What is Strabismus?

In people with Strabismus, the eyes are misaligned and point in different directions. This visual defect may always be noticeable, or it may come and go. One eye may be directed straight ahead, while the other is turned in, out, up or down. The turned eye may straighten at times and the straight eye may turn.

About 4% of children in the United States have Strabismus, but it may also develop later in life. The condition occurs equally in males and females, and may run in families. However, many people with Strabismus have no relatives with the problem.

How does Strabismus affect vision?

In normal vision, both eyes are aimed at the same target. The visual function in your brain fuses the two pictures it receives into a single, three-dimensional image.

But when one eye turns, as in strabismus, the brain receives two different pictures. In young children, the brain trains itself to ignore the image of the misaligned eye and sees only the image from the straight, or best-seeing, eye. This causes loss of depth perception and two-eyed vision. About half the children who have strabismus experience this condition, known as amblyopia. If detected in the first few years of life, amblyopia can be treated by patching the preferred or better-seeing eye to strengthen and improve vision in the weaker eye.

Adults who develop Strabismus often have double vision because the brain is already trained to receive images from both eyes and cannot ignore the image from the turned eye.

What causes Strabismus?

The exact cause is not fully understood. We do know that to line up and focus both eyes on a single target, all six eye muscles in each eye must be balanced and working together with the corresponding muscles of the opposite eye. The brain controls the eye muscles, which explains why children with eye problems that affect the brain – such as cerebral palsy, Down syndrome, hydrocephalus and brain tumors – often have Strabismus. A cataract or eye injury that affects vision can also cause Strabismus.

How is Strabismus diagnosed?

Strabismus can be diagnosed during an eye exam. All children should have their vision checked by an optometrist or ophthalmologist by three years of age. If there is a family history of Strabismus or amblyopia, an ophthalmologist or optometrist can check vision even earlier than age 3.

How is it treated?

Treatment goals for Strabismus are to preserve vision, straighten the eye and restore two-eyed vision. After a complete eye examination, an eye doctor can recommend appropriate treatment. In some cases, eyeglasses can be prescribed for your child. Other treatments may involve surgery to correct the unbalanced eye muscles or to remove a cataract. Covering or patching the strong eye to improve amblyopia is often necessary.