Predictors of surgical success in patients with intermittent exotropia

Background In patients with moderate- to large-angle exotropic deviations, surgical correction remains the definitive treatment. The purpose of this study was to identify preoperative factors that correlate with surgical success and to produce a binomial model that predicts success based on preoperative factors. Methods We performed a retrospective review of patients with intermittent exotropia who underwent uniocular recession-resection surgery. Success was defined as ocular deviation ≤10 Δ exotropia and ≤5 Δ esotropia at distance at last follow-up (at least 3 months' postoperatively). Preoperative factors such as age at surgery, sex, visual acuity, spherical equivalent, prism fusion range, stereopsis, and ocular deviation were analyzed for correlation with success using binomial logistic regression. Results A total of 82 patients were identified (average age, 33 years; range, 3.7-81.6 years). Average prismatic deviation was 35 Δ at near and 34 Δ at distance. Average stereopsis was 167″. The average success rate was 58.5%. Univariate binomial regression revealed that patients with smaller angle of deviation at near (OR = 0.96, P  = 0.013) or distance (OR = 0.96, P  = 0.005), larger myopic refractive errors in terms of mean spherical equivalent (OR = 0.71, P  = 0.022) and spherical equivalent in the more myopic eye (OR = 0.75, P  = 0.029) contributed to success. A multivariate regression model was able to predict success with an accuracy of 72% (sensitivity, 81%; specificity, 58%; negative predictive value, 67%; positive predictive value, 74%). Conclusions A smaller preoperative angle of deviation and larger myopic refractive error correlated with success in uniocular intermittent exotropia surgery in our cohort. Larger deviations and more hyperopia correlated with lower success rates.