Effect of isolated inferior oblique muscle myectomy in the management of superior oblique muscle palsy.

Thirty-three patients with superior oblique palsy were treated with an inferior oblique myectomy temporal to the inferior rectus muscle. The mean effect of surgery was 11.91 +/- 1.38 in all positions of gaze and for all age groups. The operative result in both children and adults was the same. The mean effect of surgery correlated with the size of the preoperative hyperdeviation in the fields of action of both inferior and superior oblique muscles. Inferior oblique muscle myectomy was followed by return of normal function to the superior oblique muscle in 63% of cases. Ocular torticollis was eliminated in 90% of the patients. Persistent overaction of inferior oblique muscle was encountered in three patients. Postoperative underaction of the myectomized muscle was not observed in any of our patients. A myectomy is recommended as a primary procedure in patients with superior oblique muscle palsy when the direct antagonist is overacting and the hyperdeviation is 10 to 15 prism diopters or more in primary position or the fields of action of the paretic superior oblique muscle or the overacting inferior oblique muscle.