CIE Position Statement on Non-Visual Effects of LightRECOMMENDING PROPER LIGHT AT THE PROPER TIME
2nd Edition1
October 3, 2019

Background
Light is defined as any electromagnetic radiation that can create a visual sensation bydirectly stimulating the retinal photoreceptors of the visual system. In addition to enabling
vision, these photoreceptors also drive biological effects that powerfully regulate humanhealth, performance and well-being. Light is the main synchronizer of the human biologicalclock. It can shift the phase of the circadian rhythm and can regulate the timing and quality ofour sleep. Light in the evening and at night can disrupt sleep and can cause acutesuppression of the nocturnal release of the hormone melatonin. There are also reports thatlight can increase heart rate, improve alertness, alleviate seasonal and non-seasonal
depression, influence thermoregulation, and affect brain activity as measured with theelectroencephalogram (EEG). Exposure to light elicits fast responses (in the range ofmilliseconds and seconds) in the pupillary reflex or in brain activity. To reflect their distinction
from perceptual vision, these effects are often referred to as non-image-forming (NIF) or nonvisual (NV) responses to light. In recent years various marketing terms, such as “humancentric lighting” (HCL), “circadian lighting”, and “biodynamic lighting”, have come to describe
lighting solutions that target such effects. In the upcoming 2nd edition of the CIE International
Lighting Vocabulary, currently available as DIS (CIE 2016), “integrative lighting” is the official
term for lighting that is specifically intended to integrate visual and non-visual effects,
producing physiological and psychological effects on humans that are reflected in scientificevidence.
The above-mentioned biological effects of light are elicited by stimulation of ocular
photoreceptors. The classical receptors for vision, the rods and cones, are relatively wellunderstood and characterized by existing CIE publications. Pioneering work over the last 25
years revealed that the eye has another kind of photoreceptor. These photoreceptors play animportant role in non-visual effects of light and have a peak sensitivity in the shorter
wavelength part of the visible spectrum. Such photoreceptors are known as intrinsicallyphotosensitive retinal ganglion cells (ipRGCs), and their intrinsic photosensitivity is based onthe photopigment melanopsin.
Based on the outcome of an independent workshop of leading scientists in the field of
quantifying light for non-visual effects in Manchester in 2013 (see CIE TN 003:2015 (CIE2015)), the CIE issued an international standard, CIE S 026:2018 (CIE 2018), that defines asystem for metrology of optical radiation for light-induced responses that can be elicited by
ipRGCs (ipRGC-influenced light (IIL) responses).

1 This edition replaces the 2015 CIE Position Statement on the same subject.

Lighting regulations and practice often still focus on visual and energy efficiency aspects oflight, with little or no attention being paid to IIL responses. Conversely, there are manylighting products entering the market that are intended primarily to influence IIL without
careful consideration of other lighting quality aspects. An improper balance between these
two approaches can result in lighting conditions that compromise human well-being, healthand functioning and that fail in terms of overall lighting quality. Since the first edition of thisPosition Statement in 2015, the CIE has issued relevant publications and engaged incollaborative activities to advance this exciting aspect of lighting fundamentals, technology
and applications.
1. How to characterize light with respect to its non-visual effects: CIE S 026:2018 “CIESystem for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light”
The International Standard CIE S 026:2018 (CIE 2018) defines spectral sensitivity functions,quantities and metrics to describe the ability of optical radiation to stimulate each of the five(-opic2) photoreceptor types that can contribute, via the melanopsin-containing intrinsicallyphotosensitive retinal ganglion cells (ipRGCs), to retina-mediated non-visual effects of light inhumans3. The units of these -opic quantities are in compliance with the International
System of Units (SI) (BIPM 2019a, BIPM 2019b), which is essential to enable traceable
measurements and international guidelines.
For non-image-forming effects of light, a description of optical radiation solely according to
the photopic action spectrum is not sufficient. Moreover, there is no single action spectrum orproxy that can describe all eye-mediated non-visual responses to light. All five receptor types
can contribute to these responses (Lucas et al. 2014). The relative contribution of eachindividual photoreceptor type can vary depending on the specific response and upon light
exposure properties such as intensity, spectrum, duration, timing (external andinternal/circadian), prior light history and sleep deprivation state of the individual. It is worth
noting that in many cases light exposure for IIL responses is better represented by using thevertical measurement plane rather than the horizontal plane to determine -opic irradiance(or -opic equivalent daylight (D65) illuminance (-opic EDI)).
2. Identifying the proper light at the proper time
This remains a key question for many people. As outlined in the 2015 position statement, theCIE is actively engaged with the international community in attempting to provide guidance
that is based on solid scientific evidence and consensus. The CIE and ISO/TC 274 aredeveloping the first international consensus-based technical report concerning integrative
lighting (ISO/CIE TR 21783, in preparation), noting both its potential beneficial effects and its
possible risks that are to be avoided. Furthermore, in August 2019, a second independentworkshop of leading scientists in this field took place in Manchester to discuss how insights
in this field can be translated into guidelines for a healthy daily pattern of light exposure. A
consensus publication on the outcomes of the workshop is currently being prepared by theworkshop participants and will be followed by a CIE Technical Note reporting on theworkshop in detail.
The CIE recognizes that spending adequate time outdoors during the day is associated with
better health and well-being, and that exposure to natural light is a significant causal

2 The term -opic represents S-cone-opic, M-cone-opic, L-cone-opic, rhodopic or melanopic.

-opic photoreceptor classes (S-cones, M-cones, Lcones, rods and ipRGCs), tabulated in steps of 1 nm, are available at
http://files.cie.co.at/S026_Table2_Data.xlsx.

