DURHAM, N.C. (WNCN) — Glaucoma is often considered the sneak thief of sight.

More than three million people in the United States are living with it.

“Glaucoma is a disease of the optic nerve which is a cable that connects the eye to the brain,” Duke Health Glaucoma Specialist Dr. Jullia Rosdahl said.

As part of Glaucoma Awareness month, health experts are raising awareness about the disease, that often shows no early symptoms.

“It’s affecting their side vision very slowly, so they don’t even realize they’re losing vision until it’s quite advanced,” Rosdahl said.

Glaucoma can affect people of all ages, but certain groups are at higher risk.

“The older you get, the more common glaucoma is,” Rosdahl said. “African Americans, Hispanic Americans, those folks are at higher risk as well. If you have had eye trauma in the past or some medications, like needing a lot of steroid medications, those are some other risk factors for glaucoma.”

That’s why doctors encourage people to take steps now to protect their vision health.

“Getting that complete dilated eye exam on a regular basis, knowing your family history, it runs in families. If you yourself have glaucoma, tell your family members so they can get their eyes examined,” Rosdahl said.

Rosdahl also suggests protecting your eyes from trauma by wearing safety glasses when doing yard work or using tools. Also, wear sunglasses.

“And then taking care of your whole body,” Rosdahl said. “A heart-healthy diet, exercise, getting enough sleep, being with people you care about, all of those things help your body and help prevent glaucoma.”

There is no cure for glaucoma, but medication and surgery can help prevent further vision loss.