Age-related macular degeneration (AMD) is a disease caused by damage or breakdown of the macula, a small part of the retina that is responsible for our central vision. This condition affects both distance and close vision and can make some activities (like threading a needle or reading) very difficult or impossible. Macular degeneration is the leading cause of severe vision loss in people over 65. Risk factors for macular degeneration include but are not limited to advancing age, family history of AMD and cardiovascular risk factors such as hypertension and cigarette smoking. Macular degeneration is exhibited in two forms: dry (nonexudative) and wet (exudative).
Dry AMD
Ninety percent of patients diagnosed with macular degeneration have the dry (nonexudative) form of AMD. Although dry AMD is the most common form of the disease, it only accounts for 10-20% of cases of severe vision loss. Types of vision loss from dry AMD include drusen (localized deposits of extracellular material)
and geographic atrophy (round or oval patches of atrophy of the retina, retinal pigment epithelium and underlying choroid).
Drusen do not usually cause visual symptoms but in rare cases, they have been known to cause blurring or distortion. On the other hand, geographic atrophy is responsible for nearly all cases of severe vision loss associated with dry AMD. Over time, areas of atrophy can become larger, more numerous and/or coalesce to form larger areas. Geographic atrophy tends to occur in both eyes but can be confined to one eye.
Wet AMD
Approximately 10% of patients with AMD develop the wet (exudative) form of the disease. This form of AMD accounts for 80-90% of cases of severe vision loss associated with AMD. Wet AMD is characterized by new blood vessel growth (neovascularization) from the choroid into the macula.
Neovascularization causes vision loss because the abnormal blood vessels that are formed do not have a tight outer layer which allows them to leak fluid and blood. On occasion, these abnormal blood vessels can hemorrhage as well. If left untreated, the neovascularization and associated leakage of blood and fluids can from a fibrovascular scar which will leave dead and/or damaged tissue in place of the normal, living tissue causing further vision loss. In some cases, dry AMD can develop into wet AMD.
Symptoms
Symptoms of either form of macular degeneration may present in various ways, however, common symptoms include:
- Blurry vision
- Distorted vision
- Straight lines appear wavy
- Objects may appear as the wrong shape or size
- The loss of clear, correct colors
- Difficulty reading
- A dark, empty area in the center of vision
Nutritional Supplements
Although the exact causes of AMD are not fully understood, the Age Related Eye Disease Study (AREDS) has demonstrated that antioxidant vitamins and zinc may reduce the impact of AMD in some people.
The study found that people at risk of developing advanced stages of AMD lowered their risk by about 25% when treated with a high-dose combination of Vitamin C, E, beta carotene and zinc. For those who have either no AMD or very early AMD the supplements did not appear to provide an apparent benefit.
The nutrient supplementation shown to provide a benefit by the AREDS contained: Vitamin C – 500mg, Vitamin E – 400IU, beta-carotene – 15mg, zinc oxide – 80mg, copper as cupric oxide – 2mg (to prevent copper deficiency which may be associated with high zinc supplementation.).
The levels of antioxidants and zinc that were shown to be effective in slowing AMD’s progression cannot be consumed through your diet alone. These vitamins and minerals are recommended in specific daily amounts as supplements to a healthy, balanced diet.
Some people may not wish to take large doses of antioxidants or zinc because of medical reasons. The study did not reveal any evidence of toxicity from the treatment. Beta-carotene however has been shown to increase the risk of lung cancer in smokers or recent past smokers.
It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision that you may have already lost from the disease. However, specific amounts of certain supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision.
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