Evaluation of the peripheral vestibular system with video head impulse test (vHIT) and vestibular evoked myogenic potentials (VEMP) in individuals withvision loss.

In this study, it was aimed to compare the balance system of individuals with vision loss with the healthy control group by using the video head impulse test (vHIT), cervical vestibular evoked myogenic potentials (sVEMP) and ocular vestibular evoked myogenic potentials (oVEMP) tests. The study included 23 individuals diagnosed with bilateral low vision, 20 individuals diagnosed with bilateral blindness and 50 healthy individuals. vHIT, cVEMP and oVEMP tests were applied to all participants to evaluate the vestibular system. In addition to the standard vHIT, two-condition vHIT (in the dark and in daylight without a target) was performed on the control group to evaluate the effect of visual input. In vHIT responses, a significant difference in VOR gains was detected in the comparison between bilaterally low vision, bilateral blind and control groups in all SSK (p <0,001). When the vHIT responses in the three conditional groups of the control group (untargeted daylight, darkness and standard) were examined, a significant difference in VOR gains was detected in the comparison of all 3 groups in the entire SSK (p <0,001). When oVEMP responses of the study and control groups were compared; No statistically significant difference was detected between the bilateral low vision group and the control group (p>0,05). No oVEMP response was obtained in the bilaterally blind group. When the sVEMP responses of bilateral low vision, bilateral blind and control groups were compared; N23 latency value obtained from the right ear (p=0,016; p <0,05), N1P1 latency value obtained from the right ear (p=0,009; p <0,05) and N1P1 amplitude value obtained from the right ear (p=0,006; p A statistically significant difference was detected in the N1P1 amplitude value obtained from the left ear (p=0,001; p<0,05). The fact that the VOR gains obtained in untargeted daylight and dark conditions were statistically significantly lower than the control group suggests that visual input has a significant effect on the vestibular system. The statistically significant lower left anterior SSC VOR gains and right posterior SSC VOR gains of the bilateral low vision group compared to the control untargeted daylight group suggests that the presence of daylight even in the absence of a target may have an improving effect on VOR gain. Although we deprived healthy individuals of their vision, VOR was still significantly higher in the healthy group. This result may be attributed to the adaptation mechanism developed in healthy sighted individuals and the prolonged absence of visual input in blind individuals. In conclusion, in our study, the large effect of visual input on the vestibular system was explained by the statistically significant low VOR gains in low vision and blind individuals. In addition, the results of our three-stage (dark, untargeted light and standard) vHIT in healthy subjects also supported this hypothesis. Keywords: Vision loss, Low vision, Loss of balance, Dizziness, Cervical Vestibular Evoked Myogenic Potentials (cVEMP), Ocular Vestibular Evoked Myogenic Potentials (oVEMP), Video Head Impulse Test (vHIT).