Crashing Through by Robert Kurson Page B

patients—a man who had suffered a chemical injury to one eye—in a new way. He transplanted a section of the edge of that patient’s healthy cornea onto the edge of the injured eye. The patient’s vision improved. Barraquer didn’t realize it, but he had performed a stem cell transplant. Science now knew that, somehow, the edges around the cornea were important to corneal health.
    Research along these lines was advanced in the late 1970s in Pittsburgh by Dr. Richard Thoft, who refined Barraquer’s techniques and also began transplanting the edges of cadavers’ eyes into patients. But it wasn’t until 1989, through the work of Drs. Kenneth Kenyon and Scheffer Tseng, that science fully understood the role of corneal epithelial stem cells and how best to transplant them. The process, it turned out, required two surgeries and a good deal of technical skill on the part of the surgeon.
    When a donor dies, an eye bank dispatches a volunteer to remove the donor’s eyeballs. The eyes are placed in a preservative solution and sent back to the eye bank, where the corneas and surrounding stem cell areas are cut from the eye and placed back in solution. They are then sent to a surgeon for transplantation, preferably within five days of the donor’s death. (Surgeons prefer to use corneas and stem cells from donors no older than age fifty.)
    The first surgery is to transplant the donor stem cells. After the patient is placed under general anesthesia, the surgeon scrapes away any conjunctiva cells and blood vessels that have grown on top of the patient’s cornea. That alone requires an artist’s touch, but the hardest parts are yet to come.
    The patient is left sleeping while the donor cornea and its surrounding doughnut of stem cells are placed under a nearby microscope. The surgeon uses that microscope—and a midnight-still hand—to cut away the center part of the donor cornea, leaving just the doughnut of stem cells. His job now is to place that doughnut on top of the patient’s existing cornea, thereby providing the cornea with a new supply of stem cells.
    In its current state, however, the doughnut is too thick to transplant. Still using the microscope, the surgeon thins the doughnut by shaving it from underneath, narrowing it from one millimeter to one-third of a millimeter, all without damaging the stem cells on top. His movements are a tiny ballet of precision and nerves.
    After the ring of stem cells has been thinned, the surgeon places it on top of the patient’s existing cornea and sutures it into place. The entire process takes between ninety minutes and two hours.
    The stem cell transplant by itself produces no vision. That’s because the patient’s existing cornea has been too badly damaged by overgrowing cells and blood vessels and no longer functions properly. He needs a new cornea, but before he can receive one, he must allow his new stem cells to produce waves of new daughter cells to forge a clear path to the cornea. Without that clear path, future protective daughter cells cannot reach a new cornea.
    It takes about four months for the daughter cells to clear that path. Once the surgeon confirms that this has occurred, he removes the patient’s damaged cornea and replaces it with a healthy cornea from a second donor. If all functions properly, that new cornea will be protected by the new stem cells and the daughter cells they produce. And that can mean long-term vision.
    By 1999, only fifteen or twenty surgeons in the United States had performed corneal epithelial stem cell transplants. It is likely that the procedure had been attempted fewer than four hundred times worldwide.
             
    May’s days stretched from dawn to midnight as August drew to a close. Still, during his free moments, he found himself digging. He called ophthalmologists to ask if they had performed corneal epithelial stem cell transplants—he wanted to know how Goodman’s experience ranked among his peers’. He could