Amblyopia

A permanent defect of visual acuity in which there is usually no structural abnormality in the eye. In many cases, there is a disturbance of the visual pathway between the retina and the brain. The term is also sometimes applied to toxic or nutritional causes of decreased visual acuity, as in tobacco–alcohol amblyopia. Amblyopia will develop if there is a marked discrepancy between the images received by the brain from each eye while vision is developing during early childhood. The most common cause is squint. Failure to form normal retinal images may also result from congenital cataract, and severe, or unequal, focusing errors, such as when one eye is normal and there is an uncorrected large degree of astigmatism in the other. Toxic and nutritional amblyopia may result from damage to the retina and/or the optic nerve. To prevent amblyopia due to squint, patching (covering up the good eye to force the deviating eye to function properly) is the usual treatment. Surgery to place the deviating eye in the correct position may be necessary. Glasses may be needed to correct severe focusing errors. Cataracts may be removed surgically. After the age of 8, amblyopia cannot usually be remedied.