Age-Related Macular degeneration (ARMD) is caused by the deterioration of the central portion of the retina (inside back layer of the eye.) ARMD is the leading cause of legal blindness in the elderly Caucasian population, but is relatively rare in other races. ARMD affects approximately 30% of the Caucasian population over age 75. The exact cause of ARMD is not known but genetics seems to play a significant role.

The retina records the images we see and sends them, via the optic nerve, to the brain. The retina's central portion, known as the macula, is responsible for central vision and our ability to read, drive a car, recognize faces, colors and see objects in fine detail. If macular degeneration develops in one eye, it will generally develop in the other eye as well. In ARMD, deposits called drusen occur beneath the central retina. Drusen are thought to be metabolic by-products of the retina itself.

The photograph: The image above is an actual photograph of the inside of an eye affected by ARMD. The circular structure on the left is the head of the round optic nerve where it enters the eye. Blood vessels can be seen spreading across the retina after
exiting from the center of the optic nerve. Drusen are the yellowish spots visible beneath the transparent retina.

 

"Dry" Macular Degeneration There are two types of Macular Degeneration: dry and wet. The dry form accounts for about 90 percent of all cases. Vision loss from dry macular degeneration occurs very gradually over the course of many years. Individuals with dry macular degeneration do not usually experience a total loss of central vision. However, it can become difficult to perform tasks that require fine-detail vision. There is ongoing research into possible treatments for dry macular degeneration but to date, no proven treatment exists. "Wet" Macular Degeneration Wet macular degeneration accounts for about 10 percent of all cases. Wet macular degeneration may be referred to as "choroidal" or "subretinal" neovascularization. It can also be called "exudative" or "disciform" degeneration. In wet macular degeneration, abnormal blood vessels grow beneath the macula. These vessels leak blood and fluid into the macula, which damages the retina's light receptor cells. The wet form of macular degeneration tends to progress rapidly and can cause severe damage to central vision. In some cases, if wet macular degeneration is diagnosed early, laser surgery can prevent extensive central vision loss. In this type of surgery, laser beams are used to destroy the leaky blood vessels that form beneath the macula. For laser surgery to be effective, it's critical that wet macular degeneration be diagnosed before extensive vision loss occurs. A new procedure called "PhotoDynamicTherapy" (PDT), which uses special light-activated drugs, also shows promise in the treatment of wet ARMD.

Test Yourself The square box at the left is called an Amsler Grid. It is one of the tests used to check for macular degeneration. Cover one eye and note the dot in the center. While keeping your eye trained on the dot, notice the lines which cross over the rest of the box. These lines should be straight with no gaps or missing areas. Repeat the test in your other eye. If there is any question about your result, you should schedule a eye examination for a more thorough test.

PREVENTION

According to Johanne M. Seddon, M.D., and colleagues at Harvard Medical School, "Increasing intake of foods that are rich in antioxidants, particularly certain carotenoids, may reduce the risk of developing advanced AMD." The carotenoids lutein and zeaxanthin show the strongest protective effect against this degenerative disease."

Some scientists have suggested an association between macular degeneration and high saturated fat, low carotenoid pigments, and other substances in the diet. There is evidence that eating fresh fruits and dark green, leafy vegetables (such as spinach and collard greens) may delay or reduce the severity of age-related macular degeneration. Taking anti-oxidants like Vitamins C and E may also have positive effects. Zinc, however, has shown mixed results. In some people, the long-term use of zinc causes digestive problems and anemia. Selenium is sometimes recommended, but you should always consult your physician to determine appropriate dosages. 

Sunlight - It has been demonstrated that the blue rays of the spectrum seem to accelerate macular degeneration more than other rays of the spectrum. This means that very bright light, such as sunlight or its reflection in the ocean and desert, may worsen macular degeneration. Special sunglasses that block out the blue end of the spectrum may decrease the progress of the disease.

In Conclusion:

1. If you have drusen, realize that most people with drusen develop no symptoms and do not progress to ARMD.

2. It is important to be followed closely by your eye doctor if drusen are present. Persons with drusen should also perform a self test (Amsler grid) on a routine basis to monitor for the presence of visual distortions.

3. Even in advanced cases of the more severe "wet" ARMD, peripheral vision is normally unaffected and mobility is good. "White-cane" blindness is rare.

4. Always consult with an eye doctor at the first sign of any blurred or distorted central vision.