NEW YORK, Jun 02 (Reuters Health) -- A new procedure that transplants tissue from around a donor cornea -- the transparent membrane covering the lens -- can restore useful vision in some people blinded by cornea diseases or trauma, report Japanese researchers.
Dr. Kazuo Tsubota from the Tokyo Dental College in Chiba, Japan and his team performed the surgery, called epithelial stem-cell transplantation, on 43 eyes in 39 people for whom surgery was a last resort after medical therapy had failed.
These patients were not candidates for standard corneal transplantation because they had lost stem cells that give rise to the outer covering of the cornea, the epithelium. The loss of these cells leads to overgrowth of blood vessels into the cornea, obscuring vision. In the new technique, these stem cells are replaced, using cells from donated corneas.
"The overall success rate," the authors write, "...was 51 percent. Thirty-five percent of the corneas became completely clear."
On average, "visual acuity improved from counting fingers to vision sufficient to distinguish the largest symbol on the visual-acuity chart from a distance of 1 meter," according to the report published in the June 3rd issue of The New England Journal of Medicine. "The 15 eyes in which the corneas became clear had (on average)... the ability to distinguish the largest eye-chart symbol from a distance of 5 meters."
"Severe ocular-surface disease causes loss of vision in thousands of patients in the United States each year," according to an editorial published in the same issue of the Journal.
In the editorial, Drs. Edward Holland and Gary Schwartz from the University of Minnesota in Minneapolis, remark on the significance of the new procedure. "To those not in the field, these results may appear unimpressive," they write. "However, without epithelial transplantation, none of these patients would have had clear corneas. All would be functionally blind."
"Epithelial stem-cell transplantation appears to be potentially beneficial for patients with a wide variety of ocular-surface diseases," Holland and Schwartz conclude. "Unfortunately, even with these advances, almost half such patients will not have much improvement after epithelial stem-cell transplantation. The encouraging results of (this study) provide a basis for further progress."
SOURCE: The New England Journal of Medicine 1999;340:1697-1703, 1752-1753.
