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

Strabismus 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 of childhood onset strabismus the misalignment is present constantly, but in intermittent exotropia (X(T)) an eye intermittently drifts outwards (exotropia), typically more so when looking into the distance, when tired or day-dreaming. When the child focuses on something close, the eye usually moves back to the centre. In X(T) ability to use the eyes together as a pair (binocular single vision) is typically retained during periods when the exotropia is controlled and the image from one eye is switched off or 'suppressed' when the exotropia occurs. Treatment for X(T) may be sought to improve the appearance of misalignment or may be instigated if there is concern that it is worsening with potential or actual loss of binocular single vision. 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 to strengthen the muscles may sometimes be used; sometimes patching or glasses for short/ near sightedness can be tried. There is currently not a clear understanding of which treatments work most effectively and at what point any treatment should be given. We searched for studies where participants with X(T) had been randomised to receive treatment. The aim was to establish which treatments are most effective at correcting the exotropia without adversely affecting any pre-existing binocular single vision. 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 studies of X(T) in the current literature but the methods used do not allow reliable interpretation of the results. Furthermore there is a worrying lack of evidence regarding the natural history of X(T) and poor validation of measures of severity. There is a clear need for further randomised studies to provide more reliable evidence for the management of this condition.