[Comparison of hang-back recession and conventional recession for correction of exotropia]

Background and objective: Weakening of the lateral rectus muscle to correct exotropia can be achieved by using a conventional or a hang-back recession. This study was conducted to compare the results of these techniques and to analyze the dose-response curve and complication rates.

Study design and methods: Patients who underwent a lateral rectus muscle recession for exotropia were included in this retrospective study. The recession was performed conventionally with direct scleral fixation at the desired point or with a hang-back recession, each combined with a plication of the ipsilateral medial rectus muscle. The study analyzed ocular alignment and motility preoperatively as well as 1 day and 3 months postoperatively. Intraoperative and postoperative complications were compared.

Results: A total of 50 patients (age 4-75 years) met the inclusion criteria for this study. A conventional recession of the lateral rectus muscle was performed in 30 patients and a hang-back recession in 20. Preoperative ocular alignment with distance fixation was - 33.8 ± 14.4 prism diopters (PD) in the conventional group and - 30.6 ± 11.8 PD (mean ± standard deviation) in the hang-back group (where negative values constitute exotropia and positive values are esotropia). Preoperative ocular alignment with near fixation was - 40 ± 15.2 PD and - 36 ± 14.7 PD for conventional and hang-back recession, respectively. Ocular alignment with distance fixation 3 months postoperatively was - 10 ± 14.1 PD in the conventional group and - 11.1 ± 13.2 PD in the hang-back group and with near fixation it was - 15.4 ± 13.9 PD and - 11.5 ± 13.9 PD, respectively. In the conventional group 1 mm of combined surgery corrected 2.03 ± 0.88 PD (- 0.31-4.15 PD/mm) of exotropia with distance fixation and 2.13 ± 0.87 PD (0.89-3.85 PD/mm) with near fixation. In the hang-back group, it corrected 1.83 ± 0.89 PD (0.42-2.95 PD/mm) and 2.32 ± 1.25 PD (0.17-4.76 PD/mm), respectively. Differences between groups were not statistically significant. Intraoperative complications, such as scleral perforation were not observed. Postoperative complications, particularly slipped or lost muscles or induced vertical strabismus were not documented in either group.

Conclusion: The hang-back recession is an effective and safe alternative to conventional recession of the lateral rectus muscle for exotropia. Larger studies with longer follow-up would be desirable to prospectively compare these two techniques.