Abstract A method is described whereby an objective measurement of eye irritation may be made The method is based on measurement of the change in corneal thickness that follows exposure of the eye to an irritant substance and the results obtained agree well with those obtained in the subjective Draize test The proposed method has the advantage, however, that the results, being objective, may more easily be standardized and are free from the individual bias inherent in the Draize test. The results are also more readily subjected to statistical analysis and can, therefore, form the basis for the assessment of comparative eye irritancy.