e r p e r c e n t a g e cf c o a p l a i n t s from clericaf non-VDT w o r k e r s ,

followed by c ler ica l VDT workers,

30 s i g a i f i c a n t dif f e r e n c ~ i n s m o k i n g habits was discerned,

For exaleple, c u r r e n t stttckers formed 64, 5% of p r a f e s s i c n a l V D T

w o r k e r s and S t , S X of profess ional non-VDT workers while 51,8X of

c l e x i c a f flLT workers and 55.6 o f clerical acn-VDP w o r k e s s were

smokersd T h e r e aFEears t o be a trend of @ore stnokers a n o n g the

professionals. Yet when smrtokiny a t vosk was e v a l u a t e d a

s i g n i f i c a n t d i f f e r e n c e was s e e n i n which clerical non-VDT

workers i n c l u d e d ittore s m o k e r s who were ~ e r ~ i t t e d t o s m o k e a t

work. Reports of s a o k e r s being a f l o v e d t o s ~ o k e at work were

g i v e n by 59.51% o f the c l e r i c a f non-VDT workers, 47.745 of the

c l e r i c a l VDT w o r k e r s , U1,OZ of the p r o f e s s i o n a l VDT workers and

32.52 of the p r o f e s s i o n a l ncn-VDT uorkers.

When aye was c o n s i d e r e d , professional VDT workers weLe

coragosrid of t h e younger age g m u p s , Of t h e 40-65 a g e g r o u p , the

p e r c e n t a g e of p r o f e s s i o n a l . VDT workers was a Zou of '3 1.3% while

c l e r i ca l aon-VDf w o r k e r s f o r m e d t h e h i g h of 33.2%. C l e r i c a l VDT

work~rs had a majority af females (64,383, w h i l e professional.

non-VDT workers had t h e l e a s t [35,2X) a

T a b l e 3 lists those p h y s i c a l enviscn~ent va z i a b l e s t h a t

were found t o 4if f e r s i g n i f i c a n t l y b e t u e e n job types

[Chi-sguared analysis, p(0.05) ,

An e v a l u a t i o n of t h e physical e n v i f o n ~ e n t of the workers

revea led t h a t g r o f e s s i o n a f VDT personse l voiced the n o s t

complaints particularly about t h e q u a l i t y crf roo@ a i r -

Table 3: Job Type Ly Pescent c o a p l a i n i n g cf the P h y s i c a l

Environment

cornpl aint prof,

VDT

*Too little air aovement 6 2 . 3

Too much air moveeent 8 , 3

Lighti ny t o o b r i g h t 5 .6

* L i y h t i a g too d i m 2 3 -0

*Glare on vork surfaces 19.4

*fJra~leasant o d o r s 26.2

Temperature t cc ccld 17 - 5

Temperature too h o t 17 -7

*Air t o o d r y 3 Y , 4

Air too a o i s t 3.3

*Air t o o sa~tokey 2 7 - 9

clerical prof.

VDT noa-VDT

*Uncosf ortable s e a t i n g 40-7 20, U 32 -6 18 .3

* p(0.05 b y Chi-squared a n a l y s i s

T h e g r e a t e s t d i f f erent ia l response was observed tor the

cor t ip la in t cf a lack of a i r aovement. O f t h e professional VDT

workers, 6 2 . 3 % thought i t v a s a p r o b l e ~ a s ccinpared to t h e next

highest value of 36-4s of c l e r i c a l VDT wrkers, The c l e r i c a l VDT

workers d i d r e ~ o f t t h a t glare on vork surfaces was a problem o n

a s l i g h t l y more frequent basis,

As shown i n Table 4 professional VDT workers had t h e f e a s t

freedom to control suc b environmeental parameters as ceiling

l ightirng, a i r ccnditioning, h e a t i n g and ventilation, In

particular, air quality would be affected by a lack of control

of vent i lat ion, a complaint expessed by all. t h e professional

VDT workers,

Table 4: Job Type by A b i l i t y to Control Environment.

+ c e i l i n g lighting

* a i r conditioning

*heating

*ventilation

Unable t o control: pro f . c l e r ica 1 grof . c l e r i c a l

V Dl! VDT non -VDT non- VET

96.Y 82.8 9 1-9 83.1

90.7 93,9 96,O 8 3 - 0

98-4 93-2 96 - 9 81.6

700,O 9 4 - 6 87,O 86,7

* p(0.05 by C h i - s q u a r e d analysis

YDT use has been an Antportant element i n the differential

respodses seen, T h e s u k s e q u e n t analyses w i l l focus on t h e

r e l a t i o n s h i p between the e x t e n t of VDT u s e and t h e p e r c e n t a g e of

conrrplaints f o u n d ,

Onf y three of n i n e Farame ters d e s c r i b i n g bothersome BDT

c h a r a c t e r i s t i c s were found to d i f f e r significantly fro^ one

a n o t h e r acco rd ing to e x t e n t o f VDT u s e , F l i c k e r i n g of t h e screen

was o f t e n h o t h e r s o r e fcr 1 2 - 3 % of u s u a l BDT users cortl~ared to

5 - 4 3 of those #ho r a r e l y use them, S i ~ i f a r l y bright l i g h t i n g

showed a 22.73'; response r a t € for u s u a l VflT u s e r s i n c o n p r i s o n

to 16.7X of ha l f - t i s e users a n d to 10.83 of t h e rare V D X u s e r s .

Brightness of le t ters %as similarly bothersow t o both u s u a l and

r a r e V D T users.

Table 5: Frequency 02 YET Use by ~ o a p l a i n t s Pound to be S i g n i f i c a n t l y Different E e t w e e n G r o u p s b y t h e Chi-Squared Analysis,

rarely <1/2 t ime 112 time of t en

Health 5yspt_oni_s --- F a t i g u e 3 5 - 5 110.3 45-2 48 -5 Sf eepia ess 105 .7 37 -7 47.6 55.9 Neck ache 2 6 - 6 26 - 0 3 3 - 3 3 6 - 7 Blurred vision 19. 4 20 -8 9 - 5 26.2 Eye i r r i t a t i o n 2U - 8 2 2 - 1 11,9 34.1 T r c u b l e f ocuss iag 17 .4 19 -5 7 . 1 2 4 - 5

Stressors ------ No job freedow 21 - 9 9 -2 13-9 27.8 Poor j o b security 10-7 1 ,3 9.8 7 - 1 3ok requires f a s t vcrk 2 7 - 5 31-2 3 5 - 7 S 3 -6 Requires c o n c e n t r a t i o n U9-8 40 .1 50.0 6 1 - 4 '

Abuse f TO@ custoailers 9,9 6.17 5.3 1 7 - 4 Xeifain in one location 60.0 61.0 5Q-0 7 1 - 6

phnsical l33viro~~ent Too little a i r movement 3 3 - 1 37 -7 35 -7 Y 5 - 1

4 3 . Glarf on sxrfaees 1.3- f 9 - 2 19.5 22.3 . U n p l e a s a n t o d o r s 12.6 5 ,3 16.7 19 -4 A i r t c o d r y 17.9 21 .1 24.4 2 9 - 9 Air t o o s ~ o k e y 11,1 6.5 12 -2 20,O Air too s t u f f y 22-tr 22,4 29.3 3 6 - 9 Uncomfortable seating 20 .2 1 0 . Y 24, Y 2 6 - 7

t h e p h y s i c a l eavironment w h i c h were found t o d i f f e r

s i g n i f i c a n t l y a c c o r d i n g t o t h e e x t e n t o f VDT u s e , B s u r v e y o f

the d a t a r e v e a l s t h a t f o r the a a j o r i t y of cases t h e f eas t

percentages of c o ~ p l a i n t s were ~ a d e by t h o s e s~ending h a l f o f

t h e i r t h e or less t h a n h a l f - t i m e o n the V D T s . The

recomeadation of l imi t ed use of the VD?s during t h e uork day is

s u p p o r t e d b y t h i s d a t a ,

The a f o r e - ~ e o t i o n e d da ta were based o n q u e s t i o n n a i r e s

f i l l e d out by 1100 members c = f a n O,P,E.I,U, l o c a l in M e w York..

T h e ~ r o f e s s i o n a l a n d clericaf VDT and non-VDT w o r k e r s b e l o n g e d

t o many d i f f e r e n t o r g a n i z a t i o n s a n d were Located i n a l a r g e

number of f a c i l i t i e s , T h e social . a n d ph y s i c a f e n v i r o n m e n t a t

work t h u s was v a r i e d i n nature. 20 o v e r c o m e t h e d i s c r e p a n c i e s

among t h e w o r k e r s i n t h e i r social miXieu and g h f s i c a l work

e n v i r c n ~ e n t , a n a l y s e s were c o n d u c t e d on one m e c h a n i c a l l y

v e n t i l a t e d b u i l d i n g s i n which w c r ) r e r s from e a c h o f t h e job t y p e

c l a s s i f i c a t i o n s were r e p r e s e n t e d .

I n t o t a l t h e r e s p o n s e s of 199 w o r k e r s were i n v o l v e d , As

e x p e c t e d , i n d i c a t o r s o f t h e n o r k e r s t ph y s i c a i e n v i r o n ~ l e a t were

c o a ~ a r a b l e a m n g job types, T h e r e were no s i g n i f i c a n t

d i f f e r e n c e s among p r o f e s s i o n a l a n d c ler ica l Y D T a n d non-VDT

workers o n a l l facets cE the p h y s i c a l wofk e n v i r o n m e n t , e x c e p t

f o r glafe on t h e vork s u r f a c e s a n d t o o l i t t l e a i s movement, F o r

t h e l a t t e r , i t was t h e p r o f e s s i o n a l VDT w o r k e r s t h a t h a d t h e

L a r ' g e s t percentage cf c o ~ p l a i n t s [ 3 9 . 3 % ) , Clerical OLlT w o r k e r s

hind t h e next h i g h e s t percentage of 24-03, T h i s g r o u p had t h e

b i g hest percentage cf c o m p l a i n t s about g l a r e (20-OW) uhi le ithe

l o w e s t p e r c e n t a g e of c o a p l a i n t s were f roa profess ional VDT

workers (7.1%) , Otherwise the percentage of co~plaints

couccrning t h e quality of a i r aad temperature were r e l a t i v e l y

s i i t l i lar across a l l job types.

O n l y one out of twenty-four ~ o s s i b l e healkh sylaptocas were

r e c o r d e d a t a frequency of oae to three tims a week, T h e

coaplaint of neck ache, f o r which profess ional VDT workers had

t h e h i g h e s t p e r c e n t a g e of 37 .91 ; t h e other v a l u e s r a n g e d from

16.77 for c l e r i c a l V D T uorlers to 37.7% f o r ~ r o f e s s i o n a l non-YDT

workers.

Where d i f f e r e n c e s araong the job i t y p s d i d becoae e v i d e n t

was in the stress elements encountered i n t h e i r work, T h e

fof l o w i n g stressors were f o u n d t o b e s i g n i f i c a n t l y different

aBong profess ional and clerical V D T and non-VDT workers

( C h i - q u a r e d a n a l y s i s , p<O, 0 5 , Table 6 ) .

T a b l e 6: Job Type versus Stress in a B u i l d i n g where

St f e s s has S i g n i f i c a n t l y Different Betveen

Groups {Chi - squared A n a l y s i s , p<O. 0 5 ) ,

stressors prcf, clerical prof, clerical

Y DT V D I non- VDT nan-BDT

No decisio r, nfa k i ay 4 8 - 3 20.0 59.0 2 9 - 1

Mo j o b freedo~ 55.2

C a n s t s e t work s p e e d 5 8 - 6

Pocr job s e c u r i t y 1 0 - 3

J o t requires f a s t work 79 .3

Requires concentration 75 -9

Too much physical effort 10-3

Awkward work iuotions 17.2

PZot enough peo~lf 37 -9

The p l c o f e s s i c n a l w o r k e r s h a d t h e h i g h e s t p e r c e n t a g e s i n t h e

c a t e g o r i e s of en hanced stress, Work p r e s s u r e s were r e p r e s e n t e d

by d i f f e r e n t i a l r e s p o n s e s even within a common s o c i a l framework,

T h e g r e a t e s t d i f f e r e n c e i n r e s p o n s e f r e q u e n c i e s was aga in

o b s e r v e d for t h e c o n p l a i n t cE b e i n g r e q u i r e d t o work f a s t , P o r

p r a f e s s i o n a l VDT workers , 79-32. t h o u g h t t h i s t o be a problem a s

compared t o t h e uext h i g h e s t resFonse rate of U3.3% aaoag

c l e r i c a l YDT wsrkers, Clerical non-VDT workers d i d e x p r e s s a

greater f r e g u e n c y of c o m p l a i n t s about using awkward work ~ o t ions

aria h a v i n g to e x e r t physical effort .

Algoag all the resy ;ondents , p r o f e s s i o n a l VDT worke r s had a

larger p e r c e n t a g e of h e a l t h c o w p l a i n t s t h a n d i d clerical VDI

w c r k e r s or c o n t r o f s , T h i s r e s u l t differs from t h a t of S m i t h et

a f . 11981) who found that cler ica l VDT o p e r a t o r s were most

l i k e l y t o s u f f e r f r c e h e a l t h and stress p r o b l e s s , However the

professional V D T w c r k e s s i n o u r s t u d y had a larger VDT workload

in t h a t they s p n t the aajor i ty of t h e i r time on V D T s , l i h i l e

S a i t h r s p r o f e s s i o n a l YDT w o r k e r s "were not t i e d t o t h e i x VDIs

Pcr any set t i a r : pe r iod" .

