Strabismus (crossed eyes) is a condition in which the eyes do not align properly. In other words, one eye is turned in a different direction than the other eye.

In normal conditions, the six muscles that control eye movement work together to point both eyes in the same direction. Patients with strabismus have problems with eye movement control and cannot maintain normal eye alignment.

Strabismus can be categorized by the direction of the turned or misaligned eye:

Other factors to consider that help determine the cause and treatment of strabismus:

Accommodative esotropia: This typically occurs in cases of uncorrected farsightedness and a genetic predisposition (family history) for the eyes to turn inward. Clear focusing can cause the eyes to turn inward. Symptoms include double vision, closing or covering one eye when looking at something close, and tilting or turning the head. This type of strabismus often begins in early childhood. It is usually treated with glasses but may also require eye patching and/or surgery on the muscles of one or both eyes.

Intermittent exotropia: In this type of strabismus, one eye fixes (focuses) on a target while the other eye points outward. Symptoms may include double vision, headaches, difficulty reading, eye fatigue, and closing one eye when seeing objects at a distance or under bright light. Patients may not exhibit symptoms while the eye deviation (difference) may be noticeable to others. Intermittent exotropia can occur at any age. Treatment may involve glasses, eye patching, eye exercises, and/or surgery on the muscles of one or both eyes.

Another type of strabismus is called infantile esotropia. This condition is marked by a significant inward turning of both eyes in infants that usually begins before six months of age. There is typically no significant amount of farsightedness present, and glasses do not correct the crossing. The inward turning may start intermittently but soon becomes constant in nature. It is present when the child is looking both near and far. Treatment for this type of strabismus is surgery on the muscles of one or both eyes to correct the alignment.

Adults can also experience strabismus. Most commonly, ocular misalignment in adults is caused by stroke, but it can also occur due to physical trauma or unresolved or recurrent childhood strabismus. Strabismus in adults can be treated in various ways, including observation, patching, prism glasses, and/or strabismus surgery.

It is estimated that four percent of the US population, or about 13 million people, have strabismus.

Most cases of strabismus result from an abnormality in the neuromuscular control of eye movement. Our understanding of these control centers in the brain is still evolving. Less commonly, there is an issue with the actual eye muscle. Strabismus is often inherited, with about 30% of children with strabismus having a family member with a similar problem.

Other conditions associated with strabismus include:

Strabismus typically appears in infants and young children, most commonly around the age of 3. However, older children and even adults can develop strabismus. The sudden onset of strabismus, especially with double vision, in an older child or adult may indicate a more serious neurological disorder. If this occurs, seek immediate medical attention.

A condition called pseudostrabismus (false strabismus) can make it appear that a baby has crossed eyes when, in fact, the eyes are looking in the same direction. Pseudostrabismus can be caused by excess skin covering the inner corners of the eyes and/or a flat nasal bridge. As the baby's face develops and grows, the eyes will no longer appear crossed.

If the eyes are not properly aligned, the following can occur:

In the case of children with strabismus, if the condition is detected in time and treated properly, it can result in excellent vision and depth perception and may safeguard against vision loss.