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Joke LENOIR, Els Adriaens, Ilse Claerhout, Philippe Kestelyn, Jean Paul Remon; The Slug Mucosal Irritation (SMI) Assay: A Tool to Predict Ocular Stinging, Itching and Burning Sensations. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4332.
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Eyes are very sensitive to stinging, itching and burning (SIB) sensations. A screening method for ocular discomfort would be very helpful in the development and refinement of ocular formulations. The Slug Mucosal Irritation (SMI) test was developed as an alternative for the Draize test (eye irritation test in rabbits). The aim of this study was to investigate whether the SMI-test could also demonstrate a relation between an increased mucus production (MP - expressed as % of initial body weight) in slugs and an elevated incidence of SIB sensations in human eyes by using shampoos as test substance.
The stinging potency of an artificial tear (ArtTear) and 5 shampoos (A-E) was evaluated with the SMI-test by placing 3 slugs per treatment 3 times on 100µl of the test item. After each 15-min contact period (CP), MP was measured. Evaluation of the results is based upon the total MP during the 3 repeated CPs. Additionally, a human eye irritation test (HEIT) was set up: 24 participants were dripped 10µl of a shampoo dilution in water or an artificial tear in one eye, while in the other eye 10µl of water was instilled (control). Evaluation of the test items was performed both by participants and an ophthalmologist at several time points (30 sec up to 30 min).
Preliminary analyses show that (1) ArtTear was best tolerated (total MP < 3% (SMI); median total score 0 (HEIT)); (2) scores and MP for shampoos were clearly higher than for ArtTear and water; (3) A was the best tolerated shampoo in both tests (total MP 3.4%; median total score 1), while B, C and D resulted in mild discomfort in slugs (total MP 3.8%-5.8%), with variability in the scoring behavior of the participants (median total scores 7.5-9); (4) E induced the highest MP in slugs (> 8%) and received the highest scores for immediate discomfort; (5) clinical evaluation does not correlate well with self evaluation.
These results indicate that the SIB protocol of the SMI-test is a good tool to predict clinical ocular discomfort with reference to non- and mildly irritating formulations in humans.
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