Melatonin suppression by illumination of upper and lower visual fields

As a guide to optimizing the geometry of bright Light treatment, 12 healthy subjects were studied three times in the laboratory from 11 p.m. to 2 a.m. On three evenings, in counterbalanced orders, subjects received 500 lux in the upper visual field, 500 Iu:in the lower visual field, or 5 lux while w atching television. In the upper visual field, 500 lux significantly suppre ssed melatonin, as compared to 500 lux in the lower visual field or to 5 lu x. Ln the lower visual field, 500 Iue produced intermediate suppression of borderline significance. The results suggest that bright Light treatment of depression or circadian phase disorders might be most effective when appli ed in the upper visual field.