Changes in human donor corneas preserved for longer than 4 weeks

Corneas are usually stored for a maximum of approximately 30 days in European cornea banks. Although attempts are being made to prolong culture periods, data on their success are extremely limited to date. The following study was carried out to describe the capacities and limits of the established system.Thirty-seven human corneas were stored foror = 12 weeks under standard eye bank conditions [modified minimal essential medium (MEM), 31 degrees C, closed system]. Twenty-one fresh human corneas served as control. Both the adenylate nucleotides and the glucose and lactate concentrations were measured in the tissue (all cellular layers) by using the bioluminescence technique. The endothelial-cell densities also were determined.Endothelial-cell densities decreased from 2,963.4 +/- 58.7 cells/mm2 (fresh) to 2,649 cell/mm2 after 4 weeks and to 2,087 cells/mm2 after 6 weeks. Storage for periods6 weeks led to total endothelial necrosis. Biochemical studies showed improving values during the first 4 weeks and acceptable conditions foror = 6 weeks.From these data, we conclude that long-term organ culture in a closed system is limited to approximately 6 weeks and thereby confirm the clinical results of Früh and Böhnke.