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. 2021 Aug 21;6(5):1116–1127. doi: 10.1002/lio2.632

TABLE 2.

Battery of ocular motor, reaction time and cognitive tests

Tests Metrics
1 Optokinetic (OKN) 20 deg/s: Participants see a stimulus consisting of a field of dots moving on the display first to the right, then to the left, with a velocity of 20 deg/s. Each test consists of a stimulus rotating for 10 seconds clockwise (CW) and then 10 seconds counterclockwise (CCW), with 3 seconds of rest between CW and CCW rotation.
  1. Average eye velocity CCW (deg/s) = eye velocity during the slow phase of nystagmus for stimuli moving in counterclockwise (CCW) direction
  2. Average eye velocity CW (deg/s) = eye velocity during the slow phase of nystagmus for stimuli moving in clockwise (CW) direction
  3. Gain = ratio between average eye slow phase velocity and stimulus for CW and CCW segments
  4. Gain Asymmetry (%) = represents the difference between gain calculated for CW and CCW segments
  5. *Area Under Velocity Fit +(30 deg) = proportional to fast beat velocity for CCW stimuli
  6. *Area Under Velocity Fit (30 deg) = proportional to fast beat velocity for CW stimuli
  7. Normalized OKN CW velocity gain (normalized at 20 deg/s)
  8. Normalized OKN CCW velocity gain (normalized at 20 deg/s)

*‐see details for calculation in the method section
Optokinetic (OKN) 60 deg/s – same as OKN 20 deg/s, but with the stimulus moving at 60 deg/s. Same as above
2 Sinusoidal harmonic acceleration (SHA) 0.02 Hz (also known as Chair rotation sinusoidal): subject is rotated back and forth sinusoidally in the dark at frequency of 0.02 Hz with a peak velocity of 60 deg/s.

  1. Gain = average of gain left and gain right, that is, vestibulo‐ocular reflex (VOR) gain, where gain (left or right) is the ratio of the peak slow phase eye velocity to the peak head velocity and is expressed as a percentage

  2. Asymmetry = represents the percentage difference between gain calculated for left and right gains

  3. *Phase = temporal relationship between peak eye and peak head velocity, expressed in degrees

    *see details for calculation in the method section
Sinusoidal Harmonic Acceleration (SHA) 0.64 Hz Same as above
3 Visual enhancement (VE): subject is rotated back and forth sinusoidally at frequency of 0.64 Hz with a peak velocity of 60 deg/s. A static optokinetic stimulus is presented during this rotation.
  1. Average gain
  2. Asymmetry
  3. Phase

All values that have similar meaning are calculated similar to those described in the SHA test
4

Visual suppression (VS): subject is rotated back and forth sinusoidally at frequency of 0.64 Hz with a peak velocity of 60 deg/s. Subject is directed to fixate on laser dot that moves with the chair.

This allows an individual to suppress the VOR. Suppression is poorer at higher frequencies of rotation.
  1. Average gain
  2. Asymmetry
  3. Phase

All values that have similar meaning are calculated similar to those described in the SHA test
5 Controlled rotational head impulse test (crHIT): subject is rotated briefly in pseudo‐random direction (6 CW and 6 CCW) for a total of 12 rotations. An acceleration of 1000 deg/s2 is included in this test. Participants are directed to fixate on earth‐fixed target during rotation. Each stimulus consists of 150 milliseconds acceleration using an “S” type profile (to minimize patient's discomfort), followed by 300‐400 milliseconds run at speed up to 180 deg/s and slow “S” type deceleration for 2–3 seconds. Between each stimulus the subject is at rest for 5–8 seconds.

  1. *Gain = Average VOR Gain

  2. *Asymmetry = Average VOR Gain Asymmetry (%)

    *see details for calculation in the method section
6 Subjective visual vertical (SVV): subject is presented with a non‐vertical line and by using the left and right buttons on the handheld control box (Dx 100) or the buttons located on the chair handle (NOTC), orients the line to the vertical (upright) position, and then presses the accept button on the control box (Dx 100), or verbally acknowledges the alignment (NOTC). A total of 6 trials were performed per subject, 3 with a positive and 3 with a negative angle preset, presented randomly. Mean error (deg) = difference between subject's orientation angle and true vertical. Data are presented as a mean of errors of all measurements.
7 Subjective visual horizontal (SVH): subject is presented with a non‐horizontal line and by using the left and right buttons on the handheld control box (Dx 100) or the buttons located on the chair handle (NOTC), orients the line to the horizontal position, and then presses the accept button on the control box (Dx 100), or verbally acknowledges the alignment (NOTC). A total of 6 trials were performed per subject, 3 with a positive and 3 with a negative angle preset, presented randomly. Mean error (deg) = difference between subject's orientation angle and true horizontal. Data are presented as a mean of errors of all measurements.

Note: Description of each test and metrics measured for each test.