Non-visual Effects Research Articles

Influence of the perceived size of a light source on non-visual effects in humans

Abstract Light not only enables humans to perceive their surroundings, but also influences their sleep–wake cycle, mood, concentration and performance. Targeted use of these so called nonvisual effects could also have a positive contribution in automobiles by keeping passengers alert, minimizing error rates or bootsting attention in general. Since construction space in vehicle interios is scarce, this study compared the influence of differently-sized light panels and thus solid angles on nonvisual effects. In a counterbalanced order, 32 volunteers were exposed to three lighting conditions in the morning: baseline (12 lx, 2200 K), small (200 lx, 6500 K, 0.05 sr) and large (200 lx, 6500 K, 0.44 sr). During each session of 60 min, alertness, concentration and working memory were assessed before and during light exposure. After data analysis no significant main effects of light, measurement point or interaction between light and measurement point could be seen.

Present And Future Activities Of The International Commission On Illumination (CIE)

The article describes the main activities of the International Commission on Illumination in recent years. The most important publications are reflecting recent developments in lighting science and industry, including LED sources and luminaires test methods, fundamental recommendations concerning colorimetry, discomfort caused by glare from luminaires with a non-uniform luminance, as well as intelligent control of lighting systems. Human centric lighting and the non-visual effects of light on humans was highlighted. To promote standardization in the field of horticultural lighting the CIE is in the process of establishing a new JTC. In view of COVID‑19 pandemic outspread the use of germicidal UV radiation is of relevance to reduce both contact spread and airborne transmission of infectious agents. The CIE is responsible for worldwide standardization of the fundamentals, including metrology and vocabulary, as well as lighting education. The CIE considers it important to make digital products including validated calculation tools, apps, databases and machine-readable documents more available for many experts and it takes a step in this direction by provide open access to the individual CIE publications.

Matching CIE illuminants to measured spectral power distributions: A method to evaluate non-visual potential of daylight in two European cities

The evaluation of non-visual effects of light is a crucial topic in lighting design research and practice. Performing such analysis requires precise information about the spectral distribution of the tested light source. Assessing non-visual effects of daylight is complicated due to its spectral composition continuously changing, depending on many factors. Currently there are no available databases with spectral and spatial radiation patterns of the sky vault for locations spread all over the world, and an easy and common method to evaluate non-visual effects of daylight is lacking.The goal of the paper is to provide a simple method to evaluate the non-visual potential of daylight, accounting for its variability. In order to present it, spectral measurements were conducted in two European cities in spring and summer. Horizontal and vertical illuminance toward the four cardinal directions was measured. Daylight variability was analysed in terms of illuminance, Correlated Colour Temperature (CCT) and Melanopic to Photopic (M/P) ratio. A comparison between the measured spectra and the CIE standard illuminants was performed and it was found that the usefulness of this method to evaluate non-visual effects of light in terms of M/P is adequate and provides reliable results. Therefore, a simple method to estimate the non-visual potential of daylight based on the use of D series of illuminants was presented and validated by comparing the results with the measured data. Using this method to calculate M/P always achieves RMSPEs below 6%.

Blue-Light Levels Emitted from Portable Electronic Devices Compared to Sunlight

Over recent years, a technological revolution has taken place in which conventional lighting has been replaced by light emitting diodes (LEDs). Some studies have shown the possibility that blue light from these artificial sources could have deleterious effects on the retina. Considering that people spend a non-negligible time in front of screens from computers and mobile phones, the eyes receive blue light of different intensities depending on the source. Nevertheless, any study about the visual and non-visual effects of blue light must consider precise measurements taken from actual artificial sources. For this reason, we have analyzed the spectral emission of 10 different electronic devices and weighted them according to the hazard caused by blue light to the eyes, comparing the results with solar radiation simulated with a radiative transfer model. The maximum spectral irradiance of the measured electronic devices at 10 cm from the detector was located between 440 nm and 460 nm. The irradiance for blue light hazard ranged from 0.008 to 0.230 Wm−2 depending on the particular characteristics of each electronic device. In contrast, the solar radiances in the same spectral range are larger both under clear and cloudy conditions.

