SAN FRANCISCO--A study appearing in the February issue of Ophthalmology--the clinical journal of the American Academy of Ophthalmology, the Eye M.D. Association, shows that inner retinal and optic nerve disease may be a significant risk factor for sleep disorders.
In the prospective cohort study, researchers observed the sleep-wakefulness cycles of 25 visually impaired subjects, ages 12 to 20, and compared them with the cycles of 12 young subjects with normal sight. Because recent basic research has suggested the retina contains non-visual photoreceptors in the inner ganglion cell layer that communicate directly with the areas of the brain involved in circadian rhythms, the visually impaired subjects were divided into two groups--those with optic nerve disease and those without. Daily activity, including both sleep and wakeful periods of the subjects, was continuously monitored for 14 days using a wrist-worn actigraph.
"The study showed the subjects with optic nerve disease were 20 times more likely to have pathologic levels of daytime sleepiness, as indicated by napping, than the subjects with normal sight," said one of the study's authors, Russell N. Van Gelder, MD, assistant professor in the Department of Ophthalmology and Visual Sciences at the Washington University Medical School, in St. Louis. "They were also nine times more likely to have pathologic sleepiness than the visually impaired subjects who were blind from the non-optic nerve diseases. We suspect these patients have difficulty using daylight to synchronize their internal rhythms to the outside world."
The subjects with the optic nerve disease also had highly variable wake-up times and had more trouble falling asleep compared to the other two groups. "Taken together, these results lead to the unexpected conclusions that eye disease is a risk factor for sleep disorders and whether the optic nerve is healthy or diseased strongly influences the risk of sleep disorders," Dr. Van Gelder said. "Physicians and other health care professionals should be sensitive to the possibility of daytime sleepiness or insomnia, particularly in patients with severe optic nerve disease." This will likely affect all patients with congenital optic nerve hypoplasia, congenital glaucoma and other early onset optic neuropathies.
"There is an important take-home message here for all ophthalmologists," said Alfredo A. Sadun, MD, PhD. "While some might argue that there is little merit in trying to salvage already bad vision, this present clinical study confirms what we already suspected from basic science investigations. That is, even rudimentary vision is a required substrate for human health and longevity. Vision helps entrain the neuroendocrine control of circadian rhythms, and even poor vision is much better than no vision at all." Dr. Sadun's discussion of the study is also published in this issue of Ophthalmology. He is the Flora Thornton Endowed Chair of Vision Research and Professor of Ophthalmology and Neurosurgery at the Doheny Eye Institute/Keck-University of Southern California School of Medicine.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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