Notes compiled for Pediatrics

Ophthalmology (Med I, Block 5, OP)

Amblyopia and Strabismus University of Manitoba

Faculty of Medicine

MedII/OP7 Dr. P.

Shuckett 2008-09

Objectives:

1. To state how to measure or estimate visual acuity in children 2. To detect strabismus by general inspection, the corneal light reflex test, and the cover test. 3. To explain why it is necessary to perform ophthalmoscopy in a child to rule out any organic causes

of impaired vision when amblyopia is suspected. 4. To explain to parents the need for prompt treatment of amblyopia.

This lecture is loosely based on the material found in Chapter 6,Basic Ophthalmology by Frank Berson Objectives include understanding the concepts of amblyopia and strabismus how they can be diagnosed, and a review of visual development and the measurement of vision in a child.

ADULT (over 8) vs. CHILD

ability to SUPPRESS

DIPLOPLIA IN ADULTS

The major difference between an adult and a child is the ability to suppress the information from one

eye. The child suppresses the information from the non fixing eye. An adult can't and instead sees both images ie) double.

EXTRAOCULAR MUSCLES -action, innervation

MEDIAL RECTUS -adduction (3) LATERAL RECTUS -abduction (6) SUPERIOR RECTUS -elevation (3) INFERIOR RECTUS -depression (3) INFERIOR OBLIQUE-excyclorotation (3) SUPERIOR OBLIQUE incyclorotation (4)

NOMENCLATURE

FUSION- the brain's mechanism to keep the eyes working together preventing double

vision and keeping them straight. TROPIA- a manifest turn, the fusion mechanism has broken down. PHORIA- a tendency for the eyes to turn. Fusion mechanism prevents this from occurring' If

fusion is eliminated a turn develops

ESO- eyes turned in

EXO- eyes turned out

HYPER- one eye higher than the other

COMMITENT- the type of turn caused by fusional breakdown .Not caused by a specific muscle

weakness and therefore symmetrical. The type most commonly seen in children

NONCOMMITENT- the type of turn caused by muscle palsx. Not symmetrical. Uncommon in

children ,

STRABISMUS- turned eye i.e. one eye fixes on the object of regard; the other doesn't

Amblyopia and Strabismus University of Manitoba

Faculty of Medicine Med II/OP 7 Dr. P. Shuckett 2008 - 09

DIAGNOSING STRABISMUS

CORNEAL LIGHT REFLEX - does the light reflect in a symmetrical manner COVER TEST-diagnosing TROPIA

Cover one eye observe the movement of the otherveye

repeat covering the other eye

movement=tropia

UNCOVER TEST-diagnosing PHORIA cover test negative

observe eye as you uncover it repeat for other eye

movement=phoria

ALTERNATE COVER TEST-diagnosing TROPIA or PHORIA cover one eye quickly cover the other movement=tropia or phoria

VISUAL DEVELOPMENT-THEORETICAL

BIRTH- 20/200- normal infants can see their mother 4 MONTHS- MACULA MATURE - baby can fix and follow with each eye. -if not refer 6 MONTHS- Evoked potential -fully developed

2 YEARS- 20/20 -using preferential looking.

TESTING FOR ACUITY AND AMBLYOPIA

FIXATION-after 4 months fix and follow (one eye at a time) FIXATION PREFERENCE up to 3 cover one eye and observe behavior PICTURE CARDS 3-4 differences more important -

EGAME 4-5 2 line difference or 20/40 -refer SNELLEN LETTERS 5+ 2 line difference or 20/40-refer

Amblyopia and

Strabismus

University of

Manitoba Faculty of

Medicine Med II/OP 7

Dr. P. Shuckett 2008

- 09

AMBLYOPIA-POTENTIALLY NORMAL VISION IN AN EYE WITH SUBNORMAL VISION.

caused by visual deprivation or distortion

reversed by "correcting cause " and forcing use of the amblyopic eye

TOTAL DEPRIVATION OF ONE EYE FROM BIRTH-TWO MONTHS -IRREVERSIBLE

1 YEAR-1 MONTH TO REVERSE

6 YEARS -6 TO 12 MONTHS TO REVERSE

9 YEARS -NO REVERSAL

*** RED REFLEX *** diagnose visual obstruction at birth

TYPES OF STRABISMUS

ESOTROPIA I

NFANTILE (diagnosed by 6 months) Tx.-SURGERY

ACCOMMODATIVE-accommodates because of hyperopia!eyes converge and fusion mechanism

breaks down Tx.-SPECTACLES INCLUDING BIFOCALS THEN SURGERY (AMBLYOPIA COMMON)

