The rocker rarely removes his sunglasses in public, and he often wears shades with an orange, blue, or green tint, which he previously claimed was to protect his sensitive pupils.

However, he recently opened up about the real reason for his coloured lenses, revealing he has suffered with glaucoma for the past two decades, although he assured fans he will be "fine", thanks to the "good treatments" he's received over the years.

Now Bono is teaming up with executives at eyewear brand Revo and the non-profit Brien Holden Vision Institute for the Buy Vision, Give Sight campaign, which aims to raise $10 million (£6.25 million) to provide eye exams, glasses and other assistance to the disadvantaged around the world, in the hopes of preventing vision impairment and blindness in more than five million people by 2020.

Revo bosses have pledged to donate $10 (£6.25) from each pair of eyeglasses sold, while Bono will introduce his own collection with the firm this autumn (15).

In a statement released on Thursday (23Jul15), Bono says, "The 'Buy Vision, Give Sight' campaign is a very personal one for me. Thanks to good medical care my eyes are okay, but tens of millions of people around the world with sight problems don't have access to glasses, or even a basic eye test.

"Poor eyesight may not be life-threatening, but it dramatically affects your life and your livelihood if you aren't able to fix it. When we met with experts, they said the number one problem is untreated poor vision, which prevents a child from learning in school, or an adult from performing their job.

"Sight is a human right and the 'Buy Vision, Give Sight' initiative will help ensure millions of people have access to the eye exams and glasses they need to see."

Bono is currently modelling the new sunglasses range on the band's Innocence + Experience Tour.