Prevalence of Different Types of Intermittent Exotropia among Exotropic Children at Ain Shams University Ophthalmology Outpatient Clinic

Abstract

Exodeviation is a manifest outward deviation of the visual axes relative to each other, according to fusion control, exodeviation could be XT; being present all the time or X(T),where large exophoria intermittently breaks down to XT. Mechanisms responsible for these variations include the degree of fusional control with varying levels of alertness, the convergence-accommodation relationship and the change of the angle of deviation at different fixation distances. Exodeviation which is considered normal has a small angle of deviation, usually less than 10 PD, Most normal adults have a small exodeviation when fully dissociated. Exodeviations are controlled with our innate strong fusional convergence. Intermittent exotropia expresses early in childhood and rarely associated with neurological anomalies. The amblyopia is infrequent unless the disease progresses to constant XT. Intermittent exotropia is usually first observed by the parents in early childhood or late infancy as an infrequent drifting or squinting of one eye. Patients with X(T) tend to manifest their deviation when they are tired, have a cold or flu, which express as asthenopia, visual fatigue, and diplopia in older children and adults. many patients with X(T) have photophobia (squinting to bright light) which originally thought to be a way for eliminating diplopia or confusion.