Corneal permeability in a redesigned corneal holder for the bovine cornea opacity and permeability assay

The bovine cornea opacity and permeability assay (BCOP) is a proposed alternative to the Draize rabbit test for potential eye irritants. In the standard BCOP, bovine corneas are mounted in a holder on a flat surface between two identical chambers. The flat configuration of the standard holder does not conform to the normal curved shape of the bovine cornea and it comes into direct contact with the cornea tissue. Mounting corneas in this holder causes extensive damage to both epithelial and endothelial corneal cell layers. Our laboratory has designed a new holder that allows the cornea to maintain its natural curvature and does not damage the cornea. Previous tests, using both the new and standard holders, and comparing corneal opacity, hydration and endothelial morphology, have shown that the new holder is a significant improvement over the standard holder. The present study extends the comparisons of the new and standard holders to measurement of corneal fluorescein permeability. The permeability (ng/cm(2)/min) of intact corneas, corneas with no epithelium, and corneas treated with 1% NaOH, isopropanol, acetone, 30% trichloroacetic acid or 30% sodium dodecysulfate for either 1 or 10 min was determined by measuring fluorescence of samples taken from the endothelial chamber after 90 min epithelial exposure to 0.04% sodium fluorescein. In all trials, the redesigned holders yielded not only lower permeability measurements but also decreased measurement variability. The data provide further evidence that the new holder is an improvement over the standard holder and should be incorporated into a new protocol for the BCOP.