examination of a case of squint

EXAMINATION OF A CASE OF

SQUINTNisha Kumari,

Optometrist, NSPB- IndiaDr. R.P. Centre, AIIMS

PRELIMINARY EXAMINATION

1. PRESENTING SIGNS & SYMPTOMS Patients usually come with following problems :-o Manifest squinto Defective ocular movementso Abnormal head postureo Defective visiono Intermittent squinto Nystagmus o Asthenopic symptoms Duration of occurrence of symptoms

should be noted (intermittent/constant).

2. HISTORY TAKING Obstetric history – Mother’s

health during pregnancy - delivery - Child’s weight at birth Medical history - General

development - Recent illness and treatment - Any trauma to the head &/or face - Any systemic disease Family history – squint, refractive

error Child – Greater emphasis on

obstetric history & developmental milestones.

Adult – Medical history can be of paramount importance

3. Previous treatment (if any) Optical (glasses/prisms/C.L.) Occlusion Orthoptic Operative Miotics Pleoptics Type & results of treatment.

3. Visual acuity assessment Tested for distance & for near Unaided & aided With pinhole Easier to do in adults & older

children Challenging in infants &

children with slower mental development

VISUAL ACUITY TESTS ACCORDING TO AGE

AGE OF CHILD

VA ASSESSMENT METHOD

Infant Catford drum test, TAC, OKNOVIS, Cardiff acuity cards (@ 25 cm)

1-2 years Boeck candy test, Worth’s ivory ball test, Sheridan’s ball test

2-3 years Miniature toy test, Coin test, Dt visual acuity test

3-5 years Tumbling ‘E’, Landolt’s ‘C’, Sheridan letter test, Lippman’s HOTV test

4.Fixation Ability of each eye to fixate at an object steadily & to

maintain that fixation is checked. Pattern of fixation is checked In children, fixation preference is checked. CSM method - central - steady - maintained -> child won’t allow to cover normal eye -> alternate fixation→ no amblyopia

5.Refractive status of the eye With proper cycloplegia

6. Anterior segment examination

7. Fundus examination

TWO ASPECTS

EXAMINATION OF THE MOTOR STATUS

• Head posture• Ocular deviation• Ocular movements• Fusional Vergences

EXAMINATION OF THE SENSORY STATUS

• Binocularity (+ or -)• Diplopia (+ or -)• Type of Correspondence• Suppression (+ or -) (if +, extent & depth)• Amblyopia (+ or -)• Stereopsis (+ or -) (if +, grade)

EXAMINATION OF MOTOR STATUS

HEAD POSTURE Observation at the first glance of

the patient Components –(i) Vertical (chin elevation or depression )(ii) Horizontal (face turn to R or L)(iii) Torsional (head tilt to R shoulder or L

shoulder) Head posture ensures that the eye is

out of the field of action of the paralytic muscle

OCULAR MOVEMENTS Methods to check – 3-step test Hess/lees charting FDT AFGT Ocular movements – Ductions , Versions & Vergences Tests the agonistic , antagonistic & synergistic action of

muscles. Restrictive squint – severe limitation of movements

compared to ocular deviation which is small Paralytic squint – limitation of movement of eye relates with

the ocular deviation Graded subjectively

DOCUMENTATION OF OCULAR MOVEMENTS

FUSIONAL VERGENCES Tested in 3 planes :- Horizontal vergences – Convergence & Divergence

(NPC & convergence sustenance measured) Vertical vergences – Sursumvergence &

Deorsumvergence Torsional vergence – Incyclovergence &

Excyclovergence Amplitudes of vergences measured with prisms

EXAMINING FOR OCULAR DEVIATION Has 2 components – Detection & quantification

DETECTION OF SQUINT1. Cover test2. Cover – uncover test

QUANTIFICATION OF SQUINT1. For distance & for near2. With & without glasses3. In 9 cardinal gaze positions4. 25⁰ up gaze & 35⁰ down gaze5. With right & left eye fixating

alternately6. Subjective & objective methods7. After prolonged cover

METHODS TO QUANTIFY SQUINT

1. Corneal reflection tests (Hirchsberg’s & Krimsky test)

2. Prism Bar Cover Test3. Synoptophore4. Maddox rod5. Maddox wing (near)

DETECTION OF SQUINT

COVER TEST Objective test Requires - Proper fixation

target to control accommodation

- Fixation distance – 6 m for distance and 33cm for near.

