Reduced Vestibulo-Ocular Reflex During Fast Head Rotation in Complete Darkness.

This article investigates the influence of visual input on the human horizontal vestibulo-ocular reflex (VOR) during high-acceleration head movements by comparing VOR performance under conditions of unrestricted vision and complete darkness. Using the video Head Impulse Test (vHIT) with the EyeSeeCam™ system, the study found that VOR gain—defined as the ratio of eye to head angular velocity—declined significantly more in complete darkness, particularly at 80 milliseconds after head movement onset when head velocities exceeded 150°/second. These results suggest that visual feedback modulates the high-velocity VOR, likely via cerebellar integration, and that reduced visual input in darkness may impair gaze stability and postural control, potentially increasing fall risk in populations with diminished sensorimotor function such as the elderly. The study emphasizes the importance of visual cues in maintaining VOR efficacy during rapid head turns and highlights the need for further research on sensory integration affecting balance in low-light conditions.