Because the original donor stem cells could usually be taken from the same patient, tissue rejection wasn t a problem. But the cell layer is so thin, Tsai explains, lifting the fragile cell layer, just a fraction of a millimetre thick, was as frustrating as trying to pick up a sheet of damp tissue paper. Worse, when scientists successfully moved the layer, the patient would sometimes be teased by a few days of clearer vision before the new corneal surface clouded over. The stem cells had not survived the transfer, and without them, the ordinary corneal cells, which only live for a couple of weeks, were not replaced when they died. Amniotic membrane, which nurtures and protects unborn babies in the womb, helps body tissues heal without scarring.
Scientists are able to obtain it when babies are born by Caesarian section.
Early in 1995 he put a layer of amniotic membrane in a lab dish, planted some stem cells in it and placed the dish in an incubator. Two weeks later, a layer of corneal cells had grown on top of the membrane. When Tsai transplanted it to a patient's eye, a difference was immediately obvious. The amniotic membrane held the layer together, making it far easier to move. The surgery complete, Tsai and his colleagues waited.