A simple method for controlled freezing of human donor corneae

A simple method for freezing cultured human donor material with dimethyl sulfoxide (DMSO) was developed empirically in a commercially available microcomputer-controlled apparatus allowing reproducible freezing curves to be made. The optimum cooling rate was found to be 1.0 degrees C/min down to -40 degrees C and then 5.0 degrees C/min to -80 degrees C. Total cell loss rates were 36.9 +/- (SD) 19.8% of postmortem endothelial cell counts. An improved method for evaluating endothelial viability was applied, which enabled us to observe definite cell survival after a postculture period.