弱视，俗称为懒惰眼，是由于儿童在成长期间，视觉未有正常发展，眼球内部、外部均外无器质性病变。结果在长期失去刺激的情况下，大脑最终会放弃了该部份的视力功能，结果令视力减退，形成弱视。

Amblyopia, also called lazy eye, is a disorder of sight. It results in decreased vision in an eye that otherwise appears normal, or out of proportion to associated structural problems of the eye.

Whenever the brain does not receive visual signals from an eye for a long period of time, there is a risk of amblyopia. It also can occur when the brain "turns off" the visual processing of one eye to prevent double-vision, for example in strabismus (crossed eyes). The cause of amblyopia is within the brain.