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

PURPOSE: To determine whether central fusion and distance stereoacuity are useful as objective measures in assessing the need for and success of surge ry for intermittent exotropia (X[T]), METHODS: A prospective, institutional, clinical trial was conducted of 26 c onsecutive patients with X(T) who were undergoing strabismus surgery in who m fusion (central and peripheral) and stereoacuity tar near and distance) w ere assessed preoperatively and postoperatively, as well as in 112 normal s ubjects. To obtain accurate measurements with sensory tests, the lower age was limited to 5 years for inclusion. A successful surgical alignment was d efined as an exotropia of 10 prism diopters or less at 6 m, Sensory and mot or 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 suppr ession preoperatively and postoperatively, Central fusion was not predictiv e of surgical outcome (P = .078); however, there was a trend toward less su rgical success in patients with central suppression. Patients with X(TS exh ibited good near stereoacuity before and after surgery. Distance stereoacui ty in patients with X(T) preoperatively was significantly diminished compar ed with normal subjects (P < .001) and was improved in 58% postoperatively. Patients who achieved successful surgical alignment had a greater likeliho od of demonstrating distance stereoacuity improvement postoperatively than patients who failed to achieve successful surgical alignment (P = .003), Pa tients with central suppression were unlikely to improve their distance ste reoacuity postoperativeIy (P = .014). CONCLUSIONS: Successful surgery may improve distance stereoacuity. Better d istance stereoacuity and central fusion are frequently associated with bett er surgical success in X(T), (C) 1999 by Elsevier Science Inc. All rights r eserved.