Exotropia

Signs and symptoms

The earliest sign of exotropia is usually a noticeable outward deviation of the eye, which may initially be intermittent and occur when a child is daydreaming, tired, or not feeling well. The deviation can become more apparent when looking at distant objects. Squinting or frequent eye rubbing is common. Children often do not report double vision because the brain may suppress the image from the deviating eye, a process called suppression.

As the disorder progresses, the eyes begin to turn outward when viewing close objects as well. If untreated, the eye may turn continually, leading to loss of binocular vision or stereopsis. In young children, the brain may learn to ignore the misaligned eye's image, resulting in amblyopia (lazy eye) and impaired depth perception. In adults who develop strabismus, double vision can occur because the brain cannot ignore the image from the turned eye.

Adults who have had exotropia since childhood may adapt by using a blind-spot, avoiding double vision and increasing peripheral vision on the side of the deviating eye.

Causes

Scientists still do not fully understand why exotropia develops. Six eye muscles must work together to give the brain a single clear image.

If any of these muscles fails to function correctly, a form of strabismus can result. Strabismus is more frequent in children who have brain-related conditions like cerebral palsy, Down syndrome, hydrocephalus, or brain tumors. According to one study, children with exotropia face a three times higher risk of developing a psychiatric disorder than other children.

Treatment

A comprehensive eye examination, including ocular motility evaluation and assessment of internal ocular structures, allows accurate diagnosis. Glasses, patching therapy, exercises, or prisms may reduce or control the outward-turning eye in some children, but surgery is often required. Convergence insufficiency, a common form of exotropia, responds well to orthoptic vision therapy including exercises. Consecutive exotropia, which arises after initial esotropia (often from surgical overcorrection), can be addressed with further surgery or vision therapy; vision therapy shows promising results if the consecutive exotropia is intermittent, alternating, and of small magnitude.

Because of surgical risks and the fact that about 35% of people require at least one more surgery, many try vision therapy first. Surgery is recommended if exotropia is present for more than half of each day, increasing in frequency, significant during near viewing, or if binocular vision is being lost; it may also be indicated for headaches with no other cause. In very mild cases, exotropia may diminish with time. Evidence from systematic reviews shows clinical benefits for patching in children aged 12 months to ten years, but insufficient evidence regarding benefits of surgical interventions.