EyeWorld Asia-Pacific September 2012 Issue

47 September 2012 EWAP GLAUCOMA An eye with both a cataract and elevated IOP. A recent study examines the long- term effect of phacoemulsification on IOP. Source: Pekka Virtanen Is cataract surgery alone enough? by Enette Ngoei EyeWorld Contributing Editor EyeWorld talks to the authors of two important papers on lowering IOP with cataract surgery S afety and efficacy in performing combined procedures on patients with cataract and glaucoma have led many surgeons to do separate surgeries. David S. Friedman, MD, Alfred Sommer Professor, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Md., USA, and author of the study “Surgical strategies for coexisting glaucoma and cataract; an evidence-based update,” said that in cases where patients have significant cataract and borderline pressure control, many clinicians are now taking out the lens only and performing glaucoma surgery later. When surgeons think of combined procedures they like to think “save the conjunctiva,” Dr. Friedman said, because “the results of our [2002] literature review showed that when you look at the overall outcomes of combined trabeculectomy and cataract surgery, the pressure lowering effect is less than trabeculectomy alone.” The question is, will taking out the cataract now and doing the trabeculectomy in 3 months produce better results? No one has done a trial comparing that approach to the straight combined approach, said Dr. Friedman, but there are arguments for the former being better because after that period of time, the inflammation should go down and bring pressure back to baseline levels. The ongoing debate about whether cataract surgery alone is enough to bring about a significant decrease in IOP is an important one. In 2002, Dr. Friedman and colleagues assessed short- and long- term control of IOP with different surgical treatment strategies for coexisting cataract and glaucoma. Published in Ophthalmology , the study was mainly a large case series, looking at IOP pre- and post-op. The study reported that evidence was good that long-term IOP is lowered more by combined glaucoma and cataract operations than by cataract operations alone. On average, Dr. Friedman said, patients with angle-closure glaucoma who had cataract surgery alone had a pressure decline of about 1 mmHg or 1.5 mmHg at about 1 year. “As there weren’t a lot of studies about patients with open- angle glaucoma, the actual number of those is harder to tell, but it seemed like it was also in a similar range,” he said. Higher pressure, larger effect “In terms of angle-closure, there’s been a wide variability in reports about how much cataract surgery controls eye pressure. My take on a lot of the literature is if the patient starts at a higher pressure, surgery tends to bring the pressure down a bit,” Dr. Friedman said. He described a large study from Hong Kong that compared phacoemulsification alone versus combined phacotrabeculectomy in medically controlled chronic angle-closure glaucoma (CACG) with coexisting cataract. Published in Ophthalmology in 2008, the randomized clinical trial showed that there was pressure lowering post-op and in the 1-1.5 mmHg range, but those patients started with a baseline pressure of around 18 mmHg. Dr. Friedman said, “So again when you start relatively low, there’s not that far to go. Removing the lens isn’t going to make [IOP] go down a lot in those patients.” Dr. Friedman described a study by Bradford J. Shingleton, MD, and colleagues that looked at the effect of phacoemulsification with posterior chamber IOL implantation performed by a single surgeon on IOP and glaucoma medication requirements in pseudoexfoliation (PFX) eyes with or without glaucoma. The study showed very large declines in pressure especially in instances where the pressure was high, Dr. Friedman said, and there was an association with the amount of pressure decline with the level of IOP elevation pre-op. Mixed evidence According to Peter Ta Chen Chang, MD, Vanderbilt Eye Institute, Nashville, Tenn., USA, “The most compelling evidence of the IOP-lowering effect of cataract surgery is in the population of untreated ocular hypertensive patients (patients with elevated IOP without evidence of progressive optic nerve damage), as demonstrated by the recent publication by Dr. Mansberger and the Ocular Hypertension Treatment Study Group.” Dr. Chang, lead author of an important recently published study that investigated the long- term effect of phacoemulsification on IOP in patients with ocular hypertension and open-angle glaucoma, said that outside of this untreated ocular hypertensive patient population, the evidence on the IOP-lowering effect of cataract surgery is mixed. Dr. Chang’s study retrospectively reviewed the medical records of 29 individuals with either open-angle glaucoma or ocular hypertension in both eyes who had uncomplicated phacoemulsification in one eye; the other eye remained phakic for at least 3 years, he said. “We compared the IOP between the surgical and fellow eyes both before and at several points after the cataract surgery. We found no statistically significant differences in both the IOP and number of medications used between the surgical and fellow eye at any of these points up to 3 years post-op,” Dr. Chang said. The EAGLE study For primary angle-closure glaucoma patients, there may soon be enough evidence to support whether or not cataract surgery alone decreases IOP significantly. The EAGLE study, a multicenter randomized trial to evaluate whether early lens extraction improves patient-reported, clinical outcomes and cost-effectiveness, compared with standard care, is under way. While data won’t be filed for several years, Dr. Friedman said there’s enough preliminary evidence to support doing the study to look at whether just removing the lens early, even if the lens isn’t cataractous, might prevent further worsening of angle- closure glaucoma. continued on page 48