The Eye Irritation Test (EIT) is an OECD-approved in vitro non-animal test method for identifying chemicals and mixtures not requiring classification and labelling for eye irritation or serious eye damage. The test method utilizes an in vitro reconstructed human corneal epithelium (RhCE) model (EpiOcular™, MatTek Corp.), in an acute exposure assay to support international regulatory labeling requirements, according to the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS).
The Eye Irritation Test can be used to support European Cosmetics dossier and REACH registration requirements. Since the mechanistic basis for eye irritation involves corneal penetration and cellular/tissue damage, the measurement of cell viability is highly relevant. Therefore, the viability of the RhCE tissues is determined by the NAD(P)H-dependent microsomal enzyme reduction (and to a lesser extent by the succinate dehydrogenase reduction) of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). Test materials that result in a relative tissue viability >60% do not require classification for eye irritation or serious eye damage.