Treatment options in intermittent exotropia: a critical appraisal

Clinical opinions regarding treatment of intermittent exotropia (IXT) vary widely and there is controversy as to which treatment modality is most successful. This paper reviews the clinical literature related to five different treatment modalities used for IXT: overminus lens therapy, prism therapy, occlusion therapy, extraocular muscle surgery, and orthoptic vision therapy. Based upon review of 59 studies of treatment of IXT, and using each author's stated criteria for success, the following pooled success rates were revealed: over-minus lens therapy (N = 215), 28%; prism therapy (N = 201), 28%; occlusion therapy (N = 170), 37%; extraocular muscle surgery (N = 2530), 46%; and orthoptic vision therapy (N = 740), 59%. Success rates for IXT surgery differed depending upon whether a functional (43%) or cosmetic (61%) criterion was used to evaluate treatment success. These pooled success rates must be viewed carefully because nearly all the studies suffer from serious scientific flaws such as small sample sizes, selection bias, inadequately defined treatments and success criteria, absence of statistical analysis, and results reported in a manner that makes interpretation difficult. These problems indicate the need for a careful, circumscribed, and well controlled clinical trial to study the efficacy of different treatment modalities in remediating IXT.