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Sensitive physiological indicators for human visual comfort evaluation
Abstract
Three physiological factors (melatonin levels, tear mucus ferning quality and degree of asthenopia) were examined for their relationship to visual comfort. A lighting environment was created where the illuminance, illuminance uniformity and correlated colour temperature could be adjusted. A three-factor and three-level orthogonal experiment with 24 subjects was designed and carried out. The results indicated that the selected environmental factors had different impacts on the physiological factors. With the illuminance increasing, the melatonin level decreased significantly and the tear mucus ferning quality was improved. However, there is no general influence of illuminance uniformity and correlated colour temperature on the physiological parameters, only differential effects among the three levels were found.
... CCT is also an influential factor that affects the visual perception, task performance, mood, and well-being of users; thus, several studies have conducted field lighting simulations considering CCT [8,13,25,35,50,[64][65][66]. For example, Viola et al. [13] conducted field lighting simulations in an office and identified lighting condition with 17000 K improves perceived mood, alertness, and task performance compared to lighting conditions at 4000 K. Hoffmann et al. [35] conducted field lighting simulations by using a survey and measuring sulfatoxymelatonin, which is linked to the circadian rhythm, and found that dynamic lighting conditions with varying CCT and illuminance levels during a day could improve users' subjective mood in an office. ...
... However, as mentioned above, the changes in the illuminance levels in the IVEs did not significantly affect the participants' visual comfort. However, some previous field lighting simulation studies [63,65,66] have reported results inconsistent with these findings. For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. ...
... For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. Similarly, Sun et al. [65] and Viitanen et al. [66] observed that participants indicated improvements in visual comfort as the illuminance increased. We believe that this inconsistency in our results is owed to the visual discomfort and mental workloads caused by using the HMD for IVE lighting simulations. ...
Optimizing space utilization in buildings is necessary to achieve a sustainable built environment. To this end, accurate space utilization prediction, considering the spatial preference of occupants, is required to design well-utilized spaces in architecture, engineering, and construction projects. However, there is no existing method for quantitatively estimating occupants’ spatial preferences during space planning and design phases to optimize post-occupancy space utilization. Thus, in this study, an immersive choice modeling approach (ICMA) was developed to estimate the spatial preferences of occupants by integrating a discrete choice modeling approach with an immersive virtual environment simulation. The ICMA quantitatively estimates the spatial preferences of occupants in three steps: 1) discrete choice experiment design, 2) immersive virtual environment choice simulation creation, and 3) spatial preference modeling. The ICMA was successfully demonstrated by estimating the spatial preferences of 45 participants for an office. The application of an ICMA was then illustrated through a case example, highlighting its ability to predict space utilization in space planning and design phases.
... CCT is also an influential factor that affects the visual perception, task performance, mood, and well-being of users; thus, several studies have conducted field lighting simulations considering CCT [8,13,25,35,50,[64][65][66]. For example, Viola et al. [13] conducted field lighting simulations in an office and identified lighting condition with 17000 K improves perceived mood, alertness, and task performance compared to lighting conditions at 4000 K. Hoffmann et al. [35] conducted field lighting simulations by using a survey and measuring sulfatoxymelatonin, which is linked to the circadian rhythm, and found that dynamic lighting conditions with varying CCT and illuminance levels during a day could improve users' subjective mood in an office. ...
... However, as mentioned above, the changes in the illuminance levels in the IVEs did not significantly affect the participants' visual comfort. However, some previous field lighting simulation studies [63,65,66] have reported results inconsistent with these findings. For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. ...
... For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. Similarly, Sun et al. [65] and Viitanen et al. [66] observed that participants indicated improvements in visual comfort as the illuminance increased. We believe that this inconsistency in our results is owed to the visual discomfort and mental workloads caused by using the HMD for IVE lighting simulations. ...
In recent decades, immersive virtual environments (IVEs) have enabled users to experience various lighting scenarios with a high sense of presence and immersion, thereby having the potential to simulate office lighting design. To realistically experience lighting design cases in IVE lighting simulations, the CCT and illuminance levels should be accurately reproduced. However, there is still a lack of empirical evidence considering these factors. Thus, this study examined whether CCT and illuminance levels could be accurately reflected in IVE lighting simulations by investigating users’ responses to variations in CCT and illuminance levels in IVEs. To this end, we created nine IVE lighting cases and investigated the responses of participants regarding visual perception (comfort, naturalness, dimness, and warmness) and task performance measured through a questionnaire and the Landolt C test. The results indicated that, although using head-mounted displays affected the perception of visual comfort in some respects, the participants showed responses corresponding to the general findings of field lighting simulations of previous studies. In terms of task performance, participants showed improvement as the illuminance increased in IVEs, while there was no specific relationship between CCT and task performance due to the different effects of CCT on visual acuity and contrast sensitivity. The present study empirically identified the potential of IVE lighting simulations considering CCT and illuminance. With further investigations on more diverse office lighting conditions, IVE lighting simulations will help architects design optimal office lighting.
... Lighting has an impact on recipients' physical and mental conditions [4] and so does visual comfort in the workplace which, in turn, has a direct impact on mood [10], [11]. Gradually, it was realised that visual comfort was an important factor informing employees' health and productivity [12]. Potential productivity can be derived from a range of factors including: i) reducing pain due to breathing problems such as asthma and ii) the defeat of 'sick building syndrome' coupled with improved employee performance due to iii) changes in temperature and iv) visual conditions [13]. ...
... In the workplace, the sense of sight is considered the most important, compared to other senses [17]. Visual comfort is the most important thing in realising user satisfaction in office buildings [18] in terms of health and work productivity [12], [19]. Good lighting leads to better performance in terms of: i) speed, ii) fewer errors, iii) fewer accidents, and iv) less absenteeism [20]. ...
... In the case of the daylight factor (DF), the office is recommended to receive a minimum of 2% [23] and the ratio of walls to windows (WWR) is 20% -50% [24]. The illuminance level in the workplace has the greatest impact on employees' visual comfort, followed by the correlated colour temperature (CCT) and the uniformity of the lighting [12]. ...
