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~ _ ~ Contact Lens and An terior Eye (2000 ) 23 , 142-176@ 2000 British Contact Lens Associationwww.nature.com/clae

Abstracts of the24th BCLA Annual Clinical ConferenceBirm ingham 2000W H I C H R E FR A C TI V E P R O C E D U R E S W I L L S U R V I V E I N T H E N E W M I L L E N N I U M ?M McDonald

Th e n e w m i l l e n n iu m h a s b e g u n , a n d t h e r e i s n o d o u b tt h a t e x c i m e r l a s e r s u rg e ry w i ll c o n t i n u e t o d o m i n a t e o u rf ie ld fo r severa l yea rs to com e. I t wil l have to shar e th es tage , however , wi th severa l o ther modal i t i es .I n t r a c o rn e a l r i n g s e g m e n t s ( Int a c s) f o r t h e t r e a t m e n to f l o w d e g re e s o f m y o p i a h a s o b t a i n e d a p p rov a l in t h eUni ted S ta tes . The c l in ica l t r i a l s da ta a re impress ive ,wi th 73% gre a te r tha n o r equa l to 20 /20 , 81% gre a te rthan o r equa l 20 /25 , a nd 97% gre a te r to o r equa l to 20 /40 uncorrec ted a t 24 mon ths pos toop in US Phase I I(n=62) . The revers ib i l i ty and rap id re tu rn o f exce l len tb e s t c o r r e c t e d a n d u n c o r r e c t e d v i s i o n a r e b i g a d v a n -tages . A smal l bu t def in i t e p iece o f the re f rac t ive su rg eryp ie wil l be se rved by In tacs , appea l ing to tho se pa t i en t swho t reasu re rev ers ib i l ity above a ll .Gel in jec t ion ad jus tab le kera top las ty , under deve lop-m e n t b y D r s G a b r i e l S i m o n a n d J e a n M a r i e P a rd , i sb a s e d o n t h e s a m e p r i nc i p le a s t h e i n t r a c o rn e a l r i n gs e g m e n t s . S e v e ra l c h a l l e n g e s m u s t b e a d d re s s e d : t h es u r g e o n d o e s n o t e x a c t l y k n o w h o w m u c h g e l i sin ser ted ( there i s a lways some loss du r ing inser t ion ) ,a n d i n tr a -op e ra ti v e v i d e o k e ra t o g ra p h y a n d / o r r e f ra c t o -m e t ry a r e n e c e s s a ry a s w a y s t o m o n i t o r t h e c o rn e a lc u rv a t u r e a n d / o r r e f r a c t i o n a t t h e t i m e o f s u rg e ry . M o rew o rk i s n e e d e d t o a d d re s s t h e s e t w o i s s u e s .Advanced Cornea l Sys tems o f I rv ine Cal i fo rn ia i sr e v is i ti n g t h e c o n c e p t o f o r t h o k e ra t o l o g y b u t w i t h o n eimpor tan t d i f fe rence : the co rn ea i s f i r s t ' des tab i l i zed ' by

i n j e c ti o n s o f h y a l u ro n - i d a se . Th e c o rn e a l s h a p e i sa l t e red wi th a se r ies o f ever- f l a t t e r con tac t l enses , andt h e c o rn e a is t h e n c u re d w i t h a n o t h e r m e d i c a t i o n w h e nthe idea l re f rac t ion is ob ta ined . US c l inica l t r i a ls a re se tto beg in th i s year .

H o l m i u m t h e rm o k e ra t o p l a s t y w il l h a v e a l i m i t e d b u ti m p o r t a n t r 6 1 e i n t h e n e w m i l l en i u m , fo r c o r r e c t i o n o fl o w e r d e g re e s o f h y p e ro p i a a n d fo r t h e c o r r e c t i o n o f ov e r-co rr ec te d myop ic PRK (and poss ib ly LASIK) pa t ien t s .A n i n t r i g u i n g n e w m e t h o d o f a p p l y i n g t h e r m a le n e rg y t o t h e c o rn e a i s w i t h r a di o f r e q u e n c y e n e rg y .Th e R e f r a c t e c u n i t i s b e i n g u s e d i n M e x i c al i, M e x i c o b yt h e D r s A n t o n i o M e n d e z a n d A n t o n i o M e n d e z N o b l e ,and in a mult i -centre U.S. cl in ical t r ial as well withe n c o u r a g i n g c l i n i c a l r e s u l t s f o r t h e t r e a t m e n t o fhyperop ia .Th e Ar t i san (OPH TEC), NuV i ta (Ch i ron Vis ion ), andSTAAR phak ic in t raocu lar l enses wi l l have an impo r tan tr61e in the co rrec t ion o f h igh re f rac t ive e r ro rs in the ne wm i l l e n n i u m , a s l o n g a s p u p i l o v a l i z a t i o n , c a t a r a c tfo rm a t io n , a n d s e c o n d a ry g la u c o m a c a n b e k e p t t o ami n im um dur in g c l inica l t ri al s.A n e m e r g i n g f i e l d i n r e f r a c t i v e s u r g e r y i s t h ecorrec t ion o f p resbyop ia by man ipu la t ion o f the c i l i a ryb o d y / z o n u l a r / l e n t i c u l a r r e la t io n s h ip . B o t h o f t h e c u r -r e n t a p p ro a c h e s ( a n t e ri o r ci li a ry s c l e ro t o m y a s c h a m -p i o n e d b y D r S p e n c e Th o rn t o n , a n d s c l e r a l e x p a n s i o nb a n d s a s p o p u l a r is e d b y D r s . R o n a l d S c h a c h e r a n dSheld on Her tz ig ) a re based on the p r inc ip le o f pu t t ingt h e z o n u l e s o n s t r e t c h o n c e a g a in , t o c o m p e n s a t e fo r t h eincre ased s ize o f the m atu re l ens . Inves t iga t ions in tob o t h p ro c e d u re s a r e a t s u c h a n e a r l y s t a g e t h a t i t i sd i f fi cu lt to accu ra te ly p red ic t w hat r61es the y wi ll p lay inr e f r a c ti v e s u rg e ry i n t h e n e w m i l l e n ni u m .A d d r e s s f o r C o r r e s p o n d e n c eRefrac t ive Surgery Cen ter , EENT Ins t i tu te , 2626 Napo-lean Avenue , New Orleans , LA 70115 , USA

C O N T A C T L E N S A P P L I C A T I O N S F O L L O W I N G R E F R A C T IV E S U R G E R Y D I S A S T E R SBA Weissman

Th e m a j o r it y o f p a t ie n t s u n d e rg o i n g r e f r a c ti v e s u rg e ryappear to be sub jec t ive ly p leased w i th resu l t s; a l thoug hth i s f igu re may be somewhat over ly op t imis t i c , re f rac-t i v e s u rg e o n s t y p i c a l l y r e p o r t t h e p r e v a l e n c e o f ' p o o rv i sua l resu l t s ' a t the 1% leve l . Refrac t ive su rg eryp ro c e d u re s i n c l u d e b o t h t h o s e w h i c h m o d i fy c o rn e a l

cu rva tu re (e .g. ILK, AK, H exK, ALl ( , L ASIK, In tacs e tc . )a n d t h o s e w h i c h m o d i fy i n t ra o c u l a r o p ti c s ( e . g. d e a rl e n s e x t r a c t i o n , p h a k i c IO Ls e t c . ) . W h e n c o n s i d e r i n go n l y t h o s e p ro c e d u re s w h i c h m o d i fy t h e c o rn e a l s u r-f a c e , p o o r o p t ic a l r e s u l ts u s u a l l y o c c u r s e c o n d a ry t oi r r e g u l a r c o rn e a l a s t ig m a t i s m o r s p h e r i c a l a b e r r at i on .


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S i m i la r i rr e g u l a r c o r n e a l s u r f a c e s o c c u r s e c o n d a r y t okera t oconus , t r auma, i n fec t i on ( e .g . HSK) and o t hersu rger i es ( e .g . pene t r a t i ng kera t op l as t y ) . Con t ac t l ens(CL) care i s s i mi l a r fo r a l l i r r egu l ar co rnea l su r f aces ,r e g a r d l e s s o f a e t io l o gy . R ig i d g a s p e r m e a b l e c o n t a c tl e n s e s a r e t h e m a i n s t a y o f t r e a t m e n t f o r a ll th e v a r i o u sp r o b l e m s w h i c h c a u s e i r r e g u l a r c o r n e a l a s t i g m a t i s m ,i nc l ud i ng r e f r ac t ive su rger i es . O ccas i ona l l y s t anda rdd e s i g n s p h e r i c a l R G P s , w i t h s t a n d a rd d i a m e t e r s a n dp e r i p h e r a l c u r v e s y s t e m s , m a y b e e f f e c ti v e . M o r ecommonl y , however , t he c l i n i c i an can i ncrease e f f ec t i v -i t y b y a p p r o p r i a t e u s e o f u n u s u a l l y s t e e p o r fl a tp e r i p h e r a l s y s t e m s a n d r e l a ti v e ly la r g e d i a m e t e r C L s ,b e c a u s e o f t h e d i s to r ti o n o f n o r m a l c o r n e a l s u r f a c et o p o g r a p h y . U s e o f r e v e r s e g e o m e t r y p e r i p h e r a l c u r v e s ,and t he var i ous b i t o r i c l ens des i gns , a r e a l so occas i on -

a l l y he l p fu l i n es t ab l i sh i ng mechan i ca l l y and op t i ca l l yef f ec t i ve r i g id CLs . Bo t h s t an dard and t o r i c hydroge lC L s , o r l e s s u s u a l h y b r i d d e s i g n s ( e . g . p i g g y b a c k o rSof t Perm e t c . ) r a r e l y may p rove he l p fu l . Ref r ac t i vesu rg ery pa t i en t s , in par t icu l a r , e l ec t thes e p roc edu resp r i mar i l y t o e li mi na t e nee d fo r spec t ac l es and CLs . Suchpat i en t s a r e u sua l l y unhap py i f t he y f ind t ha t CLs , andp a r t i c u l a r l y R G P C L s , a r e n o t o n l y a d v i s a b l e b u tn e c e s s a r y f o r o p t i m u m v i s i o n p o s t s u r g e r y . T h u s t h ec l in i c ian m us t a l so be p re pare d t o dea l wi t h t he pa t i en t ' sp sycho l og i ca l d i sappo i n t men t .

T h e p r o c e d u r e s , a n d C L o p t i o n s, a n d t h e c o m p l ic a -t i ons wi l l be r ev i ewed .A d d r e s s f o r C o r r e s p o n d en c e2 5 6 7 A m h e r s t A v e n u e , L o s A n g e l e s , C A 9 00 64 , U S A

