The use of in vitro methods in the ocular irritation assessment of cosmetic products.

The ocular tissue is a complex system consisting of corneal and conjunctival epithelial cells, the underlying corneal stroma and associated endothelial cells. Exposure to chemicals may result in responses ranging from mild, slight redness and itching, to severe injury with loss of corneal epithelium, damage to stroma, inflammatory infiltration and loss of vision. This complexity hinders the development of in vitro methods able to replace animal testing. Various in vitro techniques have been proposed and subsequently developed as potential replacements for ocular toxicity screening on animals. Over the past 2 years, eight methods have been evaluated in these laboratories. The endpoint of these methods could be linked to one or to several clinical events occurring in the in vivo eye irritancy process described above. Using these systems, a battery of four complementary in vitro assays has been developed. For the categories of ingredients and cosmetic products investigated, the promising results obtained suggest that in vitro methods of ocular risk assessment may be used increasingly in the future.