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Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the most common cause of legal blindness among people over the age of 50 in the Western world. It affects the macula, the central part of the retina. As the photoreceptors begin to deteriorate, so does the central vision needed for everyday activities such as reading or driving. Peripheral vision is usually unaffected.

Approximately 25 to 30 million people have some form of AMD, and that number is expected to triple over the next 25 years.

Research has yet to identify the causes of AMD. As the name suggests, the biggest risk factor is age—the disease affects almost 30% of people over age 75. The disease is more prevalent in women, Caucasians, smokers, people who are obese, and those who have a family history.

Possible preventive strategies are being investigated but have yet to be fully elucidated. Nutrition and the role of vitamins, minerals and antioxidants in the prevention of macular degeneration have recently received considerable attention as a result of the Age-Related Eye Disease Study (AREDS). In addition, the impact of other nutritional supplements, such as lutein and zeaxanthin, on eye health is currently being studied.

The two distinct types of age-related macular degeneration (AMD) are known as the dry and wet forms. Most cases of the disease start with the dry form, which may or may not develop into the wet form.

Dry Age-Related Macular Degeneration
Dry age-related macular degeneration, which is also known as atrophic or non-neovascular macular degeneration, is the milder form of the disease, accounting for up to 90% of all cases. The key clinical sign is development of drusen, small, round, white-yellow lesions in the macula. The connection between drusen and vision loss is unclear. In its early stages, dry age-related macular degeneration is characterized by several small or a few medium-sized drusen. The size or number of drusen increases in the intermediate stage. With advanced disease, a breakdown of photoreceptor cells and the supporting tissue accompanies an increased number of drusen. There is no treatment currently available for dry age-related macular degeneration.
Wet Age-Related Macular Degeneration

Wet age-related macular degeneration accounts for only 10% of cases, but it is responsible for 90% of the severe vision loss associated with AMD. The term wet refers to choroidal neovascularization across the macula. These abnormal vessels leak fluid and blood into the tissue at the back of the eye, causing damage to the retina. This in turn leads to scar tissue and a large blind spot, which impairs central vision. Worldwide, approximately 500,000 new cases of wet age-related macular degeneration occur each year.

Wet age-related macular degeneration tends to develop in one eye at a time. Approximately half of patients who have one affected eye will be diagnosed with the condition in their second eye within 5 years. Rapidity of disease progression varies among individuals, from a few months to 3 years. Untreated, the majority of eyes affected with wet age-related macular degeneration will become functionally blind within approximately 2 years.

Because treatments that slow or halt progression of wet age-related macular degeneration are available, persons over age 60 should receive yearly ophthalmologic examinations with dilated pupils to ensure that the disease is diagnosed at its earliest stage.

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