Amblyopia, also known as "lazy eye," is a vision problem that affects just two to three percent of the population, but if left uncorrected, it can have a very big impact on their lives. Central vision does not develop properly, usually in one eye, which is called amblyopic. A related condition, strabismus, sometimes causes amblyopia.

Untreated amblyopia may lead to functional blindness in the affected eye. Although the amblyopic eye has the capability to see, the brain "turns off" this eye because vision is very blurred. The brain elects to see only with the stronger eye.

Amblyopia generally develops in young children, before age six. Its symptoms often are noted by parents or health-care professionals. If a child squints or completely closes one eye to see, he or she may have amblyopia. Other signs include overall poor visual acuity, eyestrain and headaches.

Trauma to the eye at any age can cause amblyopia, as well as a strong uncorrected refractive error (nearsightedness or farsightedness) or strabismus. It's important to correct amblyopia as early as possible, before the brain learns to entirely ignore vision in the affected eye.