前庭性眼振と視運動性眼振の急速相の差異について

Abstract

Differences between vestibular nystagmus and optokinetic nystagmus in fast phase elicited by the same stimulating velocity in a sinusoidal manner were determined. A rotatory chair was surrounded by a cylinder screen to project stripes for optokinetic stimulation. The test subject was instructed to look at stripes rotating sinusoidally for the pendular optokinetic nystagmus (POKN) testing without rotation of the chair. Then the test subject was sinusoidally rotated with eyes closed for the vestibulo ocular reflex (VOR) testing, and finally requested to open eyes with the chair rotating in the illuminated screen for the visual and vestibulo ocular reflex (VVOR) testing.The relationship between fast phase amplitude and velocity was approximated by the exponential equation, i. e. Velocity (i)= V (1-exp (-Amplitude (i)/A). The V and A which were calculated by the least square method from fast phase amplitude and velocity of every nystagmus in each testing condition were parameters to evaluate the amplitude and velocity of each response.Previously, the gain of slow phase velocity of normal subjects was in the order VVOR>POKN>VOR. However, the V and A values of normal subjects were in the order POKN>VVOR>VOR (P<0.005). Moreover, the coefficient of correlation between the gain of slow phase velocity and the V-value in VOR (0.49) was significantly more than that in POKN (0.20) and VVOR (0.19).In conclusion, although the fast phase of OKN in stripe stimulation is saccadic eye movement look at the next stripe closer to the center of visual field, that of vestibular nystagmus is reflex eye movement for recovery of the eye deviation by vestibulo ocular reflex.