Oxidative stress of the cornea

The corneal epithelium is exposed to the atmosphere and is therefore prone to oxidative stress due to ultraviolet (UV) radiation and relatively high concentrations of oxygen. Using sensitive fluorescent probes, it is possible to measure oxidant formation in corneal epithelial cells at UV radiation intensities much lower than the lethal threshold. Cell death caused by UV radiation takes the form of either apoptosis or necrosis, depending upon the dose of radiation and on mitochondrial function, which is vital in determining the pattern of cell death. A high level of atmospheric oxygen, especially following periods of hypoxia, can also cause oxidative stress in epithelial cells. Although oxygen deprivation can damage cells, reoxygenation is believed to cause leakage of electrons from the mitochondria, which leads to accumulation of toxic reactive oxygen species within the cell. The fact that corneal epithelial cells have extensive stores of glycogen for anaerobic glycolysis indicates that they have a mechanism to protect themselves from oxidative damage.