Types of AMD

AMD comes in two types - the "DRY" form and the more severe "WET" form.

Dry AMD, the more common and milder form of AMD, accounts for 85% to 90% of all cases. It develops gradually over time and usually causes only mild loss of vision. One key identifier for AMD is the collection of small, round, white-yellow, fatty deposits called drusen in the central part of the retina, the macula. Drusen accumulate in the Retina Pigment Epithelium (RPE) tissue beneath the macula and the macula thins and dries out. The amount of vision loss is related to the location and amount of macular thinning caused by the drusen. Sometimes abnormal new blood vessels form (so called choroidal neovascularization - see below). It is therefore important for individuals with dry AMD to have their eyes examined regularly, because the dry form may eventually develop into the wet form.

Wet AMD can rapidly damage the macula and result in a very quick loss of central vision.

Although the wet form of AMD accounts for only 10 - 15% of all AMD, the risk of severe sight loss is much greater. Wet AMD is responsible for 90% of cases of severe vision loss associated with AMD. It is caused by the growth of abnormal blood vessels, or choroidal neovascularization (CNV), under the macula. These abnormal vessels leak fluid and blood into the tissue at the back of the eye, causing a blister to form in the retina. The resulting scar tissue leads first to distortion and eventually to loss of central vision. Wet AMD can rapidly damage the macula and result in a very quick loss of central vision.

Based upon the pattern of the blood vessel leakage, your doctor may classify your wet AMD as "classic" or "occult". In pure classic CNV, the blood vessels that are involved can be seen distinctly. In the pure occult form, it is impossible to locate the leaking vessels. Often patients present a combination of both occult and classic CNV with a portion showing a defined site of leakage and another portion being obscured.

The vision loss symptoms experienced with wet AMD and the availability of treatment options depend on the type of AMD but also on the location of the leakages. For wet AMD we distinguish between three different locations based on the distance between the CNV and the central part of the macula, the fovea. The three locations are: subfoveal, juxtafoveal and extrafoveal. Subfoveal, is CNV that lies directly below the fovea. Juxtafoveal and extrafoveal CNV lie progressively further away from the fovea (but still within the macula).

For treatment options please go to the "Treatments" section.