Glaucoma can sneak up on you

Glaucoma often not detected until severe

Today and tomorrow, people can get free glaucoma screenings. (See Health Notes below.) According to the Glaucoma Research Foundation, as many as 4 million Americans have glaucoma, but only half know it.

High-risk groups, according to the National Eye Institute, include African-Americans over 40; everyone over 60, especially Mexican-Americans; and people with a family history of glaucoma.

Dr. Francis A. La Rosa at Virginia Eye Institute talked about the eye disorder in advance of the screenings.

Q. What is glaucoma?

A. "Glaucoma is a disease of the optic nerve of the eye."

Q. Is the eye-pressure test where you get the puff of air to the eye the best way to detect it?

A. "The eye pressure is the easiest thing to measure, and it's the single greatest risk factor. But fully 10 percent of people in this country have glaucoma and never have a high eye pressure. In fact, there is a category we call normal tension glaucoma. If you just rely on pressure, you are going to miss all of those patients."

Q. What are other ways to detect it?

A. "The health of the optic nerve trumps everything else. An experienced observer who looks at the optic nerve in an exam will know what to look for and can tell what might be a diseased optic nerve from one that is healthy. Then we have ancillary tests we do that include pressure and something known as a visual field test, and some automated testing these days that measure the thickness of the tissues that make up the optic nerve that also give us clues to the diagnosis of glaucoma."

Q. Are there any symptoms?

A. "Not until the end of the disease. In the most prevalent form of open-angle glaucoma, the disease is symptom-free until enough vision is already lost that the patient complains of poor vision. At that point, most folks are in the advanced stages.

"There are some acute forms of glaucoma that do present with symptoms. They are less common, but there are a fair number of folks that have an acute form." Symptoms include an acutely painful eye with a headache that surrounds the eye and rainbow-colored halos around sources of light, he said.

"Sometimes they will even be nauseated and having vomiting. If you are waiting for those symptoms, the preponderance of folks with glaucoma will be missed."

Q. Does an annual eye exam routinely check eye pressure?

A. "The annual eye exam will check for pressure, but again pressure is not the be-all and end-all."

Q. What should people in risk groups be doing?

A. "The recommendations for screening will depend on multiple factors identified at an initial exam. They should be seen by someone who treats glaucoma or is at least familiar with glaucoma and have a dilated examination to look at the health of the optic nerve."

Q. What kind of blindness does it cause?

A. "Glaucoma can result in total blindness. It's not like switching a light on and off. The way that it works, the visual field is constricted. It's very difficult for most people to detect on their own. . . . There are lots of subtle things impacted as well. Contrast sensitivity, color perception and the time that it takes an eye to adapt from brightness to a dark room are dramatically delayed."

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