Figure 3.

Relevant restrictive artifacts in our cohort. In this figure shows the relevant restrictive artifacts in our study: (A) slippage: the eye movement (top, black) precedes the head movement (top, gray). This leads to a calculated normal gain of 1.0 at 55–65 ms (see time course of the gain, bottom). A vestibulo-ocular reflex (VOR) deficit (note distinct re-fixation saccades, top) might not be detected because of the phase shift falsely increasing the gain value. (B) Calibration problems: due to a false calibration (bottom), the eye to head movement ratio is miscalculated resulting in an inappropriately low or high (as in this example) gain value without matching re-fixation saccades. Note the combination with the (not dominating) slippage artifact. For a correct example of calibration see Figure 1. (C) noise: oscillations of the eye movement trace (top, black), probably due to blinks, impaired pupil detection (e.g., narrow palpebral fissure, wearing mascara) or the examiner touching the goggles. A reliable gain calculation (bottom) is not possible. In this example, the former categories blinks, multiple VOR peaks and oscillations are present (Figure 2), summarized as “noise.”