Amblyopia is a unilateral or,less commonly,bilaeral reduction of best-corrected visual acuity (also referred to as corrected distance visual acuity) that cannot be attributed directly to the dffect of any structural abnormality of the eye or visual pathways Amblyopia signifies a failure of normal neural development in the immature visual system(see Chaper 5) and is caused by abnormal visual experience early in life resulting from one or a combination of the following.