An overview of the analysis o f the Neu Ycrk d a t a i n d i c a t e s

t h a t s y ~ p t o ~ s of ~ o c r h e a l t h were relate4 t o a i r q u a l i t y

conrglaints, R e l e v a n t v i s u a l p rob l ems (b l u r r e d vision, eye

i r r ' i t a t ion and t r o u k l e f o c u s s i n g ) r e s p i r a t o r y [nose i r r i t a t i o n )

a n d psychosoma tic sy mgtoms ( ~ L e e p i u e s s , f a t i g u e , headache,

c o n f u s i o n , d i z z i n e s s , d e p r e s s i o n , m o o d i n e s s a n d 3. ight h e a d e d a e s s )

coincided with a p r e d o m i n a n c e o f a i r q u a l i t y complaints [too

l i t t l e a i r nrovement, a i r t o o stuErf3, dry, s s o k e y and u n p l e a s a n t

o d o r s ) . A n a l y s i s of t h e g r o u p s i n one building r e v e a l e d t h a t

where p h y s i c a l e n v i r o n a e n t p r o b l e a s were redaced to o n l y t w o

c o m p l a i n t s , o n l y one h e a l t h symptom uas r e p o r t e d , T h u s i n a

common p h y s i c a l e n v i r o n a r e n t the h e a l t h c o ~ p f a i n t s were vastly

r e d u c e d ,

Banp recent r e p o r t s have focussed cn the p r c b l e m s o f

b u i l d i n g - r f f a t e d illness due to i n d o o r p o l l u t i o n (see S p e n y l e r

and S e x t o n , 1983; S t e r l i n g a n d K o b a y a s h i , 1977) - T h e s y ~ p t o a s

v h i c h a r e linked t o b u i l d i n g - a s s o c i a t ~ d i l l n e s s include

headache, r e s p i r a t c r y p o b l e ~ s , f a t i g u e a n d v i s u a l distress. I t

was fo r t h e p r o f e s s i o n a l VDT workers t h a t a g r e a t e r i n c i d e n c e of

a i r q u a l i t y c o l n p l a i n t s were o b s e r v e d . They a l s o had t h e l e a s t

control over t h e ventilation of their of f i ce e n v i r o n ~ e n t , I t

b e c o ~ e s r e a d i l y a p p a r e n t t h a t good v e n t i l a t i o n of of •’ice space

is a p r e r e g u i s i t s f a r co~fort a t work,

T h e VDT uorkers* c o r a p f a i n t s of v i s u a l and sosatic

discoaf o r t were soaewhat c c n s e r v a t i v e i n f reguency compared w i t h

thcse r e ~ o r t e d i n t h e l i t e r a t u r e , G u n n a r s o n and O s t b e s g f '1977)

•’or exaaple found 60% of t h e i r VDT a o r k e r s c c m g l a i n e d of a t

l e a s t a few t i a e s a w e e k o f e y e f a t i g u e while 19% c o m p l a i n e d of

b l u r r e d v i s i o n , G r a n d j e a n (1980) found 40-50% o f t h e VDT

o p e r a t o r s i n t e r v i e w e d c o ~ p l a i n f d of o c c a s i o n a l v i s u a l

i m g a i r ~ e ~ k s . O f t h e p r o f e s s i o n a l VDT w o r k e r s who r e s p o n d e d t o

t h e q u e s t i o n a i ~ e g i v e n i n t h i s study, Y2 ,9X conaplaixned of e y e

i r r i t a t i o n a t least once a w e e k , while a f i g u r e o f 29-07! was

found for c l e r i c a l . V D T workers. B l u r r e d arision was a prublera tc

36.5% a n d 2 f e 9 F o f profess ional a n d c l e r i c a l VDT w o r k e r s

r e s g e c t i v e l y . Heck a c h e s vere a p r o b l e m t o U2.9X of VCT

p a o f e s s i o n a l u o r k e r s and 31,6% cf clerical VDT o p e r a t o r s . Tc

46,OX o f t h e p r o f e s s i o n a l VDT agerators and 29.0% of t h e

c l e r i c a l VET o p e r a t o r s backacke was apparent more than once a

week. C a k i r et a l , (1 978) r e p o r t e d t h a t 57% of t h e i r VDT u s e r s

had aching necks while 60% had back pains,

P s y c h o s o c i a l . stresses vere e v i d e n t among p r o f e s s i o n a l VDT

w o r k e r s . A particular probleia t c 63,9% of them was b e i n g

r e q u i r e d t o work fast, Gunriarson and O s t b e r g f19771 i n c o n t r a s t

found about o n e - t h i r d o f the ir VDT opesators felt the workpace

was too f a s t . This agrees v i t h t h e f i g u r e o f 34% found f o r

c l e r i c a l YDT @orkers i n t h i s study. O f t h e f ull-tilae VDT

operators 22-73 c o t r i ~ l a i a e d oT b r i g h t lighting, w h i l e a f i g u r e of

37% was f o u n d f o r the O D 1 wcrkers s u r v e y e d by Dainof f e t

a1*,1981),

Differences in t h e percentages of YDT o p e r a t o r s e x ~ r e s s i n g

sy iaptora a t i c, p s y c h o s o c i a l or environt l len t a l cotlrpla inks a ncng t h e

s t u d i e s caa be a t t r i b u t e d t o d i f f e r e n c e s i n task d e f i n i t i o n , as

well ins Zke s o c i a l stress almd p h y s i c a l e n v i r o n m e n t s i a p o s e d upon

the VDT workers,

i l aportant f a c t o r t o r e g u l a t e , M here o p e r a t o r s spent h a l f o f

their time o r Less t h a n halftime using the terminals t h e

f r e q u e n c y o f c o a p f a i n t s c o n c e r n i n g h e a l t h , stress and t h e

p h y s i c a l envi roamenf . d e c r e a s e d , B e c o n t ~ e n d a t i o a s f o r a four hou r

l i a i t of V D T u s e p u t f o r v a r d b y s u c h o r g a n i z a t i a n s a s ARSTS

X1979) s e e e s p a f t i c u l a r l y r e l e v a n t .

T h e q u e s t i o n n a i r e approach has a n u ~ b e r of f i a i t a t i o n s ,

Response was v a l u n t a r p and therefoce not randora, though b y

h a v i n g c o n t r o l s non- re spondan t s c o u l d be s i m i l a r l y r e p r e s e n t e d

i n each job c a t e g o r y , In s o w instances due to l i m i t a t i o n s in

t h e wording of some q u e s t i o n n a i r e c a t e g o r i e s , a i s s i ng v a l u e s

became r e p r e s e n t a t i v e o f a non-response . F o r e x a ~ p l e , t h e lowest

c a t e g o r y of s y z ~ t o s s was a t r e y u e n c y of o n c e per naontb,

Non-resyoase was assunted t o refresent a n e v e r category. Another

liai.tati.cn of a n y q u e s t i o n n a i r e is the lack a•’ o b j e c t i v e

m e a s u r e e e n t s of the e n v i x o a ~ e n t . Bather, it is the employeesa

s u b j e c t i v e p e r c e p t i o n s of t h e i r e n v i r o n m e n t t h a t was e v a l u a t e d .

C, An Experiaental Study to Determine V i s e a l Function Tiffects of

VDT Use

I. I h e Experiaental Study

A c u t e V i s u a f F u n c t i o n C h a n g e s

" I n speaking a b o u t v i s n a l f a t i g u e we are s p e a k i n g a k o u t s o a e t h i n g w h i c h h a s n o p r e c i s e aad unique d e f i n i t i o n " { C o l l i n s , 1959) .

E y e s t r a i n i n v o l v e s p r o c e s s e s t h a t t a k e place i n t h e s e n s o r y

cel ls of the r e t i n a , f a t i g u e of t h e o u t e r and i n n e r muscles of

t h e e y e , c h a n g e s of a t t e n t i o n a n d c e n t r a l n e r v o u s s y s t e m

phenomena , and f i n a l l y , a general fatigue of the e n t i r e b o d y ,

D i s t u r b a n c e s of t h e s u b j e c t e s n o r m a l c l a r i t y of v i s i o n Bay

o c c u r b e c a u s e t h e c i l i a r y and o c u l o - m o t o r muscles c a n n o t

s t e a d i l y a t a in t a i zn t h e proper f o c u s a n d f i x a t i o n . of t h e eyes, The

f o g g i n g of v i s i o n is accoiapanied by a f e e l i n g of i r r i t a t i o n and

a s e n s e of d i l f i c u l t y i n ~ a i n t a i n i n g a t t e n t i o n , B c c o m ~ o d a t i o n

involves a l t e r a t i o n of t h e c o n v e r g i n g power o f t h e crystalline

l e n s of t h e eye, w h i c h m i k e s i t p c s s i b l e f o r t h e eye t o focus

e i t h e r f o r near or d i s t a n t objec ts , b p a c t i o n of ithe c i l i a r y

musc le . The work of a c c o ~ m o d a t i o n r e s u l t s in fatigue of t h e

c i l i a r y i i i u sc l e w h i l e c c n v e r g e n c e , l eads t o a sense of f a t i g u e

r e s b l t i n y froa an i n a b i l i t y t o s u p p l y n e r v o u s energy f r o a within

t h e m i d - b r a i n n u c l e i s u b s e r v i n g eye ~ovements-

S e v e r a l h y p o t h e s e s have b e e n p r o p o s e d t o e x ~ f a i n v i s u a l

f a t i g u e , T h e s e i n c l u d e a n over tax ing of t h e r e t i n a ; c o n s t a n t

shifting k e t w e e n i n t r a - o c u l a r and e x t r a - o c u l a r m u s c l e s i n

a t t e a p t s t o o b t a i n a clear i sage; a n d increased i n t r a o c u l a r

p r e s s u r e c a u s e d by n e u r o - h o z @ o n a l a c t i o n (Smith, l 9 7 9 ) ,

S h a r i t a n d S a l v e n d y 11992) c i te C a r n e r o n * ~ work {1971,3973)

i n which f a t i g u e is v i e w e d a s a g e n e r a l i z e d r e s p o n s e t o stress

over a p e r i o d of time. I n t h i s c o n t e x t , c u ~ u l a t i v e effects

b e c o w i u i p o r t a n t and s u g g e s t t h a t t h e t i a e r e q u i r e d fo r r e c o v e r y

may b e t h e a p p r o p r i a t e index •’ox q u a n t i f y i n g f a t i g u e .

C o ~ p a r e d t o those s t u d i e s w h i c h u s e s i n g l e s a a i ~ l i n g

a e t h o d s , t h e r e a r e few s t u d i e s i n which c e r t a i n v i s u a l

p a x a ~ e t e r s were s l e a s u r e d before a n d after use of t h e VDT, Holler

et a l , (1974) g r o v i d e d t h e f i r s t d e f i n i t i v e #ark i n t h i s area,

T h e f o u r t e e n s u b j e c t s used were a l l e x p e r i e n c e d VBT o p e r a t o r s

who had e i t h e r n o r m a l e y e s i g h t o r wore a p p r o p r i a t e e y e g l a s s e s o r

c o n t a c t l e n s e s . T h e s u b j e c t s u e r e t e s t e d b e f o r e and a f t e x f o u r

h o u r s of V D T work, and a f t e r two one-hour p e r i o d s . T e s t s

i n c l u d e d visual a c u i t y d e t e r m i n e d b y u a l l boards o f h o o k s and

f i g u r e s , c o l o r tests u s i n g t h e H e l ~ h o l t z A p p a r a t u s a n d a

s u t j e c t i v e c o l c r scale a n d q u e s t i o n n a i r e s ,

About o n e - h a l f of the s u b j e c t s r e p o r t e d a d e t e r i o r a t i o n o f

v i s u a l a c u i t y a n d burniog o t the e y e s , a b c u t c n e - t h i r d

c o i n p l a i n e d of h e a d a c h e and o n e - f o u r t h of f L i c k e r i n g be•’ ore the

eyes, ' S u r p r i s i n g l y t h e d a t a f ro ia t h e f o u r - h o u r c o n d i t i o n h a r d l y

d i f f e r e d frorxt the two o n e - h o u r c a n d i t i o n s .

Most s u b j e c t s s h o v e d s l i g h t changes i n c c l o r v i s i o n , with

two in t h e four-hour c c n d i t i o n showing a b o v e n o r m a l s h i f t s , Up

t o t w e n t y m i n u t e s were n e e d e d f o r r e c o v e r y , F i v e s u b j e c t s showed

d e f i a i t e c h a n g e s i n color v i s i o n i n t h e s u b j e c t i v e c o l o u r scale,

Belated to t h e pre l iminary v a l u e , t h e work a t t h e s c r e e n

f o r f o u r h o u r s was, i n nine cases followed by a a y o p i a a v e r a g i n g

o n e - f o u r t h d i o ~ t e r . Perr ttlost of these s u b j e c t s , 15 m i n u t e s was

s u f f i c i e n t r e c o v e r y time. A t t h e end of t h e two one-f iour

c o n d i t i o n s s u b j e c t s shoved a r e d u c t i o n of an a v e r a g e of 1/8

d i o p t e r . Yet I5 a i n u t e s later o n l y t n o s u b j e c t s had recovered.

@bile t h e ~ U ~ ~ U E S c c n c l u d e d t h a t they h a d proven c h a n g e s i n the

functional s t a t e o f t h e o p t i c a l s y s t e m a f t e r extended work a t

t h e d i s ~ l a y s c r e e n , i t was not r e g a r d e d a s a h e a l t h h a z a r d . T h e

issue of w h e t h e r slight measarable c h a n g e s in v i s u a l f u n c t i o n

are i n d i c a t i v e of p f r r a a n e n t tianage r e aa in s con t rovers i a l ,

H a i d e r e t a l , (1980) h a v e shown t h a t a f t e r a f c u r h o u r YDT

work p e r i o d w i t h breaks , a clear a n d l o n g l a s t i n g t e m p o r a r y

m y o ~ i z a t i o n h a v i n g a s a g a i t u d e cE a b o u t 1/4 d i o p t e r o c c n r r e d . It

took t e n t o f i f t e e n minutes t o regain good distance v i s i o n . They

t h e o r i z e d that t h e t e m y o r a r y m y o p i z a t i o n is p r o b a b l y due t o

a c c c ~ r r t o d a t i ye s t r a i n .

