Chia‑Han Wanga, Ariel A. Winnickb,c, Yu‑Hung Kod, Zheyu Wange, Tzu‑Pu Changf,g*
aDepartment of Chinese Medicine, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, bSoroka University Hospital and Faculty of Health Sciences, Ben‑Gurion University of the Negev, Beer‑Sheva, Israel, cSchool of Optometry, University of California, Berkeley, Berkeley, CA, USA, dDepartment of Research, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, eDivision of Biostatistics and Bioinformatics, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA, fDepartment of Neurology, Neuro‑Medical Scientific Center, Taichung Tzu
Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, gDepartment of Neurology, School of Medicine, Tzu Chi University, Hualien, Taiwan
Open Access funded by Buddhist Compassion Relief Tzu Chi Foundation
Abstract
Objective: The objective is to investigate the test‑retest reliability of subjective visual vertical (SVV) in the upright position and with lateral head tilts through a computerized SVV measuring system using virtual reality (VR) goggles. Materials and Methods: Thirty healthy controls underwent SVV test in upright position, with the head tilted to the right 30°, and with the head tilted to the left 30°. Subjects wore SVV VR goggles, which contained a gyroscope for monitoring the angle of head tilt. Each subject completed 10 adjustments in each head position. The mean value of SVV deviations and SVV imprecision (the intra‑individual variability of SVV deviations from the 10 adjustments) were recorded and compared across different head positions. The participants then repeated the same SVV protocol at least 1 week later. The test‑retest reliability of SVV deviation and SVV imprecision were analyzed. Results: The SVV deviation (mean ± standard deviation) was 0.22° ± 1.56° in upright position, −9.64° ± 5.91° in right head tilt, and 7.20° ± 6.36° in left head tilt. The test‑retest reliability of SVV deviation was excellent in upright position (intra‑class correlation coefficient [ICC] = 0.77, P < 0.001), right head tilt (ICC = 0.83, P < 0.001) and left head tilt (ICC = 0.84, P < 0.001). The SVV values from the 10 adjustments made during right and left head tilts were less precise than when measured at upright (P < 0.001). The test‑retest reliability of SVV imprecision was poor at upright (ICC = 0.21, P = 0.26) but fair‑to‑good in right head tilt (ICC = 0.72, P < 0.001) and left head tilt (ICC = 0.44, P = 0.04). Conclusion: The test‑retest reliability of SVV deviation during lateral head tilts via VR goggles is excellent, which supports further research into the diagnostic value of head‑tilt SVV in various vestibular disorders. In addition, the degree of SVV imprecision during head tilt has fair‑to‑good test‑retest reliability, which suggests SVV imprecision may have clinical applicability.
Keywords: Reliability, Subjective visual vertical, Vestibular perception, Vestibular test
