AMBLYOPIA

PREPARED BY:

Anis Suzanna binti Mohamad

Optometrist

INTRODUCTION

What is amblyopia? What are the types of amblyopia?What causes of amblyopia? Classification of amblyopia?What are the sign and symptoms of

amblyopia?

What is amblyopia?

• “Lazy eye”

• A unilateral/bilateral condition

• The best corrected VA is poorer than 6/9 in absence of the ocular media and fundus anomalies or ocular disease.

• Prevalence:- occurs about 1 in 25 children develop some degree of amblyopia.

• High risk of becoming blind.

Normal vision Amblyopia ( Loss of vision)

Reduction clarity of vision in amblyopic eye

How does it happen?

How does it happen?

What causes of amblyopia? • There are four major causes of amblyopia which are:

Unequal/Poor visual acuity Unequal refractive error (Anisometropia)

Bilateral equal high refractive errors (isoametropia)

Uncorrected moderate/high astigmatism

Strabismus/Misaligned Eyes

Blockage or deprivation

Toxic

Unequal/Poor visual acuity due to: 1) Unequal refractive error (Anisometropia)

Unequal/Poor visual acuity due to:

Uncorrected high myopia Uncorrected high hyperopia

2) Bilateral equal high refractive errors (isoametropia)

More than -6.00D to -9.00D More than +4.00D

Blurred image form onto the retina because ray of light focused in front of the retina.

Blurred image form onto the retina because ray of light focused at the back of retina.

Unequal/Poor visual acuity due to:

3) Uncorrected moderate/high astigmatism

Meridional amblyopia is a mild condition in which lines are seen less clearly at some orientations than others after full refractive correction.

Unequal/Poor visual acuity due to:

3) Uncorrected moderate/high astigmatismA Compound myopic

B Simple myopic

C Mixed astigmatism

D Simple hyperopic

E Compound hyperopic

Clinical types of astigmatism which can lead to meridonal astigmatism if it is not corrected within plastic age.

Constant strabismus or an imbalance in the positioning of the two eyes

Strabismic amblyopia

Blockage or deprivation

an opacity in the line of vision-e.g: cataract

Due to: -Congenital/traumatic cataract -Congenital ptosis

-Congenital/traumatic corneal opacities.

Toxic • Drugs - chloramphenicol, digoxin, ethambutol

• Tobacco- piped smoker, excessive smoker

• Alcohol- alcoholic • Chemicals-

 Lead, methanol• Nutritional

disorders - such as Strachan's syndrome, lack of vitamin A and zinc.

The optic nerve head in acquired optic neuropathies

What are the types of amblyopia?

• The nature of amblyopia differs depending on the cause:-

Refractive amblyopia Anisometropic amblyopia Meridonial amblyopia Strabismic amblyopia Visual deprivation amblyopia Toxic amblyopia

Classification of amblyopia

Functional Amblyopia• Not due to the

diseases in the eye• unilateral/bilateral of

the eye• Reversible• Examples:

– Refractive amblyopia– Anisometropic

amblyopia– Meridonial amblyopia– Strabismic amblyopia

Structural/Pathological Amblyopia

• Due to lesion in the eye or visual pathway

• unilateral/bilateral of the eye

• Irreversible• Examples:

– Visual deprivation amblyopia

– Toxic amblyopia

Type Causes

Refractive amblyopia • Uncorrected isometropia • Result :- A blurred image in both eyes.

Anisometropic amblyopia(Second in frequency)

• Uncorrected anisometropia• Result :- A blurred image in more ametropic eye.

Meridonial amblyopia • uncorrected high astigmatism• Result :- A blurred and distorted image in unilateral or bilateral eyes.

Strabismic amblyopia(most common)

• Constant strabismus• Suppression in deviated eye

Functional Amblyopia

Structural/Pathological Amblyopia

Types Causes

Visual deprivation amblyopia • Opacities in ocular media or structures• Examples:- cataracts, cornea opacities and cloudy vitreous in infants.

Toxic amblyopia • Drugs, tobacco, alcohol, chemicals, nutritional disorders.

What are the sign and symptoms of amblyopia?

Symptoms • No symptoms • Blurred vision• Reduced vision• Reduced contrast

sensitivity

Signs • No obvious sign, unless

severe abnormality is present.

