Amblyopia

Lazy eye, the brain ignoring a weak eye

Overview

Amblyopia, often called lazy eye, is reduced vision in one or occasionally both eyes that results from abnormal visual experience during early childhood rather than from a structural problem in the eye itself. When one eye sends a blurred or misaligned image to the developing brain, the visual cortex comes to favor the other eye and suppresses input from the weaker one. The main causes are strabismus, a misalignment of the eyes, anisometropia, a substantial difference in refractive error between the eyes, and deprivation, where something such as a congenital cataract or a droopy eyelid blocks vision. It is one of the most common causes of reduced vision in children. Its biological basis was illuminated by the visual deprivation experiments of David Hubel and Torsten Wiesel, part of the work for which they shared the 1981 Nobel Prize. Treatment first addresses the underlying cause and then encourages use of the weaker eye through patching or atropine penalization of the stronger eye, and responses are generally better the younger the child, reflecting the critical period of visual development.