U2 frontman Bono revealed Friday that the real reason he wears sunglasses is because he suffers from glaucoma.
The 54-year-old singer said he has lived with the condition -- which is caused by increased pressure in the eyeball causing gradual loss of sight -- for around two decades.
Glaucoma can make the eyes more sensitive to light and sufferers wear sunglasses to ease the condition.
Commentators have long assumed Bono's trademark shades -- oversize and in different tints -- were part of his rock star image.
"This is a good place to explain to people that I've had glaucoma for the last 20 years," the Irishman told BBC television.
"I have good treatments and I am going to be fine," he said, adding: "You're not going to get this out of your head now and you will be saying 'Ah, poor old blind Bono'."
Bono also addressed the controversy over the decision to give away U2's new album, "Songs of Innocence," for free through iTunes, saying: "We wanted to do something fresh but it seems some people don't believe in Father Christmas."