Comment 2
Abstract
Discussion Comment 1 on 'Ambulant Recording of Light for vision and Unspecific Biological Effects' by S Hubalek, D Zo¨ schg, and C Schierz C Cajochen (Centre for Chronobiology, Psy- chiatric University Clinics, Wilhelm-Kleinstr. 27, CH 4025 Basel, SWITZERLAND) Light B more than vision Our light-sensing systems0/familiar func- tion is to collect and process light to generate an image of the world. Although light pri- marily serves vision, it is now known that it also exerts powerful non-visual effects on a number of physiological variables in humans, among them synchronisation of circadian rhythms, suppression of the hormone melato- nin, and an increase in cortisol and heart rate. Exposure to bright light enhances alertness levels and has been proven to be an effective therapeutic intervention for patients of all ages with Seasonal Affective Disorders (SAD) and subsyndromal SAD. Parts of those non-visual effects of light are mediated by non-classical photoreceptors with melanopsin acting as photopigment with a maximum sensitivity in the /blue0/part of the visible electromag- netic spectrum. Although the knowledge of lights0/non- visual effects in humans has considerably accumulated over the past years, simple ques- tions such as /how much light0/and what /kind of light0/we usually receive during our