Assessment of vestibulo-ocular function without measuring eye movements

•A method to assess the vestibulo-ocular reflex without measuring eye movements is described.•This new method involves the nulling of perceived visual motion as the head moves.•This provides a functional measure that accounts for a range of sensorimotor mechanisms.•This technology enables simple and rapid assessments with minimal apparatus and time. The vestibulo-ocular reflex (VOR) maintains stable gaze during head motion. Deficiencies lead to apparent world motion due to incomplete stabilization of eyes in space. VOR measurement requires specialized apparatus, trained operators, and significant setup time. We present a system (VON: vestibulo-ocular nulling) for rapid vestibulo-ocular assessment without measuring eye movements per se. VON uses a head-mounted motion sensor, laptop computer with user input control, and laser target whose position is controlled by the computer. As the head moves, the target is made to move in the same manner with a gain set by the subject. When the subject sets the gain so the target appears stationary in space, it is stationary on the retinas. One can determine from this gain the extent to which the eyes move in space when the head moves, which is the amount by which the VOR is deficient. From this the gain of the compensatory eye movements is derived. VON was compared with conventional video-based VOR measures. Both methods track expected changes in gain over 20min of adaptation to minifying spectacles. VON measures are more consistent across subjects, and pre-adaptation values are closer to compensatory. VON is a rapid means to assess vestibulo-ocular performance. As a functional perceptual measure, it accounts for gaze-stabilizing contributions that are not apparent in the standard VOR, such as pursuit and perceptual tolerance. VON assesses functional VOR performance. Future implementations will make VOR assessment widely available to investigators and clinicians.