No more than 15 people in the world have so far undergone this revolutionary procedure - which involves what is called an intraocular retinal prosthesis. A probe is used to implant a 3mm silicon chip temporarily into the surface of the retina. When light strikes the chip it is converted into electrical impulses that travel through the optic nerve to the brain, which interprets it as an image.
The technique, which has been developed over the last 10 years, offers new hope for the blind. It is suitable for people of any age - but only if their sight loss has been caused by retinal damage.
"I have had this operation three times now," recalls Harold Churchey. "The first time was in 1992 at Duke University, North Carolina. A probe was used to insert a chip with one electrode in my right retina. The electrode sent signals to my brain that allowed me to see colours and lights during the test. It was left there for about 20 minutes. It was really exciting for me. When it was pulled out, I was back to square one and I couldn't see anything again. But I thanked the Lord, and I knew we were on the right track."
Two years later he had another operation, at the Wilmer Eye Institute in Baltimore. "This time, a chip with two electrodes was inserted into my retina. Again, I was able to identify colours."
In 1996 he had 25 electrodes inserted into his right eye. "They were shuffled around to form the letter "H" - for Harold _ in all its glory. It may not sound like much, but for me it was an amazing sight."
It took about 45 minutes. "Each time I could see a little more," claims Churchey. "And it wasn't painful, just a little uncomfortable. They don't use any anaesthetic - as I have to be able to communicate what I see and how it feels. But if you want sight, you'll put up with anything.
"They are now talking about putting 100 electrodes into my eye," he says. "Eventually, they hope to be able to insert enough electrodes into the retina so that the person can see a whole picture." These electrodes will be in electronic communication with a small camera mounted on the patient's glasses. In theory, images from the camera will be sent directly to the brain, via the electrodes on the implanted chip.
"My wife and I are very excited at the idea," enthuses Churchey. "And we both hope that some day I will be able to see again. Call me a medical guinea-pig if you want, but when you're blind, you'll try anything. And what else can happen? I have nothing to lose."
Joe Korner, a spokesperson for the Royal National Institute for the Blind, suggests that if the procedure is perfected in the US, "then perhaps the surgery will be available here in about 10 years' time". So will the blind be able to see? "It is too early to say," he cautions. "At the moment, experts in the UK believe that cell transplantation is a more promising technique."
The legendary soul singer Stevie Wonder, aged 48, is considering undergoing the procedure, so that he can see his four children. He recently announced the news at a church service in Detroit: "I am about to undergo an operation that helps the blind to become sighted, with the help of some sort of chip."
The star had apparently been inspired by Harold Churchey's experiences.
"Stevie Wonder heard about my story and wondered if he could get help, too," says Churchey. "He's like me - he wants to see his children. I understand that, and I wish him luck. It's my greatest wish to see my 11-year-old grandson."
However, Joe Korner of the RNIB warns Stevie Wonder - and anyone else considering having the surgery - that the technology is still at an early stage:
"There are few pros, apart from the research benefits, but there are many cons," he says. "The chip is a foreign body inserted into an extremely sensitive area of the eye. The surgery is invasive and if the procedure goes wrong, it is possible that the eye will be irreparably damaged. The side-effects are not yet known. At this stage, the best the surgery can offer is probably just light and dark perception."
But Harold Churchey is prepared to take his chances: "The next time the hospital calls me for another test, I'll be ready."
Call the Royal National Institute for the Blind on 0345 669999 or visit the Johns Hopkins University website: www.irp.jhu.eduReuse content