Therapeutic exposure to sunlight WordNet 3.0 & Open English WordNet

Light therapy, also called phototherapy or bright light therapy is the exposure to direct sunlight or artificial light at controlled wavelengths in order to treat a variety of medical disorders, including seasonal affective disorder, circadian rhythm sleep-wake disorders, cancers, and skin wound infections. Wikipedia

Therapy consisting of exposure to daylight or to specific wavelengths of light, for a prescribed amount of time or at a specific time of day Wikidata

Any medical therapy by exposure to light. Wiktionary

Therapy. Wiktionary (translation)