U2 frontman Bono just revealed that he doesn't constantly wears dark sunglasses to add to his rock star image. He wears them to protect his eyes - because he suffers from glaucoma, a chronic eye condition.

"I have glaucoma," he told British talk show host Graham Norton. "For the last 20 years." Bono, 54, was on Norton's show with the rest of the band, as well as actors Robert Downey Jr., Robert Duvall and Stephen Fry, reports CNN.

Bono's revelation on the BBC's The Graham Norton Show came after Norton showed a couple of the group's early photos featuring Bono without spectacles. Noting the difference between Bono in 1980 and Bono today, the TV host asked, "Do you ever take (the glasses) off?" adds CNN.

Glaucoma is a condition that causes damage to the eye's optic nerve and is often associated with a buildup of pressure in the eye. The condition can make eyes highly sensitive to light and glare, with some glaucoma medications exacerbating the problem further. If left untreated, it can permanently damage the optic nerve and lead to blindness in some cases, reports People.

"I have good treatments and I am going to be fine," Bono stated on the TV show, reports The Independent.

He added with good humor: "You're not going to get this out of your head now and you will be saying 'Ah, poor old blind Bono.'"

He had previously said he wore his signature shades because he was "very sensitive eyes to light," adds The Independent.

"If somebody takes my photograph, I will see the flash for the rest of the day," he told Rolling Stone in 2005. "My right eye swells up."

Bono and his bandmates were on The Graham Norton Show to promote their newest album, "Songs of Innocence," which was released this week after previously being automatically added to 500 million iTunes customers' playlists - an unorthodox move that caused controversy among some iTunes users, according to People.