Exotropia is a specific type of strabismus (ocular misalignment) in which one or both of the eyes drift outward. Exo-means "out" and tropia means "to turn".

Exotropia can begin at any age, as early as the first few months of life or at any time during childhood. Parents may notice one eye drifting out or both eyes drifting out at different times. Normally exotropia will begin as an intermittent problem. Often it initially will be seen when the child is tired, sick, just waking up, excited or stressed. At other times, it may not be noticeable to parents but may be during a routine eye exam.

Another sign frequently seen in children is squinting in bright light. This occurs because the child tries to squint or close the deviating eye in bright sunlight. At times this may be the only sign of exotropia. When one eye is deviated outward, it is ignored by the brain.

Children with exotropia do not see double. Exotropia normally gets worse over time, although occasionally the problem stays the same throughout childhood. It is extremely rare for the problem to go away spontaneously. Progression of the exotropia occurs when the outward deviation of the eye occurs more frequently and/or the amount of misalignment increases. If the drifting is frequent and severe enough, eye muscle surgery will be recommended.

If exotropia goes uncorrected, it may worsen to the point that the eye becomes deviated much or all of the time. In this instance that eye is at risk for developing amblyopia or "lazy eye", which is loss of vision because of disuse. Therefore, it is essential to correct exotropia before it becomes a constant problem.

Some children may have amblyopia or "lazy eye" of the drifting eye even if the exotropia has not yet become constant. If the eye is deviating frequently, the eye will not be used and loss of depth perception (stereopsis) and loss of vision (amblyopia) may ensue.

If amblyopia or "lazy eye" is present, then patching will be required to improve the vision in addition to eye muscle surgery to correct the drifting. The frequency and duration of patching will depend on the severity of the amblyopia. Patching frequently must be continued after surgery. Occasionally, glasses may also be prescribed in children with exotropia if they also have a refractive error. However, glasses rarely have any effect on improving exotropia.

Surgical correction of exotropia is straightforward. It normally involves weakening or "loosening" one or both outer (lateral rectus) muscles. Unless the drifting is small, both outer muscles will need to be weakened even if only one eye drifts out, or if one eye drifts out more than the other.

by David R. Weakley, Jr., M.D.

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