Anterior Transposition of the Inferior Oblique Muscle for Treatment of Superior Oblique Palsy

PURPOSE: Weakening of the inferior oblique muscle is the procedure of primary importance in patients with superior oblique palsy, Knapp's Classes I and III. In this study, the effectiveness of anterior transposition of the inferior oblique muscle in treatment of these patients was evaluated. METHODS: Sixteen patients with superior oblique palsy, Knapp's Classes I and III, underwent anterior transposition of the inferior oblique muscle. The tip of the disinserted muscle was sutured to the sclera, parallel, and adjacent to the lateral border of the inferior rectus muscle insertion. The prism and alternate cover test measurements were made in all cardinal positions of gaze before and 6 months after surgery. RESULTS: The mean reduction of hyperdeviation was 15 prism diopters (PD) in the primary position, 23.4 PD in adduction, 26.65 PD in elevation and adduction, and 18.63 PD in depression and adduction. There was no hypotropia in the primary position. Mild limitation of upgaze has occurred in 3 of these patients, and mild fullness of the lower lid was developed by 25%. Postoperative hyperdeviation in the primary position was 5 PD or less in 15 out of 16 patients. CONCLUSIONS: The anterior transposition of the inferior oblique muscle is very effective in eliminating hyperdeviation in patients with superior oblique palsy, Knapp's Classes I and III. Up to 25 PD reduction of hyperdeviation in the primary position can be achieved. If this type of anterior transposition is used, primary position hypotropia or marked limitation of upgaze possibly will not occur.