The effect of ophthalmic preservatives on the shape of corneal endothelial cells

The mean area (293.6 +/- 53.6 micrometers 2) and perimeter (65.5 +/- 5.8 micrometers) of individual cells were determined from the photographed endothelium of a total of 54 guinea pig corneas, after staining with silver nitrate and removal of the epithelium and stroma. In addition a quantitative assessment of cell shape S (= P2/A) was calculated. The mean cell density (3406 +/- 619 cells per mm2) was similar to that for young humans, and the S value (14.76 +/- 0.73) was as expected for slightly irregular hexagonal and pentagonal shapes. Incubation of the corneas in glutathione-bicarbonate-Ringer solution for periods up to 4 h resulted in only slight changes in the endothelial cell shape (S = 15.21 +/- 0.89). However, incubation with thimerosal (0.01%) for 2 h (S = 16.78 +/- 1.79) or with disodium ethylenediaminetetraacetate (Na2EDTA) (0.2%) for 1 h (S = 17.20 +/- 2.36) gave a marked increase in the tortuosity of the cell 'outlines'. Longer periods of contact with Na2EDTA resulted in a rounding up and separation of endothelial cells.