Early Glaucoma Damage Sometimes Missed by Visual Field Test

Jenni Laidman

January 17, 2014

The standard 24-2 visual field (VF) test for glaucoma missed early glaucomatous damage in the central macula that was detectable via a 10-2 VF test, according to research published online January 9 in JAMA Ophthalmology.

In a prospective observational cohort study, Ilana Traynis, BS, from the Department of Psychology, Columbia University, New York City, and colleagues used a 10-2 VF test to examine 100 eyes from 74 patients with glaucomatous optic neuropathy and a 24-2 VF with mean deviation (MD) better than −6 dB.

The researchers found that among the 83 hemifields that appeared normal with 24-2 VFs, 13 (15.7%) were found to be abnormal in subsequent 10-2 testing. That is, among the 22 eyes judged normal in 24-2 testing, 22.7% were found to be abnormal in 10-2 testing. Sixty-eight percent of the abnormal 10-2 hemifields were arcuate-like, 8% were widespread, and 25% were described as "other."

Senior author Donald Hood, PhD, professor, Department of Psychology, Columbia University, told Medscape Medical News that the research means clinicians should consider adding a 10-2 VF test for some patients or modifying current 24-2 VF equipment. "What we're suggesting, at the very least, is that if [clinicians] have any reason to suspect macular damage, the patient complaining of fuzzy vision or difficulty reading, or even if 24-2 looks a little funny, add a 10-2. Even better would be to use a 24-2 modified to add points in the center," Dr. Hood said. The 10-2 VF looks at points every 2 degrees. The central 4 test points in the 24-2 VF test sit at the edge of central vision, with more than 30% of all the ganglion cells, Dr. Hood said.

He noted that the study reveals the clinical implications of his earlier findings, using frequency domain optical coherence tomography to study the anatomic characteristics of glaucomatous damage.

Glaucomatous Macular Damage More Common Than Many Clinicians Realize

"I think the important message of this paper and the work we're doing in general is that glaucomatous damage [in the macula] is more common than most clinicians think," Dr. Hood said.

Although it has been known that the 24-2 VF test, with its test points placed 6 degrees apart, can miss damage that falls between the points, this study is the first to examine the issue systematically, Paul Artes, PhD, associate professor and foundation scholar, Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada, told Medscape Medical News. Dr. Artes was not involved in the current study. "They're really taking a fairly large group of 100 eyes and investigating them systematically. I don't think anyone has done that before."

He added, "Until recently, people would have thought the macula is protected in glaucoma, that it isn't damaged until very late. So this does clearly show there is damage early on in that central region." That does not mean the 10-2 test should replace the 24-2 test, he said. "But if you are suspicious there is something in the center, do a 10-2."

Anne Coleman, MD, PhD, clinical spokesperson for the American Academy of Ophthalmology; professor of ophthalmology in the Jules Stein Eye Institute of the David Geffen School of Medicine at the University of California, Los Angeles; and professor of epidemiology in the University of California, Los Angeles, School of Public Health, called the study "interesting and thought provoking," in an email to Medscape Medical News.

"But because glaucoma is diagnosed not only based on visual fields but also based on evidence of nerve damage, I think it would be important as a next step to evaluate the visual field procedure as part of a broader, more realistic clinical protocol that includes evaluation of the nerve," she noted.

Her own strategy in glaucoma diagnosis is to combine visual field testing with visual inspection of the nerve, and before she modifies her clinical practice, she wrote, "I am going to be on the lookout for studies that more closely mirror my approach. In addition, I am not sure the mix of patients in my practice and the mix of patients in the study have similar distributions of clinical characteristics."

The authors, Dr. Artes, and Dr. Coleman have disclosed no relevant financial relationships.

JAMA Ophthalmol. Published online January 9, 2014. Abstract

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