NOV 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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36 EW GLAUCOMA November 2013 February 2011 Are disc photos still useful in glaucoma? by Tony Realini, MD before those changes are evident on clinical examination or by visual field testing, Dr. Schuman said. The challenge is knowing when those changes in the imaging test are due to real changes in the optic nerve versus false-positive changes that may be artifacts. "These false positive results can arise from bad scans," he explained. "It is critical to assess the quality of the test before accepting the test results." The case for photographs Dr. Khouri evaluating images transmitted via telemedicine. H igh-tech optic nerve imaging was supposed to revolutionize glaucoma management. Whether by scanning laser polarimetry (the GDx platform), confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph, HRT, Heidelberg Engineering, Heidelberg, Germany), or optical coherence tomography (made by many manufacturers), automated optic nerve scans were anticipated to make the optic nerve photograph—and perhaps the clinical optic nerve examination— obsolete. It hasn't happened. True, various studies have shown that some of these devices are approximately as good as a glaucoma specialist at distinguishing between glaucomatous and non-glaucomatous optic nerves. However, by definition, the diagnosis of glaucoma had already been ruled in or out without the device's help before the studies were conducted. It's not the obvious cases of glaucoma we need help diagnosing. Also true, some devices have been proven to identify optic nerves that will become glaucomatous even Source: Albert Khouri, MD when expert glaucoma specialists call them normal. However, few if any glaucoma specialists have replaced their own clinical evaluation of the optic nerve with a machine's output. Despite these realities, many if not most ophthalmology practices have at least one optic nerve imaging platform. So the question remains: What is the role of optic nerve photography in glaucoma management today? The case for imaging Imaging has an important role in glaucoma, according to Joel Schuman, MD, University of Pittsburgh. "In the Ocular Hypertension Treatment Study (OHTS), subjects had to have normal optic nerves— as judged by a panel of expert glaucoma specialists—to be enrolled," he said. The HRT ancillary study to the OHTS clearly showed that the HRT could identify the nerves that were more likely to eventually become glaucomatous. "The imaging device saw something that the experts didn't," he said. Imaging can also see small changes in the optic nerve structure George Spaeth, MD, Wills Eye Institute, Philadelphia, agreed that imaging has clinical utility. "Modern optic nerve imaging techniques are immensely important," he said. "We want something that is both useful and functional. The imaging techniques are touted as being more objective than clinical examinations of the optic nerve. But these techniques are not as objective as they seem. They are noisy." In contrast, he said, "Photographs work. They are useful. They are relevant." He pointed out that imaging technologies provide outputs filled with various parameters, while a disc photograph provides one thing: an image. "One piece of relevant information is more valuable to us than 100 pieces of data that we don't know what to do with," he said. He also said that photographs will stand the test of time. "They are valuable now, and they will continue to be valuable for many years to come. The technology will not become obsolete." Dr. Schuman pointed out one additional feature of optic disc photographs. "They show us things we cannot see with imaging. Among these are disc hemorrhages and peripapillary atrophy. You won't see a disc hemorrhage on an imaging test. A skilled examiner might see it. A photograph will capture it." He noted that even the expert observers in OHTS missed a number of disc photos during the clinical examination that were subsequently detected on photographs. Screening: The special case One application in which photographs are likely superior to imaging is in screening. Albert Khouri, MD, Rutgers University, Newark, N.J., utilizes telemedicine both in his research and his clinical practice. "Optic disc photography is less expensive and more widely available than imaging," he said. He added that screening for glaucoma by nerve appearance is a challenging endeavor. "There is substantial overlap between the appearance of healthy nerves and those with early glaucoma," he said. This generates false positives that require expensive confirmatory testing. "The advantage of an optic nerve photograph is that it can easily capture the entire posterior pole," he said. "This allows us to screen for other important causes of blindness, such as macular degeneration and diabetic retinopathy, using the same image." This multi-phasic screening approach increases both the diagnostic yield and the cost effectiveness of screening for eye disease, he said. Clinical impact Dr. Spaeth said that if he developed glaucoma, "I hope my physician obtains a disc photograph on me." Dr. Schuman said, "If you have an expert optic nerve examiner, imaging will give you little additional information. However, imaging technologies standardize the interpretation of ocular structures at an expert level and minimize intra- and interobserver variation." Dr. Khouri said that imaging should be considered an adjunct to the clinician's own judgment. "If imaging shows an abnormality or a change, that is my cue to look more closely at the nerve to see if I agree that the finding is clinically relevant." EW Editors' note: Dr. Khouri has no financial interests related to the article. Dr. Schuman has financial interests with Massachusetts Institute of Technology, Massachusetts Eye & Ear Infirmary and Carl Zeiss Meditec (Jena, Germany). Dr. Spaeth has no financial interests related to the article. Contact information Khouri: albert.khouri@rutgers.edu Schuman: schumanjs@upmc.edu Spaeth: gspaeth@willseye.org

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