Interventions for intermittent exotropia

Hatt S, Gnanaraj L

Summary

Treatment for a type of childhood squint where one or both eyes intermittently turn outwards

A squint is a condition in which the eyes are out of alignment, that is one eye looks straight ahead whilst the other eye turns inwards, outwards, up or down. In most cases squint is present constantly but about 25% of children develop a type where an eye intermittently drifts outwards, typically more so when looking into the distance, when tired or day-dreaming. This is called intermittent exotropia (X(T)). When the child focuses on something close, the eye usually moves back to the centre. Constant squint that develops in childhood results in permanent loss of the ability to use the eyes together as a pair. In X(T) this ability is retained during periods when the squint is controlled but one eye is 'suppressed' when the squint occurs. Treatment is usually sought by the child's parents/ carers in order to improve the appearance; less commonly it is undertaken principally to realign the eyes in order that they work as a pair. Treatment typically consists of surgery on the muscles around the eye: it may be either on the outside muscle of both eyes or on the inside and outside muscle of one eye. Exercises are thought to strengthen the muscles and correct small degrees of squint; sometimes patching or glasses for shortsightedness can be tried in the short term. There is currently not a clear understanding of which treatments work most effectively and when any treatment should be given. We searched for studies where subjects with X(T) had been randomised to receive a particular treatment. The aim was to establish which treatments were most effective at correcting the squint without adversely affecting any existing ability to work the eyes together. The one included study in this review compared surgery on one eye to surgery on both eyes for the basic type of X(T) and found that surgery on one eye was more effective. There are many other studies in the current literature but the methodology employed makes it impossible to reliably attribute the reported effect to the intervention. There is a clear need for further randomised studies to provide more reliable evidence for the management of this condition.