Amblyopia, commonly known as lazy eye, occurs when there is a lack of vision in one eye because the eye and the brain are not working together. The brain may start to ignore the image from the amblyopic eye. Amblyopia may result from a strabismus (crossed-eyes), difference in nearsightedness or farsightedness between eyes, as well as other preexisting eye conditions, such as cataracts, ptosis (drooping of the upper eyelid), and refractive problems. Amblyopia develops early, usually before age 6. The earlier it is diagnosed and treated, the better. Symptoms of amblyopia include: significant favoring of one eye, poor depth perception, and poor vision in one eye. Treatments for amblyopia include: patching the strong eye (this method forces the weaker eye to work harder, naturally strengthening its ability focus), contacts and glasses.