B o u r a a t et a l , (7981) u s i n g c o n t r c t l s i n t h e i r s t a d y ,

l ~ s a s u r e d accom~cda t i v e f a c i l i t y , 82)T u s a g e f u r t h r e e h o u r s

p r o d u c e d measurakle v i s u a l fatigue i n t h e eye a o v e m e n t a n d / o r

a c c o m m o d a t i o n ~ a e c h a n i s m , a s ~tleasured by i n c r e a s e d d u r a t i o n s i n

moving fro@ a n e a r p i n t f o c u s t o a P a r point focus (and vice

versa). S u c h v i s u a l changes were n o t present i n a h a r d espy

v i s u a l search task,

F i n a l l y Daiaaoff e t al, (1981) f o u n d , b y q u e s t i o n n a i r e , t h a t

VDT workers h a d s i g r t i f i c a n t l y acre f a t i g u e , t e n s i o n , e y e s t r a i n ,

b l u r r y v i s i o n , neck and s h o u l d e r E E O ~ ~ ~ B S , focus problems a n d

lower b a c k problem after work t h a n before, However t h e r e v e r e

n o i n d i c a t i o n s o f any re-~ust changes i n the o p t o r n e t s i c

n t e a s u r e s of v i s u a l a c u i t y , a n d lateral and v e r t i c a l p h o r i a as a

f u r n c t i o n of VDT work. Rowever Dr. H a i d e r i l n d i c a t e d to them in a

p e r s o n a l c o m n u n i c a t i o n t h a t the l a c k of s i g n i f i c a n t change i n

the o p t m e t r i c r e s u l t s may b e due t o t h e f a c f : t h a t the subjects

were p e r w i t t e d t o take in foraal work breaks on their own

i n i t i a t i v e . The p r e s e n c e of s u c h breaks nay h a v e a c t e d to

m i n i n i z e any ogtcinetric effects,

L e n g t h of Exposure

O n e of t h e f a c t o r s that in f luence t h e l i k e l i h o o d of a n

occupational disease or injury is the aaouat of time that t h e

worker is exposed t o t h e source o f t h e r i s k . A c c o r d i n g t o G r a l l

(1974, a s c i ted by O s t k e s g , 1975) good work organizat ion and

e f f i c i e n t u s e o f rest pauses c a n b e Ear @ore important i n

c c m b a t t i n g f a t i g u e than a n o t h e r u i s e ergonomicalf y good

w o r k p l a c e d e s i g n . One of t h e b i g selling points of VDTs has b e e n

t h e potential • ’of i n c r e a s e d o u t p u t , S u c h claims t h a t a n employee

would have t o h i t 80% more k e y s , Thus t h e job c o n t e n t or aatrtount

of lime s p e n t on v a r i o u s t a s k s i s r e d i s t r i b u t e d . Pox e x a ~ p l e ,

f i l i n g ti@@, error c o r r e c t i c n ard i n f o r s a t i o n r e t r i e v a 1 is

reduced, 83.1 t h e work c a n be. d o n e a t one s t a t i o n . Unfortunately

t h e s e c h a n g e s t e n d t o i n c r e a s e t h e s o n o t o n y and boredom of t h e

j o b w h i l e a t t h e sa@e t i w f a t i g u e is i n c x e a s ~ d k e c a u s e o f t h e

r e r e t i t i o n o r l a ck o f r e l i e f , Tasks are d e s i g n e d w i t h

c o n s i d e r a t i o n of c o q u t e r s p e e d r a t h e r t h a n t h e c a p a c i t y of t h e

worker ( A r n d t , 1980) . A rest p a u s e is a means of overco tn iag or a v o i d i n g t h e

c o n d i t i o n o f o c c u p a t i o n a l l y - i n d u c e d fatigue. I t i s n o t o n l y t h e

l e n g t h of a rest pause that i s i a p o r t a n t , it is a l s o a q u e s t i o n

of when _the pause is t a k e n , D e p n d i u g u p l n t h e n a t u r e of t h e

job, t h e c u n u l a t i v e l e v e l of f a t i g u e can be marked ly r e d u c e d and

o v e r a l l p e r f o r m a n c e improved i n spite of t h e r e d u c t i o n i n

u o r R i n g time p r o d u c e d by h a v i n g f r e q u e n t b u t s h o r t d u r a t i o n rest

p a u s e s [ C a k i r e t a l , t 9 7 9 ) , f t is v e r y d i f f i c u l t t o spec i f g

a g ~ r o p r i d t e aock / res t r cycles for work a t v i s u a l d i s p l a y units,

Their l r n g t h a n d f r e q u e n c y depend upon t h e i n d i v i d u a l , t h e t a s k ,

t h e e n v i r o n a e a t , t h e e q u i p m e n t and a range of otber f a c t o r s ,

Regardless of t h e f i g u r e s laid down t h e r e will b e c i r c u a s t a o c e s

when t h e s t a n d a r d is t o o l o n g (and therefore u n p r o d u c t i v e ) o r

t o o short (and t h e r e f o r e r e s u l t s i n u n n e c e s s a r y f a t i g u e ) .

Acccrding t o Stevart (1999) t h e i n d i a i d u a f i s t h e b e s t judge;

so@& f l e x i b i l i t y t o allon t h e i n d i v i d u a l to a r r a n g e his work t o

s u i t h i m s e l f o r t o rest would be much Better t h a n s t a t u t c r p rest

pauses. Gv'herc; ~ 0 s s i b f . e VDT use s h o u l d be p a r t of t h e user's j o b

r a t h e r t h a n a l l o f it. T h i s a l l o w s fo r t a s k mixes which a v o i d

E X G E S S ~ V ~ P a t i y u e or o c u l a r s y m ~ t o m s ,

I n t h e CLC-LESC s u r v e y 11982) w o r k e r s s p e n d i n g seven t o

e i g h t h o u r s per day on V D T s g e n e r a l l y e x p e r i e n c e d v i s u a l a n d

s u s c u l a r proble~s N a l l a o s t daily" a b o u t two to three times nore

o f t e n t h a n w o r k e r s using V D T s for two h o u r s a day o r less. The

l a r g e s t i n c r e a s e s i n levels of r e p o r t e d p r o b l e m s o c c u r r e d

b f t u e e n those u o r k i n g four hours o r l ess a n d t h o s e working five

o r more h o u r s o n the V3T, V i s u a l , m u s c u i o s k e l e t a l and stress

p r c b l e a s were generally e x p e r i e n c e d a b o u t two to four times @ore

o f t e n i n t h o s e wosking a t l e a s t two h o u r s on t h e VDTs without a

rest b r e a k t h a n i n t h o s e working thirty m i n u t e s or less a t a

t i ~ e cn t h e i r VDT,

Iu a VCT h e a l t h c o l l e c t i v e b a r g a i n i n g k i t , aeraspapsr g u i l d s

uerE r e c o a a w n d e d t o nake rest-time a l l o w a n c e s t h e n u ~ b e r o n e

i s s u e , N f U S H recotamended a 1 5 - ~ i n u t e break b e g i v e n a f t e r two

h o u r s o f c o n t i n u o u s VDT v o r k under a o d e r a t e visual deaands o r

wcrkfoad, In a s t r c a g e r move, a I S - m i n u t e break was reccmended

a f t e r one hour of c o n t i n u o u s VDT vork u n d e r h i g h v i s u a l derrtand,

b i g b w o r k l c a d a n d / o r r e p f t i t i v s or k t a s k s [Duoley , 198 I ) ,

d S T W felt t h a t t h e ataltieulii VDT w r k ia one day s h o u l d b e

n o more t h a n f o u r h o u r s , The Ndtional G r a p h i c a l Association, T h e

H a t i o n a l U n i o n of J o n r n a l i s t s , and APEX are a @ o q t h e o the r

nn ' ions t h a t a g r e e d w i t h t h i s approach , C . U , P . E , demanded t h a t

e v e r y f o r t y n i n u t e s of YDT o p e r a t i o n m u s t b e ba lanced b y a

twenty a i i n u t e rest ~ e r i o d i n a r e l a x i n g p l a c e [Zanrbert, 1980).

In t h e Norwegian government8s r e c e n t l a b o r i n s p e c t o r a t e ' s draft

document t h e r e %ere p r o v i s i o n s fcr workers t o s p e n d only 50% o f

t h e i r t i z e a t work o n t e r a i n a l s , w i t h no acre t h a n two h o u r s

s p e n t on a terminal at any o n e s t r e t c h {Comput ing, l 9 t ? l ) , Even

Bore radical is the A u s t r i a n F e d e r a t i o n o f Salaried E ~ p l o y e e s i n

t h e P r i r r a t e 3a;zsiness Sector's demand f cr @ c n e h o u r cf f a f t e r one

A s a r e s u l t of t b e recent r e p o r t of t h e Labour Canada t a s k

force on ~tticro-elect ronics and e r t i g l o y ~ e n t (1982) anrwandments t o

t h e Canada Labour c o d e h a v e been p r o p o s e d i n v h i c h VDT o p e r a t o r s

sill b e a l l o w e d a formal rest break every h o u r , As well,

r e c c ~ m e n d a t i o n s hawe been made to reduce total YDT work time t o

f i v e hours of the uork day,

E x p e r i l t l e n t a l e v i d e n c e s o f a r a p p e a r s t o s u p p o r t many of

t h e s e recomrr iendat ions , Raft (3976) s u g g e s t e d t h a t there is sow?

evidence t h a t with four h o u r s of c o n t i n u o u s s c r e e n v i e w i n g ,

t e n p c t r a r y eye a f frictions such a s eye-strain and disturbel l

c c l c u r ~ e r c e p t i o n occur, Haider et a l . f 1 9 8 0 ) h a v e s h o w n that

e v e n a f t e r a f o u r h o u r work pe r iod with breaks, a clear

t e m p o r a r y E yopizat i o n h a v i n g a r t iagni tude of a b o u t 1/4 d i o p t e r

cccus. A t h r e e h o u r c o n t i n u o u s vcfk p x i o d 'caithout b r e a k s

showed t h e strarsgest effect. However, Ho l l e r et al. (1975) Zonnd

t h a t even af ter two c o n t i n u o u s h o u r s of VDT work, some opet-atcrs

e x p e r i e n c e d a r e d u c t i o n i n v i s u a l a c u i t y , A v e r a g e r e c o v e r y tiwe

c o n c l u d e d t h a t extensive VDT e x p o s u r e c a u s e d a change i n t h e

functional state o f t h e v i s u a l structure. T h i s change acts

~ o t e ~ t i a f l y as a g e n e r a l systemic, a s well a s a v i s u a l stressor.

Thus VDT o p e r a t o r s a r e recorrtaaended t o b e given a t t h e v e r y

least, a f i f t e e n l a i n u t e break e v e r y two hours,

f i n a l l y , Cot; et al. f1980) f a u n d t h a t v i t h i n the g r o u p o f

VDT o p e r a t o r s whose rate of t a k i n g inforaal workbreaks was

a1 ways low f l e s s t hars f i v e & e x h o u r ) , 6 2 % r e p o r t e d a s t h e n a p i a ;

t h i s d i f f e r e d s i g n i f i c a n t l y f roa t h e 42% f i g u r e found for t h e

o p e r a t o r s w i t h aediam/hiyh r a t e s , The a u t h o r s conc fuded t h a t t h e

t a k i n g o f i a f o r a a f workbreaks a l u m i s n o t s u f f i c i e n t to reduce

the p r e v a l e n c e sf asthenopia. B u t that those who a l s o take a low

f r e q u e n c y of i n f o s n t a l b r e a k s a re gtoae likely t o r e p o r t

a s t henup ia ,

Prorn t h e review of t h e f i t e r r a t u r e i t was a p p a r e n t t h a t ntarny

s t u d i e s t o this d a t e have been l a c k i n g i n several features:

I . u s e of a d e q u a t e c o n t r o l g roups ,

2. u s e o f s t a n d a r d i z e d o p t o m t r i c e v a l u a t i o n procedures, and

3 , an e v a l u a t i o n o f t h e c o n s e q u e n c e s of recoinsended VDT exposure

and rest periods,

The t h e s i s e x p e r i m e n t was d e s i g n e d i r n c o n s i d e r a t i o n of t h e s e

th ree f a c t o r s ,

C h o i c e of V i s u a l F u n c t i a n Eeasures

(1) Critical F l i c k e r F u s i o n F r e q u e n c y

T h e c r i t i c a l flicker f u s i o n f r e q u e n c y ftteasure (ClfF) has

5een u s e d more f r e q u e n t l y t h a n any other v i s u a l t e s t a s a n index

of genera l . CWS f a t i g u e , It was Froposed i n 1941 b y Sinaonson and

E n z e r { c i t e d i n Bartley a n d Simonson, 1975) a s a test r e f l e c t i n g

s u b j e c t i v e f a t i g u e , They found a s i g n i f i c a n t d r o p of t h e CFli i n

c l e r i c a l w o r k e r s and l a b o r a t o r y technicians {-5,4 and -4.6 c p s

resgectively) , I n t h e i r s u b s e q u e n t s t u d i e s aftlphetaaaine prevented

t h e dropJ together w i t h relief of s u b j e c t i v e fatigue, After i t

was f o u n d t h a t a d r o p of CPE a f t e r a l c o h o l i n g e s t i o n was related

to t h e a l c o h o l c o n t e n t of b lood rather than to s e n s a t i o n it was

c o n c l u d e d t h a t t h e CFF was an i n d e x of t h e general s t a t e o f

e x c i t a b i l i t y of v i s u a l p a t h u a y s and p r o k a b l y of the C N S ,

However S i a o n s o n and Brozek i r a . 1948 [ c i t e d i n B a r t f e y ,

1976) f o u n d a n i d e n t i c a l drop i n CPP a f t e r two h c n r s of

s t f e n u o u s v i s u a l work under ade-guate a s w e l l as i n a d e q u a t e

i l l u m i n a t i o n f e v e l s , It was s u g g e s t e d t h a t the d r o p i n CPF uas

r e l a t e d t o g e n e r a l fatigue rathes t h a n t o v i s u a l s t ress p e r se,

S c h a i d t k e i n 1951 { c i t e d i n B a r t l e y , 1976) f c u n d n o t on1 y a

s i g n i f i c a n t d r o p i n CFF i n t y p e s of work i n v c l v i n g v i s u a l effort

[ f i n e assembly, l i n o t y p e and otlicroscopy) b u t also found s u c h a

d r o p a f t e r w e n t a l c a l c u l a t i o n s perforwed by a b l i n d f o l d e d

s u b j e c t , N a t u r a l l y h e conc luded t h a t d e ~ r e s s i o n of C P F is

re la ted t o g e n e r a l f a t i g u e r a t h e r than s t r i c t l y t o v i s u a l

f a t i g u e , C a u t i o n ~gust h e p l a c e d a u t h i s i a t e r g r e t a t i o n a s f o v e a l

C f E d u r i n g d a r k a d a ~ t a t i o n h a s been r e p o r t e d by Brown (1958) to

f a l l .

