Strabismus is a visual defect in which the eyes are misaligned and point in different directions. One eye may look straight ahead, while the other eye turns inward, outward, upward or downward.
You may always notice the misalignment, or it may come and go. The turned eye may straighten at times, and the straight eye may turn.
Strabismus is a common condition among children. About 4% of all children in the United States have strabismus. It can also occur later in life. It occurs equally in males and females. Also, strabismus may run in families.
The main symptom of strabismus is an eye that is not straight. Sometimes children will squint one eye in bright sunlight or tilt their head to use their eyes together.
The exact cause of strabismus is not fully understood. Six eyes muscles that control eye movement are attached to the outside of each eye. To line up and focus both eyes on a single target, all of the muscles in each eye must be balanced and working together. The brain controls the eye muscles. Strabismus is especially common among children with disorders that affect the brain, such as: cerebral palsy, Down's syndrome, hydrocephalus, and brain tumors.
The eyes of infants often appear to be crossed, though they actually are not. This condition is called pseudostrabismus. Young children often have a wide, flat nose and a fold of skin at the inner eyelid that can make the eyes appear crossed. This appearance of strabismus may improve as the child grows. A child will not outgrow true strabismus.
A ophthalmologist can usually tell the difference between strabismus and pseudostrabismus.
After a complete eye examination, an ophthalmologist 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.
Most common types of strabismus:
- Esotropia: It is the most common type of strabismus in infants, when the eye turns inward because the child does not use the eyes together. Esotropia is fixed with surgery.
- Accommodative esotropia: It occurs in farsighted children, usually two years or older. When the child is young, he or she can focus the eyes to adject for the farsightedness, but the focusing effort to see clearly causes the eyes to cross. Glasses reduce the focusing effort and can straighten the eyes. Sometimes bifocals are needed for close work.
- Exotropia: It is an outward turning of the eye. This occurs most often when a child is focusing on distant objects. The exotropia may occur only from time to time, particularly when a child is daydreaming, ill or tired. Parents often notice that the child squints one eye in bright sunlight. Although glasses, exercises or prisms may reduce or help control the outward turning eye in some children, surgery is often needed.
The eyeball is never removed from the socket during any kind of eye surgery. The opthalmologist makes a small incision in the tissue covering the eye to reach the eye muscles. Certain muscles are repositioned, depending on which direction the eye is turning. It may be necessary to perform surgery on one or both eyes.
Recovery time is rapid and people are usually able to resume their normal activities within a few days.
After surgery, glasses or prisms may be useful. In many cases, further surgery may be needed at a later stage to keep the eyes straight.
Strabismus surgery is usually an effective treatment for eye misalignment. However, it is not a substitute for glasses or amblyopia therapy.