... Working in environments that are excessively bright or dim can have a negative impact on workers' work efficiency and visual comfort. Unstable illuminance levels can interfere with workers' visual abilities, thereby affecting product quality [27]. illuminance on the indoor work surface is directly influenced by the exterior illuminance, resulting in an unstable illuminance level on the work surface. ...
... Working in environments that are excessively bright or dim can have a negative impact on workers' work efficiency and visual comfort. Unstable illuminance levels can interfere with workers' visual abilities, thereby affecting product quality [27]. ...
T8 LED tubes with adjustable brightness and color temperature are installed in the workshop for workers to adjust their lighting independently. The illuminance of the workers’ working surface is dynamically monitored for one year, and the collected illuminance data are quantitatively analyzed to explore the suitable illuminance threshold and color temperature preference for workers in real scenes. The illuminance value is divided according to time period and season, which provides reference for the development of intelligent buildings. For the three workflows in the post-finishing workshop, the lighting environment was optimized based on the uniformity of illumination, and the optimal height of the lighting arrangement was determined. The optimal luminaire placement height for the bar tacking machine was found to be 1.28 m, for the auxiliary workbench it was 1.02 m, and for the ironing table it was 1.2 m.
... People intend to have a higher heart rate when they are in an integrative environment combined with both higher temperature and noise (Ren et al., 2011). Additionally, individuals' visual sense directly affects their physiological factors (Sun and Lian, 2016). For example, bright space can reduce heart rate and blood pressure (Peng et al., 2022). ...
The Metaverse is a new application of the internet and social form which integrates a myriad of new technologies. It can not only create a parallel space that is closely connected to the real world while highly independent, but also bring the immersive experience of virtual scenarios without delay. The virtual tourism space situations that integrate realistic visual, audio, and temperature sensations can restore the real tourism environment to the greatest extent, and improve tourists’ perception and satisfaction with the experience. The purpose of this experimental lab study is to examine the effects of the virtual tourism audio-visual conditions and environmental temperature on tourists’ thermal sensation and temperature comfort. VR equipment and microclimate simulation technology was applied in a 3 × 2 × 2 experimental design (n = 180), simulating the virtual tourism scenarios. Electrocardiogram devices were also employed to assess participants’ physiological indicators. Study results suggest that: (1) Virtual tourism spatial situations (environmental temperature and audio-visual conditions) significantly affect participants’ thermal sensation and part of the physiological indicators; (2) Virtual tourism spatial situations (environmental temperature and audio-visual conditions) significantly affect participants’ temperature comfort; and (3) Physiological responses (indicators) mediate the effect from tourism spatial situations to temperature comfort. The study mainly contributes to the literature about virtual tourism experience and spatial situations under the concept of the Metaverse, as well as provides theoretical and managerial implications for the development of “immersive” virtual tourism scenarios.
... Numerous studies have shown that a light environment can directly influence work efficiency through visual effects while indirectly affecting people's attention, enthusiasm, and arousal level. Sun et al. [22] found that the illumination on the work plane had the most significant impact on visual comfort, and the CCT of the light ranks second. Ishii et al. [23] found that the task performance of the subjects under high CCT (6200 K) was better than that of normal CCT (5000 K). ...
In this study, we investigated the impact of the lighting environment on psychological perception, physiology, and productivity and then designed lighting control strategies based on the experimental results. The research was conducted in a smart lighting laboratory, and 67 subjects were tested in different illuminances and correlated color temperatures (CCTs). During the experiment, the physiological data of subjects were continuously recorded, while the psychology and productivity results were evaluated by questionnaires and working tests, respectively. The experimental results found that both illuminance and CCT could significantly influence the feeling of comfort and relaxation of the subjects. Warm CCT and higher illuminance (3000 K–590 lux) made subjects feel more comfortable. Productivity reached its maximum value with illuminance above 500 lux and equivalent melanopic lux (EML) higher than 150. The brain-wave and heart-rate changes did not have a close relationship with either illuminance or CCT, but the heart rate slightly increased in the adjustable lighting mode. Regardless of the initial value setting, the subjects preferred intermediate CCT (4200 K) and bright illumination (500 lux) after self-adjustment. Finally, we proposed three comprehensive lighting control strategies based on psychology, productivity, circadian rhythm, and energy-saving.
... Visual comfort is seen as an important factor in satisfying the occupants of a workplace [1] with particular reference to the issues of health, safety and work productivity [2]. The comfort is influenced by [3]: a) the illuminance level [4], b) the contrast and c) the glare [5 -7]. ...
Research on how to optimize natural lighting can recommend ways to save the energy without ignore the occupants’ visual comfort. This paper discusses the feasibility as workplace of the office workspace providing sufficient natural lighting and how the occupants respond to that environment. The research is conducted with computer simulation using DIALux software and field measurement at three different times of day: 8.00, 12.00 and 16.00. The research object is an office room of Magister Teknik Sistem (METSI), Universitas Gadjah Mada, Yogyakarta. It is measured and simulated in two window conditions; (i) without vertical blinds and (ii) with closed vertical blinds. The measurement and simulation show that the highest average of illuminance level is 305 lx and the highest daylight factor is 1.135%. This level is reached at the 12.00 with windows without blinds. The result is below the standard which are 350 lx for illuminance level and 2% for daylight factor. Therefore, it can be concluded that the natural lighting of the research object/ room has failed to meet the requirement needed for an acceptable workplace. Nevertheless, the occupants passively adjust the vertical blinds’ position in order to create their visual comfort. The occupants initiated adaptive activity, such as moving (from their sitting position) to where there is abundant light or turning on the artificial lighting when the room is dark.
... personality type, perceived stress and emotional state Table 9 shows three participants with proneness to stress associated with negative affects (lower scores on the test). On the other hand, the remaining four participants with no 20 Means Figure 6 Mean melatonin secretion (mg) of individual participants in response to the experimental lighting conditions in summer and winter stress proneness show positive affects (higher scores on the test). The intermediate type C of the personality test type A/B shows more individuals without a proneness to stress. ...