D u l l , r e p e t i t i v e and monotonous s i t u a t i o n s a l s o p r o d u c e a

d r o p i n CFP. T h e study _by Grandjean et a l , (1977) is

i l l u s t r a t i v e o f t h i s s i t u a t i o n . T h e a o n o t o a o n s c o n d i t i o n

c o n s i s t e d of a s e p e t i t i v e a c t i v i t y [ count ing nails t o a set pace

for three hours), An a c t i v a t i n g c o n d i t i o n i n v o l v e d s t i m u l a t i n g

a n d p l e a s a n t activities s u c h a s p s y c k o a o t o r tests and m u s i c , I n

t h e isonctonons situation a decrease i n CPP cf two hertz gas

f o u n d as well as a shift of &he s e l f - r d t e d s a b j e c t i v e state

towards a decrease o f m t i v a t i o n a n d a b i l i t y for a c t i o n , Tn t h e

a c t i v a t i n g situation CFP d i d n o t change d u r i n g the three h o u r

session,

Little i f any l o w e r i n g of GEF results f ro@ w o r k that

r e q u i r e s o n l y noderate m e n t a l eff crt, and which al lows the

c o m p a r a t i v e f r e e d u a of act ion, or w h i c h i ava fves physical

e f f o r t , Exaraples g i v e n b y Grandjean (1979) are of f ice work,

s o r t i n g jots aad r e p e t i t i v e work a t a m o d e r a t e aenta l level,

while reading was caas i s ten l ly f o u n d act tc: ~ r d n c e a

s i g n i f i c a n t d e ~ r e s s i o n of the CEP [ B a r t l e y and Sitaornson, 1376) . T h e r e s u l t s for cler ica l v o s k e r s are not c o n s i s t e n t . For

example, Sa i to et al, [1981) found c r i t i ca l flicker f n s i o n

f r e q u e n c y t o deter icrate with time both i n i n s p e c t i o n work a n d

clerical work,

A c c o r d i n g t o B a r t l e y and Sinionson (1969) t h e ref a t i v e f

p o o r c o n t r o l of f i e l d c o n d i t i o n s i n o c c u p a t i u n a l work i s a majoz

f a c t o r i n t h e d i s c r e p a n c i e s f o u n d , As well, t h e r e is a l a c k of

s t a n d a r d i z a t i o n of t h e t e c h n i q u e of CPE d e t e r m i n a t i o n , The CFF

depends o a t h e s ize , b r i g h t n e s s a n d c o f o r cf t h e test p a t c h ,

s u r r o u n d i n g i l l u l i l i n a t i o n , state of a d a p t a t i o n and t h e 1 i g h t : d a r k

r a t i c , a a o n g s t othfr t h i n g s ,

The o n l y i n v e s t i g a t o r s t o n l e a s u r e t h e CPF of YDT o p e r a t o r s

were Cakir et a l . (1373, c i t e d by Ostberg et al . 11;79), A d r o p

o f CPP f o u n d a t the end of t h e work shift c o r r e l a t e d h i g k l y w i t h

m u s c u l a r and visual c o n a p l a i n t s ,

(2) C o n t r a s t S e n s i t i v i tg

V i s u a l a c u i t y is t h e c a p a c i t y t o d i s c r i i a i n a t e t h e f i n e

d e t a i l s of o b j e c t s , It is specif i ~ d i n terms of the mininulii

d i m e n s i o n o f some c r i t i c a l a s p e c t s of a test object t h a t a

s u b j e c t can c o r r e c t l y i d e n t i f y . This r e g u i r e s a f r e q u e n c y of

s e e i n g d e % e r m i n a t i o n , a n d t h e t h r e s h o l d size is g i v e n a s the

v i s u a l a n g l e o f t h e d e t a i l t h a t c a n B e c o s r e c t l y d e t e c t e d 50% of

t h e titae. T h e S n e l l e n e y e c h a r * , c o n t a i n i n g letters a n d digits

GE g r a d u a t e d size in h i g h contrast, is t h e t r a d i t i o n a l

optomtric t o o l t o n leasnre v i s u a l a c u i t y , B u t v i s u a l a c n i t p

a l o n e is a p o o r p s e d i c t c r : of o v e r a l l visual p e r f o r m a n c e ( S e k u l e r

and MuLvanny, 1982) - Another way t o assess visual f u a c t i o n is t o d e terwrine

contrast t h r e s h o f d - t h e ai -nu~ua c o n t r a s t n e e d e d t o perceive a

p a t t i c u l a r p a t t e r n . A g r a t i n g o f a n y c o a r s e n e s s c a n be made

o f t h e l i g h t bass a n d t h e l u m i n a n c e of t h e d a r k b a t s [Thorrtas,

19'35). C o n t r a s t s e n s i t i v i t y varies wi th a g e a n d depends , among

other things, upon t h e c o n d i t i c r ; of the e y e " c r y s t a l l i n e l e n s .

S u b t l e l e n s changes, n o t s e r i o u s eslough t o l o v e r v i s u a l a c u i t y ,

can i r a p a i r c o n t r a s t s e n s i t i v i t y , On t h e joD e x p o s u r e t o certairr.

c h e m i c a l s cr t c i n f r a r e d o r l a i e r c u a v e r a d i a t i o n c a n a f f e c t the

l e n s [ S e k u l e r and Blulvanny, 3 9 8 2 ) .

A c c o r d i n g t o Woo (3982) c o n t r a s t s e n s i t i v i t y t e s t i n g c a n

g r o v i d e an " e a r l y rarniag" and can be used t o detect s u b t l e

chaages i n v i s i o n . A s YDT work Bay p r o R o t e v i s u a l f a t i g u e h e

c o n d u c t e d a p i l o t study to B e a s u r e the c o n t r a s t s e n s i t i v i t y

f u n c t i o n of VBT aorrtrers after varying work p e r i o d s . T h e a v e r a g e

curve of c o n t r a s t t b r e s b o l d b y s ~ a t i a f f r e g v e n c y d i d n o t c h a n g e

a f t e r work , However a a n y i n d i v i d u a l s d i d show marked c h a n g e s i n

t h e i r c o n t r a s t seitsit i v i t y f u n c t i o n c u r v e s , Moo s u s p e c t s length

and i n t e n s i t y o f V D T work a r e i ~ ~ o r t a n t d e t e r ~ i n i n g f a c t o r s of

reCuced c o n t r a s t s e n s i t i v i t p .

(3) Accomodat i v e R e s p o n s e

The c h a n g ~ i n t h e r e f r a c t i v e power of t h e eye when t h e

i n a g e of a near ob jec t is b r o u g h t i n t o f o c u s o n the retina is

d e s c r i b e d a s a c c o a m d a t i o n [Davson, 1976) . T h e r a d i u s of

c u r v a t u r e of t h e l e n s s u r f a c e s hecoraes s h o r t e r , t h a t is, aore

convex. T h e Lens thickens a n d t h e p u p i l c o n t r a c t s . ?he H e l m h o l t z

t h e o r y s t a t e s t h a t the l e n s is mare c o n v e x o r t h i c k e r f o r n e a r

v i s i o n b e c a u s e of a r e d u c t i o n i n z o n u f a r t e n s i o n r e s u l t i n g from

c o n t r a c t i o n of t h e c i l i a r y muscle [Cartrpbel l et a l . l 9 7 & ) ,

The class ica l vie% is t h a t the l e a s t e f f o r t o f

a c c o m m o d a t i o n s i l l ke o b s e r v e d when the s t i n t u l u s is a t a far

d i s t a n c e , a s t h e e x t r i n s i c a n d i n t r i n s i c e y e m u s c l e s will be

r e l a x a d then, Q s t b e r g e t al, (1980) s u p p o r t a n a l t e r n a t i v e

h y p o t h e s i s t h a t t h e r e s t i n g focus does n o t c o r r e s p o n d t o

i n f i n i t y , b u t t o a n i n t e r f l t e d i a t e position o f a b o u t one meter,

G u a n a r s s o n a n d S o d e r b e r g 11983) measured the n e a r g o i n t of

a c c o m m o d a t i o a by f i r s t e s t a b l i s h i n g t h e saa.llest line of letters

t h a t c o u l d be read clearly frorxl 30 cra along a near ~ o i n t r u l e r .

A 3 t h e l i n e of letters was reoved closer t o t h e s u b j e c t the near

p o i n t o f a c c o a ~ o 8 a t i o n was d e t e r m i n e d a s t h e point where t h e

letters s t a r t e d to appear b l u r r e d . Bftcr a vork d a y which

i n c l u d e d s i x h o u r s rrf V D T work this near ~ c i n t of accon ta loda t ion

was f o u n d t o i n c f e a s e a n a v e r a g e o f 3 - 5 cm.

C o l l i n s a n d P r u e n (3962) n s i n g a rotating s e c t o r d i s c , bad

s u t jects v i e u single L a n d o l t r i n g s a t two d i f f e r e n t d i s t a n c e s ,

They c o n c l u d e d that t h e t h e requi red tc p e r c e i v e accurately

o b j e c t s a t two d i f f e r e n t d i s t a n c e s is worth c o n s i d e r i n g a s an

i n d i c a t o r o f E a t i g u e ,

K r i v o h l a v y e-l al. (1969) used t ~ i o panels of L a n d o l t r i n g s

t o measure v i s u a l performance i n c o n v e r g e n c e a n d a c c o m m o d a t i v e

s i t u a t i o n s . The s u b j e c t had t o read two L a n d o l t ring p n e l s i n a

serial manner, T h e f i r s t p a n e l was - 5 meters away from the

s u b j e c t and t h e secand was 5 a e t s z s away. The tirae necessary f o r

method, R r i v o h l a v y e t a l , {I9691 f o u n d that f o r s i x female

m a c h i n i s t s , Bean p r f oratlance i n c o n v e r g e n c e and accom~tlodat ion

steadily d i sn in i shed d u r i n g a work s h i f t , X r i o o h l a v y ' s nethod

unf or t u n a t e l y b r o u g h t i n t h e c o n f o u n d i n g f a c t o r s o f h i g h e r - o r d e r

i n f o r ma t ion p r o c e s s i n g r a t h e r t h a n phys i o l q i c a l reflex

phtzaomena. I n a d d i t i c n t o a c c o m o d a t L v e t i ~ e l a g , perce tio on of

t h e L a n d u l t r i n g gap p o s i t i o n is r e q u i r e d , E x t r a n e o u s f a c t o r s

s u c h a s subjective mood w i l l have a g r e a t e r effect upon r e s p o n s e

tirna w i t h this wethcd-

The a c c o a m o d a t i v e facility o f V D T workers was measured b y

Rourant e t a l , (198 1) - Accoocsnodat i v e f a c i l i t y was f o u n d to

Cecrease after VOT work, y e t not a f t e r a hard-copy v i s u a l s e a r c h

task.

O t h e r o b j e c t i v e measures of general fatigue such a s the

s l o w i n g o f p e r c e p t u a l - a o t o r p e r f o r m n e e a s evidenced by an

i n c r e a s e i n r e a c t i o n tint* Rave been c o n s i d e r e d , However due to

t h e s p e c i f i c i t y oE rnen ta l f a t i g u e , psychotautor tests may cause a

t e a p o r a r y arousal which c o u l d mas t a n y p o s s i b l e s i g n of g e n e r a l

f a t i g u e {Grand jean, 1979).

The p u r p o s e of t h e e x p e r i m e n t was to assess whether a n y

v i s u a l f u n c t i o n c h a n g e s or evidence of p s y c h o l o g i c a l f a tigue

o c c a r over a t u o h o u r YDT session. T h e e x p e r i m e n t a l task

i Sub j ~ c t s were i n s t r u c t e d t o m a i n t a i n i n t e n s i t y ~f iraterest

towards t h e task t h ~ o u g h o u t t h e ~ x p e r i ~ e n t a l session, Interest

was maintained b y allowing the subject to choose h i s o r h e r own

t e x t to e d i t , During t h e t w c hoar control s e s s i o n no VDT work

was allowed. Subjects were free to read and relax a t w i l l . ,

S e v e n males and f i v e fenales p a r t i c i p a t e d i n t h e

e x p e r i ~ e n t a l study, They ranged in age frc@ 23 t o 43 years ; the

avasage was 30 y e a r s of a g e .

nxrrl r v U L 02 t h e subjects d i d n o t r e q u i r e c o r r e c t i v e lenses t o

o p e r a t e the VDT, F i v e s u k j e c t s were myo~ic and wore glasses,

while three wore c c a t a c t Leases, The wa-jority had never smoked.

Only one subject was a c u r r e n t s m o k e r o f about three cigarettes

a week w h i l e o n e o t h e r was a former s ~ o k e r ,

Wl1 subjects were paid v o l u n t e e r s , T h e y were g i v e n $10.00

for p a r t i c i p a t i n g i n both t h e e x p e r i m e n t a l and c o n t r o l

c o n d i t i o n s .

All exper i r ~ e n t a l se s s i c n s %ere c u n d a c t e d i n a l a b o r a t o r y

mom, T h e t e m p e r a t u r e ranged f r o & 69 f to 7 3 F, a v e r a g i n g 7 1 E,

T h e h u l a i d i t y , which was d e t e r i n i n e d w i t h a s l i n g p s y c h r o m e t e r

[Tap lo r f n s t r u t ~ e n t Co,, New 'Ilork) a v e r a g e d Q Y X * Roo@

illuaiaation was constant at 1150 l u x a s m e a s n r e d by a G o s s e n

P a n l u x i l l u m i n a t i o n l e v e l meter,

D a r i n g t h e e x p e r i ~ e n t a l s e s s i o n s u b j e c t s vere s e a t e d i n aa

office chair v h i c h was a d j u s t a b l e f o r h e i g h t . On t h e i r own

i n i t i a t i v e * no one deemed i t necessary t o a l t a r the adjustment.

T h e SBA mode l 3101 display t e s n i n a l was p l a c e d on a d e s k , 7 2 , s

can h i g h , T h e keyboard d i s t a n c e was a d j u s t a b l e rrith t h e keyboard

height averaging 7 cnt a b o v e the table level. The v i d e o screen

d i m e n s i o n s were 20 by 25-5 cn w i t h g r e e n l e t te rs b e i n g f o r w e d

from a 7 x 9 d o t aatr ix on a dark background, Up to 2 Y l i n e s o f

80 c h a r a c t e r s each could be e n t e r e d o n the s c r e e n , Reflections

froa t h e overhead fluorescent lighting were n o t i c e a b l e on the

screen face.

The o r d e r o f tfie v i s u a l tests, which were g i v e n b e f o r e a n d

a f t e r the two hour e x p e r i r t i e n t a l session a n d after a 35 Eainute

rest k r e a k , were c o u n t e r b a l a n c e d b e t w e e n t b e cr i t ica l f l i c k e r

f u s i o n (CFP) arnd c o n t r a s t s e n s i t i v i t y measures, as a e f l as t h e

two accoramadative meaznres, For: the costrol s e s s i o n , these

~ t e a s u r e g t e n t s were d c n e before a n d a f t e r the two hour p e r i o d

o n l j f .

