The experimental method can benefit patients suffering from "ocular surface failure" which may occur as a result of disease, chemical injury or burns, and may cause blindness and severe pain.
A small amount of the amniotic membrane that surrounds a baby in the womb is collected after a Caesarean delivery, and used to reverse damage. Mr Sheraz Daya, at the Queen Victoria Hospital in East Grinstead, West Sussex, has performed about 40 amniotic membrane transplants. "I've used it in patients with persistent epithelial [surface layer] defects and to restore the surface of the eye after a chemical injury or burn, and it works very well in these situations. The membrane certainly changes things, and we still don't fully understand why."
The technique is employed when the cornea, which is the transparent membrane covering the eyeball, loses its ability to make its own transparent skin. "In these patients, the inside of the eye is fine and the lens is clear. But because the limbal stem cells [responsible for regenerating the cornea] have been killed off by disease or chemical injury, ulcers develop on the cornea and they either won't heal, or they heal as an opaque membrane," says Mr Daya. "It's rather like having a room with a piece of paper over the window so that you can't see out. What we do when we use an amniotic graft is to peel the piece of paper away from the front of the window and replace it with a transparent membrane that allows the sight to return."
Dr Charlie Hunt, a research and development scientist, helped the North London Tissue Bank to set up the collection of "amnions" (amniotic membranes) last year. It has since supplied more than 30 grafts to seven centres in the UK.
"We are collecting between four and six amnions per year," says Dr Hunt. "One amnion can provide material for about 50 grafts, but the first six months after collection are a `quarantine period' - we have to wait six months from the time of donation to re-test the donor for HIV."
"When we need an amnion, the cord bank nurses find a suitable donor who is having an elective Caesarean and obtain consent. We carry out an extensive medical history and serological tests on the donor, and microbiological tests on the tissue to make sure it is not carrying any diseases."
Incredibly, the procedure was first attempted in the late Forties, when a London eye surgeon, Dr Sorsby, carried out 58 operations and wrote two papers on his work. However, it was not tried again until 1993. It is now increasingly popular. Since last spring, the consultant ophthalmologists Mr John Dart, from Moorfields Eye Hospital in London, and Mr Francisco Figueiredo, from the Royal Victoria Infirmary in Newcastle, have each performed half a dozen amniotic membrane transplants. A handful of other UK surgeons have also used the technique. In many cases, the only alternatives for the patients were accepting loss of sight or a corneal transplant, which has a high rejection rate.
Amaya Teague, 29, from Mid Glamorgan, was born with a condition that caused her corneas to deteriorate and her eyesight to worsen. In 1994, her eyesight was so poor that she could see fingers held up in front of her face, but very little else. She had a number of operations to try to thicken the cornea, including two amniotic membrane transplants. However, the operations were unable to offer a lasting solution. A third attempt in November last year proved more successful. Amaya was rushed to Queen Victoria Hospital, after the cornea in her left eye suddenly perforated. "I was looking at a chair and I could see it disappearing," she recalls.
Sheraz Daya performed a amniotic membrane transplant. "This time, her eye quietened down straight after surgery and she grew new epithelium, and it has been stable ever since," he says. "I've never seen her look so good. I have no idea why it worked the third time when it didn't before - we don't really know enough about how it works."
Amaya is delighted with the result. "Before, it was like looking through a misty window. Now everything is much clearer," she says. "It's given me more confidence in getting around. I can watch television, though I have to sit close to the screen, and I can even read some print in magazines without using a magnifier."