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 forced-choice paradigm and was applied twice in 0º, 15º, 30° and 45º to the left or to the right. In addition, difference in mean of SVV in zero and non-zero positions was compared. Results: There was a statistically significant difference between the mean SVV results of 0º and 15º (p ˂ 0.001). The comparison of mean SVV results between 0º and 30º, and between 0º and 45º were not significant (p > 0.05). In addition, comparison of SVV results between rightward and leftward tilt of 15º was statistically significant (p ˂ 0.001). The latter comparison was not significant for 30º and 45º (p > 0.05). Conclusion: Our results showed that head tilt angle of 15º 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