Medial Rectus Advancement for Secondary Exotropia

Abstract

Purpose: To determine the preoperative characteristics and surgical results after medial rectus advancement in patients with secondary exotropia.

Design: Retrospective, interventional case series.

Methods: Setting: Tertiary Care University Medical Center. PatientPopulation: 221 patients with a diagnosis of secondary exotropia who underwent medial rectus advancement surgery by a single surgeon.

Observation: Preoperative demographics, exodeviation and motility, intraoperative findings, and postoperative results were recorded. MainOutcomeMeasure: Success of surgery, defined as Esotropia <15 prism diopters (pd) at postoperative week 1, or any deviation of <8 pd at postoperative month 2 (POM2).

Results: A total of 98 patients underwent unilateral medial rectus advancement (UMRadv), 89 underwent UMRadv with lateral rectus recession (LRc), and 34 underwent bilateral medial rectus advancement (BMRadv). POM2 success rates were 66.7% in UMRadv patients, 62.1% in UMRadv + LRc, and 56% in BMRadv. A total of 117 patients had preoperative adduction deficits, which were significantly associated with the finding of an intraoperative stretched scar (P < .001). Larger preoperative duction deficits were associated with larger stretched scars (P < .001). At POM2, the mean effect of surgery (pd of correction/mm) was 2.3 ± 1.4 pd/mm for UMRadv, 2.5 ± 0.8 pd/mm for UMRadv + LRc, and 2.8 ± 1.1 pd/mm for BMRadv. Patients with a stretched scar had significantly less correction per millimeter (2.2 ± 1.2 pd/mm) compared with those without (2.6 ± 1.2 pd/mm, P < .001). A total of 38.6% of patients experienced exodrift greater than 10 pd. Exodrift was significantly larger in the BMRadv group (P < .005).

Discussion: These results provide guidance for surgical correction based on preoperative deviation and ductions. Adduction deficits indicate a stretched scar, which must be treated with resection and advancement of the medial rectus. A larger amount of surgery is needed in patients with a stretched scar. Exodrift is common, and therefore aiming for approximately 10 pd of overcorrection at postoperative week 1 can improve final outcomes.

Conclusion: Medial rectus advancement results in successful surgical results at POM2 for secondary exotropia.