In vitro predictive tests for eye irritants

The developments and attitudes towards in vitro testing since the first major workshop on irritation testing five years ago (Reinhardt et al., 1985) are summarized. Many test systems have been described and an increasing number of compounds tested. However, the in vivo data basis used for comparison is still heterogeneous and a proper analysis of most in vivo/in vitro correlations is difficult. Some progress has been achieved with various controlled validation programmes on a national and international level, all of which have not been completed. In order to improve this slow progress the following measures are proposed: (1) expectations for a uniform test need to be discouraged when heterogeneous chemical actions may occur, and rigid test guidelines have to be replaced by flexible ones (differentiated approach); (2) many practical small steps need to be taken rather than one theoretical large step, that is by accepting simple in vitro tests for restricted groups of chemicals such as severe irritants (adaptive approach); and (3) the threshold for acceptance of in vitro tests needs to be lowered by regulatory bodies and routine laboratories (optimistic approach).