Background. Bilateral medial rectus muscle recession with or without Cuppers' posterior fixation suture and recess and resect surgery are used to correct for large angle esotropia. There are only few reports on three muscle surgery (3MS). We analyzed the results of 3MS.

Patients and methods. Between June 2016 and May 2020, 61 patients received 3MS for esotropia >= 27 degrees (50 PD) together with oblique muscle surgery, if needed. Angles of strabismus were measured by simultaneous prism and cover testing (SPCT) and alternating prism and cover testing (APCT) at 5 m and 0.3 m. Grading was around 0.51 mm/degree (at 5 m). Medium-term results of 57 patients were available.

Results. Medians and ranges (min-max) were: age, 6 years (3-56 years). Preoperative APCT, far 34 degrees (27-45 degrees), near 36 degrees (27-50 degrees). Amount of surgery, 17 mm (15-21 mm), oblique muscle recession in 21 cases. The APCT after 5 months (3-24 months), far 2 degrees (-10-18), near 2 degrees (-8-18). Success rates (absolute deviation <= 6 degrees [10 PD]), APCT far 68%, near 67%, SPCT far 79%, near 74%. Exotropia > 6 degrees occurred in 4 cases (7%) at far and 3 (5%) at near, esotropia > 6 degrees in 14 cases (25%) at far and 16 (28%) at near.

Conclusion. The use of 3MS is a suitable first step procedure to correct for large angle esotropia.