Assessment Of Eye Irritation Potential Research Articles

Application of SV40 T-transformed human corneal epithelial cells to evaluate potential irritant chemicals for in vitro alternative eye toxicity

Assessment of eye irritation potential is important to human safety, and it is necessary for various cosmetics and chemicals that may contact the human eye. Until recently, the Draize test was considered the standard method for estimating eye irritation, despite its disadvantages such as the need to sacrifice many rabbits for subjective scoring. Thus, we investigated the cytotoxicity and inflammatory response to standard eye irritants using SV40 T-transformed human corneal epithelial (SHCE) cells as a step toward development of an animal-free alternative eye irritation test. MTT and NRU assays of cell viability were performed to investigate the optimal experimental conditions for SHCE cell viability when cells were exposed to sodium dodecyl sulfate (SDS) as a standard eye irritant at 6.25×10−3 to 1×10−1%. Additionally, cell viability of SHCE cells was examined in response to six potential eye irritants, benzalkonium chloride, dimethyl sulfoxide, isopropanol, SDS, Triton X-100 and Tween 20 at 5×10−3 to 1×10−1%. Finally, we estimated the secretion level of cytokines in response to stimulation by eye irritants in SHCE cells. SHCE cells showed a good response to potential eye irritants when the cells were exposed to potential irritants for 10min at room temperature (RT), and cytokine production increased in a concentration-dependent manner, indicating that cytotoxicity and cytokine secretion from SHCE cells may be well correlated with the concentrations of irritants. Taken together, these results suggest that SHCE cells could be an excellent alternative in vitro model to replace in vivo animal models for eye irritation tests.

A critical review of the assessment of eye irritation potential using the Draize rabbit eye test.

Traditionally, the eye irritation potential of substances and products has been assessed using the Draize eye test. While this procedure has been criticized in terms of its scientific validity and its ethical acceptability, it remains the only official, government-recognized procedure for predicting the irritant effect of substances in the eye. The relative absence of serious human accidents testifies to the success of the predictions. With the development of alternative non-animal procedures to replace the Draize test, the data generated in the Draize procedure are also being used as a 'gold standard' against which the performance of alternative procedures is measured. The major sources of variability are small group size and inability of existing scoring systems to reflect the complexities of the total in vivo response. In addition, the use of algorithms to simplify the in vivo data (for comparison with in vitro data) also misrepresents the in vivo data. Addressing the above issues would inevitably increase the use of animals. This would go against the general public demand for a reduction in the use of animals. Therefore the issue is to decide upon a simple parameter (for comparison with in vitro data) that encompasses the complexity of the irritation response and accurately reflects irritation without requiring the use of additional test animals. Such a parameter could be the recovery time. In addition, controlled human testing to benchmark the Draize data would be invaluable. The future use of Draize data in the validation of in vitro alternatives is undisputed, but the utility of these data will only be enhanced by a proper understanding of the shortcomings of the Draize test.

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 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.