Most cases of amblyopia are unilateral and relatively mild. Unilateral cases usually occur due to anisometropia or strabismus or a combination of the two, and in the minority of cases due to visual deprivation. When diagnosed early the treatment is usually relatively easy and effective and includes corrective glasses, patching or penalization, and/or vision training. In some rare instances, however, amblyopia can also present bilaterally which requires a somewhat different approach to the treatment.
Bilateral amblyopia is caused by bilateral optic abnormalities
Bilateral cases of amblyopia occur due to bilateral abnormalities of the anterior segment of the eye that result in blurry images that fall on retinas of both eyes. Examples include any form of bilateral optic opacities that lead to bilateral visual deprivation, such as congenital cataract, corneal opacities, or hemorrhages in the vitreous. Those are often congenital but can also be acquired later in childhood. Another possible etiology of bilateral amblyopia is severe bilateral refractive abnormalities, which comprise of bilateral high astigmatism (cylinder) or high hypermetropia (plus diopter).
Different treatment approaches for the same goal
Whilst the treatment goal for bilateral cases of amblyopia is exactly the same as for unilateral ones – to restore visual acuity and binocular visual function – the way how to get there, due to obvious reasons, slightly differs. Patching for instance, which is very effective in unilateral cases, is of no benefit in bilateral ones, as both eyes are equally deprived and covering one does not do anything. Hence, it is even more important to address the cause that led to amblyopia, let it be the extraction of bilateral cataracts, or simply prescribing correct refractive glasses that will eliminate severe astigmatism of hypermetropia.
Needless to say, though, when the cause for bilateral amblyopia has been properly addressed, vision training can also help and accelerate the recovery of visual acuity.