Aim of the present ring trial was to prove 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 in the hemicornea model after chemical treatment 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 3 independent laboratories which 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 physico-chemical 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.
