Wiktionary
photomedicine
n. (context medicine English) The branch of medicine that involves the therapeutic use of light
Wikipedia
Photomedicine
Photomedicine is an interdisciplinary branch of medicine that involves the study and application of light with respect to health and disease. Photomedicine may be related to the practice of various fields of medicine including dermatology, surgery, interventional radiology, optical diagnostics, cardiology, circadian rhythm sleep disorders and oncology.
A branch of photomedicine is light therapy in which bright light strikes the retinae of the eyes, used to treat circadian rhythm disorders and seasonal affective disorder (SAD). The light can be sunlight or from a light box emitting white or blue (blue/green) light.