INTRODUCTION:

DEFINITION:

Strabismus is the condition when visual axis of two eyes do not meet at the point of fixation.

COMITANT: Although misaligned they retain relation in all direction of gaze

INCOMITANT: Deviation is different in all position of gaze

TROPIA: It is manifest ocular misalignment .

PHORIA: It is latent ocular deviation.

ALTERNATE : Fixation is retained by alternate eye

UNILATERAL: Only one eye habitually fixes

INTERMITTENT: when deviation remain only for some time

Contd..

Tropia Or Phoria can be,

Esotropia /phoria

Exotropia/phoria

Hypertropia/phoria

Hypotropia/phoria

Cyclotropia/phoria

ASSESSMENT:History

Visual Acuity

Examination:

1) Examination of motor status : a) Head posture

b) Ocular deviation

c) Ocular motility

d) Diplopia

2) Examination of sensory status & adaptation

Refraction & fundoscopy

HISTORY

The age of onset

Gradual or sudden (old photographs may sometime help)

Symptoms, i.e. diplopia/ discomfort/ blurring/ eye ache/ cosmetic

Whether the symptoms occur during fatigue / illness/ stress/inattentive condition etc.

Whether it occurs for near/ distant vision

Whether it is unilateral/ alternate or constant/ intermittent.

General health ( measles, whooping cough), birth history( LBW) & family history( high refractive error, strabismus)

Previous treatment if any, & type & improvement after it.

VISUAL ACUITY

TESTING IN < 1YR AGE:

OKN test

Catford drum test

Preferential looking test

Teller acuity card test

Visually evoked potential

Indirectly by, blinking & fixation( central, steady , maintained)

TESTING IN 1-3 YRS AGE:

Cardiff acuity card test

Marble game test

STYCAR graded ballsvision test

Coin test, Miniature toytest, etc.

TESTING 3-5 YRS AGE:

Lea symbol chart

Broken wheel acuity

Sheridan- gardiner test

Tumbling E test

TESTING IN PRE-SCHOOL AGE:

Can be done by snellen’s chart/ above tests

EXAMINATION OF MOTOR STATUS:

ABNORMAL HEAD POSTURE (AHP) :

Chin elevation/ depression (vertical).

Face turn to right/ left side ( horizontal).

Head tilt to right or left shoulder (torsional).

CAUSES:

Incomitant squints

A –V phenomenon

One eyed persons

OCULAR DEVIATION:

Is it a true squint/ pseudo or apparent squint?

Causes of pseudo strabismus:

Telecanthus

Epicanthus

Hypertelorism

Ptosis

Lid retraction

Large angle κ

ANGLE KAPPA:

It is the angle subtended by the visual and optical axis and is usually about 5° (positive).

Contd…

A large positive angle κ stimulate exotropiaas in high hyperopia

A negative one stimulate esotropiaas in high myopia

TESTS TO MEASURE & DETECT OCULAR DEVIATION:

1) Cover test2) Cover- uncover test3) Alternate cover test4) Prism bar cover test5) Maddox rod test6) Double maddox rod test7) Maddox wing test8) Hirschberg’s test 9) Krimsky test 10) Bruckner test 11) 4D prism test

corneal reflection test

COVER TEST:

Fixation of eyes

Cover the apparently fixating eye

Observe the deviation of the other eye

Movement confirms manifest or true

squint(Heterotropia)

COVER-UNCOVER TEST:

One of the eyes is covered 2-3 sec

Then cover removed

In heterophoria the eye behind cover deviates

Examiner observes the movement of the on removal of cover

ALTERNATE COVER TEST:

The right eye covered for several seconds

Occluder quickly shifted to the opposite eye for 2sec

It repeats for several times

Examiner notes the recovery of eye position

Compensated heterophoria will have straight eyes, but poor control patient may show manifest deviation

PRISM BAR COVER TEST:

Prism of increasing strength is placed in front of squinting eye

Cover & alternate cover test is performed

Until the movement stops

MADDOX ROD TEST:

ORTHOPHORIA: streak passes through white light.

