Light does not only give a person the ability to perceive his/her environment: it is also able to influence numerous non-visual effects, by stimulating the intrinsically photosensitive retinal ganglion cells (ipRGCs). The ipRGC does not have an influence on the perception of one’s environment, while they are present in the retina, similar to the known rods and cones. The amount of stimulation of the ipRGC depends on the melanopic Equivalent Daylight Illuminance (mEDI) in the light. Different mEDI light conditions can be manipulated, whilst not changing the stimulation of the S, M or L cones, using the silent substitution method. In this research, the influence of ipRGC stimulation on alertness is investigated. A within-subject experiment is conducted, where participants are placed in front of the Boschman Colourbox. Participants consisted of 6 male and 16 female students, with a mean age of 20.63 years (N = 22, SD = 1.44). The participants are exposed to a series of six lights: three of the lighting conditions are of low illuminance (60 lux) and three of high illuminance (300 lux). Within both illuminances, the conditions had 3 levels in terms of mEDI, namely low, medium and high. The order of the illuminances are randomized, whilst the mEDI level is randomized within the illuminance. The alertness of the participant is measured via the Karolinska Sleepiness Scale (KSS) and the pupillary unrest index (PUI). Multiple multi-level regression models are calculated to analyze the relationship of the different lighting conditions and alertness. The data suggests that increasing the mEDI results in higher alertness, where an increasing illuminance also resulted in higher alertness.
The relationship between ipRGC activation and alertness using metamers
Struijk, D. (Author). 2022
Student thesis: Bachelor