Isolated inferior oblique weakening procedure is an effective treatment for patients with superior oblique muscle palsy who had up to 15 prism diopters (PD) of vertical deviation in the primary position, but 2-muscle surgery is needed for patients with larger deviations. Herein, we report the surgical results of simultaneous 2-extraocular muscle surgery for large primary position hypertropia 16 PD or more caused by superior oblique palsy.

This study was a retrospective review of the records of patients who presented with central gaze hypertropia 16 PD or more and underwent simultaneous 2-extraocular muscle surgery between January 2003 and June 2014 in Severance Hospital. The patients were divided into 3 groups: 43 patients who underwent inferior oblique (IO) myectomy and contralateral inferior rectus (IR) recession (Group 1), 10 patients who underwent IO myectomy and superior rectus (SR) recession (Group 2), and 8 patients who underwent SR recession and contralateral IR recession (Group 3). Criteria for success included correction of head posture and a primary position alignment within 5 PD of vertical deviation.

Mean preoperative alignment at primary gaze was 25.5 ± 7.1 PD (range, 16-60 PD) compared to the postoperative value of –1.3 ± 6.8 PD (range, –20~25 PD) ( p < 0.001). Surgery was successful in 49 (80%) patients. Nine (15%) patients were overcorrected and the other 3 (5%) patients were undercorrected. Success rate was the highest in subjects who underwent IO myectomy and contralateral IR recession. Among the 24 patients who did not receive combined horizontal muscle surgery, horizontal deviations decreased from 10.4 ± 2.7 PD to 1.5 ± 5.5 PD ( p < 0.001)

Two-muscle surgery can be effective in patients with large hypertropia 16 PD or more. Additionally, horizontal deviations are more likely to be resolved with vertical muscle surgery alone. However, IO myectomy combined with ipsilateral SR recession can cause overcorrection postoperatively, so surgical dose should be reduced when performing weakening procedure of two elevators in one eye.