The relationship of melatonin regulation and color vision in humans

A 200 lux white light stimulus significantly (p < 0.001) suppressed plasma melatonin in both subjects with normal color vision and in subjects with color vision deficiencies, with no significant difference in the degree of melatonin suppression between the two groups. These data suggest that a normal three cone photopic system may not be necessary for light regulation of the human pineal gland. This finding raises questions about the practice of measuring and describing light in photometric terms - currently the standard practice among investigators studying the effects of light on the human pineal gland, the circadian system, and therapeutic applications.