Revealed at last: Why Bono always wears shades - Glaucoma

Bono says he has been suffering from glaucoma for the last 20 years. "I have good treatments and I am going to be fine."

Bono, the U2 frontman, has revealed that he wears dark glasses all the time because he suffers from glaucoma.

The star said he has had the condition - a build-up of pressure in the eyeball, which can damage the optic nerve and lead to blindness if not treated - for around two decades.

Many had assumed his ever-present sunglasses - even indoors - were a rock star affectation, but he explained during a recording of the Graham Norton Show for BBC One that they are to help with his vision problem.

Glaucoma can make the eyes more sensitive to light, causing sufferers to use dark glasses to alleviate difficulties.

Presenter Norton asked whether or not the singer ever removes his shades, to which Bono replied: "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."

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

The Irish band were on the show to promote their new album, Songs Of Innocence, which was released commercially this week after previously being given away to half a billion iTunes customers, a controversial move which upset some people who said they did not want it automatically added to their music libraries.

Speaking about the furore, Bono told Norton: "We wanted to do something fresh but it seems some people don't believe in Father Christmas.

"All those people who were uninterested in U2 are now mad at U2. As far as we are concerned, it's an improvement."

Bono also addressed the iTunes issue in a Facebook Q&A with fans earlier this week. One of the questions posed was: "Can you please never release an album on iTunes that automatically downloads to people's playlists ever again? It's really rude."

The singer apologised and put it down to a "drop of megalomania, touch of generosity, dash of self-promotion and deep fear that these songs that we poured our life into over the last few years mightn't be heard".