A new way to measure the quality of artificial lighting based on non-visual light effects – melanopic EDI
This new international standard establishes a way to measure interior luminance, taking into account the effect of light on biological processes in the body through the non-image forming (NIF) system of the retina of the eye. This standard defines a readily measurable EDI lux quantity, the melanopic EDI (melanopic EDI, mEDI), which not only takes the image-forming but also the non-visual functions of light through its spectral composition (SPD) into account. In the expert advice, the authors defined optimal mEDI values for indoor lighting during different phases of the day in order to achieve the desired responses of the organism to light exposure.
The studies included in the analysis show that the stimulus effects of light with different spectral compositions are better predicted by mEDI compared to any other available metrics. This conclusion is relevant for both day, evening and night lighting. At the same time, most available laboratory results show that mEDI reflects well the spectral photosensitivity of human circadian and other non-image forming responses to light.
Results from laboratory studies
Available laboratory evidence shows that the mEDI better maps the effects of light on alertness and cognitive brain function than other metrics. They further confirm that increasing the mEDI value in lighting can promote an individual’s alertness throughout the day. When the recommendations presented in this document are implemented, circadian rhythms are properly synchronised and consequently promote healthy sleep, increased alertness and mood, and overall vitality, as the light gives a clear signal of day or night and the disturbing effects of light in the evening are reduced.
Results from studies carried out in a real environment
Offices
In offices, an increase in mEDI (approximately double) had a positive effect on alertness, performance, mood and sleep quality. Increasing access to natural daylight in the workplace also improved objectively measured cognitive performance in office workers.
Schools
Lighting systems with higher mEDI (>500 lx) improved measured concentration and reading comprehension in schools compared to current standard lighting (typically providing mEDI <200 lx).
Nursing homes
The introduction of higher mEDI lighting has led to a number of improvements, including reduced depression, agitation and anxiety, improved daytime activity and improved sleep quality for nursing home residents.
