Storage of human corneas in dextran and chondroitin sulfate-based corneal storage medium: changes in stromal free sodium.

OBJECTIVES To evaluate the hydration and the levels of free and total sodium in human corneal stromata preserved for up to 21 days in a dextran and chondroitin sulfate-based corneal storage medium (Optisol-GS, Chiron IntraOptics, Irvine, Calif) and to evaluate the effect of epithelial removal on stromal sodium and hydration parameters. METHODS Stromal hydration was evaluated thermogravimetrically. A sodium-specific electrode and an atomic absorption spectrophotometer were used to determine the amounts of free and of total stromal sodium, respectively, of preserved human corneas. In 50% of the corneas, the epithelium was removed prior to placement in the storage medium. After 3, 7, 14, or 21 days at 4 degrees C, corneas were removed from the storage medium and sodium measurements were taken. RESULTS In corneas with an intact epithelium, the stromal hydration as well as the stromal free sodium and total sodium levels were relatively constant up to 21 days of storage in the preservation medium. In the absence of the epithelium, the water and sodium contents of the stroma increased significantly during storage. CONCLUSION The presence of an intact epithelium is required for maintaining the hydration and sodium levels within the corneal stroma during storage. Removal of the epithelium prior to storage results in increased sodium values and hydration, which may affect postkeratoplasty deturgescence.