BATON ROUGE - It is World Glaucoma Day, a day that brings awareness to diseases that damage the optic nerve. It can result in vision loss and even blindness.

The CDC says only half of the three million Americans with glaucoma know they have it.

"Glaucoma in its early phases is really asymptomatic. People have no idea that they have it," Dr. David S. Friedman, Director of Glaucoma Service at Massachusetts Eye and Ear said.

Friedman says the first thing to know about glaucoma is that early detection is critical. A regular eye exam can help prevent damage and vision loss from the condition.

While anyone can get glaucoma, everyone over the age of 60, African-Americans over the age of 40, people with a family history of the disease and those who have diabetes have a higher risk.

There are several forms of glaucoma; open angle, which leads to increased eye pressure, and angle closure are the most common types. Both tend to run in families.

There is no cure for glaucoma, but there are treatments that help reduce pressure and preserve vision, such as eye drops, oral medicine or surgery.

The CDC says Medicare covers an annual glaucoma test for those at high risk of developing it.

"The strongest recommendation I can make is that as people are aging, they get routine eye care," Friedman said.