• Rubbing or squinting of eyes

• Misaligning eyes• Reduced VA • Droopy eyelid

ASSESMENT

Assessment of deviation– Compare magnitude at distance versus

near• Laterality• Concomitancy• frequency

– The test is• Cover test• Hirchberg test

– Uses pen torch– Corneal reflexes

• Bruchner test– Uses ophthalmoscope– Observe the color and brightness of fundus

reflexes and compared

Hirschberg test Bruckner test

Strategies in assessment of amblyopia

1. Visual Acuity (VA)

• Degree of amblyopia• Crowding phenomena

– Normal Snellen Chart• Line Acuity

– Single Letter Chart• Single Letter Acuity

2. Neutral Density (ND) Filter

• Depth of amblyopia• Differentiate between

organic amblyopia or functional amblyopia

1. Visual Acuity (VA)– Amblyopes perform better when isolated

letters are used instead of full chart.– Crowding effect

• Single letter acuity– Infant

• Teller acuity chart– Preschool-aged children

• Lea symbols, HOTV or broken wheel cards– School-aged children

• Snellen chart or Log MAR chart

Visual Acuity Chart

Snellen Chart Single letter chart

Single Letter AcuityAdvantage

• Directly measures acuity especially in children 3-6 years old.

Disadvantage • Isolated letters can be

used, which may lead to under estimated amblyopia visual loss.

Solutions: Crowding bar may help alleviate this problem

Crowding effect

• Crowding bar, or contour interaction bars, allow the examiner to test the crowding phenomenon with isolated optotype.

• Bar surrounding the optotype mimic the full of optotype to the amblyopia child.

E O

Teller acuity chart

Lea symbol

HOTV

• In strabismic eye, mostly it use other part of area instead of fovea area which consist rod.

• Image that form will reduce in contrast.

• Hence, it also reduce the visual acuity of the eye.

2. Neutral Density (ND) Filter• Strabismic amblyopia

– Better VA with ND filter compared to the normal eye

– The use of a neutral-density (ND) filter in front of the fixing eye enhanced motion-in-depth performance.

– exhibit residual performance for motion in depth, and it is disparity based

• Anisometropic amblyopia

– Cannot be diagnosed with neutral density filter

ND bar

Neutral Density (ND) Filter

Strabismic amblyopia Anisometropic amblyopia

VA increased with ND filter VA cannot be diagnosed with ND filter

Contrast sensitivity test

– Detect functional differences between strabismic and anisometropic amblyopes

– Strabismic amblyopes showed abnormalities only in the high spatial frequency range

– Anisometropic amblyopes showed an abnormal function both in the low and high spatial frequency range

Contrast sensitivity test

Pelli-Robson contrast sensitivity chart

Functional Acuity Contrast Test (FACT)

The contrast sensitivity function

• A- normal contrast sensitivity function

• B- mid to low contrast sensitivity losses

• C- more severe refractive errors or severe amblyopia

• D- Mild refractive error or mild amblyopiaExamples of how the CSF is

altered due to refractive error or disease.

* The pivotal visual developmental study of Harwerth et al.

Eccentric fixation– Fixate away from fovea

• In strabismic amblyopic eye– Visuscopy

• Detect and assess eccentric fixation• Explain decreased vision and lead to a more

accurate measurement of strabismus• Grid center is temporal to foveal reflex(temporal EF)• Grid center is nasal to foveal reflex(nasal EF)• Grid center is superior to foveal reflex(superior EF)• Grid center is inferior to foveal reflex(inferior EF)

Eccentric Fixation

Binocularity/stereoacuity test– Ambyopia reduced VA, it also has reduced stereopsis– Stereo smile for infant– Preschool random-dot stereogram or random-dot test

for preschool children

TNO test

Stereo smile Random-dot stereogram

Refraction– commonly can determine anisometropia– Cycloplegic refraction

• Spasm the ciliary muscle to inactive the accommodation by using drug

– Uses 1% cyclopentolate hydrochoride– Usually more hyperopic or more

astigmatic eye for the amblyopic eye

External and internal ocular examination of the eye

– Determine either it is visual deprivation amblyopia or afferent pupillary defect are characteristic of optic nerve disease but occasionally appear to be present with amblyopia

– To rule out ocular pathology– These examination consist of

assessment • Physiological function• Anatomical status

MANAGEMENTGoal of treatmentPassive therapy

•Optical correction•Occlusion•Penalization

Active therapy•CAM visual stimulator•Intermittent photic stimulation (IPS)•Pleoptics

GOAL OF TREATMENT: to restore and improves visual acuity by two

strategies:

1. present CLEAR retinal image to the amblyopic eye

• eliminate causes of visual deprivation• correcting visually important refractive errors

2. make the child use the amblyopic eye

• Recommended treatment should be based on– patient’s age, visual acuity, compliance with

previous treatment & physical, social and psychological status

CHOICES OF TREATMENTthe choices of treatment of amblyopia are used alone or in combination to achieve goal of treatment

