People suffering from total blindness are known to have problems with sleeping
at night. Since they are not affected in their circadian clocks by light, they
may fail to distinguish between night and day.
According to a comment in New Scientist for September 16, research at the University
of Surrey in Guildford has indicated that for people in this situation melatonin
therapy may prove helpful. In sighted people melatonin blood levels reach a
peak at about 4am, whereas in someone who is totally blind they peak at different
times of day or night. Sleep may then be necessary during the day to compensate
for its deprivation during the night. In seven totally blind volunteers suffering
severe sleep disruption, melatonin usually gave better night sleep and fewer
daytime naps were required. However, the doses of melatonin need to be timed
correctly in relation to the individual’s personal melatonin peak. Thus,
observation of the individual circadian rhythm is necessary before the appropriate
timing of therapy can be determined.