Summary
This review highlights that the direction of light incident on the retina matters for non-image-forming effects (e.g., circadian regulation, alertness), because ipRGCs are not uniformly distributed across the retina. Lighting designers should consider not just light intensity and spectrum, but also the angle and vertical illuminance of light sources to maximize health-relevant retinal stimulation.
Key Findings
- ipRGCs show a non-uniform spatial distribution on the retina, with higher density in certain regions, meaning light direction influences the magnitude of non-image-forming (NIF) responses.
- Overhead/superior-field lighting may stimulate ipRGCs more effectively than equivalent light from below, suggesting ceiling and luminaire positioning is critical for circadian effectiveness.
- Animal and human studies indicate that the angle of light incidence contributes meaningfully to the magnitude of NIF effects such as melatonin suppression and pupillary light reflex.
- Current lighting standards largely ignore directionality as a parameter, representing a gap in optimizing lighting for human health outcomes.
Categories
The Science of Light: Reviews ipRGC spatial distribution on the retina and how light direction/angle of incidence affects non-image-forming photobiological responses.
Sleep & Circadian Health: Discusses how radiation directionality influences circadian and health-relevant stimulation of ipRGCs, with implications for entrainment and wellbeing.
Workplace Performance: Provides design guidance for incorporating directionality into building lighting to optimize human health and performance outcomes.
Author(s)
P Khademagha, M Aries, A Rosemann
Publication Year
2016
Number of Citations
16
Related Publications
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice
Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors
Workplace Performance
- Acute alerting effects of light: A systematic literature review
- Effects of artificial dawn and morning blue light on daytime cognitive performance, well-being, cortisol and melatonin levels
- Can light make us bright? Effects of light on cognition and sleep
- Kruithof's rule revisited using LED illumination
- Shining light on memory: Effects of bright light on working memory performance