Physiological function of regenerating endothelium.

A defined area, 4 mm. diameter, cryothermal injury was created on a rabbit cornea. Corneal thickness was measured at four distances from the limbus to the center of the cornea during the swelling phase after endothelial damage, and during the recovery period. Rapid initial swelling was followed by a period of stable maximum thickness over 24 hours. More swelling occurred centrally than peripherally. Eight days after injury the peripheral cornea regained normal thickness, and the central portion was normal thickness after 10 to 12 days. Histological examination of corneal endothelium showed that early migration of cells into the denuded area occurred 6 hours after injury. By 2 days, most of the denuded area was covered by endothelial cells, although the cells were large and irregular. The number of normal cells increased, and of irregular cells decreased, over the next five days, until two weeks after freezing all cells had a normal appearance. The recovery of physiologic endothelial function lags behind the histologic recovery by about four to five days, indicating that recovery of the normal endothelial permeability is possibly related to the status of the cellular junctions rather than covering of the posterior surface by cells per se.