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

Abstract

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.

Keywords: Exotropia; Operation; Strabismus.

Fig. 1. Mean angles of deviation at each postoperative time point in the bilateral lateral rectus recession (BLR) group and the unilateral lateral rectus recession-medial rectus resection (RR) group treated for basic-type intermittent exotropia. (A) The mean angle of deviation at distant fixation was more exotropic in the RR group than in the BLR group through the entire follow-up period, except for postoperative year 3. (B) The mean deviation at near fixation was also more exotropic in the RR group than in the BLR group through the entire follow-up period, except postoperative year 3. ^*p <0.05 by independent t-test.

Fig. 2. The proportions of each surgical outcome type at distant fixation for each postoperative time point in the bilateral lateral rectus recession (BLR) group (A) and in the unilateral lateral rectus recession-medial rectus resection (RR) group (B) for basic-type intermittent exotropia. Surgical outcomes at postoperative month 6 (p = 0.045) and year 1 (p = 0.040) differed significantly between the groups, demonstrating a higher success rate in the BLR group than in the RR group. ^*p <0.05 by Pearson's chi-square test.

Fig. 3. The percentages of recurrence at distant fixation for each postoperative time point in the bilateral lateral rectus recession (BLR) group and the unilateral lateral rectus recession-medial rectus resection (RR) group for basic-type intermittent exotropia. Analysis showed that recurrence was most common between postoperative years 2 and 3 in the BLR group, whereas it was most common within 6 months postoperatively in the RR group with continuous recurrences after surgery.

Fig. 4. Kaplan-Meier survival analysis for recurrence of exophoria/tropia more than 8 prism diopters in the bilateral lateral rectus recession (BLR) group and the unilateral lateral rectus recession-medial rectus resection (RR) group for basic-type intermittent exotropia. The analysis showed no statistically significant difference in the cumulative probability of survival between the two groups (p = 0.531, log-rank test).