The Associated Press

Scores of blind people in California and Taiwan are seeing again through eyes refurbished in the laboratory.

The experimental technique - which involves transplanting lab-grown cells to replenish the cornea's surface - offers hope to hundreds of thousands of people around the world blinded by fire, chemical burns or certain diseases.

So far, the transplants are working for about 60 out of more than 90 patients operated on at Chang Gung Memorial Hospital in Taipei and 11 of 15 at the medical school at the University of California at Davis. Doctors do not yet know if the repair is permanent, but the patients' improved sight has lasted up to 15 months so far.

A report in Thursday's New England Journal of Medicine describes the results in the first six patients operated on in Taiwan by Dr. Ray Jui-Fang Tsai. Results from UC-Davis are described in the July issue of the journal Cornea.

Doctors already transplant cells directly from one person's eye to another to refurbish the cornea. But when that is done, the donor must give about half of the cells from the limbus, the circle where the clear cornea turns to white.

The new approach requires only a tiny sliver from the donor's limbus; those cells are then grown in a laboratory dish until ready for transplant.

"Long term, what's going to happen to the donor eye 20 or 30 years from now? We don't know," said Dr. Edward Holland, ophthalmology professor at the University of Cincinnati and director of cornea services at the Cincinnati Eye Institute. "This lets us take less than 5 percent of the cells from the donor eye and potentially - this is very early - but potentially get the same results.

"That's very exciting," he said.
The technique could help perhaps tens of thousands of people in the United States, as well as hundreds of thousands in developing nations where a disease called trachoma is common, said Dr. Neil F. Martin of the American Academy of Ophthalmology. Trachoma is one of the world's leading causes of blindness.

It will not help people who are blind from birth or those who lost their sight because of damage to the nerves or the retina. Nor is it for the totally blind; it is only for people who can still at least distinguish light and dark.

Many of the patients who underwent the procedure had been burned by fire or chemicals. Others had eyes scarred by disease or reactions to eye drops. Standard cornea transplants had not worked because the people did not have cells needed to grow a new protective covering over the cornea.

Some of those who could see only fingers or hand motion at about 16 inches could see well enough to drive after the transplants. Some could see clearly at a distance of a few inches. Other patients could see well from the start, but the white of the eye was growing toward the pupil, a condition that can cause blindness unless it is corrected.

For his first patients, and about 40 eyes in all, Tsai took cells from the patient's own healthy eye to repair the diseased eye. Virtually all of those transplants worked. He has also used cells from cadavers and from patients' relatives to create transplants for 54 eyes. About half of those worked.

The approach relies on what are known as epithelial stem cells - which grow replacements for the cells that cover the body's surface and line most of its hollows, such as the inside of the digestive system and lungs.

In a normal eye, epithelial stem cells in the limbus create new cells to replace dead corneal cells. If those stem cells are destroyed, the cornea can become scarred and opaque. The white of the eye may grow over the cornea.

Tsai's team took a slice eight-hundredths of an inch long from the limbus and put it in a lab dish on top of a piece of amniotic membrane, the thin film which holds the fluid around a fetus until birth. When the corneal cells had grown to about an inch across, Tsai removed the patient's damaged eye tissue and replaced it with the membrane and the new eye cells.

The UC-Davis team used a slightly different technique. Some of the UC-Davis patients also got transplanted corneas.

Dr. R. Rivkah Isseroff, the cell biologist in charge of the lab work at UC-Davis, said the only bioengineered replacement tissues now commercially available are skin, which is used to treat burns and chronic skin wounds, and cartilage, used for some knee injuries. Corneal surface tissue could become the third type available, she said.

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