Surgical outcome of single-staged three horizontal muscles squint surgery for extra-large angle exotropia

Purpose To report the surgical outcomes of 24 patients undergoing single-staged three horizontal muscles squint surgery for extra-large angle exotropia. Patients and methods Prospective case series of 24 consecutive patients with primary exotropia >60 prism diopters (PD) at distant and underwent single-staged three horizontal muscles squint surgery from 2003 to 2006. Surgery consisted of bilateral lateral rectus recession of 9.0 mm for 50 PD exotropic correction. For every 5 PD remaining angle exceeding 50 PD, we additionally performed 1.0 mm of unilateral medial rectus resection. The mean follow-up period was 15.8 months (range 6.0–38.0 months; SD 9.5 months). Results The mean age at surgery was 31.2 years old (range 7–78 years old, SD 18.2 years old). The mean distant preoperative deviation was 71.3 PD (range 60–85 PD, SD 7.7 PD). No limitation of eye movement or diplopia was found. The success rate was higher in the intermittent group (88.2%) than the constant group (42.9%) ( P =0.02) and in cases with preoperative deviation of 80 PD are warranted.