高齢者の迷路性眼球運動機能

伝達関数による検討

抄録

This study describes the characteristics of visual-vestibuloocular reflex (VVOR) and vestibuloocular reflex (VOR) in elderly subjects.
Head and eye movements in passive horizontal head oscillations were examined with an "FAT-1" apparatus (reported by Tokita, 1993). Transfer function was calculated with head movements as input and eye movements as output. The examination was performed under the following 2 conditions, A) visual fixation to an earth-fixed target in the light (test for VVOR), B) image fixation to an earth-fixed target in the dark (test for VOR).
From the data obtained in five healthy adults (twenties and thirties), the mean (M) and the standard deviation (SD) were calculated as the standards. The data obtained in twenty elderly subjects (65-91 years) were compared with the standards. The evaluation defined within M±1SD as "no change", within M±1SD-2SD as "tendency toward decrease" or "tendency toward increase", and beyond M±2SD as "decrease" or "increase."
Results
A) VVOR test
(1) The breakpoint frequencies of the gain showed "decrease" or "tendency toward decrease" in all subjects.
(2) The frequency ranges of 180°±10° were narrow in 14 subjects.
B) VOR test
(1) Patterns of gain curves were classified into 5 types.
Gains did not show "decrease" or "tendency toward decrease" and slopes of 0.1-1 Hz and slopes at 0dB did not show "increase" or "tendency toward increase" in 5 subjects. These were classified as N type.
Gains showed "decrease" or "tendency toward decrease" in low frequencies in 6 subjects. These were classified as L type.
Gains showed "decrease" or "tendency toward decrease" in high frequencies in 2 subjects. These were classified as H type.
Gains showed "decrease" or "tendency toward decrease" in low and high frequencies in 1 subjects. This was classified as LH type.
Gains did not show "decrease" or "tendency toward decrease" in low frequencies and slopes of 0.1-1 Hz or slopes at 0dB showed "increase" or "tendency toward increase" in 6 subjects. These were classified as I type. This type was considered to show disorders of integration.
(2)The frequency ranges of 180°±10° were narrow in 10 subjects.
Conclusion
In all elderly subjects, the visual-vestibuloocular function had decreased and the vestibuloocular function was classified into 5 types.