Causes

Although older age is the primary risk factor for cataracts, experts are still not certain about the exact biologic mechanisms that tie cataracts to aging.

Oxygen-Free Radicals (Oxidants) and Glutathione

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Researchers have been focusing on particles called oxygen-free radicals as a major factor in the development of cataracts. They cause harm in the following way:

• Oxygen free radicals (also called oxidants) are molecules produced by natural chemical processes in the body. Toxins, smoking, ultraviolet radiation, infections, and many other factors can create reactions that produce excessive amounts of these oxygen free radicals.
• Oxidants are missing an electron, so they are unstable and tend to chemically bind with other molecules in the body. When oxidants are overproduced, these chemical reactions can be very harmful to nearly any type of cell in the body. At times these reactions can even effect genetic material in cells.
• Cataract formation is one of many destructive changes that can occur with overproduction of oxidants, possibly in concert with deficiencies of an important protective anti-oxidant called glutathione.
• Glutathione occurs in high levels in the eye and helps clean up these free radicals. One theory posits that in the aging eye, barriers develop that prevent glutathione and other protective antioxidants from reaching the nucleus in the lens, thus making if vulnerable to oxidation.

Radiation and Electromagnetic Waves

Sunlight and Ultraviolet Radiation. Sunlight consists of ultraviolet (referred to as UVA or UVB) radiation, which penetrates the layers of the skin. Both have destructive properties that can promote cataracts. The eyes are protected from the sun by eyelids and the structure of the face (overhanging brows, prominent cheekbones, and the nose). Long-term exposure to sunlight, however, can overcome these defenses.

• UVB radiation produces the shorter wavelength, and primarily affects the outer skin layers. It is the primary cause of sunburn. It is also the UV radiation primarily responsible for cataracts. Long-term exposure to even low levels of UVB radiation can eventually cause changes in the lens, including pigment changes, which contribute to cataract development. (UVB also appears to be responsible for macular degeneration, an age-related disorder of the retina.) Some scientists suggest that global warming and ozone depletion may increase people’s exposure to UVB, leading to a greater incidence of cataracts.
• UVA radiation is composed of longer wavelengths. They penetrate more deeply and efficiently into the inner skin layers and are responsible for tanning. The main damaging effect of UVA appears to be the promotion of the release of oxidants.