Unilateral inferior oblique muscle myectomy and recession in the treatment of inferior oblique muscle overaction: A longitudinal study

Abstract

Background. The comparable long-term outcomes of inferior oblique muscle myectomy and recession for the treatment of superior oblique underaction (in primary position and straight right and left gaze) have not been well documented in the literature. The purpose of this study was to compare longitudinally these two procedures in a similar, patient population with binocular single vision, when both operations were performed by the same surgeon, with a minimum follow-up period of 12 months. Methods. A total of 24 patients who randomly underwent either a unilateral myectomy (at the temporal border of the inferior rectus muscle) or a standard recession for inferior oblique muscle overaction associated with long-standing superior oblique underaction were evaluated preoperatively at 2 weeks, 4 months, and 12 months postoperatively by the same orthoptist. Results. A total of 23 patients met the study criteria, (12 myectomies and 11 recessions). All but one patient had demonstrable binocular single vision. The average preoperative hyperdeviation in contralateral gaze was 26.5 prism dioptres (Δ) in the myectomies and 20 Δ in the recessions. This was reduced at 12 months postoperatively to 1.75 Δ in the myectomies and to 3 Δ in the recessions. Both procedures were largely self-grading, so that the larger the preoperative hyperdeviation, the greater the effect of surgery. Conclusions. Single inferior oblique muscle-weakening procedures were effective in the vast majority of patients, even when the preoperative primary position hyperdeviation was 15 Δ or more. An improvement occurred in both groups immediately after surgery and in many throughout the follow-up period represented by a continuing drift towards orthotropia, but there was a recurrence of the hyperdeviation in some of the recession patients.