CVT Gaze Stabilization & Oculomotor Assessment 2 — Questions and Answers
Question 1: Dynamic visual acuity (DVA) testing measures:
- Visual acuity at rest with best optical correction
- The change in visual acuity between static conditions and during active head movement (Correct answer)
- Visual field defects caused by vestibular disorders
- Contrast sensitivity during optokinetic stimulation
Correct answer: The change in visual acuity between static conditions and during active head movement
DVA measures the difference in visual acuity between static conditions and during active head movement, directly reflecting the functional adequacy of VOR-mediated gaze stabilization.
Question 2: Normal VOR gain during sinusoidal rotational chair testing is approximately:
- 0.3–0.5
- 0.6–0.7
- 0.8–1.0 (Correct answer)
- 1.2–1.5
Correct answer: 0.8–1.0
Normal VOR gain is approximately 0.8–1.0, indicating that eye velocity closely matches head velocity and gaze is maintained on the target.
Question 3: Covert saccades detected on vHIT are best described as:
- Saccades that occur during the head impulse before the head stops moving (Correct answer)
- Saccades that occur after the head has completed its movement
- Saccades directed away from the visual target
- Saccades observed only in central vestibular disorders
Correct answer: Saccades that occur during the head impulse before the head stops moving
Covert saccades occur during the head impulse itself while the head is still moving; they represent an early compensatory strategy invisible to the naked eye and detectable only by video.
Question 4: The smooth pursuit eye movement system is best tested at which frequency range?
- 0.5–2 Hz (Correct answer)
- 5–10 Hz
- 0.1–0.4 Hz
- 10–20 Hz
Correct answer: 0.5–2 Hz
Smooth pursuit is most effectively assessed at 0.5–2 Hz; higher frequencies exceed the bandwidth of the smooth pursuit system and require saccadic catch-up movements.
Question 5: Which oculomotor finding most strongly suggests a central vestibular lesion rather than a peripheral one?
- Unidirectional horizontal nystagmus suppressed by fixation
- Direction-changing nystagmus that reverses with the direction of gaze (Correct answer)
- Spontaneous nystagmus that decreases with visual fixation
- Reduced VOR gain ipsilateral to hearing loss
Correct answer: Direction-changing nystagmus that reverses with the direction of gaze
Direction-changing gaze-evoked nystagmus — beating toward the direction of gaze — is a hallmark of central vestibular pathology, typically involving cerebellar dysfunction.
Question 6: The optokinetic nystagmus (OKN) response is generated by which combination of eye movement systems?
- Saccadic system only
- Smooth pursuit system only
- Both smooth pursuit and saccadic systems working together (Correct answer)
- VOR system exclusively
Correct answer: Both smooth pursuit and saccadic systems working together
OKN involves the smooth pursuit system to track the moving visual field (slow phase) and the saccadic system to reset the eyes (fast phase), creating the characteristic saw-tooth nystagmus pattern.
Question 7: During fixation suppression of the VOR (VVOR), failure to suppress the VOR suggests:
- Peripheral vestibular hypofunction on the tested side
- Normal central vestibular processing
- Cerebellar or central nervous system pathology (Correct answer)
- Bilateral otolith organ dysfunction
Correct answer: Cerebellar or central nervous system pathology
The cerebellum mediates VOR suppression during fixation; failure to suppress the VOR during VVOR testing is a sign of cerebellar or CNS pathology.
CVT Gaze Stabilization & Oculomotor Assessment 2
Dynamic visual acuity (DVA) testing measures: