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Age-Related Macular Degeneration

Darren Bell, M.D.

Age-related macular degeneration (AMD) has been in the news a lot recently, primarily because of newly developed pharmacologic therapies. While certainly welcome news for patients, unless you or someone you know has been diagnosed with AMD, you may wonder why it has received so much attention.

AMD currently affects nearly 2 million Americans and is the leading cause of irreversible vision loss in the developed world among people over age 60. As the U.S. population ages, the number of people affected by AMD is predicted to increase to 3 million by 2020. AMD affects the high-definition central vision, which is used for activities such as reading, driving, watching television, and fine detail work. Objects such as door frames, walls, and sign posts may appear wavy or curved rather than straight or there may be a blurry or blank spot in the center of vision. AMD does not affect the peripheral vision, although some patients may still meet the criteria for legal blindness, defined as 20/200 or worse. Risk factors that increase the risk of AMD include being female, advancing age, smoking, family history, and cardiovascular disease.

AMD occurs in two forms, with similar beginnings. Approximately 90% of patients with AMD have the “dry” or nonexudative form, in which yellow deposits of cellular waste material called drusen, form underneath the center of the retina. The disease slowly progresses over time as more deposits accumulate and the photoreceptor cells (rods and cones) become damaged.

The second form, “wet” or exudative AMD, develops in only 10% of patients, but is more rapidly progressive and is responsible for 80% of the cases with severe vision loss. Exudative AMD involves growth of new blood vessels into the space underneath the retina. Blood and fluid can leak out from these new vessels, leading to scar formation in the involved area. Although vision is affected as soon as the fluid appears, the changes can sometimes be reversed if detected early enough. Once a scar develops, the vision loss is generally permanent. Recent advances in treatment for macular degeneration have centered on methods to get the new blood vessels and the fluid associated with them to resolve before the formation of scar tissue.

The previously mentioned pharmacologic therapies for exudative AMD can stop vision loss in approximately 90% of cases, and even improve the vision in 40%. By contrast, little proven therapy exists for the dry form of AMD. At the present time, only certain high dose antioxidants have been shown in the Age-Related Eye Disease Study (AREDS) to be of benefit in slowing the progression to the advanced form of AMD. Numerous clinical trials involving potential therapies for both wet and dry forms of AMD are ongoing.

If you or someone you know potentially has vision loss from AMD, you should make an appointment with your eye care provider for a complete eye exam, including a dilated fundus exam.