Abstract
PURPOSE: Cataracts are often considered to be an unavoidable consequence of aging. Oxidative damage is a major cause or consequence of cortical and nuclear cataracts, the most common types of age-related cataracts. METHODS: In this review, we consider the different risk factors, natural history and etiology of each of the 3 major types of age-related cataract, as well as the potential sources of oxidative injury to the lens and the mechanisms that protect against these insults. The evidence linking different oxidative stresses to the different types of cataracts is critically evaluated. RESULTS: We conclude from this analysis that the evidence for a causal role of oxidation is strong for nuclear, but substantially lower for cortical and posterior subcapsular cataracts. The preponderance of evidence suggests that exposure to increased levels of molecular oxygen accelerates the age-related opacification of the lens nucleus, leading to nuclear cataract. Factors in the eye that maintain low oxygen partial pressure around the lens are, therefore, important in protecting the lens from nuclear cataract. CONCLUSIONS: Maintaining or restoring the low oxygen partial pressure around that lens should decrease or prevent nuclear cataracts.