|Macular Degeneration is the leading cause of blindness affecting more Americans than cataracts and glaucoma combined. Few people are aware that macular degeneration is an incurable eye disease and that it is the leading cause of blindness for those aged 55 and older in the United States, affecting more than 10 million Americans. Macular degeneration 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.
As people age, their chances for developing eye diseases increase dramatically. Unfortunately, the specific factors that cause macular degeneration are not conclusively known and research into this little-understood disease is limited.
There are two basic types of macular degeneration: "dry" and "wet." Approximately 85% to 90% of the cases of macular degeneration are the "dry" Patients with this "dry" form may have good central vision (20/40 or better) but substantial functional limitations, including fluctuating vision, difficulty reading because of their limited area of central vision, limited vision at night or under conditions of reduced illumination.
In the "dry" type of macular degeneration, the deterioration of the retina is associated with the formation of small yellow deposits, known as drusen, under the macula. This phenomena leads to a thinning and drying out of the macula, causing the macula to lose its function. The amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen.
The early stage of age-related macular degeneration is associated with minimal visual impairment and is characterized by large drusen and pigmentary abnormalities in the macula.
This form of macular degeneration is much more common than the "wet" type of macular degeneration and it tends to progress more slowly than the "wet" type. However, a certain percentage of the "dry" type of macular degeneration turns to "wet" with the passage of time. There is no known cure for the "dry" type of macular degeneration.
What a patient may see with the DRY form of Macular Degeneration:
Central vision may appear blurry because parts of the macula have begun to die, leaving blank spots in vision. Straight lines may look wavy. Side or "peripheral" vision is rarely affected.
In the "wet" type of macular degeneration, abnormal blood vessels grow under the retina and macula. These new blood vessels may then bleed and leak fluid, causing the macula to bulge or lift up, thus distorting or destroying central vision. Under these circumstances, vision loss may be rapid and severe.
What a patient may see with the WET form of macular degeneration:
With the "wet" type, the patient may see a dark spot (or spots) in the center of their vision due to blood or fluid under the macula. Straight lines may look wavy because the macula is no longer smooth. Side or "peripheral" vision is rarely affected. However, some patients do not notice any such changes, despite the onset of neovascularization.Therefore periodic eye examinations are still very important for patients at high risk.