Could you be losing your vision and not know it?

It’s a leading cause of vision loss worldwide and many people don’t realize they have it until some damage is already done.

Glaucoma, a disease that damages the optic nerve, typically causes loss of peripheral vision before it causes central vision loss.

“That’s an important characteristic to note because probably about half of the people who have glaucoma don’t realize it,” says Dr. Kathryn Bollinger, an ophthalmologist at the Medical College of Georgia at Augusta University and AU Health. “It can be very difficult to recognize that you are losing your peripheral vision. The best way to find out if you have glaucoma or are at risk of developing it is to visit your eye doctor.”

During a basic eye exam, an ophthalmologist will dilate the eyes to get a better look at the optic nerve and look for any damage. They also measure intraocular pressure, the fluid pressure in the eye. Those with high pressures are typically thought to be more at risk for glaucoma, though that is not a hard and fast rule, Bollinger says. “There are some people who have high pressure who never develop glaucoma, and there are people with low pressure that do,” she says. Basic glaucoma screenings also involve a vision field test to measure peripheral vision.

Yearly, dilated eye exams should become part of regular health maintenance, particularly after age 40, according to the American Academy of Ophthalmology, but “someone who has some risk factors for glaucoma is generally evaluated a little more frequently,” Bollinger says.

Risk factors, other than increased intraocular pressure, include a family history, past trauma to the eye and chronic use of corticosteroids, to control conditions like rheumatoid arthritis for instance, but which also raise eye pressures. Diabetics can also be more at risk for developing the disease, which affects 3 million people in the United States alone.

Most of those 3 million people are diagnosed with open angle glaucoma. This most common type of the disease typically occurs when the outflow tracks that allow for the flow of aqueous humor — the clear fluid that fills the front of the eye, between the lens and the cornea — are physically open but malfunctioning. “We don’t fully understand why,” Bollinger notes.

Closed angle glaucoma — rare and more severe — occurs when the outflow tracks are, as the name indicates, closed. It can occur suddenly and cause pain and immediate vision loss. In both types, the excess aqueous humor raises intraocular pressure, which is what ultimately damages the optic nerve.

For both types of the progressive disease, current treatments include medications that either  lower pressure, decrease the formation of the aqueous humor or improve outflow of fluid from the eye. “There are several categories of meds and there are new meds that have come out in recent years,” Bollinger says. “So there are choices.” Surgery can also improve outflow.

January is National Glaucoma Awareness Month.

Bollinger is a glaucoma specialist and retinal cell biologist in the MCG Department of Ophthalmology and the Culver Vision Discovery Institute. She also is principal investigator on a $1.8 million grant from the National Institutes of Health aims to develop novel treatment strategies for protecting the optic nerve from the damage caused by glaucoma.