Macular Degeneration Health Center

Understanding Macular Degeneration -- the Basics

What Is Macular Degeneration?

Age-related macular degeneration (AMD) is the foremost cause of vision loss in the U.S., with millions of Americans showing some sign of the disorder. AMD is uncommon in people younger than 55. If you are over 65, macular degeneration may already affect your central vision -- the vision you need for close work like reading and sewing. 

AMD occurs in two forms:

• Dry: Most common
• Wet: Less common, but requires immediate medical attention to preserve central vision

Most people with AMD do not become totally blind; they can still see well enough to ''get around.'' It is their central vision used for reading and detailed vision that is lost. Regular eye exams can detect early signs of AMD and identify when more extensive testing, such as angiography, may be necessary. Recent innovations in AMD treatment can halt or slow progression of retinal changes.

What Causes Macular Degeneration?

The word "macula" comes from the Latin word meaning "spot." The macula is a very small portion of the retina that is responsible for your central vision. It is about the size of a pencil eraser. The macula is loaded with photoreceptors that enable you to read, watch television, drive, sew -- anything that requires focused, precise vision.

Outside of the central macula, the retina has fewer photoreceptors, so image resolution is less detailed. Although this part of the retina continues to process images in the majority of your field of vision, the tissue damage caused by AMD distorts or obscures part of the crisp central image that your eye transmits to your brain.

In the dry form of AMD -- the most common form -- tiny yellow deposits, called drusen, develop beneath the macula, signaling a degeneration and thinning of nerve tissue. 

About 10% of cases of dry macular degeneration develop into the wet, or neovascular, form of AMD, in which abnormal blood vessels grow beneath the macula. As these vessels leak blood and fluid onto and underneath the retina, retinal cells die, causing blurring, distortion, and blank spots in your field of vision.