Long-term surgical outcomes of bilateral vs. unilateral medial rectus resection for recurrent exotropia

The objective of this study is to compare the long-term outcomes of bilateral and unilateral medial rectus (BMR/UMR) resection for recurrent exotropia after bilateral lateral rectus (BLR) recession.

Retrospective study was performed of 99 patients who underwent BMR resection (BMR group) or UMR resection (UMR group) for recurrent exotropia of 20-30 prism diopters (PD), with a minimum follow-up of 5 years. Surgical outcomes including success rate, exodrift rate, and average effect of MR resection were compared between two groups. The risk factors associated with poor outcomes were evaluated.

At 5 years after surgery, 57% in the BMR group and 62% in the UMR group showed successful outcome. Success and recurrence rates were not significantly different between two groups, whereas the overcorrection rate was significantly higher in the BMR group (35% vs. 15%; p = 0.039). The average effect of MR resection was significantly greater after BMR throughout the whole postoperative period. The average effect of UMR resection was significantly greater in those who had previously undergone a large amount of BLR recession compared with those with a smaller dosage (p = 0.006). By multivariate analysis, a large amount of previous BLR recession and initial overcorrection of >10 PD of esotropia were found to be significant risk factors of overcorrection.

In moderate angles of recurrent exotropia, large UMR resection is a safe and efficient procedure. However, if a large BLR recession was performed previously, surgical dosage for UMR resection should be reduced because of the high risk of long-term overcorrection.