Light can impact psychobiological processes in a healthy or harmful way, challenging designers to better understand the resources they are manipulating. The present exploratory study compared two forms of office lighting which differed in correlated colour temperatures and light level. A holistic approach, comprising visual, emotional and biological dimensions, was used to assess the lighting conditions that could favour productivity and well-being by means of the identification of congruent relationships between objective and subjective measurements in response to light stimuli. The former included analyses of melatonin and cortisol, and the latter were psychological instruments for measuring transitory mood, somnolence, and visual comfort. Controlled experiments were run in a laboratory with a repeated measures design, which yielded fifty-six evaluations. Although no extreme ranges of correlated colour temperatures were used in this study, the spectral blue component present in the correlated colour temperature of approximately 4000 K, and also provided by the light-emitting diodes system at a higher light level, could have contributed to render most of the strong effects on the inter and intra correlations among the psychobiological responses. The mediator role of the psychological profile of the individuals was demonstrated by the significant predictive value of the perceived stress measures. References Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, Gerner E, Rollag MD. Action spectrum for melatonin regulation in humans: Evidence for a novel circadian photoreceptor. Journal of Neuroscience 2001; 21: 6405–6412. Lucas RJ, Peirson SN, Berson DM, Brown TM, Cooper HM, Czeisler CA, Figueiro MG, Gamlin PD, Lockley SW, O’Hagan HB, Price LLA, Provencio I, Skene DJ, Brainard GC. Measuring and using light in the melanopsin age. Trends in Neurosciences 2014; 37: 1–9. Rea MS, Figueiro MG. A working threshold for acute nocturnal melatonin suppression from ‘white’ light sources used in architectural applications. Journal of Carcinogenesis and Mutagenesis 2013. DOI: 10.4172/2157-2518- 1000150. Rea MS, Figueiro MG. Light as a circadian stimulus for architectural lighting. Lighting Research and Technology First published 6 December 2016. DOI: 1477153516682368. Rea MS. The lumen seen in a new light: Making distinctions between light, lighting and neuroscience. Lighting Research and Technology 2015; 47: 259–280
... The mean values and standard deviation of three air pollutants, NO 2 , SO 2 and PM 10 , during 90 days before reporting day were calculated based on the original data from SEMC where the abnormal data have been excluded [51,52] . These three air pollutants and the combined objects according to the independent impacts of these pollutants were then classified as four categories by quartiles (25%, 50% and 75%). ...
In order to investigate the relationship between outdoor air pollution and sick building syndrome (SBS) symptoms, the CCHH (China, Children, Home, Health) group in Shanghai conducted a cross-sectional survey on the current incidence of SBS symptoms among residents in five districts of Shanghai during April 2011–April 2012. It also collected the related outdoor air pollutants data from Shanghai environmental monitoring center (SEMC), including nitrogen dioxide (NO2), sulfur dioxide (SO2) and particles with aerodynamic diameter less than 10 µm (PM10). The logistic regression models were used in this paper to study the associations between air pollutants and SBS symptoms. Results were found that the daily mean concentrations of NO2 and SO2 met standard requirement, but that of PM10 exceeded the limit values of the standard in China during this survey. The significant differences were found between the pollutants concentration in urban and suburban area. In addition, the incidences of three categories of SBS symptoms among residents were 79.1% for general symptoms (GS), 65.2% for mucous membrane symptoms (MS) and 35.7% for skin symptoms (SS), respectively. Multiple logistic regression analysis by two case studies illustrated that three outdoor air pollutants, both their concentration quartiles and equal increment, were all associated to and taken as the risk factors for SBS symptoms, for GS ORNO2 = 1.62 (1.18–2.22), MS OR NO2 = 1.58 (1.21–2.06) and SS OR PM10 = 1.21 (1.09–1.35). Furthermore, the new pollutants expressed as the mixtures of their combination were also significantly associated with part of the SBS symptoms. The synthetic air quality indexes of all surveyed residents were calculated as III-level, which represented mild pollution. Therefore, it would be an effective way to decrease the incidence of SBS symptoms in residence to reduce the outdoor air pollution and control the penetration from outdoor to indoor environment.
... personality type, perceived stress and emotional state Table 9 shows three participants with proneness to stress associated with negative affects (lower scores on the test). On the other hand, the remaining four participants with no 20 Means Figure 6 Mean melatonin secretion (mg) of individual participants in response to the experimental lighting conditions in summer and winter stress proneness show positive affects (higher scores on the test). The intermediate type C of the personality test type A/B shows more individuals without a proneness to stress. ...
Light can impact psychobiological processes in a healthy or harmful way, challenging designers to better understand the resources they are manipulating. The present exploratory study compared two forms of office lighting which differed in correlated colour temperatures and light level. A holistic approach, comprising visual, emotional and biological dimensions, was used to assess the lighting conditions that could favour productivity and well-being by means of the identification of congruent relationships between objective and subjective measurements in response to light stimuli. The former included analyses of melatonin and cortisol, and the latter were psychological instruments for measuring transitory mood, somnolence, and visual comfort. Controlled experiments were run in a laboratory with a repeated measures design, which yielded fifty-six evaluations. Although no extreme ranges of correlated colour temperatures were used in this study, the spectral blue component present in the correlated colour temperature of approximately 4000 K, and also provided by the light-emitting diodes system at a higher light level, could have contributed to render most of the strong effects on the inter and intra correlations among the psychobiological responses. The mediator role of the psychological profile of the individuals was demonstrated by the significant predictive value of the perceived stress measures.
This chapter offers a reflection on how comfort is perceived in the Global South, specifically in tropical countries, considering economic and technological constraints. International standards do not fit well within the climatic diversity of the places located in the equatorial zone, such as Colombia. This raises the question of whether tropical climates do not allow comfort, or simply do not provide what others want. The bioclimatic architecture paradigm of the last century assigned comfort the status of goal, but in this climatic and socio-cultural context, an attempt has been made to use it as a work tool. The calculation of the environmental performance of spaces, empirically valued as adequate or inadequate for specific conditions, indirectly provides knowledge about the typical tolerance thresholds of a place.KeywordsEnvironmental comfortBioclimatic architectureTropics
This book describes how comfort, energy and climate change in developing countries and vulnerable sectors of the population relate to buildings.
