Inferior oblique muscle myectomy versus anterior transposition in the management of unilateral superior oblique muscle palsy, a comparative study

Purpose: To evaluate the surgical outcomes of two inferior oblique muscle weakening procedures in the management of unilateral superior oblique muscle palsy (SOP). Methods: Files of all SO palsy patients with 11-20 PD hypertropia (HT) who were treated either by inferior oblique myectomy (IOM) or inferior oblique anterior transposition (IOAT) were retrospectively reviewed. Demographic characteristics such as sex, age, etiology, simultaneous horizontal deviation, and diplopia were noted. The two techniques were compared through HT correction (in the primary position, contralateral gaze, and ipsilateral tilt) and head tilt correction. Subgroup analysis was performed in the moderate group (11-15 PD HT) and large group (16-20 PD HT). Results: This study included 69 patients in the IOM group and 55 patients in the IOAT group. The demographic characteristics of both groups were similar. Although both procedures successfully corrected the abnormal head tilt, IOAT achieved significantly more HT correction compared to IOM (p-value: 0.003). While both techniques were equally effective in the moderate group, IOAT resulted in more primary position HT correction (16.4 vs. 12.9 PD) in the large group. However, anti-elevation syndrome occurred in 5.4% of patients treated by IOAT. Conclusions: IOAT achieved more HT correction compared to IOM, particularly in patients with large preoperative HT. The lower risk of under-correction following IOAT must be weighed against its potential risk of anti-elevation syndrome.