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Help of pediatric ophthalmologist crucial in care of intermittent exotropia
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Exotropia occurs in about 1% of the population. The most common form is intermittent exotropia, representing more than 75% of cases. Most of us have a small exophoria, and when fusion is broken, this can manifest as an exotropia with temporary diplopia. It can be induced at will, and it also occurs in many under the influence of alcohol or other sedatives.
Significant intermittent exotropia with a prolonged break in fusion is a common form of strabismus in children, and it usually manifests by 12 months of age. Because the tropia is intermittent, the good news is that patients do not usually develop dense amblyopia, although most manifest a dominant eye and it is usually the nondominant eye that turns outward.
Most pediatric ophthalmologists delay surgical treatment of intermittent exotropia until the patient is 5 years of age or older, which works well with school attendance onset. In the interim, some will recommend patching for 4 to 6 hours a day, usually of the dominant eye, but some specialists recommend patching in an alternate eye fashion. This patching in some cases reduces the amount of time one eye is exodeviated, but this benefit is usually short lived.
The decisions to patch or not and how frequently and for what length of time are topics of much debate, and most of us rely on a pediatric ophthalmologist to help formulate the patching plan. It is critical to prevent the development of any amblyopia, which can occur if the deviation transitions from intermittent to a more permanent state. The same dependence on subspecialist advice is true for the timing and type of surgery that is recommended, and while muscle surgery is most frequently selected, this is a diagnosis in which botulinum toxin injections have been effective.
For the comprehensive ophthalmologist, the challenge is to make the diagnosis, and in many cases, pictures of the child at home can be helpful, because all may be normal when the child is seen in the office. An hour of patching in the office can sometimes help elucidate the diagnosis, and there are other tests using plus lenses to break fusion that can be reviewed in standard textbooks.
If intermittent exotropia is diagnosed, a careful refraction, including cycloplegia, is important, and even small refractive errors should be corrected. Some doctors will slightly over-minus the patient’s glasses to induce a small amount of accommodation and secondary convergence, but the value of this approach has not been confirmed. Of course, a complete eye examination is in order to rule out any other pathology, but usually the eyes are normal.
Prisms are rarely helpful because the deviation is intermittent and usually variable in prism diopters. Other than in older patients with accommodative insufficiency, vision training exercises have not been proven beneficial. Vision training for the child with intermittent exotropia is almost never recommended by a pediatric ophthalmologist, but many optometrists remain supportive and it is not uncommon to share a patient in which vision training is being recommended and performed by an optometric colleague.
The management of this awkward situation with the family, pediatric ophthalmologist and vision training doctor can be difficult. The key issues for the comprehensive ophthalmologist include make the diagnosis, treat any refractive error with glasses, be vigilant that amblyopia is prevented with patching as needed, and treat surgically when persistent or progressive, usually at the age of 5 years or later.
Most of us enjoy the help of a pediatric ophthalmologist in this process, and many of us simply transfer the care to a subspecialist if one is available nearby.