The Importance of Ocular Irritation Testing

Ocular Irritation tests are essential for assessing the safety of products and chemicals that may come into contact with the eyes. Determination of eye irritation and serious eye damage are key parameters in safety assessment testing for registration and labeling of chemicals and other agrochemicals and drug development. 

Used in strategic combination and as part of a tiered approach, the SkinEthic™ RhCE test, EpiOcular™, BCOP,  and ICE assay, effectively categorize your chemical’s UN GHS ocular irritation potential. These tests used are widely recognized and have been used extensively across several industries. Several in vitro and ex vivo skin models and test strategies are available to determine eye irritation and serious eye damage. Test materials inducing serious irreversible eye damage are classified as UN GHS Category 1, while those inducing reversible eye irritation are classified as UN GHS Category 2. You can use these models to screen your test article early in its development, or during GLP toxicology testing.

In Vitro Eye Hazard Identification Assays

  • SkinEthic™ RhCE test method for eye hazard identification (OECD 492B)
  • EpiOcular™ Eye Irritation test for identifying chemicals not requiring classification (OECD 492)
  • Bovine corneal opacity and permeability assay (BCOP) (OECD 437)
  • Isolated Chicken Eye Test (ICE) (OECD 438)

With our expertise and experience, we can help you assess a test material’s potential for ocular irritation and serious eye damage through our complete package of services, while meeting regulations. Our commitment to accuracy and quality ensures that you receive reliable and trustworthy data, so you can make informed decisions about product safety.

Close up microscope in laboratory.

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SkinEthic™ RhCE method (OECD 492B) and EpiOcular™ Eye Irritation Test (OECD 492)

The SkinEthic Reconstructed Human Epidermis (RhCE) model method is a stand-alone in vitro test method used to assess the potential skin irritation or corrosion of chemicals, formulations, or products. The test utilizes a three-dimensional reconstructed model that mimics the human corneal epidermal.

The test model consists of an epidermis layer with corneal keratinocytes that are cultured to form a multilayered tissue structure. The test involves applying the test substance to the surface of the tissue and then measuring the cytotoxicity, and viability, at specific time points.

After treatment with the test substance the relative tissue viability is measured by photometrical measurement of formazan production by enzymatic reduction of MTT (MTT assay). Based on the degree of toxicity the compound is classified as UN GHS Category 1 or Category 2. If no or limited toxicity is observed (non-irritant) the test chemical is identified as not requiring classification and labeling according to UN GHS No category.

The EpiOcular test is a similar test, however this test can only predict chemicals not requiring classification and is used in a tiered approach.

Both ocular irritation test methods are validated methods and are recognized as an alternative to the traditional animal-based methods for assessing skin irritation or corrosion. Both methods are considered a humane alternative to animal testing as it does not involve the use of live animals.

Bovine Corneal Opacity and Permeability (OECD 437) & Isolated Chicken Eye Test (ICE) (OECD 438)

The BCOP and ICE tests are an in vitro test method that can be used to assess and classify substances as potential ‘eye irritation or corrosion of chemicals, formulations, or products’. These ocular irritation tests use living corneal tissue obtained from the abattoirs (left over material). Both the BCOP and ICE tests are considered a humane alternative to animal testing and do not involve the use of live animals. 

The BCOP test consists of topical application of a chemical on to corneal epithelium. Two important components which are predictive of irritation are measured being - corneal opacity, and permeability. Corneal opacity is a measure of the cloudiness or haziness of the cornea, while permeability refers to the ability of a substance to pass through the cornea. The change in opacity and permeability values (OD490) will be used to calculate an in vitro score (IVIS). 

In the ICE test multiple endpoints are measured after topical application: The endpoints evaluated are corneal opacity, swelling, fluorescein retention, and morphological effects (e.g., pitting or loosening of the epithelium). Combining these endpoints results like in the BCOP test in an in vitro score. This score can be used to identify the chemical as inducing serious eye damage (UN GHS category 1) or as a chemical not requiring classification for eye irritation or serious eye damage (UN GHS No Category).

Serious Eye Damage and Ocular Irritation Test Model Guidelines

The bovine corneal opacity and permeability test (BCOP, OECD437), the Isolated Chicken Eye test (ICE, OECD 438) and EpiOcular™, OECD 492 can be used together to classify many UN GHS Category 1 chemicals and chemicals not requiring classification for eye irritation or serious eye damage.

In June 2022, the OECD published the Test Method for Eye Hazard Identification No. 492B and the Defined Approach for Serious Eye Damage and Eye Irritation guideline No. 467, to also classify UN GHS Category 2 test materials using in vitro test methods.

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