U2 frontman Bono, 63, is known for his trademark, fashionable sunglasses, but the real reason behind the sexy shades is that the rocker suffers from glaucoma. Glaucoma is a condition in which high pressure inside the eye causes damage to the optic nerve.

Overall, there are about 2 to 3 million Americans living with glaucoma. These numbers are expected to increase in the future. The risk of glaucoma becomes higher as we age into our 60s, 70s, and 80s.  In addition, it can affect anyone regardless of gender or ethnicity. People with a family history may be more prone, so it is important to have regular checkups, says Dr. Wayne Tie, an ophthalmologist with the Kelsey-Seybold Clinic in Texas.

Glaucoma is a group of eye diseases that cause vision loss due to damage to the optic nerve. It’s the second leading cause of blindness in the U.S. and knowing the early warning signs — such as partial vision loss, eye pressure, and headaches — is important so you can see an ophthalmologist for timely treatment and to prevent further damage.

According to Health, there are several types of glaucoma which is caused by the buildup of aqueous humor, a fluid between the clear outer layer and the lens of the eye. The most common type is open-angle glaucoma, a primary form of the disorder, that usually doesn’t have symptoms early on. Loss of peripheral or side vision is one sign, but by this time the disease has progressed significantly, and vision loss is not reversible. Your best bet to prevent open-angle glaucoma is to have regular eye checkups.

Angle-closure glaucoma happens when the angle between the iris, the colored part of the eye, and the cornea, the clear outer layer of the eye closes. Symptoms include:

•Headache.

•Eye pain.

•Blurry vision.

•Redness.

•Nausea or vomiting.

•Seeing halos or rainbows around light.

If you are experiencing symptoms of angle-closure glaucoma, it’s important to see an ophthalmologist, says Health. If left untreated, this condition can damage the optic nerve and cause vision loss.

TREATMENT

“The treatment of glaucoma focuses on reducing eye pressure,” Tie tells Newsmax. “How much each person needs to be treated is dependent on the severity of glaucoma as well as the individual. Eye pressure can be controlled with eye drops, lasers, and surgery. Because everyone is different, one patient may benefit more from one type of treatment over another.”

Because glaucoma causes irreversible damage to the optic nerve, none of the treatments including eye drops or surgeries can recover the vision that has already been lost, explains Tie. “This is the reason why regular comprehensive eye exams are so important. Just like we use medications to treat blood pressure or diabetes to prevent future complications, we treat glaucoma in a similar way.”

If you have any other these symptoms, see and eye doctor promptly to avoid vision loss.