© 1989 Oxford University Press
research-article |
An Objective Procedure for Quantitating Eye lrritation Based upon Changes of Corneal Thickness1
Department of Toxicology. PPG Industires. Inc., Environmental Sciences Center 260 Kappu Drive, Pittsburgh, Pennsylvania 15238
Received January 20, 1988; accepted July 20, 1988
An Objective Procedure for Quantitating Eye Irritation Based upon Changes of Corneal Thickness. KENNAH. H. E. II, HIGNET, S., LAUX, P. E., DORKO, J. D., AND BARROW. C. S. (1989). Fundam Appl Toxicol. 12,258-268. For four decades, the Draize test has remained the accepted method for evaluatmg eye lrritation. Criticisms center around the inhumane treatment of animals and the irreproducibility of the subjective scoring procedure. The objective of this study was to determine if changes in corneal thickness obtained uslng a slit-lamp pachometer could be used to replace the Draize scoring procedure and provide a method for quantifying ocular irritation. Twenty-four chemicals (six surfactants, seven alcohols, four ketones, four acetates, and three aromatics) were instilled in the conjunctival sacs of rabbits and irritation monitored by Draize scoring and changes in corneal thickness. The Draize procedure was more adept at detecting minor conjunctival damage, but corneal thickness exhibited less variation and increased sensitivity for detection of healing reactions. A significant linear correlation (y = 1.736x + 92.883)was established between Draize score and corneal thickness changes with a correlation coefficient (r) of 0.86 and an F-value for regression of 261.3. Using these findings, an ocular irritation ranking system is proposed based upon the percentage of corneal swelling. Ocular irritation potentia1 was ranked for the chemlcal groups tested (surfactants > alcohols > ketones or acetates > aromatics). Quantitauon of ocular irritation from changes in corneal thickness provides objective, numerical data applicable to standard parametric statistical procedures. This should eliminate the subjective blas inherent to Draize scoring and decrease intra-and interlaboratory variability.