Summary
Spectrally different LED light sources with identical photopic luminance but different cirtopic (melanopic) luminance produce statistically indistinguishable pupil responses during daytime hours, but significantly different responses at night, particularly at midnight. This finding implies that circadian-effective lighting design must account for time of day, with nighttime environments being especially sensitive to the spectral (melanopic) content of light sources.
Key Findings
- Cirtopic effect on steady-state pupil diameter was not statistically different between the two LED sources during daytime (09:00 and 15:00).
- Cirtopic effect on pupil size was significantly different at nighttime, especially at midnight (02:00), despite matched photopic luminance and color temperature.
- Study used 20 healthy volunteers tested across four time points (09:00, 15:00, 21:00, 02:00) over five working days.
- Results indicate that melanopsin-driven pupillary sensitivity is time-of-day dependent, being greatest at night.
Categories
The Science of Light: Investigates melanopsin-driven (cirtopic) pupillary responses to spectrally different LED light sources with matched photopic luminance.
Sleep & Circadian Health: Demonstrates time-of-day dependence of the circadian (cirtopic) pupil response, relevant to understanding circadian entrainment and light sensitivity across the day.
Author(s)
F Rao, AHS Chan, X Zhu
Publication Year
2017
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Sleep & Circadian Health
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