Head impulses in complete bilateral vestibular loss: Catch-up saccades require visual input

Abstract

Patients with bilateral vestibular loss (BVL) experience oscillopsia during passive head movements,(1) e.g., walking or driving. Because their vestibulo-ocular reflex does not stabilize gaze with compensatory eye movements, patients with vestibular deficiency make refixation saccades to a target.(2) Some can trigger directionally accurate "covert" saccades during head movements and "overt" saccades afterward.(3) Covert saccades, with latencies as short as 70 milliseconds in unilateral vestibular loss,(3) reduce oscillopsia. To clarify the underlying mechanism, we investigated the sensory inputs required to evoke short-latency catch-up saccades.