July 1, 2009 Health conditions in normal tension glaucoma (NTG) patients differ from those in patients with the more common primary open-angle glaucoma (POAG). For one thing, an increased incidence of silent cerebral infarct (SCI), blockage in small blood vessels in the brain, is seen in brain scans of people with NTG.
Also, visual field loss is often more rapid in NTG patients than in those with POAG. Researchers at The Chinese University of Hong Kong, led by Dexter Y.L. Leung, FRCS, recently investigated whether SCI might be directly related to rate of visual field loss in patients newly diagnosed with NTG.
They found that visual field loss was 61 percent more likely in NTG patients with SCI than in those without SCI. Computed tomography (CT) brain scans performed at the beginning of the study showed that of 286 study subjects with similar NTG disease factors, 64 had SCI and 222 did not. Patients' visual field status was assessed every four months over three years. Though this study was in newly diagnosed NTG 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 NTG, along with intraocular pressure (IOP). Second, if additional studies confirm SCI as a risk factor for visual field loss, treatment to prevent SCI might slow disease progression in NTG patients. Third, brain scans of NTG patients to detect SCI might be deemed cost-effective. Since treating SCI is also known to prevent stroke, we may be talking about saving not only vision, but lives," said Dr. Leung.
NTG 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 POAG patients. Despite this "normal" IOP, optic nerve damage does occur in NTG patients, who comprise about one-third of all people with glaucoma.
This research is published in The July issue of Ophthalmology.
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