Dry AMD
AMD is classified into two types: dry AMD (also known as non-exudative or non-neovascular) and wet AMD. Dry AMD is more common, accounting for about 90 per cent of AMD cases. It may cause little or no visual symptoms until it is more advanced.
What Happens
Dry AMD occurs when the layer of cells beneath the retina (called the retinal pigment epithelium) begins to age and thin. This, in turn, affects the overlying retina, particularly the light-sensitive cone cells, gradually dulling and blurring central vision, and often reducing colour perception.
Dry AMD tends to progress over a matter of years, much more slowly than wet AMD. As dry AMD gets worse, a person may see a blurred or blank spot in the center of vision or notice a gradual decline in their ability to see fine print or detail in images. People with dry AMD may have difficulty recognizing faces or may need more light for reading and other tasks. Gradually, as less of the macula functions, central vision may be lost altogether. In some individuals, as dry AMD worsens the condition can progress into wet AMD.
Dry AMD generally affects both eyes, but vision can be lost in one eye while the other eye seems unaffected. If it occurs in one eye, there may be no noticeable changes in overall vision. People can still drive, read and see fine details with the eye that still sees clearly.
Symptoms
One of the most common early signs of dry AMD is the presence of drusen, which are yellow-white deposits that accumulate under the retina. The presence of drusen may result in a further breakdown and thinning of macular tissues.
A harmless type of drusen is often found in people over age 60, and almost all people over the age of 50 have at least one small druse in one or both eyes. For a more detailed look of how drusen works in the eye, take the AMD Challenge.
Stages
Dry AMD has three stages, all of which may occur in one or both eyes:
- Early Dry AMD: People at this stage of dry AMD have either several small drusen or a few medium-sized drusen. At this point, there are usually no symptoms, although there may be a loss of contrast sensitivity. People without the ability to detect contrast, for example, may have trouble seeing the screen of an ATM machine or a menu in a dark restaurant.
- Intermediate Dry AMD: People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light and some magnification may be needed for reading and other tasks.
- Advanced Dry AMD: In addition to drusen, people with advanced dry AMD have localized loss of the retinal pigment epithelium under the retina, resulting in a loss in function of the overlying cones cells in the macula. This breakdown can cause a blurred or blank spot in the center of the vision. Over time, the blurred spot may get bigger and darker, with increasing vision loss.