By AMEERHAMZA S B6th term MBBS

Shimoga Institute of Medical SciencesShimoga

AMBLYOPIA

How we see?

We learn to see, like walking or talking Learning to see is a slow process At birth – vision is noisy, can not distinguish

targets Object tracking starts around 3 month old Hand-eye-body coordination starts after 3 month

old Depth perception appears after 5 month old Vision is well developed by two years old

Definition:

It refers to a partial reversible loss of vision in one or both eyes, for which no cause can be found by physical examination of eye(absence of any organic disease).

Pathogenesis

Amblyopia is an eye condition when the nerves that connect one of the eyes to the brain do not develop correctly during childhood. As a result, the person sends blurry or wrong images to their brain, which results in the brain ignoring the information and favoring the other eye. Patients are seen using one eye more or may have problems with depth perception. 

TYPES

Strabismic Stimuslus deprivation

Anisometropic

Isoametropic

Strabismic amblyopia

Two eye moves in two direction

Brain cannot combine image from two eye into one

Double vision Brain starts to ignore

image from one eye Causes unilateral

amblyopia

Stimulus deprivation amblyopia

Congenital or traumatic cataract or corneal haziness

Occlude lights to reach the retina

No or distorted image formed on retina

No visual learning happens Both unilateral or bilateral

amblyopia can occur

Anisometropic amblyopia

Different focusing power in two eye

One eye gives clearer image than other

Brain starts to ignore the blurrier image

Causes unilateral amblyopia

Isoametroipc amblyoipa Is bilateral amblyopia occuring in

children with bilateral uncorrected high refractive error

Occurs in children eith uncorrected astigmatic refractive error

Meridional amblyoipa

Clinical features Visual acuity is decreasedCrowding phenomenon : visual

acuity is less when tested with multiple letter charts (eg.snellen’s chart)than single letter charts (eg.optotype).

Treatment

Younger the child , better is the prognosis.

Works best when child is under 3yrs of age.

1) Occlusion therapy : occlusion normal eye to force use of amblyopic eye

Before that procedure it should be ensured that

If any cataract…. is corrected. If any refractive error…is corrected. Upto 2 yrs it should be done in 2:1 i.e. 2

days occlusion in normal eye and one day in amblyopic eye.

At the age of 3… 3:1 At the age of 4….4:1

At the age of 5….5:1…..until the visual acuity develops fully

2) Penalization

i.e. blurring of vision of normal eye either by using

Atropine (Atropine penalization) orOver plus lenses in spectacles

(optical penalization)

3) Computerized vision therapy

It works on the form of operant conditioning(a form of psychological treatment)

Computerized Home Vision Therapy (CHTV) can prescribed as an alternative to occlusion therapy.

Other treatments• To re-establish foveal

fixation in young children

Pleoptic exercises

• Using levodopa/carbidopa as adjunct yo occlusion therapy

Pharmacologic manipulation

• Also suggested as an adjunct to occlusion therapy

Perceptual learning

Refernces

Comprehensive Opthalmology by A.K.Khurana ,6th Edition.