The impact examination of the head tilt size on the subjective visual vertical (SVV) among the normal individuals with ages ranged from 18 to 35 years

Abstract Objective: The subjective visual vertical (SVV) is commonly considered as an indicator of the sense of orientation. The present study aims to assess the impact of head tilt size (by 0°, 15°, 30° and 45° to the left or to the right) on SVV among the normal individuals with ages ranged from 18 to 35 years. Methods: Four healthy participants (30 males and 17 females; mean ± SD age: 22.14 ± 3.463) were included in current study. SVV was measured using a forced-choice paradigm and was applied (in different head tilt positions) for every individual twice the time. In addition, difference in averages of SVV in zero and non-zero positions was compared. A p-value of .05 or below was considered to be statistically significant. Results: There is statistically significant different between head tilt size by 15° and without head tilt for averages of SVV responses (p ˂ .001). Averages of SVV responses were not different between the head tilt size by 30° and 45° and without head tilt (p > .05). In addition, there is statistically significant different between head tilt size by 15° to the left and to the right (p ˂ .001). This rate was not statistically significant between 30° to the left and to the right and 40° to the left and to the right (p > .05). Conclusion: Our results showed that head tilt size by 15° have an impact on the evaluation of the SVV. These findings must be taken into account in the growing body of research that uses the SVV paradigm in disease settings.