Bono is nearly unrecognizable without his trademark sunglasses. However, the U2 front-man's distinct look is more a product of necessity than styling.

He explained the shades to Rolling Stone and told them he uses the glasses to protect his blue eyes. "[I have] very sensitive eyes to light. If somebody takes my photograph, I will see the flash for the rest of the day," he said.

"My right eye swells up. I've a blockage there, so that my eyes go red a lot. A magazine across the pond was referring to me as 'old red eyes.'"

Bono also reacts to wine and other allergens that irritate his eyes and leaves them red.

"So it's part vanity, it's part privacy, and part sensitivity," he explains.

Bono first became associated with the sunglasses style in 1992, when he posed as a character called "The Fly" for a concert tour. He began wearing oversized shades to give life to the persona that represented the ultimate rock star. Naturally, the box set for U2's 20th anniversary of "Achtung Baby" will include a pair of replica shades.

There are reports that he's a fan of Emporio Armani sunglasses, but Bono has said he prefers Bulgari. "A lot of times, people think when they see a "B" on the side, it is just my own megalomania," he joked to Rolling Stone. "Only half the time it is."

"I'm the Imelda Marcus of sunglasses," he laughed.