Reactive oxygen species (ROS) are vital metabolites in numerous biological functions. Disorders of cellular mechanisms can cause overproduction of ROS and, subsequently, oxidative damage to DNA, proteins, cells and tissues, which is associated with the pathogenesis of a number of neurodegenerative and inflammatory diseases. Development of highly sensitive, relatively simple and fast-to-implement innovative methods to detect oxidative stress requires understanding of how such disorders relate to the level of ROS. This research aimed to apply the biological fluids' ROS detection method we have developed (using the stable platinum nanoelectrode that allows assessing the level of hydrogen peroxide (H₂O₂) down to 1 μM) and determine the level of H₂O₂ in lacrimal and intraocular fluids of rabbits, as well as to investigate how the level of H₂O₂ changes under the influence of antioxidant therapy. The effect superoxide dismutase (SOD) nanoparticles produce on biological fluids' ROS level was shown. The level of H₂O₂ in lacrimal fluid increased 10 and 30 min after instillation of SOD nanoparticles. As for the intraocular fluid, H₂O₂ concentration starts to grow only 30 min after instillation of SOD nanoparticles, which suggests that the they penetrate the internal structures of the eye gradually. The method seems to be of value in the context of eye diseases diagnosing and treatment.