Amblyopia is the loss of an eye's ability to see details. The condition appears in one eye. The cause is by lack of use of that eye in early childhood.

Amblyopia can be caused by any condition that causes one eye to be favored, and the other ignored by the brain. Strabismus (crossed eyes), farsightedness, nearsightedness, and astigmatism in both eyes, and childhood cataracts are common causes of amblyopia.

The preferred eye becomes 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 does not develop properly. Between ages 5 and 10, 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.

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
• Inability to judge depth correctly

Amblyopia is usually easily diagnosed with a complete examination of the eyes. Special tests are usually not required.