DURHAM, N.C. — Vision that's like a race horse with blinders on is one of the first symptoms of glaucoma. Peripheral or side vision fades away.

"I noticed some eye problems when my vision was bleary," said glaucoma patient Charlene Harmon-Barbee. "I couldn't see that well, and the redness in my eye was a burning sensation."

Harmon-Barbee learned she had glaucoma six years ago. It's a disease of the optic nerve that's associated with increased pressure inside the eye.

"Increased pressure is sort of like stepping on a garden hose, where it prevents the flow of nutrients and growth factors," said Dr. Stuart McKinnon with the Duke Eye Center.

The optic nerves eventually die. McKinnon said the high pressure inside the eye can be lowered with eye drops or laser treatments. Neither worked well for Harmon-Barbee's advanced stage of glaucoma.

"So we actually had to perform surgery to get those pressures down, and now she's doing very well," said McKinnon.

But the vision she's lost won't ever return. That's why, McKinnon said, early detection with an eye exam is so important for those at high risk.

They include most people over age 60. Blacks and Hispanics should get screened even earlier, by age 50. Anyone with a family history of glaucoma, the very nearsighted, diabetics, and those with high blood pressure should also get early sceening.

Harmon-Barbee needs frequent exams to maintain the vision she has.

"You want to go to church and do things for yourself," she said. "You want to be an independent person, not a dependent."

McKinnon is researching a possible link between Alzheimer's disease and glaucoma. An Alzheimer's drug called nemantadine is now in clinical trials to see if it helps glaucoma patients.