The building sector is currently facing significant challenges connected to energy consumption, energy poverty and climate change effects. When studied in developing countries and vulnerable sectors of the population, these factors, which are commonplace in the tropics and the southern hemisphere, are interlinked and share a critical component: environmental comfort. Although progress has been made in environmental comfort through research and the development of standards and policies at the international level, in the Global South, where the countries with the highest levels of income inequality are concentrated, environmental comfort has its own characteristics and challenges that prevent a clear understanding from the established vision of the Global North.
This book presents research, theories and techniques related to Thermal comfort, Indoor air quality, Visual comfort, and Acoustic comfort and its relationship with energy use and energy efficiency, seeking to address different barriers to environmental comfort. It shows how to improve the way buildings are designed and operated to promote healthier environmental conditions and more sustainable construction, by presenting studies and reflections carried out in the target geographical area: the Global South. In this way, this book contributes to developing the concept of environmental comfort, visualising how progress has been made in understanding it from a tropical and southern perspective, and posing common challenges.
The book is intended for engineers, architects, and researchers of the built environment who are interested in environmental comfort and its influence on energy consumption, energy poverty, and other related factors in the Global South context. It is also a useful resource for decision-makers and public policy developers concerned with the indoor comfort of buildings. Moreover, the book aims to provide guidance for those in developing countries by gathering existing knowledge in the field for the tropics and southern hemisphere climatic and sociocultural contexts, allowing us to move forward in this subject with actions and proposed solutions that fit our particular needs.
It has been proved that lighting has nonvisual effects on the human body, including changes in heart rate and blood pressure. Heart rate and blood pressure are associated with the autonomic nervous system and can indicate stress level. The present study investigates whether heart rate and blood pressure are influenced by the frequency or duty cycle of pulsed light, together with the duration of lighting. Twelve healthy young subjects were recruited for the investigation. Subjects were exposed to pulsed light of varying frequencies (40 Hz, 100 Hz, 300 Hz) and duty cycles (10%, 50%, 90%). Exposure time was divided into two groups: short-time (20 min) and long-time (3 hours). Heart rate and blood pressure were measured during the experiments. Results showed that after a short lighting period (20 min), heart rate and blood pressure were significantly higher under 40 Hz pulsed than that under stable light, while 100 Hz and 300 Hz had no significant difference. After 3 hours of exposure time, the two indices became higher under 100 Hz (no flicker perceived with eyes) with 10% duty cycle, while 50% and 90% duty cycle showed no significant difference. These findings indicate that pulsed light will cause a deviation of heart rate and blood pressure from that under stable light.
Indoor luminous quality affects occupants’ health a lot, but no mature solution exists to assess the quality. The objective of this paper was to develop a practical fuzzy evaluation model for light environment. Based on previous studies and a series of luminous experiments, illuminance, correlated color temperature and illuminance uniformity were chosen as evaluation indicators and a fuzzy synthetical evaluation model with five grades was developed.
This study examined the effects of lighting with different spectra on humans, as measured by mean arterial pressure, heart rate and visual comfort. Twenty subjects were recruited and tested under 12 different lighting spectra, produced by self-made luminaires respectively. In order to evaluate the shape similarity between the measured spectrum and the solar spectrum, a full-spectrum index E (0–100) was proposed. The higher the value of E, the closer the spectrum is to the full range of daylight. Groups whose E value is above 90 are classified as full-spectrum lighting groups. Subjects were required to maintain a calm mood during the 3-h testing time, and data were recorded every 20 min. Pearson correlation test and independent samples t-test were performed on the mean values. Results showed that heart rate and visual comfort were likely to be influenced by the spectrum. The higher the E is, the lower the average heart rate is and the higher the visual comfort is. Full-spectrum lighting group has a significantly lower heart rate and higher visual comfort than the control group.
The study of the quality of lighting and visual comfort is conditioned to the health and well-being of those who use and enjoy the built spaces. Light is important to the conceptual design of an environment; therefore, many researchers have searched for ways to identify and evaluate visual comfort through different research instruments. One of the most recurrent, the questionnaire, is an instrument of data collection in order to evaluate the preferences and characteristics of a sample. In this context, the objective of this study was to identify, detail and provide greater understanding about the questionnaires that evaluate visual comfort, through a systematic literature review. It was selected a set of seventeen questionnaires and, thus, is intended to analyze the questionnaires under the following aspects: structure; the objective of the research; evaluated environment and main aspects and characteristics of lighting. It was possible to observe that during the systematic review of the literature, most of the researchers found, that deal with the measurement of visual comfort, making it for office environments. In addition, It was found that the aspects preferences and satisfaction; and glare and light distribution are the characteristics more recurring in the questionnaires analyzed. This work contributes to developing research studies that require a questionnaire as part of their evaluation method..
The purpose of this study was to investigate the effect of lighting environment on the work performance. Orthogonal experiments with three-factor and three-level for each factor were designed and carried out in a laboratory aiming to reveal the relationship between lighting illuminance (ILL), uniformity of illuminance (U-ILL), correlated colour temperature (CCT) and workers’ productivity. Twenty-four participants’ work performance was evaluated by subjective questionnaires, objective physiological tests, accompanied with computerized neuro-behavioural tests assessing six kinds of neuro-behavioural functions. Results illustrate that when exposed to high ILL, U-ILL and CCT environment, participants reported highest satisfaction on productivity and attention, while lowest score on stress, difficulty of conducting work and fatigue. The range value and variance analysis from neuro-behavioural tests demonstrated the appropriate level of each factor and the optimal combination. However, they varied with the type of tests illustrating that lighting conditions could influence neuro-behavioural functions differentially. The improvements of perception, learning and memory function of participants were benefited from high ILL, high U-ILL and high/medium CCT. Low ILL, low U-ILL and moderate CCT were appropriate to increase participants’ thinking and executive performance. Moreover, high quality of tear film crystallization was related to higher illuminance. The present study suggests that it is necessary to design personalized illumination environment for particular workplace.
The aim of this article was to assess some of the main lighting software programs habitually used in architecture, subjecting them to a series of trials and analyzing the light distribution obtained in situations with different orientations, dates and geometry. The analysis examines Lightscape 3.2, Desktop Radiance 2.0, Lumen Micro 7.5, Ecotect 5.5 and Dialux 4.4.
