OECD 492B | The Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Eye Hazard Identification 

The OECD 492B test is an internationally recognized in vitro method for evaluating the potential of chemicals and mixtures to cause eye irritation or serious eye damage. It is widely used for regulatory safety assessment and identifies substances requiring classification under the UN Globally Harmonized System (GHS) for ocular hazards:

• Category 1 (Serious eye damage classification); H318
• Category 2 (Eye irritation classification); H319
• No Category (No classification required)

The Human Corneal Epithelium (HCE) Time-to-Toxicity (TTT) test, as described in OECD 492B, is the latest addition to the NAMs (New Approach Methodologies / Non-animal Alternative Methods) for eye hazard testing. It represents an improvement over OECD TGs 437 and 492, which allow the identification of "not requiring classification" (No Category) but could not distinguish between Category 2 and Category 1 substances. And even more, the HCE-TTT test fully replaces animal testing methods, such as the Draize test.

Test Principle

The three-dimensional reconstructed human cornea-like epithelium (RhCE) model from SkinEthic™ closely mimics the histological and biochemical properties of the human corneal epithelium. Cell viability, which correlates with tissue health, is quantified by the enzymatic reduction of the tetrazolium salt (MTT) to a formazan product. Reduced viability indicates a potential ocular hazard. The test employs multiple exposure durations to improve the accuracy and predictability of eye irritation categories (Time-To-Toxicity approach).

Test Scope

The test involves the measurement of MTT reduction on the SkinEthic™ tissue model at multiple time points following incubation with the test item, a negative control, and a positive control.

Test Variant

For strongly colored test items where photometric evaluation is not possible due to interference, we offer an analytical approach using High-Performance Liquid Chromatography (HPLC) to quantify the evolved formazan product.

Please contact us for more information.