Macular Degeneration

Age-related macular degeneration (AMD) is the most common cause of visual loss in developed countries in individuals over the age of 60. It is estimated that by the year 2000, more than 2 million people in the United States will be afflicted with this serious sight-threatening disorder.


The retina is a complicated network of nerve cells that changes light into nerve impulses that travel to the brain where they are interpreted as visual images. The central part of the retina is called the macula and is responsible for vision that is needed for reading and other detailed work. Damage to the macula results in poor vision. The most common disease process that affects the macula is age-related macular degeneration (AMD). In patients with AMD, retinal cells in the macula die over the course of several years. The cell death and gradual visual loss usually do not begin until age 60 or older and hence the name age-related macular degeneration. It is not known why the cells die, but two clues suggest that genetic defects called mutations may be involved. One clue is that AMD runs in families and another clue is that AMD shares some features with other retinal degenerations known to occur from mutations.

Dry Macular Degeneration

Patients who are affected by the dry form of macular degeneration have gradual loss of central vision due to the death of nerve cells in the macular region. This is unfortunate because the macula is the center portion of the retina that is responsible for reading and other complex visual tasks. Therefore, patients with AMD gradually lose their central vision along with it the ability to drive and read. As bad as this may seem, it is a gradual process and is compatible with reasonable functioning for many years. Patients will never go completely “blind” (absolute loss of vision) from macular degeneration. The patient will maintain peripheral vision.

Wet Macular Degeneration

There is another aspect of AMD that is even more devastating. As the nerve cells slowly degenerate, there is a tendency for blood vessels to grow into an abnormal location beneath the retina. This abnormal new blood vessel growth is called choroidal neovascularization (CNV). The abnormal blood vessels leak and bleed, resulting in sudden and severe loss of central vision. Depending on the location, laser treatment can sometimes be given to destroy the blood vessels. Only 15% of the cases of wet AMD are eligible to have laser treatment because the blood vessels can not be located too close to the center part of the macula. The laser is a beam of light that is absorbed by the RPE cells and changes to heat energy that cauterizes the abnormal blood vessels. Often times the blood vessels come back and result in severe loss of vision. In fact, most of the patients with AMD, who have very poor vision, have it as the result of abnormal blood vessel growth. Currently, there is no treatment available that prevents the cell death or abnormal blood vessel growth that occurs in AMD.
Only 10% of patients with AMD have the wet type, but it is responsible for 90% of all blindness resulting from AMD.

The Macular Photocoagulation Study (MPS) Showed that if patients are eligible for laser photocoagulation, treatment is better than no treatment. But, both groups of patients lost a significant amount of vision

Social and Economic Implications

Since ARMD results in loss or impaired central vision, it is not surprising that the majority of patients either become partially sighted or legally blind. Activities which require good central vision such as reading, writing and carrying out certain domestic tasks are all affected. Many macular degeneration patients require help to perform activities of daily living. Sometimes, their visual handicap necessitates admission to a nursing home. At the vision clinic we provide low vision aids to help the patient maintain independence for as long as possible.

Diet and Vitamins

It is important to note that cigarette smoking, sun exposure, high blood pressure, and high cholesterol have been thought to increase your risk of macular degeneration.
In contrast, antioxidant containing foods are thought to be beneficial for patients with macular degeneration. The most popular antioxidants, called carotenoids (are the pigments which give fruits and vegetables their color). Two such carotenoids are found in the macula (Lutein and Zeaxanthin)
A recent prospective study of 3,640 patients called the Age-Related Eye Disease Study (AREDS) suggests that anti-oxidants and vitamins help prevent the progression of macular degeneration and vision loss.

Vitamins

Vitamins C, E, beta-carotene and Zinc are proposed as dietary supplements to protect the retina from macular degeneration (always remember when taking Zinc to also take copper to help prevent anemia). The AREDS study supports the use of these supplement's.

Sunglasses and Ultraviolet Radiation

The sun gives off many forms of energy. Visible light from the sun helps us see the world around us. Other forms of light are not visible to the eye. These include ultraviolet (UV) light and infrared (IR) light. Even though these forms of light are not visible to the eye, they are still absorbed by the eye and the eye lids. When all forms of light are absorbed by the body, a reaction occurs which results in heat and chemical changes. Ultraviolet light rays are particularly energetic and cause more chemical reactions (damage) in ocular tissues than visible light. Ultraviolet (UV) Light Exposure Contributes to: Macular degeneration, eye cancer, cataracts.
Occupational Exposure to UV is Related To Sun Exposure:
Example: Truck driver, Mailperson, park ranger, construction, logger, farmer

Sunglasses

Sunglasses should block all UVA, UVB, and UVC rays. Be careful and ask for 100% UV protection. If you have a high-risk profession, or have already had an eye disease related to sun exposure, consider buying "wraparound" glasses, and wearing a hat.

How the Vision Clinic can help

Other Resources

Macular.org
Macular Degeneration.net
Eye Sight.org

We encourage you to visit these sites as they can answer many of your questions and also contain links to support groups.