To evaluate the efficacy of combined resection and anterior transposition of the inferior oblique muscle for treatment of unilateral superior oblique palsy with 20-25 prism diopters (PD) hypertropia in primary position.

Surgery was performed on 27 patients with unilateral superior oblique palsy and 20-25 PD hypertropia in primary position. All of the patients had overaction of the inferior oblique muscle. The inferior oblique muscle was disinserted and 4mm of its distal end was resected. It was transposed to the lateral border of the inferior rectus muscle insertion. The alternate prism and cover test was used to measure the hypertropia. The surgical result was evaluated 6 months later.

The mean hypertropia in primary position was 22.6±0.4 PD preoperatively, which decreased to 1.4±0.6 PD after operation. None of the patients developed hypotropia in primary position. Mild limitation of elevation was recorded in one patient. Four patients developed lower lid fullness.

Combined resection and anterior transposition of inferior oblique muscle is an effective treatment for unilateral superior oblique palsy with 20-25 PD hypertropia in primary position.