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Nowadays, no current index can properly explain the high variability existing between individuals’ discomfort glare perception. The mechanism behind the discomfort glare phenomenon is not well understood as some of the factors influencing this phenomenon are still unknown. A large literature review has shown that in addition to the physical quantities currently used in discomfort glare indices, other variables such as contextual, physiological, or even psychological factors, could influence the degree of perceived discomfort glare. The aim of this research project is therefore to determine which factors, whether physiological, psychological, contextual or physical, have a real and significant influence on discomfort glare perception in daylighting. Subsequently, these factors can be compiled in a new discomfort glare model or included in the Daylight Glare Probability, which is the most accurate index at present. During the first stage of the project, potential factors were identified thanks to a large literature study. Every factor having at least been the object of an experiment as a potential element influencing discomfort glare perception has been reviewed. Its influence was classified as either certain, probable, improbable, uncertain or nonexistent. The second stage consists in collecting a large dataset of objective and subjective discomfort glare evaluations through a field experiment in offices using daylighting. The office occupants answer a questionnaire to assess various factors, such as their age, self-assessed glare sensitivity or color of the eyes and to evaluate discomfort glare from daylight in their office. In the meantime, luminance and illuminance measurements as well as HDR images (fig. 1) are collected. Since this research project focuses on the influence of culture on discomfort glare perception, this experiment will be conducted in Chile, Belgium and Japan. These countries have been chosen considering the climate and cultural diversity requirements and because of the local presence of competent teams in the field of daylighting. In total, a dataset of around two hundred investigated offices should be achieved. The last stage of the project involves comparisons between the gathered objective and subjective discomfort glare evaluations through statistical analyses. These analyses are aimed at highlighting factors having an influence on discomfort glare perception. The expected result of this research project is a more accurate and universal discomfort glare evaluation model for daylighting, including validated physiological, psychological or contextual factors. A better understanding of the discomfort glare mechanism should also be achieved.

The mechanism behind the discomfort glare phenomenon, the kind of glare provoking an irritating or distracting effect, is not well understood. Since some of the factors influencing this phenomenon are still unknown, no current indices can properly explain the high variability existing between individuals' discomfort glare perception. A list of potential factors influencing the degree of perceived discomfort glare in daylighting has been established from existing literature. In addition to the physical quantities commonly used in glare indices, other variables, whether psychological, physiological, related to light or to the context, could influence the degree of perceived discomfort glare. (C) 2017 The Authors. Published by Elsevier Ltd.

A gaze-driven methodology for discomfort glare was developed and applied for glare evaluation. A series of user assessments were performed in an office-like test laboratory under various lighting conditions. The participants’ gaze responses were recorded by means of mobile eye tracking while monitoring photometric quantities relevant to visual comfort using HDR luminance imaging. The integration of the luminance images coupled with eye-tracking methods enabled us to use gaze-centred luminance distribution to have an accurate estimate of the light received at the eye. Using a novel gaze-driven approach, a unique database was created as a basis to investigate the gaze direction dependencies of visual comfort. Here we compare the proposed gaze-driven approach with two other approaches based on fixed-gaze assumptions: gaze fixating on the task area, and gaze shifted 45 ° towards the window area. The results show that there is a significant difference between luminance distributions driven by gaze and those based on fixed-gaze assumptions, indicating a potentially important impact on glare assessment results as well.

Measuring gaze allocation during scene perception typically faces a dilemma: full control over the stimulus requires comparably constrained scenarios, while realistic tasks leave the visual input hard to control. We propose to capture the full (4pi) light-field of an oce space, while participants perform typical oce tasks. Using a wearable eye-tracking device ("EyeSeeCam"), gaze, head and body orientation are measured along with subjective well-being and performance. In the present study, 52 participants performed four oce tasks ("input", "reflection", "output", "interaction"), each with three dierent tools (phone, computer, paper) under varying lighting conditions and outside views. We found that eye and head were fundamentally differently affected by view and that this dependence was modulated by task and tool, unless participants' task was related to reading. Importantly, for some tasks head movements rather than eye movements dominated gaze allocation. Since head and body movements frequently remain unaddressed in eye-tracking studies, our data highlight the importance of unconstrained settings. Beyond assessing the interaction between top-down (task-related) and bottom-up (stimulus-related) factors for deploying gaze and attention under real-world conditions, such data are inevitable for realistic models of optimal workplace lighting and thus for the well-being of an occupant's workplace.

