Clue To Normal-Tension Glaucoma
July 27, 2009
Adapted from the American Academy of Ophthalmology and EurekAlert!
Health conditions in normal-tension glaucoma patients differ from those in patients with the more common primary open-angle glaucoma. For one thing, an increased incidence of silent cerebral infarct blockage in small blood vessels in the brain, is seen in brain scans of people with normal-tension glaucoma. Also, visual field loss is often more rapid in normal-tension glaucoma patients than in those with primary open-angle glaucoma. Researchers at The Chinese University of Hong Kong, led by Dexter Y.L. Leung, FRCS, recently investigated whether silent cerebral infarct might be directly related to rate of visual field loss in patients newly diagnosed with normal-tension glaucoma.
They found that visual field loss was 61 percent more likely in normal-tension glaucoma patients with silent cerebral infarct. Though this study was in newly diagnosed normal-tension glaucoma patients and results could vary in patients who have been in treatment, the results raise important points.
"First, this study adds weight to the hypothesis that vascular factors are likely causes of normal-tension glaucoma, along with intraocular pressure (IOP). Second, if additional studies confirm silent cerebral infarct as a risk factor for visual field loss, treatment to prevent silent cerebral infarct might slow disease progression in normal-tension glaucoma patients. Third, brain scans of normal-tension glaucoma patients to detect silent cerebral infarct might be deemed cost-effective. Since treating silent cerebral infarct is also known to prevent stroke, we may be talking about saving not only vision, but lives," said Dr. Leung.
Normal-tension glaucoma is termed "normal" because the IOP, the pressure within the eye, is lower than the point at which optic nerve damage is known to occur in primary open-angle glaucoma patients. Despite this "normal" IOP, optic nerve damage does occur in NTG patients, who comprise about one-third of all people with glaucoma.
This study was published in the July issue of Ophthalmology.
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