Lighting hygiene, melanopic daylight efficacy ratios and energy efficiency

The second Manchester Workshop recommended minimum daytime eye-level exposures to light, and evening and night-time maximums, in terms melanopic equivalent daylight illuminance (melanopic EDI). In integrative lighting and healthy light hygiene regimes, the evening calls for lights with low melanopic daylight efficacy ratios (melanopic DERs) to realize sufficient illuminance for visual function whilst limiting melanopic EDI. In the daytime, where electric lighting is needed, a higher melanopic DER is desirable. Night -time may be considered an extreme version of evening, with a need for light by exception. It is a matter of social and economic importance that daytime, evening and night -time spectral objectives can each strongly conflict with the use of luminous efficacy to determine how much net positive utility derives from electrical energy and its CO2 footprint. This paper compares LED products, including melanopic engineered lighting systems, it discusses electrical energy efficiency implications and introduces the concept of “melanopic efficacy”

Lighting hygiene, melanopic daylight efficacy ratios and energy efficiency

The second Manchester Workshop recommended minimum daytime eye-level exposures to light, and evening and night-time maximums, in terms melanopic equivalent daylight illuminance (melanopic EDI). In integrative lighting and healthy light hygiene regimes, the evening calls for lights with low melanopic daylight efficacy ratios (melanopic DERs) to realize sufficient illuminance for visual function whilst limiting melanopic EDI. In the daytime, where electric lighting is needed, a higher melanopic DER is desirable. Night -time may be considered an extreme version of evening, with a need for light by exception. It is a matter of social and economic importance that daytime, evening and night -time spectral objectives can each strongly conflict with the use of luminous efficacy to determine how much net positive utility derives from electrical energy and its CO2 footprint. This paper compares LED products, including melanopic engineered lighting systems, it discusses electrical energy efficiency implications and introduces the concept of “melanopic efficacy”

Report on the Workshop Use and Application of the new CIE s 026/e:2018, Metrology for ipRGC-influenced responses to light “specifying light for its eye-mediated non-visual effects in humans”

In December 2018, the international standard CIE S 026/E:2018 “CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light” (doi.org/10.25039/S026.2018) was published. This standard defines spectral sensitivity functions, quantities and metrics to describe the ability of optical radiation to stimulate each of the five retinal photoreceptor classes that can contribute, via the melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs), to the retinally mediated non-visual effects of light in humans. This one-hour workshop started with four 10 minute presentations about the standard, followed by a general discussion and questions. The four presentations focused on the following topics:1) Introduction to CIE S 026 and its quantities (Luc Schlangen)2) Demonstration of toolkit (in preparation) to calculate CIE S 026 quantities (Presented by Luc Schlangen on behalf of Luke Price)3) Accounting for field of view (David Sliney)4) ipRGCs and pupil response (Manuel Spitschan

Degradation of biological potency in led light sources with lifetime

This paper investigates the degradation of biological potency in LED light sources over their lifetime. Biological potency refers to the ability of light to generate biological effects, for instance on sleep, mood, and circadian rhythms. Current lifetime metrics for LEDs typically do not consider the biological potency, despite its relevance for human health and well-being. Therefore, we investigate such metrics and explore blue light hazard changes over the lifetime of LEDs.Using a dataset of accelerated aging of LEDs, we show that the melanopic equivalent daylight luminance maintenance decreases faster than lumen maintenance, this effect is smaller in LEDs of 4000K versus 2700K. Over lifetime, the melanopic daylight efficacy ratio also decreases, while the blue light hazard does not significantly increase.Our findings highlight the need to consider changes in biological potency over time in the design and implementation of LED lighting solutions

Degradation of biological potency in led light sources with lifetime

This paper investigates the degradation of biological potency in LED light sources over their lifetime. Biological potency refers to the ability of light to generate biological effects, for instance on sleep, mood, and circadian rhythms. Current lifetime metrics for LEDs typically do not consider the biological potency, despite its relevance for human health and well-being. Therefore, we investigate such metrics and explore blue light hazard changes over the lifetime of LEDs.Using a dataset of accelerated aging of LEDs, we show that the melanopic equivalent daylight luminance maintenance decreases faster than lumen maintenance, this effect is smaller in LEDs of 4000K versus 2700K. Over lifetime, the melanopic daylight efficacy ratio also decreases, while the blue light hazard does not significantly increase.Our findings highlight the need to consider changes in biological potency over time in the design and implementation of LED lighting solutions

Blue-enriched Lighting for Older People Living in Care Homes: Effect on Activity, Actigraphic Sleep, Mood and Alertness

Objective: Environmental (little outdoor light; low indoor lighting) and age-related physiological factors (reduced light transmission through the ocular lens, reduced mobility) contribute to a light-deprived environment for older people living in care homes. Methods: This study investigates the effect of increasing indoor light levels with blue-enriched white lighting on objective (rest-activity rhythms, performance) and self-reported (mood, sleep, alertness) measures in older people. Eighty residents (69 female), aged 86 ± 8 yrs (mean ± SD), participated (MMSE 19 ± 6). Overhead fluorescent lighting was installed in communal rooms (n=20) of seven care homes. Four weeks of blue-enriched white lighting (17000 K ≅ 900 lux) were compared with four weeks of control white lighting (4000 K ≅ 200 lux), separated by three weeks wash-out. Participants completed validated mood and sleep questionnaires, psychomotor vigilance task (PVT) and wore activity and light monitors (AWL). Rest-activity rhythms were assessed by cosinor, non-parametric circadian rhythm (NPCRA) and actigraphic sleep analysis. Blue-enriched (17000 K) light increased wake time and activity during sleep decreasing actual sleep time, sleep percentage and sleep efficiency (p < 0.05) (actigraphic sleep). Compared to 4000 K lighting, blue-enriched 17000 K lighting significantly (p < 0.05) advanced the timing of participants’ rest-activity rhythm (cosinor), increased daytime and night-time activity (NPCRA), reduced subjective anxiety (HADA) and sleep quality (PSQI). There was no difference between the two light conditions in daytime alertness and performance (PVT). Conclusion: Blue-enriched lighting produced some positive (increased daytime activity, reduced anxiety) and negative (increased night-time activity, reduced sleep efficiency and quality) effects in older people

