Tehran University of Medical Sciences Auditory and Vestibular Research 2423-480X 25 1 2016 05 16 39 48 EN Narges Naderi Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran Fahimeh Hajiabolhassan Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran Saeed Farahani Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran Nasrin Yazdani Department of Ear, Nose and Throat, Amiralam Hospital, Tehran University of Medical Sciences, Tehran, Iran Shohreh Jalaie Biostatistics, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran 2016 03 12 2016 04 12 Background and Aim: The video head-impulse test (vHIT) measures the vestibulo-ocular reflex (VOR) driven by each semicircular canal, follo­wing high-acceleration head rotations. The main measurable response is the ratio of eye mov­ement velocity to the angular head velocity, which reflects canal function. Although norma­tive data is available for VOR gain, most studies only report horizontal VOR characteristics, ignoring variations in vertical plane VOR gains. The purpose of this study was to establish nor­mative data for future comparisons of vesti­bulopathy patients. Methods: Vestibulo-ocular reflex gain and refi­xation saccades were assessed across 50 healthy individuals between the ages of 20 and 64, without any previous or current vestibular dis­orders, by applying and measuring horizontal and vertical head impulses. Results: The mean VOR velocity gain was 0.96 (SD=0.11) and 0.93 (SD=0.17) for the hori­zontal and vertical canals, respectively. The variation of the gain in right anterior/left pos­terior and left anterior/right posterior move­ments appeared to be wider than in the laterals, but the results were not influenced by direction (p>0.05). Refixation saccades occurred in 7.2 percent of all impulse trials, with a majority occurring covertly in lateral canals. Unlike saccades (more often observed in subjects older than 50), the VOR velocity gain varied independently of age. Conclusion: The findings suggest these gain values can be used to determine VOR deficits in patients. vHIT values are affected by diff­erent factors, especially in the vertical plane, so further study is needed to confirm normal ranges of vertical vHIT values. https://avr.tums.ac.ir/index.php/avr/article/view/97 https://avr.tums.ac.ir/index.php/avr/article/download/97/41