Evaluating the Number of Trials for Stable Virtual Reality-Based Subjective Visual Vertical Measurement in Healthy...

Virtual reality-based subjective visual vertical (VR-SVV) has attracted attention as a potential solution to equipment-related limitations of conventional SVV testing. This study investigated the test-retest reliability and adequate trial number for stable assessment of vertical perception using VR-SVV in healthy adults. Participants performed 10 trials in a VR-SVV test and repeated the assessment after one week. SVV orientation and SVV variability were calculated. Test-retest reliability was evaluated using the intraclass correlation coefficient (ICC [1,2]), standard error of measurement (SEM), and minimal detectable change at the 95% confidence level (MDC₉₅). The minimum number of trials required for stable assessment was examined by comparing results from fewer trials with those obtained from all 10 trials. SVV orientation and variability were -0.14° and 0.79°, respectively. ICC, SEM, and MDC₉₅ were 0.62, 0.64°, and 1.76°, respectively. No adverse events occurred. SVV metrics derived from 6-9 trials differed by less than 10% from those obtained from 10 trials. VR-SVV is feasible and demonstrates moderate test-retest reliability. Six trials may be adequate for practical assessment of vertical perception.