Pupillary Dilation Reflex in Healthy Volunteers

Pupillary dilation amplitude is defined as the maximum increase in pupil diameter from the pre-stimulus baseline, measured in millimeters (mm) using the AlgometRx infrared pupillometer. Pupil diameter is recorded before, during, and for 10 seconds following each 1-second stimulus. Amplitude is assessed at each stimulation intensity, beginning at 1.0 mA and increasing in 1 mA steps until participant perception, followed by measurements at 2 mA and 4 mA above the perception threshold, at each of three frequencies (5 Hz, 250 Hz, and 2000 Hz). Reported as the mean pupillary dilation amplitude in millimeters at each intensity and frequency combination.

Variability of pupil diameter recorded by the AlgometRx infrared pupillometer during the pre-stimulation baseline period, while participants fixate on a visual marker in a quiet room under controlled lighting for up to 5 minutes. Variability is calculated as the standard deviation of pupil diameter, in millimeters (mm), across the final 30 seconds of the baseline recording. Reported as the mean standard deviation in millimeters.

Area under the curve (AUC) is calculated from the pupil diameter-time curve recorded over the 10-second period following each 1-second stimulus, using the AlgometRx infrared pupillometer, and is expressed in millimeter-seconds (mm*s). AUC is assessed at each stimulation intensity, beginning at 1.0 mA and increasing in 1 mA steps until participant perception, followed by measurements at 2 mA and 4 mA above the perception threshold, at each of three frequencies (5 Hz, 250 Hz, and 2000 Hz). Reported as the mean AUC in millimeter-seconds at each intensity and frequency combination.

Within-participant difference in pupillary dilation amplitude, measured in millimeters (mm) by the AlgometRx infrared pupillometer, between testing under approximately 100 lux and approximately 400 lux ambient lighting. Amplitude is defined as the maximum increase in pupil diameter from the pre-stimulus baseline. Reported as the mean within-participant difference in millimeters.

Agreement between left-eye and right-eye pupillary dilation amplitude recorded simultaneously using the AlgometRx binocular handheld attachment under identical stimulation and lighting conditions. Amplitude is defined as the maximum increase in pupil diameter from the pre-stimulus baseline, measured in millimeters. Agreement is expressed as an intraclass correlation coefficient (ICC) ranging from 0 to 1, where higher values indicate greater agreement between eyes. Reported as the ICC with a 95% confidence interval.

The percentage of participants in whom the AlgometRx binocular handheld attachment successfully captures interpretable simultaneous pupillary recordings from both eyes. A recording is considered successful if both pupils are tracked continuously throughout the stimulus and post-stimulus recording period. Reported as the percentage of participants with successful binocular recording.