Purpose:
This study investigates the effect of gaze shifting prism ongaze holding abnormalities secondary to vestibular injury. Shiftinggaze away from a direction of high SPV (Slow Phase Velocity)nystagmus reduces symptoms of oscillopsia and dizziness andpromotes successful vestibular rehabilitation in refractorysubjects.
Methods:
Six vestibular injury subjects with oscillopsia, dizziness,and discomfort during vestibular rehabilitation, were testedwith a Subjective Disability Scale (SDS) and infra-red videooculography using the ICS Charter System VNG. Gaze was heldsteady for 30 seconds on a red LED in center and at 30ºright, left, up, and down on a light bar 4 feet away. Eyes wereopen then testing was repeated with vision denied behind a closedgoggle. SPV was calculated from the gaze holding graphs of binocularvertical and horizontal eye movements that were obtained ineach position (figure #1). After prism adaptation for shiftinggaze away from a position of high SPV, graphs were repeated(figure #2) and symptoms were reassessed. Subjects resumed eightweeks of vestibular rehabilitation with prism.
Results:
A higher mean SPV was measured in symptomatic positions of gaze(11º) than in the opposite direction (4º). HigherSPV correlates to oscillopsia and dizziness symptoms. Prismreduces SPV (3º) and symptoms. Prism along with vestibularrehabilitation improved the SDS (83%).
Conclusions:
Gaze shifting prism reduces gaze holding nystagmus and relatedsymptoms of oscillopsia and dizziness. Prism provides the reliefnecessary to endure and achieve success in vestibular rehabilitation.
Keywords: eye movements • vestibulo-ocular reflex • vision and action