A comparison of the results of vertical position determination obtained using varying methods for the subjective visual vertical tests

This study is aimed at exploring how the subjective visual vertical (SVV) might vary depending on the method used to determine the vertical positions. Original equipment devised by the author was used in this study (hereafter, SVV investigation equipment). Study participants spun a wheel in order to determine the vertical position of an axis presented to them as an illuminated pillar in a dark room. Participants were asked to perform the task six times during the study. The results reflect their averages, with a + indicating the results that tilted towards the right. In 20 healthy participants, the results of the SVV test obtained with the subjects using their dominant hands to adjust the angle were compared with those obtained with the subjects using their non-dominant hands. In 23 healthy participants, the results of SVV test obtained with the subjects using their hands to adjust the angle were compared with those obtained with having the subjects answer yes/no to the presented angle (12 different patterns of tilted markers from 0 to ±5 degrees). In another 20 healthy participants, the results of the SVV test obtained with the subjects performing the test with both eyes open were compared with those obtained with the subjects performing the test using either eye. All the results obtained by the different methods were correlated with each other. There was also no difference in the actual measured angle between the test methods except for that between the tests conducted with the patient using the dominant and non-dominant hands. Our present study indicates that, the characteristics of SVV deviation can be estimated correctly even if the measurement method varies slightly, although it is better not to change the method when performing quantitative or temporal evaluation.