Narrow Retinal Vessels Raise Risk for Open-Angle Glaucoma

Linda Roach

January 09, 2013

Epidemiologists have found another nugget of gold in data from the population-based Blue Mountains Eye Study: a strong association between narrowed retinal arterioles and an elevated risk of developing primary open-angle glaucoma (OAG) within 10 years.

Participants with a retinal arteriolar caliber in the lowest quartile at baseline were approximately 4 times more likely to develop OAG during the subsequent decade than those in the highest quartile, Ryo Kawasaki, PhD, from the Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, University of Melbourne, Australia, and the Department of Ophthalmology, Yamagata University Faculty of Medicine and the Osaka Medical Center for Health Science and Promotion, Japan, and colleagues report in their article, published in the January issue of Ophthalmology.

After adjustment for possible confounding factors, there still was a 77% greater risk of developing OAG for each standard deviation decrease in arteriolar caliber (adjusted OR, 1.77; 95% confidence interval, 1.12 - 2.79; P = .014), the group reports. The researchers adjusted for age, sex, body mass index, glaucoma family history, smoking, diabetes, hypertension, hypercholesterolemia, spherical equivalent refraction, and cup-to-disc ratio. (Separate analyses, which added intraocular pressure and ocular perfusion pressure, also had little effect on the risk outcomes.)

"That is a very significant increase in risk. It's beyond even something like a family history of high intraocular pressure," Louis Cantor, MD, chairman and professor of ophthalmology at the Eugene and Marilyn Glick Eye Institute, Indiana University School of Medicine, Indianapolis, told Medscape Medical News.

Compelling Data

"Their data that this is a significant risk factor is pretty compelling, actually," Dr. Cantor noted. "It's not too often that we run into things that are considered completely new risk factors."

Since the mid-1990s, the Blue Mountains Eye Study, a population-based cohort study in Australia (n = 3654), has been the basis for dozens of peer-reviewed research papers delineating the risk factors for eye and systemic diseases that increase with age.

The current study examined the records of 2417 participants for whom the database had retinal photographs and 5-year and 10-year follow-up exam results. There were 82 incident cases of OAG (104 eyes) in the 10-year period they studied, the researchers write.

They used computer image analysis software to measure retinal arteriolar and venular caliber on the baseline retinal photos taken as part of the Blue Mountains protocol. The diameters of the 6 widest vessels of each type then were summed up to produce a pair of numbers that could be compared from eye to eye and correlated with glaucoma incidence.

Differences in venular caliber were not associated with higher glaucoma risk, the researchers found, but the mean arteriolar caliber, which they called the "central retinal artery equivalent," was 156.1 μm (SD, 15.1 μm) in the eyes that later developed glaucoma compared with 160.6 μm (SD, 14.9 μm) in those who did not.

"Our results suggest that a computer-based imaging tool designed to detect narrowing of the retinal artery caliber, or diameter, could effectively identify those who are most at risk for open-angle glaucoma. Such a tool would also need to account for blood pressure and other factors that can contribute to blood vessel changes. Early detection would allow ophthalmologists to treat patients before optic nerve damage occurs and would give us the best chance of protecting their vision," lead author Paul Mitchell, MD, PhD, from the Centre for Vision Research, University of Sydney, Australia, stated in an American Academy of Ophthalmology news release.

The investigators previously reported that individuals with OAG at baseline were 2.7 times more likely to have retinal arterial narrowing that those who did not have OAG at baseline.

Supported by the Australian National Health & Medical Research Council and the Centre for Clinical Research Excellence. The Centre for Eye Research Australia receives support from the Victorian Government, Australia. This study was also supported by a Japanese grant-in-aid for scientific research. The authors have disclosed no relevant financial relationships. Dr. Cantor is a consultant for Abbott Medical Optics and Allergan. He receives research support from Allergan, Alcon, Pfizer and Merck and speaking fees from Allergan.

Ophthalmology. 2013;120:84-90. Full text

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