Circadian metric – Computation of circadian stimulus using illuminance, correlated colour temperature and colour rendering index

The circadian rhythm is influenced by light and other non-visual responses in humans. Recent researches have shown that the visual quantity illuminance is not appropriate for evaluating non-visual effects. Metrics such as the circadian stimulus have been developed to address this issue. One of the limitations with circadian metrics is that the determination requires a spectroradiometer instead of the standard illuminance meters. In this article, a simple circadian stimulus calculation model for white light sources is presented. The model is determined with the parameters illuminance, correlated colour temperature CCT and colour rendering index Ra. The accuracy and reliability of the model is high and is based on 7641 spectra with 19 illuminance levels, which are generated using a heuristic optimisation procedure. In addition, the model has been internally validated with the method repeated-split-data and has an error deviation of 0.058 for CCT > 3710 K and 0.045 for CCT ≤ 3710 K at 99% confidence interval in the circadian stimulus CS range between 0.2 and 0.5. Since the quantities illuminance, correlated temperature and colour rendering index are common in practice, this model enables non-visual planning of illumination installations by lighting designers or lighting design tools. Furthermore, it allows retrospective analysis of past non-visual research results in scientific studies, where illuminance and correlated colour temperature were provided.

Modeling melanopsin-mediated effects of light on circadian phase, melatonin suppression, and subjective sleepiness.

A physiologically based model of arousal dynamics is improved to incorporate the effects of the light spectrum on circadian phase resetting, melatonin suppression, and subjective sleepiness. To account for these nonvisual effects of light, melanopic irradiance replaces photopic illuminance that was used previously in the model. The dynamic circadian oscillator is revised according to the melanopic irradiance definition and tested against experimental circadian phase resetting dose-response and phase response data. Melatonin suppression function is recalibrated against melatonin dose-response data for monochromatic and polychromatic light sources. A new light-dependent term is introduced into the homeostatic weight component of subjective sleepiness to represent the direct alerting effect of light; the new term responds to light change in a time-dependent manner and is calibrated against experimental data. The model predictions are compared to a total of 14 experimental studies containing 26 data sets for 14 different spectral light profiles. The revised melanopic model shows on average 1.4 times lower prediction error for circadian phase resetting compared to the photopic-based model, 3.2 times lower error for melatonin suppression, and 2.1 times lower error for subjective sleepiness. Overall, incorporating melanopic irradiance allowed simulation of wavelength-dependent responses to light and could explain the majority of the observations. Moving forward, models of circadian phase resetting and the direct effects of light on alertness and sleep need to use nonvisual photoreception-based measures of light, for example, melanopic irradiance, instead of the traditionally used illuminance based on the visual system.

The potential of circadian lighting in office buildings using a fibre optics daylighting system in Beijing

This study presents an investigation of circadian lighting potential for a fibre optics daylighting system (FODS) in a single office in Beijing, China. Research methods included the monitoring of FODS daylighting performance during a 11-month period, the indoor lighting simulations at the horizontal workplane and vertical planes using a single office model, and thus the theoretical calculations of circadian stimulus brought by the FODS. Key findings are as follows: There is a high possibility that a proper level of circadian light at a windowless workspace could be achieved through applying the FODS in northern China. With this FODS, the non-visual effect of lighting (circadian system entrainment) can be attained when a standard lighting requirement was met at the horizontal workplane based on occupants' visual performance in this office. Compared with typical artificial lighting systems, the FODS can deliver circadian light in a more efficient way. In addition, it can be found that the application of FODS system would benefit office workers in terms of both visual and non-visual aspects. It is the first study to investigate the non-visual performance of a fibre optics daylighting system.

Towards a Sustainable Indoor Lighting Design: Effects of Artificial Light on the Emotional State of Adolescents in the Classroom

In recent years, articles have been published on the non-visual effects of light, specifically the light emitted by the new luminaires with light emitting diodes (LEDs) and by the screens of televisions, computer equipment, and mobile phones. Professionals from the world of optometry have raised the possibility that the blue part of the visible light from sources that emit artificial light could have pernicious effects on the retina. The aim of this work is to analyze the articles published on this subject, and to use existing information to elucidate the spectral composition and irradiance of new LED luminaires for use in the home and in public spaces such as educational centers, as well as considering the consequences of the light emitted by laptops for teenagers. The results of this research show that the amount of blue light emitted by electronic equipment is lower than that emitted by modern luminaires and thousands of times less than solar irradiance. On the other hand, the latest research warns that these small amounts of light received at night can have pernicious non-visual effects on adolescents. The creation of new LED luminaires for interior lighting, including in educational centers, where the intensity of blue light can be increased without any specific legislation for its control, makes regulatory developments imperative due to the possible repercussions on adolescents with unknown and unpredictable consequences.