Despite numerous efforts in developing glare indices through human assessment studies, predicting visual comfort in indoor environments still poses important challenges in design. A major limitation in discomfort glare indices is that they all ignore its dependencies on view direction. In this study we adopted eye-tracking methods in a series of human assessment experiments in order to record actual visual response when experiencing discomfort glare. We set up an experiment where the view directions distributions were monitored as the participants were working in a side-lit office with three different task-supports - monitor, paper and phone - on a standardized office task sequence. The participants were allocated randomly to two groups where they were exposed to two different views from the window. The results show that the “view outside the window” is the main determinant of view direction bias whenever the participant is not focused on any cognitive or visual office task procedure.

Discomfort glare metrics typically consider at least one of the two effects of discomfort glare-saturation and contrast-in their equation. The former occurs when there is an excessively bright glare source in the field of view, while the latter occurs when there is a high luminance ratio between the glare source and the adaptation level of the eye. We hypothesize that the contrast effect may dominate in low-light scenarios such as those commonly found in open-plan offices. Thus, we designed and carried out a user study in controlled laboratory conditions with 63 participants with a total of 252 scenes to investigate discomfort glare evaluations in dim daylight office environments with low adaptation levels. Our preliminary findings support our hypothesis that contrast-driven metrics predict glare responses in a more reliable way than hybrid metrics at low adaptation levels where the contrast effect dominates, which underlines the need for refining glare metrics in low brightness conditions.

In a context where lighting standards are developed based on glare indices, no study has ever investigated that these indices could be used analogously for subjects having different cultures and living in different climates. The wide variability existing between individuals’ discomfort glare perceptions suggests, however, that some of the factors influencing discomfort glare perception are still unknown, and culture might be one of them. This paper aims to determine the existence of differences between the discomfort glare perceptions of Belgians and Chileans. A field study was conducted in Chile and Belgium, for which a total of 288 measures of the lighting environments and subjective glare assessments were collected. Statistical analyses of the Belgian and Chilean datasets showed that Chileans perceive discomfort glare differently than Belgians. It is therefore hypothesised that existing discomfort glare indices might not be suited for Chilean subjects accustomed to a different type of lighting environment.

Discomfort glare is a major challenge for the design of workplaces. The existing metrics for discomfort glare prediction share the limitation that they do not take gaze direction into account. In order to overcome this limitation, we developed a ‘gaze-driven’ method for discomfort glare assessment. We conducted a series of experiments under simulated office conditions and recorded the participants’ gaze using mobile eye tracking and the luminance distributions using high dynamic range imaging methods. The two methods were then integrated in order to derive ‘gaze-centred’ luminance measurements in the field of view. The existing ‘fixed-gaze’ and the newly developed ‘gaze-driven’ measurement methods are compared. Our results show that there is a significant difference between the two methods. In this paper the procedure for integrating the recorded luminance images with the recorded gaze dynamics for obtaining gaze-centred luminance data is described. This gaze-centred luminance data will be compared to the subjective assessment of glare in Part 2 of this study.

This paper presents the results of an experimental study that aims to provide objective insights as to how luminance distribution in an office setting modulates our view direction (VD) in a daylit workspace while performing office tasks. Using the office-like test facility at Fraunhofer ISE (Freiburg, Germany) to create a range of controlled daylighting conditions, and a wearable mobile eye-tracker to measure eye and head orientation, we assessed VD distributions for subjects performing a standardized sequence of typical office tasks relative to two different daylight conditions: low contrast condition with no direct sunlight as compared to high contrast condition with direct sunlight coming into the room. Our results show that while the participants look more outside the window during a non-cognitive and non-visual office task, this effect is lower under the high contrast lighting conditions. Moreover, the focus of the VDs is on the task area when the participants are performing a task involving visual and cognitive activities.

