Trial of Vision Therapy for Intermittent Exotropia

The main objective of this randomized trial comparing vision therapy to observation is to determine the short-term effectiveness of vision therapy on distance intermittent exotropia control. The results will help determine whether to proceed to a full-scale, long-term randomized trial.

Major Inclusion Criteria- * Age 8 - 16 years * Intermittent exotropia meeting all of the following: * Distance exodeviation of 15∆ to 35∆ by prism alternating cover test (PACT) * IXT, exophoria, or orthophoria at near * Near exodeviation that does not exceed the distance exodeviation by more than 10∆ * Mean distance control score of 2 points or more with at least one measure being 3 points or higher * Mean near control score less than 5 points * Random dot stereopsis of 200" or better on Preschool Randot Stereotest * Willingness to accept randomization and no plan to relocate in the next 6 months Major Exclusion Criteria- * Treatment for IXT or amblyopia (other than refractive correction) within 3 months prior to enrollment * Office-based vision therapy for IXT within 6 months prior to enrollment * Prior office-based vision therapy for IXT of ≥10 sessions * Prior strabismus, intraocular, or refractive surgery (including BOTOX injection)