CHARACTERIZING PROTECTION ABILITY OF BLUE BLOCKING LENSES USING K-MEANS CLUSTERING

Blue light protection ophthalmic lenses have been regularly marketed as the ultimate protection against short-wavelength visible radiation mainly in the range of 400 nm and 450 nm. However, the actual protective effects of such lenses are currently unknown; most claims are provided by the manufacturers with limited scientific validation. This will not only make selling such lenses challenging but may provide the lens wearers little or no protection against the blue light hazard. It is recently discovered that the protection needs to take into accounts the light source that the wearers wish to protect from – heavy electronic gadget users for instance, are exposed to different spectrum of radiation compared to non-users. This problem is aggravated when the hazard needs to further be classified into the visual and non-visual effects. Non-visual impact includes the disruption in the circadian cycle which is governed by the physiological cycles of our body within 24 hours such as the melatonin hormone secretion. Such knowledge will help to educate optometrist to explain to their prospective customers and will also assist the spectacle wearers to make an informed decision based on validated scientific data.

Melanopic illuminance defines the magnitude of human circadian light responses under a wide range of conditions.

Ocular light drives a range of nonvisual responses in humans including suppression of melatonin secretion and circadian phase resetting. These responses are driven by intrinsically photosensitive retinal ganglion cells (ipRGCs) which combine intrinsic, melanopsin-based, phototransduction with extrinsic rod/cone-mediated signals. As a result of this arrangement, it has remained unclear how best to quantify light to predict its nonvisual effects. To address this, we analysed data from nineteen different laboratory studies that measured melatonin suppression, circadian phase resetting and/or alerting responses in humans to a wide array of stimulus types, intensities and durations with or without pupil dilation. Using newly established SI-compliant metrics to quantify ipRGC-influenced responses to light, we show that melanopic illuminance consistently provides the best available predictor for responses of the human circadian system. In almost all cases, melanopic illuminance is able to fully account for differences in sensitivity to stimuli of varying spectral composition, acting to drive responses that track variations in illumination characteristic of those encountered over civil twilight (~1-1000 lux melanopic equivalent daylight illuminance). Collectively, our data demonstrate widespread utility of melanopic illuminance as a metric for predicting the circadian impact of environmental illumination. These data therefore provide strong support for the use of melanopic illuminance as the basis for guidelines that seek to regulate light exposure to benefit human health and to inform future lighting design.

Topics Important for the up-to-date Interior Lighting Professional

To avoid disappointments with LED lighting installations, detailed knowledge of the typical characteristics of the many different solid-state light sources is essential, while already long-available information on vision and colour seeing has to be combined with entirely new fundamental research on the relationship between lighting on the one hand and vision, performance, comfort, health and well-being on the other hand. Lighting has apart from visual effects also far-reaching non-visual biological effects. These effects influence the way our body “operates” and therefore, influence our health, well-being and alertness. Interior lighting installations today have to be designed so that they provide both suitable visual and non-visual biological effects, while adverse effects of lighting, like flicker, blue light hazard and disruption of the biological clock, are avoided. LEDs offer the possibility to use them not only for lighting but also for data transmission. The use of LED lighting as a means for data communication is referred to as “light beyond illumination”. Visible Light Communication (VLC), LiFi, and light itself used as sensor are part of this subject. The modern lighting professional has to get familiarised with these new technologies and applications. The author of this article published in 2019 the book “Interior Lighting, fundamentals, technology and application” with Springer [1]. It discusses in 500 pages all topics important for the up-to-date interior lighting professional. The present overview article is entirely based on this book and follows the same chapter structure. Each chapter also describes, as an example, one or two crucial aspects in more detail.

