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 administerd 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 sleepwake
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.