1 4 3

R E F R A C T I V E S U R G E R Y F R O M A N O P T O M E T R I C P E R S P E C T I V EJ CraigF o r s o m e , r e f r a c t i v e s u r g e r y h a s b e c o m e a v i a b l ea l t e rna t i ve t o spec t ac l e o r con t ac t l ens co r r ec t i on o fa m e t r o p i a . R e a s o n s f o r s e e k i n g t r e a t m e n t v a r y , b u to f t e n i n c l u d e i n t o l e r a n c e t o a c u r r e n t m o d e o fr e f r a c t i v e c o r r e c t i o n a n d t h e d e s i r e f o r b e t t e r u n a i d e dv i s i o n . T h e r 6 1e o f t h e o p t o m e t r i s t w i t h i n t h eref r ac t i ve su rgery se t t i ng can be an i n t e r es t i ng andvar i ed one . P re-opera t i ve pa t i en t assessmen t ; p sycho-l og i ca l as wel l as oph t ha l mi c , i s es sen t i a l fo r t herecru i t me n t o f su i t ab l e ind i v idua l s . A ques t i onnai r eh a s b e e n d e s i g n e d s p e c if ic a l ly f o r e s t a b l is h i n g p a -t i e n t s ' m o t i v e s f o r u n d e r g o i n g e x c i m e r l a s e r t r e a t -men t , i n o rder t ha t app rop r i a t e counse l l i ng can beg i ven and r ea l i s t i c expec t a t i ons se t . I n t r a -opera t i ve l y ,i n v o l v e m e n t c a n r a n g e f r o m p r e p a r i n g t h e r e f r a c t i v ep a r a m e t e r s n e c e s s a r y fo r p r o g r a m m i n g t h e l a s e r t oass i s t i ng t he su rgeon du r i ng t he p rocedure i t se l f . I na d d i t i o n t h e e x c i m e r l a s e r c a n b e u s e d b o t h t o c o r r e c tr e f r ac t i ve e r ro r and , t herapeu t i ca l l y , t o t r ea t a mu l t i -t u d e o f p a t h o lo g i c a l c o n d it io n s , t h u s t h e p r o c e d u r ev a r i e s f r o m c a s e t o c a s e . A s e l e c t i o n o f t h ep r o c e d u r e s p e r f o r m e d i n r e c e n t y e a r s a t t h e C o r n e a lD i s e a s e s a n d E x c i m e r L a s e r R e s e a r c h U n i t i n D u n d e ewi ll be desc r i bed . In t e rms o f t he i dea l pos t -opera t i ve

care , pa t i en t s r equ i r e , no t on l y r e f r ac ti on , bu t a l soc o r n e a l t o p o g r a p h i c e v a lu a t io n , m e a s u r e m e n t o f c o n -t r a s t s e n s i t M t y , a n d a n a s s e s s m e n t o f f u n ct io n a l,p sycho l og i ca l , and sa t i s f ac t i on ou t comes . Over 300p a t i e n t s h a v e b e e n t r e a t e d a t t h e c e n t r e i n D u n d e e ,f o r m y o p i a , h y p e r m e t r o p i a , a s t i g m a t i s m o r c o r n e a lp a t h o l o g y , m a n y w i t h f u n d i n g f r o m t h e N a t i o n a lH e a l t h S e r v ic e . A s p e c t s o f m a n a g e m e n t a n d o u t c o m ew ill b e d i s c u s s e d o n t h e b a s i s o f p e r s o n a l r e s e a r c ha n d p u b l i s h e d r e s u l t s , i n c o n j u n c t i o n w i t h t h epo t en t i a l fo r r esea rch i n t h i s ever - evo l v i ng f i e ld .N e w e r im a g i ng t e c h n i q u e s s u c h a s in-vivo c o n f o c a lm i c r o s c o p y a n d s l it - sc a n n i n g e l e v a t io n t o p o g r a p h ya l lo w t h e e f f e c t s o f r e f ra c t iv e s u r g e r y o n t h e c o r n e at o b e o b s e r v e d i n c o n s i d e r a b l y m o r e d e t a i l t h a np r e v i o u s l y p o s s i b le . T h e r e s u l t s o f t h e s e a n d o t h e ri nves t i ga t i ons wh i ch may d i c t a t e t he fu t u re d i r ec t i ono f r e f ra c t iv e s u r g e r y d e v e l o p m e n t s i n t h e c o n t i n u e ds e a r c h f o r t h e u l ti m a t e m a n a g e m e n t o f a m e t r o p i a w il lb e d i s c u s s e d i n t h e p r e s e n t a t i o n .A d d r e s s f o r C o r r e sp o n d e n c eDi sc i p l ine o f Oph t ha l m ol ogy , Un i ve r s i t y o f Auck l and ,Pr i va t e bag 92019 , Auck l and 1001 , New Zeal and

V I D E O K E R A T O S C O P Y I N C O N T A C T L E N S P R A C T I C EL CarneyT h e a v a i la b i li ty o f v i d e o k e r a t o s c o p e s h a s p r o v i d e dcon t ac t l ens p rac t i t i oner s wi t h ex t ens i ve and de t a i l edi n fo r m a t io n a b o u t c o r n e a l t o p o g r a p h y . B u t h o w e f f e c t iv eh a s t h i s i n f o r m a t i o n b e e n i n a d v a n c i n g o u t c o m e s i np a t ie n t c a r e a n d c h a n g i n g c o n t a c t l e n s p r a c ti c e ?I n a n s w e r i n g t h is q u e s t i o n , s e v e r a l u n d e r l y i n gf e a t u r e s n e e d t o b e c o n s i d e r e d .

F i r s tl y , h o w v a l id a r e t h e s e c o r n e a l t o p o g r a p h ym e a s u r e m e n t s ? U s i n g a ra n g e o f t e s t s u r f a c e s , w e c a n

e s t a b l is h t h a t t h e r e i s n o s i m p l e a n s w e r t o t hi s q u e s t i o n ,s i n c e o u t c o m e s f o r d i ff e r e n t i n s t r u m e n t s d e p e n d o n t h es p e c i f i c t e s t c o n d i t i o n s a n d t h e a n a l y s i s p r o c e d u r e su s e d .S e c o n d l y , w h a t i s t h e m o s t e f f e c t i v e m o d e l f o rd e s c r i b i n g c o r n e a l t o p o g r a p h y i n a w a y w h i c h i s u s e f u li n c o n t a c t l e n s p r a c ti c e a n d w h i c h i n fo r m s c o n t a c t le n sdes i gn?T h i r d l y , h o w v a l u a b l e a r e t h e c o n t a c t l e n s f i ~ g

Contact Lens and Anter ior Eye


3/35

Abstractsi i !14 4 p ro g ra m s i n c o rp o ra te d w i t h v i d e o k e ra t o sc o p e s ? T h e s en e e d t o b e e v a l u a te d n o t o n l y i n t e rm s o f t h e f i t ti n gs t r a t e g y wh i c h i s e m p l o y e d b u t a l s o a g a i n s t t h e b a c k -g ro u n d o f t h e e s t a b l is h e d a c c u ra c y o f c o rn e a l t o p og ra -p h y m e a s u r e m e n t s a n d o t h e r k n o w n i n f l u e n c e s o n

contact lens fi t t ings.F o u r t h l y , wh a t c a n c o rn e a l t o p o g ra p h y m e a s u re -me n ts t e l l u s a bou t v i sua l func t ion? Recen t ly es tab l i shedin te r - re la t ionsh ips be tween co rnea l topography , re t ina limage qua l i ty and v i sua l func t ion g ive us in s igh ts in tom a n a g e m e n t s t r a t e g i e s f o r c o r n e a l a b n o r m a l i t i e s ,

whether pa tho log ica l o r su rg ica l ly induced .An d f i n al ly , c a n we u s e c o rn e a l t o p o g ra p h y m e a s u re -m e n t s t o i m p ro v e v is u a l p e r fo rm a n c e t h ro u g h o p t i m i s e dc o n t a c t l e n s d e s i g n ?E a c h o f t h e s e q u e s t i o n s w il l b e c o n s i d e re d b a s e d o nc u r r e n t p r a c t ic e a n d l i ke l y fu t u re d e v e l o p m e n t s .A d d r e s s f o r C o r r e s p o n d e n c eQu e e n s l a n d S c h o o l o f Op t o m e t ry , V i c to r ia P a rk R o a d,Kelv in Grove , Q ueen s land 4039 , Aus t ra l i a

C O N T E M P O R A R Y O R T H O K E R A T O L O G YP Caroline

T h e t e c h n i q u e o f o r t h o k e ra t o l o g y c a n b e d e f i n e d as t h ere d u c t i o n o r m o d i f ic a t io n o f r e f r a c t iv e e r ro r s t h ro u g ht h e a p p l i c a t i o n o f m o d e rn , r e v e r s e g e o m e t ry , r i g i dc o n t a c t le n s e s . T o d a y , o r t h o k e ra t o l o g y i s a c c o m p l i s h e dth rou gh a s ing le o r se r ies o f l enses , w h ich f la tt en thec e n t r a l r a d i u s o f t h e c o rn e a t h e r e b y r e d u c i n g m y o p i aand improv ing una ided v i sua l acu i ty .T h e m o d e r n r e n a i ss a n c e o f o r t h o ke r a t o lo g y h a s b e e ndramat ica l ly in f luenced by the in t roduct ion of:1. N e w ' r e v e r s e g e o m e t r y ' l e n s d e s i g n s w h i c hproduce rap id and d ramat ic a l t e ra t ions in co rnea lcu rva tu re .2 . Ad v a n c e s in n e w h i g h Dk , R GP l e n s m a t e r i a l s f o re n h a n c e d p h y s io l o g ic r e s p o n s e .3 . Ad v a n c e s i n c o rn e a l m a p p i n g t e c h n i q u e s t o a id in

m o re a c c u ra t e f i r s t f it l e n s s e l e c t i on a n d i m p ro v e dpos t - f i t t ing pa t ien t managemen t .4 . Ne w c o n c e p t s r e l a te d t o t h e p h y s i o l o g y o f t i s s u ed i s p l a c e m e n t p ro v id i n g a c l e a r e r u n d e r s t a n d i n g a st o h o w o r t h o k e ra t o l o g y wo rk s .T h e s e e v o l u ti o n a ry a d v a n c e s h a v e d ra m a t i c al l y c h a n -g e d t h e m o d e rn p ra c ti t io n e r s ' vi e w o f o r th o k e ra t o l o g y .T o d a y , t h e p ro c e d u re h a s m o v e d f ro m a s p e c i a l i t yp ra c t i s e d b y o n l y a h a n d fu l o f p r a c t i t io n e r s , t o at e c h n i q u e t h a t c a n b e s u c c e s s fu l ly i n c o rp o ra t e d i n toa lmos t any p rac t ice .

A d d r e s s f o r C o r r e s p o n d e n c e13606 Blazer T ra i l , Lake Oswego , Oregon 97035-1358 ,U SA

C O N T.4 2 II NA T IO N O F H Y D R O G E L C O N T A C T L E N S D I S I N F E C T I O N S Y S T E M SC Lakkis

A n u m b e r o f in f e c ti o u s a n d i n f l a m m a t o ry c o m p l ic a t io n so f m i c ro b ia l o r ig i n h a v e b e e n l i n k e d t o t h e we a r o fcon tac t l enses . Ulcera t ive kera t i t i s i s the mo s t se r ious o ft h e s e , w i t h t h e c o n d i t i on s o m e t i m e s c a u s i n g s c a r r i n g o ft h e c o rn e a a n d r e s u l t i n g i n p e rm a n e n t v is i on l o ss .In f l a m m a t o ry r e a c t i o n s o c c u r m o re c o m m o n l y t h a nin fec t ious compl ica t ions bu t wh i l s t the y do no t gene ra l lyr e s u l t i n v is i on l o ss , t e m p o ra ry o r p e m m n e n t c e s s a t i o no f l e n s w e a r m a y b e a c o n s e q u e n c e .A wi d e r a n g e o f m i c ro -o rg a n i s m s h a s b e e n i m pl i-ca ted as causa t ive agen ts in in fec t ious and in f lamma-to ry con tac t l ens re la ted compl ica t ions . Whi l s t thep a t h o g e n e s i s o f t h e s e c o m p l i c a ti o n s r e m a i n s u n c l e a r ,par t i cu la r ly fo r in f la lmnato ry reac t ions , bac te r ia l con-tamina t ion o f the eye appears to p lay a s ign i f ican t r6 le .Lens hand l ing , and c on tamina t ion o f the l ens , l ens casea n d l e n s c a r e s o l u t i o n s h a v e b e e n i m p l i c a t e d i ni n c re a s i n g t h e o c u l a r i n o c u l u m o f m i c ro -o rg a n i s m sd u r i n g l e n s we a r . A t h o ro u g h u n d e r s t a n d i n g o f h o w

poten t ia l ly pa thogen ic bac te r ia ga in access to the eyei s v ital i f we a re to p rom ote safe and success fu l con tac tl e n s we a r .Th is p resen ta t ion wi ll p rov ide an overv iew o f con tac tl e n s r e l a t e d c o m p l i c a ti o n s o f m i c ro b ia l o r i g i n a n dd i s c u s s t h e i n c i d e n c e a n d c o n t r i b u t i n g f a c t o r s t omicrob ia l con tam ina t ion o f hyd roge l con tac t l ens d is in -f e c t io n s y s t e m s . T h e t y p e s a n d l e v el s o f c o n t a m i n a ti o ntha t a re observed wi th var ious d i s in fec t ion sys tems wi l lbe cons idered and bo th c l in ica l and bac te r ia l fac to rscon t r ibu t ing to con tam ina t ion wi ll be d i scussed . Ina d d it io n , t h e a d e q u a c y o f c u r r e n t IS O/ F D A t e s t i n gp ro c e d u re s fo r r e g u l a t o ry a p p ro v a l o f d i s i n f e c t i o ns y s t e m s w i ll b e e x a m i n e d a n d s u g g e s t i o n s fo r r e d u c i n gcon tam ina t ion wi ll be p rov ided .A d d r e s s f o r C o r r e s p o n d e n c eUnivers i ty o f Cal iforn ia , Be rke le y Schoo l o f Op tom et ry ,#688 Minor Hall , Berkeley CA 94700-2020, USA



