Vestibulo-Ocular Reflex according to the Change of Angular Acceleration in Sinusoidal Harmonic Acceleration Test

Chi, Jang Hoon; Lee, Won Sang; Chung, Myung Hyun; Chung, Woon Kyo; Lee, Jung Jun; Lee, Hae Song

Abstract

We investigated the vestibulo-ocular reflex which is followed by the change of angular acceleration in sinusoidal harmonic acceleration test. 20 normal volunteers with no evidence of previous otoneurologic disease were tested. The maximal slow phase eye velocity, gain and asymmetry were obtained in five different amplitudes of rotation, 30degrees, 60degrees, 90degrees, 120degrees and 150degrees with properly fixed conditions such as darkness and the frequency of rotation fixed at 0.05Hz. During each test, we asked the examinees to be alert and keep the eyes open. At least 5 minute interval was given between the tests and recalibrations were done before each test. The results of this test were as follows. 1) The maximal slow phase eye velocities were gradually increased according to the increment of the amplitudes of rotation with the statistical significances(p<0.05). 2) The gains were gradually decreased according to the increment of the amplitudes of rotation between the range of 30degrees and 90degrees with the statistical significances(p<0.05). 3) The asymmetries of each amplitude were the highest(13.6%) at 30degrees and the lowest(6.9%) at 120degrees, but there were no statistical significances(p>0.05). Therefore, from the above results, sinusoidal harmonic acceleration test with the frequency fixed at 0.05Hz, gain is higher when the amplitude of rotation is smaller and the pattern of the nystagmus is more evident when the amplitude of rotation is bigger. But The authors conclude that in order to get the results which are statistically significant, the amplitude of rotation should be lower than 90degrees.