Running blind: seven marathons, seven continents, seven days

The day Dave Heeley fell down a hole in the road, he realised that he badly needed a guide dog. Until then, he had done his best not to draw anyone's attention to the fact that the world was darkening around him because of a degenerative eye disease.

His first dog, as he puts it "opened his eyes", and since its arrival he has turned his life into a mission to create publicity and raise funds for the charity Guide Dogs for the Blind.

In just over six weeks' time, he will set out to achieve a feat of endurance that many professional athletes would find overwhelming. He proposes to run seven marathons, on seven continents, on seven successive days.

There are only two men – the polar explorers Sir Ranulph Fiennes and Dr Mike Stroud – who have ever achieved this and they both could see where they were going. "Blind Dave" – as he is inevitably known to other runners – will need to be accompanied throughout by his friend and "seeing" runner Malcolm Carr.

The pair are currently running 20 miles every other day. On their "rest days", they try exercise such as pool running – which is hard work but puts less pressure on the joints.

Watch Dave Heeley in action

The 777 test will begin in Port Stanley, on the Falkland Islands, on Monday, 7 April. On Tuesday, it will be Santiago, the capital of Chile; Wednesday, Los Angeles; Thursday, Sydney; Friday; Dubai; Saturday, Nairobi, the capital of Kenya. The grand finale will be the Flora Marathon in London on Saturday 13 April.

In total the pair will run 183.4 miles in one week – 26.2 miles each day – in Antarctica, South America, North America, Australasia, Asia, Africa and Europe. They will have to snatch as much sleep as they can on flights, with the occasional short break in a hotel room, and overcome problems such as jet lag and contrasting climates and time zones.

The feat is all the more extraordinary for the fact that Mr Heeley, 50, did not take up serious running until he approached middle age. He was born with the degenerative eye disease retinitis pigmentosa. His sight began failing in childhood and deserted him entirely in his teens. He studied carpentry at a college for the blind, and would work today as a professional carpenter if he could. But he pointed out: "If you're over 40 it's difficult to find a job, and if you're over 40 and blind, nobody wants to employ you."

In November 2006 he ran the New York marathon in three and a half hours – accompanied, as always, by a sighted guide who needs to be as fit as he is. So far, he has amassed pledges for the 777 attempt worth just over £8,000. Ultimately he hopes to raise £100,000 and already he has backing from his local council in West Bromwich, in the West Midlands.

"We probably won't ever know exactly how much we have raised, because the fundraising will be going on for years and years. Hopefully, it's going to be a continuous income. It's also not just about money, it's about raising awareness," he said.

"Around the world, every five seconds, someone loses their sight. Having suffered sight loss, I know how terrifying life can seem. I have been fortunate to have had my life transformed by guide gogs, which is why I am determined to create awareness of visual impairment worldwide."

Sir Ranulph Fiennes said: "Dave's inspirational effort is made all the more extraordinary by the fact that he's blind – further pushing the boundaries of human endeavour."

To make a donation, visit www.justgiving.com/777