The Effect of Myectomy on the Grading of Overaction of the Inferior Oblique Muscle.

Purpose: This study assesses the surgical results of inferior oblique myectomy on the degree of overaction in patients with overaction greater than +2 of the inferior oblique muscle. Methods: Seventy eyes of 54 patients underwent an inferior oblique myectomy and at least 6 months of follow-up. Patients with contracture of the superior rectus muscle or dissociated vertical deviation were excluded. The chief complaints, preoperative and postoperative degrees of overaction of the inferior oblique muscle, the angle of hypertropia, and head tilt were analyzed. Results: Deviation of the eyeball (38.9%) and head tilt (25.9%) were the most common complaints. Overall, the success rate was 91.4%, and the likelihood of success decreased with increasing severity of overaction of the inferior oblique muscle. The angle of hypertropia reduced from 11.9 (Prism diopters, PD) preoperatively to 2.2PD postoperatively (p=0.000). Preoperative head tilting was seen in 20 patients (37%) and all saw postoperative improvement. Conclusions: Inferior oblique myectomy is effective in treating the overaction of the inferior oblique muscle without contracture of the superior rectus muscle or dissociated vertical deviation, especially in patients with greater than +2 overaction of the inferior oblique muscle.