Analysis of Eye Movements Using 3-Dimensional Video-oculography in Response to Galvanic Vestibular Stimulation
BACKGROUND: Quantitative assessment of vestibular nerve activity has been difficult with conventional electrophysiological techniques. This study aimed to develop a novel method combining galvanic vestibular stimulation (GVS) with 3-dimensional video-oculography (3D-VOG) to evaluate vestibular function noninvasively. METHODS: Eye movements were recorded from healthy individuals using a high-resolution infrared VOG system (yVOG, Yamaguchi University). Bipolar GVS was applied bilaterally over the mastoid processes with various current intensities (0.5-2.0 mA) and polarities. Horizontal, vertical, and torsional eye-movement components were extracted and analyzed in relation to stimulus parameters. RESULTS: Torsional nystagmus amplitude and slow-phase velocity increased proportionally with stimulus intensity and reversed with polarity. Healthy participants exhibited symmetric responses. The induced eye-movement responses showed reproducible polarity- and intensity-dependent characteristics. CONCLUSION: This study demonstrates that GVS-VOG provides a direct, reproducible, and noninvasive means of evaluating vestibular nerve function through eye movement analysis. The method may complement existing vestibular function tests in future clinical applications. Galvanic vestibular stimulation-video-oculography also offers utility in both research and clinical settings by linking physiological mechanisms with observable oculomotor responses. This approach holds promise as a diagnostic tool for vestibular disorders, especially when conventional tests yield inconclusive results.