[The potential role of oxidative stress in the pathogenesis of the age-related macular degeneration (AMD)]

Abstract

Age-related macular degeneration (AMD) is one of the most important causes of blindness among the elderly. Although the disease presents a serious social problem, its pathogenesis is still unclear. AMD involves the posterior pole of the retina, the place responsible for acute vision. Retinal factors (intensive oxygen metabolism, continual exposure to light, a high concentration of polyunsaturated fatty acids, the presence of photosensitizers) increase the production of reactive oxygen species. Oxidative stress is aggravated by the presence of lipofuscin. The pigment accumulates with age, especially in the eyes of those with AMD. The most important risk factors for AMD, beside genetic predisposition, are factors leading to oxidative stress in the retina, e.g. age above 65 years, cigarettes smoking, obesity, exposition to blue light, and bright irises. Macular pigment is a natural barrier protecting the central retina against oxidative damage. It is formed by two dihydroxycarotenoids, lutein and zeaxanthin. The prereceptoral location of the macular pigment permits it to act as an optical filter that absorbs short-wavelength visible light. Carotenoids also demonstrate antioxidant activity. Eyes with a predisposition to develop AMD or which already have developed the disease have considerably less macular pigment and a greater risk of oxidative damage compared with healthy eyes. Investigations have shown that diet poor in antioxidant micronutrients (vitamin C, E, carotenoids, zinc) and low plasma levels of antioxidants may favor the development of the age-related macular degeneration. The findings demonstrated that micronutrient supplementation enhances antioxidant defense and might prevent or retard AMD or modify the course of the disease.