Long-term morphologic changes in the endothelium of transplanted corneas

In a group of 17 patients, we studied the endothelial morphology and thickness of the central cornea yearly for five years after penetrating keratoplasty. The endothelial photographs were analyzed with a computerized digitizer to determine the area and shape of individual cells. The endothelial cell density decreased rapidly during the first two years postoperatively (59.4%), after which cell loss occurred at a considerably slower rate (3.5% of the preoperative cell count per year). During the observation period, the coefficient of variation in cell area stayed relatively constant (30%), implying that individual cells enlarge proportionally to their areas when spreading. The percentage of hexagonal cells and figure coefficient for the donor corneas were 60.5% and 0.8774, respectively. When the corneal thickness returned to normal two months after surgery, the endothelium showed a significant decrease in both measurements (48.2% and 0.8708, respectively), indicating a definite disruption of the normal hexagonal pattern. Between two months and two years postoperatively, both measurements gradually returned to normal. These results suggest that termination of endothelial cell loss from the central graft might be closely associated with the reestablishment of the normal hexagonal cellular pattern.