ENLIGHT:A consensus checklist for reporting laboratory-based studies on the non-visual effects of light in humans

Background: There is no consensus on reporting light characteristics in studies investigating non-visual responses to light. This project aimed to develop a reporting checklist for laboratory-based investigations on the impact of light on non-visual physiology. Methods: A four-step modified Delphi process (three questionnaire-based feedback rounds and one face-to-face group discussion) involving international experts was conducted to reach consensus on the items to be included in the checklist. Following the consensus process, the resulting checklist was tested in a pilot phase with independent experts. Findings: An initial list of 61 items related to reporting light-based interventions was condensed to a final checklist containing 25 items, based upon consensus among experts (final n = 60). Nine items were deemed necessary to report regardless of research question or context. A description of each item is provided in the accompanying Explanation and Elaboration (E&amp;E) document. The independent pilot testing phase led to minor textual clarifications in the checklist and E&amp;E document. Interpretation: The ENLIGHT Checklist is the first consensus-based checklist for documenting and reporting ocular light-based interventions for human studies. The implementation of the checklist will enhance the impact of light-based research by ensuring comprehensive documentation, enhancing reproducibility, and enabling data aggregation across studies. Funding: Network of European Institutes for Advanced Study (NETIAS) Constructive Advanced Thinking (CAT) programme; Sir Henry Wellcome Postdoctoral Fellowship (Wellcome Trust, 204686/Z/16/Z); Netherlands Organisation for Health Research and Development VENI fellowship (2020–09150161910128); U.S. Department of Defense Grant (W81XWH-16-1-0223); National University of Singapore (NUHSRO/2022/038/Startup/08); and National Research Foundation Singapore (NRF2022-THE004-0002).</p

CIE Software Check of luox.app

The University of Oxford has developed an open-access software platform known as luox, which incorporates elements of CIE publications for the calculation of certain quantities integrated from spectral data. Under the terms of a licence agreement between the University of Oxford and the CIE, the CIE has agreed to endorse the software following a black-box validation of the software. This is the report of that validation exercise, based on the work of an ad hoc task group of the CIE Board of Administration. The task group selected 43 spectrafrom various sources, 19 being spectra with 5 nm intervals and 24 being spectra with 1 nm intervals, and calculated luminance (illuminance), a-opic radiances (a-opic irradiances), a-opic equivalent daylight luminances (a-opic equivalent daylight illuminances), a-opic efficacies of luminous radiation, and chromaticity coordinates using both luox and a variety of other available reference calculation tools, both public and private. Tolerance intervals were established for each quantity, and the deviation between the test values from luox and thereference values were calculated for each spectrum. The results for all of these evaluations showed consistency between the test values and the reference values. Based on these results, the CIE approves the following statement concerning the luox software, as per the aforementioned licence agreement:“This software incorporates methods, formulae, spectral function calculations and spectra from the International Commission on Illumination (CIE). The CIE endorses this software having made a black-box evaluation of the software as of Feb. 11, 2021, finding that the software performs satisfactorily. This software is not a replacement for the CIE publications and works from which it is derived. The user is advised to consult the original publications and works for proper understanding of and calculation of the result of this software.

An inventory of human light exposure behaviour

Light exposure is an essential driver of health and well-being, and individual behaviours during rest and activity modulate physiologically relevant aspects of light exposure. Further understanding the behaviours that influence individual photic exposure patterns may provide insight into the volitional contributions to the physiological effects of light and guide behavioural points of intervention. Here, we present a novel, self-reported and psychometrically validated inventory to capture light exposure-related behaviour, the Light Exposure Behaviour Assessment (LEBA). An expert panel prepared the initial 48-item pool spanning different light exposure-related behaviours. Responses, consisting of rating the frequency of engaging in the per-item behaviour on a five-point Likert-type scale, were collected in an online survey yielding responses from a geographically unconstrained sample (690 completed responses, 74 countries, 28 time zones). The exploratory factor analysis (EFA) on an initial subsample (n = 428) rendered a five-factor solution with 25 items (wearing blue light filters, spending time outdoors, using a phone and smartwatch in bed, using light before bedtime, using light in the morning and during daytime). In a confirmatory factor analysis (CFA) performed on an independent subset of participants (n = 262), we removed two additional items to attain the best fit for the five-factor solution (CFI = 0.95, TLI = 0.95, RMSEA = 0.06). The internal consistency reliability coefficient for the total instrument yielded McDonald’s Omega = 0.68. Measurement model invariance analysis between native and non-native English speakers showed our model attained the highest level of invariance (residual invariance CFI = 0.95, TLI = 0.95, RMSEA = 0.05). Lastly, a short form of the LEBA (n = 18 items) was developed using Item Response Theory on the complete sample (n = 690). The psychometric properties of the LEBA indicate the usability for measuring light exposure-related behaviours. The instrument may offer a scalable solution to characterise behaviours that influence individual photic exposure patterns in remote samples. The LEBA inventory is available under the open-access CC-BY license. Instrument webpage: https://leba-instrument.org/ GitHub repository containing this manuscript: https://github.com/leba-instrument/leba-manuscript