Fig 1. A schematic example of the pupillometry measurement.

The figure shows a normal pupillometry. The mean pupillary diameter was normalized against the mean baseline pupil diameter. The pupils were video recorded for 10 seconds before light stimulation, 20 seconds during light stimulation called “Light ON” (blue arrow), and 40 seconds after light stimulation called “Light OFF” (black arrow). Early PIPR (light grey area) is the early post-illumination pupillary response recorded 0–10 seconds after the light turns off. Late PIPR (dark grey area) is the late post-illumination pupillary response (late PIPR) recorded 10–30 seconds after the light turns off [21].