The advancement of the medial rectus muscle for consecutive exotropia

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.

Retrospective cohort study.

Seventy-seven patients with consecutive XT that developed after surgery for infantile ET.

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.

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 XT at 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%.

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.