ASSESSMENT OF RECOVERY FROM OCULAR IRRITANCY USING A HUMAN TISSUE-EQUIVALENT MODEL

The SKIN2TM ZK1200 tissue equivalent model has been used in an explora tory study of recovery from ocular irritation. Nine substances from th e ECETOC eye irritation reference chemicals data bank were tested. The cellular viability of the tissue model was measured using the MTT ass ay immediately after chemical exposure and after incubation periods co rresponding to observation times used in the Draize tests. The cellula r viability of the tissue specimens exposed to moderate irritants, wit h modified maximum average score (MMAS) values between 15 and 40 (n = 5), returned to control levels within 1-7 days. Tissue specimens expos ed to 1 and 10% benzalkonium chloride showed significantly reduced MTT activities at day 14 and day 21. Mild ocular irritants, with MMAS val ues below 3 (n = 2), did not induce significant depressions of the MTT activities of the tissue specimens after 60 min exposure. A relativel y good correlation (r = 0.73) was obtained between the exposure times used in vitro and Draize MMAS values. Moreover, the incubation periods needed for the exposed SKIN2 ZK 1200 to regain control MTT activities showed a good agreement (r > 0.90) with days-to-clear ocular irritanc y in the Draize test. (C) 1997 Elsevier Science Ltd.