RESUMEN
An internal 24-hour biological clock working in tandem with external environmental cues like bright light regulates our daily rhythms specially sleep-wake cycle. In a blind individual, due to absence of external cue endogenous rhythm may take upper hand and free running of sleep-wake cycle starts without any synchronicity with day-night cycle, creating ground for sleep disorders. To evaluate the frequency of sleep disorders, 65 blind individuals without any comorbid medical or surgical problem were interviewed according to the criteria of Diagnostic and Statistical Manual of Mental Disorder-IV (DSM-IV). Simultaneously 70 persons with no visual impairment were assessed in the same manner as used for blind persons. Blind patients showed far higher presence (44.6%) of sleep problems compared to controls (15.7%), and this difference was highly significant statistically [odd's ratio (OR) = 4.32, CI 95 =1.8-10.54]. Blind patients showed far higher presence (43.1%) of DSM-IV based diagnosis compared to controls (8.6%), and this difference was highly significant statistically [OR = 8.072, CI 95 = 3.059-21.298]. Circadian sleep disorders, insomnia and hypersomnia were relatively higher in blind patients. High incidence of sleep disorders calls for development of short reliable screener for sleep disorders among blind persons and better liaison among ophthalmologists and psychiatrists for early detection of this problem.