Amblyopia is impaired vision due to lack of use of an eye when the brain favors the other eye. The most common causes of amblyopia are strabismus and anisometropia. In strabismus, the eyes are not aligned. The brain favors one eye over the other and the ignored eye is not adequately stimulated and the visual brain cells do not mature normally. Anisometropia occurs when the eyes have an unequal refractive power. One eye is myopic (nearsighted) and the other hyperopic (farsighted). Because the brain cannot reconcile this difference, it develops a preference for the image coming from one eye only.