Non-Visual Exposure to Light as a Production Factor of the Influence of Lighting of the Working Area on Labor Productivity and Safety of Workers

The statistical data on the level of occupational injuries, which is caused by the discrepancy between the quantitative and qualitative characteristics of the working area illumination and the established stan­dards, are presented. The characteristics and features of the functioning of the human visual analyzer are described. Characterized by the non-visual effect of light on the human body. Developed recommendations on the organization of industrial lighting, which will provide a reduction in the level of occupational morbidity and industrial injuries.

UNDERSTANDING BLUE LIGHT'S EFFECTS

DISPLAYS HAVE BECOME AN indispensable part of life—we use computers, tablets, smartphones, and other devices during the day for work, and at night for entertainment. Many of the self-luminous displays use LED backlight technology that includes blue-emitting LEDs with a narrowband emission of 450–470 nanometers (nm). The white backlight is created by combining three colors from red, green, and blue (RGB) LEDs, or by using phosphor-converted white LEDs or blue LEDs with quantum-dot enhancement film. Phosphor-converted LEDs are relatively inexpensive. The technology has been used to create highly efficient white light sources that provide significant energy savings, and LED solid-state lighting is now available in a wide variety of home and industrial products. Phosphor-converted LEDs are also richer in blue components compared to other artificial light sources, and their spectra are significantly different from that of incandescent or fluorescent lamps.1, 2 More to Uncover Some aspects of blue light's effect on health are far from settled. Image: GIPhotoStock/Science Source Presently, blue light's effect on human health—in particular, the human vision system—is highly and frequently debated. It's now well-accepted that the non-visual effects of light significantly impact our circadian system. We need exposure to blue-rich morning light for regulation of our biological rhythms, improved sleep quality, and other health benefits.2 However, overexposure to blue light in the evening, especially from self-luminous displays, results in circadian disruption. But is blue light harmful to our eyes? Displays deliver illumination directly into the eyes, as opposed to the reflected light received when reading paper books. Researchers have found that exposure to bright short-wavelength light (a “phototoxic band” of 440–470 nm) can cause permanent retinal damage; this is often referred to as blue-light hazard (BLH). The light-induced damage can result from viewing either incredibly bright light for a short time (up to 12 hours) or a less bright light for a longer duration (days to weeks). The BLH to the retina depends on the light source's radiance, which does not decrease with distance. To assess the risk, we must consider the source's radiance, its spectral distribution, and the retina's duration of exposure. We obtain the blue-light weighted radiance by multiplying the source's spectrum by the BLH function and integrating the product of this multiplication. The obtained value is compared to the radiance limits. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) provides an exposure limit of 100 watts per square meter per steradian (W m−2 sr−1) for viewing blue light without adverse effects for more than three hours.3 According to the guidelines, if a white light source's radiance doesn't exceed 104 candelas per square meter (cd/m2), evaluating its blue-light weighted radiance isn't required. Displays operate at a lower brightness that doesn't exceed the ICNIRP's luminance value; for example, the maximal brightness of the iPhone X is about 625 cd/m2.4 Still, little is understood about long-term exposure to lower levels. Brightness of LEDs is significantly higher; they offer > 4,000 lumens (Im) per package, which can exceed 104 cd/m2.5 Interestingly, one paper suggested that it would be useful to classify LEDs and other illuminants by their potential hazard to the eye, as they're labeled with respect to their energy efficiency already.6 This issue of Information Display includes the Frontline Technology article “Investigating Blue-Light Exposure from Lighting and Displays,” an important review by two experts in this area of research, John D. Bullough and Stefan Peana. It summarizes current views on blue-light risks and their effect on ocular health. The topic is relevant to you as both a professional in the display industry and a user of displays. It might be prudent, for example, to reduce the color temperature of your display and lower the amount of blue light emitted for viewing comfort and long-term eye health. It was difficult to write this editorial, as there is a lot of information on the BLH topic, as well as some unknowns. But as research continues and our knowledge advances, we will keep you updated. Marina Kondakova, Ph.D., is the director of device formulation at OLEDWorks. She can be reached at mkondakova552@gmail.com.

Applications in sleep: How light affects sleep.

