The 52-year-old singer has revealed in the past that he wears his ever present sunglasses because his eyes are sensitive to light, reported Daily Star.
"Bono actually has a condition with his eyes. I don't know the exact issue but the brightness of the sun hurts them and it's a deteriorating issue," Julian Lennon, son of late Beatles legend John Lennon, said.
Lennon said that the sunglasses have now become an integral part of Bono's image too.
"It's part of his image so in some senses it was lucky but nor really of course. Maybe it's part of his process now and without the image he can't be Bono," Lennon added.
Speaking about his eye condition previously, Bono admitted that he has to be careful when being photographed by fans and paparazzi.
"I have very sensitive eyes to light. If somebody takes a photograph, I will see the flash for the rest of the day. My right eye swells up," Bono had said.