Effects of inferior oblique muscle-weakening surgery on the Bielschowsky head-tilt phenomenon in patients with superior oblique palsy habitually fixating with the paretic eye

Abstract

To evaluate the usefulness of inferior oblique (IO) weakening surgery on a paretic eye for correcting vertical deviation in three positions of gaze by comparing the surgical results in 2 types of unilateral superior oblique (SO) palsy. The patients were divided into 2 groups: 27 patients fixated with the paretic eye and 61 patients fixated with the non-paretic eye (control). The former had hypotropia and the latter hypertropia. All patients underwent IO recession of the paretic eye. We compared the corrective effects, percentage changes in the decrease of vertical deviation of the primary position (PP), vertical deviation on ipsilateral head tilt, i.e., the Bielschowsky head-tilt phenomenon (BHP), and differences in vertical deviation between ipsilateral and contralateral head tilt (BHTD) relative to the preoperative values between the 2 groups. Mean percentage decrease in vertical deviation of the BHP and BHTD in the control group was larger at 3, 6, and 12months, but no significant difference was observed between the 2 groups except for the BHP at 12months (52% for case vs. 70% for control, p=0.04). IO weakening in the paretic eye was effective irrespective of the preferred eye for fixation on PP and head-tilt position.