Corneal opacity, hydration and endothelial morphology in the bovine corneaopacity and permeability assay using reduced treatment times

The purpose of this study was to determine whether the standard bovine corn ea opacity and permeability (BCOP) assay exposure time of 10 minutes overes timates the ocular irritancy of chemical substances. Corneas were subjected to BCOP protocol following 30-second and 1-minute exposures to irritants. Corneal opacity and hydration (mg H2O/mg corneal were then measured and com pared to data obtained after 10 minute irritant treatments. For most test s ubstances corneal opacity and hydration were lower following reduced exposu re times. It is suggested that using shorter exposure times in BCOP protoco l may be more predictive of human response to ocular irritants, since irrit ants are usually in brief contact with the ocular surface during accidental exposure. A second purpose of this study was to examine effects of irritan ts on the corneal endothelium. Corneas were treated according to BCOP proto col following exposure to irritants for 1 or 10 minutes. The endothelium wa s stained with Alizarin Red and trypan blue,and examined using Light micros copy. Severe irritants, such as NaOH and trichloroacetic acid, cause endoth elial cell death. It was also determined that simply mounting the cornea in the BCOP assay holders caused damage to 20% of the endothelial cells. Beca use the endothelium is essential for normal corneal transparency and hydrat ion, it is suggested that examination of the endothelium be added to the BC OP assay and that optimization of the assay will require modification of th e cornea holders. (C) 2000 Elsevier Science Ltd. All rights reserved.