Context: A subgroup of individuals with vestibular dysfunction and visual motion hypersensitivity (VMH) become dizzy and imbalanced in response to movement of the visual environment. Objective: The purpose of this study was to investigate ocular fixational stability while bifixating on a small midline target with and without visual background movement. Binocular visual functions were also examined as possible confounding factors. Design: The study was a quasi-experimental three-group comparison design with a control group. Assignment to the experimental group was by symptoms of VMH as diagnosed by a physical therapist or neuro-otologist. Subjects: Twenty-four individuals with VMH, 20 with vestibular disorders without VMH, and 20 healthy subjects were tested. Outcome measures: Electrooculogram recordings (vertical an horizontal) were examined for refixation eye movements, and 4 binocular visual functions were assessed. The DHI for measuring level of dizziness were also used. Results: Subjects with VMH had significantly more refixation eye movements and higher levels of dizziness than found in the other two groups. There were abnormalities in binocular function in bothe the VMH group and vestibular dysfunction group compared to the control group. Conclusions: Individuals with VMH are unable to use bifixation to inhibit eye movements to background motion. Binocular vision dysfunctions may contribute to this problem.