Existing methods for glare-free daylighting design rely on analyses of physically based lighting simulations employing tools such as Radiance. The rendered image is an accumulation of luminance values from a fixed point of view, which creates a basis for luminance-based metric analysis such as discomfort glare models. A major challenge using luminance images for glare prediction analysis lies in the image processing steps for deriving different parameters of the predictive discomfort glare metrics. One of these challenges is to define and identify glary pixels and zones in the image. The glare source detection algorithms adopted in evaluation tools like evalglare, search for pixels of luminance value that are x-times larger (we call it threshold multiplier in the following) than the average luminance of a pre-defined zone, e.g. the monitor screen. As a second step, the potential glare pixels detected within a search radius (also predefined) are considered and evaluated as one glare source. The implemented default value of a threshold-multiplier and the search radius are decided intuitively and so far no validation has been made on their accuracy. The objective of the present study is to establish a sensitivity analysis on the threshold and search radius parameters. In two series of experiments we took luminance images very 30 second under different lighting conditions and with different façade systems. We also gathered the participants’ subjective assessments of the glare conditions using a Likert scale. Thereafter, we processed the images using 15 different combinations for the threshold multiplier and search radius (threshold multiplier with 5 and search radius with 3 treatment levels). The preliminary results show that there is a significant effect of threshold on all lighting conditions and an effect of search radius on lighting conditions with shading systems. But the results also show, that the choice of the ”right” detection parameters underlies also some effects, which cannot be explained so far. The consequence of this is, that further investigations are needed and as long as no clear rule exist to choose ”right” detection parameters the user of glare evaluation tools has to check the detected glare sources for each investigated situation.

For the application of discomfort glare metrics, a categorisation is used, dividing the metric scale into categories of perception. These categories are separated by borderline values, or so-called cut-off values. Recent literature shows that these cut-off values are lower when they are derived from field study data than those derived from laboratory study data. To investigate this further, the data from one field study and two laboratory studies was used to derive and compare cut-off values corresponding to three borderlines. The results show that the field study cut-off values were systematically lower than the laboratory study ones, implying that discomfort glare is reported at lower stimulus magnitudes in the field. Although further research is required on that topic, several hypotheses are discussed in order to explain the gap between cut-off values derived from field data and cut-off values derived from laboratory data. Recommendations for future studies are also provided.

Using a newly developed gaze-driven methodology for discomfort glare assessments, we studied gaze behaviour in different glare conditions. The study was done in a series of experiments where gaze behaviour of the participants were recorded using eye-tracking techniques and the daylight dynamics were measured using high dynamic range (HDR) imaging techniques. In these experiments 5 daylit and one artificial lighting condition were considered to further our understanding of gaze behaviour in relation to light. Here we present the findings on how gaze behaves in different lighting conditions in relation to glare and task.

Access to daylight and views out are usually recognized as beneficial to occupant comfort at the workplace. Simultaneously, discomfort glare due to direct sunlight is a known source of occupant dissatisfaction. Shading fabrics with low openness factor have been identified as capable of mitigating this source of discomfort. Yet, as these fabrics tend to be dense, views out and illuminance can be limited. Our objective is to evaluate the effect of shading control when it comes to the visual comfort reported by occupants interacting with such blinds. We first exposed participants to a space with the shading fabric down and, in a second session, allowed them to freely position the blind. Our usable sample included 24 participants, and the sun was visible through the blinds within their field of view.Three quarters of the participants raised the blinds in the second session primarily to increase the light levels and have better view out. Glare assessments showed that despite the opening of the blinds –and thus the significant increase in illuminance–, perceived discomfort glare did not increase. This result was in line with the Daylight Glare Probability metric, whose contrast term is able to counteract for the increase in saturation.

