Strabismus

What is strabismus?

Strabismus is a condition in which the eyes point in different directions. Usually one eye is pointed straight ahead and the other is pointed in, out, up, or down.

With normal vision, the brain fuses the images from two eyes that are aimed at the same target into one clear image (called binocular vision). With strabismus, two different images are sent to the brain. In a young child, the brain starts to ignore the image from the turned eye, and the child loses depth perception and vision in the turned eye. Adults who develop strabismus often have double vision because the brain is used to receiving two images and cannot easily ignore the image from the turned eye.

Some types of strabismus are:

• esotropia or "crossed eye"--an eye turns in
• exotropia or "wall" eye--an eye turns out
• hypertropia--an eye turns up
• hypotropia--an eye turns down.

How does it occur?

Strabismus occurs when the eye muscles are not balanced. The movements of the muscles of one eye do not match those of the other eye.

Sometimes the cause of eye muscle imbalance is not known. Children may be born without the ability to keep the eyes together. Children with other conditions such as cerebral palsy or Down syndrome often develop strabismus.

Strabismus in adults may be caused by:

• strabismus from childhood that recurs
• poor vision in one eye, which begins to drift outward
• a concussion (injury to the brain)
• an injury to nerves that control eye muscle movement, sometimes as a result of a disease or other medical condition (such as, high blood pressure or diabetes).

What are the symptoms?

The person's eyes appear to be looking in different directions all or part of the time. Other symptoms include turning or tilting the head or squinting one or both eyes.

Babies younger than 3 months old may appear to look in different directions for a few moments, often just before going to sleep. This does not always mean they have strabismus. However, if the eyes appear to be misaligned constantly by age 2 months or misaligned part of the time by age 3 months, the baby should be checked by an ophthalmologist (medical eye doctor). Children do not outgrow true strabismus.

How is it diagnosed?

Parents, caregivers, or family members usually notice that the eyes are not pointed in the same direction. The eye doctor will test the vision and ability to follow objects with each eye. The eye doctor will also examine the eyes for any signs of disease.

How is it treated?

The goals of treatment for strabismus are to:

• correct any vision problems
• straighten the eyes and restore the ability to make normal eye contact.

In children, treatment should begin as soon as the condition is diagnosed. Treatment that begins after age 6 may improve a child's appearance but not always his vision.

Treatment of strabismus includes:

• Patching or using special eyedrops in the good eye. This treatment forces the brain to pay attention to the weak eye. Then it works harder and develops more normally.
• Glasses. Glasses are used to correct farsightedness or to improve the focus of the eyes. An eye with poor vision is more likely to drift. Farsighted children have to work harder to focus their eyes. This can cause the eyes to cross. Glasses that correct the farsightedness help keep the eyes from crossing while they are worn.
• Eye exercises. These exercises train the eyes to move together and focus on the same object at the same time. Unfortunately, most forms of strabismus do not improve with eye exercises.
• Prism glasses for adults. These glasses can sometimes eliminate double vision while they are being worn.
• Surgery on the eye muscles. Muscles may be loosened, tightened, or repositioned. If this surgery is done early enough in some children, they may develop normal vision. Strabismus surgery is not cosmetic surgery. Having eyes that are not aligned normally interferes with a person's ability to communicate with others through eye contact.

Like any surgery, eye surgery has some risks. Your eye doctor can discuss those with you. The success of surgery will depend partly on whether the coordination between the eyes and brain is good enough to keep the eyes locked on target and in proper alignment. If proper alignment is not achieved or if strabismus develops again, more surgery may help.

How can I take care of myself?

It is important that you and your children have routine eye exams. Tell your doctor about any eye misalignment you notice in yourself or in family members. If your eye doctor recommends patching or any other treatment, follow his or her instructions exactly.