EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/407647
EW NEWS & OPINION 26 November 2014 by Michelle Dalton EyeWorld Contributing Writer Anterior segment imaging devices G onioscopy—long the gold standard in glaucoma examinations—is admit- tedly difficult to learn, and as a result may not be used as often in clinical practice as it is during residency. The numer- ous angle "grading" schemes can be confusing as well. Coupled with the introduction of anterior segment im- aging devices, glaucoma specialists now have a variety of tools to use. "When anterior segment imaging became available, it was an emerging, promising technique that produced great images," said Nathan M. Radcliffe, MD, assistant professor of ophthalmology, New York University, New York. "The ophthalmic community let off the gonioscopy skills a bit because we were so certain that imaging was going to be the way of the future. But it hasn't evolved to the point where it replaces gonioscopy. Plus, a new era of microincisional glaucoma surgeries has become available for which intraoperative gonioscopy is a crucial skill." These procedures include trabecular micro bypass procedures (currently available), as well as forthcoming suprachoroidal microshunt procedures that will be placed into the ciliary body face via gonioscopic visualization. Parag Parekh, MD, MPA, in private practice, Laurel Eye Clinic, Brookville, Pa., does not use anterior segment imaging yet—as a surgeon with a predominantly cataract patient base, he does not yet see the need. "Gonioscopy is definitely the go-to procedure for me," he said, although his practice is evaluating adding an anterior segment imaging adapter to its new optical coherence tomography (OCT) machine. "If I had a greater percentage of severe/tertiary glaucoma patients in my practice, it might make more sense," he said. Dr. Radcliffe laments that more ophthalmologists do not regularly perform gonioscopy, but believes the pendulum may be swinging back. "The enthusiasm in treating glaucoma in the angle and the value of these gonioscopy skills will drive people back toward routine clinical gonioscopy," he said. "With anterior segment imaging, the images are beautiful. They are highly valuable for patient education because you can show the results to a patient and bring the diagnosis 'home' for them." For clinicians who want objec- tive documentation about angles, the latest imaging devices can be beneficial, but determining which treatment course to implement is likely going to rely upon go- nioscopy, both physicians said. A few exceptions include pathology behind the iris or in the iridociliary sulcus, such as plateau iris, iris cysts or malpositioned intraocular lenses, in which case ultrasound (but not anterior segment OCT) can be a great benefit. Then there is the issue of physical space, Dr. Parekh added. "With all the newer devices currently on the market, where to put the next piece of equipment can be a significant challenge." Advantages of the latest imaging devices Sometimes the hardest part of the disease for a glaucoma patient is understanding it, and that is where the latest imaging devices can help, Dr. Radcliffe said. "The images are fantastic for patient education. But we're not at a point yet where we can implement commercially available normative databases or use other automated algorithms to distinguish normal from abnormal." Imaging is still open to subjective interpretation, he said, much like gonioscopy. "Tertiary glaucoma specialists, for example at academic centers, will get referred these difficult cases the generalist can't figure out, and in my mind, these newer imaging devices might be more helpful for that type of glaucoma-heavy, referral prac- tice," Dr. Parekh said. Dr. Parekh is optimistic about the future of angle imaging, based on how OCT changed retinal practice. For example, before the advent of OCT, retina specialists lumped several macular diseases under one group as the nuanced differences were not easily seen, Dr. Parekh said. "Once OCT came into play, it gave us a whole new way to look at the macula," he said. "Imaging revolutionized our understanding of the macula. I would argue that OCT has changed how retinal specialists diagnose and treat all those diseases. And the glaucoma imaging devices may be able to do the same; only time will tell." Dr. Radcliffe cited the ability to use ultrasound biomicroscopy (UBM) in movie mode as an advan- tage over high definition anterior segment OCT, "but UBM requires an even more skilled operator than gonioscopy does," he said. "It's difficult to pass off the UBM image acquisition to a technician for a complex case; they're usually per- formed by fellows. If I'm going to interpret a UBM and make a treat- ment decision based upon UBM, I usually have to be the one who performed it." Outside the U.S., the EyeCam (Clarity Medical Systems, Pleasanton, Calif.) has shown "good agreement with gonioscopy for detecting angle closure," and it "detected more closed angles than did gonioscopy in all quadrants," according to research from the Singapore National Eye Center. The EyeCam provides a 2D view, whereas gonioscopy is 3D, Dr. Radcliffe said. "Other imaging devices are also 2D—the UBM, even OCT. Gonioscopy is the only 3D imaging device available." In time, however, Dr. Parekh said anterior segment OCT or UBM may be able to identify a patient's Device focus High definition anterior segment optical coherence tomography demonstrates an open angle (top) and an occludable angle with iridocorneal contact. Source: Nathan M. Radcliffe, MD