Adult Stem Cells Offer New 
Hope in Some Cases of Blindness

April 22, 2003—Bethesda, MD: A little-known operation restores hope for people who lose sight from chemical or heat burns of the eye or certain rare diseases. The procedure, 50 to 100 percent effective in healing corneal damage, is used worldwide, including Iran, where it helps restore sight for victims of Iraqi mustard gas attacks.

A variation on corneal transplants, the surgery grafts stem cells from a donor or a patient's good eye to the injured eye. The cells are from the limbus, a rim around the cornea. The cells resheath the cornea's surface, the 50-micron-thick epithelium, to maintain it as a transparent window. When burns or disease wipe out the limbal stem cells, the epithelium clouds over with scar tissue, causing blindness.

Grafting even a small piece of limbus can lead the stem cells to regrow clear epithelium - and keep it clear - thus restoring sight. The cells even recover transplanted corneas. Stem cell transplants and corneal transplants are frequently performed one after the other if corneal damage extends below the epithelium.

The discovery of the cells 17 years ago and clinical proof that they keep working in any eye with an intact tear system has opened a new era in eye surgery.

"It's an outstanding breakthrough and has, at least in the short run, cured a number of patients," said Dr. Richard S. Fisher, director of the corneal disease program at the National Eye Institute in Bethesda, Md.

The stem cells are adult, not fetal tissue or embryonic, and join bone marrow and skin as the third adult stem cell in wide use to repair organs.

In the United States, officials estimate that 300 a year are performed and that the transplants are increasing because they are the sole alternative to plastic corneas for desperate burn cases, industrial accidents, damage from contact lenses and a few rare diseases that cause blindness. In operations on one eye, 90 percent to 100 percent restore vision, because the patients' own stem cells from the good eye can be transplanted without rejection.

In one eye, the surgery is "basically a slam dunk," said its originator, Dr. Kenneth R. Kenyon of Boston.

"When we first saw a number of challenging cases of mostly chemical burns," he said, "the eyes were chronically inflamed, with ulcers and blood vessels growing into the cornea, hallmarks, we now know, of limbal stem cell deficiency."

Stem cell transplants on one eye are now standard, said Dr. R. Doyle Stulting, editor of the journal Cornea. "They are clearly successful and they are permanent," Dr. Stulting said.

For patients blind in both eyes, stem cell transplants remain effective in half the cases after five years, principally because of rejection. Donor cells from eye banks or relatives are used, and surgeons report progress in those cases. Dr. Edward J. Holland, director of corneal services at the Cincinnati Eye Institute, has written the lone textbook on reconstructing the ocular surface. Last year, he announced results from 74 blind patients who received donor stem cells in both eyes.

Seventy-three percent developed clear new corneal surfaces. In patients with no other problems, that would have meant great vision. But for those complicated cases, half of whom had aniridia, the mean vision improved, from 20/1700 before surgery to 20/200 after surgery.

"Twenty/200 is legal blindness, but most aniridics can't get better vision," Dr. Holland said, because their retinas have genetic damage that cannot be repaired. "At 20/200, they can get around and read large print books with functional aids."