Are local tolerance tests in animals always necessary?

The Draize test was introduced in 1944 as a toxicological standardization method to study irritation and toxicity of substances applied to the eye (and the skin). It has been considered, from that time on, as a routine toxicological protocol by most regulatory agencies to test eye-tolerance of chemicals. The authors think that for ethical and scientific reasons, this test is obsolete and should be changed or eliminated. They suggest the use of cell cultures or an in vitro technique for ocular safety assessment. The described technique uses a bovine cornea clamped in vitro between two chambers and kept alive in physiological conditions during six hours. This in vitro corneal perfusion system replaces in vivo irritation tests and enables quantitation of corneal drug uptake at the same time. This system provides reproducible results and can be used in ocular toxicological studies as well as in pharmacokinetic modeling.