Bright light suppresses melatonin in blind patients with neuronal ceroid-lipofuscinoses

We studied whether light information can reach the pineal glands of clinically blind patients with neuronal ceroid-lipofuscinoses. The suppression of melatonin by light was used as an indicator. Seven patients and seven control subjects were exposed to 3,000-lux light for 60 minutes at the rising phase of the melatonin synthesis. Most patients were not cooperative, and their eyelids were opened by a researcher every 2 minutes for 2 seconds. The control subjects opened and closed their eyes similarly by themselves. Light suppressed melatonin in three of seven control subjects and in all patients. The average postlight levels were 80% (control subjects) and 51% (patients) of the corresponding levels during the dim-light session. Despite degenerated retinas of the blind patients, light can penetrate their visual system to the hypothalamic and pineal levels and regulate neuroendocrine function.