LIPID-PEROXIDATION IN THE IRIS AND ITS PROTECTION BY MEANS OF VISCOELASTIC SUBSTANCES (SODIUM HYALURONATE AND HYDROXYPROPYLMETHYLCELLULOSE)

Free radicals, especially the hydroxyl radical (OH'), are known to be toxic for several ocular structures including the cornea, lens, iris a nd retina through the initiation of lipid peroxidation of cell membran es. The oxidative damage to the iris epithelial-cell membranes, induce d by the injection of hydrogen peroxide (H2O2) at different concentrat ions into the anterior chamber of the rabbit eye, was studied by means of the measurement of lipid peroxidation products. Thiobarbituric aci d reactive (TBAR) products were significantly increased compared with normal control iris after the intracameral injection of H2O2 at concen trations of 0.1 (p < 0.02), 10 and 100 mM (p < 0.001). Viscoelastic su bstances, widely used in anterior ocular surgery, sodium hyaluronate ( Healon(R)) and hydroxypropylmethylcellulose, show a protective effect against rabbit iris lipid peroxidation. A statistically significant (p < 0.001) inhibition of the release of TBAR products occurred in both experimental groups that received an injection of these substances pri or to a H2O2 injection. This is the first report of lipid peroxidation of the iris and the 'antioxidant'-protective effect of viscoelastic s ubstances. This new technical approach could be used as a test of effi cacy of the protective effect of viscoelastic substances.