In vitro eye irritation testing using the open source reconstructed hemicornea – a ring trial

The aim of the present ring trial was to test whether two new methodological approaches for the in vitro classification of eye irritating chemicals can be reliably transferred from the developers' laboratories to other sites. Both test methods are based on the well-established open source reconstructed 3D hemicornea models. In the first approach, the initial depth of injury after chemical treatment in the hemicornea model is derived from the quantitative analysis of histological sections. In the second approach, tissue viability, as a measure for corneal damage after chemical treatment, is analyzed separately for epithelium and stroma of the hemicornea model. The three independent laboratories that participated in the ring trial produced their own hemicornea models according to the test producer's instructions, thus supporting the open source concept. A total of 9 chemicals with different physicochemical and eye-irritating properties were tested to assess the between-laboratory reproducibility (BLR), the predictive performance, as well as possible limitations of the test systems. The BLR was 62.5% for the first and 100% for the second method. Both methods enabled to discriminate Cat. 1 chemicals from all non-Cat. 1 substances, which qualifies them to be used in a top-down approach. However, the selectivity between No Cat. and Cat. 2 chemicals still needs optimization.