Comparison of Long-term Surgical Outcomes of Two-muscle Surgery in Basic-type Intermittent Exotropia: Bilateral versus Unilateral

PURPOSE: To compare long-term surgical outcomes after bilateral lateral rectus recession (BLR) and unilateral lateral rectus recession-medial rectus resection (RR) for the treatment of basic-type intermittent exotropia. METHODS: Consecutive patients who underwent BLR or RR for treatment of intermittent exotropia between 1999 and 2010 and underwent ≥5 years of follow-up were recruited for this study. Surgical outcomes were grouped according to postoperative angle of deviation: overcorrection (esophoria/tropia >8 prism diopters [Δ]), success (esophoria/tropia ≤8Δ to exophoria/tropia ≤8Δ), and undercorrection/recurrence (exophoria/tropia >8Δ). Outcomes were compared between the BLR group and the RR group at postoperative week 1, months 1 and 6, and years 1, 2, 3, 4, and 5. RESULTS: Of 99 patients, 37 underwent BLR and 62 underwent RR. At postoperative month 6 (97.3% vs. 82.3%, p = 0.045) and year 1 (91.9% vs. 74.2%, p = 0.040), the surgical success rates in the BLR group were significantly higher than in the RR group. Recurrence of exophoria/tropia most commonly occurred between 2 and 3 years after surgery in the BLR group, but continuous recurrences were found in the RR group. At postoperative year 5, the surgical success rate was 54.1% in the BLR group and 41.9% in the RR group (p = 0.403). The reoperation rate was 24.3% in the BLR group and 33.9% in the RR group (p = 0.317). CONCLUSIONS: Surgical outcomes 5 years after surgery for intermittent exotropia were comparable between the BLR and RR groups. The surgical success rate and the reoperation rate were not significantly different between the BLR and RR groups.