The spectral sensitivity of the average human eye in photopic conditions is represented by the photopic luminosity function V (λ). The CIE has established the photopic luminosity functions for the 2o and 10o visual fields for a standard observer applicable for foveal and para-foveal light sources, respectively. These functions differ in short wavelength region where V10° (λ) has higher sensitivity. However, V10°-(λ) function is not implemented in any of the discomfort glare metrics even though, for most glare scenarios, the glare source is located further than 2o from the fovea. This can result in an underestimation of the short wavelength contribution of the glare sources’ spectra, and, a fortiori, in the blue-colored light sources. In this paper, we aim to determine the impact of replacing V2° (λ) with V10°-(λ) in the daylight discomfort glare metrics for scenarios where the visible sun disk lies very much outside the 2° zone and acts as a glare source through blue-tinted and color-neutral tinted low transmittance glazing. We compare three types of colored glazed façade: color-neutral glazing, blue-tinted electrochromic (EC) glazing and an extreme case of saturated blue-tinted glazing. We found that the difference in derived glare source luminance and discomfort glare metrics is statistically significant only for the saturated blue glazing with an average 70% increase in luminance and 20% increase in DGP (i.e. one category higher discomfort) and 9% increase in CGI, when using V10° (λ). We conclude that the impact of replacing V2° (λ) with V10°-(λ) is negligible for standard EC or color-neutral glazing types in commercial buildings. However, specific cases of saturated blue light sources that peaks at 450nm are more accurately quantified by V10° (λ), that produces higher values of glare metrics.

Avoiding discomfort glare is one of the critical aspects of maintaining visual comfort, which significantly influences occupants' overall satisfaction with their indoor environment. Discomfort glare prediction models have been developed for various lighting conditions, and their equations commonly use either contrast and/or saturation terms to account for glare caused by excessive luminance contrast or excessive overall brightness, respectively. Daylight Glare Probability (DGP), which includes both terms (hybrid model) and thus accounts for both effects, is one of the more robust ones. However, the predictive performance of discomfort glare models is limited to the luminous conditions and light source types found in the dataset from which they were developed. As daylight glare models like DGP are typically derived from glare evaluations in brightly lit environments, their performance in dimmer conditions, such as those found in deep open-plan workspaces away from the window, could be limited. This thesis, therefore, aims to extend the prediction range of existing discomfort glare models to reliably cover low-light ranges as well. To determine which conditions are most critical to focus on, the luminous ranges covered in previous laboratory studies were compared to those that can be expected in open-plan offices where low-light conditions may occur. The identified range of missing lighting conditions was then used to design and conduct two new user studies in semi-controlled dim daylit conditions to supplement prior discomfort glare datasets. In the first study, participants evaluated four scenes in which the size and luminance of the glare source were varied, and in the second, participants evaluated four scenes in which it was the size and position of the glare source were varied. In parallel, the models that currently perform best in dimmer conditions were identified using an existing dataset of glare evaluations in daylit conditions: contrast-driven models were shown to outperform saturation-driven models in dim conditions, while the more versatile hybrid metrics tended to perform well overall. Hence, the hybrid format was found to be better suited for extending glare models. To create a comprehensive training dataset for this model extension, the data obtained from the two user studies were combined with experimental data from other recent studies containing high-contrast scenarios, namely with the sun disc visible through fabric shadings and low-transmittance glazing. A new best-fit discomfort glare prediction model was then proposed for the broader targeted range of luminous conditions. Based on preliminary performance checks, the new hybrid model appears to fit the participants' glare responses better in low-light conditions than the reference model, DGP, while maintaining a fit equivalent to DGP in brightly lit conditions. The new user studies also revealed an unexpected finding: the summation of multiple glare sources in glare model equations can sometimes result in an over-prediction of discomfort glare. More research will be needed to validate the newly proposed model using a larger test dataset that does not include data points used for any model development. This thesis' findings may help to advance daylight glare prediction in indoor spaces by broadening the range of validity of prediction models to dimmer conditions, thus improving the overall reliability of visual comfort appraisal in the built environment.

