Impact of light on non-visual functions of the human eye

The luminous environment does not only affect visual performance but also human physiology and behaviour, in particular circadian rhythms, alertness, well-being and mood. Non visual photoreceptors on the mammalian retina discovered not long ago are involved in these effects. In lighting design it is accordingly necessary to take into account not only luminous intensity, but also light's spectral composition, since the non visual photoreceptors are more maximal sensitive to different luminous wavelengths than visual photoreceptors (e.g. rods and cones).

To investigate both visual and non-visual effects, Apiparn Borisuit first set up a new photometric device based on a high dynamic range logarithmic visual sensor (IcyCAM^TM) for the monitoring of the luminance distribution within a scene. The apparatus was then used in two experimental studies with human subjects, aiming to test the acute effects of light on visual comfort variables, subjective alertness, mood and well-being. Among other, the impacts of luminous distribution over time and under various lighting conditions were investigated as well as inter-individual differences, as assessed in extreme chronotypes.The results obtained with the new device provide a more comprehensive scientific framework and practical basis for indoor lighting design at workplaces.

Apiparn Borisuit's thesis was supervised by Dr Mirjam Münch and Prof. Jean-Louis Scartezzini of the EPFL Solar Energy and Building Physics Laboratory. The work was financed by the Velux Foundation.