The objective of this study was to evaluate the epithelium of human corneas stored in Optisol-GS (Chiron Intraoptics, Irvine, CA) for extended periods (2-34 days). Human corneas stored in Optisol-GS (n = 64) were obtained from the Georgia Eye Bank. Corneal epithelial viability was assessed by using the Calcein-AM (Molecular Probes, Inc., Eugene, OR) ethidium homodimer stain, a fluorescent assay used to distinguish live from dead cells. Scanning and transmission electron microscopy was used to evaluate epithelial ultrastructure. The results showed that corneas stored up to 6 days in Optisol-GS had minimal damage of the epithelium. Calcein-AM ethidium homodimer staining showed 20-25% epithelial damage. Corneas stored 7-10 days had a further increase in epithelial damage (30-35%). Corneas stored for 11-15 days had marked increases in epithelial damage (40-50%), and corneas stored 16-34 days showed significant epithelial damage (60-70%). The data show that corneas stored in Optisol-GS are able to maintain the epithelium up to 6 days. A gradual decrease in epithelial viability and loss of epithelial cells occurs in corneas stored 6-10 days. Corneas stored for > 10 days have a marked loss of epithelial cells with extensive epithelial damage.