Normal tension glaucoma may be nocturnal disorder

Normal tension glaucoma may be nocturnal disorder

NUSA DUA, Indonesia — Normal tension glaucoma is really primary open-angle glaucoma in which risk factors other than or in addition to IOP are found to contribute to the condition, and common sleep disorders may play an important role in the disorder, according to one glaucoma expert here.


Robert Ritch
In defining normal tension glaucoma, "what we are really talking about are risk factors in addition to IOP," Robert Ritch, MD, said in the von Graefe APAO Special Lecture at the joint meeting of the Asia-Pacific Academy of Ophthalmology and the American Academy of Ophthalmology.

Dr. Ritch noted a host of other disorders contribute to the progression of glaucoma in addition to IOP. "About 20 years ago, people realized ischemia plays a role," he said. "In the 21st century, we realize a whole slew of disorders are being investigated." These include cytotoxicity, macular degeneration, genetic disorders, oxidative damage and many others.

Dr. Ritch hypothesized that mechanisms other than IOP are associated with systemic factors and normal tension glaucoma itself is basically a nocturnal disorder associated with sleep disorders.

Studies have shown there is decreased ocular blood flow in sleep apnea, as well as a 27% incidence of glaucoma in sleep apnea patients. Studies have also shown the severity of sleep apnea correlates with the severity of glaucomatous damage, he said.

He said he now takes a sleep history of all of his glaucoma patients, and he has found a "fair number of patients have been positive for sleep apnea syndrome." He cautioned that there are many other conditions associated with compromised ocular blood flow in addition to sleep apnea.

For these reasons and due to the well-documented IOP rise during sleep, Dr. Ritch cautioned that normal tension glaucoma patients with high blood pressure should not take beta-blockers before sleep. Dr. Ritch hypothesized that disc hemorrhages occur mainly at night, but they are not seen until patients present at the clinic during the day.

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