Endothelial evaluation in the cornea bank.

The light microscope is the first-choice technique for the evaluation of organ-cultured donor corneas. For the microscopic visualization of the endothelial cells, the corneas have to be immersed in ahypotonic solution. The number of cells, their vitality and morphology are analyzed. The cell densityis easily estimated with the fixed frame/L method. Use of an image analysis system enables computer processing and counting of digitalized endothelial cell images. An adequately high endothelial cell density after the culture period is a decisive criterion that must be met before releasing adonor cornea for grafting. An endothelial cell density of 2,000-2,200 cells/mm2 is generally recognized as the lower limit for the longest possible graft survival. While an evaluation of the endothelium does not necessarily have to be performed at the beginning or middle of organ culture, it isobligatory at the end. Morphology assessment should routinely involve estimating the pleomorphism (deviation from hexagonality), polymegathism (variation in cell area) and granulation/vacuolization of the endothelial cells. Recognition of devitalized cells is easily facilitated by vital stainingwith trypan blue.