Among those concerned with practical matters of office design, demonstrations that the work environment affects employees’ well-being and work behaviors are thought to be important to support client decision making. Veitch, Newsham, Boyce, and Jones developed a conceptual model in which lighting appraisal and visual capabilities predicted aesthetic judgments, mood, and performance. This article extends that model to include measures of work engagement, using experimental data originally reported by Newsham, Veitch, Arsenault, and Duval. Structural equation modeling showed strong fit to a model in which lighting appraisals indirectly influenced work engagement through aesthetic judgments and mood. This evidence that providing a satisfactory work environment can contribute to employee effectiveness merits further study by environmental and organizational psychologists.
A study is presented about the effects of three glazing colour types (blue, neutral, bronze) on daylight quality, arousal and switch-on patterns for electric lights. This study was carried out using a scale model (1:4) of an office room, where subjective evaluations of the luminous conditions were performed by 36 participants (mean age 23.8 years) with their upper bodies immersed in the model. The evaluations were achieved using questionnaires designed to assess five light quality factors: 1) visual comfort; 2) naturality; 3) pleasantness; 4) precision (of details and textures) and 5) light level. Mixed model analyses of the questions revealed significant higher scores for pleasantness (p = 0.003) comfort (p = 0.015) and light level (p = 0.044) for the bronze glazing type compared to the blue and neutral glazing, confirming results of earlier studies. Results from a paired t-test on the Karolinska Sleepiness Scale (KSS) scores indicated that the level of self-reported arousal decreased in presence of the blue glazing. However, the analysis did not reveal significant results regarding switch-on patterns of electric lights. Overall, the study shows that there is a preference for daylight filtered through bronze window glazing and that the glazing colour type may have a significant effect on arousal level of office workers.
The introduction of daylight to reduce electrical lighting energy consumption and to enhance Indoor Environmental Quality is one of the most common claims made for commercial office buildings promoted as “sustainable,” “energy efficient,” “green,” or “high performance.” However, daylit buildings are rarely studied in use to examine the impact of design strategies on visual comfort, or to examine how occupant modifications to the facade may reduce daylighting effectiveness and visual connection to the outdoors. This paper presents key findings from a post-occupancy study of a side-lit open-plan office building located in San Francisco, California. The study examines daylighting performance over daily and seasonal changes in sun and sky conditions in core and perimeter zones of the building. Daylighting performance is assessed through measurements of electrical lighting energy, observations of occupant modifications to the facade, and physical measurements of interior lighting conditions paired with occupant subjective assessments using novel desktop polling station devices. Results show a high frequency of visual discomfort responses at both perimeter and core workspaces and observations reveal a large percentage of facade glazing covered by interior shading devices. Despite the significant reduction in effective visible light transmission, occupants working in the perimeter zones generally considered the levels of available daylight to be sufficient, even when daylight levels were below recommended thresholds for daylight autonomy. Issues related to the daylighting design strategies are discussed in regard to improving the performance of future daylit buildings and refining daylighting design criteria.
Depending on what is in the view, looking out the window may provide numerous opportunities for restoration. Unlike other restorative opportunities, however, window viewing is more frequent and for brief moments at a time. The setting is also experienced from afar rather than while being in it. A study conducted at six low-rise apartment communities, using a survey with both verbal and visual material, provides considerable support for the premise that having natural elements or settings in the view from the window contributes substantially to residents’ satisfaction with their neighborhood and with diverse aspects of their sense of well-being. Views of built elements, by contrast, affected satisfaction but not well-being. Views of the sky and weather did not have a substantial effect on either outcome. The potential of nature content in the view from home to contribute so significantly to satisfaction and well-being suggests clear action mandates.
The minimum size of subjects required for the research on human health, thermal comfort and productivity is a frequently asked question. In this paper the idea of power analysis, which helps to determine required sample size as well as to interpret research results, is introduced in order to promote good practice of power analysis in the context of human and building environment relationship research. How to calculate effect size from published article or experimental data is presented with plenty of examples. The effect sizes of several physiological and psychological measurements indicating the effect of indoor environment quality on human health, thermal comfort and productivity are presented, which could be worked as references when researchers planning their own studies. How to determine required sample size when planning a study and how to interpret the research results with power analysis are also illustrated step by step with samples. Finally how to make decisions when evaluating the study results is summarized. It is expected that these examples and the summary could help researchers to better apply power analysis in indoor environment quality (IEQ) studies. Some statistical terms used in this paper, such as power analysis, effect size, and t-test, etc., are explained in detail in the Appendix.
Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task–ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18–30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (−0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.
The purpose of this paper is to promote statistical power analysis in the behavioral sciences by introducing the easy to use GPower software. GPower is a free general power analysis program available in two essentially equivalent versions, one designed for Macintosh OS/OS X and the other for MS-DOS/Windows platforms. Psychological research examples are presented to illustrate the various features of the GPower software. In particular, a priori, post-hoc, and compromise power analyses for t-tests, F-tests, and chi-2-tests will be demonstrated. For all examples, the underlying statistical concepts as well as the implementation in GPower will be described.
In order to study resonance phenomena in the EEG response to flickering light, 10 subjects were exposed to intermittent photic stimulation with the frequency of flashes linearly changing from 1 to 15 Hz and vice versa. Spectral analysis of occipital electrical activity revealed the occurrence of peaks of spectral density in those frequency components which coincide with the frequency of flashes. Such resonance peaks were observed at individually specific frequencies of stimulation. To assess the stability of the characteristics of the resonance phenomena, a repeated trial with 4-fold higher rate of changing the flash frequency was performed 3 months later. In a repeated trial the resonance phenomena were less pronounced, but were registered at the same frequencies as in the initial trial, showing significant test-retest reliability. The data obtained are interpreted in terms of provoking the activity of multiple brain oscillators having a narrow tuning to individually specific frequencies of photic stimulation by flickering light with the changing frequency of flashes.
