[The effect of natural and artificial light via the eye on the hormonal and metabolic balance of man (author's transl)].

Examinations of hormone levels in blind persons compared with almost blind and people with normal vision and hormone evaluation with increased artificial light exposure show a definite stimulating effect of light on the human hormonal balance. The effect of light is mediated by an intact perception of light by the eye over an "energetic part" of the visual pathway (Hollwich 1948) - hypothalamus - hypophysis - peripheral endocrine gland. Increasing the intensity of artificial light with "neon-tubes" (fluorescent tubes) leads to "light stress" proved by increased hormone production - especially the stress hormone Cortisol. The belief that artificial light is the same as natural light and that it can fully replace it, is inappropriate in the medical view and needs correction.