Lazy eye (amblyopia) is decreased vision that results from abnormal visual development in infancy and early childhood. Although lazy eye usually affects only one eye, it can affect both eyes. Lazy eye is the leading cause of decreased vision among children. Left untreated, vision loss may range from mild to severe. With lazy eye, there may not be an obvious abnormality of the eye. Lazy eye develops when nerve pathways between the brain and the eye aren't properly stimulated. As a result, the brain favors one eye, usually due to poor vision in the other eye. The weaker eye tends to wander. Eventually, the brain may ignore the signals received from the weaker or lazy eye. Usually doctors can correct lazy eye with eye patches, eyedrops, and glasses or contact lenses. Sometimes lazy eye requires surgical treatment.