AUG 2013

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

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August 2013 February 2011 Getting schooled on laser versus medicine Treatment for optic disc with glaucoma has been guided by findings from key glaucoma trials. Source: Steven L. Mansberger, MD some practitioners continue to ascribe to for glaucoma suspects with ocular hypertension alone. "If they have a relatively severe glaucoma, we'll shoot for a higher drop in intraocular pressure—sometimes 50%," he said. "When they have early or moderate glaucoma, it will be somewhere between a 20% and 50% drop in pressure." Also gleaned from OHTS was a risk calculator, profiling those who were more or less likely to develop glaucoma based on a numbers of factors, Dr. Kass said. "This looked at the patient's age, intraocular pressure, cup disc ratio, corneal thickness, and pattern standard deviation from the visual field," he said. "It said that if you look at these things as a group, you can estimate the five-year risk of someone developing glaucoma." Taking patient risk into account implied that those at high risk may benefit from frequent observation and early treatment, while those at low risk would be better served by being examined less frequently and maybe spared the cost, bother, and potential side effects of early treatment, Dr. Kass said. Dr. Spaeth thinks OHTS showed that physicians can affect the course of ocular hypertension in a way that means that fewer people are going to develop progressive disc or field damage. He cited a related study by Joseph Caprioli, MD, who found that the two most important determining factors in who will get worse are rate of visual field change and age. Meanwhile, in a study of his own, Dr. Spaeth found that rate of visual field change holds up well, but that age was not nearly as pertinent. However, he warned, treating at-risk patients does not necessarily mean they will improve as a result of care. "You can't make an asymptomatic patient better," he said. "Unless patients are going to develop enough field loss and eventually develop some kind of disability or decrease in quality of life, the effect that you're having on them by giving them medications is going to make them worse unnecessarily." Dr. Mansberger thinks that the OHTS risk calculator as to who is likely to develop glaucoma should serve only as a guide, with the choice ultimately made individually. "One of the papers from OHTS showed that it was more cost effective to treat patients for anything above a 10% level," he said. "But I think that it's up to the patient and the doctor to make the final decision of if that risk is high enough to treat." He stressed that it's the responsibility of practitioners to educate patients about the various options. Laser is an option that some patients consider initially instead of medication. The GLT (glaucoma laser trabeculoplasty) and SLT (selective laser trabeculoplasty) studies both looked at laser as an alternative to medical therapy, Dr. Katz said. The GLT compared use of argon laser trabeculoplasty (ALT) as initial therapy in one eye with medical therapy using timolol in the other. Investigators found that while there was a better chance of visual field and optic nerve stability when laser was used initially, this was not adopted in practice, Dr. Katz said. He thinks some of this may have had to do with the fact that medication in one eye can have a crossover effect in the other. Also, he pointed out that many practitioners are conservative and tend to be more comfortable using medications first. "It's easier to give medications and then if that fails, go to the laser," Dr. Katz said. The SLT study, which came after the GLT study, showed pretty much the same thing, Dr. Katz said, adding that he participated in a privately funded multicenter trial that substantiated the effect of lasers. "It confirmed what the GLT said in that the laser, whether it's argon laser or SLT, is a reasonable alternative to monotherapy as a start-up for glaucoma," Dr. Katz said. Dr. Spaeth said such studies haven't changed practice patterns since the medications studied were not necessarily the ones that practitioners are currently using. Also, he pointed out that for patients, the thought of using lasers can be scary. However, when he thinks it's time for laser therapy, he quotes these studies frequently, stressing that the treatment has been found to be safe and effective. Reading up on trabeculectomy versus medical therapy In regard to filtration surgery, CIGTS investigators considered whether it would be more effective to control new glaucoma patients with this approach or with medication. Dr. Katz said that the study showed that both were very effective in preventing any glaucoma progression. Patient target pressure was based on a formula that took into account starting EW GLAUCOMA 45 pressure and the severity of the visual field loss. "If you try and keep to that number, whether it's with medical therapy or surgery, you have a good chance of keeping that population stable," Dr. Katz said. Dr. Spaeth concurs that patients in both groups were helped. He pointed out that the benefits in both groups were not equal. "There was more of an initial visual decrease in patients who had surgery," he said, adding, however, that this group also had a greater initial fall in pressure. "I think what it established is not that initial surgery is better or worse, but quite the opposite," he said. "Specifically, you make the decision with your particular patient, with the understanding that whether you use drops or surgery, both are going to benefit the patient." Overall, Dr. Kass thinks the trials have clearly indicated that lowering intraocular pressure does protect patients with glaucoma. "It's not a cure-all," he said. "There are people who will still progress even at pressures that are substantially lower than when you started, but you can greatly reduce the rate of progression and help to protect people." EW Editors' note: Drs. Kass and Spaeth have no financial interests related to this article. Dr. Katz has financial interests with Aerie Pharmaceuticals (Bedminster, N.J.), Allergan (Irvine, Calif.), Alcon (Fort Worth, Texas), Bausch + Lomb (Rochester, N.Y.), Glaukos (Laguna Hills, Calif.), Inotek Pharmaceuticals (Lexington, Mass.), Lumenis (Yokneam, Israel), Merck (Whitehouse Station, N.J.), Sensimed (Lausanne, Switzerland), and Sucampo Pharmaceuticals (Bethesda, Md.). Dr. Mansberger has financial interests with Allergan, Merck, Alcon, Valeant Pharmaceuticals (Quebec, Canada), Bausch + Lomb, Sucampo, and Liquidia Technologies (Research Triangle Park, N.C.). Contact information Kass: 314-362-3937, Kass@vision.wustl.edu Katz: 215-928-3197, ljkatz@willseye.org Mansberger: 503-413-6453, smansberger@deverseye.org Spaeth: 215-825-9020, gspaeth@willseye.org

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