U2 frontman Bono, 62, is known for his trademark, fashionable sunglasses, but the real reason behind the sexy shades is that the rocker suffers from glaucoma. This condition is caused by high pressure inside the eye, which can lead to long-term damage to the optic nerve. It is a leading cause of irreversible blindness in the world.

Overall, two to three million Americans have 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.  The condition 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 associated with the Kelsey-Seybold Clinic in Texas.

Bono says he’s suffered from glaucoma for the last 20 years, according to Eat This, Not That!  The condition makes his eyes more sensitive to light. “I have good treatments and I’m going to be fine,” he says. Experts say that most diseases that cause blindness, like glaucoma and diabetes, can be treated or slowed down if they’re diagnosed and managed properly.

According to the Cleveland Clinic, there are two kinds of glaucoma: open-angle and closed-angle glaucoma. Signs of open-angle glaucoma, which affects 95% of sufferers, tend to come on subtly and gradually, which makes them easy to miss. This makes it incredibly important to have routine eye exams to detect this disease, says Dr. Cary Silverman, a leading ophthalmologist and medical director of EyeCare 20/20 in East Hanover, N.J.

“Open angle glaucoma causes a slow insidious irreversible loss of vision. Unfortunately, there are no symptoms until late in the disease when most of this irreversible vision loss has already occurred. The trick here is semiannual eye exams which also screen for glaucoma,” Silverman tells Newsmax. “The aim is early diagnosis and treatment to prevent vision loss.”

Closed-angle glaucoma has more severe symptoms that tend to come on more suddenly. These include:

• Eye pain or pressure

• Headaches

• Rainbow-colored halos around lights

• Nausea and vomiting

• Red eyes

“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,” he says.