These measurements are then combined to derive an eye irritation classification or an in vitro
irritancy score. Eye irritation is primarily determined by the extent of initial injury that correlates with the extent of cell death and ultimately the outcome of an irritant on an eye ( Jester et al., 2001). Generally, slight irritants damage the superficial epithelium, mild irritants penetrate further to damage the Veliparib concentration stroma and severe irritants penetrate through the cornea and damage the endothelium ( Jester et al., 2001) ( Fig. 1). Ocular organotypic models or enucleated eye tests (EET) were first introduced by Burton et al. (1981) using isolated rabbit eyes (IRE) from animals used for other research purposes, or those that had been sacrificed commercially as a food source (ICCVAM,
2010c). The IRE test, or rabbit enucleated eye test (REET) was originally developed to detect severe irritants that cause serious irreversible eye damage (Guo et al., 2012). Currently, the most commonly used test substances for IRE are active pharmaceutical ingredients, chemical/synthetic intermediates, cleaners, raw materials, soaps Idelalisib nmr and detergents, solvents and surfactants (ICCVAM, 2010c). Lab-specific IRE protocols have developed over time, with variables including the evaluation of one to four different endpoints, differences in prediction models or classification systems, differences in the number of controls used and methodological variations (ICCVAM, 2010c). IRE has been extensively evaluated by international regulatory bodies including the European Commission/British Home Office (EC/HO), the Cosmetic, Toiletry and Perfumery Association (CTPA) and the Interagency Regulatory Alternatives Group (IRAG) (Guo et al., 2012). However, to date, the IRE protocol is not considered to be adequately validated for classification of ocular irritancy. Instead, it is advised that IRE is used for non-regulatory
optimization studies to facilitate the collection of data to expand toxicology databases (ICCVAM, 2010c). Slaughterhouse waste BCKDHA has been extensively investigated as an alternative tissue source (Prinsen, 1996) for EETs. Bovine or porcine corneas are often used (Reichl and Muller-Goymann, 2001), although chicken enucleated eye tests (CEET), also known as the isolated chicken eye (ICE) test are widely accepted to be a reliable and accurate slaughterhouse tissue for assessing the eye irritation potential of test materials (Prinsen, 1996). The ICE testing protocol (TG 438, (OECD, 2013b) is based upon the IRE model and was first described by Prinsen and Koëter (1993). The eyes are isolated from an intact chicken head and processed 2 h postmortem. The enucleated eye is then positioned in a clamp, with the cornea positioned vertically and transferred to a superfusion apparatus for examination of damage (Maurer et al., 2002) (Fig. 2i).