Glaucoma is damage to the optic nerve of a person’s eye that is related to increased pressure. There are usually no perceptible symptoms, but it can render a person blind. Fifty percent of people with glaucoma in the United States don’t know they have it. The disease affects 1 to 2 percent of the world’s population. Some people are born with it. Others develop it. It affects infants – it occurs in one of every 10,000 births – as well as middle-aged folks and the elderly. It also becomes more prevalent as we get older. By age 80, one in 10 Americans will be diagnosed with glaucoma. The eye contains a clear fluid called aqueous humor. It is a form of ultra-filtrated blood, stripped of its color, which is generated by the ciliary body. The fluid streams into the inner part of the eye to nourish the lens, the cornea and trabecular meshwork, and there’s a rapid and constant flow. Every 100 minutes there’s a complete turnover of the aqueous fluid. The fluid drains out through the eye’s trabecular meshwork. In glaucoma cases, however, that drain becomes plugged with debris and pressure builds within the inner eye. Pressure is measured with an instrument called a tonometer, and a reading of 10 to 21 mm Hg is generally considered normal. But checking the pressure isn’t enough. Patients with normal tension readings may still develop glaucoma if the pressure is too high relative to their optic nerves. In fact, 30 percent of glaucoma patients have “normal tension” glaucoma. To ensure the absence of glaucoma, you should ask your eye doctor to evaluate the optic nerve for damage. Glaucoma runs in families. In fact, if someone in your immediate family has glaucoma, your risk of contracting it is eight times higher than the general population. Race, for reasons we don’t understand, also appears to be a risk factor: African Americans are four to five times more likely to contract glaucoma. And the risk of going blind from glaucoma among African Americans is eight times higher than average. Other health issues such as diabetes and hypertension also increase the risk of glaucoma. There is no cure for glaucoma – only treatments. Usually it is first treated with medicines. Today’s medical therapies are better than ever. However, prescription eye drops can cost patients as much as $1,000 to $2,000 per year. Some medicines decrease production of aqueous fluid, others increase drainage. Often they’re given in combination. If medicines don’t work, a doctor may add laser treatment or surgery. To reduce the risk of blindness from glaucoma, a person should get a complete eye exam, including a pressure reading and an optic nerve evaluation, administered by an ophthalmologist or medical eye doctor. A check up at age 40, and every five years thereafter, is probably sufficient for those without any risk factors. Those with risk factors should see an ophthalmologist sooner and more often. Dr. J. David Brown is an associate professor of ophthalmology and part of University of Minnesota’s glaucoma service. This column is an educational service, and advice presented should not take the place of an examination by a health-care professional. To ask a health-care expert at the university a question, or for more health-related information, go to www.healthtalkandyou.com/.
