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BCOP - Bovine Corneal Opacity/Permeability Assay

The Bovine Cornea Opacity/Permeability test (BCOP) is an alternative toxicology test to the Draize Rabbit Eye Test that is used to assess the ocular irritation of a test substance without the use of live animals.
The BCOP measures two endpoints: Changes in Opacity, reflecting protein denaturation and corneal injury as well as, Quantitative measurement of damage to corneal epithelium by determination of the amount of sodium fluorescein dye that passes through all corneal cell layers.
The BCOP has been used as an effective safety assessment test used by the cosmetic industry for many years. An OECD compliant protocol is offered by MB Research.
A substance that induces a BCOP In Vitro Irritation Score (IVIS) greater than or equal to 55.1 is defined as a corrosive or severe irritant. (OECD Guideline 437)

The cornea is of primary interest in assessing ocular irritation, the BCOP provides a useful parallel for possible human exposure. MB Research has pioneered the use and development of alternative and in vitro ocular toxicity models used mainly for cosmetics and consumer product safety evaluations. We have performed over 10,000 alternative ocular irritancy tests, which include over 3,000 materials assayed with the BCOP. The BCOP can be used in combination with other alternatives such as the CAMVA or HET-CAM to further determined ocular irritancy classification. Also see: ROBatt


Bovine corneas have been used since the 1940s. Current BCOP protocols were developed by Pierre Gautheron and Joseph Sina* as an alternative to the Draize Rabbit Eye Test to evaluate the response of an excised cornea (a waste byproduct of food production) by measuring light transmission and fluorescein permeability.

In 1994, MB Research conducted validation studies of the BCOP test method and established the BCOP as a standard assay.


In Vitro Toxicol 1994;7(3):283-90.

The author's task was to develop an approach to assessing ocular irritation, with minimal use of animals, so that it could be applied inhouse for worker safety testing.

The centerpiece of the multifaceted approach was the bovine corneal opacity and permeability (BCOP) assay, a test that measures opacity and cell sheet integrity in a target tissue: the cornea. Initial studies indicated that the BCOP gave an overall concordance with in vivo data of 85%. Two specific findings were that although suspensions could be tested, hydroscopic compds. tended to float on the exposure medium and adequate exposures could not be obtained; and that some compounds caused irritation in animals only after a delay of 24-72 hrs, and these could not be detected in vitro.

The BCOP method proved to be easily transferable, with good reproducibility in a small interlaboratory study. Overall concordance was approximately 83% among the six participants. Some slight modifications were made to the assay based on the results of this study, and a larger interlaboratory study was begun in order to broaden further experience and to attempt to define other areas of potential difficulty. Twelve labs participated in evaluating 52 diverse chemicals, and interlaboratory variability was quite low. Concordance was approximately 80%, with the false-negative and false-positive rate dependent upon the in vivo classification system generally in use at a particular lab.

In a comparison study in which 36 pharmaceutical manufacturer intermediates from 11 companies were all tested in the BCOP and 6 other assays, the BCOP was found to be among the most accurate tests. A tiered approach, combining results from other assays with the BCOP data, did not appear to provide an enhanced predictive value. Based on this body of data, it was considered that the BCOP assay is valid for the specific purposes and for the types of chemicals included in the studies (i.e., mainly pharmaceutical intermediates and raw materials).

Applicable Regulations/Guidelines:

* “Bovine Corneal Opacity and Permeability Test: An In Vitro Assay of Ocular Irritancy”, Gautheron P., Dukic, M., Alix, D. and Sina, J. Fundamental and Applied Toxicology 18, 442-449.

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