1. Passive therapy: The patient experiences a change in visual stimulation without any conscious effort

i. Proper refractive correction ii. Occlusioniii. Penalization

Passive therapy:i. Proper refractive correction

• PURPOSE:– to provide sharp images and

providing OPTIMAL environment for amblyopia therapy

• Give pt proper optical correction alone– Short period of time (6-8 weeks)

before initiation of other therapy

Passive therapy:

ii. Occlusion • PURPOSE:

cover good eye to stimulate amblyopic eye

• Enable the amblyopic eye to enhance neural input to the visual cortex

• Decreasing inhibition better eye

• occlusion can be classified in several ways:

– Ways of patching• adhesive patch• spectacles occlude• opaque contact lens

– Type • direct occlusion: to stimulate amblyopic eye• inverse occlusion: to weaken eccentric fixation

– Duration • full time occlusion : for deprivational amblyopia• part time occlusion : to help preserve fusion

• Ways of patching– There are several ways of patching

– Excluding light and form:• Adhesive patching• Spectacle occlude• Opaque contact lens

– Excluding form (ie: frosted glass)

- Partial patching form• allow appreciation of form but

diminish acuity– ie. Translucent materials (Bangerter

foil)– foil is cut to size and positioned on

inner lens surface

• or occlusion covering part of spectacles– ie. Lower half of spectacles – to promote use of the amblyopic eye

for near work

• Type• Direct occlusion

• Patch the good eye• stimulate amblyopic eye• Indication for

• deprivation amblyopia• anisometropic amblyopia

• Inverse occlusion• For amblyopia associated with EF -->

strabismic amblyopia • Patching the amblyopic eye

• To weaken eccentric fixation of amblyopic eye

• If children under 5 year old age• direct full time occlusion may risk reverse

amblyopia • Do direct occlusion alternate with inverse

occlusion• Ie: for 3 years old children, may need 3 days direct

and 1 day indirect occlusion consider 1 cycle and repeated period of time

• Duration– Based on binocular vision status, age,

performance need

• Full time occlusion• 24 hours a day/waking hours• For children over 7 years over plastic age• When there is no binocular vision

• strabismic amblyopia– Alternate strabismus– Constant strabismus

• Also anisometropic amblyopia with poor binocular vision

• Shows more rapid development

• Part time occlusion• For specific periods / prescribed activities

• When binocularity is present • anisometropic amblyopia

• To help preserve fusion• Prevent occluded eye become amblyopic if doing

full time occlusion

• Children under 4 years• 2 hours per day• Prevent deprivation amblyopia in good eye

• Occlusion is maintained until there has been no further improvement for the last 5-6 weeks

• Frequent check are necessary to monitor ocular health, binocular status and each eye’s acuity

1. Drug penalization

• 1 gtt of 1% atropine instilled daily• to good eye

• Provide sufficient blur to force the child

• use amblyopic eye at near • good eye at distance

1.Has cosmetic advantages and does not totally disrupt binocular vision

• Effective method of treatment • for mild to moderate amblyopia in

children

Active therapy:

Penalization

2. Optical penalization• Children who do not

tolerate patching

• Fog the good eye (non-amblyopic eye) +3.00 D

• Amblyopic eye use for distance and good eye use for near

• Not practically applicable– Do near work most of time

compared to distance

2. Active therapy: • is designed to improve visual performance by the patient ‘s

conscious involvement in a sequence of a specific, controlled visual task that provide feedback

i. CAM visual stimulator

ii. Intermittent photic stimulation

iii. Pleoptic

Active therapy:i. CAM visual stimulator

• Treat amblyopia – by intense visual stimulation

for short period of time

• Grating of different spatial frequency are rotated in front of amblyopic eye

• The good eye is occluded

• Method based on: – cortical cell response to specific

line orientation and to certain spatial frequency.

– Therefore rotation ensured that a large range of cortical neurons are stimulated

• Better for anisometropic

amblyopia

Active therapy:ii. Intermittent photic

stimulation• Mallet IPS unit

• described as the "heightened response" to a visual stimulus

• The targets – consisted of slides containing

much detail of varying type and angular dimension

– viewed against a red flickering background.

• Red slight stimulation at 4Hz • detailed visual task for 20-30

minutes

1. 2.

3. 4.

Active therapy:iii. Pleoptics

• Purposes :– To disrupt eccentric fixation in

strabismic amblyopia

• Apparatus based on ophthalmoscope principle

• Euthyscope, projectoscope, pleutophore

• Exposed peripheral retina to a very bright light while protecting the macular area

• Only suitable for children >7 years old

Euthyscope

Surgery If amblyopia is due to:

• cataract cataract surgery

• nonclearing vitreous opacities vitrectomy

• corneal opacities corneal graft

• Blepharoptosis tarsal tuck

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