Poor vision. Amblyopia occurs when one or both eyes are not given the opportunity to see well in infancy and youth. It can be caused by uncorrected need for glasses, an eye that is not straight (strabismus), or something blocking the vision (congenital cataract, drooping eyelid). If not caught and treated early (by age 4-6), the eye will have limited potential vision (usually 20/40 or worse).
An Eye Disorder. Amblyopia is a condition when one eye is myopic (nearsighted) and the other eye is not. This can lead to confusion in the brain as each eye delivers two different pictures. Instead of seeing double vision, the brain starts to ignore the blurry image. The most effective treatment is patching the good eye. Treatment should begin at the earliest age possible.