Lazy eye, also known as amblyopia, is reduced vision in one eye caused by abnormal visual development early in life. However, it is possible for adults to develop amblyopia as well. The most common cause of lazy eye in adults is an imbalance in the muscles that position the eyes, known as strabismus amblyopia. Strabismus is a condition in which the eyes are not aligned, and it can affect peoples ability to function and even cause them to lose their independence. Other causes of amblyopia in adults include a drooping eyelid, cataract, tumor blocking the entry of light into the eye, a large difference in refractive error between the two eyes, or other vision problems. Treatment for amblyopia is directed towards the underlying cause and may include surgical removal of the obstruction, correction of the drooping eyelid, cataract surgery, eyeglasses, contact lenses, or patching therapy.