Loss of visual acuity in the non-dominant eye caused by lack of use of the eye in early childhood.
Causes and risks
Amblyopia may 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, or childhood cataract are common causes of amblyopia. The preferred eye becomes dominant and has normal vision. but the non-favored eye is ignored by the brain, and the visual system in the brain for that 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.
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.
Amblyopia should be suspected in a child if any of the following are seen:
Eyes that turn in or out, Eyes that do not appear to work together, Lack of depth perception
The primary treatment involves patching the normal eye to force the use of the non-preferred amblyopic eye. Sometimes drops may be used to blur the vision in normal eye instead of patching. Younger patients have more potential for the visual system of the brain to develop, and thus better potential for improvement in 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 from any cause.
When treatment is begun before age 5, 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.
Complex problems with muscle alignment may require several surgeries.