Analysis of new attachment site in medial rectus resection with advancement using anterior segment optical coherence tomography

Objective: To evaluate the surgical outcome of unilateral medial rectus resection with small advancement for recurrent exotropia, ≤30 prism diopters (PD), and verify new attachment site anatomically using anterior segment optical coherence tomography (ASOCT). Method: This study is a retrospective chart review of patients who underwent 1.0 mm advancement of unilateral resected medial rectus from original medial rectus (OMR) insertion for recurrent exotropia since 2014. The age at operation, sex, preoperative angle of deviation, near stereopsis, and suppression were evaluated. Success was defined as ≤5 PD of esodeviation or ≤10 PD of exodeviation at the final visit. Preoperative scleral thickness was measured using ASOCT, 1.0 and 0.5 mm anterior to OMR insertion, and at the insertion. Results: A total of 76 patients, including 30 males (40.2%), were reviewed retrospectively. Continuous values were presented as mean ± standard deviation. Age at operation was 11.6 ± 6.6 years. The preoperative deviation was 20.9 ± 3.6 PD, and the amount of resected unilateral medial rectus was 4.5 ± 0.6 mm. The minimum required follow-up period after operation was 12 months after surgery. The postoperative follow-up period was 21.3 ± 8.0 months. A total of 65 patients (87.8%) showed successful outcome at the final visit. Preoperative scleral thickness at 1.0 and 0.5 mm anterior to OMR insertion site, and at OMR insertion site were 0.52 ± 0.05, 0.52 ± 0.06, and 0.43 ± 0.04 mm, respectively. Scleral thickness at OMR insertion site was significantly less compared with 1.0 and 0.5 mm from the OMR insertion site (p = 0.03). Conclusion: The scleral thickness 1.0–0.5 mm anterior to OMR insertion site was thicker that than at the OMR insertion site. The new technique of medial rectus resection with small advancement may be safer and more effective than conventional technique.