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Abstracts

T H E F U T U R E O F C O R N E A L T O P O G R A P H Y I N T H E C O N T AC T L E N S P R A C T IC EP Car o l ineC u r re n t c o rn e a l t o p o g ra p h y a s s e s s m e n t t e c h n i q u e s a r eu n d e rg o i n g c o n s i d e ra b l e e v o l u t i o n i n b o t h h a rd w a reand in the so f tware a lgo r i thms used to ca lcu la te andd i s p l a y c o rn e a l c u rv a t u r e . I t i s t h e r e fo re p ru d e n t t h a te y e c a r e p ro fe ss i o n al s s t a y a b re a s t o f t h e s e d y n a m i cc h a n g e s , e s p e c ia l l y i n l i g ht o f t h e m a n y n e w c o n t a c t l e n sd e s i g n s a n d r e f r a ct i v e s u rg e ry o p t i o n s b e i n g p r e s e n t e dto ou r pa t i en t s .Th r o u g h o u t t h is l e c t u r e w e w il l f o c u s o n t h e fu t u r e o fc o rn e a l t o p o g ra p h y a s s e s s m e n t a s i t re l a t e s to :1 . Th e n o rm a l c o rn e a2 . Th e p a t h o lo g i c c o rn e a

3 . Th e r e f r a c t iv e c o rn e a l s u rg e ry p r a c ti c e4 . Th e m o d e rn c o n ta c t l e n s p r a c t ic eS p e c i a l e m p h a s i s w i l l b e d i r e c t e d t o w a rd s u s e s fo rt o p o g ra p h y a s s e s s m e n t in t h e c o n t e m p o ra ry c o n t a c tl e n s p r a c t i c e . N e w t e c h n i q u e s w i l l b e p r e s e n t e d o ns a g it ta l h e i g h t a n a l ys i s t h ro u g h v i d e o k e ra t o g ra p h y a n dthe r61e o f sag i t t a in the f i t t ing RGP and so f t con tac tl enses .

A d d r e s s f or C o r r e s p o n d e n c e13606 Blazer Tra i l , Lake Oswego , Oregon 97035-1358 ,U S A

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R G P L E N S E S A N D T H E I R R O L E I N SL O VC IN G M Y O P I C P R O G R E S S I O NA Canel laM y o p i a is s a i d to b e t h e m o s t c o m m o n o c u l a r d i s o rd e ra f f e ct i ng m a n k i n d . W h i l e t h e e p i d e m i o l o g y va r i e s b yc o u n t ry a n d c u l t u r e , o n e f a c t r e m a i n s , m y o p i a i sincreas ing wor ld -wide . Th is p resen ta t ion i s a rev iewo f m y o p i c p ro g re s s i o n c i t i n g p a st s t u d i e s s u c h a sS p e rd u t o e t a l . , The F ra m i n g h a m O f f s p r i n g S t u d y ,Y u p i k Es k i m o S t u d y , S i n g a p o re A rm y r e c ru i t s b y Ta yet al. , I s r a e l i S t u d y , M e l b o u rn e V i s u a l Im p a i rm e n tPro jec t . Prev ious l andmark myop ia s tud ies u t i l i s ingr i gi d c o n t a c t l e n s e s s u c h a s M o r r i s o n 1 9 5 6 , S t o n e1 97 6, a n d G ro s v e n o r 1 9 9 1 w i ll b e c o m p re h e n s i v e l yr e v i e w e d w i t h r e g a rd t o t h e i r f i n d i n g s a s w e l l a s t h e i rs ign i f i cance in iden t i fy ing t rends . Cu rren t s tud ies su cha s C Y K h o o et al. , 1 9 9 7, t h e C o n t a c t Le n s A n d M y o p i aP ro g re s s i o n (C LA M P ) S t u d y b e i n g d o n e a t O h i o S t a t eU n i v e r si t y, a n d t h e S i n g a p o re M y o p i c T re a t m e n t S t u d y(C L-M TS ) b e i n g c o n d u c t e d a t t h e S i n g a p o re Ey e

R e s e a rc h In s t it u te . Th e c o m m o n t h r e a d o f t h e s e s t u d yre s u l t s s h o w s t h a t d e s p i t e s t u d y s h o r t c o m i n g s , u s e o fr ig id con tac t l enses appears to p lay a ke y r61e in thep reven t ion o f myop ic p rogress ion . Key to th is p re-sen ta t ion i s the s ign i f i cance and impact o f the var iousf ind ings as they re la te to the u se o f r ig id con tac t l ense sto mi t iga te and to ha l t myop ic p rogress ion in ch i ld ren .M o re c r it ic a l i s h o w e y e c a r e p r a c t i t io n e r s a n d c o n t a c tl ens f i t t e rs wi l l p rocess th i s in fo rmat ion and beg in tofo rm u l a t e c o m m u n i c a t i o n s t r a te g i e s t o e d u c a t e p a r e n t sa n d p ro s p e c t i v e p a ti e n ts o n t h e c o u r s e o f m y o p i a a n dt h e r a t i o n a l e b e h i n d t h e u s e o f R G P l e n s e s t o s l o w o rs top i t s p rogress ion .A d d r e s s f o r C o r r e s p o n d e n c eP o l y m e r Te c h n o l o g y C o rp o ra t io n , 1 00 R e s e a rc h D r i v e ,W i l m i n g t o n M A 0 1 8 87 , U S A

A N O V E L A S P H E R I C S U R F A C E F O R C O N T A C T L E N S E SW S a m m o n sA s p h e r i c s u r f a c e d e s i g n s i n c o n t a c t l e n s e s h a v e ,usua l ly , two main ob jec t ives . P laced on the backsurface , they p rov ide oppor tun i t i es to c rea te favour-a b l e r e l a t i o n s h i p s w i t h t h e c o rn e a l s h a p e a n d , o n t h ef ro n t , t h e y p ro d u c e v a r i a t i o n i n p o w e r n e e d e d , f o rexam ple , in mul t i foca l p resbyo p ic co rrec t ion . Which-e v e r m o d a l i t y i s in t e n d e d , a s p h e r i c s u r f a c e s a r eu s u a l l y q u i t e s i m p l e m a t h e m a t i c a l f u n c t i o n s w i t hsmooth , con t inuous der iva t ives , y ie ld ing the requ i redsmooth cu rva tu re p ro f i l es . The con ic sec t ion , fo re x a m p l e , p ro v i d e s a w h o l e f a m i l y o f a s p h e r i c s u r f a c e sc l a s s i f i e d b y t h e d i s t i n g u i s h i n g p a ra m e t e r o f e c c e n -t r i c i t y . H o w e v e r , t h e s e a n d s o m e o t h e r m a t h e m a t i c a ls u r f a c e r e p re s e n t a t i o n s l a c k t h e i n g re d i e n t s t o p ro -duce rea l ly e f fec t ive cu rva tu r e var ia t ion , esp ec ia l ly fo r

p resbyop ic co rrec t ion , and the sub jec t o f th i s paper i st h e e v o l ut io n o f a w h o l e n e w c l a ss o f f u n c t io n s w h i c hdo po ssess th i s ab il ity. T he y d i f fe r rad ica l ly f romt h o s e n o rm a l l y u s e d i n a c r i t ic a l w a y . Th e s e a r efu n c t i o n s w h i c h d e s c r i b e t h e c o -o rd i n a t e s u r f a c eshape smooth ly and con t inuous ly , bu t the i r der iva t ivesg ive r i se to s ingu lar i t i es , near wh ich rap id changes o fs lope and cu rva tu re a r i se . Choos ing the loca t ion o fthe s ingu lar i t i es therefo re resu l t s in a very powerfu lt e c h n i q u e fo r d e s i g n i n g a l m o s t l i m i t l e s s c u rv a t u r ev a r i a t i o n s , w h i c h p ro d u c e s e n s i t i v e p o w e r c h a n g e sa c ro s s t h e l e n s . S u r f a c e d e s i g n s b a s e d o n t h i sm a t h e m a t i c a l f o r m u l a t i o n h a v e b e e n s u c c e s s f u l l ya p p l i e d i n c o n t a c t l e n s m a n u fa c t u r e t o g i v e l e n s e swi th un ique mul t i foca l p roper t i es . Fun ct ion param eters



5/35

~ .~ Abstracts14 6 a l l o w t h e d e s i g n e r a c h o i c e o f s u r f a c e e i t h e r f o rp resy byo p i c co r r ec t i on , o r t o co r r ec t spher i ca l aber r a -

t i on and enhance no rmal v i s i on .A d d r e s s f o r C o r r es p o n d e n c e11 Sti l l ions Clos e, Windm il l Hil l, Al ton, Ha nts GU 34 2RX

C O R N E A L A S P H E R IC I T Y A N D R G P L E N S W E A RS KlyceW e d e v e l o p e d t h e c o r n e a l a s p h e r i c i ty i n d e x ( C A D ,whi ch i nd i ca t es t he aspher i c i t y o f t he ce n t r a l co rneau s i n g t h e T M S - 1 v i d e o k e r a t o s c o p e a n d u s e d t h e C A [ toe v a l u a te b o t h n o r m a l c o r n e a s a n d c o r n e a s w i t h r ig i d g a sp e r m e a b l e ( R G P ) l e n s i n d u c e d w a r p a g e . T h e C A [(mean_+ s t andard dev i a ti on ) fo r t he 22 con t ro l co rne aswa s 0 .33 + 0 .26 , wh i ch i nd i ca t es t h a t t he no rma l cen t r a lc o r n e a h a s a p r o la t e s h a p e . T h e a v e r a g e C A I f o r t h e 2 4c o r n e a s w i t h R G P l e n s i n d u c e d w a r p a g e w a s s i g n i f i -

c a n t ly l o w e r ( - 0 . 1 5 + 0 . 3 6 , P = 0 .0 0 0 1) . T h e s e d a t as u g g e s t t h a t s o m e c o r n e a s h a v e a b n o r m a l a s p h e r i c i t yi n t h e c e n t r a l c o r n e a w h e n w a r p a g e o c c u r s w i t h R G Pl e n s e s . C A [ i s u s e f u l f o r t h e q u a n t it a ti v e a s s e s s m e n t o faspher i c i t y and t opograph i c abnormal i t i es i n t he cen t r a lc o r n e a c a u s e d b y c o n t a c t l e n s i n d u c e d w a r p a g e .A d d r e s s f o r C o r r e sp o n d e n c e2858 a t 6 t h S t r ee t , N ew O r l eans L A 70115 , USA

M E A S U R I N G N O N - S P H E R I C A L O P T IC A L S U R F A C E SC WoodsIntroduction: M o r e l e n s d e s i g n s f o r t h e p r e s b y o p i cm a r k e t a r e e m e r g i n g . T h e u s e o f n o v e l d e s i g n s t ogenera t e var i foca l op t i cs i n con t ac t l enses i s i ncreas i ng .A n u m b e r o f d e s i g n s in c o r p o r a t e a s p h e r i c s h a p e s , o fk n o w n p - v a l u e s on t h e f r o n t a n d b a c k s u r f a c e o f c o n t a c tl e n s e s . F r e q u e n t l y t h e r a d i u s o f c u r v a t u r e q u o t e d b y t h emanufac t u rer i s a nomi na l r e f e rence mak i ng ver i f i ca t i ono f t hes e l e nse s d i ff icu lt . Cou l d a v i de oke ra t osc ope o r ar a d i u s c o p e v e r i fy th e s e c o m p l e x s u r f a c e s ?Methods: T h i s s t u d y a s s e s s e s w h e t h e r c l i n i c a l e q u i p -m e n t c a n v e r i fy t h e s e c o m p l e x s u r f a c e s f o r a r a n g e o fc o n c a v e s u r f a c e s o f k n o w n c u r v a t u r e s ( 7. 30 m m t o8 .10 mm ) and k now n p -va l ues (p=0 .0 t o p= l .0 ) .Results: T h e v i d e o k e r a t o s c o p e w a s a b l e to d e s c r i b e t h ep - v al u e f o r th e s u r f a c e to a h i g h d e g r e e o f a c c u r a c y(_+0 .15 [2 SD] ) b u t d i d dem ons t r a t e b i as , acco rd i ng t od i screpa ncy ana l ys i s (mean d i f fe r ence=0 .048 + 0 .02 [2S E ] ). T h e d e g r e e o f a c c u r a c y f o r t h e m e a s u r e m e n t o ft h e r a d i u s o f c u r v a t u r e o f t h e c o n c a v e s u r f a c e w a s a l s overy h i gh (_+0 .014) wi t hou t any dem ons t r a t i on o f b i as

