Eyeworld

EW FEATURE 35 by Michelle Dalton POAG is becoming an individualized disease No one test is best for diagnosing the disease or progression, experts say. It all depends on the patient D etecting glaucoma—and its progression—is a com- bination of multiple tests, and no one single test is best for any one individ- ual patient. Regardless of where a patient is (ocular hypertension, early glaucoma, advanced glaucoma), the primary tests used for evaluation re- main stereo optic disc photography, visual field analysis, and optical co- herence tomography (OCT). "Developing a glaucoma care plan is a form of personalized medi- cine. We want to assess the individ- ual risk of disease onset and disease progression, try to tailor the testing (structural, functional, and fre- quency of testing) and visits to the individual patient," said Jeffrey Liebmann, MD, clinical professor of ophthalmology, New York Univer- sity School of Medicine, and director of the glaucoma services, Manhattan Eye, Ear and Throat Hospital, New York. Dr. Liebmann suggested physicians should be less concerned about determining if progression has occurred and more concerned about the rate of that progression. "We need to pay attention to the rates of change over time—this will allow us to determine the likelihood of visual impairment due to glaucoma over the lifetime of the patient." The "most important" thing to look for is progression, said Robert J. Noecker, MD, in private practice, Ophthalmic Consultants of Con- necticut, Fairfield, because "every- one can't be 'average' in terms of progression. The main thing is if that person is changing on our watch." Confounding the issue is that while seeing abnormalities in the retinal nerve fiber layer and correlat- ing those to visual fields to make a diagnosis is one thing, "telling when that retinal nerve fiber layer is get- ting thinner and is progressing and correlating that with the rest of the examination is very difficult," said Louis B. Cantor, MD, chair and professor of ophthalmology, Jay C. and Lucile L. Kahn professor, and director of the glaucoma service, Indiana University School of Medicine, Indianapolis. Further, that assessment may be somewhat subjective as "trying to see if there is progressive change is difficult," he said, calling that one of the biggest challenges glaucoma specialists face. "Establishing the diagnosis of glau- coma, while often challenging, is not nearly as difficult as determin- ing when the glaucoma is getting worse." As every ophthalmologist knows, visual fields (VFs) "require an alert and cooperative patient," said Brian Samuels, MD, PhD, assistant professor of ophthalmology, Univer- sity of Alabama at Birmingham. "Additionally, studies have shown that a relatively large percentage of the retinal ganglion cells have to be lost before a visual field defect is apparent." The key to successfully manag- ing POAG patients is to identify early disease and begin treatment "when they're having nerve fiber layer loss to prevent visual field loss. If field loss is present, you want to treat them to prevent or delay func- tional impairment and disability," Dr. Liebmann said. Dr. Samuels prefers to use a combination of tests "and there are times that one test may show progression quicker than others," Dr. Samuels said. Some evidence exists that struc- tural tests (OCT) to look for change may be the best method, "but we're finding more and more people who are getting worse, but a visual field defect hasn't shown up yet. There's that concept of preperimetric glaucoma," Dr. Noecker said. All of that may go out the window if the patient is merely an ocular hypertensive and does not progress to glaucoma, the experts said. "Only about 10% of the patients enrolled in the Ocular Hypertension Treatment Study were noted to have both visual field changes as well as disc photo changes at the time they were diagnosed as progressing from ocular hypertension to definitive glaucoma," Dr. Samuels said. "In my mind, this underscores the impor- tance of multi-modal testing in our glaucoma patients. Currently, no single tool or test has a high enough sensitivity and specificity for glau- coma progression to make it the only one you need. I am hopeful that as OCT technology progresses, it provides us that objective test that we have been looking for, but I don't think we are quite there yet." Diagnosing anatomic damage Perhaps the most frustrating aspect of using VF to assess damage is how subjective it is, or maybe a relatively large percentage of retinal ganglion cells have to be lost before a VF defect is apparent. Either way, it is far from perfect, but VF is about as good as it gets—for now. In very severe disease, VF testing may become unreliable, Dr. Liebmann said. "Just when we need the VF the most, it can fail us," he said. Patients with peripheral damage may not be as bothered as those with less dam- age that is more central, he added. VFs are insensitive to early or moderate damage, and there is a "great deal" of fluctuation within the test results themselves, so "estab- lishing a baseline is difficult and can require a number of tests before you get a reliable baseline," Dr. Cantor said. In his opinion, multiple fields may be needed to confirm progres- sion. Even with all the downsides to VF testing, "they're still the go-to," Dr. Noecker said. VFs have the advantage of being more quantifiable than optic disc photos, Dr. Samuels said, and fol- lowing the pattern over the years is the only way to assess progression. The one thing that is a given— physicians need a few years' worth of data to get the complete visual picture, Dr. Liebmann said. Dr. Samuels recommends looking at each VF back to the baseline, "regardless of whether it's been 3 months or 5 years. If you're only looking back over a few visits, you May 2014 AT A GLANCE • Individualized assessment and evaluation are necessary. • Visual fields are the most used method to detect progression, but are still too patient-dependent. • OCT technology is advancing so quickly that it should not be the sole diagnostic. • Stereo disc photography remains mandatory for baseline assessment. continued on page 36 A trabeculectomy may do a better job of controlling the IOP in those patients, he said, adding that if done in a phakic eye, it should be done with an iridectomy. "You want to perform that as well to remove the pupillary block component of angle closure. Otherwise, you'll make a hole in the sclera and the patient is still going to be at risk of an acute attack," he said. Dr. Brown said that ACG patients with particularly high pres- sures may need a trabeculectomy but even then, he usually tries cataract surgery first. It goes back to tempering patient expectations, he explained. "You have to tell the pa- tient there's a chance the cataract surgery might not work and that you'll have to do a trabeculectomy next week. You can't tell patients that the cataract surgery will always work. You have to say this is some- thing that may help, but if it does- n't, we have a next step and we'll have to do it quickly," he said. EW References 1. Friedman DS, Vedula SS. Lens extraction for chronic angle-closure glaucoma. Cochrane Database Syst Rev. 2006;19:CD005555. 2. Emanuel, ME, Parrish RK II; Gedde SJ. Evidence-based management of primary angle closure glaucoma. Curr Opin Ophthalmol. 2014;25:89–92. Editors' note: The physicians have no financial interests related to their comments. Contact information Bell: nbell@cizikeye.org Brown: reaymary@comcast.net Friedman: friedman@jhu.edu Making the case continued from page 34

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