Comparison between Modified Bilateral Lateral Rectus Recession and Augmented Unilateral Recession-resection for Convergence Insufficiency Exotropia

Purpose: To compare the surgical outcomes between modified bilateral lateral rectus muscle (BLR) recession and augmented unilateral recession-resection (R&R) for the convergence insufficiency intermittent exotropia (IXT). Methods: 37 patients with convergence insufficiency IXT were divided into two groups: 13 patients (underwent BLR recession) and 24 patients (underwent unilateral R&R). Success was defined as within 10 prism diopters (PD) at distance and near, and within 10 PD of the difference between them at postoperative 12 months. Results: After the patch test, the preoperative distance deviation angle in the BLR group was 29.9 +/- 8.4 PD, and the near deviation angle was 42.3 +/- 9.7 PD; the difference between them was 12.5 +/- 3.2 PD. In the R&R group, the preoperative distance deviation angle was 26.7 +/- 5.8 PD, and the near deviation angle was 41.5 +/- 7.4 PD; the difference between them was 14.8 +/- 4.3 PD (p = 0.235, p = 0.987, and p = 0.123). At the 12-month follow-up in the BLR group, the distance angle was 3.8 +/- 5.1 PD, and the near deviation angle was 4.9 +/- 6.1 PD; the difference between them was 2.9 +/- 5.9 PD. In the R&R group, the postoperative distance deviation angle was 4.7 +/- 6.1 PD, and the near deviation angle was 7.9 +/- 6.6 PD; the difference between them was 3.65 +/- 5.1 PD (p = 0.708, p = 0.162, and p = 0.632, respectively). The surgical success rate did not differ significantly between groups at 12 months postoperatively (76.9%: BLR group and 70.8%: R&R group; p = 0.690). Conclusions: Modified BLR recession showed a similar surgical success rate to augmented unilateral R&R, and was effective in reducing both distance and near exodeviation, and in decreasing the difference between distance and near deviation in convergence insufficiency IXT.