Test No. 492: Reconstructed human Cornea‑like Epithelium (RhCE) test method for identifying chemicals not requiring classification and labelling for eye irritation or serious eye damage

This Test Guideline describes an in vitro procedure allowing the identification of chemicals (substances and mixtures) not requiring classification and labelling for eye irritation or serious eye damage in accordance with UN GHS. It makes use of reconstructed human cornea-like epithelium (RhCE) which closely mimics the histological, morphological, biochemical and physiological properties of the human corneal epithelium. The test evaluates the ability of a test chemical to induce cytotoxicity in a RhCE tissue construct, as measured by the MTT assay. Coloured chemicals can also be tested by used of an HPLC procedure. RhCE tissue viability following exposure to a test chemical is measured by enzymatic conversion of the vital dye MTT by the viable cells of the tissue into a blue MTT formazan salt that is quantitatively measured after extraction from tissues. The viability of the RhCE tissue is determined in comparison to tissues treated with the negative control substance (% viability), and is then used to predict the eye hazard potential of the test chemical. Chemicals not requiring classification and labelling according to UN GHS are identified as those that do not decrease tissue viability below a defined threshold (i.e., tissue viability > 60%, for UN GHS No Category).