Justification of the enucleated eye test with eyes of slaughterhouse animals as an alternative to the Draize eye irritation test with rabbits.

The enucleated eye test (EET) with the isolated eye of rabbits has been recognized as a valuable alternative to the Draize test, because it represents a test system nearest to the in vivo test, without the need to use live animals. In this ex vivo bioassay, three parameters are measured to detect possible adverse eye effects, namely corneal swelling, corneal opacity and fluorescein retention. The measurement of corneal swelling in this assay guarantees a highly objective and discriminative parameter. In combination with the detailed observation of corneal opacity and fluorescein retention, a reliable evaluation of the eye irritation potential of test materials is achieved. However, laboratory animals are still necessary as eye donors. The use of slaughter animals, such as the cow, the pig and the chicken, as possible as eye donors for the EET was therefore examined. From these candidates, the chicken appeared to be the most practicable. 21 reference compounds, ranging from non-irritant to severe irritant, which had been tested previously in a validation study on alternative test methods for eye irritation testing, sponsored by the Commission of the European Communities, were examined in the Chicken Enucleated Eye Test (CEET). When compared with the in vivo EC classification, the CEET correctly classified each of the compounds that must be labelled in the EC as irritant (R36) or severely irritant (R41). In addition, since the CEET recognizes three levels of irritancy rather than two (as in the case of the EC classification) a small number of the compounds were recognized as slightly irritant, which according to the EC classification need not be labelled. It was concluded that this ex vivo test system is highly accurate in the assessment of eye irritation potential without the use of laboratory animals.