3 The CIE S 026 action spectra of the five humancomponent in these effects. CIE also recommends not to unnecessarily restrict daylightwithin indoor settings.
For two important, well-studied human non-visual responses to light (melatonin suppression
and pupil control), evidence is accumulating that the overall light sensitivity of these
responses is largely controlled by melanopsin-based photoreception (Nowozin et al. 2017,
Souman et al. 2018, Prayag et al. 2019, Spitschan 2019). In order to provide some initial
guidance while waiting for the participants of the August 2019 workshop in Manchester todevelop further insights and consensus in this field, the CIE recommends the manipulation ofmelanopsin-based photoreception as a useful strategy to manipulate overall light input into
non-visual responses. This means that specifications in terms of melanopic EDI are areasonable route to provide initial guidance on how to manipulate the human (polychromatic)
lighting environment in typical everyday life for non-visual responses in people with a regular,
day-active schedule (as long as these specifications are not compromising visual comfortand visual performance):
 A high melanopic EDI during the day is usually supportive for alertness, the circadianrhythm and a good night’s sleep.
 A low melanopic EDI in the evening and at night facilitates sleep initiation andconsolidation.
Suitable light patterns for night-shift workers are more complex, as they depend on thespecific schedule.

Further CIE Strategy
Delivering proper light at the proper time will require integrative approaches that meet theneeds of all the people within a space. Ongoing CIE projects in this field include the joint
activity with ISO/TC 274 to revise the international standard for indoor workplace lighting,ISO 8995-1:2002/CIE S 008:2001 (ISO/CIE 2002).
The CIE is committed throughout all of its work, to providing scientifically-groundedrecommendations and to advancing science that will support the next generation ofstandards. The development of proper evidence-based recommendations continues todemand concerted research efforts, and the CIE in its Research Strategy calls upon theresearch community to engage in developing this knowledge base. As a support toresearchers and practitioners in this field, a toolbox to facilitate the application of CIE S
026:2018 will shortly be available on the CIE website. Researchers proposing to study topics
relevant to the CIE Research Strategy may apply to the CIE for a letter of support for theproposal by emailing a request form to ciecb@cie.co.at.

References
BIPM (2019a) The International System of Units (SI), 9th Edition
Downloadable at https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9-EN.pdf
BIPM (2019b) The International System of Units (SI), 9th Edition – Appendix 3: Units forphotochemical and photobiological quantities
Downloadable at https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9-App3EN.pdf
CIE (2015) CIE TN 003:2015 Report on the First International Workshop on Circadian and
Neurophysiological Photometry, 2013
Downloadable at http://files.cie.co.at/785_CIE_TN_003-2015.pdfCIE (2016) CIE DIS 017:2016 ILV: International Lighting Vocabulary, 2nd Edition
CIE (2018) CIE S 026:2018 CIE System for Metrology of Optical Radiation for ipRGCInfluenced Responses to Light
ISO/CIE (2002) ISO 8995-1:2002/CIE S 008:2001 Lighting of Work Places - Part 1: Indoor
ISO (in preparation) ISO/CIE TR 21783 Light and lighting — Integrative lighting — Non-visualeffects
Lucas, R.J., Peirson, S.N., Berson, D.M., Brown, T.M., Cooper, H.M., Czeisler, C.A.,
Figueiro, M.G., Gamlin, P.D., Lockley, S.W., O'Hagan, J.B., Price, L.L., Provencio, I., Skene,D.J., Brainard, G.C. (2014) Measuring and using light in the melanopsin age. Trends inNeuroscience 37(1): 1-9.
Nowozin, C., Wahnschaffe, A., Rodenbeck, A., de Zeeuw, J., Hadel, S., Kozakov, R.,
Schopp, H., Munch, M., Kunz, D. (2017) Applying Melanopic Lux to Measure Biological Light
Effects on Melatonin Suppression and Subjective Sleepiness. Curr Alzheimer Res 14(10):1042-1052.
Prayag, A.S., Najjar, R.P., Gronfier, C. (2019) Melatonin suppression is exquisitely sensitiveto light and primarily driven by melanopsin in humans. Journal of Pineal Research 0(ja):e12562.
Souman, J.L., Borra, T., de Goijer, I., Schlangen, L.J.M., Vlaskamp, B.N.S., Lucassen, M.P.
(2018) Spectral Tuning of White Light Allows for Strong Reduction in Melatonin Suppression
without Changing Illumination Level or Color Temperature. Journal of Biological Rhythms
33(4): 420-431.
Spitschan, M. (2019) Photoreceptor inputs to pupil control. Journal of Vision 19(9): 5-5

About the CIE and its Position Statements
The International Commission on Illumination – also known as the CIE from its French title,the Commission Internationale de l´Eclairage – is devoted to worldwide cooperation and theexchange of information on all matters relating to the science and art of light and lighting,colour and vision, photobiology and image technology.
With strong technical, scientific and cultural foundations, the CIE is an independent, nonprofit organization that serves member countries on a voluntary basis. Since its inception in1913, has been accepted as representing the best authority on the subject and as such isrecognized by ISO as an international standardization body. As such the CIE is recognizedby ISO as an international standardization body, publishing global standards on thefundamentals of light and lighting.
CIE position statements are approved by the CIE Board of Administration, which includes theDirectors of all the CIE Divisions (the bodies that carry out the scientific work of the CIE),
after first ensuring agreement with the relevant CIE Technical Committees.
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