If streak passes on the left to the light i.e. esophoria &, if to the right then exophoria

DOUBLE MADDOX ROD TEST:

A red maddox rod is put in front of suspected eye & white in front of other eye.

Now a 6D prism is put behind white rod

The rods are kept at 90° in trial frame

Result:

Orthophoria: 2 line will be parallel

Cyclodeviation : Not parallel, red line will be inclined.

Angle can be measured by rotating the rod

MADDOX DOUBLE PRISM:

Patient will see 3 horizontal line parallel to each other.

In cyclodeviation Intermediate line will be oblique.

MADDOX WING TEST:

R/E : white arrow vertically And red arrow horizontally pointing left.

L/E :Horizontal row of figures in white and Vertical row in red

Contd…

White arrow measures horizontal tropia

Red arrow measures vertical tropia

In cyclophoria red scale is adjusted to appear parallel to horizontal scale.

HIRSCHBERG TEST:

Corneal reflections are usually symetricalin absence of squint

In esodeviationreflex fall on temporal cornea.

Roughly 1mm shift signifies 7° or 15 prism diopter.

KRIMSKY TEST:

A prism bar is placed in font of the fixating eye

The power increased

until the reflections get symmetrical.

BRUCKNER TEST:

Direct ophthalmoscope is used to obtain a red reflex simultaneously in both eyes.

In strabismus , the deviated eye will have a lighter and brighter reflex.

4 D PRISM TEST:

BIFOVEAL FIXATION:

Base-out prism placed in front R/E

For fixation B/E move to left

Then L/E move To right side to fuse image

IN LEFT MICROTROPIA:

When prism placed in front L/E no movement of either eye is seen

When moved to R/E , R/E adducts, Also the L/E Abducts

But L/E do not Adducts again to fuse image

OCULAR MOVEMENTS:

Ductions: Monocular movement

Versions: Binocular , simultaneous conjugate movement.

Vergences: Binocular, simultaneous, disjugate movement .

ACTION OF EXTRA-OCULAR MUSCLES:

9 POSITION OF GAZE:

Near point of convergence:

Nearest point on which eye can maintain binocular fixation.

Measured by RAF rule

It should be Less than 10 cm.

Near point of accommodation:

Nearest point on which eyes can maintain clear focus.

CONVERGENCE TEST:

Hold a pencil / a finger at distance of 30-40cm

Ask the patient to look at its tip

Bring it nearer to patient’s eyes.

kept at the eye level of patient till the eye develops

Diplopia or one eye Deviates

FUSIONAL AMPLITUDE:

It is the efficacy of vergence movements.

It is done by increasing prism dioptre.

Vertical fusional reserve: 1.5°-2.5°

Horizontal negative fusional reserve

(abduction range): 3°-5°

Horizontal positive fusional reserve

(adduction range) : 20°-40°

PRISM VERGENCE TEST:

Patient at 6m distance from light source

The highest Prism that permits single vision gives

Verging Power

TESTS FOR DIPLOPIA:

Diplopia charting

Hess screen test

Lees screen test

PARK’S 3 step test

Forced duction test

DIPLOPIA CHARTING:

Maximum separation is in the quadrant in which the muscle acts most

The level of 2 image

In which direction the image is deviated (image displaced toward the direction of action of the muscle)

LEFT LATERAL RECTUS PALSY:

HESS CHART:

Patient is asked to superimpose green light on the red light.

Procedure repeated with red filter in front of left eye.

The points are marked by examiner.

RESULT:

In orthophoria: both lights superimpose in 9 position of gaze.

Rt 6th nerve palsy:

R/E 4th nerve palsy:

LESS SCREEN:

Consists of two opalescent glass screens at right-angles to each other, bisected by a two-sided plane mirror which dissociates the two eyes

interpretation done as like hess chart

PARK’S 3 step test:

Use to identify cyclovertical muscle paralysis.

