Aside from experiencing the distinct disadvantage of not being able to see, blind individuals may suffer from a sleep disorder known as “circadian rhythm disorder.” This inability to sleep in accordance with regular sleeping and waking times stems from a blind person’s inability to take time cues from daylight. Normally, a person’s “internal body clock” is set on its 24-hour cycle by exposure to natural light. Beginning in the morning and extending throughout the day, the eyes’ photoreceptors detect sunlight and transmit the information to the brain, which uses it to suppress melatonin (the sleep hormone) production. Once circadian sleep disorder is properly diagnosed, treatments ranging from behavioral therapy to medication can help blind individuals establish a regular sleeping pattern.
P.S. Tasimelteon (Hetlioz) was approved by the FDA in January 2014 for treatment of circadian rhythm disorder in totally blind individuals.