The slug mucosal irritation (SMI) assay: development of a screening tool for the evaluation of ocular discomfort caused by shampoos.

In this research, the slug mucosal irritation (SMI) assay was applied to predict ocular discomfort caused by shampoos to investigate the correlation between responses in slugs and humans. Several SMI experiments and a human eye irritation test (HEIT) were performed with 1 artificial tear solution (ArtTear) and 5 shampoos (A-E; 5%-dilution). In the HEIT, evaluation was performed by participants and an ophthalmologist at several time points. Analyses reveal that (1) a significant positive association existed between immediate stinging reaction reported by the participants and the mean total mucus produced by the slugs (MTMP) (Spearman's Rank correlation=0.986, p<0.001); (2) ArtTear was best tolerated in both tests; (3) moreover, all shampoos induced higher reactions than ArtTear and water; (4) Shampoo A induced the highest MTMP and received higher scores for immediate discomfort; (5) B was the best tolerated shampoo in both tests, while C, D and E resulted in more pronounced reactions; (6) lacrimation was found not to be statistically correlated with discomfort sensations reported by the participants. The SMI assay is a promising evaluation method for discomfort in the human eye. Screening prototype (eye) formulations with this assay allows formula optimization prior to a HEIT.