F i v e v i s u a l f u n c t i o n rtreasurementz were o b t a i n e d i n t h e

f o l l o v i n g manner:

1, Cri t i ca l F l i c k e r : Fusion - T h e subject was p o s i t i c n e d so h i s

o r h e r eyes v e r e 5 0 crit away fzcm t h e f l i c k e r f u s i o n v i e w i n g

c h a m h e r (model 12026, Lafayette I ns t su r t l en t Co, I n d i a n a ) , The

percentage light was set a t 33, The flicker rate of t h e f l i c k e r

f u s i o n a p p a r a t u s [ m o d e l 12025, Lafayette I a s t r u m e r n t Co,,

Indiana) was a d j u s t e d b y t h e e x p r i m e n t e r i n 0.1 hz i n c r e m e n t s

u n t i l t h e subject c o u l d n o l o n g e r see a n y f l i c k e r o f t h e

s t i m u l u s lamp t h r o u g h foveal vision, T h i s p r o c e d u r e was r e p e a t e d

twice. Accuracg a•’ t h e i n s t r u a e n t Mas + / - , I h z .

2. C o n t r a s t T h r e s h o l d - S u b j e c t s vere s e a t e d 4 , 3 me-ters Erortc an

o s c i l l o s c o p e which d i s p l a y e d s i n e wave g r a t i n g s a t a d i s p l a y

f r e q u e n c y of e i t h e r 30 o r 40 cycles per display o f 11 c a . T h i s

was e q u i v a l e n t t o 20 and 27 c y c l e s p e r degree of v i s u a l a n g l e ,

r e s p e c t i v e l y . T h e p a r t i c u l a r s g a tial f r e q u f n c i e s u s e d were

c h c s e n due to p r e l i m i n a r y f i n d i n g s which showed t h a t d i s p l a y s of

20 o r less cycles, o r 50 or Bore c y c l e s e x c e e d e d t h e c o n t r a s t

r a n g e , F o r this saae reason, a s e a t i n g d i s t a n c e of 4-3 meters

was c h o s e n , T h e contrast f u n c t i o n d i a l a l l o v e d s i a u l t a n e o u s

r e c i p r o c a l a d j n s t ~ e n t of t h e l u m i n a n c e of t h e adjacent l i g h t aad

da rk bars o f g r a t i n g s o that t h e o v e r a l l s c r e e n l u a i n a n c e was

c o n s t a n t r e g a r d l e s s of t h e g r a t i n g c o n i r a s t , The f a n g e of

c o n t r a s t v a r i e d on a n a r b i t r a r y s c a l e of O to t h e highest

c o n t r a s t of 290. Ccntrast Mas progressively d i a i n i s h e d by the

s x @ r i a r e n t e r i n d e c r e m e n t s c.f 3 u n i t , u n t i l t h e presence of t h e

g r a t i n g c o u l d aot be d i s t i n g u i s k ~ d from a u n i f o r a f i e l d . T h i s

procedure was done six t i a t e e i n a l l , w i t h t h e o r d e r o f t h e set

s ~ a tiaZ f r e q u e n c i e s given randoaly,

3. Accommodative response - This faoasure was d e t e r ~ i n e d ky t h e

B a d a l Optometer s e t h o d . A t a r g e t in was a d j u s t e d f o r maximum

c l a r i t y w h i l e a l i g n e d d i r e c t l y b e h i a d a f i x e d 10 d i o p t r e l e n s - A

S n e l f e n e y e c h a r t was p l a c e d a t a 50 cm cfistance, subjects were

p o s i t i o n e d o n a n u ~ r i g h t rest so that t h r o u g h the left e y e

(which was 18 cs away fro@ the l e n s ) t h e y c o u l d see t h e pin

behind t h e l e n s #hi2e through t h e r i g h t eye, t h e e y e cha r t was

v i ~ w d . The s u b j e c t a d j u s t e d t h e p i n - t o - l e n s d i s t a n c e from p a s t

t h e o p t i c a l infinity p a i n t u n t i l . t h e p i n i m a g e becalae clear

while a a i n t a i n i n g the view of the e y e c h a r t .

T h e p r i n c i p l e upon which tke p r o c e d u r e was base4 was

B e r i n g ' s tau of E q u a l I n n e r v a t i o n . A s t i a u l u s t o a c c o ~ ~ o d a t i o n

(the eye chart) %as p r e s e n t e d t o one eye ut t i1 .e the response to

a c c o a t ~ o d a t i o n [ t h e pin-to-lens d i s t a n c e ) was nreasured i n t h e

o t h e r , T h e p r o c e d u r e was c o n d u c t e d t h r e e tirttes,

4. Bccomraodative f a c i l i t y - T h i s v i s u a l f u n c t i o n was a e a s u r e d

uith a s t a n d a r d S n e l l e n e y e c h a r t p l a c e d 6 meters a w a y aud a

n e a r point chart viewed fros a distance of , 2 5 meter. S n b j e c t s

a l t e r n a t e d t h e i r g a z e between t h e f a r a n d n e a r c h a r t s , using t h e

p o i n t a t which t h e letters kecame clear a s t h e s i g n a l t o change .

p e r i o d of 15 s e c c n d s was used t o r e c o r d t h e n u a b e r of t i ~ e s

t h e subject's view kecawe clear a f t e r r e t u r n i n g to the f a r

c h a i t , T h e p r o c e d u r e was n o t r e p e a t e d due t o t h e f a t i g u e effect

of p e r f o r ~ i n g the t a s k ,

T h e r a t i o n a l e for t h e use cf accolamodati 'se f a c i l i t y is that

VET work i o v o f i r e s accomrttodative and c o c v e r g e n c e f u n c t i o n s , due

t o t h e need f o r changing t h ~ f o c u s o f the e y e to the d i f f e r e n t

distances of YDT s c r e e n , keys and document and m a i n t a i n i n g a

fixed g a z e a t t h e s c r e e n .

Q u e s t i o n n a i r e s were f i l l e d out b e f o r e and a f t e r t h e

exper i l tnen ta l c o a d i t i o n and after t h e 15 minute rest p e r i o d .

Similar q u e s t i o n n a i r e s were g i v e n before and af ter t h e

succeeding c o n t r o l period o f non-BDT a c t i v i t y , Repea ted

questions included a p s y c h o l o g i c a l f a t i g u e scale of l u d i p o l a r

f a c t o r s d e v e l o p e d by Graud jean et al, ( l 9 7 7 ) . As well, health

c o i u p l a i n t s r a t e d fron nono to s e v e r e were i n c f u d e a - fo l lowing

t h e e x p e r i n e n t a l c c n d i t i o n a d d i t i o n a f q u e s t i o n s e v a l u a t e d t h e

p h y s i c a l c o n d i t i o n s i n t h e l a b o r a t o r y and p h y s i c a l p a r a m e t e r s of

the VDT. Answers were on a n o r d i n a l scale of "noneti, * * s l i g h t r ' ,

* ' ~ o d e r a te" and *'severem. A copy of e a c h q u e s t i o n n a i r e i s g i v e n

i n Rppendix C,

An a n a l y s i s of v a r i a n c e f o r repeated trneasures (BRDP, 1981)

was conducted on e a c h of t h e v i s u a l f u n c t i o n tests, A

s i g n i f icaat ef •’ect (p<Et,OS) f o r time of measurement [before and

a f t e r t h e e x p e r i ~ e n t a n d a f t e r rest] was found f o r CPP, contrast

threghold at 4 3 cycles o e r 1 1 cw, and accomnaodatirre f a c i l i t v ,

f i g u r e s 1 to 5 show the gray ;hs of t h e aeans o f t h e v a l u e s of

each visual f u n c t i o n at each measurement occasion, The error

bars are +/- one s t a n d a r d error of t h e mean, A p a r t i t i o n e d F

t e s t for m u l t i p l e ccmgarisons revealed that it was t h e

difference B e t u e f n t h e w a n s a f t e r and k e f o r e t h e e x p e r i m e n t a l

c o n d i t i o n that contributed to the significant difference

( p < 0 . 0 5 ) .

CRlPl LICKER FUSION

MEASUREMENT OCCASION

88b

F i g u r e 2. Eean Experimental C h a n g e s i n C o n t r a s t T h r e s h o l d a t 30 I

' I cycles/l lca.

CONTRA

MEASUREMENT OCCASION 89b

F i g u r e 3 . n e a n Experimental Changes i n Contrast T h r e s h o l d at 40

SHOL 4

MEASUREMENT OCCASION 90b

4

Figure 4. Bean ~ x p e r i i f i e n t a l C h a n g e s i a Acccmmcda t i v e Response,

ACCOM ESPONSE

MEASUREMENT OCCASION 9 I b

F i g u r e 5 , Rean Exper imenta l C h a n g s in Rcccmmcda Zive F a c i l i t y ,

IVE FACILITY

MEASUREMENT OCCASION 92b

F o r t h e c o n t r o l s e s s i o n , a n a a a l y s i s of v a r i a n c e f o r

r epea t ed m e a s u r e s showed no s i g n i f i c a n t e f f e c t f o r any of t h e

v i s u a l f u n c t i o n values. A H s N O I T A [SPSS, 198 1 ) a n a l y s i s war; run

to t a k e i n t o a c c o u n t the r e l a t i c n s h i p s be tueez l the IMjaEures o n

t h ~ effect of time cf raeasureiuent* T h e result showed t h a t the

level of s i g n i f i c a n c e was j u s t above t h e rejeefioa l e v e l

(p=D .06) . A two-way a n a l y s i s of variance was u s e d t o d e t e r m i n e i f

there was a n y s i g n i f i c a n t effect o r i n t e r a c t i o s l between t i ~ e of

m e a s u r e ~ e n t a n d t y F e o f t r e a t n e a t ( e x p e r i m e n t a l o r c o n t r o l ) ,

Vhile f o r accrtmirtodative E a c i l i k y , t y p e cf t r e a t n e r t t a l o n e was

s i g n i f i c a n t l y d i f f e r e n t , b o t h f c r contrast t h r e s h o l d a t 40

cyclesJl1 cm, a n d a c c o ~ m d a t i v e f a c i l i t y a s i g n i f i c a n t

i a t e r a c t i o n [p<0-05) was o k s i e r v ~ d . Both figures 6 and 7 r e v e a l

t h a t a f t e r a two h o u r pried t h e r e was a d e c r e m e n t of v i s u a l

f u r c t i o n i n t h e exp~rintentcr l t r e a t m e n t group; t h i s t e i n g t h e

o p p o s i t e t r e n d of t h e c c n t r a l group, P o r e x a m p l e , contrast

t h r e s h o l d vaf ues i n c r e a s e d b y the e n d of the e x p e r i a e n t a l

session w h i l e w i t h t h e c o n t f o l treatment a d e c r e a s e , w h i c h

i n d i c a t e s a n iaprovertlent, o c c u r r e d .

an analysis of v a r i a n c e was a l s o c o n d u c t e d w i t h a g r o u s i n g

f a c t o r ba sed on VDT p a r a r a e t e s c c s y l a i n t s , S u b j e c t s were c l a s s e d

a s low, mediure o r h i g h i n .the VDT p a r a m e t e r complaint scale a s

t o t h ~ frequency i n which they perceived f a u l t s i n t h e V E T , As

observed i n f i g u r e 8 those w i t h high VDT c o m p l a i n t s h a d the

h i g h e s t c o n t r a s t threshold values, u hi-ile t h e l o u ITDT c o r a p l a i n ts

g r o u p consistent ly ha1 d the lowest coatrast t h r e s h o l d v a l u e s

[p<0 ,05 ) , The lover c o n t r a s t v a l u e s i ~ ~ l y a greater a b i l i t y t o

detect c o n t r a s t differences b e t w e e n the ad jacen t k a r s of light

7 1

o f t ke g r a t i n g ,

F i g u r e 6 : Hean C o n t r a s t T h r e s h o l d at 40 cycles/ltcm - E x p ~ r i m e n t a l vs Ccatrcl .

ESHOLD AT 40

b

EXPERIMENTAL

CONTROL

MEASUREMENT OCCASION 95b

F i g u r e 7: 8ean A c c c ~ m c d a t i v e F a c i l i t y - E x p e r i m n t a l v s Control ,

CCO IVE FACILITY

I EXPERIMENTAL

I

MEASUREMENT OCCASION '3 6b

ESHOLD AT

i HIGH

@ MEDIUM

+ LOW

MEASUREMENT OCCASION

9 7b

~ s y c h o l o g i c a l f a t i g u e v a r i a b l e s %ere m e a s u r e d on a f i n e a r

scale, An a n a l y s i s of v a r i a n c e for r e p e a t e d m e a s u r e s was r u n for

t h e e x p e s i ~ e n t a l measures . S i g n i f icani d i f f e r e n c e s (p(0.053 were

found i n t h e direction of t h e f a t i g u e v a r i a b l e f o r t h e

p s y c h o l o g i c a l d i p o l a r scales of s t r o n g - w e a k , happy-sad ,

r e f r e s h c d - t i r e d , i n t e r e s t e d - b o r ~ d , e n e r g e t i c - l a z y ,

v i g o r o u s - e x h a u s t e d , a w a k e - s l e e p y , s t i m f a t e d - s e d a t e d , a b l e t o

c o n c e n t r a t e - u n a b l e a n d no feeling o f d i s c ~ ~ f o r t - e x t e n s i v e , No

s i g n i f i c a n t d i f f e r e n c e s were f o u n d f o r t h o s e p s y c h o l o g i c a l

m e a s u r e s t e s t e d before a n d a f t e r t h e c o n t r o l c o n d i t i o n . 4

p a r t i t i o n e d F test for w l t i p l e c a ~ p a r i s o n s i n d i c a t e d t h a t it

was t h e b e f ose-af t es c o m b i n a t i o n w h i c h was s i g n i f i c a n t l y

d i f f e r e n t fp<O, 05) . P e a r s o n c o r r e l a t i o n c o e f f i c i e n t s were o b t a i n e d on e a c h o f

t h e t h r e e i w a s a r e t p e n t t r i a l s done o n CPF, contrast s e n s i t i v i t y

and acco~iamoda t ive reslcnse a t each measurement o c c a s i o n . Pearson

c o r r e l a t i o n c o ~ f f i c i e n t s showed s t r o n g r e l a t i c m s h i p s o f e a c h

measurement t r i a l with t h e o t h e r , w i t h r v a l u e s ranging f rom

0.82 t o Q,94 f o r CFP; 0.94 t o D,99 f o r c o n t r a s t s e n s i t i v i t y ; and

0.62 t o 8-89 f o r a c c o r m o d a t i v e r e s p o n s e .

Whether p h y s i c a l s y ~ ~ p t o m s were p r e s e n t before o r a f t e r t h e

e x p e r i m e n t a l c o n d i t i o n o r a f t e r rest was a n a l y z e d a c c o r d i n g t o

E r i e d t a a n ' s test of s i g n i f i c a n c e ( B r a d l e y , 7968). T h e h e a l t h

s y m f t o m s of e y e i r r i t a t i o n a n d h e a v y e y e l i d s B e r e f o u n d t o

d i f fez s i g n i f i c a a t ly a f t e r t h e e x p e r i ~ e n t as colapared t o before.

