Bilateral vestibular failure impairs visual motion perception even with the head still.

Visual motion perception of a single object, moving with a constant angular velocity of 40 min of arc/s in four orthogonal directions, was measured in eight patients with chronic bilateral vestibular failure (BVF) with the head stationary. Perception of object motion was more severely impaired for horizontal than for vertical directions and the impairment was more pronounced in the dominant eye than the nondominant eye. Impaired motion perception in patients with BVF is best explained by a central visual mechanism that suppresses oscillopsia due to the involuntary retinal slip caused by the defective vestibulo-ocular reflex (VOR). This mechanism cannot be switched off with the head stationary (inactive VOR) and thus causes a measurable deficit of motion perception.