Abstract
Purpose :
Visual vertigo, or Visual Motion Hypersensitivity (VMH), is when visual motion alone cause severe dizziness. Measuring the eye movement response to opto-kinetic cyclo-rotational motion could hold clinical utility. A head tilt is known to yield ocular torsion (OT) and ocular vertical skewing (OVS). Cyclo-rotational visual stimuli can also result in OT, but the skewing response has not been thoroughly investigated. The aim was to investigate the impact of vestibular and visual cyclo-rotational motion on the OT and OVS response in healthy subjects.
Methods :
16 healthy subjects were exposed to i) vestibular (VES), ii) visual (VIS), and iii) visuo-vestibular (VIS-VES) balance provoking stimulation in a randomized order. VES were carried out through whole-body tilting using a mechanical sled in complete darkness, VIS through opto kinetic stimuli of two magnitudes (low and high) and, VIS-VES while the subject viewed a static visual scene during body tilt. All stimulation occurred at 33°s-2 during one second. Eye movements were recorded using the Chronos Eye Tracker. OT= (right + left eye/2); OVS=left-right eye.
Results :
Compensatory OT combined with OVS were seen in all test conditions. VES stimulation caused significantly faster OT and OVS velocities than VIS. The contributions of VIS and VES to the OT response were calculated to 10-25% and 75-90% respectively. VIS levels (ii, iii) had no effect on OT and OVS velocities but the high VIS level increased the OT-OVS ratio regardless of vestibular activity.
Conclusions :
Our findings demonstrate similar eye movement responses to head tilt and visual opto-kinetic motion. The proportional contribution of visual- and vestibular input to EM balance response yields an estimation, in absolute values, of relative sensory hierarchy in postural control. The OT-OVS ratio may be a potential objective measurement of perceived intensity of visual information and could possibly be useful for distinguishing VMH patients.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.