~ h ' e c o ~ p l a i n t o f i r r i t a t e d e y e s o c c u r r e d i n 75% o f t h e s u b j e c t s

after the VDT s e s s i o n v h i l e c o m ~ l a i n t s of h e a v y eyef i d s , b l u r r e d

vision a n d b u r n i n g e y e s accurred i n 58.3%- T o 47,746 white c o l o u r

appea red p i n k i s h , w h i l e 33.3% e x p e r i e n c e d n e c k a c h e s .

In t fie p o s t - e x p e r i m e n t a l c o n d i t i o n , emironfaental Var i ab l e s

wefe a s s e s s e d . S e v e n t y - f i v e p e r c e n t of t h e s u b j e c t s f o u n d the

s e a t i n g u n c o s f o r t a b l e and t h e r o o @ lighting t o o bright. For 5 0 %

t h e rooa was s t u f f y , 41.7% t h o u g h t t h e room was noisy a n d 3 3 - 3 s

c o m p l a i n e d t h a t t h e ~oolg was too hot, However vhen the s a t i n g s

o f these e n v i r o n l t t e n t a l v a r i a b l e s done a f t e r a two h o u r VDT

s e s s i o n were c o a p a r e d w i t h r a t i n g s d o n e by t w e n t y o t h e r s u b j e c t s

before w o r k i n g i u t h e roo@, no s i g n i f i c a n t d i f f e r e n c e s %ere

i d s n t i f i e d us ir .g a 3ann-#hi tneg T i a n a l y s i s o f i n d e p e n d e n t

measures &<Om 05) .

P i n a l l y , V D T p a r a n t e t e r s were e v a l u a t e d . To 58.3% of t h e

s u k j f c t s , g lare cn t h e s c r e e n was a probler t l , The h e i g h t o f the

k e y b o a r d a n d t h e d i s t r a c t i o n cf b r i g h t lights a b o v e o r b e h i n d

the YDT were i n d i c a t e d b y 50% of t h e s u b j e c t s t o be b o t h e r s o m e .

f o r 41.7% t h e d i s t a n c e t o t h e k e y b o a r d was n o t o p t i m a l . w h i l e f o r

33, 3% t h e b r i g h t n e s s cf the s c r e e n a n d a h i g h p i t c h e d n o i s e were

bothersome,

Discuss i o n ------

Exposure t o two h o u r s of i n t e n s i v e work a t a v i d e o d i s p l a y

t e r t a i n a l a p p e a r s to have a n e f f e c t on t h e rrisnal f u n c t i o n

p a r a m e t e r s of cr i t ical f l i c k e r f u s i o n , c o n t r a s t s e n s i t i v i t y a n d

ilcco.ntrmodative f a c i l i t y . In a l l i n s t a n c e s B e a s u r e s shoved a

decse ~ e n t i n •’ u n c t i o n a f t e r t h e e x p e r i n t e n t a l c o n d i t i o n , Recovery

was e v i d e n t t o some extent i n a l l o f t h e v i s u a l measures after

15 i n i n u t e s rest, C h a a g e s i n t h e p s y c h o l o g i c a l f a t i g u e d i p o l a r

scale a l s o i n d i c a t r d tbat the e x ~ e r i ~ n t a l s e s s i o n was

s u b j e c t i v e l y more f a t i g u i n g . Host d i p o l a r ~ s y c h o l o g i c a l t f a t i g u e

i n d i c a t o r s i n c r e a s e d i n degree i n t h e d i r e c t i o n s f t h e fatigue

v a r i a b l e a f t e r t h e e x p e r i m e n t c c ~ p a r e d w i t h b e f o r e .

The a v e r a g e d r o p i n CPP o f 1 - 9 c p s a•’ ter t h e two-hour

experirtrental s i e s s i c n was s a t a l l , b u t c o n s i s t e n t i n i t s t r e n d ,

Eartley a n d S i x o n s o a (3976) r e p o r t f i n d i n g s o f a g r e a t e r d r u g i r :

CPF o f 4-6 to 5,4 c p s in i n t e n s e close work after a full work

d a y , r a t h e r : t h a n a twc hour work p e r i o d , 3L s i g n i f i c a n t c h a n g e i n

c o n t r a s t t h r e s h o l d a t 40 c y c k s / l lcra was f onnd w h e r e an a v e r a g e

c c n t r a s t r e a d i n g of 90,8 b e f o r e t h e s e s s i o n i n c r e a s e d t o 102,f:

a f t e r , Roo 11982) i n c c m p a r i s c n f o u n d no c o n s i s t e n t t r e n d i n t h e

t o t a l c o n t r a s t t h r e s h o l d f u o c t i o n curve, However, analyses 05

changes in i n d i v i d u a l f r e q u r a c i ~ s were not pxesented. The d r o p

i n accomraoda t ive f a c i l i t y of 1 - 3 cycles %hen viewing c h a r t s a t

two d i f f e r e n t d i s t a n c e s , a g r e e s w i t h t h e findings of a decrease

i n accoptaodatiue f a c i l i t y b y Hourant e t a l , ( 1 9 0 1 ) .

Accommodative r e s p o n s e showed a sligbt c h a n g e of - 3 5

d i o g t e r s . Yet b e c a u s e cf i n d i v i d a a l v a r i a t i o n a n y c o n s i s t e n t

effect was n o t e v i d e n t , Hovevec H c f l e r et c x l . {1975) with o n l y a

change of .25 d i o p t e r s , conemented on its g o t e n t i a l s i g n i f i c a n c e

t o a p p r o p r i a t e v i s i o n , T h e t a s k of a c c a a a o d a t i v e response was

-the itnost d i f f i c t i l t t o assess as s u b j e c t s found that f o c u s s i n g on

t h e t a r g e t p i n w h i l e m a i n t a i n i n g a clear image of t h e S n e l l e n

c h a r t a d i f f i c u l t g r o c e s s .

Liati tat iorts t o this e x p e r i n t e n t %ere e v i d e n t , T h e t a s k w h i c h

t h e subject p e r f o r a e d c o u l d b e made more s t a n d a r d i z e d s o t h a t

t h e r a t e o f work c o u l d be m o n i t c r e d , F o r t h e c o n t r o l group,

l i k e w i s e , ~ o n i t o r i n g work s u c h a s t p p e ~ r i t i n g i n t h e same room

e n v i r o a f a e n t ~ o u l d h a v e tcen beneficial i n crder t o assess

u h e t h e s p s y c h o r o t u s : f a t i g u e was e v i d e n t f r o a t h e t y ~ i n g e l e t t l e n t

of VDT work. The tirae d e l a y between t h e c o a i p l e t i o n of t h e

e x p e r i m e n t a l t a s k a n d visual function f a e a s u r e a e n t Bay bave

promoted some r e c o v e r y . A t issue is what a decrement i n GFF

r e a l l y i n d i c a t e s . The descriptive terra " v i s u a l f a t i g u e M is

r e l a t i v e l y ~ e a n i n g l e s s . Subjects a a i n t a i n e d f i x e d d i s t a n c e s f rcm

t h e i n s t r u m e n t s w i t h o u t a n y m e c h a n i c a l a s s i s t a n c e , S l i g R t

c h a n g e s i n v i e v i n g d i s t a a c e s rtidy affect t h e feslalts so~ewhat ,

F i n a l l y , c o m p l e t e a n a l y s i s o f t h e c o n t r a s t s e n s i t i v i t y f u n c t i o n

w o u l d r e q u i r e use of egu ipnaen t w i t h a more e n c o m p a s s i n g r a n g e of

c o n t r a s t . T h i s would p e r m i t t h e p l o t t i n g of a c o n t r a s t threshold

f u n c t i o n c u r v e v h i c h wculd @ore c o n c l u s i v e l y i n d i c a t e w h i c h

f r e q u e n c i e s of s i n u s o i d a l wave g r a t i n g s were a f f e c t e d .

B c c o r d i n g t o t h e current l i t e r a t u r e , the q u e s t i o n of

w h e t h e r acute c h a n g e s i n v i s u a l f u n c t i o n p r o m t e any d e g r a d a t i o n

i n p e r a a n e n t v i s u a l f u n c t i o n i n g resain E u n r e s o l v e d . However t h e

fact t h a t v i s u a l f u n c t i o n changes were e v i d e n t a f t e r two h o u r s

of ? h ~ work and not i n a t-lso hour f ree p e r i o d in - r rc lv ing r e a d i n g

and rest, i n d i c a t e s t h a t a tvc-hour u n i n t e r r u p t e d period of

i n t e n $ @ v i s u a l work u s i n g the VD? may b e too long. I n c o m p l e t e

recovery after 15 minutes rest in s o w i n d i v i d u a l s a l so prontotes

this c o n c l u s i o n . I n light of these f i n d i n g s , a s h o r t e r v o r k

period, ~ o s s i f r r l y of a one-hour ~ a x i m u t n of V D T m r k f o l l o w e d b y a

f o r m a l rest break would be more a p p r o p r i a t e , The encouragement

of i n f o r a a l rest b r e a k s a l s c may h e l p t o a l l e v i a t e a n y undue

v i s u a l stress, Such s l i g h t changes i n v i s u a l f u n c t i o n ntay 'hinder

t h e opera tors* v i s u a l coaafort d u r i n g a VDT task, A c c o m o d a t i v e

function changes e s ~ e c i a l l y would affect the smb ject* s ability

t o f o c u s cn the material. I t can be e x p e c t e d t h a t a f t e r a longer

VDT work period ( t h a t t y p i c a 1 l . y found f o r a n average Y D T

operator's work d a y ) there would be a g r e a t e r effect of B D T s o r k

o n v i z u a l f u n c t i o n , Rest b r e a k s m u s t be of s u f f i c i e n t frequency

aud d u r a t i c n to promote r e c o v e r y ,

F u r t h e r research into t k e nore p e r m a n e n t f e p e s c u s s i o n s of

acute v i s u a l f u n c t i o n changes is r e c m n e n d e d , C h a n g e s i a

a c c o a r a o d a t i v e response may Le particularly f e l e v a n t a s i t showed

t h e least afflount of r e c o v e r y o n t h e average, D e l i n e a t i n g factors

t h a t may ease v i s u a l stress snch as l i g h t i n g and g l a r e c o n t r o l

a a d t h e optiaal spacing of rest b r e a k s is a f u r t h e r

r e c o m @ e n d a t i o n , A g o t e n t i a l a i d i n t h i s regard is t h e u s e of

a p p r o p r i a t e specialized p ~ e s c r i p t i o n glasses w h i c h may ease t h e

s t r a i n of a c c a ~ a o d a t i s e work.

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54, X. 8 - ?I, Human P a c t o r s 05 V c r k s t a t i o n s w i t h D i s p l a y Terminals, fleport 6320-6102-0. S a n Jose, C a l i f o f n i a , 7 978,

5 5 , K r i v o h l a v y , J , , K o d a t , V,, C i z e k , P, V i s u a l efficiency and fatigue d u r i n g t h e a f t e r n o o n s h i f t . E r g o n o m i c s 12: 335-740, 1 9 6 9 ,

56. K r u e y e r , B . O p t h a f l l t o l c g i c a l aspects of work w i t h d i s p l a y w o r k - s t a t i o n s , f n E,Grand j e a n a n d E , V i g l i a n i {Eds ) E r g o n o m i c A s p e c t s of V i s u a l D i s p l a y T e r n t l n a f s , London: T a y l c r E F r a n c i s Ltd: 3 1-40, 19813,

57, L a b o r O c c u p a t i o n a l H e a l t h P rog tan t , T h e H a z a r d s of Clerical. Work, J u l y , 7980,

58, L a b o u r C a n l d a , I n the C h i p s : O p p o r t u n i t i e s P e o p l e P a r t n e r s h i p s . R e ~ o r t of the Labour C a n a d a T a s k Force on B i c r o - e l e c t r o n i c s a n d Esfloyme.rtt, 1982,

59, L a ~ b e r t , C. V i s u a l Display Terrttinals, C a n a d i a n Union o f P u b l i c Employees , 1 9 8 0 ,

6 0 , Laubli, T h , , B u n t i n g , H., G r a n d j e a n , E. V i s u a l i m p a i r m e n t s i n V C U operators r e l a t e d t o e n v i r o n a e n t a l c o n d i t i o n s , In 3 . G r a n d j e a n a n d E. V i g l i a n i ( E d s ) E r g o n o m i c Aspect of V i s u a l D i s p l a y T e r m i n a l s , London: T a y l o r 8 F r a n c i s E t d : 85-94, 1980.

S t . L a u b l i , T h . , H u n t i n g , W,, Grandjean, E, P o s t u r a l a n d v i s u a l l o a d s a t VDT w o r k ~ l a c e s 11, L i g h t i n g c o n d i t i o n s d a d v i s u a l i m p a i r m e n t s , E r g o n o m i c s 24: 9 3 3 - 9 4 4 , 1981 ,

02, Lin, 3 . C, H e a l t h aspcts of: r ad io a n d microwave r a d i a t i o n , journal o f E m i r a n a e n t a l Pa tho f ogy axid T o x i c 0 fogy 2 ( 6 ) : 1413-1432, 1981,

6 3 , Love, 3, H e a l t h h a z a r d s of cf f i ce work, Rontea and H e a l t h May/June: 18-22, 1978.

64. BacAr thu r , 1-0. Birds , Bls a n d C B T s . ICL T e c h n i c a l J o u r n a l 2 ( 2 ) : lQ7-1741, 1980,

65. HacKay, C. P e o p l e and V C U s , S p e c t r u m 177: 9- 11, 1982. 1 6 6 . PIcGratfi, J, G , 1981. H e a l t h , s a f e t y a n d e r g o n o m i c a s p e c t s o f

v i s u a l d i s p l a y u n i t s , B e d i c a l B u l l e t i n 411 11) 2 79-112, 1981,

67, itfcPhee, D. I. S o v i e t and eastern European r e s e a r c h o n b i o l o g i c a l e f f e c t s of microwave r a d i a t i o n . P r o c e e d i n g s o f t h e I . E . E . E . 6 8 ( l ) : 84-91, 1980.

