Correlation study of two methods for evaluating corneal endothelial damage in vitro: the Janus green photometry technique versus cell counting.

Counting of endothelial cells after vital staining is a time-consuming method which, in addition, requires considerable experience and does not normally allow for the study of the entire endothelial cell surface. However, the Janus green photometry technique (JGPT) is an objective, time- and personnel-saving procedure which also has the advantage of allowing for the evaluation of the whole endothelial cell surface. A comparative simultaneous experimental study of the two methods had not been reported. Freshly excised pig corneas (n = 58) were preserved in MK storage medium for 4, 7, 14 and 20 days at 4 degrees C. All corneas were stained with Janus green and alizarin red. A 7-mm corneal button corresponding to an endothelial surface of 38.46 mm2 was punched out. The percentage of damaged cells was determined with cell counting (CC) and with JGPT, and the results were statistically compared. Two methods for CC were used. Cells were counted either directly under the microscope or in photomicrographs. The overall correlation between the results of CC and JGPT was R = 0.98. However, when endothelial cell damage was higher than 30%, CC became an estimation by approximation, since necrotic areas were confluent, whereas with JGPT the results were usable even when the damage was 100%. Thus it appears that although the two methods can be used interchangeably, JGPT may in some instances be the method of choice.