( m e a n d i f f e r e n c e = - 0 . 0 7 , 0 .0 22 ). T h e r a d i u s c o p e w a sa b l e to v e r i fy t h e r a d i u s o f c u r v a t u r e t o a h i g h d e g r e e o fa c c u r a c y ( + 0 . 0 7 2 ) w i t h o u t b i a s ( m e a n d i ff e r-ence=0 .008 + 0 .01 ). How ever , ver i f i ca t ion o f t he p -va l ueb y u ti li s in g B a k e r ' s e q u a t i o n d e m o n s t r a t e d a p o o rd e g r e e o f a c c u r a c y ( + 0 . 5 7 4 ) a n d a b i a s ( m e a nd i f fe r ence=0 .134 , _+0 .078) . Th ese r esu l t s fo r t he mea-s u r e m e n t o f t h e p - va l ue f o r t h e r a d i u s c o p e w e r es t a t is t i ca ll y s i gn i fi can t ly d i f f e r en t f rom t ha t o f t he know nm ea su r em en t (P=0 .0375) and t ha t fo r t he v i deokera t -ometer ( / ' - -0 .0050) .Conclusion: T o d e t e r m i n e t h e d e g r e e o f a s p h e ri c i ty o fa c o n c a v e o p t i c a l s u r f a c e t o a n a c c e p t a b l e d e g r e e o fa c c u r a c y a v id e o k e r a t o m e t e r c a n b e u s e d i n p re f e r e n c et o a r a d i u s c o p e . B o t h i n s t r u m e n t s d e m o n s t r a t e d a h i g hd e g r e e o f a c c u r a c y w h e n m e a s u r i n g t h e r a d i us o fcu rva t u re .A d d r e s s f o r C o r r e s p o n de n c eT h e V i c to r ia n C o l le g e o f O p t o m e t r y , C n s K e p p e l a n dCardigan St reets , Car l ton 3053, Victor ia, Aust ral ia

N E O V AS C UL A R IZ A TI ON : T H E S U P E R F I C I A L A N D T H E D E E PB A W e i s s m a nA s a n o p t o m e t r y s t u d e n t i n B e r k e l e y i n t h e e a r l y 1 9 70 s,I w a s t a u g h t t h a t c o n t a c t l e n s e s w e r e f a i r l y b e n i g nd e v i c e s . I l e a r n e d t h a t c o m m o n l y e n c o u n t e r e d p h y s i o -l og i ca l compl i ca t i ons were l i mi t ed t o var i ous man i f es t a -t i on s o f h y p o x i a g e n e r a t e d c o r n e a l o e d e m a , 3 / 9( ' j ux t apos i t i ona l ' ) co rnea l s t a i n i ng , and con j unc t i va li n je c ti o n. T h e m o s t c o m m o n c o m p l i c a ti o n s o f a ll w e r eu n s u c c e s s f u l fi ts a n d l e n s s o il a g e. T h i s w a s i n t h e d a y sw h e n a ll ri g id C L s w e r e P M M A a n d e a r l y s of t l e n s e sw e r e j u s t a p p e a r in g o n t h e s c e n e .

Subsequen t l y , as a c l i n i c i an i n var i ous academi cenv i ro nm en t s ( f ir s t i n no r t he rn Cali fo rn ia , t hen Jerus a-l e m , a n d e v e n t u a l ly L o s A n g e l e s ) , I l e a r n e d t h a t s e v e r er e a c t i o n s c o u l d o c c u r . G P C , f o r o n e e x a m p l e , w a s a n e wd i s e a s e ; i t s n a t u r a l h i s t o r y a n d t r e a t m e n t w e r e b e i n guncovered as I en t e red c l i n i ca l p rac t i ce . I have spen tm u c h o f m y s u b s e q u e n t a c a d e m i c c a r e e r i n t e re s t e d i nmi crob i a l co rnea l i n fec t i on .A t H e b r e w U n i v e r s i t y / H a d a s s a h h o s p i t a l i n I s r a e l , Ia l s o s a w s e v e r a l e y e s w i t h v a s c u l a r iz e d c o r n e a s , s o m e

Contact Lens and Anterior Eye


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A b s t r a c t s

attributed to various ocular diseases, but some clearlyassociated with contact lens wear. Isaac Michaelson wasstill alive then, the former Chair of the Development,and a giant of a man. While some of his researchinterest was in the study of those diseases which causedretinal neovascularizafion (e.g. diabetes), he had used acorneal model (with David Maurice) to support his ideathat some angiogenic biochemical messenger (his'factor X') was probably produced by stressed tissues:retina or cornea. Hearing his ideas and reading hispapers, and seeing some patients with this complicationof CL wear, initially caught my interest. Perhaps it wasalso because these vessels are so easily observed andinteresting - even pretty - at the biomicroscope. Inbetween other long-term projects which you mightrecall reading at some time, I have returned to this topicfrom time to time over the past 20 years with variousstudents and colleagues.

Cogan proposed in 1949 that the lack of vasculatnrein the normal cornea was due to the compactness of thestroma - but many of us have observed corneas swollenfrom endothelial dysfunction which do not vascularizefor years. Contact lens practitioners have also noted tha tpannus associated with 3/9 staining progresses fromthe timbus to where the CL begins, and then stops;clearly this process is not due to hypoxia leading tostromal swelling at all.NV is now known to be the final common pathway of agreat variety of corneal problems, and probably repre-sents a healing effort on the part of the tissue when thenormal balance of negative and positive mediators ofangiogenesis is upset. It is now also clear that NV is theresult of a cascade of cellularly derived biochemicalmediator interactions (and that leukocytes as well aslocal tissues are involved) which can be elicited by alarge variety of anterior segment insults. One of thesemediators, Vascular Endothelial Growth Factor (VEGF),may be Michaelson's factor X and is known to beupregulated by hypoxia among other things.CL wear is known to cause both superficial (com-mon) and deep (very rarely) stromal NV. Superficial NV,also called 'pannus', usually follows either (1) chronic'3-9' or 'juxtapositional' epithelial staining, which weknow is a consequence of chronic limbal desiccation, or(2) hypoxia associated with the daily wear of low Dk(thick-edged high minus optically powered, or Soft-Perm) hydrogel CLs or extended wear of any CL. Deep

stromal vessels may follow (1) very severe 3-9 staining(called pseudopterygium or vascularized timbal kerati-tis), (2) hypoxia from daily wear of very low Dk CLs(e.g. 'SoftPerm') or extended wear, and (3) has alsobeen associated with keratoconus.Because NV is typically a 'silent' complication, in tha tpatients are subjectively unaware of the problem untilthe clinician makes the observation; clinical manage-ment may first consist of enhanced professionalobservation. When NV is noted, the clinician mustmake a judgement whether intervention or continuedobservation, perhaps at a more frequent interval, iswarranted. Photographic documentation is very helpfulin following such patients and assists in appropriatetiming and monitoring of intervention if elected.Intervention may consist of changing the patientfrom an extended wear to a daily wear schedule.Patients who develop pannus due to extended wear or

use of thick edged hydrogels may be re-fitted intomodest to high Dk RGPs (or perhaps one of the newhigh Dk silicone hydrogel designs); patients whodevelop NV from 3-9 stain may benefit from beingdispensed standard hydrogel CLs, or new RGPs withlarger diameters and higher ed ge lifts to address limbaldesiccation. The clinician should always considerdiscontinuing purely cosmetic CL wear. Followingplanned intervention, the clinician should continue tomonitor the patient's course to be sure that the bloodvessels both become less inflamed and cease growth.It gives one some satisfaction to see the progresswe have made as a field over almost three decades ofprofessional life. When I entered this profession, webarely recognised any complications to CL wear at all.Over the past several years we as a profession havebetter learned recognition, diagnosis and now manage-ment and treatment. We are also participating in thegrand adventure to learn some of the basic physiolo-gical interactions which allow these complications tooccur, and hopefully we will be able to prevent man yof them in the future. In the near future, specifically,enhanced understanding of the aetiology and treat-ment of the various forms of ocular NV (e.g. diabetes,macular degeneration as well as corneal) may allowmore effective pharmacological intervention of NV.A d d r e s s f o r C o r r e sp o n d e n c e2567 Amherst Avenue, Los Angeles, CA 90064, USA

14 7

D R Y E Y E A N D C O N T A C T L F ~N SWEARL CarneyImprovements in contact lenses and contact lensmaintenance over recent years have led to significantgains for practitioners and patients alike. Despite this,satisfactory management of contact lens patients ex-hibiting dry eye signs and symptoms remains difficult.Indeed, manag ement of dry eye in any patient, wheth eror not they are contact lens wearers, represents a

considerable challenge.Dry eye is a highly prevalent condition amongstcontact lens wearers. Prescribing contact lenses for apatient with recognised dry eye can exacerbate thecondition, and for a patient with a marginal condition itcan induce dry eye problems. Thus dry eye and contactlens wear are a combination which remain a challenge

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Abstracts148

t o p rac t it i oner s and a re a maj o r sou rce o f con t ac t l ensi n t o l e rance .Y e t t h e r e a r e s o m e r e a s o n a b l e g u i d e l i n e s f o ra p p r o a c h i n g m a n a g e m e n t o f t h e s e p a t ie n t s. I t is n o wc l e a r t h a t t h e d r y e y e c o n d i t i o n c a n h a v e m a n y c a u s e s ,a n d t h i s h a s l e d t o a n i m p r o v e d d r y e y e s u b t y p ec l ass i f i ca t i on . Under s t and i ng i t s r e l a t i onsh i p t o t he

b roader ocu l ar su r f ace d i seases , i nc l ud i ng con j unc t i va l ,c o r n e a l a n d l i m b a l e p i th e l iu m c h a n g e s , i n f o rm s n o t o n l yc l ass i f i ca t i on bu t a l so i t s managemen t .A d d r e s s f o r C o r r es p o n d e n c eQ u e e n s l a n d S c h o o l o f O p t o m e t r y , V i c to r ia P a r k R o a d ,Kel v i n Grove , Queens l and 4059 , Aus t r a l i a

O B S E R V I N G A N D M E A S U R I N G O C U L A R E R Y TH E M A . W H A T D O W E M E A N B Y R E D N E S S ?E PapasBackground: O b s e r v a t i o n o f e r y t h e m a p l a y s a c e n t r a lr 6 1e i n t h e a s s e s s m e n t o f t h e s t a t u s o f th e a n t e r io rsegmen t . Trad i t i ona l sub j ec t i ve quan t i f i ca t i on met hods ,s u c h a s g r a d i n g s c a l e s , a r e w i d e l y u s e d d e s p i t e a l a c k o fva l ida t ion . The r ec en t app l i ca t i on o f mo re ob j ec t i ves y s t e m s h a s o c c u r r e d w i t h o u t c o n s id e r a t i o n o f t h o s ea s p e c t s o f t h e v i s u a l s c e n e u f il is e d b y h u m a n o b s e r v e r sd u r i n g th e s u b j e c t i v e j u d g e m e n t p r o c e s s . T h e p u r p o s eo f t h is s t u d y w a s t o e s t a b l is h o b j e c t iv e l y m e a s u r a b l ec h a r a c t e r i s t i c s o f t h e c o n j u n c t i v a l v a s c u l a t u r e t h a tc o r r e s p o n d w i th t h e j u d g e m e n t o f e r y t h e m a b y h u m a no b s e r v e r s .Methods: C o l o u r i m a g e s o f b u l b a r c o n j u n c t iv a f r o m 2 1d i f f e r en t sub j ec t s were d i g i t a l l y ana l ysed t o ex t r ac tv a r i a b le s c h a r a c t e r is t i c s o f t h e s c e n e . T h e s e d a t a w e r ec o m p a r e d w i t h t h e s u b j e c t i v e j u d g e m e n t s o f a p a n e l o fs e v e n t r a i n e d o b s e r v e r s w h o i n d e p e n d e n t l y r a t e de r y t h e m a , i n th e s a m e i m a g e s , u s i n g a 0 - 4 g r a d i n g s c a l e .

