EyeWorld Asia-Pacific September 2014 Issue

22 EWAP GLAUCOMA September 2014 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 structural 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 importance of multi-modal testing in our glaucoma patients. Currently, no single tool or test has a high enough sensitivity and specificity for glaucoma 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 damage 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 “establishing 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 progression. 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 following 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 be missing a slow but real progression.” Be vigilant about resetting those baselines, too. If a patient has undergone cataract surgery, the VF may improve slightly so that may become the “new” baseline. Similarly, a patient who had been lost to follow-up and without drops for any length of time will likely have progression and need a new baseline. Dr. Noecker added the more advanced a patient’s glaucoma, the more likely he is to rely upon VF assessment. “I rely heavily on what the end-stage patients tell me,” he said. “They’re usually very sensitive to visual changes. At that point, they’ve lost so many ganglion cells already, you won’t be able to detect a change as easily.” In the future, however, the goal of functional assessment has been to move to something more objective than VF, Dr. Cantor said. “The goal is to take the patient’s thumb out of the process.” Electrophysiology may offer objectivity, but has been limited by reproducibility and signal-to- noise ratio. “There’s still work to be done,” Dr. Cantor said, but “hopefully, we’re going to be able to isolate the signal from the eye in order to assess retinal ganglion cell function.” Ongoing work is attempting to correlate what is being seen with electrophysiology with structural changes to determine the status of glaucoma suspects, he said. If successful, electrophysiology “may be less prone to artifacts than regular VFs,” Dr. Noecker said. Diagnosing structural damage Evaluating the optic nerve structure at the time of the initial examination coupled with stereo disc photography “will always be useful,” Dr. Liebmann said, and referring back to that original photo will help assess damage as well. These days, most specialists use spectral-domain (SD) OCT technologies, but Dr. Cantor said the “fundamental” problem with OCT is “the technology keeps progressing so rapidly that our ability to understand what it presents and the development of analysis packages of software to analyze it and understand it can never catch up.” Once validation studies have been completed, researchers are using the next generation machines, he said. While swept-source and even SD-OCT is “quite promising, it still needs further validation in longitudinal trials to help us determine what changes constitute glaucomatous changes vs. natural aging,” Dr. Samuels said. “A completely objective test that could identify damage prior to having functional field loss would be ideal.” Once damage gets too advanced, “sometimes the SD-OCT doesn’t help you,” Dr. Liebmann said. “You’re more dependent on the functional aspect.” For glaucoma specialists, determining whether progression is related to glaucoma or another eye disease is not trivial, Dr. Samuels said, “especially when the disease often progresses quite slowly.” “You have to use everything available to you because there is no one magic thing that works on every patient to diagnose progression,” Dr. Noecker said. Bottom line? “The yardsticks that we have to measure progression are still crude and we need better,” Dr. Cantor said. EWAP Editors’ note: Drs. Noecker and Samuels have no financial interests related to their comments. Dr. Cantor has financial interests with Allergan (Irvine, Calif., U.S.), Bausch + Lomb (Bridgewater, NJ, U.S.), Liquidia Technologies (Research Triangle Park, NC, U.S.), Mati Therapeutics (Austin, Texas, U.S.), Mobius Therapeutics (St. Louis, Mo., U.S.), and Aerie Pharmaceuticals (Bedminster, NJ, U.S.). Dr. Liebmann has financial interests with Alcon (Fort Worth, Texas, U.S.), Allergan, Diopsys (Pine Brook, NJ, U.S.), Merz (Frankfurt, Germany), Optovue (Fremont, Calif., U.S.), and Quark Pharmaceuticals (Fremont,Calif., U.S.). Contact information Cantor: lcantor@iupui.edu Liebmann: jml18@earthlink.net Noecker: noeckerrj@gmail.com Samuels: bcsamuel@uab.edu POAG - from page 21