Sleep is an active physiological state that plays a critical role in our physical and mental health and well-being. It is generated by a complex interplay between two oscillators, namely, the circadian oscillator and the sleep-wake homeostat. Sleep propensity is a function of wakefulness, that is, the longer one is awake the greater the homeostatic sleep pressure. Sleep onset occurs as a wake promoting circadian signal subsides, coinciding with an evening rise in melatonin and drop in core temperature. Light is one of the strongest time signals for the circadian oscillator. Poor sleep is a prevalent complaint today, attributable, in part, to our easy access to artificial light, especially after dusk. This non-visual effect of light is mediated by a multi-component photoreceptive system, consisting of rods, cones and melanopsin-expressing intrinsically-photosensitive retinal ganglion cells (ipRGC). Perhaps, with this available biological knowledge we can engineer artificial light to minimize its disruptive effect on sleep. We will highlight this by discussing circadian photoreception and its effect on sleep, in the blind population.

Lighting design factors contributing to circadian stimulation in offices

Light synchronizes biological functions through photoreceptors: cones and rods regulate color and twilight vision, respectively, generating visual light effects that originate the current lighting design. In turn, retinal ganglion cells synchronize the circadian cycle, a non-visual light effect in charge of regulating body temperature, mood, and the suppression/secretion of melatonin, all variables linked to productivity, motivation, and emotional wellbeing. Currently, natural light and illumination design are critical for wellbeing in the office. This work shares the findings of a research aimed at assessing the design factors that impact on the circadian cycle stimulus, highlighting the relevance of this non-visual effect of light. A diagnostic was made of office spaces to subsequently suggest circadian stimulus strategies that consider the visual system in full.

Application of healthful lighting: Research progress and prospects

Light is a key component for life on Earth. Lighting quality is thought to be one of the most important factors influencing people’s work and living conditions in building spaces. A complete standardization system has been established on the basis of comprehensive research concerning visual performance and comfort under lighting situations with traditional lighting technology; this has played an important role in guiding the proper design and application of lighting environments. In the past decades, science and technology related to lighting have advanced significantly in the following areas. (1) Technology has transformed lighting with the development of light emitting diodes (LEDs), which are now a practical source for general illumination. The unique properties of LEDs, such as their small size and availability in saturated colors ranging from red, green, and blue to different tones of white, offer tremendous new application possibilities. Because most existing quality measures for such applications are derived from research with and referring to the use of diffuse fluorescent lighting, there has been significant concern with respect to the feasibility of current measures for evaluating indoor lighting with LED lighting systems. (2) Vision and biological sciences have achieved a deepening knowledge of the complex relationship between light and health, adding both opportunities and responsibility to the work of those who design lighting systems, and have heightened public awareness with respect to how lighting affects our lives. Intrinsically photosensitive retinal ganglion cells (ipRGC) send light information via the retinohypothalamic tract (RHT) directly to the suprachiasmatic nucleus (SCN) of the hypothalamus and other targets in the brain; they have given lighting research and applications a brand-new connotation to provide the right light for the right person in the right place using the integration of LED lighting and smart lighting control technology to provide occupants with healthful lighting environments that provide safety, comfort, and human wellbeing. In this paper, on the basis of a systematic review of recent advances in the areas of lighting, and vision and the implications of healthful lighting, the following suggestions concerning research and the implementation of healthful lighting in China are given. (1) The widening application of LED technology and its connotations for healthful lighting, as well as the challenges faced by existing lighting quality measures, need to be studied. A healthful lighting evaluation system needs to be established with improved evaluation criteria for glare, color quality, and temporal light artifacts. In addition, a better understanding of the mechanisms of non-visual effects needs to be acquired in the areas of vision, neurophysiology, and psychology. (2) From the point of view of the dynamic characteristics of its intensity and spectrum, daylight is the optimal light source for healthful lighting. Therefore, the integration of daylighting technology, smart lighting control, and LED lighting will be the most effective method to realize this concept in real applications without resulting in high levels of energy consumption and discomfort associated with a fluctuating and nonuniform daylight distribution. (3) The core connotation of healthful lighting is its human-centric feature. Individuals differ widely in their visual capabilities and needs; this is not considered in current lighting recommendations, which have been developed on the basis of average results, usually for able-bodied young adults. Globally, with the increasing proportion of older people and people with visual impairments, the suitability of lighting recommendations based primarily on research with younger populations is being questioned. For healthful lighting, the development of suitable lighting technologies or design practices to assist diverse populations is necessary for healthful lighting applications.