Results: St rong assoc i a t i ons ( r 2> 0. 9) b e t w e e n s u b j e c -t iv e g r a d in g a n d o b j e c ti v e m e a s u r e s w e r e f o u n d f o rm o r p h o m e t r i c v a r i a b l e s d e s c r i b i n g t h e d e n s i t y o fvess e l s on t he ocu l ar su r f ace . Asso c i a t i ons fo r var i ab l esd e s c r i b i n g c o l o u r i n t h e s c e n e w e r e s u b s t a n t i a l l yweaker.

Conclusions: J u d g e m e n t s o f e ry t h e m a m a d e b y h u m a no b s e r v e r s r e l y p r i m a r i l y o n m o r p h o l o g y r a t h e r t h a nco l ou r . Th i s r esu l t has i mpor t an t i mp l i ca t i ons fo r :

( i) De s i gn o f bo t h sub j ec t i ve and ob j ec t i vem e a s u r e m e n t s y s t e m s( i i ) Tra i n i ng o f c li ni ca l obse rver s( i i i ) Approach t o da t a ana l ys i s

A d d r e s s f o r C o r r es p o n d e n c eCRCER T, Level 4 , Nor t hwi ng , R uper t My er s Bu i l d i ng ,U n i v e r s i ty o f N e w S o u t h W a l e s , K e n s i n g t o n , A u s t r a l iaN S W 2 0 52

C L IN I C A L E V A L U A T IO N O F T O R I C S O F T L E N S R E P R O D U C I B I L I T YG YoungPurpose: F r e q u e n t r e p l a c e m e n t t o r ic s o f t c o n t a c tl e n s e s a r e b e c o m i n g i n c r e a s i n g l y p o p u l a r . T h e w i d e rr a n g e o f p r e s c r ip t i o n v a r i a b l e s w i th t o r i c l e n s e s m e a n st ha t l ens r ep roduci b i l i t y i s harder t o con t ro l t han wi t hs p h e r ic a l l e n s e s . T h e p u r p o s e o f t h i s s t u d y w a s t oass ess t h e e f f ec t o f l ens r ep roduci b i l i t y on t he c l in i ca lp e r f o r m a n c e o f t h r e e d i ff e r e nt b r a n d s o f f r e q u e n tr e p l a c e m e n t t o f i c s o f t l e n se s .Method: Thi s was a t h ree-v i s i t , r andomi sed , r epea t edm e a s u r e s s t u d y in t h r e e p a r ts . I n e a c h p a r t , s u b j e c t sw e r e p r e - a d a p t e d t o t h e t e s t l e n s p r i o r t o t h r e ea s s e s s m e n t v i s i t s . A t t h e a s s e s s m e n t v i s i t s s u b j e c t sw o r e 1 2 t o r ic t e s t l e n s e s i n s u c c e s s i o n ( f ou r l e n s e s p e rv i s it ) in one eye . All 12 l ens es w ere o f t he sam el a b e ll e d p o w e r . T h e o t h e r e y e w o r e a s i n g l e l e n s w h i c hw a s r e m o v e d a n d r e i n s e r t e d b e t w e e n a s s e s s m e n t s at o t a l o f 1 2 t i m e s . T h e t h r e e f r e q u e n t r e p l a c e m e n t t o r i cso f t l enses eva l ua t ed were : Acuvue Tor i c ( e t a f i l con A) ,Foc us Tor i c (v if il con A) , and F res hL oo k Tor i c (phem-f i lcon A). A r an ge o f v i s ion , l en s f i t and sub j ec t i vev a r i a b l e s w e r e m e a s u r e d a t e a c h a s s e s s m e n t . As t a t i s t i ca l ana l ys i s t es t ed fo r d i f f e r ences i n var i ance

b e t w e e n t h e r e s u l t s fo r t h e r e p l a c e d ( te s t) a n d n o n -r e p l a c e d ( c o n t r o l ) l e n s e s . T h e r e s u l t s w e r e e v a l u a t e di n con j unc t i on wi t h in-vitro m e a s u r e m e n t s o f p r o c e s scapab i l i t y (manufac t u r i ng accu racy and r ep roduci b i l -i ty).Results: T h e F o c u s a n d F r e s h L o o k T o ri c l e n s e sshowed s i gn i f i can t l y g rea t e r var i ab i l i t y wi t h t he r e -p l a c e d l e n s e s c o m p a r e d w i t h t h e n o n - r e p l a c e d l e n s e swi t h t he fo l l owi ng var i ab l es: comfor t , t i gh t ness on push -up , overa l l f i t accep t ance , v i sua l acu i t y (h i gh and l owcon t r as0 and sub j ec t i ve v is i on qua li ty . In add i ti on , t heF o c u s T o r i c r e p l a c e d l e n s e s s h o w e d g r e a t e r v a r i a b i l i t yo f o r i en t a t ion p os i t i on and s t ab i l i t y com pare d t o non-r e p l a c e d l e n s e s . T h e A c u v u e T o r i c re p l a c e d l e n s e sshowed s i gn i f i can t l y g rea t e r var i ab i l i t y i n one var i ab l e :sub j ec t i ve v i s i on qua li ty . In a nu m be r o f case s , as i gn i f i can t l y g rea t e r var i ab i l i t y was no t ed wi t h t he non-r e p l a c e d l e n s e s w h e n c o m p a r e d t o t h e r e p l a c e d l e n s e s ,w h i c h s u g g e s t s a b a s e l i n e f o r e x p e c t e d c l i n i c a l c o n s i s -t ency .Conclusions: T h i s s t u d y h a s s h o w n d i f f e r e n c e s b e -

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9/35

Abstracts150 The hyperopic LASIK patients had an averagespherical equivalent of +2.25 _+ 1.50 D, with a sphericalcomponent averaging +2.91+1.49 D and a cylindercomponent (for all eyes) of - 1.33 _+ 1.50 D, though theasfigmats alone averaged -2.13_-t-1.53 D. The stability

of the cohort was established at 3 months, and verifiedwith the 6 month and 9 month data. At 9 months, 56%of the patients were 20/20 or better without correction,72% saw 20/25 or better, and 95% saw 20/40 or better.Seventy-four per cent were -+0.50 D, and 91% werewithin _+ 1.00 D of intended correction. No eyes lostmore than two lines of BSCVA, 4% lost two lines, andno eye had less than 20/40 BSCVA. Microkeratome-related miscreated flaps and peripheral interfaceinfiltrates both occurred in 0.8% of the patients, and0.3% (one patient) had an increase in IOP in greaterthan 10 mmHg above baseline, though no eye had an

IOP of greater than 25 mmHg at any visit. All eyes hada BSCVA of 20/25 or better, except for two eyes withmiscreated flaps which currently have a BSCVA of 20/32.Seventy-two per cent of patients felt that thei r quality

of vision had improved; 73% were satisfied with theirresults, and 89% no longer required long distance vision.LASIK results on the first eyes tr eated for myopia andhyperopia with or without astigmatism are very en-couraging with a single treatment.Updated results on the first 20 LASIK patients treatedwith the CustomCornea (wavefront-based) system alsowill be presented.

A d d r e s s f or C o r r e s p o n d e n c eRefractive Surgery Center, EENT Institute, 2626 Napo-lean Avenue, New Orleans, LA 70115, USA

CONTACT L E N S D E H Y D R A T I O N A N D L E N S A G E I N GP MorganPurpose: To investigate changes in hydrogel contactlens water content and lens comfort with wear.Methods: Six subjects wore each of four contact lenstypes (Acuvue [Vistakon], Gentle Touch [WesleyJessen], Proclear [Biocompatibles] and Freque ncy 38[CooperVision]) for 28 days. On the morning of eachday of wear, a comfort score was recorded and watercontent was measured with a hand refractometer (AtagoCL1). The same parameters were recorded at the end ofeach lens wearing day.Results: Over the 28 day period, absolute watercontent at insertion reduced for each lens type by0.12%, 0.02%, 0.05% and 0.10% per day for Acuvue,Frequency 38, Genre Touch and Proclear respec-tively. At removal, there was a day-to-day watercontent reduction of 0.14% and 0.04% for the Acuvueand Gentle Touch lenses, no change for the Proclear

lens and a day-to-day increase of 0.05% for theFrequency 38 lens. Mean+SD daily dehydrationvalues (absolute %) were 6.1_+3.0, 2.0+1.9, 3.9+2.3and 1.7 + 2.2 respectively. No changes in lens comfortover time were demonstrated. The Acuvue lens wasthe most comfortable at lens insertion and the Acuvueand Proclear lenses were the most comfortable at lensremoval.Conclusions: All four contact lenses demonstrated apermane nt and irreversible day-to-day reduction inwater content with consequent adverse effects on lensoxygen transmissibility. We demonstrated differencesbetween the lenses for daily lens dehydration andsubjective comfort scores.A d d r e s s f or C o r r e s p o n d e n c eDepartment of Optometry & Neuroscience, UMIST, POBox 88, Manchester M60 1QD

M U C I N B A L L P O S T L E N S D E B R I S I N H I G H D K S IL I C O N E H Y D R O G E L W E A R E R SL JonesPurpose: Experience with high Dk silicone hydrogellenses has revealed post-lens debris which is charac-terised by the appearance of spherical, translucentparticles referred to as 'mucin balls'. Although theseentities are easily blinked away on lens removal andappear harmless, any association with discomfort,blurred vision or adverse reactions has not beeninvestigated. The objective of this analysis was todetermine wheth er any association between mucin ballobservation and various ocular responses to contact tenswear exists.Methods: Ninety-two subjects wore lotrafilcon A lenses

on an extended wear basis for up to 30 nights and werefollowed for 6 months. Mucin balls were graded on a 0 to 4scale (0.5 increments) at three visits. Subjective ratingsand physiological response were recorded at all visits.Results: Mucin balls were observed in 70% of subjectsat one or more visits, 29% of subjects exhibited mucinballs at all three visits and there was no change inobservation frequency over time. There was a 71%concordance between eyes. Mucin balls were graded at> 1 in 18% of eyes , > 2 in 4% of eyes and > 3 in 1% ofeyes. Mucin ball appearance was not associated withany decrease in overall comfort vision or dryness and

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Abstracts ~ .~

overa l l sa t i s f ac t i on r a t i ngs were h i gh . The percen t age o fs u b j e c t s ' n e v e r ' u s i n g l u b r i c a t i n g d r o p s w a s h i g h e r i nt he sub j e c t s wi t h muci n ba l l s (P=0 .0014). No assoc i a t i onw a s f o u n d b e t w e e n b i o m i c r o s c o p i c a p p e a r a n c e , in fla m -m a t o r y r e s p o n s e s a n d m u c i n b a l l o b s e r v a t i o n .Conclusions: T h e p r e s e n c e o f m u c in b a l ls d o e s n o ta p p e a r t o b e d e t r i m e n t a l t o c o n t a c t l e n s w e a r . F u t u r e

i nves t i ga t i on i n t o t he r e l a t i onsh i p be t ween muci n ba l lo b s e r v a t i o n a n d t h e u s e o f r e - w e t t i n g d r o p s i sw a r r a n t e d .A d d r e s s f o r C o r r e sp o n d e n c eCCLR, Schoo l o f Op t omet ry , Un i ver s i t y o f W at er l oo ,On t ar i o N2L 3GI , Canada

