For personal care, cosmetic and light industrial products sold in the EU, in vitro solutions for testing human eye irritation potential are essential. This is particularly the case at a time when RIPT (Repeat Insult Patch Tests) are difficult to conduct due to social distancing requirements for human volunteers. The speed and accuracy of in vitro tests can help organisations get to market quicker; vital when demand for safe, hygiene products is so high.

But despite some reconstructed human corneal models having been approved by regulators for a while, there are still gaps in the in vitro testing armoury for eye irritation. Good news has arrived however, with the adoption of the Ocular Irritection® test by the OECD. In this article, we look at why the gaps exist and how new technologies can help.

THE CHALLENGES OF CLASSIFYING EYE IRRITANTS

Reconstructed human corneal models have been approved for regulatory eye irritation testing for some time as described in OECD Test Guideline 492. The tests work on the same mechanism as the skin equivalents, measuring damage to the tissue following application to the surface of the cornea. However, currently these can only be used as stand-alone tests for chemicals not requiring classification (ie GHS No Category), leaving a huge gap when it comes to classifying eye irritants.

The IATA (last updated July 2019) clearly describes a requirement to perform tests that are able to identify serious eye damage, either as a first step (top down approach for expected irritants) or as a follow-on to unexpected positive results in TG 492 (bottom up approach).

Cow's eyes are used in the BCOP testSo which tests are needed? The default test for the identification of serious eye damage is currently the Bovine Corneal Opacity and Permeability (BCOP) method (OECD TG 437).

The use of bovine eyes from slaughter houses has led to much debate about the status of this test as an animal replacement method, and it raises concerns for companies developing vegan products. Many companies won’t commission or conduct the BCOP, but for chemical companies who need to comply with global regulations across a range of industry sectors, there has been little choice.

PROGRESS MADE WITH NEW OCULAR IRRITECTION® TEST

Other methods have contributed a promising shift to truly animal-free methods. The new Ocular Irritection (OI®) test (OECD TG496 published October 2019) measures changes in opacity of a synthetic macromolecular matrix. It’s approved for the classification of both chemicals and mixtures with potential to induce serious eye damage, as well as those not requiring classification for eye irritation or serious eye damage and be a useful first step in either top down or bottom up approaches.

In this sense, it matches the applicability of the longstanding short-time exposure test (OECD TG491 updated June 2020) using rabbit corneal cells, but it overcomes the solubility limitations encountered when using submerged cell cultures. However these can’t be used as stand-alone tests, meaning that further steps are still required for sub-categorisation of serious eye damage and eye irritation. In many cases that still means the BCOP and, in a minority of cases, the Draize test (OECD TG405).

XCellR8 will be offering the Ocular Irritection test in 2021. If you’d like to discuss how you can begin the process of eliminating animal components from your eye irritation testing strategy, please get in touch with a member of our team. You might also be interested in our short video showing a regulatory eye irritation test being conducted in our laboratory.