Exposure to light, and especially to daylight, has much to offer. Regarding buildings’ occupants, daylight has been shown to boost performance, improve sleep, provide a connection to the outside, increase comfort, lessen agitation, and reduce depression. Regarding buildings, daylight enhances the aesthetics of a space and improves its energy efficiency. On one condition, though: that it does not produce visual discomfort. In order to harvest the benefits of daylight, visual discomfort has to be minimized. Hence, discomfort glare from daylight should be predictable. To date, more than twenty daylight discomfort glare models have been developed. However, none of them can consistently and accurately explain the large variation between subjects’ discomfort glare perception. Improving current models predicting discomfort glare perception remains a crucial step to move towards optimal daylighting design in buildings. In this context, it is hypothesized that the prediction of discomfort glare perception can be improved by including relevant additional factors related to the context or to the subject in the models. The main research question that this study aims to answer is to determine whether one of these factors, namely the socio-environmental context of the subject, influences discomfort glare perception from daylight in office buildings. The socio-environmental context is defined here as the climate and habitat, including indoors and outdoors, to which a subject has been acclimatized, her/his behavior toward these elements, and her/his expectations about them. Two additional research questions aim at investigating other potentially influencing factors and potential experimental biases in order to guide further research in the field. For this purpose, a field study was conducted in real office buildings located in four socio-environmental contexts, i.e., Chile, Belgium, Japan, and Switzerland. Discomfort glare perception evaluations, each consisting of a subjective assessment of discomfort glare from daylight and the measurement of the visual stimulus, were collected at the office desk of the 401 subjects who took part in the study. The raw data was processed to derive useful information, and cleansed according to specific rules to ensure data quality. Different statistical analyses were conducted on the processed and cleansed data to answer the main research question. No statistically significant differences in the sensitivity to discomfort glare from daylight could be observed between the subjects acclimatized to the Chilean, Belgian, Japanese, and Swiss contexts. The results show therefore no evidence of an influence of the socio-environmental context of a subject on discomfort glare perception from daylight in office buildings. Furthermore, the influence of several other factors on discomfort glare perception from daylight in office buildings was tested and the data was further analyzed regarding potential experimental biases in order to answer the two additional research questions. A statistically significant effect was found for three factors, namely the self-assessed glare sensitivity, the attractiveness of the view through the window, and the indoor air temperature. From this result, it can be hypothesized that these factors could influence discomfort glare perception. Moreover, further analyses suggest that two experimental biases, namely the glare rating scales and the study type, could be influencing the results of studies on discomfort glare perception. However, since the study was not specifically designed to answer these two additional research questions, and in view of its limitations, no conclusion can be drawn on these last observations. They can, however, be used to guide the development of future studies. In conclusion, this research provides no evidence that discomfort glare from daylight is perceived differently in different socio-environmental contexts. Research efforts in discomfort glare perception from daylight should therefore aim at improving prediction models by looking at other potential factors, such as physiological and environmental ones. Finally, future studies should also aim for the validation of reliable methods to study discomfort glare, and for the development of a unified methodological framework to promote the reproducibility of studies and the comparability of results. L’exposition à la lumière, et en particulier à la lumière du jour, a beaucoup à offrir. En ce qui concerne les occupants des bâtiments, il a été démontré que la lumière du jour accroît les performances, améliore le sommeil, assure une connexion avec l’extérieur, augmente le confort, diminue l’agitation et réduit la dépression. En ce qui concerne les bâtiments, la lumière du jour met en valeur l’esthétique d’un espace et améliore son efficacité énergétique. Cela n’est valide qu’à une condition cependant : qu’elle ne produise pas d’inconfort visuel. Afin de récolter les bénéfices de la lumière du jour, l’inconfort visuel doit être minimisé. Par conséquent, l’éblouissement d’inconfort causé par la lumière du jour devrait être prévisible. À ce jour, plus de vingt modèles d’éblouissement d’inconfort dû à la lumière du jour ont été développés. Cependant, aucun d’entre eux ne peut expliquer de manière cohérente et précise la grande variation de la perception de l’éblouissement d’inconfort d’un sujet à l’autre. L’amélioration des modèles actuels permettant de prédire la perception de l’éblouissement d’inconfort demeure une étape cruciale afin d’avancer vers une conception optimale de l’éclairage naturel dans les bâtiments. Dans ce contexte, nous émettons l’hypothèse que la prédiction de la perception de l’éblouissement d’inconfort peut être améliorée en incluant dans les modèles des facteurs additionnels pertinents liés au contexte ou au sujet. La principale question de recherche à laquelle cette étude cherche à répondre est de déterminer si l’un de ces facteurs, à savoir le contexte socio-environnemental du sujet, influence la perception de l’éblouissement d’inconfort par la lumière du jour dans les immeubles de bureaux. Le contexte socio-environnemental est défini ici comme le climat et l’habitat, en ce compris l’intérieur et l’extérieur, auxquels un sujet s’est acclimaté, son comportement envers ces éléments, et ses attentes à leur égard. Deux questions de recherche supplémentaires visent à étudier d’autres facteurs potentiellement influents, ainsi que d’éventuels biais expérimentaux, afin d’orienter la recherche future dans ce domaine. À cette fin, une étude de terrain a été menée dans des immeubles de bureaux situés dans quatre contextes socio-environnementaux différents, à savoir au Chili, en Belgique, au Japon et en Suisse. Les évaluations de la perception de l’éblouissement d’inconfort, consistant chacune en une évaluation subjective de l’éblouissement d’inconfort causé par la lumière du jour et en la mesure du stimulus visuel, ont été collectées aux bureaux des 401 sujets qui ont participé à l’étude. Les données brutes ont été traitées pour en tirer les informations nécessaires et nettoyées selon des règles spécifiques pour en assurer la qualité. Différentes analyses statistiques ont été effectuées sur les données traitées et nettoyées pour répondre à la principale question de recherche. Aucune différence statistiquement significative de la sensibilité à l’éblouissement d’inconfort dû à la lumière du jour n’a pu être observée entre les sujets acclimatés aux contextes chilien, belge, japonais et suisse. Les résultats ne montrent donc aucune preuve d’une influence du contexte socio-environnemental sur la perception de l’éblouissement d’inconfort par la lumière du jour dans les immeubles de bureaux. De plus, l’influence de plusieurs autres facteurs sur la perception de l’éblouissement d’inconfort dû à la lumière du jour dans les immeubles de bureaux a également été testée et les données ont été analysées plus en détails par rapport aux potentiels biais expérimentaux afin de répondre aux deux questions de recherche supplémentaires. Un effet statistiquement significatif a été constaté pour trois facteurs, à savoir la sensibilité à l’éblouissement auto-évaluée, l’attrait de la vue à travers la fenêtre et la température de l’air intérieur. Une hypothèse peut être émise à partir de ces résultats : ces facteurs pourraient influencer la perception de l’éblouissement d’inconfort. Des analyses additionnelles suggèrent que deux biais expérimentaux, à savoir les échelles d’évaluation de l’éblouissement et le type d’étude, pourraient influencer les résultats des études sur la perception de l’éblouissement d’inconfort. Toutefois, comme cette étude n’a pas été spécifiquement conçue pour répondre à ces deux questions de recherche supplémentaires, et compte tenu de ses limitations, aucune conclusion ne peut être tirée de ces dernières observations. Les hypothèses émises peuvent toutefois servir à orienter l’élaboration d’études futures. En conclusion, cette recherche ne fournit aucune preuve que l’éblouissement d’inconfort causé par la lumière du jour est perçu différemment dans différents contextes socio-environnementaux. Les efforts de recherche sur la perception de l’éblouissement d’inconfort dû à la lumière du jour devraient donc se concentrer sur l’amélioration des modèles de prédiction en examinant d’autres facteurs potentiels, tels que les facteurs physiologiques et environnementaux. Enfin, les études futures devraient également viser à valider des méthodes fiables pour l’étude de l’éblouissement d’inconfort, ainsi qu’à élaborer un cadre méthodologique homogénéisé pour promouvoir la reproductibilité des études et la comparabilité des résultats. (FSA - Sciences de l'ingénieur) -- UCL, 2019

