The most common type of macular degeneration, about 85 to 90 percent of cases, is the dry (atrophic) type:
- The photosensitive cells of the macula slowly break down.
- Yellow protein deposits called drusen (extracellular waste products from metabolism) form and accumulate under the retina between the retinal pigmented epithelium (RPE) layer and the Bruch's membrane, which supports the retina.
- Drusen are often found in the eyes of older people, but an increase in the size and number of these deposits is frequently the first sign of macular degeneration.
- Over time, drusen lead to deterioration of the macula and the death of RPE and photoreceptor cells. This process results in a blurring or spotty loss of clear, straight-ahead vision but does not cause pain.
- In the early stages of the disease, the patient may notice slightly blurry vision. However, as more and more of the cells die, central vision worsens.
- Although dry AMD does not cause complete blindness, in its most advanced form it can cause profound central vision loss, severely affecting a person's quality of life.
The dry type of macular degeneration has three stages:
- Patients have several small or a few medium-sized drusen.
- No vision loss or symptoms occur at this stage.
- Patients have many medium-sized or one or more large drusen.
- Some people may need more light for tasks such as reading.
- A blurry spot may appear in the center of the visual field.
- Patients have a large number of drusen deposits.
- RPE, photoreceptor (light-sensitive) cells and supporting tissue in the retina begin to break down.
- A large blurry spot occurs in the center of the visual field and can become larger and darker, eventually causing a complete loss of central vision.