An in vitro test for the assessment of eye irritancy in consumer products - preliminary findings.
Synopsis An in vitro procedure for preliminary screening of severe eye irritants is described. Rabbit eyes are removed immediately after death and are placed in temperature controlled chambers. The eyes are superfused with isotonic saline and, after a suitable equilibration period, are treated with test substances. The effects of treatment (corneal swelling, and the severity, extent, and rate of development of opacity in the corneal epithelium and stroma) are assessed using the slit lamp biomicroscope. Experiments show that the cornea of the isolated eye remains viable and physiologically active for the duration of the test. Results of in vitro tests show a reasonably good correlation with in vivo data for a series of chemicals reported in the literature to be severely, moderately, or non-irritant to eyes. The effects of a range of high pH sodium hydroxide solutions are described. Thresholds for effect in vitro are defined and related to in vivo thresholds for high pH products. The effects of shampoos in the in vitro system are described, with preliminary results suggesting that the method can distinguish between normal 'adult'shampoos and 'baby'shampoos, which are known to differ in irritancy in vivo. Overall the in vitro procedure appears to offer a reliable screening procedure to identify severe eye irritants. Materials producing severe effects in vitro following a short contact time should not be tested in vivo, but where no effects are observed in vitro, in vivo testing may still be required. Like all in vitro procedures it has limitations compared with the in vivo eye test. It takes no account of the effects on the conjuctivae, nor does it take account of the rate of healing, both of which are important aspects of in vivo eye tests.
York
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Environmental Safety Laboratory, Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1LQ, UK.
Lawrence
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RS
Gibson
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GB