Daylight – visual comfort and non-visual functions

Within the last decades it became evident that light through the eyes is essential for both visual and non-visual functions. One of the most important non-visual functions of light is the daily entrainment of the circadian clock by environmental light conditions. As most people spent the majority of their time inside of buildings, room light quality defines not only vision related properties but also many physiological and behavioral functions. This is true for acute light responses but also for circadian (and probably even longer lasting) light effects. Another emerging question is to what extent visual and non-visual functions might be associated with each other. We tested whether visual comfort is associated with subjective alertness, mood and physical wellbeing. By comparing these effects under two different office lighting conditions in healthy young subjects during daytime, we found that associations of visual comfort with alertness, mood and wellbeing were not only dependent on the light condition but also on the time of day. We also found repercussions of different light conditions during the afternoon on cognitive performance in the evening. We conclude that for optimized environmental light conditions visual and non-visual human aspects of light need further to be integrated into architectural and building science.