OECD Test Guideline 492 describes an in vitro method using reconstructed human cornea-like epithelium (RhCE) to identify chemicals that do not require classification and labelling for eye irritation or serious eye damage under the applicable UN GHS framework.

The test uses three-dimensional RhCE tissue constructs that closely mimic the morphology and structure of the human corneal epithelium. Depending on the validated test system used, the tissues are reconstructed from human-derived epidermal keratinocytes, immortalized human corneal epithelial cells, or primary human corneal epithelial cells and cultured to form a stratified, highly differentiated squamous epithelium.

The test chemical is applied topically to the RhCE tissue, followed by a post-treatment incubation period. Eye hazard potential is assessed based on chemical-induced cytotoxicity, since the extent of initial cellular injury is closely associated with serious eye damage and eye irritation responses. Tissue viability is measured using tetrazolium dye-based assays such as MTT, WST-8 or WST-1, depending on the validated RhCE model used.

Chemicals that maintain tissue viability above the defined method-specific threshold may be identified as not requiring classification for eye irritation or serious eye damage under UN GHS. OECD TG 492 is not intended, on its own, to differentiate between UN GHS Category 1 serious eye damage and Category 2 eye irritation; chemicals requiring classification may therefore require additional testing within an appropriate testing strategy.

Vipragen Biosciences offers in vitro eye irritation testing in accordance with OECD TG 492 using reconstructed human cornea-like epithelium-based test methods as part of its in vitro safety assessment services.