Abstract #489, Date Tuesday, Jan 29 2002 1:00PM - 12:00PM Session M Vestibular
Postural Sway in a Virtual Environment in Patients With Unilateral Peripheral Vestibular Lesions
Susan L. Whitney, Patrick J. Sparto, Kathryn E. Brown, Mark Redfern, Joseph M. Furman
Vestibular compensation adjusts for abnormalities of the vestibulo-ocular reflex (VOR) and postural instability seen acutely following unilateral peripheral vestibular lesions (UPVL). The goal of this study was to assess the visual motion sensitivity of patients with chronic UPVL's. Seven patients who had undergone a vestibular nerve section at least 10 months prior to testing (3F/4M, ages 31-65) and seven gender and age-matched controls participated in the experiment. A visual stimulus of an infinitely long tunnel with checkered walls was displayed in the BNAVE, a virtual environment display facility. Subjects stood barefoot for 80 seconds while viewing sinusoidal movements of the virtual tunnel. Sixty seconds of movement were preceded and followed by 10 seconds of quiet standing. Scene movement occurred forward and back along the long axis of the tunnel at sinusoidal frequencies of 0.1 or 0.25 Hz. The field of view (FOV) conditions consisted of 1) full FOV, 2) central 30 degrees FOV, and 3) peripheral 30 degrees FOV. Head movement and center-of-pressure (COP) was measured using a magnetic tracking device and a force plate. Repeated measures ANOVA was used to test for the effects of subject group, movement frequency, and FOV condition. There was no difference in the amount of sway elicited in the patients versus controls. However, the amount of sway was significantly affected by the FOV: full FOV and peripheral FOV elicited sway that exceeded the sway elicited by central FOV conditions. This effect was seen for both patients and controls and did not depend on the frequency of scene movement. We conclude that FOV significantly influences visual motion-induced sway in normal subjects and in patients with chronic UPVL’s. Support provided by The Eye and Ear Foundation and NIH Grants DC05372, DC05205, and DC03417.