The advancement of the medial rectus muscle for consecutive exotropia

Objective: To characterize the dose effect of the advancement of the medial rectus muscle (MR) for consecutive exotropia (XT) after corrective surgery for infantile esotropia (ET) and provide a guide for achieving orthotropia. Design: Retrospective cohort study. Participants: Seventy-seven patients with consecutive XT that developed after surgery for infantile ET. Methods: All patients underwent advancement of the unilateral or bilateral MR and were followed up for at least 1 year. The angle of deviation and stereopsis were retrospectively reviewed from patient records. Results: At the time of surgery for infantile ET, the mean eso-angle was 52.2 +/- 13.10 prism diopters (PD; mean age, 28.5 +/- 16.97 months). The exo-angle of consecutive XT was 25.6 +/- 8.47 PD (mean age at surgery, 132.7 +/- 82.32 months). The mean deviation was 1.8 +/- 10.40 PD XTat the final follow-up (47.0 +/- 43.57 months). The corrective effect of the exo-angle for a 1-mm advancement of the MR was 3.1 PD at 1 year after surgery and 2.9 PD at the last follow-up. There was a significant positive relationship between the preoperative exo-angle and the corrective effect of the 1-mm advancement of the MR at the last follow-up (r = 0.367, p < 0.05). Postoperatively, orthotropia was present in 79.2% of patients, re-exodrift in 16.9%, and ET in 3.9%. Favourable stereopsis was achieved in 73.2%. Conclusions: MR advancement was effective for treating consecutive XT, followed by recession of the MR for infantile ET, achieving favourable stereopsis. The corrective value was 3 PD per 1-mm advancement of the MR.