A systematic review of the effectiveness of treatments in altering the natural history of intermittent exotropia

Evidence of effectiveness of interventions for treatment of childhood intermittent exotropia, X(T), is unclear. We conducted a systematic review to locate, appraise and synthesise evidence of effectiveness, including twelve electronic databases, supplemented with hand searches and expert contact. We included randomised controlled trials, quasi-experimental and cohort studies with a comparison group examining interventions for divergence excess, simulated divergence excess or basic type X(T) in children, up to and including 18 years of age, followed for at least 6 months. Dual data extraction and critical appraisal were conducted and a narrative synthesis undertaken. Eleven studies satisfied the eligibility criteria. Seven examined the comparative effectiveness of two surgical procedures; four compared surgery with other interventions, including botulinum toxin A therapy, orthoptic exercises, occlusion, binocular vision training and watchful waiting. The evidence retrieved was of limited extent and quality with differences across studies in terms of outcome assessment and most appropriate time-point for measuring long-term outcomes. There were mixed outcomes when comparing unilateral recession/resection (R&R) with bilateral lateral rectus recession (BLR) on improving angle of deviation, which makes it difficult to recommend either surgical option with confidence. While non-surgical interventions appear less effective in terms of improving angle of deviation, they are rarely associated with adverse outcomes. Given the limited evidence base, better designed studies are required to address the question of the most effective management for treatment of childhood X(T). Importantly, consensus is required on what constitutes a successful outcome as well as agreement on how this should be measured.