Light is an important way that our bodies calibrate our internal clock (circadian rhythm). When light (especially blue light) enters the eye, signals go to the brain, where the biological clock is set. A method we use to assess sensitivity to light is pupillometry. Participants sit in a completely dark room for about 10 minutes to let themselves get used to the dark. Participants then put their eyes up to the pupillometer, a set of goggles with a camera and flashing lights. The lights flash bright blue and red light, which can be temporarily uncomfortable, but is totally safe. The camera in the goggles records pupil activity as it expands and contracts in response to the light. This test is done in multiple studies, including RAM, DAYLight, and SleepChart.
DP-2000 Pupillometer:
Oculox Pupillometer:
