Role of free radicals in ocular diseases: An overview

The aim of the present review is to focus on the potential consequences of free radicals in human health and disease with special reference to ocular disorders. The balance between the free radicals and antioxidants is crucial for good health. The risk of free radicals in health has been increasing gradually. Many of the degenerative disease like atherosclerosis, cancer inflammatory joint disease, asthma, diabetes, dementia and degenerative eye disorder are the result of imbalance of free radicals and antioxidants. In case of eye, free radicals are responsible for the pathogenesis of the majority of serious ocular diseases such as cataract, primary open angle glaucoma and age-related macular degeneration. The process of biological ageing might also have a free radical basis. Most free radical damage to cells involves oxygen free radicals or reactive oxygen species (ROS) which include non-radical species such as singlet oxygen and hydrogen peroxide as well as free radicals. The ROS can damage genetic material, cause lipid peroxidation in cell membranes and inactivate membrane-bound enzymes. Humans are well endowed with antioxidant defenses against ROS. These antioxidants include ascorbic acid (vitamin C), α-tocopherol (vitamin E), β-carotene, coenzyme Q10, enzymes such as catalase and superoxide dismutase, and trace elements including selenium and zinc. This review is an attempt to compile and document the information on various implications of free radicals in the ocular disorders.