Assessment of central and peripheral fusion and near and distance stereoacuity in intermittent exotropic patients before and after strabismus surgery

Abstract

PURPOSE: To determine whether central fusion and distance stereoacuity are useful as objective measures in assessing the need for and success of surgery for intermittent exotropia (X[T]). METHODS: A prospective, institutional, clinical trial was conducted of 26 consecutive patients with X(T) who were undergoing strabismus surgery in whom fusion (central and peripheral) and stereoacuity (at near and distance) were assessed preoperatively and postoperatively, as well as in 112 normal subjects. To obtain accurate measurements with sensory tests, the lower age was limited to 5 years for inclusion. A successful surgical alignment was defined as an exotropia of 10 prism diopters or less at 6 m. Sensory and motor outcome measures were determined 1 year after surgery. RESULTS: The successful surgical alignment rate was 69%. All patients with X(T) demonstrated peripheral fusion, whereas 35% demonstrated central suppression preoperatively and postoperatively. Central fusion was not predictive of surgical outcome (P = .078); however, there was a trend toward less surgical success in patients with central suppression. Patients with X(T) exhibited good near stereoacuity before and after surgery. Distance stereoacuity in patients with X(T) preoperatively was significantly diminished compared with normal subjects (P < .001) and was improved in 58% postoperatively. Patients who achieved successful surgical alignment had a greater likelihood of demonstrating distance stereoacuity improvement postoperatively than patients who failed to achieve successful surgical alignment (P = .003). Patients with central suppression were unlikely to improve their distance stereoacuity postoperatively (P = .014). CONCLUSIONS: Successful surgery may improve distance stereoacuity. Better distance stereoacuity and central fusion are frequently associated with better surgical success in X(T).