This dissertation proposes a novel gaze-driven approach for dynamic discomfort glare assessments as a first step towards understanding human responsive comfort with respect to daylight. The objective was to observe the natural gaze behaviour in relation to glare for office spaces with the conditions implicitly constrained by real world luminous conditions. In the existing visual comfort models human behaviour is not sufficiently considered. These models employ only subjective assessments, which lack an objective understanding of the factors affecting the perceptual mechanism of light-induced visual discomfort. They so far have not integrated the inter-dependencies of visual discomfort perception and human gaze responses and have been limited to a fixed-gaze assumption directed towards the office task area. In this dissertation, a gaze-driven approach is developed and adopted in the discomfort glare assessments. The assessments were done in a series of experiments in simulated office setting under different lighting conditions where participants’ gaze responses with means of mobile eye-tracking as well as their subjective assessments were recorded while monitoring photometric quantities relevant to visual comfort using high dynamic range luminance imaging. Integration of the luminance images coupled with eye tracking enabled us to obtain the gaze-centred luminance fields, which gives a better estimate of actual luminance values perceived by the eye, used as a basis to investigate the gaze direction dependencies of visual comfort. This PhD dissertation describes different stages of conception of this novel dynamic discomfort glare assessment method. In the experimental phase, two pilot studies were made for proper integration of the adopted methods and techniques into discomfort glare assessments. Development of several routines, algorithms and tools to identify and translate the gaze directions in order to derive the actual luminance field perceived by the participants were needed to achieve this goal. A final comprehensive experimental phase was realised to investigate gaze behaviour in response to light. As a first validation step, the gaze-driven approach was compared to the fixed-gaze approach. Then the effects of different luminance levels as well as different view outside the window on the dynamic shifts of the gaze were investigated.The developed approach demonstrates the need to integrate gaze direction patterns into visual comfort assessments, which move us beyond the existing assumption of a fixed-gaze direction towards a gaze responsive comfort.