The endogenous circadian rhythm of melatonin in humans provides information regarding the resetting response of the human circadian timing system to changes in the light-dark (LD) cycle. Alterations in the LD cycle have both acute and chronic effects on the observed melatonin rhythm. Investigations to date have firmly established that the melatonin rhythm can be reentrained following an inversion of the LD cycle. Exposure to bright light and darkness given over a series of days can rapidly induce large-magnitude phase shifts of the melatonin rhythm. Even single pulses of bright light can shift the timing of the melatonin rhythm. Recent data have demonstrated that lower light intensities than originally believed are capable of resetting the melatonin rhythm and that stimulation of photopically sensitive photoreceptors (i.e., cones) is sufficient to reset the endogenous circadian melatonin rhythm. In addition to phase resetting, exposure to light of critical timing, strength, and duration can attenuate the amplitude of the endogenous circadian rhythm of melatonin. Measurement of melatonin throughout resetting trials provides a dynamic view of the resetting response of the human circadian pacemaker to light. Future studies of the melatonin rhythm in humans may further characterize the resetting response of the human circadian timing system to light.
The photopigment in the human eye that transduces light for circadian and neuroendocrine regulation, is unknown. The aim of this study was to establish an action spectrum for light-induced melatonin suppression that could help elucidate the ocular photoreceptor system for regulating the human pineal gland. Subjects (37 females, 35 males, mean age of 24.5 +/- 0.3 years) were healthy and had normal color vision. Full-field, monochromatic light exposures took place between 2:00 and 3:30 A.M. while subjects' pupils were dilated. Blood samples collected before and after light exposures were quantified for melatonin. Each subject was tested with at least seven different irradiances of one wavelength with a minimum of 1 week between each nighttime exposure. Nighttime melatonin suppression tests (n = 627) were completed with wavelengths from 420 to 600 nm. The data were fit to eight univariant, sigmoidal fluence-response curves (R(2) = 0.81-0.95). The action spectrum constructed from these data fit an opsin template (R(2) = 0.91), which identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cell photopigments for vision. The data also suggest that this new photopigment is retinaldehyde based. These findings suggest that there is a novel opsin photopigment in the human eye that mediates circadian photoreception.
This paper presents an assessment of the air quality for the principal cities in developed and developing countries. Part of the vast and widely dispersed information on air quality that is available at this time on the Internet was compiled, thus making possible a comprehensive evaluation of the tendencies that emerged at the end of the 20th century. Likewise, these values are compared to the air quality thresholds recommended by two international organizations: guideline levels of the World Health Organization (WHO) and limit values of the European Union (EU), in order to determine air quality concentration levels in large cities around the world. The current situation of air quality worldwide indicates that SO(2) maintains a downward tendency throughout the world, with the exception of some Central American and Asian cities. NO(2) maintains levels very close to the WHO guideline value around the world. For particulate matter, it is a major problem in almost all of Asia, exceeding 300 microg/m(3) in many cities. Ozone shows average values that exceed the selected guideline values in all of the analyses demonstrating that it is a global problem. In general, the worldwide trend is to a reduction in the concentrations of pollutants because of the increasingly strong restrictions which local governments and international organizations impose. However, in poor countries and those with low average incomes, concentrations of air pollutants remain high and the trend will be the elevation of their ground levels as they develop, making the problem even worse.
Estimates of statistical power are widely used in applied research for purposes such as sample size calculations. This paper reviews the benefits of power and sample size estimation and considers several problems with the use of power calculations in applied research that result from misunderstandings or misapplications of statistical power. These problems include the use of retrospective power calculations and standardized measures of effect size. Methods of increasing the power of proposed research that do not involve merely increasing sample size (such as reduction in measurement error, increasing 'dose' of the independent variable and optimizing the design) are noted. It is concluded that applied researchers should consider a broader range of factors (other than sample size) that influence statistical power, and that the use of standardized measures of effect size should be avoided (except as intermediate stages in prospective power or sample size calculations).
The mammalian retina contains both visual and circadian photoreceptors. In humans, nocturnal stimulation of the latter receptors leads to melatonin suppression, which might cause reduced nighttime sleepiness. Melatonin suppression is maximal when the nasal part of the retina is illuminated. Whether circadian phase shifting in humans is due to the same photoreceptors is not known. The authors explore whether phase shifts and melatonin suppression depend on the same retinal area. Twelve healthy subjects participated in a within-subjects design and received all of 3 light conditions—1) 10 lux of dim light on the whole retina, 2) 100 lux of ocular light on the nasal part of the retina, and 3) 100 lux of ocular light on the temporal part of the retina—on separate nights in random order. In all 3 conditions, pupils were dilated before and during light exposure. The protocol consisted of an adaptation night followed by a 23-h period of sustained wakefulness, during which a 4-h light pulse was presented at a time when maximal phase delays were expected. Nasal illumination resulted in an immediate suppression of melatonin but had no effect on subjective sleepiness or core body temperature (CBT). Nasal illumination delayed the subsequent melatonin rhythm by 78 min, which is significantly (p= 0.016) more than the delay drift in the dim-light condition (38 min), but had no detectable phase-shifting effect on the CBT rhythm. Temporal illumination suppressed melatonin less than the nasal illumination and had no effect on subjective sleepiness and CBT. Temporal illumination delayed neither the melatonin rhythm nor the CBT rhythm. The data show that the suppression of melatonin does not necessarily result in a reduction of subjective sleepiness and an elevation ofCBT. In addition, 100 lux of bright white light is strong enough to affect the photoreceptors responsible for the suppression of melatonin but not strong enough to have a significant effect on sleepiness and CBT. This may be due to the larger variability of the latter variables.
In order to determine the effect of different light source’s spectrum to a subjects’ visual performance, this experiment examined three fluorescent lamps with a colour temperature of 2700K, 4000K and 6500K and an incandescent lamp. The results were compared to the average recognition rate a “reference person” from different light sources. Experimental results show significant differences in the recognition rate from different optical spectrum light source and recognition rate value. We determined the best combination of ambient and chalkboard light source and propose avoiding combination for classroom lighting that is clearly inferior. This article provides selection reference for optimal classroom ambient and blackboard lighting. In recent years, the study of psychological and physiological effect of light has become one of the most important field in lighting research[1]. Studies has shown that different light spectrum could affect human circadian rhythm, body temperature and alertness, which directly affecting work efficiency and health[2]. The effects by classroom light spectrum on efficiency and health cannot be ignored, as the students are exposed to one particular lighting environment for extended periods of time. Through a systematic survey of classroom lighting in several universities in Chongqing and Chengdu, T5 fluorescent of high colour temperature about 6500K was the predominant choice for classroom general lighting as well as blackboard lighting. Many students complained that they tired easily at this colour temperature. In another study on classroom light source[3] students’ preference for colour temperature is not fixed but varies according to classroom’s function and illuminance level. It was insufficient to choose colour temperature of classroom lighting based on the results of the above questionnaire. We therefore chose and compared T5 fluorescent lamps of 2700K, 4000K and 6500K colour temperature on the visual performance and their effects on study efficiency, asthenopia and physiological rhythm. Due to space limitations this article only discusses the contrast experiment of visual performance.
