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Age-Related Macular Degeneration: Overview and Risk Factors

Age-related macular degeneration (ARMD) is a degenerative disease of the macula, the central part of the retina. There are two forms of ARMD: a "dry" form marked by degenerative changes in the macula without bleeding or leakage of fluid; and a "wet" form, which often occurs in association with dry ARMD and exhibits leakage and/or bleeding from new blood vessel growth beneath the retina. Central vision, which is necessary for fine visual tasks and many daily activities, is threatened by ARMD. Consequently, ARMD is the most common cause of legal blindness (20/200 or worse in both eyes) among elderly Americans. ARMD pathogenesis is not well understood.

Changes usually seen in early stages of dry ARMD include subretinal yellowish deposits (drusen) and chorioretinal atrophy. Visual loss in dry macular degeneration tends to have a slow progression and uncommonly results in severe loss of central vision. In addition, dry ARMD can transform to wet ARMD. The wet form of ARMD involves abnormal vessel growth (neovascularization) into the subretinal space, causing leakage of fluid and/or bleeding. Resultant vision loss can occur suddenly or over the course of a few weeks.

Dry ARMD may occur in both eyes, whereas wet ARMD usually occurs unilaterally.1 Acute (days to weeks) or unilateral changes require immediate ophthalmologic evaluation. Dry ARMD may cause slow recovery of vision after leaving sunlight and going indoors. Symptoms of wet ARMD include distortion of straight lines (although this may also occur in dry ARMD), and (rarely) changes in color perception. As the disease progresses, a central scotoma may occur. For example, when looking directly at one's face, the nose (or larger area) may appear absent or distorted.

Risk Factors

Persons of white, non-Hispanic race/ethnicity generally have a higher prevalence of ARMD.2,3 Blacks have the lowest risk.3

Established risk factors include:

Age. ARMD rarely occurs in persons under age 55 years old. The prevalence is 0.8% in those aged 70 and older, increasing to 16% in those over 90.4

Smoking. Individuals who smoke have a relative risk of 2.0 and greater, compared with those who have never smoked. Risk may remain elevated for 15 or more years after smoking cessation.5

Family history.

An additional probable risk factor is nutritional deficiency (see Nutritional Considerations).

Studies of the relationship of hypertension and sunlight exposure on macular degeneration show conflicting results. Cataract surgery as a possible risk factor needs further research.

 

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Age-Related Macular Degeneration: Diagnosis and Treatment >>