Human corneas were preserved at the temperature of liquid nitrogen. Most of the corneal cells on thawing appeared to be intact although epithelial and stromal cells were electron-dense and flattened. Ultrastructural evidence of freeze-thawinduced injury was present in some of the endothelial cells, and others were electron-dense, distorted, and only partly attached to Descemet's membrane. All of the corneal cells in nonfrozen controls incorporated tritium uridine into RNA. Half of the endothelial cells in cryopreserved corneas did not incorporate the radioactively labeled compound. The remaining endothelial cells and all of the other corneal cells did so but at a reduced amount. In addition, the endothelial cells in cryopreserved corneas were more susceptible to ultrastructural damage during the incubation for radioautography as evidenced by lysis of 90% of the cells.
Van Horn DL, Hanna C, Schultz RO. Corneal CryopreservationII. Ultrastructural and Viability Changes. Arch Ophthalmol. 1970;84(5):655-667. doi:10.1001/archopht.1970.00990040657020