amblyopia

Amblyopia, commonly called lazy eye, is a neurodevelopmental visual disorder characterized by reduced visual acuity in one or both eyes that cannot be corrected solely by glasses and is not due to an obvious structural problem in the eye. It arises from abnormal visual development during early life and the brain’s suppression of input from the affected eye.

The most frequent causes are strabismus (misalignment of the eyes), anisometropia (unequal refractive errors between the eyes), and deprivation during the early visual period (for example, cataract or severe ptosis that blocks vision). Amblyopia usually develops in childhood and is most receptive to treatment when detected early, ideally before the child reaches school age.

Pathophysiology involves suppression of the image from the affected eye by the brain to avoid double vision, leading to poor development of the neural pathways for that eye. Even with correction of refractive error, the brain may continue to ignore input from the weaker eye unless active therapy is provided.

Diagnosis is based on reduced best-corrected visual acuity that cannot be explained by ocular disease, along with tests for eye alignment, refractive error, and binocular function. Screening in young children is important for early detection. A comprehensive assessment may include vision testing, cover tests, refraction, and evaluation of the visual axis.

Treatment aims to restore and maintain use of the weaker eye. Primary strategies include correcting refractive errors with glasses or contact lenses, occlusion therapy (patching the good eye) for several hours daily, and pharmacologic penalization with atropine drops. Vision therapy or binocular training may be used, and in some cases surgical alignment of the eyes is considered to improve binocularity, though surgery alone does not cure amblyopia.

Prognosis is best when treatment starts early, with ongoing outcomes influenced by age at onset, cause, and adherence. Amblyopia affects about 2-4% of people, typically unilateral.