Endothelial survival in corneal tissue stored in M-K medium.

Cat corneas were stored at refrigerator temperatures in M-K medium (TC-199, 5% dextran), modified M-K medium (TC-199, 1% chondroitin sulfate), or on the intact globe in moist chambers for intervals of one to nine days. Less than 5% of the endothelial cells stained with trypan blue in corneas stored one to four days, regardless of the method of storage. In contrast, after five days, 20% or more of the cells took up the stain in 17 to 21 corneas stored in M-K medium. Although stain uptake indicated nonviability of cells, most of the endothelial cells remained structurally intact when observed by scanning and transmission electron microscopy unless the corneas were incubated in fresh TC-199 for two hours at 35 degrees C before trypan blue staining. In that case, the percentages of disrupted cells observed at each time interval correlated with the percentages of cells that had stained in each cornea. These results indicated that storage in M-K medium did not extend the time donor coreas can be stored before transplantation beyond four days.