Collection of Digital Parameters From Parts of the Neurological Examination Using an Eye Tracker

The vestibulo-ocular reflex (VOR) is measured using the eye-tracker during sitting, standing, and walking. Participants' heads are passively rotated at 100-300 °/s, and the ratio of eye velocity to head velocity (velocity gain) is calculated. A gain of 1.0 indicates perfect VOR function; 0 indicates complete absence.

Vestibulo-ocular reflex suppression (VORS) is assessed using a head-fixed target. Reflexive eye drift opposite to head movement is measured in sitting, standing, and walking. VORS is calculated as the ratio of eye position to head position (position gain). A score of 100% indicates full expression of the vestibuloocular reflex (VOR) (no suppression), while 0% indicates complete suppression.

Saccades are rapid eye movements used to fixate on new visual targets. Using the eye-tracker, saccade velocity (°/s) is recorded and analyzed to detect abnormalities such as slowed or dysmetric movements.

The glabellar reflex is assessed by repeated tapping of the participant's glabella. Normally, the blink response habituates after 3-5 taps. Persistent blinking beyond this suggests reduced frontal lobe inhibition. The total number of blinks is recorded.

The pupillary light reflex is assessed by alternately illuminating each eye. An eye-tracker records pupil size, shape, latency, and constriction velocity. Asymmetric responses may indicate neurological deficits. Differences between eyes are quantified, with thresholds based on clinical norms.

Resting pupil size is measured and compared to normative thresholds. Values outside defined ranges are classified as mydriasis (dilated), miosis (constricted), or normal.

Nystagmus is characterized by alternating slow and fast eye movements. At rest, the slow phase velocity (°/s) is recorded during gaze to the left and right using the eye-tracker.

Skew deviation is assessed using alternate eye cover testing while the participant fixates on a target. A positive result is indicated by vertical correction movements (geotropic/apogeotropic). The presence and magnitude of deviation are evaluated based on predefined thresholds.

Smooth pursuit (SP) is an eye movement in which a moving object is tracked by the eyes without moving the head. The tracking can be saccadic, i.e. jerky, or significantly impaired or incomplete in certain directions, such as upwards. Here, too, the investigators digitally record the extent of the eye movement during neurological examination.

A disturbance of the SP is indicated by the presence of correction Saccades, which are recorded digitally. As the corrective saccade is a physiological process, the saccade is preceded by a slow phase. During this slow phase, the eye The frequency of the saccades in a time unit is indicated and, if possible, the nature and amplitude. Threshold values for this result from a comparison with the clinical examination and the gestural impression.

The investigators measure the number of correction saccades per second as a measure of ability to maintain smooth pursuit.

The amplitude of the correction saccades, for example in °, during smooth pursuit (SP) also provides information about how saccades can be performed. Together with the number of saccades, it can provide information about the role that the ability to initiate and perform saccades plays during SP. Saccades may play a different role during SP than during gaze shifts.

The mean amplitude of the saccades is determined.

The saccades during smooth pursuit (SP) are preceded by a slow phase, the speed of which can be determined. The investigators calculate the mean of all slow phases in °/s.

Nystagmus is characterized by alternating slow and fast eye movements. The fast phase is expressed as a saccade, which is recorded and measured in degree.