Strabismus is caused by one or more eye muscles functioning improperly, resulting in a misalignment of the eyes. Each eye has six muscles that work in unison to control movements. The brain controls the eye muscles to keep the eyes properly aligned. These muscles must function together for the brain to superimpose the two images it receives from each eye.

Strabismus must be detected early in children because they are so adaptable. If a child sees double, his or her brain quickly learns to suppress or block out one of the images to maintain single vision. In a short time, the brain permanently suppresses vision from the turned eye, causing a weak or amblyopic eye. Trauma, certain diseases and occasionally eye surgery can cause strabismus. It can also be inherited.

Common signs of strabismus are turned or crossed eyes, a head tilt or turn, squinting, and in some cases, double vision. Treatment depends on the patient's age, cause of the problem, and type and degree of the eye turn. Treatment may include patching, corrective glasses, prisms, vision therapy or surgery.