To investigate the effect of inferior oblique (IO) myectomy by analyzing the correlation of the amount of inferior oblique overaction (IOOA), hypertropia and excyclotorsion before, between, and after IO myectomy in patients with various degrees of IOOA.

A total of 86 eyes from 59 patients with IOOA who underwent IO myectomy were enrolled in the present study. The correlation analysis was performed for the amount of IOOA, hypertropia and excyclotorsion before and after surgery, according to the preoperative amount of IOOA, hypertropia, and excyclotorsion.

The IOOA decreased from +2.5 ± 0.6 before surgery to -0.01 ± 0.25 ( p < 0.05) after surgery. The vertical deviation was 5.7 ± 6.3 prism diopter (PD) and 2.3 ± 5.2 PD ( p < 0.05) postoperatively. The amount of cyclodeviation was 15.3 ± 7.6° before surgery and 6.6 ± 5.7° ( p < 0.05) after surgery. The amount of surgical correction for IOOA and the hypertropia was significantly correlated with preoperative deviation ( p < 0.05, p < 0.05). The amount of excyclotorsion before and after surgery was also positively correlated but was not statistically significant ( p = 0.05).

IO myectomy can correct any degree of IOOA, hypertropia, and related excyclotorsion.