In certain situations, free radicals can be generated in an exaggerated manner and can injure tissues and organs by interacting with lipids, proteins, or DNA. So, oxidative stress has been implicated in a large number of human diseases. To survive, the human body has developed a complex, efficient, and highly adaptive antioxidant defense system. The eye is also protected against oxidative stress by several mechanisms involving antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD), as well as by low-molecular-weight antioxidants such as glutathion (GSH) and ascorbate.

Primary open-angle glaucoma (POAG) is a chronic, slowly progressive optic neuropathy, characterized by excavation of the optic nerve head (ONH) and a distinctive pattern of visual field (VF) defects. The disease is multifactorial in origin, so that besides more extensively investigated factors oxidative stress has also been proposed as a contributing factor in the etiology of glaucomatous optic neuropathy. Oxidative stress represents a harmful state defined by the presence of pathologic levels of reactive oxygen species (ROS) relative to antioxidant defense.

Therefore, it would be also important to determine whether there is a relationship between circulating levels of the defense parameters to oxidative stress like malondialdehyde, GSH and SOD, and the occurrence of POAG.

Since there are only the limits of variation for these defense parameters available, mean values of the plasma levels of malondialdehyde, glutathion and superoxide dismutase will be determined in healthy subjects.