Assessing Otolith-Ocular Function With Video-Ocular Counter-Roll: Optimal Tilt Angles and Impact of Visual Inputs

Objectives: – When the head is tilted laterally against the pull of gravity, the vestibulo-ocular response is an ocular counter-roll primarily driven by utricular input. Building on this physiological principle, the video-ocular counter-roll (vOCR) test is a new method for clinical evaluation of otolith-ocular function. In this study, we look for the optimal angle for the vOCR test and explore if there is any difference in vOCR responses in different lighting environments. Design: – The vOCR test involves a passive tilt of the head and torso en bloc while the subject fixates on a small visual target ahead. We measured vOCR at tilt angles of 30°, 60°, and 90° in healthy subjects (age: 33.5 ± 10.04 [mean ± SD]) to determine which angle yields a robust response. We also compared vOCR measurements under light and dark conditions. Results: – Our results show that vOCR gains were greater at a 30° tilt compared with both 60° and 90° tilts, regardless of the lighting condition. The mean vOCR values ± SD were 5.91° ± 1.42° in the light and 6.22° ± 1.45° in the dark at 30°, 7.13° ± 1.87° in the light and 7.74° ± 2.28° in the dark at 60°; and 7.39° ± 1.7° in the light and 8.47° ± 2.23° in the dark at 90°. The vOCR measurements in the light and dark conditions showed a significant correlation (R² = 0.47; p < 0.00001). Conclusions: – These findings show that measuring vOCR with a 30° tilt under normal lighting conditions is both feasible and provides a reliable assessment of otolith-ocular function in clinical settings.