June 2016

 

GLAUCOMA

 

Glaucoma editors corner of the world

Uncovering undiagnosed glaucoma cases to reduce blindness


by Tony Realini, MD, MPH

 
 

Glaucoma usually doesnt have any symptoms until there is visual loss. If our goal is to treat patients before they have noticeable damage, we have to find them when they are asymptomatic. This is screening. Meanwhile, something like one-half of the people with glaucoma arent aware they have it. This means hundreds of thousands of people are going blind without knowing it. These facts seem to call for large-scale screening programs to find people with glaucoma and begin treatment.

But glaucoma screening has been problematic. Although a large number of people have undiagnosed glaucoma nationwide, there may not be manyor anyat a local health fair, and the few who do have it may still be missed. It is easy to fail to detect glaucomawhether in a community screening or in your officebecause none of the tests are definitive every time. For example, many glaucoma patients will have a normal pressure on a single test, visual field testing is too time consuming and variable, and OCT is not reliable as a screening tool.

In this Glaucoma editors corner of the world, we are fortunate to have Alan Robin, MD, David Friedman, MD, Dana Blumberg, MD, Anne Coleman, MD, and Constance Okeke, MD, give us their views on the current state of glaucoma screening. This is an all-star cast of glaucoma epidemiologists, and they share their insights on the pros and cons of screening.

My own view is that we need a different test for screening. We need innovation to create a test that is simple, quick, and fun. It would be based on visual field loss since this is the most definite sign of glaucoma. It could be a video-game type format and would need to work on a smartphone. Until we have better screening tools, the most we can do as ophthalmologists is to not miss the glaucoma in the patients that we see every day. This is its own challenge because the usual testing can be equivocal in the early stages. We also need to remind our glaucoma patients to have their relatives get checked. Helping to detect glaucoma in people who dont know they have it is one of the most important things we do.

Reay Brown, MD, glaucoma editor

 

Dr. Okeke shares this heredity poster that she created with Alcon to help doctors and patients start the conversation about family awareness. Source: Alcon

Approaches to glaucoma screening

In 2013, the U.S. Preventive Services Task Force, an independent panel of evidence-based medicine experts, concluded that there was insufficient evidence to recommend large-scale screening efforts to identify undiagnosed glaucoma in the community. The group opined that effective screening methodology was lacking and that the benefit of detecting early field defects remains unclear.

Glaucoma specialists take a different view of glaucoma screening. At the 2016 American Glaucoma Society annual meeting, the topic of glaucoma screening was revisited.

Screening is important

The burden of undiagnosed glaucoma is significant. About half of people with glaucoma are unaware that they have the disease, said David Friedman, MD, Baltimore. Among people at highest risk, the numbers are even worse. In Hispanics, 6276% of glaucoma is undiagnosed, and in the developing world, up to 90% of people with glaucoma are unaware they have the disease. Dana Blumberg, MD, MPH, New York, agreed, and pointed out that the problem will only get worse with time. High risk populationssuch as blacks and Hispanicsare growing and aging. These are the groups at highest risk for glaucoma and glaucoma-related blindness.

Community or opportunistic screening?

Most glaucoma specialists support screening efforts, but there are challenges. One challenge is who to screen. Should we go out into the community or should we look within our own offices? Screening is difficult, Dr. Friedman conceded. The disease has no symptoms until in the advanced stages. Still, he thinks that community-based screening has value. We need to start screening for glaucoma in the communities around us. He pointed out that they are most interested in screening people at high risk for having glaucoma, and many in this group tend to underutilize health care services overall. Thus, if we dont go out and look for them, they are unlikely to come to us, he pointed out.

The population is aging, and if we dont get people with glaucoma under care, were going to see more and more blindness, he said.

Conversely, Anne L. Coleman, MD, PhD, Los Angeles, suggested that we look within our own practices. She cited the results of several epidemiological studies showing that up to 50% of people newly diagnosed with glaucoma in screening programs had seen an eyecare provider in the previous 12 months and the opportunity to make the diagnosis had been missed. We need to reduce the risk of missed glaucoma, she said.

Who is missed?

There are several clinical attributes that play a role in missing the diagnosis of glaucoma. More than half of all glaucoma occurs in eyes with IOP in the normal range, Dr. Coleman said. He said that elevated IOP serves as a reminder to the clinician to conduct a careful examination of the optic nerve for subtle signs of glaucomatous optic neuropathy. In eyes with normal IOP, we may be less likely to pay such close attention to the optic nerve examination.

Also, disc size can mislead us. Glaucoma is missed more often if the optic nerve head is small, he said. He pointed out that small nerves should have small cups. A small nerve with a 0.4 cup might have early glaucoma, but would look quite healthy if the nerves small size in not appreciated.

How to screen?

Another challenge is what testing paradigm should be used? Screening by IOP is of very little value. As Dr. Friedman pointed out, half of glaucoma patients have normal IOP. Also, most people with elevated IOP do not have glaucoma. Therefore, we would miss at least half of the glaucoma patients, and most of the screen fails would be ocular hypertensive but not have frank glaucoma.

Structural screening could be as easy as looking with the direct ophthalmoscope or as innovative as using advanced imaging such as optical coherence tomography (OCT). The former has been shown to be poorly sensitive and specific for glaucoma detection, and the latter is both expensive and not portable.

Perimetry is a hallmark of glaucoma and the gold standard in defining the presence of disease. Most perimeters are not portable. The frequency doubling technology platform is portable but requires constant power and has not been associated with favorable screening performance, said Alan L. Robin, MD, Baltimore. Dr. Robin described several web-based and device-based perimetry platforms that can be administered using a tablet. Some of these show good correlation with standard suprathreshold perimetry in detecting moderate and severe glaucoma damage and may have value in community-based screening efforts, he said.

Screening patients families

In our quest to find the undiagnosed glaucoma patients in our communities, the lowest hanging fruit may be closer than we think: our patients relatives.

A family history of glaucoma is strongly correlated with POAG, said Constance Okeke, MD, Norfolk, Virginia. In the Baltimore Eye Survey, a positive family history was associated with a 3.5-fold increased risk of developing glaucoma. She added, In the Barbados Eye Study, 23% of relatives of known glaucoma patients had manifest open-angle glaucoma. She recommended that we encourage our patients to encourage their relatives to get tested. We need to educate our glaucoma patients to talk to their family members about glaucoma risk and the value of screening evaluations.

Editors note: The physicians have no financial interests related to their comments.

Contact information

Blumberg: dmb2196@cumc.columbia.edu
Coleman: coleman@jsei.ucla.edu
Friedman: david.friedman@jhu.edu
Okeke: iglaucoma@gmail.com
Robin: arobin@glaucomaexpert.com

Uncovering undiagnosed glaucoma cases to reduce blindness Uncovering undiagnosed glaucoma cases to reduce blindness
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