Understanding VOR Functional Testing: Dynamic Visual Acuity & the Gaze Stabilization Test
- Ana Souto
- Jan 20
- 3 min read
Dynamic Visual Acuity and Gaze Stabilization Test
The vestibulo‑ocular reflex (VOR) helps keep vision stable when the head moves by generating eye movements in the opposite direction, at the same velocity and at the same amount as the head movement. This allows images to remain clear on the retina during everyday activities where there is movement, such as walking, bending, or turning the head.
When VOR performance is reduced, patients often experience blurred vision, oscillopsia, dizziness and imbalance.
To understand how changes in the VOR gain affect functional visual performance, clinicians frequently rely on two assessments:
Dynamic Visual Acuity (DVA)
Gaze Stabilization Test (GST)
Rather than measuring the physiological response of the vestibular system, the Dynamic Visual Acuity Test and the Gaze Stabilization Test assess the final visual performance during head movement, whether the movement is active or passively induced, providing a behavioural measure of VOR function and monitoring dynamic compensation over time.
This makes them valuable for evaluating:
The impact of VOR dysfunction.
The patient’s level of dynamic compensation.
The patient´s response during rehabilitation.
Both tests can be performed using a head‑mounted IMU, ensuring accurate and consistent measurement of head velocity and direction. The PhysioSensing Otoneuro System includes both assessments.
Dynamic Visual Acuity Test (DVA)
DVA measures how much visual acuity drops when the head is moving, compared with visual acuity at rest. Because stable vision during movement depends on precise VOR‑driven eye movements, any reduction in VOR performance results in decreased dynamic acuity. For this reason, DVA is considered a strong functional indicator of both vestibular impairment and dynamic compensation.
How the DVA Test Is Performed
Static visual acuity is measured first.
The patient performs head movement in the chosen plane of movement.
Head movement can be active or passive.
A head‑mounted IMU ensures that the correct speed is reached and maintained.
The patient identifies the smallest optotype they can read during movement.
Expected DVA Results
Healthy adults
Small decrease in acuity during movement.
Typically 0.2–0.3 logMAR loss.
Symmetrical performance in both directions.
Vestibular hypofunction
Larger loss of dynamic acuity.
Marked asymmetry (worse toward the impaired side).
Strong correlation between reduced VOR gain and poorer DVA performance.
DVA in rehabilitation
As patients progress through vestibular rehabilitation, dynamic compensation improves, resulting in better DVA performance, even when physiological VOR gain does not fully recover. This improvement is a well‑known sign of vestibular compensation.
Gaze Stabilization Test (GST)
GST determines the highest head velocity at which a patient can still correctly identify an optotype. It establishes a functional speed limit for gaze stability, meaning the fastest velocity the patient can tolerate while maintaining clear vision
How the GST Test Is Performed
Static visual acuity is measured first.
The patient performs head movement in the chosen plane of movement.
The IMU measures head velocity continuously.
An optotype appears only when the preset velocity threshold is achieved.
If the patient correctly identifies the orientation, the velocity threshold increases.
Expected GST Results
Healthy adults
Average tolerable peak velocity: around 147°/s.
Symmetrical performance between directions.
Unilateral vestibular loss
Reduced tolerable velocity toward the impaired side.
Lower‑than‑normal performance even toward the intact side.
GST in rehabilitation
GST thresholds typically increase as patients recover, making it an excellent tool for:
Tracking functional improvement.
Monitoring compensation.
Identifying direction‑specific deficits.
Go check the Otoneuro System Product Sheet
Ana Souto
Meet Ana, a physiotherapist with a master's degree in human physiology and certified by the American Institute of Balance.
Ana currently serves as the clinical specialist at PhysioSensing, a cutting-edge Balance Assessment and training device. Her approach is firmly rooted in the latest scientific findings, ensuring that PhysioSensing users receive the most effective and up-to-date care. In addition to her role in designing tailored programs, Ana plays a pivotal role in guiding new clients through the learning process of using PhysioSensing. She also provides advanced training and support to existing customers seeking to further deepen their clinical practice knowledge and stay on top of the latest scientific advancements.