The Bovine Corneal Opacity and Permeability test method (BCOP) is an in vitro test method that can be used to classify substances as 'ocular corrosives and severe irritants'. The BCOP uses isolated corneas from the eyes of cattle slaughtered for commercial purposes, thus avoiding the use of laboratory animals. Each treatment group (test substance, negative/positive controls) consists of a minimum of three eyes where the cornea has been excised and mounted to a holder. Depending on the physical nature and chemical characteristics of the test substance, different methods can be used for its application since the critical factor is ensuring that the test substance adequately covers the epithelial surface. Toxic effects to the cornea are measured as opacity and permeability, which when combined gives an In Vitro Irritancy Score (IVIS) for each treatment group. A substance that induces an IVIS superior or equal to 55.1 is defined as a corrosive or severe irritant.