An in vitro method for estimating ocular irritation.

Three variations of an in vitro assay system called EYTEX were evaluated by comparing maximum in vivo Draize scores for 70 experimental consumer product formulations. The EYTEX in vitro assay (EIA) was chosen for in-house evaluation because it is an economical, objective system that is easy to learn. In the present study, double-blind samples were tested at National Testing Corporation (Lab 1) and an in-house laboratory (Lab 2). All products were tested in the standard, membrane, and rapid membrane (RMA) EIA. Most samples qualified for the membrane and RMA EIA, whereas approximately half qualified for the standard EIA. Results from both Labs 1 and 2 were highly correlated. The RMA assay gave the best overall performance of the three assays. The RMA EIA demonstrated the best correlation with in vivo data and qualified the highest percentage of formulations. RMA showed a 7.5% false positive identification of irritants. False negatives or irritants not identified were 6.1%. The predictive value for identifying irritants was 89%. Specificity or the ratio of non-irritants giving negative results to the total was 84%. The ratio of positive irritants to the total or sensitivity was 93%. Based on these results, EIA has demonstrated value as a screening tool for a broad variety of consumer products. Advantages of EIA include the opportunity to test undiluted products, reduce animal use, and lower costs.