Study Design of In Vitro Eye Irritation [Bovine Corneal Opacity and Permeability (BCOP) Test] (OECD 437)
The In Vitro Eye Irritation Test using the Bovine Corneal Opacity and Permeability (BCOP) method, outlined in OECD Guideline 437, is an alternative to animal testing for assessing the eye irritation potential of chemicals and mixtures. Here’s a breakdown of its study design:
Test System:
- Isolated bovine corneas: Freshly obtained corneas from slaughtered cattle are used.
- Corneal holders: Specialized holders maintain the corneas in a simulated physiological environment during the test.
Test Procedure:
- Test substance preparation: The substance is prepared in appropriate concentrations and dilutions according to the OECD 437 protocol.
- Application to corneas: The test substance is applied directly onto the epithelial surface of the cornea.
- Incubation: Corneas are incubated for a predetermined period (typically 60 minutes) under controlled conditions.
- Opacity and permeability assessment:
- Opacity: Light transmission through the cornea is measured using an opacitometer to quantify clouding or opacity caused by the test substance.
- Permeability: Leakage of sodium fluorescein dye from the anterior to posterior chamber of the cornea is measured with a spectrophotometer to assess disruption of the corneal barrier.
Scoring and Interpretation:
Both opacity and permeability measurements are combined to calculate an In Vitro Irritancy Score (IVIS).
Based on the IVIS, the substance is classified into several irritation categories:
- Non-irritating: Low IVIS
- Mild irritant: Moderate IVIS
- Moderate irritant: High IVIS
- Severe irritant/corrosive: Very high IVIS
Benefits:
- Reduced animal use: Eliminates the need for live animals, aligning with ethical considerations.
- Cost-effective: Generally faster and less expensive than traditional in vivo studies.
- Standardized protocol: Ensures international harmonization and data comparability.
- Predictive accuracy: Proven to be reliable in predicting eye irritation potential for certain categories of chemicals.
Limitations:
- Uses animal-derived tissues, raising some ethical concerns.
- Limited species specificity, may not fully translate to human responses for all substances.
- Not suitable for all chemicals, especially volatile or highly reactive substances.
- May not detect all types of eye irritation mechanisms.
Additional Resources:
OECD Test Guideline 437: https://www.oecd-ilibrary.org/environment/test-no-437-bovine-corneal-opacity-and-permeability-test-method-for-identifying-i-chemicals-inducing-serious-eye-damage-and-ii-chemicals-not-requiring-classification-for-eye-irritation-or-serious-eye-damage_9789264203846-en
