What is Age-Related Macular Degeneration?

Age-related macular degeneration (AMD) is the leading cause of irreversible, severe, blindness in patients over the age of 50 in the Western World. Some form of AMD affects almost 15 million people in the United States alone.

AMD is caused by the deterioration of the central portion of the retina, the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. The retina's central portion, known as the macula, is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, recognize faces or colors, and see objects in fine detail. Peripheral vision is usually left intact. Among the symptoms most commonly experienced are a central blurred or blank spot, distortion of objects, or simply blurred vision.

The number of cases of AMD will increase significantly as baby boomers age and overall life expectancy is increasing. Unfortunately, the specific factors that cause AMD are not conclusively known, but aging appears to be the most important risk factor. Atrophic changes of the retina may also occur.

Two Forms of AMD

Dry AMD

Dry AMD is the most common form. Approximately 85-90 percent of the cases of macular degeneration are the "dry" (atrophic) type. In this form of AMD, the deterioration of the retina is associated with the formation of small yellow deposits (drusen) under the macula.

Dry AMD

		Normal macula
		Drusen form under the macula
		Sometimes abnormal new blood vessels form, leading to the "wet" type of macular degeneration.

Wet AMD

Wet AMD represents between 10 and 15 percent of all AMD cases, but is responsible for most of the severe vision loss associated with this disease. Wet AMD is characterized by the development of abnormal, blood vessels (known as choroidal neovascularization) under the center of the retina (macula).These new blood vessels may then bleed and leak fluid, thereby causing the macula to bulge or lift up, thus distorting or destroying central vision. This phenomenon untreated eventually leads to scarring and destruction of the retina.

Thermal laser surgery or photodynamic therapy may be useful for some patients with active bleeding from this disease.

Time-Lapse Depiction of "Wet" Macular Degeneration

		Normal macula
		Abnormal new blood vessels grow under the macula.
		The abnormal blood vessels bleed. As a result of the bleeding, the macula bulges. The damage to the macula causes central vision to be distorted or destroyed.