151

A S T U D Y O F T H E S P O I LA T I O N P R O F I L E S O F H I G H D k F L U O R O S IL I C O N E H Y D R O G E L L E N S E SV Frankl i nT h e s p o i l a ti o n p r o f i le s o f h i g h D k f l u o r o s i li c o n eh y d r o g e l s w o r n f o r 3 0 n ig h t s, e i t h e r w e e k l y r e p la c e -m e n t o r c o n t i n u o u s l y , w e r e a s s e s s e d u s i n g f l u o r e s -c e n c e s p e c t r o p h o t o f l u o r i m e t r y a n d u l tr a - v io l e tspec t roscopy . At l eas t 35 pa t i en t s were i nvo l ved i nt h e s t u d y a n d l e n s e s w e r e c o l l e c t e d a t t h e 6 , 9 a n d 1 2mon t h po i n t i n t he t r i a l . I n fo rmat i on was ob t a i ned onsu r face and l i p i d depos i t i on on t he f ron t and back o ft he l ens , as wel l as t o t a l p ro t e i n up t ake . The r esu l t so b t a i n e d w e r e c o m p a r e d t o t h e r e s u l t s f o r a r a n g e o ff r e q u e n t r e p l a c e m e n t c o n t a c t l e n s e s , w h i c h h a d b e e nu s e d o n a d a i ly w e a r b a s i s . T h e f l u or o s il i co n e h y d r o g e le x t e n d e d w e a r m a t e ri a l h a d t h e l o w e s t p r o t e in d e p o s i -t i on o f a l l t he l e nses t es t ed , a nd t he p ro t e i n r ema i neda t t h e s u r f a c e o f t h e l e n s r a t h e r t h a n b e i n g a b s o r b e di n t o t he bu l k o f t he l en s mat r i x . Th e l ip id depos i t i onwa s wel l w i t h i n t he l i mi t s o f t he l ev e l s obse rve d fo r t he

da i l y we ar l enses , su r f ace t o bu l k p ro t e i n an d l ip idr a t i o s w e r e a l s o d e t e r m i n e d b y p l a s m a e m i s s i o n a n dm o n i t o r i n g ( P E E M S ) a n d h i g h p e r f o r m a n c e l i q u i dc h r o m a t o g r a p h y ( H P L C ) . N o d i f f e r e n c e s w e r e f o u n db e t w e e n t h e s p o i l a t i o n p r o f i l e s i n t h e t w o w e a rmodal i t i es , we ek l y r ep l ac em en t fo r 30 n i gh t s , o r 30n i g h t s c o n t i n u o u s l y . A l t h o u g h i n d i v i d u a l p a t i e n t ss h o w e d l e f t t o r i g h t e y e v a r i a b il i ty , o v e r a l l n od i f f e r e n c e s i n t h e a c c u m u l a t e d r e s u l t s w e r e o b t a i n e d ,a s w a s a l s o t h e c a s e b e t w e e n t h e f r o n t a n d b a c ksu r face depos i t i on . The l i p i d p ro f i l e was much morepa t i en t dependen t t ha t t he p ro t e i n depos i t i on , bu t s t i l ld r i ve n b y m a t e r i a l /s u r f a c e c o n s i d e r a ti o n s .A d d r e s s f o r C o r r e s p o n d e n c eAst on B i omat er i a l s Research , As t on Un i ver s i t y , As t onT r i a n gl e , B i r m i n g h a m B 4 7 E ~

M U L T I F O C A L A N D B I F O C A L C O N T AC T L E N S P E R F O R M A N C E I N C O M B I N A T I O N W I T H AU N I O C U L A R T O R IC L E N SK Fi sherA s t i g m a t s a r e o f t e n c o n s i d e r e d m a r g i n a l c a n d i d a t e s f o rp r e s b y o p i c c o r r e c t i o n w i t h s i m u l t a n e o u s v i s i o n c o n t a c tl enses .Purpose: The goa l was t o eva l ua t e v i sua l per fo r -m a n c e a n d w e a r e r a c c e p t a n c e w h e n a b i f o c a l o rmul t i foca l l ens i s pa i r ed wi t h a un i ocu l ar s i ng l e-v i s i ont o r i c l ens .Methods: T w e n t y - t w o p r e s b y o p e s w i t h v a r y i n g d e g r e e sof pre sby op ia (Add +0.50 to +2.50 D) and s igni f icantr e f ra c t iv e c y li n d e r ( - 0 . 7 5 t o - 2 . 2 5 D ) in o n e o r b o t he y e s w e r e e a c h f it te d w i th a u n i o c u l a r t o r ic l e n s i ncombi na t i on wi t h b i foca l and p rog ress i ve mu l t i foca ll e n s e s f o r t h e c o n tr a la t e ra l e y e . E a c h c o m b i n a t i o n o fl e n s e s w a s w o r n f o r 2 - 7 d a y s , a t w h i c h t i m e f i t ti n g w a sr e f in e d a n d t h e l e n s e s w o r n f o r a n o t h e r 3 - 7 d a y s .T e s t i n g e n c o m p a s s e d b i n o c u l a r d i s t a n c e a n d n e a rcon t r as t sens i t i v i t y and h i gh / l ow ambi en t i l l umi na t i onacu i t i es , as wel l as nearpo i n t s t e r eoacu i t y , b i nocu l arv i sua l r ange , and hand-eye co -o rd i na t i on . Vi sua l symp-t omat o l ogy , comfor t , hand l i ng , ghos t i ng , and sub j ec t i vev i sua l qua l i t y were a l so eva l ua t ed .

Results: P e r f o r m a n c e d e f i c i t s r e l a t i v e t o s p e c t a c l e sw e r e s i g n i f i c a n t l y g r e a t e r w h e n w e a r i n g s i m u l t a n e o u sv i s i o n l e n s e s o n b o t h e y e s t h a n w h e n w e a r i n g o n e s u c hl e n s a l o n g w i t h a u n io c u l a r t o ri c l e ns . W h e n c o m b i n e dw i t h a t o r i c l e n s , t h e p r o g r e s s i v e m u l t i f o c a l o u t -p e r f o r m e d t h e b i fo c a l w i t h r e s p e c t t o d i s t a n c e a c u i ty ,l ow i ll umi na t ion nea r acu i t y , con t r as t sens i ti v it y , s t e r eo -acu i t y , and eye-hand co -o rd i na t i on . The mul t i foca l / t o r i ccombi na t i on was r a t ed h i gher fo r overa l l v i sua l qua l i t y ,a s s o c i a t e d w i t h f e w e r a n d l e s s s e v e r e v i s u a l p r o b l e m s ,a n d w a s p r e f e r r e d b y t h e m a j o r it y o f t h e s u b j e c t si nc l ud i ng t hose p rev i ous l y we ar i ng m onof i t s i ng l e v is i onl e n s e s .Conclusion: Pai r i ng a p rog ress i ve mu l t i foca l l ens wi t ha un i ocu l ar t o r i c l ens shou l d be t r i ed p r i o r t o o t hero p t i o n s w h e n a t t e m p t i n g t o f i t a p r e s b y o p i c a s t i g m a twi t h so f t con t ac t l enses .Futu re Studies: Var i ous mu l t i foca l and b i foca l des i gnsm u s t b e c o m p a r e d t o d e v e l o p a c o m p r e h e n s i v es t r a t egy fo r success fu l l y f i t t i ng t h i s t ype o f con t ac tl ens pa t i en t .



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Abstracts152

A d d r e s s f o r C o r r e s p o n d e n c eCIBA Vi s ion Corpora t ion , 11460 Joh n ' s Cre ek Parkw ay ,Duluth , GA 30097, US A

M A N A G I N G C O R N E A L IN F IL T R A T E S IN P A T I E N T S W I T H H I G H D k E X T E N D E D W E A R L E N S E SR ChalmersW h i l e t h e h y p o x i c c h a n g e s p r e v i o u s l y a s s o c i a t e d w i t hE W h a v e b e e n e l i m i n a t e d w i t h n e w H i g h D k l e n s e s ,some pa t i en t s have exper i enced t r ans i en t ocu l ar i n f l am-mat ion . Th i s t a l k ou t l i nes t he case h i s t o ry and manage-m e n t o f t h r e e p a t ie n t s w h o d e v e l o p e d c o r n e a l i n f il tr a te s

o f vary ing seve r i t y wh i l e we ar ing l o tr a f il con A l enses .A d d r e s s f o r C o r r e s p o n d e n c eCIBA Vi son Corp , 11460 John ' s Cr eek P arkway , D u lu th ,GA 30097, USA

W A V E F R O N T S E N S I N G T E C H N O L O G Y - V I S I O N C O R R E C T I O N F O R T H E N E W M I I .I .E N I U MR PotvinA d a p t iv e o p t ic s , t h e t e c h n o l o g y d e s i g n e d t o p r o v id e f o ra t m o s p h e r i c c o r r e c t io n o f t e l e s c o p e s , h a s i ts e l f b e e nadap t ed - t o t he hum an eye . Th e r esu l t i ng ab i li t y t om e a s u r e h i g h e r o r d e r a b e r r a ti o n s o f t h e h u m a n e y eho lds i ncred ib l e po t en t i a l. App l i ca t ion o f t h i s t ech no log y

to var i ous fo rm s o f v i s i on co r rec t i on wi ll be d i s cuss ed .A d d r e s s f or C o r r e s p o n d e n c eB a u s c h & L o m b , 1 4 00 N G o o d m a n S t r e e t , P O B o x 4 5 0,Roch es t e r , NY 14603-0450 , USA

C O N T A C T L E N S D R Y E Y E . . . T H E P R O B L E M T H A T W O N ' T G O A W A YJ CraigC o n t a c t le n s i n d u c e d d r y e y e i s b y f a r a n d a w a y t h em o s t c o m m o n r e a s o n f o r c o n t a c t l e n s d r o p - o u t i np rac t i ce . Th i s l ec tu re wi l l d i scuss bo th t he env i ron -men ta l , as wel l as t he c l i n i ca l p rob l em su r round ing t h i sp e r p l e x i n g p h e n o m e n o n . I t w i l l c o n c l u d e b y p u t t i n gf o r w a r d a m a n a g e m e n t s t r a t e g y t o r e d u c e t h e i n c i -

d e n c e o f c o n t a c t l e n s d r o p - o u t f r o m d r y e y e , in y o u rp rac t i ce .A d d r e s s f o r C o r r e s p o n d e n c eDisc ip l i ne o f Oph tha lmology , Un iver s i t y o f Auck l and ,Pr iva t e bag 92019, Auck l and 1001 , Ne w Zeal and

T H A T 'S N O T W H A T I W A S T A U G H T A T U N I V E R S I T Y !J MeylerC o n t a c t l e n s p r a c t i c e i s o n e o f th e m o s t r a p i d l ychang ing f i e l d s wi th in ou r p ro fess ion and updat i ng ou rknowledge i s fundamen ta l i n a l l owing op t imal pa t i en tcare . Th i s p resen t a t i on wi l l r ev i ew changes t o ou rm a n a g e m e n t a p p r o a c h o n a n u m b e r o f e v e r y d a y c lin ic alp r o b l e m s b a s e d o n m o r e r e c e n t c o n t a c t l e n s r e s e a r c h

a n d r e m i n d u s t h a t p r e v e n ti o n i s o ft e n t h e b e s t f o r m o fm a n a g e m e n t .A d d r e s s f or C o r r e s p o n d e n c eV i s t a k o n U K - J o h n s o n & J o h n s o n , T h e B r a c c a n s ,L o n d o n R o a d , B r a c kn e l l, B e r k s R G 1 2 2 A T

A D A P T A T I O N A N D R E S IS T A N C E O F P S E U D O M O N A S A E R U G I N O S A T O C ON T AC T L E N SD I S I N F E C T I O NC LakkisPurpose: Res i s t an ce o f bac t e r i a t o con t ac t l ens d i si n-f ec t i on so lu t i ons appear s t o p l ay a r61e i n i ncreas ingt h e e x p o s u r e o f t h e e y e t o m i c r o -o r g a n i s m s d u r i n gl e n s w e a r . W e h a v e r e p o r t e d v a r i a b i l i t y a m o n g P .Aeruginosa s t r a i n s i n t h e i r s u s c e p t i b i l i t y t o t w oh y d r o g e l c o n t a c t l e n s c h e m i c a l d i s i n f e c t a n t s a n d h a v ef o u n d r e s i s t a n c e t o c o r r e l a t e w i t h g e n e s i n v o l v e d i ncy to tox i c i t y t owa rds c o rnea l t o e p i t he li a l ce l ls . Wh en

cy to tox i c P . Aeruginosa s t r a i n s w e r e e x p o s e d t o ad i s i n f e c t a n t p r e s e r v e d w i t h P O L Y Q U A D , i n t h e c o n -t a c t l e n s c a s e a t r o o m t e m p e r a t u r e , 4 / 6 s t ra i n s g r e wto l eve l s abo ve t he i ni ti al i no cu lum af t e r 24 t o 48 h .T h e a i m o f t h is s t u d y w a s t o d e t e r m i n e w h e t h e r t h i sg row th i s due t o ada p t a t ion o f t he cy to tox i c s tr a i n s t othe d i s i n fec t an t .



