Contributions of physicochemical properties to the evaluation of ocular irritation

By Regnier, J.F. - Imbert, C.

International guidelines for the evaluation of ocular irritation advise that all the available information, structural and physicochemical, should be taken into account in order to minimise the testing of substances under conditions that are likely to produce severe reactions in laboratory animals. In order to determine whether the pH and the acidic/alkaline reserve would be suitable parameters for the prediction of ocular irritation, we have measured, under standard conditions, the pH and the acidic/alkaline reserve of 166 chemicals (90 non-irritant, 22 irritant, and 54 severely irritant for the eye, according to the EEC classification and labelling system). The combination of these parameters permitted the correct identification of 74% of the severely irritant chemicals and 97% of the non-serverely irritant (non-irritant or irritant) chemicals. The predictive value for a severely irritant potential was 93%, and 88% for non-severely irritant chemicals. This physicochemical approach, used as a first line screen for ocular irritation, is very simple and inexpensive.