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Introduction: Current clinical practice considers the vestibulo-ocular reflex (VOR) gain as registered by the video head impulse test (vHIT) as the primary measure for semicircular canal function, while the role of the re-fixation saccades (RSs) is still under evaluation. The goal of the study was to appraise the added benefit of RS towards the improvement of vHIT diagnostic accuracy in cases of suspected left horizontal semicircular canal dysfunction. Methods: The vHIT recordings of 40 patients with left-sided horizontal VOR gains <0.8 were retrospectively evaluated for the presence of RS. The study groups included 20 patients with a final diagnosis of left horizontal semicircular canal dysfunction and 20 patients for whom vestibular dysfunction was ruled out. Results: Gain values >0.72 were found in all patients with no vestibular disease and in 4 (20%) patients having vestibulopathy. Significantly higher average left-sided RS velocity and frequency were found among the vestibular patients. VOR gain <0.72 was found to be highly specific for the diagnosis of vestibular dysfunction. However, for gain values in the range of 0.72–0.79, the presence of RS with frequency >80% largely improved vHIT diagnostic accuracy. Conclusions: Although VOR gain <0.8 is considered to reflect dysfunction, a significant false-positive rate for left-sided horizontal vHIT was found for gains in the range of 0.72–0.79. The presence of RS with frequency >80% could improve vHIT diagnostic ability in these patients. [ABSTRACT FROM AUTHOR]

Gaze stabilization during head movements is provided by the vestibulo-ocular reflex (VOR). Clinical assessment of this reflex is performed using the video Head Impulse Test (vHIT). To date, the influence of different fixation distances on VOR gain using the vHIT has not been explored. We assessed the effect of target proximity on the horizontal VOR using the vHIT. Firstly, we assessed the VOR gain in 18 healthy subjects with 5 viewing target distances (150, 40, 30, 20, and 10 cm). The gain increased significantly as the viewing target distance decreased. A second experiment on 10 subjects was performed in darkness whilst the subjects were imagining targets at different distances. There were significant inverse relationships between gain and distance for both the real and the imaginary targets. There was a statistically significant difference between light and dark gains for the 20- and 40-cm distances, but not for the 150-cm distance. Theoretical VOR gains for different target distances were calculated and compared with those found in light and darkness. The increase in gain observed for near targets was lower than predicted by geometrical calculations, implying a physiological ceiling effect on the VOR. The VOR gain in the dark, as assessed with the vHIT, demonstrates an enhancement associated with a reduced target distance. [ABSTRACT FROM AUTHOR]