Retinal Ischemia in Relation to Glaucoma and Neuroprotection

Abstract

The word ischemia was coined by Virchow, who combined the Greek iskho, meaning “I hold back,” with háima, meaning “blood”. Hence, ischemia refers to a pathological situation involving an inadequacy (not necessarily a complete lack of) blood fl ow to a tissue, with failure to meet cellular energy demands. Ischemia should be distinguished from anoxia (a complete lack of oxygen) and hypoxia (a reduction in oxygen): ischemia always has a component of hypoxia/anoxia, but hypoxia/anoxia does not imply ischemia. For example, the retina may become hypoxic at high altitudes, producing loss of vision, but it is not ischemic. Similarly, anemia (generally a reduction, rather than complete absence of hemoglobin) is always a component of ischemia but not vice versa.