Amblyopia is loss of visual acuity in one eye caused by lack of use of that eye in early childhood.
Causes, incidence, and risk factors
Amblyopia can be caused by any condition which causes one eye to be favored and the other ignored by the brain. Strabismus ( crossed eyes ), different refractive errors ( farsightedness , nearsightedness , astigmatism ) in the two eyes, and childhood cataract are common causes of amblyopia. The preferred eye becomes dominant and has normal vision. The non-favored eye is ignored by the brain to avoid a clash between the two different images from the eyes. As a result, the visual system in the brain for the non-favored eye fails to develop properly. Some time between ages five and ten, the brain stops growing and the condition becomes permanent. Strabismus is the most common cause of amblyopia, and there is often a family history of this condition.
Signs and tests
Amblyopia is usually easily diagnosed with a complete examination of the eyes. Special tests are usually not required.
Treatment
The primary treatment involves patching the normal eye to force use of the non-preferred, amblyopic eye. Sometimes, drops are used to blur the vision of the normal eye instead of putting a patch on it. Younger patients have more potential for the visual system of the brain to develop, and thus better potential for improved vision when amblyopia is treated. The underlying condition will also require treatment. If refractive error is the cause, glasses or contact lenses will be prescribed. If strabismus is the cause, this will require a program of treatment. (This is more fully described in the section on strabismus ). Children whose vision cannot be expected to fully recover should wear glasses with protective lenses of polycarbonate, as should all children with only one good eye caused by any disorder.
Expectations (prognosis)
When treatment starts before age 5, near complete recovery of normal vision is possible. This becomes progressively less likely as children become older. Only partial recovery can be expected after age ten.
Calling your health care provider
Call for an appointment with your health care provider or ophthalmologist if a vision problem is suspected in a young child.
Prevention
Early recognition and treatment of the problem in children can help to prevent permanent visual impairment. All children should have a complete eye examination at least once between age three and five to avoid the risk of allowing unsuspected amblyopia to go beyond the age where it can be treated successfully.