Numerous mechanisms of free radical induced oxidative tissue damage have been identified in several disease processes. The eye is unique in the way that light -a potentially damaging agent via oxidative reactions- is the physiological stimulus of the organ. The retina consists mainly of unsaturated fatty acids which are very susceptible to oxidative damage. Therefore, a relation between age related macular degeneration and a chronic light exposure has been postulated. This, on the other hand appears to be related to light induced oxidative mechanisms playing an important role in the development of senile cataract. Several additonal mechanisms for free radical generation in the eye such as ischemia and inflammation have been shown in diseases also occuring in other organs. Oxidative tissue damage is believed to play a role in the pathogenesis of diabetic retinopathy. Free radicals could be shown to initiate both, oxidative tissue damage and cytokine production thus being also involved in the propagation of proliferative activity.