This study examines the way people choose to use individual control of lighting, the effect of having such control on the illuminance selected for different activities and the performance of those activities and how people feel about having such control. The experiment took place in three small, windowless, private offices, one lit to a maximum of 1240 lx, another to a maximum of 680 lx, both these offices having a handheld dimming system. The third office was lit to a fixed illuminance of 490 lx. Eighteen subjects worked for one eight-hour day in each of the offices. During the day they carried out an alphanumeric verification task in forms which were visually difficult and visually easy, on paper and on a computer, as well as doing some casual reading. The subjects in the offices equipped with individual lighting control could use the control whenever they liked. The data collected showed that the subjects did use the individual lighting control to adjust the illuminance for different tasks, but there were wide differences between individuals. Use of the lighting controls saved energy. The ability to dim the lighting was considered highly desirable and made the tasks seem less difficult. However, the ability to control the lighting did not put the subjects in a more positive mood, did not make them more alert, and did not affect the performance on the task.
In this study, the impact of two different types of window glazing using two identical rooms was studied. In one experiment both rooms were furnished as an office, in another experiment as a bedroom. The only other difference between the two rooms was the glazing of the window. In one room a standard three-pane window (2+1) with 4 mm clear glass was used, in the other a super-insulated four-pane window (3+1) with two silver-based low-emittance coatings. The results showed that people were clearly able to distinguish between the two windows. The room with the four-pane window felt more enclosed, and the daylight felt less strong and clear. The four-pane window also affected colour perception, making the colours of the room and of the view look more subdued or more drab. Spectral measurements revealed that the four-pane window transmitted a relatively higher percentage of the green part of the spectrum. The results agree with what might be expected given the lower transmittance and different spectral distribution of the four-pane window. It is questioned how far one should go in reducing the daylight transmittance of windows.
A pilot study for investigating the effect of six coated glazing materials on visual perception of the interior and of the view out in scaled rooms is presented. The study, which involved 18 subjects, is carried out in Hørsholm (Denmark, lat. 55.4°N), under overcast skies and a north orientation. The methodology involves subjective ratings using a questionnaire and seven grade bipolar scales. The results of the statistical analysis (ANOVA) show that despite significant amplitude in daylight transmittance (50%—79%), the glazing type did not have any statistically significant effect on the perception of the sharpness of shadows in the room. It is also found that higher transmittance glazing (77%—79%) resulted in views that are more glaring compared with the views obtained with the other glazing types. In terms of light level, the reference glazing (which contained an iron-free pane) results in statistically significant differences in the ratings (brighter room) compared with the ratings from all glazing types, including glazing types of similar transmittance. Finally, it is found that higher transmittance glazing types result in more positive ratings for factors, such as naturalness, beauty, and pleasantness and sharpness.
Discomfort glare from daylight is a common problem in many office environments. It has been the subject of a significant body of research and many attempts have been made to develop reliable assessment and prediction models to address this problem. This paper reviews and discusses the advantages and limitations of using existing glare indices for daylighting conditions. It concludes that available assessment and prediction methods are of limited practical use in daylit situations and currently have no provision for integrated systems that combine daylighting and electric lighting. The paper also presents selected findings from a case study of daylit office environments which identify a number of important design considerations. On the basis of the discussion and the findings from the case study, additional research needs are identified to overcome current limitations. In the meantime, until results from such research are available and can be practically applied, this paper suggests ways to better integrate computer workstations in daylit offices.
Lighting control integrated with daylighting is recognised as an important and useful strategy in energy-efficient building designs and operations. Prediction of the internal daylight levels is a key stage in daylighting designs. With the advances in computer technology, the computation of daylight illuminances can be conducted via lighting simulation program. This paper presents a study of the daylight coefficient (DC) approach using RADIANCE lighting software in simulating the indoor daylight illuminance of a corridor. The interior daylight illuminance data measured in the corridor were compared with the simulated results based on the computer software. It was found that the DC approach could give satisfactory results especially for the sun-shaded surface and sun-facing surface receiving a large amount of direct sunlight. Further, the daylight illuminance detected by the photosensor was also simulated in conjunction with measured daylight illuminance, dimming ratio and electric lighting power to predict the lighting energy savings. The findings suggested that the measured and predicted data showed a good agreement when large electric lighting savings resulted. The probable reasons causing the discrepancies were discussed.
Using daylight as primary light source has been widely recognized as an important strategy to reduce building energy demand and enhance indoor environment quality. However, to design and operate a building to make full use of daylight, which is a dynamic light source, to meet diverse occupant needs remains a challenge. This paper reports a post-occupancy study of the visual environment in a laboratory building on a university campus, and puts a spotlight on the building occupants as it examines the effectiveness of the daylighting design and systems integration in creating a visual environment to support occupant comfort and satisfaction while reducing artificial lighting demand. Results show generally high satisfaction with daylit work environment and positive effect of the horizontal shading strategy. Issues about the integration between daylighting and electric lighting systems and level of occupant control are identified and discussed for improving the effectiveness of daylighting and enhancing the quality of the visual environment in the building of study. A multiple-tool methodology is developed and tested, which included occupant surveys, interviews, illuminance measurements, continuous data loggers, fisheye-lens camera and glare-identifying software, and documentation of spatial settings, systems features, and user behavior.
Purpose:
To investigate the effect of exposure to a low relative humidity (RH) environment on tear film physiology.
