Strabismus is a disorder in which both eyes do not line up in the same direction. Therefore, they do not look at the same object at the same time. The most common form of strabismus is known as "crossed eyes."

Causes

Six different muscles surround each eye and work "as a team." This allows both eyes to focus on the same object.

In someone with strabismus, these muscles do not work together. As a result, one eye looks at one object, while the other eye turns in a different direction and looks at another object.

When this occurs, two different images are sent to the brain -- one from each eye. This confuses the brain. In children, the brain may learn to ignore (suppress) the image from the weaker eye.

If the strabismus is not treated, the eye that the brain ignores will never see well. This loss of vision is called amblyopia. Another name for amblyopia is "lazy eye." Sometimes the lazy eye is present first, and it causes strabismus.

In most children with strabismus, the cause is unknown. In more than one-half of these cases, the problem is present at or shortly after birth. This is called congenital strabismus.