5 8 , Banuel , T. R o l d i n g c o a p u t e r t e r a i n a l s t o human needs , E l e c t r o n i c s Sf: 97- 108, 1982 ,

69, Eloss, C , E , e t al, A R e p c r t on E l e c t r o l a a g n e t i c R a d i a t i o n Surveys o f Y i d e o D l s ~ h y T e r ~ i a a l s , C i n c i n n a t i : U;S. g a t i o n a l I n s t i t u t e f o r Occupa t i o n a f S a f e t y and H e a l t h , pub. no, 78-129, 1977,

70, Houran t , D o B., Lakshmanan, R, , C h a n t a d i s a l , 8 , V i s u a l f a t i g u e a n d c a t h o d e r ay t u b e d i s p l a y t e r m i n a l s , Human F a c t o r s 23: 529-540, 5981,

71, B u r r a y , W. E*, Boss, 8. E , , P a r r , W. H,, Cox, C, A r a d i a t i o n and i n d u s t r i a l hygiene s u r v e y of v i d e o d i s p l a y terminal o p e r a t i o n s , Buman F a c t o r s 2 3 [4) : 413-420, 1981,

72. %eu S c i e n t i s t . T i g h t r u l e s f o r s c r e e n s i n Horvay c o u l d set p r e c e d e n t . Yo1 9 ( 1 2 5 2 ) : 334, 1981.

73, O l i s . b i f s h i , J, B , , McElroy, F.E. Fundamen ta l s of I n d u s t r i a l Hygiene. Chicago: N a t i c n a l S a f e t y C o u n c i l , 1971.

74, O s t b e r g , 0. CRTS pose h e a l t h probfetrts f o r o p e r a t o r s , I n t e r n a t i c n a l d o u r n a l of O c c u p a t i o n a l H e a l t h and S a f e t y 24, 1975,

75, O s t b e r g , 0. O f f i c e p a r t i c i p a t i o n , w o f k ~ l a c e design c o n s i d e r a t i o n s a n d t b ~ r e t l u c t i o r , of v i s u a l stress. P a p e r r e a d a t the M A T O Odvanced S t u d y I n s t i t u t e on Man-compnter i n t e r a c t i o n , Greece, Septeaber , 7976,

76. O s t b e r g , 8. Revielbl of v i s u a l s t r a i n , v i t h special reference

t o m i c r o i ~ a y e r e a d i n g , P a p e r r e a d a t t h e I n t e r n a t i o n a l # i c r o g r a p h i c s C o n g r e s s , S t o c k h o l m , September, 1976 ,

77 . O ~ s t b e r g , 0, T o w a r d s s t a s l d a r d s a s d T L V s f o r v i s u a l w o r k Ie B, Te-nrjrot,h {Ed) C u r r e n t concepts i n E r g o g t h a l l ~ o l o g y , Stockbolna , 1978 ,

5 I

B 78, Ostbecg, 0. The h e a l t h debate, P a p e r d e l i v e r e d a t t k e Second I n t e r n a t i o n a l Vord P r o c e s s i n g C c n v e a t i o a , Hay, 1979,

79 , O s t b e r g , O,, Powell, J , , B l o r ~ k v i s t , A , L a s e r o p t o m e t r y i n i

a s s e s s i w n t cf v i s n a l f a t i g u e i n VDU o p e r a t o r s . Sweden: C e p t , af Runan Work S c i e n c e s : 11-15, 1 9 7 9 ,

80. O s t b e r g , 0. Accommodation a n d v i s u a l f a t i g u e i n d i s p l a y work, I n E-Grand jean and E, V i g l i a n i [ E d s ) E r g o n o m i c Aspects of V i s u a l Display T e r ~ i n a l s , London: T a y l o r E F r a n c i s Ltd: 43-52, 1980,

8 1 , Purdnam, J.T, B Revielg of the L i t e r a t u r e o n H e a l t h H a z a r d s of Video D i s p l a y Ternaiaals, H a m i l t ~ ~ : C a n a d i a n C e n t r e f o r O c c u p a t i o n a l H e a l t h a n d S a f e t y , O c t o b e r , '1980.

82. S e p , P,, Moyer, J,J,, Degoumois, A. Visua l , p r o b l e m s o f o p e r a t o r s u s i n g d i s p l a y screens. S e n i a a r h e l d by t h e I n d u s t r i a l H e d i c i n e a n d Ergononay U n i t of the I n s t i t u t e of S o c i a l a n d P r e v e n t i v e i l s d i c i a e , Geaova, December, 1977 ,

8 3 . Bey, Po, #eyer, J, J, V i s u a l i a p a i r i u e n t s a n d t h e i r o b j e c t i v e correlates, I n E , G r a n d ~ e a n ant i 3, v i g l i a n i (Eds j Efgono ia ic A s p e c t s o f V i s u a l D i s p l a y T e r m i n a l s , London: T a y l o r G F r a n c i s Ltd: 77-84, 1980-

34. Rosenbaum, L, H e a l t h effects of v i d e o d i s p l a y t e r m i n a l s : t h e n o n r a a i a t ion p r o b l e m s , W e a l t h Advocacy Unit, Dept. of P u b 1 i c H e a l t h , A p r i l , 1980 ,

8 5 , Rupp, B,A. 3 i s u a l Eisplay S t a n d a r d s ; a Review o f Issues. S a n Jose, C a l i f o r n i a : I n t e r n a t i o n a l B a s i n e s s E a c h i n e s , 1979,

86, S a i t o , f l . , Tanaka, 2,. Cshima, 3, E y e s t r a i n i n i n s p e c t i o n a n d clerical w o r k e r s , E f g o n o m i c s 2 Y : 161-173, 1981.

87. S a u t e r , S,Z. e t al. Job a n d health i ~ p l i c a t i o n s of VDT u s e : i n i t i a l results of t h e H i s c o n s i n - I I O S H s t u d y , C o m m u n i c a t i c n s of t h e ACB 26 (4) 2 2434-294, 198 3,

88, S c i p u e s t . E y e s t r a i n , December, 1981,

8 9 . S e k u l e r , B., Hufvanny , E, 29/20 is n o t enough, A ~ e r i c a n Health: 5 0 - 5 6 , 1982*

5 90, Sharit, J., S a l v e n d y , G, o c c u ~ a t i o n a l Stress: r e v i e w a n d

r e a p p r a i s a l , H u m a n F a c t e c s 24: 129-162, 1982, d

9 1, S ~ l i t h , A .B ,, r a n a k a , S , , Hafpes i n , R . , B i c h a r d s , R. C. R e p o r t o f a c r o s s - s e c t i o n a l s u r v e y of VDT u s e r s a t t h e B a l t i m o r e Sun. C i n c i n n a t i : H a t i o n a l I n s t i t u t e for O c c u p a t i o n a l S a f e t y a n d H e a l t h , 1982.

92, Smith, B . J . A r e v i e w of N I O S H p s y c h o l o g i c a l stress r e s e a r c h 1977, fn Proceedings cf C c n f e r e n c e o n O c c u p a t i o n a l . S t r e s s , C i n c i n n a t i : Hat i n n a l I n s t i t u t e for Occupat i cna l S a f e t y a n d H e a l t h pub, 78-156, f larcfi 1978,

9 3 , S a i t h , &,J., Cohen, B.J., S t a ~ ~ e s j o h n Jr., L , @ . An i n v e s t i g a t i o n of h e a l t h c o r ~ p l a i n t s a n d j o b stress i n v i d e o d i s p l a y o g e r a t i o n s , Humaa F a c t o r s 2 3 14) : 387-400, 198 1.

94. S ~ l i t h , id ,J , A r e v i e w of fi t e r a t u r e r e l a t i n g t o v i s u a l f a t i g u e . I n P r o c e e d i n g s of t h e Huaan F a c t o r s S o c i e t y 2 3 r d Annua l H e e t i n g , 362-366, 1 9 7 9 .

95, S p e n g l e r , J,C., S e x t o n , 8 . Xndoor a i l : p o l l u t i o n : a p u b l i c health p e r s p e c t i v e , Science 221 (4605) : 9-17, 1983 ;

9 6 . SPSS, S t a t i s t i c a l P a c k a g e l o r t h e S o c i a l S c i e n c e s , 2nd Ed, I,B, Nie e t a l , ( E d s ) Hew York: E9cGran-Hill Book Co,, 1970.

37, S P s S , SPSS Update 7-4, New P r o c e d u r e s and F a c i i i t i e s f o r E e l e a s e s 7-9, C.H. B u l l a n d N O H . Nie (Eds) N e w York: f l c G r a w - R i l l Book Co, , 1981 ,

98. S tae tmer john , L,W,, S m i t h , H.J,, Cohen, B . G , F , E v a l u a t i o n o f work s t a t i o n d e s i g n f a c t o r s in V D T o ~ e r a t i o n s , S u m n F a c t o r s 2 3 (4) @0 1-4 7 2 , 1981,

99, S t e r l i n g , T . D , , Kobayash i , I).f4, E x p o s u r e t o p o l l u t a n t s i n e n c l o s e 4 * * l i v i n g s p a c ~ s * ~ . E n v i f c n m e n t a l R e s e a r c h 13: 1-35, 1977 ,

100. Stewart, T.F. M. E y e s t r a i n a n d v i s u a l d i s p l a y u n i t s : a r e v i e u . D i s ~ l a y s A p r i l , 1979.

10 1. Stearart, T.E,fYI, P r a c t i c a l e x p e r i e n c e s i n s o l v i n g VCU e r g o n o m i c s pfoblenrs. I n 3, G r a u d j e a n and 3. V i g l i a n i (Eds) E f gonoraic Aspects of V i s u a l D i s p l a y T e r m i n a l s .

London: T a y l o r E F r a n c i s Ltd: 233-240, 1980.

102. Stone, P.T . I s s u e s i n v i s i o n a n d l i g h t i n g f o r u s e r s of VDTs- I n the HUSWT R e s e a r c h Group , H e a l t h H a z a r d s o f V D U s ? II- S o a e S o l u t i o n s t o t h e C u m o n P r o b l e m s ,

Loughborough: Loughbsrougfi U n i v e r s i t y o f Technology, March 1981,

1 0 3 , !Ierrana, T, , Rerlrizzi, P,, G i u d i s i , El E l e c t r o ~ a g n e t i c radiations e ~ e l i t t e d b y v i s u a l d i s p l a y u n i t s . In F, G r a n d jean a n d E, V i g l i a n i (Eds) ~ r g o n o l c i c Aspects of Visual D i s p l a y T e r m i n a l s , London: Taylor E F r a n c i s Ztd: 13-33, 1980.

104. Thomas, J.P. S p a t i a l r e s o l u t i o n a n d s p a t i a l i n t e r a c t i o n , I n E.C. Car te re t t e and BOP. F r i e d ~ a n {Eds) Handbook o f P e r c e p t i o n , Volulne V . S e e i n g , Academy P r e s s , Neu P o r k , 1 9 7 5 ,

1135. The Province. Computer t e r m i n a l pregnancy hazards s t u d y d e ~ a n d e d . A p r i l 13, 1982 ,

1 0 6 . I j o n n , 8, W, R e p o r t of fac ia l , r a s h e s aEcng Y f l a o p e r a t o r s i n Nurvay. I n t h e IIUSAY! R e s e a r c h Group, H e a l t h H a z a r d s Of V D U s 1. Loughborough: L o u g h b o r o u g h University o f Technobogy , D e c e ~ h e r , 1980,

707 . Turner, P. J, V i s u a l environment of c c m p u t e r t e r m i n a l s , A u s t . a. O ~ t c m . 62(6): 238-243, 1979.

108 . U,S, Dept . of H e a l t h and Human S e r v i c e s . An E v a l u a t i o n of R a d i a t i o n E m i s s i o n f rom V i d e o D i s f l a y T e r m i n a l s , B a r y l and : B u r e a u of R a d i o l o g i c a l H e a l t h , 1981 ,

109, Vetter, H. Health H a z a r d s A s s o c i a t e d g i t h t h e Visual Cisp lay U n i t s , 50 p a g e s , 3379.

110- iJarr, A . O p e r a t i n g V D U s z Hork o r g a n i z a t i o n a n d s u b j e c t i v e e f f e c t s o n o p e r a t o r h e a l t h and p s y c h o l o g y , J, P h y s - E l S c i , I n s t r u m . 1 : 3 - 4 0 , 1981 .

1 1 1. Ueiss, &.3. , P e t e x s e n , R-C. E L e c t r o ~ a g n e t i c r a d i a t i o n e m i t t e d froin v i d e o c o m p u t e r t e r m i n a l s . Ba. fnd, Hyg- Bssoc, J, 40: 300-305, 1979,

11 2. Woo, G, P a p e r g i v e n a t "Li ving w i t h VDTstr c o n f e r e n c e . T o r o n t o : Viser C o n s u l t a n t s , O c t o b e r , 1982.

1 1 3 . Rord P r o c e s s i n g klorld. Do CPZs cause E y e s t r a i n ? p. 58, 1976,

114. W r i g h t , D o D e s i g n i n g t ~ r m i n a l s f o r t h e human f a c t o r , C a n a d i a n Da t a s y s t e n t s lY:3?-4Y, 7982.

115 , Zaret, H. MI Cataracts f o l l o w i n g u s e of c a t h o d e r a y t u b e d i s i p l a p s . P r o c e e d i n g s of I n t e r n a t i c n a f Spapos inm o f E l e c t r o m a g n e t i c -Waves a n d B i o l o g y , F r a n c e , J u n e / J u l y 1988,

- 1

,

116. Z a r e t , Pl.3. C a t a r a c t s ?and v i s u a l d i s p l a y u n i t s . Tn t h e H U S A T Researcb Graup, i iealth flazards of VCUs? 1, Loughboraugh: Loughbcrough D n i v e r s i t y of Technology, Cecember 1980.

APEE WDIXES

r

Appendix A: The idark E a v i r o n n r e l ~ t S u r v e y Q u e s t i o n n a i r e

I

INSTRUCTIONS: Please answer the following survey by blacken- , ing the most appropriete circle(s) as shown at left. Al l information I given wil l be confidential and anonymous. This SUNey is being used - t o determine the quality of your work place. Begin wi th #1 , following the example. I

111

NCS TC.~. opt^ E 0s 10603 321 . PAGE 1. Dm

STATUS m OSingle 0 Married OSeparated ODivorced Owidowed 0 Other

= i I 1

PRCSENT JOB TITLE (PI.... Pmtl

MONTH DAY YEAR m

~.ooooooo...oooooooooooo DO NOT WRITE HERE

0 Male

0 Female

ADDRESSOF PRESENTJOB

,

3. EMPLOYMENT I STATUS . 1

003587 = !

0 Full time OPart time

7. NUMBER OF CHILDREN

0 Three 0 Four or

- IN THE QUESTIONS THAT FOLLOW CHOOSE ONE BEST ANSWER UNLESS OTHERWISE INDICATED.

