The cause of age-related macular degeneration (AMD), a major cause of loss of vision after the age of 60, is unknown. The two types of AMD are wet and dry. In wet AMD, the tissues have characteristic new blood vessels (neovascular). In dry AMD, the tissues are atrophic (shriveled). Recent studies report the following risk factors: cigarette smoking, age, poor nutrition, obesity and inadequate dietary antioxidants.
The eye is subject to the stresses of environmental chemicals, radiation, and oxygen in the air, which may also be risk factors in AMD, cataracts, glaucoma, uveitis. Reactive oxygen species (ROS) produced by these stresses can cause tissue damage, and oxidation of lipids by ROS can lead to eye damage. A chemical, called MDA (malondialdehyde), is produced by the oxidation and is a measure of oxidation. Protein oxidation plays a role in Alzheimer’s disease, Parkinson’s disease, cancer, hypertension, cardiovascular disease, diabetes, reperfusion injury* and aging.
Natural antioxidants include the following: Vitamin C, glutathione (GSH) superoxidant dismutase (SOD), glutathione peroxidase and catalase. These work by “scavenging” free radicals. Although not produced by the human body, vitamin C (ascorbate) is an effective antioxidant.
Half of the fifty people studied by the authors had AMD. They were given anti-vascular endothelial growth factor (anti-VEGF) as part of the study. They were first given complete eye examinations. Extensive blood testing was done, and blood levels of MDA were higher in the people with AMD to a significant degree compared to those without AMD. The higher blood levels of MDA are consistent with higher degrees of oxidation.
SOD antioxidant levels were significantly lower in the AMD patients as compared to the group without AMD. SOD is a very important antioxidant in the protection of the eye, and many people did not have enough SOD in their blood to protect them.
Levels of vitamin C, GSH (glutathione) and GPx (glutathione peroxidase enzyme) were not different in the two groups. These antioxidants protect eyes from damage, also.
CONCLUSION: Oxidative stress of fats and proteins play an important role in AMD. Deficiency of antioxidants may be a significant factor in the progression of AMD. Patients with AMD have low levels of the enzyme SOD.
PMID: 21789374.
Summary #555.
