Head and eye tracking for study of the VOR during natural head motion

Rotational testing of the vestibulo-ocular reflex (VOR) does not always correlate with patients´ symptoms. One possible reason is that conventional testing is performed at low frequencies and relatively low velocities that do not correspond to the high frequency perturbations encountered during locomotion. The authors present a combined head-eye tracking system suitable for use with free head movement during natural activities. The system was used to study the response to rapid passive head turns in normal subjects and patients with unilateral lesions. The patients have marked, persistent VOR deficits for rotation toward the side of lesion. The implications of these results on the organization of the normal VOR and the process of VOR compensation are discussed