Manual head rotation synchronised to a metronome is a feasible and valid method for assessing visually enhanced vestibulo-ocular reflexes and vestibulo-ocular reflex suppression

Introduction: The visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VOR-S) are critical in evaluating vestibular and cerebellar contributions to oculomotor control. This study aimed to investigate the feasibility and reliability of metronome-synchronised, manual head rotation video-oculography for evaluating VVOR and VOR-S in healthy participants. A secondary aim was to determine the effects of head rotation frequency and direction, and participant's age, on VVOR and VOR-S gain and saccades. Methods: Twenty-four healthy individuals aged 20-79 years underwent VVOR and VOR-S assessments performed over a range of frequencies from 0.25 to 1.25 Hz, using a portable ICS Impulse video-oculography device. Results: Good control over the frequency and velocity of head rotation was achieved using the metronome. Correlations with the intended frequency (Spearman's rho) ranged from 0.876 to 0.884. The VVOR gains were all close to 1.0 and were unaffected by age or the frequency of head rotation. Saccade rates for VVOR were low. The VOR-S gains and refixation saccades increased with increasing frequency and there was a small but significant effect of age. Slightly higher gains were recorded for head turns to the right for both the VVOR and VOR-S. Discussion: The findings confirm that use of a metronome can effectively control the frequency and to an extent, the velocity of head rotation, offering a cost-effective alternative to traditional rotational chair testing of the VVOR and VOR-S. The results provide a basis for future research and clinical application as a reference for identifying cerebellar and combined cerebellar and vestibular dysfunction.