Strabismus
Sherman Winston Reeves, M.D., M.P.H.

What is strabismus?

Strabismus is a condition in which the eyes are not properly aligned, and one or both eyes may turn up, down, in or out. The most common forms of strabismus are esotropia, in which the eyes appear crossed, and exotropia, in which the eyes appear wall-eyed or lazy. Strabismus may be intermittent, occurring only in some situations, such as when a person is tired or daydreaming. If the strabismus occurs at all times, though, it is termed constant.

What causes strabismus?

In children, strabismus is typically caused by improper development of the nervous system which controls the eye muscles. Occasionally, the eye muscles themselves may be faulty or an injury may have occurred to the eye socket or muscle which causes it to improperly turn the eye.

In adults, strabismus is typically caused from an acquired injury to the nerve that runs the eye muscle. In older adults, small strokes can occur in the eye muscle nerves or in the specialized parts of the brain that control the eye muscles, leading to strabismus. Injury to the eye socket is a common way in which younger adults can develop malfunction of the eye movement muscles and hence, strabismus.

Strabismus can also be caused by underlying medical conditions, such as thyroid disease and myasthenia gravis, in both children and adults. As such, a person with new or unexplained strabismus should have a full evaluation by their eye and medical doctors.

Why do some people with strabismus have double vision, but others do not?

In adults with strabismus, if the two eyes are constantly looking in different directions and cannot be brought together, double vision occurs. Children with strabismus, however, will ignore one eye and use the other for viewing. However, by ignoring one eye, a severe condition called amblyopia may occur in the ignored eye, in which a child’s brain doesn’t learn to process information from the ignored eye. Amblyopia can lead to permanent loss of vision in a child if it is not identified and treated early. As such, ALL children with strabismus should be evaluated by an eye doctor. If strabismus and amblyopia are allowed to persist through childhood, a person may continue to have misaligned eyes and one eye that is much weaker than the other, but my not have double vision since the weaker eye didn’t develop properly.

What can be done to treat strabismus?

For children, glasses can sometimes be used to treat mild forms of strabismus. However, if amblyopia is occurring with the strabismus, more aggressive treatments, such as patching the eye, may be needed. Surgery to realign the eye muscles is often needed to help resolve childhood strabismus, as it typically does not resolve on its own with time.

For adults, mild forms of strabismus resulting from small strokes may resolve with time. Patching one eye or using temporary, press-on prisms for one’s glasses can help relieve double vision symptoms in the short term. If the strabismus becomes chronic, prism ground into the eyeglass prescription may be a sufficient treatment for strabismus. Surgery to realign the eye muscles may be needed if prism fails to relieve the double vision symptoms, or if the deviated eye is cosmetically unacceptable.