Bilateral vs Unilateral Medial Rectus Resection for Recurrent Exotropia after Bilateral Lateral Rectus Recession

PURPOSE: To compare outcomes after bilateral and unilateral medial rectus (BMR/UMR) resection for the treatment of recurrent exotropia after bilateral lateral rectus (BLR) muscle recession. DESIGN: Retrospective, cohort study. METHODS: Forty-four patients underwent BMR resection (BMR group) or UMR resection (UMR group) for recurrent constant exotropia of 25 prism diopters (PD) or less at distance after undergoing BLR muscle recession for intermittent exotropia in an institutional setting. The main outcome measures were final success rates and improvement in stereopsis and were compared between the groups. The risk factors for recurrence after reoperation also were evaluated. Secondary outcome measures were evaluated based on the drift of ocular alignment toward exodeviation after surgery (exodrift) from post, operative day 1. RESULTS: Thirteen (54%) of 24 patients in the BMR group had successful outcomes, 10 (42%) had overcorrection, and 1 (4%) had undercorrection at the last follow-up examination. Sixteen (80%) of 20 patients in the UMR group had successful outcomes, 2 (10%) had undercorrection, and 2 (10%) had overcorrection. The incidence of successful outcomes at the last follow,up examination and the incidence of recurrence were not significantly different between the 2 groups, whereas the incidence of overcorrection was significantly higher in the BMR group (P = .017). CONCLUSIONS: Large UMR resection is a safe and effective procedure in the treatment of small to moderate angles of recurrent exotropia after BLR muscle recession. The overcorrection rate was significantly lower after UMR resection than it was after BMR resection. (Am J Ophthalmol 2009;148:459-465. (C) 2009 by Elsevier Inc. All rights reserved.)