Performed by measuring the vertical alignment in

1)primary position,

2) In right and left gaze and

3) In head tilt to the right and to the left.

RIGHT HYPERTROPIA:

1) Circle the muscles which pull R/E down or L/E up

2) Determine whether vertical deviation is more on left/ right gaze

3) If worse when head tilted to right, tilt the circles to the right

FORCED DUCTION TEST:Anesthetize the eye

Lids retracted

Patient looks in the direction of

the muscle tested

Globe hold at the opposite limbuswith globe holding forceps

Eye is rotated at the direction of action of muscle

Contd..

RESULT:

If free movement is present then the test is negative

If restricted then the test is positive

EXAMINATION OF SENSORY STATUS:

Binocular vision & its grade

Type of Retinal correspondence

Suppression

It Determines prognosis in a case of squint.

GRADES OF BINOCULAR VISION:

1) First grade (simultaneous perception):

2) Second grade (Fusion):

3) Third grade (stereopsis)

SUPPRESSION:

It is active inhibition of image of one eye by the visual cortex, when both eyes are open.

Stimuli :

Diplopia

Confusion of image

Blurred image

RETINAL COREPONDENCE:

Each retina share the same subjective visual direction i.e.

In primary position: both fovea

In right sided object: Right nasal & left Temporal retina , & vice versa.

Abnormal retinal correspondence:

Abnormal retinalcorrespondence is acondition in which non-corresponding retinalelements acquire commonsubjective visual direction.

TESTS FOR SENSORY STATUS:

1) Bagolini’s striated glass test

2) Worth four dot test

3) After-image test

4) Synoptophore

BAGOLINI STRIATED GLASS TEST:

Symmetrical cross response

Asymmetrical cross response

Single line present

Cross response with gap in one line

WORTH FOUR DOT TEST:

All 4 lights seen –NRC/ Harmonious ARC

Left suppression – 2 red light

Right suppression – 3 green light

Diplopia – 3 green & 2 red light

Alternating suppression –Alternate green & red light.

AFTER-IMAGE TEST(HERING-BIELSCHOWSKY ):

A bright linear light is used

Patient views the target with one eye and the light is flashed

For R/E flash held vertically & for L/E horizontally

Patient appreciate a plus sign.

Contd…

a) is consistent with normal retinal correspondence (NRC), (b) shows uncrossed after-image(diplopia) and anomalous retinal correspondence (ARC) and (c) shows left supression

SYNOPTOPHORE:

It is an instrument ,used for potential for binocular function in presence of manifest squint, & tests SP, FUSION, STEREOPSIS

TESTS FOR STEREOPSIS:

1) TNO TEST

2) FRISBY TEST

3) LANG TEST

4) TITMUS TEST

TNO RANDOM DOT TEST:

Consists of seven plates of randomly distributed paired red-green dots.

Test targets are only visible to individuals who have stereopsis .

FRISBY TEST:

Consists of 3 transparent plates of, each printed with 4 squares.

1 of the squares contains a hidden circle, & the random shapes are printed on the reverse side.

Patient needs to find out the hidden circle.

LANG TEST:

Here glass is not used.

Patient has to identify simple shape (star ) on the card

TITMUS TEST:

Viewed through polaroid spectacle

Right plate contains a picture of fly

Left contains 9 squares, each containing 4 circles, of which 1 has disparity

test done at 40cm distance

Contd…

FLY: Appears to stand out from page

CIRCLES: 1 circle form disparity & appear forward.

THE ANIMALS : 3 rows of animal ,one of which appear forward.

Fundoscopy & refraction:

Dilated fundoscopy is mandatory.

To exclude any underlying ocular pathology such as macular scarring, optic disc hypoplasia or retinoblastoma.

Proper Refractive correction should be given by retinoscopy

CONCLUSION

It is a common childhood & adult problem.

It is extremely difficult to examine a child and a tactful examination is to be done.

Quantification of the angle of deviation, binocular vision, ocular movement, refraction is important for diagnosis & proper treatment purpose.