Effects of lighting on ECG, visual performance and psychology of the elderly

Research has explored the effects of illuminance and correlated color temperature (CCT) of indoor lighting on visual performance, mood and physiological parameters of the elderly. Yet, these investigations did not render a consistent finding on visual and non-visual effects of lighting from a holistic perspective. The present study systemically explored the comprehensive effects of illuminance (300 lx, 500 lx, 750 lx, 1000 lx and 1500 lx) and CCT (3000 K, 5000 K and 6500 K) on electrocardiogram (ECG), visual performance and subjective mood of the elderly. The findings revealed that the ECG indicators of the elderly did not change significantly under most lighting conditions though the heart rate was more sensitive to light than waveform time. In addition, an increase in CCT elicited statistically significant benefits on task performance, however, participants' task performance was not significantly enhanced with the increase of illuminance, and the light of 750 lx seemed to be the most unfavorable for the visual task of the elderly. Furthermore, the participants’ subjective appraisals were inclined to be positive and satisfactory and were not significantly different between different lighting conditions. The results of this study showed that short duration (i.e. 20 min) of light exposure had little effect on the physiological rhythm of the elderly, but it did affect the visual performance and psychological feelings of the elderly. Therefore, in the places where the elderly stay for a short time, the first consideration of lighting design should be to meet the visual and psychological needs of the elderly.

Nonvisual effects of light in development and disease

Nonvisual effects of light in development and disease

Light, entrainment and alertness: A case study in offices

It is well established that light affects both visual and non-visual systems. Laboratory studies have shown that, depending upon the time of exposure, short-wavelength light of sufficient amount and exposure duration will either entrain or disrupt the synchrony between our biological clock and our local position on Earth. Laboratory studies have also shown that light across the entire visible spectrum can enhance alertness, both day and night. Scant attention has been given to testing the effects of light on building occupants’ non-visual responses, and, consequently, lighting specifiers have been offered little guidance on the design and application of lighting for non-visual effects. The present study helps to fill that gap through field-testing of light exposures from a novel luminaire designed to promote entrainment and alertness throughout the day in actual office environments. The data support the inference that light exposures, when properly applied, can promote circadian entrainment and increase alertness.

Non-visual effects of diurnal exposure to an artificial skylight, including nocturnal melatonin suppression

BackgroundRecently, more consideration is being given to the beneficial effects of lighting on the maintenance and promotion of the health and well-being of office occupants in built environments. A new lighting technology using Rayleigh scattering has made it possible to simulate a blue sky. However, to date, no studies have examined the possible beneficial effects of such artificial skylights. The aims of this study were to examine the non-visual effects of artificial skylights and conventional fluorescent lights in a simulated office environment and to clarify the feature effects of the artificial skylights.MethodsParticipants were 10 healthy male adults. Non-visual effects were evaluated based on brain arousal levels (α-wave ratio and contingent negative variation [CNV]), autonomic nervous activity (heart rate variability [HRV]), work performance, and subjective responses during daytime exposure to either an artificial skylight or fluorescent lights, as well as nocturnal melatonin secretion.ResultsSubjective evaluations of both room lighting-related “natural” and “attractive” items and the “connected to nature” item were significantly higher with the skylight than with the fluorescent lights. Cortical arousal levels obtained from the early component of the CNV amplitude were significantly lower with the skylight than with the fluorescent lights, whereas α-wave ratio and work performance were similar between the two light sources. The HRV evaluation showed that sympathetic nerve tone was lower and parasympathetic nerve tone was higher, both significantly, for the skylight than for the fluorescent lights during daytime. Nocturnal melatonin secretion was significantly greater before and during light exposure at night under the daytime skylight than under the fluorescent lights.ConclusionsOur results suggest that artificial skylights have some advantages over conventional fluorescent lights in maintaining ordinary work performance during daytime with less psychological and physiological stress. The findings also suggest that the artificial skylights would enable built environments to maintain long-term comfort and productivity.