Light has been shown to not only enable human vision, but to also elicit other physiological responses. Besides its ability to influence the human circadian rhythm, acute effects of light on attention and well-being could be identified. It is thought that these effects are mainly driven by a specific receptor type in our retina -intrinsically photosensitive retinal ganglion cells (ipRGCs). These contain the photopigment melanopsin that is highly sensitive to light in the short wavelength range of the spectrum. It has been found that higher activation of ipRGCs is connected to entrainment of the circadian system.

However, evidence for a positive impact of an increase in ipRGC activation on attention is much less clear. Especially the impact of light on attention during the day in comparison to exposure during the evening and at night is yet to be fully discovered. Although attempts have been made in order to reduce this gap of knowledge, existing studies often do not consider long exposure durations and mainly investigate lighting scenes that are rather unusual regarding real-life settings.

In this thesis, effects of light on attention of employees during work were examined. First, a laboratory study that focused on attention of fulltime daytime workers at office workplaces was executed. Attention was quantified by subjective scales, as well as psychomotor tasks. Activation of ipRGCs was varied by changing illuminance and spectrum of the light. In contradiction to the aforementioned findings, the lighting with the lowest activation of melanopsin led to best results in performance parameters and self-reported measures. It could be shown that the change in lighting also led to significant differences in perceived mood and comfort. In addition, a field study that focused on home-based workers was executed. For most participants a lack of light exposure in terms of ipRGC activation could be identified. The study included an intervention period in which an additional lighting was added to participants’ workplaces. This lighting resulted in a significant increase in light exposure levels which was partly translatable to improvements in mood states and performance parameters.

In general, findings of both studies underline the importance of effects of light on comfort and mood in combination to the activation of the human alerting system by activation of ipRGCs. Therefore, the complex interplay of those impacts should be investigated further, in order to create lighting for office and home-based workplaces that support both employees’ attention but also well-being at work.