Catalase is one of the several important antioxidant enzymes that detoxifies hydrogen peroxide (H2O2) to nontoxic H2O+O2. While previous studies prove that catalase plays an important role in the mechanism of enzymatic antioxidant defenses, the basal level of catalase is inadequate to deal widi excessive generation of H2O2 during ischemia and inflammation of me central nervous system. Although administered exogenous catalase can significantly reduce free oxygen radical damage in inflammatory response and demyelination disorders, it does not eliminate H2O2. Moreover, catalase has to be administered daily to increase its level. Recently, viral mediated gene delivery has been successfully demonstrated in many mammalian tissues, including in vivo gene transfer into ocular tissue. Gene expression was observed in retinal photoreceptor, RPE, Corneal endothelial and trabecular meshwork. Although it has already been reported that in vitro human endothelial cells express a 2-4 fold increase in catalase level within 24 hours after administration of the viral-catalase cDNA complex, there is no information available regarding in vivo human catalase gene transfer.