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 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. Exotropia will normally begin as an intermittent problem, only noticed 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 detected during a routine eye exam.
Squinting in bright light is another sign frequently seen in children. 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. Eye muscle surgery will be recommended if the drifting is frequent and severe enough.
If exotropia goes uncorrected, it may worsen to the point that the eye becomes deviated much or all of the time. The eye is then is at risk for developing amblyopia or “lazy eye,” which is loss of vision because of disuse.
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 is present, 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.
Glasses rarely have any effect on improving exotropia, but they are occasionally prescribed in children with exotropia and a refractive error.
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.