Eye Movements Are Correctly Timed During Walking Despite Bilateral Vestibular Hypofunction

Area of Science:

• Neuroscience
• Ophthalmology
• Rehabilitation Science

Background:

• Bilateral vestibular hypofunction (BVH) often causes oscillopsia during locomotion.
• Gaze stability during walking relies on eye velocity and precise movement timing.
• The specific deficits in eye velocity (VOR gain) or timing (phase) in BVH during walking remain unclear.

Purpose of the Study:

• To investigate whether eye velocity (VOR gain), timing (phase), or both are impaired in individuals with BVH during walking.
• To identify the primary mechanism of gaze instability in BVH to guide rehabilitation strategies.

Main Methods:

• Measured gaze stability in eight individuals with severe BVH and eight healthy controls during treadmill walking.
• Calculated frequency response functions (FRF) from pitch eye and head velocity.
• Used ANOVA and Pearson correlation to analyze group differences and relationships with oscillopsia scores (oVAS).

Main Results:

• Individuals with BVH showed significantly lower VOR gains than controls at frequencies above 0.5 Hz.
• The phase of eye movements in BVH was compensatory for frequencies below 3 Hz.
• Higher oscillopsia scores correlated with reduced VOR gain.

Conclusions:

• Individuals with BVH exhibit intact timing of vertical eye movements during walking but reduced eye velocity (VOR gain).
• Rehabilitation should focus on enhancing VOR gain during locomotion to potentially reduce oscillopsia and improve quality of life.