Amblyopia Causing Squint and Squint Causing Amblyopia
-Its Recognition and Optimal Management

Kanwar Mohan
(Grewal Eye Institute, SCO 168-169, Sector 9-C, Chandigarh)

Whenever a patient with both amblyopia and squint presents, the ophthalmologist is faced with the question whether amblyopia caused squint or squint caused amblyopia.

Amblyopia causes a severe obstacle to sensory fusion which leads to strabismus. Here strabismus is the direct consequence of a primary sensory deficit. Some patients get exotropia and some get esotropia. Possibly a variable tonic convergence during early childhood and perhaps less forceful tonic convergence during adulthood contribute to the direction of sensory heterotropia. There is no correlation between the degree of visual impairment and development of esotropia or exotropia.

Squint causes suppression of images in the deviating eye which subsequently leads to amblyopia. Squints accounts for 30-45% of the patients of amblyopia. If we consider relative risk, strabismus patients are nearly 15 times more prone to become amblyopic than non-strabismus individual. Esotropia accounts for nearly 61% and exotropia accounts for only 6% of the cases of amblyopia. It has been shown that the appreance of amblyopia is more closely related with duration of strabismus than with age of the child at the time the squint appeared.

In a patient with amblyopia and squint, if there is a history or record or photograph showing straight eyes previously and squint developed subsequently, most likely squint developed due to amblyopia. If there is record of normal vision initially and subsequently squint and poor vision are noted and there is no other amblyogenic factor such as anisometropia or stimulus deprivation, most likely amblyopia developed due to squint. However, in absence of initial record, it may not be possible to know whether amblyopia caused squint or squint caused amblyopia.

Irrespective of whether amblyopia caused squint or squint caused amblyopia, amblyopia should always be treated first because a good vision presents a fusion lock which prevents recurrence of squint. Also if squint surgery is performed without treating amblyopia, the surgeon and the parents feel happy and relaxed with straight eyes of the child, and the treatment of the amblyopia is ignored. This leads to permanent visual loss.

If amblyopia is cured, one can perform conventional surgery for correction of associated squint. However if amblyopia is untreatable or only partially cured, exotropia should be overcorrected and esotropia should be undercorrected.

Home|Introduction|Office Bearers|Activities|Members|Oration