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 and retina through the initiation of lipid peroxidation of cell membranes. The oxidative damage to the iris epithelial-cell membranes, induced by the injection of hydrogen peroxide (H2O2) at different concentrations into the anterior chamber of the rabbit eye, was studied by means of the measurement of lipid peroxidation products. Thiobarbituric acid reactive (TBAR) products were significantly increased compared with normal control iris after the intracameral injection of H2O2 at concentrations of 0.1 (p < 0.02), 10 and 100 mM (p < 0.001). Viscoelastic substances, 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 prior to a H2O2 injection. This is the first report of lipid peroxidation of the iris and the 'antioxidant'-protective effect of viscoelastic substances. This new technical approach could be used as a test of efficacy of the protective effect of viscoelastic substances.