But now the Grammy winner, 54, is revealing a surprising reason for his shady look: glaucoma, a chronic eye condition.
The Irish singer made the surprising admission during a recent taping of BBC1's The Graham Norton Show, telling the host, "This is a good place to explain to people that I've had glaucoma for the last 20 years. I have good treatments and I am going to be fine."
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.
"You're not going to get this out of your head now and you will be saying, 'Ah, poor old blind Bono,'" cracked the Rock and Roll Hall of Famer.
Bono and his bandmates were on the 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.
"We wanted to do something fresh, but it seems some people don't believe in Father Christmas," Bono told Norton. During a Facebook Q & A session on Tuesday, he admitted the band may have gotten "carried away" with the unconventional iTunes approach.
"Artists are prone to that kind of thing," he said. "Drop of megalomania. Touch of generosity. Dash of self-promotion."