Page 22 - NAME OF CONDITION: REFRACTIVE ERRORS

NAME OF CONDITION: STRABISMUS AND AMBLYOPIA

I. WHEN TO SUSPECT/ RECOGNIZE?

a) Introduction:

Strabismus or amblyopia or both together may lead to failure to develop binocular vision
which may prevent individual pursuing specific occupations. The associated cosmetic
disorder may interfere with social and psychological development with potentially serious
effects on individuals. Timely diagnosis and appropriate treatment of children with
strabismus and/or amblyopia is likely to reduce the prevalence of persistent amblyopia and

ocular misalignment in adults.

Rarely, strabismus and/or amblyopia may be the presenting symptom in children with a
serious eye disease or systemic condition (e.g. retinoblastoma or hydrocephalus) when
urgent referral to a specialist may be necessary. Amblyopia is the most common visual
disability in children. It can present as early as 3 months of age. Its progression and
reversibility both are inversely proportional to child’s age. It is commonly unilateral. Nearly
all amblyopic visual loss is preventable or reversible with timely detection and appropriate
intervention.

b) Case definition:

Strabismus is a misalignment of the eyes in which the visual axes deviate from bifoveal
fixation.

Amblyopia is a unilateral or, less commonly, bilateral reduction of best-corrected visual
acuity that cannot only and directly be attributed to the effect of a structural abnormality
of the eye or the visual pathways.

For practical purposes, amblyopia is defined as at least 2 Snellen lines difference in visual
acuity between the eyes, but amblyopia is truly a spectrum of visual loss, ranging from
missing a few letters on the 6/6 (20/20) line to hand motion vision. It is a diagnosis of
exclusion. Amblyopia is caused by abnormal visual experience early in life resulting from
one of the following:

 Strabismus

 Anisometropia or high bilateral refractive errors (isometropia)

 Visual deprivation
With timely intervention, the reduction in visual acuity caused by amblyopia can be
completely or partially reversed.

22