EXOTROPIA

INTERMITTENT ~ AMBLYOPIA RARE

Usually CONSERVATIVE MANAGEMENT

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STRABISMUS and

AMBLYOPIAPaul Shuckett

• Early diagnosis and treatment prevents visual loss

• Strabismus = misalignment of the eyes

• Amblyopia = visual impairment in one eye from lack of use

A childs eyeis not

an adult eye

Suppression

Non-comitant

Children do not outgrow crossed

eyes

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Eye Exercises

do not correctlearning disabilities

• Childs eye ≠ adult eye]

• Pseudostrabismus ≠ true strabismus

• Eye exercises do not work

Strabismussuppressionamblyopia

loss of vision

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Diagnostic tests for strabismus

• Corneal Light Reflex Test

• Cover Tests

• Bruckner Test

• Cover test - tropia

• Uncover test -phoria

• Alternate cover test- tropia and phoria

• Tropia -one eye fixes on the object of regard. The other eye does not.

• Phoria -suppressed tendency for one eye to drift off the object of regard.

• Fusion keeps the eyes working together. When fusion is prevented (covering one eye) the covered eye

drifts off the object of regard

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Bruckner Reflex

• Direct ophthalmoscope 1 meter from patient

• Focus on cornea and compare red reflex

• Fail if difference in color or brightness

– Asymmetry represents strabismus or significant refractive diffference in the eyes

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Diagnostic Tests for Amblyopia

• Measure Visual acuity

Visual development

• Birth-visual acuity at least 20/200

• Four Months- macula anatomically developed

• Eight years- entire eye and cortical systems fully mature

• 4-6 months follow toy

• 2-3 years flash cards

• 3-4 years illiterate E

• 4-5 years Snellen letters

Infants

• Cover one eye at a time. Refer if

– Object when one eye is covered

– Following ability is unequal

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Flashcards

• Teach objects binocularly

• Check vision one eye at a time

• Refer if:• Discrepancy between the eyes

• Visual acuity <20/50 in either eye

Illiterate E

• Teach child to use a hand held E

• Monocular testing

• Point to E’s on chart

• Refer if• Difference between eyes

• Vision 20/40 in either eye

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Snellen Chart

• Teach child binocularly. If problems revert to E

• Monocular testing as in Illiterate E

• Refer if• Difference of 2 lines

• Vision < 20/30 in a six year old

Causes and Treatment ofAmblyopia

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Major causes of Amblyopia

• Strabismus-squint

• Anisometropia-difference in refractive error between the 2 eyes

• Vision deprivation of one eye

Amblyopia Facts

• Total deprivation of one eye from birth to 3 months

• Best vision 20/200

• Amblyopia discovered at age 1• Reversed in 1 month

• Amblyopia discoveed at age 3• Reversed in 3 months

• Amblyopia discovered age 6• Reversed in 6+ months

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Referral for suspected amblyopia

• Decreased vision (one or both eyes)

• Strabismus

• Family history of strabismus or amblyopia

• Cataract , Glaucoma , other blocking mechanisms

USE OPHTHALMOSCOPETO EXAMINE

• Red reflex

• fundus

Forms and Treatment of Strabismus

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• Children-usually comitant.

No muscle weakness

• Adults - usually non comitantAcquired specific muscle(s) weakness

Accomodative Esotropia

• Accomodative convergence reflex

• Glasses to control turn

• Often associated with amblyopia

• Surgery if glasses insuccessfull.

Infantile Esotropia

• Develops after 3 months

• Refer when identified

• Early surgery (starting at age 6 months)

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Exotropia

• Most often intermittent

– Fatigued

– Distant viewing

• Conservative management

– Surgery with frequency and/or large size

Unusual forms of Strabismus

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Adult onset Strabismusnon commitment

• Non Comitant (specific muscle(s)

• Identify paretic muscle(s)

• Investigate etiology

When Misalignment occurs

REFER

Inform Parents

• Surgery safe and effective

• Eyeball not removed

• May need more than one operation

• Both eyes often require surgery

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Types of Surgery

• Recession- relax muscle

• Resection- strengthen muscle

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