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Methods: The cytotoxic P. Aerug inosa strain PAl03 wasused to inoculate the POLYQUAD preserved disinfec-tant in the lens case environment, to give an initialinoculum of 107 CFU/ml. Cases were kept at roomtemperature (22C) for 7 days. The solution within thelens case, containing surviving PAl03 (pre-exposedPAl03), was then used to inoculate fresh disinfectantwhilst the remaining solution was filter sterilised andchallenged with pre-exposed PAl03 and a new inoculumof PAl03 (unexposed PAl03). Unexposed PAl03 as alsoused to inoculate flesh solution. Cases were stored at22C and viable counts performed at 4, 18, 24, 48 and168 (7 days) h post-inoculation.Results: An initial inoculum of approximately 106 CFU/ml was achieved. When the growth of unexposed andpre-exposed PAl03 was compared in fresh disinfectant,the pre-exposed PAl03 showed statistically significantlyhigher levels of growth at all time points from 4 h to 7

days. When the growth of unexposed PAl03 wascompared between the filtered and flesh disinfectant,inhibition of growth was observed in the filteredsolution.Conclusions: Inhibition of the growth of unexposedPAl03 in filtered compared to fresh solution suggeststhat the growth of cytotoxic strains in POLYQUADpreserved disinfectant is a result of adaptation to thedisinfectant and/or the low nutrient environment of thecontact lens case. This adaptation may influencevirulence factors such as adherence (both to the contactlens and the corneal epithelium), epithelial cell invasionand cytotoxicity, contributing to the development ofinflammatory and infectious complications.A d d r e s s f o r C o r r e s p o n d e n c eUniversity of California, Berke ley School of Optometry,#688 Minor Hall, Berkeley CA 94700-2020, USA

153

S E V E N- D A Y E X T EN D E D W E A R A N D 3 0 - D A Y C O N T I N U O U S W E A R O F S O F T C O N TA C T L E N S E SW I T H V E R Y H IG H O X Y G E N TR A N S M I S S IB I L IT Y . A S T U D Y O F 5 0 0 P A T I E N T SSE Ni lssonBackground and Method: New silicone hydrogel con-tact lenses with an oxygen transmissibility (Dk/0 3- 5times that of current soft lenses may reduce the risk ofmicrobial keratitis. Cavanagh and his group showed thatbacterial binding to exfoliated corneal epithelial cellsafter overnight wear of contact lenses was inverselyrelated to tens Dk/t. However, the new high Dk/t softlenses did not increase binding at all over no lens wear. Ina 1-year study, a high Dk /t soft contact lens (BalafilconA) was teste d in 150 patients for 7-day extended wear andin 350 patients for 30-day continuous wear.Results: No sight threatening complications, e.g. bac-terial keratitis, occurred. Limbal and bulbar injectiondecreased significantly. Positive slit lamp findingsrelated to lens wear were seen in 24% of the eyes,primarily as sl ight corneal staining (11%), and to a muc hless extent also as sterile peripheral infiltrates, tarsalconjunctival abnormalities, CLARE and SEAL with nosignificant difference between the two groups. Most

infiltrates did not stain and healed upon a shor t period ofdiscontinued lens wear. Thirteen per cent of the patientsin the 7-day group and 8% in the 30-day group did notcomplete the study for reasons related to lens wear, e.g.because of discomfort or sterile peripheral infiltrates,with no significant difference between the two groups.The patients' subjective judgement of comfort, visualquality, freedom from dryness and handling varied from89 to 95 on a scale from 0 to 100.Conclusions: It seems that the new high Dk/t softcontact lenses may reduce serious complications suchas microbial keratitis. Inf lammatory reactions such assterile peripheral infiltrates are still seen. The 30-daygroup did not show more complications than the 7-daygroup.A d d r e s s f o r C o r r e s p o n d e n c eDepartment of Ophthalmology, LinkSping University,HnkSping, SE-581 85, Sweden

B A C TE R IA L P O P U L A T I O N S P R E S E N T D U R I N G E X T E N D E D W E A R O F C O N T A C T L E N S E SC Morr i sBacterial contamination of contact lenses duringwear has been demonstrated in asymptomaticwearers 1 and may contribute to CL-related infectionand inflammation. Microbial keratitis occurs morecommonly in extended wear (EW) compared todaily wear (DW) use of CLs. 2-4 The aim of thisstudy was to evaluate the bacterial contaminationrate during EW over a much longer wear cycle (30NEW), now possible with the introduction of highly

oxygen permeable soft materials. For this purpose,FocusR NIGHT and DAY M (a fluorosfloxane basedpolymer, 24% H20, Dk /t of 175 barrers/ cm) wasused. Two hundred and eighty-four lenses wereaseptically collected at various time points from aDW, six NEW and 30 NEW patient group andplaced in 2 ml PBS. After sonication, each lens wascultured, and a portion of the sonicated solutionwas plated out on a variety of media and grown



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~ . ~ A b s t ra c ts15 4 under d i f f e ren t cond i t i ons , a l l des igned t o max imi se

t h e c h a n c e s o f p i c k in g u p o r g a n i s m s p r e s e n t o n th el ens . The r emain ing so lu t i on was s t o red a t 5 C andf i lt e r ed i f l ense s exh ib i t ed no g ro wth . T he f i lt e r wa sthen p l a t ed t o es t ab l i sh l ens s t e r i l i t y . Bac t er i a lp o p u l a t i o n s p r e s e n t o n t h e l e n s a t a n y g i v e n t i m ep o i n t w e r e n o t d i f f e r e n t , a n d w e r e m o s t l y n o r m a lsk in f l o ra . More impor t an t l y , t he percen t age o fs t e r i l e l e n s e s w a s t h e s a m e d u r i n g t h e w e a r c y c l e ,a n d t h e r e w a s n o s i g n i f i c a n t i n c r e a s e i n t h e n u m b e ro f o r g a n i s m s p r e s e n t o n d a y 1 t h r o u g h t o d a y 30 .

T h e i m p l ic a t io n s o f t h e s e f i nd i n g f o r 3 0 N E W w i llb e d i s c u s s e d .R e f e r e n c e s :I Gopinathan et a l . J . App l . Micro b io l . , 8 2 , 1 - 7 ( 1 9 9 7 ) .Sc h e i n e t a l . N . E n g l . J . M e d . , 3 2 1 , 7 7 3 - 7 7 8 ( 1 9 8 9 ) .a Stap le ton e t a l . C L A O ] . , 1 9 , 2 0 4 -2 1 0 (1 9 9 3 ) .4 C h e n g e t a l . L a n c e t , 5 4 , 1 7 9 -1 8 3 (1 9 9 9 ) .A d d r e s s f o r C o r r e sp o n d e n c eC I B A V i s io n C o r p , 1 1 46 0 J o h n ' s C r e e k P a r k w a y ,Duluth , G A 30097, USA

T H E I M P L I C A T I O N S O F v C J D F O R C O N T A CT L E N S P R A C T I C EG M aca l i s terT h e a i m o f t h i s p r e s e n t a t i o n i s t o p r o v i d e t h ep rac t i t ioner w i th an ov erv i ew o f t he r i sks o f t r ansmi s -s i on o f var i an t Creu t zfe ld t - Jakob d i sea se (vCJD) f romp e r s o n t o p e r s o n v i a c o n ta c t l e n s e s ( a n d o t h e r d e v i c e swhich con t ac t t he eye) . I t w i l l h igh l i gh t t he f ac t s t ha th a v e b e e n e s t a b l is h e d , f o c u s i n g o n t h o s e a s p e c t s o f t h es c i e n t i f i c b a c k g r o u n d t h a t a r e f u n d a m e n t a l t o a nin fo rmed v i ew. The gaps i n t he sc i en t i f i c knowledge ,and t he i r imp l i ca t i ons , wi l l be po in t ed ou t . Referencewi l l a l so be made t o s t ud i es t ha t a r e cu r ren t l y i np r o g r e s s , t h e r e s u l t s o f w h i c h m a y c h a n g e o u r o u t lo o k .Prion biology: A br i e f ou t l i ne o f p r ion b io logy wi ll beg iven . Th i s w i ll concen t r a t e on t he exp l ana t i on o f them os t r e l evan t po in ts , fo r example t he l ack o f e f f ec t ived e c o n t a m i n a t io n m e t h o d s , a n d t h e e x i s t e n c e o f d if f e re n ts t r a in s o f p r i on , wi th d i s t i nc t b io log i ca l p roper t i es ,w h i c h c a n a l t e r w h e n t h e d i s e a s e c r o s s e s a s p e c i e sbarr ier .Transmission: T h e r e a r e t h r e e k e y q u e s t i o n s . F i r s t l y ,wi l l i n fec t i ous p r i ons be p resen t i n t ear s and a t t heocu l ar su r f ace t i s sue s o f pa t i en t s wh o are i n t he ear l yp re-c l i n i ca l s t ages o f CJD? Second ly , i s i t poss ib l e t ot r a n s fe r t h e s e p r i o n s t o a n o t h e r e y e v i a c o n t a c t le n s e s ?Th i rd ly , cou ld t hese p r i ons t hen i n fec t t he b ra in o f t hes e c o n d i n d iv i d ua l b y p a s s a g e f r o m t h e o c u l a r s u r fa c et i s s u e s ? S c i e n ti s ts c a n n o t y e t p r o v i d e e x a c t a n s w e r s t o

t h e s e q u e s t i o n s , b u t i n d i r e c t e v i d e n c e , m a i n l y f r o man imal s t ud i es , po in t s t oward t he l i ke l i hood t ha t sucht r a n s m i s s i o n m a y b e t h e o r e t i c a l l y p o s s i b l e . If w ea c k n o w l e d g e t h a t t h e r e i s s o m e r i s k , h o w e v e r , s m a l l ,o f t r ansm i ss ion v i a con t ac t l enses , w e are t he n l e f t wi tht h e m o s t i m p o r t a n t q u e s t i o n . H o w l i k e ly a r e w e t oe n c o u n t e r a p e r s o n i n f e c t e d w i t h vCJD i n ou r p rac t i ce?I t i s n o w c l e a r th a t t h e p r io n s t r a in w h i c h c a u s e s B S E i nca t t le i s i den t i ca l to t he one foun d i n hum ans wi th vCJD.k fo l l ows t ha t m i l li ons o f peop l e i n t he UK cou ld haveb e e n e x p o s e d t o th e v C J D a g e n t i n t h e l a t e 1 9 8 0 's b e f o r ei n f e c t e d m a t e r i a l w a s p r e v e n t e d f r o m e n t e r i n g t h e f o o dc h a in . V e r y f e w p e o p l e a r e k n o w n t o h a v e c o n t r a c t e dvCJD so f a r , bu t ep idemio log i s t s a r e unab l e t o p red i c tt h e f u t u r e s c a l e o f t h e o u t b r e a k .Discussion: Thi s r ev i ew wil l d i scu ss t he e th i ca l con -cerns t ha t a r i se f rom the uncer t a in , bu t po t en t i a l l y veryser i ous , r i sk o f t r ansm i ss ion o f vCJD v i a con t ac t l enses .R e f e r e n c e w i ll b e m a d e t o o t h e r i n t e rv e n t i on s t h a t c o u l dhave t he po t en t i a l fo r c ross - i n fec t i on , and t he r eac t i onso f o ther p ro fess iona l g roups wi l l be r epo r t ed . In add i t i ont o t h e c u s t o m a r y o p p o r t u n i t y t o p o s e q u e s t i o n s , i t i shoped t ha t de l ega t es wi l l be ab l e t o u se i n t e rac t i veh a n d s e t s t o v o t e o n s o m e o f t h e i s s u e s r a i s ed .A d d r e s s f o r C o r r e s p o n d en c eF i n g e l l a n , W h i n e s L a n e , C a m b r i d g e s h i r e C B 4 5 P T

