Disorders of the sleep-wake cycle in blindness.

BACKGROUND Alteration of the intensity of light reaching the pineal gland through the visual pathway affects the sleepwake cycle in humans. OBJECTIVE To determine the prevalence, types and severity of sleep-wake disorders in the blind and their relation to the degree and cause of blindness. METHODS One hundred and seventy consecutive blind patients were included in the study. The patients were interviewed and administered the Montgomery Asberg Depression Rating Scale (MADRS) and the Pittsburg Sleep Quang Index (PSQI) questionnaire. Information collected included age, sex, visual loss parameters, type and degree of sleep-wake disorder. RESULTS A total of 138 (81.2%) blind patients had sleep-wake disorders with significant disorder found in 84(49.4%). The mean PSQI+/- SD were 8.4 +/-2.91, 9.6+/- 3.3 and 8.0+/-2.7 globally, no light perception group and the remaining blind patients respectively. The commonest type of sleep-wake disorder was day time nap [112(65.9%)]. Forty-one (46.1%), 33(58.9%), 8(80.0%), 2(100%) and 0(0.0%) of those that had cataract, glaucoma, optic atrophy, uveitis and others respectively had moderate and/or severe sleep-wake disorder. The relationship between degree of blindness and prevalence and severity of sleep-wake disorder was very significant statistically (p= 0.008 and 0.002 respectively). The relationship between causes of blindness and prevalence and degree of sleep-wake disorder was statistically significant (p=0.009 and 0.007 respectively). CONCLUSION This study has shown that the prevalence of sleep-wake disorders in the blind is high and a strong relationship exists between visual loss and the sleep-wake cycle in humans.