This study investigated the visual-vestibuloocular reflex in patients with vestibular disorders.
Head and eye movements during active horizontal head oscillations were recorded using apparatus for examining the vestibuloocular system. Transfer function of the oculomotor system was calculated using head movement as the input and eye movement as the output.
The examination was performed under the following 2 conditions: a) visual fixation on a fixed target in a lighted room (test for visual-vestibuloocular reflex, VVOR), and b) image fixation on a fixed target in the dark (test for vestibuloocular reflex, VOR).
The data obtained were compared with previously reported reference intervals.
Two patients with bilateral vestibular disorders and fifteen patients with unilateral vestibular disorders were examined.
Results
1) bilateral vestibular disorders:
On VVOR test, the breakpoint frequencies of the gain were lower than the reference intervals.
On VOR test, the gains at 0.1 Hz were lower than the reference intervals, the slopes of the gain enhancement were not linear.
2) unilateral vestibular disorders:
On VVOR test, the breakpoint frequencies of the gain were lower than the reference intervals in 75% of patients that were examined within two months after onset, 55% of patients that were examined two or more months after onset.
On VOR test, the gains at 0.1 Hz were lower than the reference intervals in 75% of patients examined within two months, and in 64% of those examined after two or more months, the slopes of the gain enhancement were not linear in 100% of patients examined within two months, and in 73% of those examined after two or more months.
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