Contact Lensand AnteriorEy e


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A b s t r a c t s

P O S T E R P R E S E N T A T IO N S

J u r a s s i c s c l e r a l s , a t h i n g o f t h e p a s t ?J Lamb, BRyan, T Sabell and W IllahiAim: T h e a i m o f t h is p o s t e r i s to s h o w i n a s t e p b y s t e pp r a c t i c a l f o r m h o w s i m p l e i t c a n b e t o m a k e a n e y ei m p r e s s i o n , p r o d u c e a P M M A s h e l l a n d s u b s e q u e n t l yadjust and f i t i t .Objective: T h e o b j e c t iv e s a r e to r e m i n d p r a c t it i o n e rst h a t w h e n t h e y a r e d e a l i n g w it h a c o r n e a w h i c h a p p e a r si mpo ss i b l e t o f it w i t h a co rnea l con t ac t l ens ( a con t ac tl ens be i ng t he on l y wa y o f op t i ca ll y co r r ec t i ng i t) ani m p r e s s i o n P M M A s c l er a l l e n s m a y b e t h e m o s ts u c c e s s f u l a n d s i m p l e s t o p t i o n . I t w i ll a l s o g i v ep r a c t i t i o n e r s t h e o p p o r t u n i t y t o s e e a n d t o u c h P M M Ascl era l l enses , eye cas t s , mat er i a l s and o t her p rac t i ca ltools of scleral lens f i t t ing .Method and Materials: T h e p o s t e r s h o w s a s t e p b y s t e pp rac t i ca l gu i de t o t ak i ng an eye i mpress i on , mak i ng apos i t i ve cas t and an i n i t i a l PMMA she l l , g r i nd i ng andedg i ng i t, and f i na ll y t he n ear f i n i shed pow ered l ens .Conclusion: W e s e e h o w u s e f u l t h e P M M A s c le r a l l e n sf r o m i m p r e s s i o n c a n b e a n d h o w r e l a t i v e l y s i m p l e a n dc o s t e f f e c ti v e it c a n b e t o p r o d u c e t h e m .A d d r e s s f o r C o r r e s p o n d en c eB i r m i n g h a m & M i d l a n d s E y e C e n t r e , C i t y H o s p i t a lN H S T r u s t , D u d l e y R o a d, B i rm i n g h a m B 1 8 7 Q U

C l i n i c a l e v a l u a ti o n o f a d e s i g n o f g a s p e r m e a b l es c le r a l c o n t a c t l e n s e s o v e r a t h r e e y e a r p e r i o dW Illahi, B Ryan, T SabeU and J LambThe aim of t h i s po s t e r i s t o r epo r t a 3 -year updat e o f t heo u t c o m e o f a ll t h e c o r n e a s w h i c h w e r e f i t te d w i t h g a sp e r m e a b l e s c l e ra l l e n s e s i n t h e B i r m i n g h a m & M i d l a n dE y e C e n t r e .Objectives: T h e o b j e c t iv e s a re t o i n d e p e n d e n t l y e v a lu -a t e t h e s u c c e s s r a t e o f R G P s c l e r al l e n s e s d e s i g n e d b yInnova t ive Sclerals Ltd . on di f f icul t ey es an d to out l inep r o b l e m s w h i c h m a y b e e n c o u n t e r e d .Method: F o r t y - e i g h t e y e s w e r e f i t t e d w i t h p r e f o r m e dr ig i d g a s p e r m e a b l e s c l e r a l l e n s e s b e t w e e n J a n u a r y1 99 6 a n d D e c e m b e r 1 9 99 a t t h e B i r m i n g h a m & M i d l a n dEye Cen t r e . A l l f i t t i ngs were done acco rd i ng t o t hemanufac t u rer ' s spec i f i ca t i on . Pa t i en t s were fo l l owed-upa n d o u t c o m e s r e c o r d e d .

Conclusion: G a s p e r m e a b l e s c l e r a l l e n s e s a r e a v i a b l eo p t io n f o r a la r g e n u m b e r o f p a t i e n ts w h o a r e n o ts u i ta b l e f o r a n y o t h e r t y p e o f l e n s i n c l u d in g P M M A

s c l e r a l l e n s e s . S o m e p a t i e n t s w e r e f o u n d t o b eu n s u c c e s s f u l i n t h e l o n g e r t e r m , t h e m a i n r e a s o n sb e i n g h a n d l i n g d i f f i c u l t i e s , s o l u t i o n i n t o l e r a n c e o rexc ess i ve l y t o ro i da l sc l e r a .

A d d r e s s f o r C o r r e s p o n d e n c eB i r m i n g h a m & M i d l a n d s E y e C e n t r e, C i t y H o s p i t a lN H S T r u s t , D u d l e y R o a d , B i r m i n g h a m B 1 8 7 Q U

G a s p e r m e a b l e m a t e r i a l s e n a b l e p r e d i c t a b l e s c l e r a ll e n s f it ti n g p r o c e s s e sK PullumT h e p u r p o s e o f t h i s p r e s e n t a t i o n i s to i l lu s t ra t ecu r ren t sc l e r a l l ens f i t t i ng t echn i ques i n t he manage-m e n t o f h i g h r e f r a c t iv e e r r o r s , a b n o r m a l o c u l a rt o p o g r a p h y a n d o c u l a r s u r f a c e d i s o r d e r s . T h e t h e o r yand p rac t i ce o f sc le r a l l ens f i t t ing a re i l l u s t r a ted i nv a r i o u s e x a m p l e s o f ty p i c al e y e c o n d i ti o n s w h e r esc l e ra l l enses a r e i nd i ca t ed . F i t t i ng p rocesses haveu n d e r g o n e a t r a n s f o r m a t i o n s i n c e t h e i n t r o d u c t i o n o fg a s p e r m e a b l e m a t e r i a l s . F e n e s t r a t e d d e s i g n s w e r en e c e s s a r y t o a l l o w s o m e f r e s h o x y g e n a t e d t e a re x c h a n g e w i t h P M M A s c l e r a l l e n s e s , b u t a d m i t t e dbubb l es t o t he p re-co rnea l f l u i d r eservo i r and l ead t ose t t l i ng back on t he g l obe . Bo t h were s i gn i f i can tp r o b l e m s , m a k i n g s c l e r a l l e n s f i t t i n g a c u m b e r s o m eand unpred i c t ab l e exerc i se . B ub b l e s have t r ad it i ona ll yb e e n u s e d t o d e f i ne t h e q u a l it y o f f e n e s t r a t e d s c l e r a ll ens f i t t i ng , bu t a r e i nappropr i a t e fo r assessmen t nowt h a t t h e g r e a t m a j o r i t y o f e y e s c a n b e f i t t e d u s i n gs e a l e d d e s i g n s w i th R G P m a t e r ia l s . T h e d e p t h o f t h ep re-co rnea l f l u id r eservo i r and t he qua l i t y o f co rnea lc o n t a c t z o n e s a r e t h e k e y f e a t u r e s t o e v a l u a te a s b o t hhave a s i gn i f i can t bear i ng on bo t h t o l e r ance t o l ensesand v i sua l per fo rmance .A d d r e s s f o r C o r r e s p o n d e n c e2 0 3 W a r e R o a d , H e r tf o r d , H e r t s S G 1 3 7 E Q

N o m o g r a m f o r f it ti n g k e r a t o c o n i c e y e s u t i l i s i n gc o m p u t e r i s e d v i d e o - k e r a t o s e o p yLG Sorbara and J LuongPurpose: T o d e t e r m i n e a fi tt in g n o m o g r a m r e la t in g t h ec o r n e a l c u r v a t u r e m e a s u r e m e n t s o f k e r a t o c o n i c e y e s , t ot he b ack op t i c zone r ad i us (BOZR) o f t he f i nal l ensdes i gn .Methods: F i f ty - s e v en k e r a t o c o n i c e y e s w e r e f it te d w i t ha t r i cu rve , mu l t i cu rve o r Rose-K ri g i d gas perm eab l e( RG P ) l e n s . S u b j e c t s w e r e n o m i n a ll y g r o u p e d b y t h ea m o u n t o f c o r n e a l a s t i g m a t i s m ( d e l ta K ) : l o w( - 2 . 0 5 D + - 0 . 9 1 , n =1 7) , m o d e r a t e ( - 5 . 6 5 D _ +- 1 . 2 1 , n= 24 ) a n d h ig h ( - 1 0 . 9 7 D + - 3 . 1 3 , n =1 6).The l enses were f i t t ed by t r i a l l ens f i t t i ng t o ach i eve at radi t ional three-point , minimal apical touch f i t . Once

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156 f i t t ed , t he r e l a t i onsh i ps be t ween t he cen t r a l t opograph i -c a l r e a d i n g s , a m o u n t o f c o rn e a l a s t i g m a t is m , s t e e p e s tt o p o g r a ph i c a l r e a d i n g a t t h e a p e x o f t h e c o n e a n d t h ef ina l BOZR s we re s t ud i ed t o e s t ab l i sh a fi tt ing nomo-g r a m .Results: Th e BOZ Rs we re s i gn i f i can tl y d i ff e r en t fo re a c h a s t i g m a t i c c a t e g o r y ( P < 0 . 0 5 ) . A l l l e n s e s w e r ef i t t ed s t eeper t han t he cen t r a l f i a t K . The fo rmul aees t ab l i she d were : l ow cy l am oun t s : BOZR=fl at K(D)- 0 . 6 0 9 ( d e lt a K ); m o d e r a t e c y l a m o u n t s : B O Z R = -f i at K(D) -0 .4 1 9 (de l ta K) ; h i gh cy l amo un t s :BOZR=f i a t K(D) -0 .3 54 (de l ta K) . Th e ap i ca l ands t e e p e s t re a d i n g s a s m e a s u r e d b y t h e t o p o g r a p h e rd i d no t p rov i de as p red i c t ab l e a r e l a t i onsh i p wi t h t hef ina l BOZR, espec i a l l y fo r t he h i gh cy l i nd ri ca l g roup(ste epe st K's of 68.58 D_+6.00, n--16) . For th e lowa n d m o d e r a t e a s t i g m a t i c g r o u p s , t h e l e n s e s w e r ef i t ted b e t w ee n 6 .25 and 7 .57 D f l a t t e r than t hes t ee pes t K . K t he a verage o f t he cen t r a l f ia t ands t e e p e s t a p i c a l K r e a d i n g w e r e u s e d a s t h e s t a r t i n gBOZ R, the in it ial l e ns w ou ld b e 3 .0 to 7 .0 D toos t eep .Conclusions: T h e u s e o f c o r n e a l t o p o g r a p h e r s i nd i a g n o s i n g e a r ly k e r a t o c o n u s h a s b e e n w e l l e s t a b l i s h e dand s t ud i ed . P red i c t i ng t he i n i t i a l and / o r f i na l con t ac tl e n s p a r a m e t e r s b y u s i n g t h i s f it ti n g n o m o g r a m w il le m p h a s i s e t h e i m p o r t a n c e o f i n t e g ra t i n g c o r n e a l t o p o -g raphy i n t o con t ac t l ens p rac t i ce .A d d r e s s f o r C o r r e s p o n d e n c eSchoo l o f Op t om et ry , Un i ver s i t y o f W at er l oo , Wat er l oo ,On t ar i o N2L 3G1 , Canada

A k e r a t o c o n u s c o r n e a l l e n s f it ti n g t e c h n i q u e u s i n gl i n e a r a x i a l p r o f i l e i n c r e m e n t sKW Pullum and K MurphyKe ra t om et ry i s u sed as a gu i de t o se l ec t i on o f t he i n it ia ll ens i n kera t oconus bu t t he f i na l op t i mum spec i f i ca t i onof t en bear s l i t t l e r e l a t i onsh i p t o t he co rnea l cu rva t u re i nm o d e r a t e o r a d v a n c e d s t a g e s o f t h e c o n d it io n . F u r t h e rd a t a m a y b e g a i n e d f r o m c o r n e a l t o p o g r a p h y m a p p i n g ,b u t t h e p r e d i c t i v e v a l u e r e m a i n s q u e s t i o n a b l e . T h i sp r e s e n t a t io n d e s c r i b e s h o w t h e c e n t r a l c u r v a t u r e a n dt he asp her i c per i phera l con f i gu ra t i on o f t he l ens a r ei n t eg ra t ed t o g i ve a s i ng l e paramet er , t he ax i a l p ro f i l e .T h i s i s v a r i e d i n e q u a l i n c r e m e n t a l s t e p s a c r o s s t h erange enab l i ng a s i mp l i f i ed , s t r a i gh t fo rward and h i gh l yp red i c t ab l e app roa ch t o kera t oco nus f it ti ng . E xam pl es o fkera t oco nus f i tt i ngs il l u s tr a t e b y use o f c li ni ca l pho t o -g raphy how ax i a l p ro f i l e var i a t i ons change t he c l i n i ca la p p e a r a n c e , h o w t

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