Designing architectural façades that allow sufficient daylight to create visually comfortable and pleasant environments is a challenging aspect of building design. It requires accounting for visual comfort and discomfort glare risks and understanding the factors that influence them. In the last two decades, several prediction models have been developed to quantify discomfort glare by considering almost exclusively the photometric properties and spatial distribution of incoming light. Although these empirical models have been derived to best match one's perception of glare, they fail to account for the significant interindividual variability that exists in glare perception and are furthermore limited in their applicability in certain visual environments. It is evident from the literature that not all the factors influencing discomfort glare perception are known and accounted for in the existing prediction models. Based on the literature review, we have identified two potential factors, namely, the macular pigment density in the retina and the color of daylight, as likely to influence discomfort glare perception. Up to now, their influence on glare induced by daylight has remained unknown. To address this gap, this thesis aims to determine the influence of macular pigment density and color of the sun disc (altered by colored glazing) on discomfort glare perception in daylit environments. By means of three psychophysical experiments conducted in office-like test rooms along with the ocular examinations of the participants, we determined the influence of macular pigment and color of daylight on the perception of discomfort glare for young and healthy individuals. Three experiments were conducted, one with blue electrochromic glazing, one with color-neutral glazing, and the third with red, blue, green, and color-neutral glazing. Each experiment followed a similar protocol of exposing every participant to four daylight glare scenarios and recording their responses to questionnaires. The four daylight scenarios differed either in color or in the transmittance of the glazing through which the sun was visible as the primary glare source. The remaining windows were set in a way to keep the overall color rendering in the space as neutral as possible. The results show that macular pigment density does not influence discomfort glare perception from the sun disc filtered by color-neutral glazing in the near-peripheral field of view. However, when exposed to the sun disc filtered by saturated blue-colored glazing also in the near-peripheral field, participants with higher macular pigment density were better able to tolerate the glare, indicating a significant influence of macular pigment in this case. In regards to the influence of color, results show that the perceived color of the sun disc (as filtered by colored glazing) has a strong influence on participants' perception of glare. Direct sunlight filtered through four types of colored glazing of a similar visible (photopic) transmittance caused significantly different levels of discomfort glare perception amongst the participants. More precisely, participants experienced statistically higher levels of glare under the red and blue glazing compared to the colorneutral or green glazing. The findings show that the photopic luminosity function (V2°(l)) is not an appropriate weighting function to characterize the spectral sensitivity of the human eye when a high-intensity colored glare source is in