Method:
A controlled environment chamber was used to create 2 different environmental conditions. Ambient temperature was constant in both conditions (21°C) while the RH was set at 40% at the normal condition and at 5% in the desiccating environment. Tear evaporation, noninvasive tear break-up time, lipid layer thickness (LLT), osmolarity, ocular comfort, tear production, and ocular surface temperature were assessed in normal humidity and over a period of 60 minutes in the dry environment.
Results:
There was significant change in tear evaporation rate (P = 0.00), noninvasive tear break-up time (P = 0.00), LLT (P = 0.00), ocular comfort (P = 0.00), and tear production (P = 0.01) after exposure to the desiccating environment. No significant differences were observed between normal and dry environmental conditions in tear osmolarity (P = 0.09) and ocular surface temperature (P = 0.20).
Conclusions:
Evaporation rate, tear LLT, ocular comfort, tear stability, and production were adversely affected by low RH. The tear film parameters observed after exposure to a desiccating environment for 1 hour were similar to those of the dry eye patient. Therefore, to avoid tear film disruption and possible ocular surface damage, the environmental conditions of dry locations need to be improved or the tear film should be protected against adverse environmental conditions.
Museums have the most complicated lighting criteria of common building types. A stable lighting environment for visitors and artworks should be guaranteed within the exhibition areas of museums. This paper presents a challenge to the application of daylighting simulation integrated into the architectural design process (DSADP). The scale model measurements and computer simulations were carried out to verify the computer program RADIANCE. A comparison between the measurement and simulation results showed that there was considerable relative error at measurement points. Therefore, a correction factor (CF) and corrected simulation (CS) were recalculated to correct the simulation results. The Seoul Museum of Art (SMOA) was selected to make an application of DSADP. The monitor and sawtooth-shaped toplights were chosen as attractive alternatives for the existing skylight of SMOA. The application of DSADP was carried out by changing the light transmission efficiency and opening size of the toplights. The RADIANCE results showed that computer simulation models can accurately represent the lighting environment under clear sky conditions, and more importantly, they can be used to propose an alternative toplight for SMOA. Therefore, the research results showed that DSADP technology would be very useful during the schematic design stage of the architectural design process. The findings of this research also suggested that there are large differences between the real sky conditions for scale model measurements and the CIE sky conditions for computer simulations. More studies are required to reduce the differences between real and simulated sky conditions.
Visual requirements are high when sorting mail. The purpose of this visual ergonomics intervention study was to evaluate the visual environment in mail sorting facilities and to explore opportunities for improving the work situation by reducing visual strain, improving the visual work environment and reducing mail sorting time. Twenty-seven postmen/women participated in a pre-intervention study, which included questionnaires on their experiences of light, visual ergonomics, health, and musculoskeletal symptoms. Measurements of lighting conditions and productivity were also performed along with eye examinations of the postmen/women. The results from the pre-intervention study showed that the postmen/women who suffered from eyestrain had a higher prevalence of musculoskeletal disorders (MSD) and sorted slower, than those without eyestrain. Illuminance and illuminance uniformity improved as a result of the intervention. The two post-intervention follow-ups showed a higher prevalence of MSD among the postmen/women with eyestrain than among those without. The previous differences in sorting time for employees with and without eyestrain disappeared. After the intervention, the postmen/women felt better in general, experienced less work induced stress, and considered that the total general lighting had improved. The most pronounced decreases in eyestrain, MSD, and mail sorting time were seen among the younger participants of the group.
The objective of this work is to investigate the accuracy of the Adeline lighting software in simulating the illuminance distribution from daylighting and the electrical lighting consumption of an existing atrium building. The case study is an enclosed atrium space equipped with an automatic on/off lighting control system and roofed by a skylight made of several.-lazing systems. Field monitoring of the atrium space was conducted during summer and winter and included measurements of horizontal indoor and outdoor illuminance, solar radiation and electrical lighting system time-of-use. The computer simulation included the creation of one simple and one complex computer model used to simulate the daylighting performance of the atrium space. The software accuracy was evaluated based on comparisons between the predicted and the on-site measured illuminance distribution and lighting energy consumption.
This paper presents findings from a web-based survey on the current use of daylight simulations in building design. The survey was administered from December 2nd 2003 to January 19th 2004. One hundred and eighty five individuals from 27 countries completed the survey. The majority of respondents worked in Canada (20%), the United States (20%), and Germany (12%). Most participants were recruited through building simulation mailing lists. Their self-reported professions ranged from energy consultants and engineers (38%) to architects and lighting designers (31%) as well as researchers (23%). They worked predominantly on large and small offices and schools. Ce document présente les conclusions d'une enquête Web sur l'utilisation actuelle de lumière du jour simulée dans la conception des bâtiments. L'enquête a été menée du 2 décembre 2003 au 19 janvier 2004 auprès de 185 personnes dans 27 pays. La majorité des participants travaillait au Canada (20 %), aux États-Unis (20 %) et en Allemagne (12 %). La plupart des participants ont été sollicités par l'intermédiaire de listes distribution touchant la simulation dans les bâtiments. Ils ont déclaré exercer des professions dans les domaines de l'énergie et de l'ingénierie (38 %), de l'architecture et de la conception d'éclairage (31 %) et de la recherche (23 %). Ils travaillaient principalement dans des bureaux et des écoles de dimensions diverses. RES
The integration of daylighting and electric lighting systems within buildings (also designated by "Green lighting") is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users' visual comfort and performance, a large variety of novel daylighting systems and components having been developed during the last years. In order to demonstrate this, an anidolic daylighting system combined with several electric lighting fixtures was set-up in an office room of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Three different electric lighting modes, involving recessed luminaries (direct lighting), floor lamps (indirect lighting) and desk lamps (task lighting), were considered for that purpose.
Melatonin, acting through melatonin receptors, is involved in numerous physiological processes including circadian entrainment, blood pressure regulation, oncogenesis, retinal physiology, seasonal reproduction, ovarian physiology, immune function and most recently in inducing osteoblast differentiation. Moreover, melatonin was proved to be a potent-free radical scavenger and a broad-spectrum antioxidant. More research is required into the effects of therapeutically modulating the melatoninergic system on circadian haemodynamics and rhythm under varying physiopathological conditions and the possible impact on morbidity and mortality in humans.