9. Are you the primary source of income in your household?

Yes 0 N o 0

10. Were you laid off or fired: a) i n the past 6 months? Yes 0 No 0 b) i n the past year? Yes 0 N o 0

1 1 . On the average how many hours a day do you work?

0 l r o 2 O 3 t o 4 O 5 t o 6 0 7 to 8 0 9 to 10 OOver 10

- ,

8. EDUCATION - $ ()Grade 9 or less r $ o ~ o m e high school I OHigh school (completed/ o ~ u n i o r college - 1: OTechnical training m :I 0 Some college - : I OUndergraduate college degree - :! 0 G.raduate school :1

- :I 12. How many days a week do you usually work? ,

0 1 day 0 2 days 0 3 days 0 4 1 :: 0 5 days 0 6 days 0 7 days - :1 - :I

13. How many days have you been absent from :: work during the past 6 months? (Do not include - ;: vacation days). - ::

ONone 07 to 2 0 3 to 5 - ;I O f i t 0 8 0 9 t o 1 2 O M o r e t h a n l 2 - 1:-

I

14. I n the past 6 months how many days have - 4 you left during work due to illness? - 2

()None 0 1 1 0 2 0 3 1 0 5 - P 0 6 ro 8-- 0 9 to 12 S M o r e than 12

Blacken the most appropriate circles.

I( - 15. In your job are you able 1: to make decisions on ............ 1 your own? 'I: - I( - 16. Are you free to determine ( 0 how you do yourjob? ... : - : - 17. Can you set the speed at : - which you work? ...... : - : 0 18. Are you able to influence [ - company policies that : r affect your job? ....... : - ( 19. Is your job security good? : - : - : r 20. During the past year, were : - you faced with possible ( r job loss or layoff? (Exclude ( r actual job loss or layoff) : - : r 21. Does your job require you - to work very fast? ..... : - : m 22. Does your job require : m a great deal :-m of concentration? . . . . . . : - : - 23. Is your job monotonous : m or boring? ............ : = : r 24. Does your lob requare you 1: - to exen a lot 0' ........ ( u physical effort? : - : r 25. Are you required to use : awkward work motions? : r u 26. Are co-workers helpful in

( r getting your job done? : - ( 27. Is your supervisor helpful

I( in getting your job done? . . . . . . . . . . . . . 1 =

1, r 28. Are you faced with abuse

1; I or hostility from: I( I a) customers or clients? ........ 1: I b) supervisors?

........ 1: III C) CO-workers? I: 1: - 29. Are there enough people ir

...... ii r your department?

# - fl m 30. Do you remain in one

I m location at work m each day? ............

II 31. I n your primary work area

(that in which you spend the most time) do you feel there is:

a) too little air ........... movement?. 0

b) too much air ............ movement? 0 I

c) lighting too bright? . . . . . . 0

d) lighting too dim?. . . . . . . . 0

. . e) glare on work surfaces? .I 0

f ) unpleasant odors?. . . . . . . g) temperature too cold? . .

h) temperature too hot? . . . . 0

i) air too dry? . . . . . . . . . . . . 0

j) air too moist? . . . . . . . . . . 0

k) air too smoky?. . . . . . . . . I O

I) air too stuffy? . . . . . . . . ..I 0

m) uncomfortable seating? .. 32. What type of

equipment do you " j e (Choose all approp- riate rusponsos):

a) transcriber ...... b) typewriter ...... c) VDTICRT ....... d) laser printer . . . . .

. . . . . e) photocopier

f) mimeograph .... g) adding machine

... or calculator

.... h) telephone(s)

. . . . . . . . . . . i) filing

AGE 2

0

0

0

0

0

0

0

0

0

0

0

0

_O

0

0

0

0

0

0

0

0

4_

CRT. no t o quesiton 34). Are the follo&ng bothersome: I I I a) flickering of screen? . . . 0 0 0

b) brightness of screen? . . 0 0 0

c) height of screen?. . . . . . 0 0 0

d) distance t o screen?. . . . 0 0 0 e) bright lights above

or behind VDTICRT? . . 0 0 0

f) sire of lettering? . . . . . . 0 0 0

g) brightness of letters? . . 0 0 0

h) height of keyboard? . . . 0 0 0

i) distance t o keyboard? . 0 0 0

Yes N o j) Is the keyboard attached? 0 0

34. I s your work area: 0 enclosed 0 not enclosed

35. Can you see a window from your primary work position?

OYes O N o

36. Approximately what distance are you from a window? 0 Less than 5 feet 0 5 to 1 0 feet 0 1 0 to 20 feet 0 Over 20 feet 0 No windows nearby

37. D o the windows open? 0 Yes 0 No 0 Yes, but not allowed

38. On how many sides are there privacy partitions? 0 None OOne 0 Two OThree 0 Four

39. Is your work area lighted by: (Choose all that apply) 0 fluorescent ceiling light 0 fluorescent table light 0 incandescent ceiling light 0 incandescent table light 0 natural window light

I

80. Are you able t o control: Yes No I

a) ceiling lighting 0 0 I

b) air conditioning 0 0 I

c) heating 0 0 d) ventilation 0 0 -

I

I

01. In the past year have you brought I

t o work: Yes N o m

a) extra heater 0 0 .I

b) extra fan 0 0 I

I

02. Do you now or have you ever I

smoked cigarettes? I

0 Yes 0 No - w

a) age started smoking: I

Obeforeage15 0 1 5 t o 2 0 0 2 1 t o 3 0 - 0 3 1 to 40 Oafter age 40 ~l

.I

b) age stopped smoking: II

0 still smoke 0 15 to 20 0 21 to 30- 0 31 to 40 0 after age 40

c) How many cigarettes do you or did you smoke each day on the average?

43. Are you able to smoke a t work? OYes 0 No OYes. but only in designated areas OYes, but not much time to smoke

44. Do you wear corrective lenses at work? 0 No 0 Bifocals 0 Reading glasses 0 Contact lenses 0 Regular glasses

45. H o w many cups of coffee do you drink on the average each day at work?

0 None 0 1 or less 0 2 to 3 0 4 t o 5 0 6 or more

46. H o w many cups of tee do you drink on the average each day at work?

0 None 0 1 or less 0 2 to 3 0 4 t o 5 0 6 or more

07. How often have you had alcoholic beverages in the past 6 months?

0 None 0 Less than once a month 0 1 to 3 times a month 0 1 to 3 times a week 0 4 or more times a week

48. Do you use the following appliances i n your- home? (Choose all that apply)

0 Gas stove OGas heating 0 Electric stove 0 Electric heating OOi l furnace O A i r conditioner

- am

Blacken the most appropriate circles.

49. Have you ever experienced any of the symptoms listed below while at work? (Choose all that apply):

a) headache . . . . . . . . . . . . 0

b) dizziness.. . . . . . . . . . 1 0

c) fatigue.. . . . . . . . . . . . . .

d) sleepiness . . . . . . . . . . . e) nausea . . . . . . . . . . . . . f) skin rashes.. . . . . . . . . g) ringing i n ears . ....... h) nose irritation . . . . . . . . i ) breathing difficulty . . . I O

j) chest pain or tightness. . 0

k) racing heart . . . . . . . . . . 0

I) neck ache.. . . . . . . . . . . 0

m) sore arms, hands or wrists.. . . . . . . . . / o

n) backache . . . . . . . . . . . .

o) blurred vision . . .

p) eye irritation . . . . . . . .

q) split or double ........ vision

r) trouble focusing eyes . . I O s) sore throat or cold

symptoms . . . . . . . . . . . 0

t) nioodiness . . . . . . . . . . .

U) frequent urination . . . . . v) depression . . . . . . . . . . . 0

w) lightheadedness . . . . . . . 0

x) confusion . . . . . . . . . . . . 0

a PAGE 4 ........................ DO NOT WRITE HERE

50. Are you currently taking any of the following medications? (Choose all that apply): . . . .

. . . . . . . . . . . . . a) aspirin..

b) stomach or digestive aids. ......

c) cough, cold or sinus medication. . . . .

d) stimulants (pep pills) . . 0 0

e) prescription medicine. ........... 0 0

f) laxatives.. . . . . . . . . . . . I 0 I 0 g) depressants

. . . . . . . . (e.g., valium).

. . . h) sleep inducing aids

51. Have vou ever been diagnosed by a 6 as having: (choose all that apply)

Ocancer 0 hypertension 0 heart disease 0 diabetes 0 kidney disease 0 liver disease Oasrhma Qdeirnaiiiis 0 allergies Onewous disorders 0 anemia Oglaucorna 0 ulcers 0 cataracts Orespiretory illness Oeye infections

(other than colds)

52. H o w many times have you been to a doctor i n the past 6 months?

ONone OOnce OTwice 0 3 to 4 0 5 to 6 0 7 to 8 OMore than 8

53. Do you have trouble sleeping?

OYes 0 No

54. Have you or your spouse ever experienced: (Choose all that apply)

0 miscarriage Ost t l l birth Ooffspring with birth defect(s) 0 difficulty becoming pregnant

*THANK YOU VERY MUCH* - This work environment survey was developed a t Simon Fraser University and at Columbia University.

@ E . Srarlins. 0. Sterl~na. D. Kobavsshi

Appendix 33: D . O . T . O c c u ~ a t i a a codes

Professioaal j o k categories

A d ~ i n i s t r a t i v e QT staff assistant A u d i t o r E u l l e t i n Edi tor Buyer C l a i m s examiner C o w p n t i n g prograimer Executive, chief, coordinating secretary P i f l d abstracter 'Li Itr a r i an R e ~ c r t e r Seniar d r a f t s a a n S e s v i c e , c o r s p l a i n t s , i n v e s t i g a t i o n Staff or a d n i n i ~ t r a t i v e assistant S t a t i s t i c i a n

Dot Code

159 160 132 162 168 007 189 119 100 131 0317 1 6 8 16 9 020

Cle r i ca l job ca tey cr ies D o t . Code

A35 e x p e d i t ~ s A c c s u a t , b i l l i n g c l e r k Accounting Bond, reserve c l e r k C l a i ~ s a p p r o v e r Clerk ( u n c l a s s i f i e d ) Clerk-t y p i s t Coder Collector G o aputer o p e r a t o r C o ~ p u t i n g { u n s ~ e c i f i c e d ) Customer s e r v i c e , a c c o u n t r e p r e s e n t a t i v e Data c o n t r o l F i l e clerk Gate, t i c k e t c l e r k In•’ c r n a t i o n a n d a e s s a g e d i s t r i b u t i o n I n t e r ~ a r k e t t r a d i n g systea operator Keypunch L e g a l secretary B a i l c l e r k E e d i c a l secretary Messenger H i s c e l l a n e o u s o f f ice m a c h i n e s o f f s e t , mirtteo m a c h i n e o p e r a t o r Page R e c e p t i o n , a p p o i n t s e a t s c l e r k R e g i s t r a t i o n c l e r k Secretaries { u n c l a s s i f i e d ) S e n i o r clerk S t a S i s t i c a l clerk Stacker Statistics 1 ty ~ i s t S t o c k e x c h a n g e e m p l o y e e s S w i t c h b o a r d operator T e l ~ ~ h o I i e o p e r a t o r T u b e c l e r k , can boy Typist f u n c l a s s i f i e d ) vDn/c\nT X e r o x m a c h i n e o p e r a t o r

a p p e n d i x C: Experimental Ques t ionna ires

Date- -_--------___ Ti ate _ ------------ Ty pe of corrective lenses ----- --- Rou iuany c u p s of coffee have p u hail today? --a_------

flow any cups of tea have you had today? ----------- gave you eatelz a snack or seal i n the last 2 hours? - 5rttoking sta t u s , aevec- --- - for Ber -------- urren t

Ron &any cigarettes have you snoked today? --- A t the atoreent are you suffering any visual, rrruscnl~skeletal

or any other type 02 h e a l t h symptoa? P l e a s e s p e z i f y ,

- .-

P l e a s e nark t h e point on t fie scale a p ~ r o p r i a k e to your

present sood. e ,g , P o d ,,-----, / -,-,,,----- bad

s t r o n g , - ----- wea k

r ela xed ------------- tense

~~PPY------------------- s3 d

r efres bed ----- t i r e d

interested -------------------- b r e d

energetic -------,----,-- l a z y

vrgorous - I----

ex ha us t e d

e x h i l a r a t e d ,,,,,,,,,,------ angry

------ i n e f f i c e n t

no f e e l i n g of discontfort - extens i v e

listed belou o c c u r r e d during t h e test c o n d i t i o n ,

m n e

White a p p e a r s another color

Burning eyes

j l r r i ta ted eyes

Heavy e y e l i d s

See ing s p a r k s before eyes

T w i t c h i n g e ye1 ids

Blurred vision

Headache

g e c k stiffness or a c h e

S h o u l d e r w i n

A r la s o r e n e s s

grist , hand stiffaess

Backache

Li gbt h e a d n e s s

'Dizziaess

sf i g h t

If any of these s y ~ ~ p t o m s were present before t h e experiraent

p l e a s e put: an asterisk [*) before t h e a p p r o p r i a t e syarptom,

Hental status; Please &ark the p o i n t o n t h e scale appropriate

Did you notice any problea w i t h

v a r i a b l e s ? . none

Uncwfortab Ze seating -- R o o ~ lighting too

Noise

S t u f f i n e s s of the

Boo@ too h o t

Room too cold

Drafty room

t h e f orlowing e n v i r o n n e n t a l

slight aoderatc sevefe

i i l A i r too dry

Bad odors n o t i c a b l e ---- ---We- ------- ------

# h i h working p i t h the BDT d i d you have any p r o b l e ~ t s w i t h t h e

following paranteters?

F l i c k e r i n g of screen

Glare on t h e screen

Brigh t n e s s of the screen

Height of screen

D i s t a n c e to screen

Bright l i g h t i n g

Size sf l e t t e r i n g

Distance bet wee^ l i n e s

B r i g h t n e s s of lettering

Height of keyboard

D i s t a ~ c e to keyboard

High p i t c h e d VDT n o i s

Heat fro& the VDT

none slight severe

White appears awl; her co lo r --- ------- -We--

f3usning eyes -- ---- - ----- Irritated eyes ---- ------ ------- ------ Beavy e y e l i d s ---- ------- ------ Seeing sparks before eyes ----- ------ ----- ---- -- T u i t c h i n g eyelids

B f urred v i s i o n

Headache

B e c k s t i f f n e s s o r ache

S h o u l d e r pain

A r a t sozeness

grist, hand stiffness

Bac kac he

Light headness

Di z zi ness

P h a s e nark the point on

--- ------ ------- ----- ---- -- ---- ------

----- ------ ------ ----- t h e s c a li; a p p r o p r i a t e t o your