- Occluder (semi-transparent)

COVER – UNCOVER TEST Unmasks the latent squint B/E should be able to fixate the target, have

central fixation, have no gross motility defect

INFORMATION PROVIDED BY COVER & COVER-UNCOVER TEST

Direction of deviation The difference in angle from near to distance The effect of accommodation Comitance and incomitance The speed of recovery in latent strabismus.

Intermittent, constant(unilateral or

alternating) Latent nystagmus or latent component in

manifest nystagmus DVD A/V Pattern

QUANTIFICATION OF SQUINT

PRINCIPLES

Diplopia principle (single “physical location” perceived by the subject as 2 “perceptual localizations”) – Diplopia charting, Maddox rod test.

Haploscopic principle( 2 “physical locations” used to have 1 “perceptual localization”) – Synoptophore(when tested subjectively) , Hess/Lees screen.

CORNEAL REFLECTION TESTS

Hirchsberg’s test – Used as an initial screen for strabismus or in patients who are not able to fixate at any given target.

CORNEAL REFLECTION TESTS Krimsky test – Used to centralize

the corneal reflection in squinting eye with the help of prisms.

PRISM BAR COVER TEST Apex towards deviation Addition of neutralisation of

deviation with prisms to cover – uncover test.

Done for distance as well as for near

Done with & without refractive correction

Can be done in all 9 diagnostic gaze positions

SYNOPTOPHORE Based on haploscopic principle Measurement of deviation(objective and subjective) &

range of fusion(convergence and divergence) Assessment of binocular status (SMP, fusion & stereopsis)

MADDOX ROD TEST Measures latent, manifest, horizontal & vertical

deviation for distance & near. Used with maddox tangent scale.

MADDOX WING TEST Measures heterophoria for near. Can measure horizontal, vertical and cyclo

deviations.

MEASUREMENT OF CYCLODEVIATIONSUBJECTIVE METHODS

1. Diplopia charting (with a slit target)

2. Double maddox rod test

3. Synoptophore

OBJECTIVE METHODS

1. Indirect ophthalmoscopy

2. Fundus photography

DIAGNOSTIC OCCLUSION Diagnostic occlusion can be used to induce full

dissociation when it seems to the examiner that the maximum angle of deviation hasn’t been revealed.

Used in: Intermittent exotropia. To diagnose whether symptoms are due to

hetrophoria. To differentiate between real or apparent

limitation of abduction in children.

EXAMINATION OF SENSORY STATUS

Assessment of binocular status of eyes & the nature of correspondence b/w them.

1.Binocular diplopia (+) → Binocularity (+) : tested with the help of red-green goggles or Bagolini’s glasses or single/double maddox rod.

2.Retinal correspondence – NRC or ARC

3. Suppression – unilateral or alternating, facultative or obligatory, extent & depth.

4. Amblyopia – Fallout of obligatory suppression5. Stereopsis

METHODS TO EXAMINE THE SENSORY STATUS

1. Bagolini’s Striated Glasses Most physiological test for

dissociation of eyes Can detect ARC, suppression

2. Worth Four Dot Test Red-green dissociation More dissociating, less

physiological Can detect ARC, diplopia,

suppression

3. After-image Test Highly dissociating, not physiological,

don’t give the real picture always.

4. Testing extent of suppression – tested by prisms, synoptophore, lees/hess screen, polaroid scotometer

5. Graded density filter bar To test the depth of suppression

scotoma

To summarize..

Patient’s current complains are recorded. A proper history is taken. General health of the eye is checked. Detection of deviation. Measurement of deviation. Detection of fallouts of deviation.

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