What does vestibulo-ocular reflex testing assess, and which methods are commonly used?

• A. It assesses the vestibulo-ocular reflex; commonly using head impulse test and VOR gain
• B. It tests auditory nerve function
• C. It measures spinal reflexes
• D. It assesses visual acuity only

Answer: (A)

The vestibulo-ocular reflex (VOR) is the mechanism that keeps what you see stable when your head moves. Testing VOR asks how well this reflex stabilizes gaze, so you can detect vestibular problems.

A quick bedside method, the head impulse test, probes high-frequency VOR function. You look at a fixed target and the clinician makes small, rapid, unpredictable head movements. If the VOR is working, the eyes stay on the target; if not, you’ll see a quick catch-up saccade as the eyes refocus on the target.

For a quantitative readout, you measure the VOR gain—the ratio of eye velocity to head velocity. A normal gain is around 1.0, meaning the eyes move the same amount in the opposite direction as the head. Reduced gain indicates impaired VOR function. This gain is commonly obtained with video head impulse testing (vHIT), which records precise eye and head movements to give a numerical gain and identify corrective saccades.

Other tests like caloric testing or rotary chair can assess different frequencies of VOR and broader semicircular canal function, but the most widely used practical approach in many clinics is combining the head impulse test with VOR gain measurement.