Surgical outcomes related to degree of unilateral lateral rectus muscle recession in intermittent exotropia of 20 prism diopters

Purpose: We compared the surgical results of different degrees of unilateral lateral rectus muscle recession (ULR) and investigated the surgical outcomes and factors related to recurrence of intermittent exotropia of 20 prism diopters (PD). Study design: Retrospective study. Methods: The study comprised 163 patients with intermittent exotropia of 20 PD who underwent ULR between January 2010 and May 2015 and at least 2 years of follow-up after the initial surgery. The patients were divided into 3 groups according to the extent of ULR (8.0, 8.5, or 9.0 mm), and the surgical results were compared. We investigated the surgical outcomes and factors related to recurrence. Results: The mean postoperative follow-up period was 3.89 ± 1.82 years. The rate of recurrence within 2 years differed clinically (8.0 mm: 25.7%; 8.5 mm: 19.0%; 9.0 mm: 8.6%). However, other factors did not significantly differ among the groups. The comparison of the recurrence and the nonrecurrence groups showed that the age at the time of surgery varied significantly (recurring: 6.5 years, nonrecurring: 8 years; P = 0.012). A younger age at the time of surgery and a ULR of 8.0 mm were significant risk factors for the recurrence of ULR in intermittent exotropia of 20 PD. Conclusion: We suggest that a surgical dose of 9.0 mm ULR is preferable to 8.0 mm ULR for intermittent exotropia of 20 PD.