the effect of head tilt angle in the roll plane on the virtual subjective visual vertical results in healthy adults

Background and aim: the subjective visual vertical (svv) is commonly considered as an indicator of the sense of orientation and attributed to the utricular function. the present study examined the impact of different head tilt angles on svv among the normal individuals. methods: svv was measured in 47 normal participants (30 males and 17 females; mean ± sd age: 22.14 ± 3.46) using a virtual goggle and forcedchoice paradigm and was applied twice in 0°, 15°, 30° and 45° to the left or to the right. in addition, difference in mean of svv in zero and nonzero positions was compared. results: there was a statistically significant difference between the mean svv results of 0° and 15° (p < 0.001). the comparison of mean svv results between 0° and 30°, and between 0° and 45° were not significant (p > 0.05). in addition, comparison of svv results between rightward and leftward tilt of 15° was statistically significant (p < 0.001). the latter comparison was not significant for 30° and 45° (p > 0.05). conclusion: our results showed that head tilt angle of 15° have a substantial impact on the virtual svv. these findings must be taken into account in the growing body of research that uses the svv paradigm in clinical populations.