Eyeworld

EW GLAUCOMA 56 by Maxine Lipner Senior EyeWorld Contributing Editor Factoring age into the glaucoma equation Are older eyes destined for glaucoma? I t's a well-known fact that the older patients are, the more likely they are to have glau- coma, but are tissue changes related to aging part and parcel of the disease process? In an article e-published in the January issue of Current Aging Science, investigators explored the role that such tissue-re- lated changes may play here. Nils A. Loewen, M.D., Ph.D., assistant professor of ophthalmology and visual science, Yale University School of Medicine, New Haven, Conn., saw it as natural to review the recent literature on this. "We're an aging society with an ever-ex- panding life expectancy, and as a re- sult of that, more people are developing glaucoma because it is typically something that affects peo- ple after the age of 50 or so," Dr. Loewen said. "The question is why is glaucoma increasing in the elderly population? There is no good answer to this." Two key theories To better address this, Dr. Loewen thinks it is important to consider what is involved in developing glau- coma. "Glaucoma is typically an ele- vated eye pressure that damages the optic nerve and then reduces the vi- sual field," he said. "But why is this increasing with age?" Currently two possible theories predominate. One centers on the outflow of the eye continuing to decrease as patients get older. The other theory revolves around the idea that the optic nerve becomes more susceptible to pres- sure fluctuations. "There are many studies trying to address either one—making the optic nerve more robust, or trying to prevent outflow failure or making outflow more effi- cient," Dr. Loewen said. In considering the literature, in- vestigators determined that aging plays an important role in glaucoma development. "The key finding is that aging itself is a factor—a causative factor, not just a correla- tion," Dr. Loewen said. "We can say this because the incidence of glau- coma increases disproportionately as we get older while the eye pressure goes up more or less in a linear way." As a result, investigators noted that there's an almost exponential up-tick in the incidence of glau- coma, while the increase of pressure that doctors primarily see as the cause of glaucoma is linear. "This implies that there is another factor involved that's causing the onset of glaucoma," Dr. Loewen said. From an evolutionary stand- point, Dr. Loewen thinks it makes sense that an eye disease that people weren't made to outlast might even- tually develop. "Our life expectancy was around 25 or 35 years, even 100 years ago, and now we live 70 years on average. With that we manifest things for which there was no selec- tion pressure," he said. "There was never any selection pressure to opti- mize an outflow system in the eye that could last 100 years." He pointed out that until recently, hu- mans only needed their eyes to hunt prey and escape enemies or wild ani- mals for maybe 40 years. Anti-aging therapy Determining specifically what may be occurring with age to spur glau- coma is not easy. "It's hard to figure out what's causing this other than saying that age is causing a failure of the outflow," Dr. Loewen said. What can we do about it? Even without knowing for certain what is occur- ring, Dr. Loewen pointed out that it is possible to look for specific signs of stress that may indicate chronic inflammation in the aging outflow track. "The trabecular meshwork is the structure that allows the drainage in the eye, and there's this chronic in- flammation," Dr. Loewen said. "The back of the eye has altered biome- chanics—the optic nerve cannot easily give in to the pressure fluctua- tions that occur." Going forward, the real question becomes what can be done to head this off. "Chronic inflammation is bad, and some doctors think we have to treat chronic inflammation or up-regulate a very fashionable set of genes," Dr. Loewen said. There's some thinking that resveratrol found in red wine may help by activating a set of genes called sirtuins, which have been implicated in influencing aging. "Some people take pills think- ing that they will live longer, and this actually seems to work in mon- keys and mice," Dr. Loewen said. "Humans are not too far away from the monkey, so perhaps the pills would also preserve outflow." EW Editors' note: Dr. Loewen has no finan- cial interests related to his comments. Contact information Loewen: 203-533-1004, nils.loewen@yale.edu February 2011 April 2011

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