Selective surgery for intermittent exotropia based on distance/near differences.
Classic teaching suggests that surgery for intermittent exotropia should be based on distance/near differences. Divergence excess, according to tradition, should be treated with symmetric lateral rectus recessions; simulated divergence excess and basic deviations should be treated with a recess/resect procedure. This teaching, to our knowledge, has not been systematically tested.
                To evaluate the appropriateness of selective surgery based on distance/near differences and to determine if bilateral lateral rectus recessions affect the distance deviation more than the near deviation.
                Patients with basic type intermittent exotropia were randomized to 2 groups, those receiving either unilateral recess/resect procedures or symmetric lateral rectus recessions. Patients with simulated divergence excess intermittent exotropia received symmetric lateral rectus recessions. Outcome was observed 1 year after surgery.
                Of 19 patients with basic exotropia receiving lateral rectus recessions, 10 patients (52%) had a satisfactory outcome compared with 14 (82%) of the 17 patients who had recess/resect procedures (P<.05). Of the 68 patients with simulated divergence excess, 55 patients (80%) had a satisfactory outcome after bilateral/lateral rectus recessions. This result was significantly better than the outcome for patients with basic exotropia who underwent lateral rectus recessions (P<.05) [corrected]. The decrease in the distance/near difference after surgery was essentially identical for patients with basic exotropia who underwent lateral rectus recessions as for those who received recess/resect procedures (means, 2.4 prism diopters vs 2.1 prism diopters, respectively).
                Although this study did not evaluate increasing the amount of symmetric lateral rectus recessions for patients with basic exotropia, these data suggest that patients with basic type intermittent exotropia should be treated with recess/resect procedures. Data also suggest that patients with simulated divergence excess do well with lateral rectus recessions. Recess/resect procedures and symmetric surgery affect distance/near differences equally in patients with basic exotropia.
The available literature consists mainly of retrospective case reviews, which are difficult to reliably interpret and analyse. The one randomised trial included found unilateral surgery more effective than bilateral surgery for basic intermittent exotropia. However, across all identified studies, measures of severity and thus criteria for intervention are poorly validated, and there appear to be no reliable natural history data. There is therefore a pressing need for improved measures of severity, a better understanding of the natural history and carefully planned clinical trials of treatment to improve the evidence base for the management of this condition.