The macula is a small but vital part of the retina. The macula is responsible for your central vision. When you read, thread a needle, or perform any other activity that requires you to see fine details, you are using your macula. When the macula does not function as it should, objects appear distorted, blurry or may seem to disappear. Macular degeneration reduces central vision but generally does not affect peripheral vision or cause total blindness.
Age-related macular degeneration is the leading cause of severe vision loss in the United States. About 1 in 10 Americans between 66 and 74 years of age has macular degeneration and this increases to 30% of those older than 75. The majority of patients with this disease have the “dry” or atrophic version of this disease. These patients experience thinning of the tissues of the macula and the accumulation of abnormal deposits called drusen underneath the retina. Vision loss in this form tends to be gradual. Patients with many and large drusen are at increased risk of severe visual loss and development of the “wet” form of the disease. Wet or exudative macular degeneration affects one in ten patients with macular degeneration. It accounts for the majority of cases of blindness from this disease. Abnormal blood vessels form in the choroid, the layer just underneath the retina. These new, abnormal blood vessels leak fluid and blood into the macula and can cause sudden and severe vision loss.
Macular degeneration is a complex disease with a strong hereditary component. The lifetime risk of developing macular degeneration is 50% for people with a close relative who has the disease. Multiple genes have been associated with a susceptibility to macular degeneration. Defects in the gene for complement factor H are estimated to be present in over 40% of patients with macular degeneration. Complement factor H defects are associated with a higher likelihood of inflammation in the retina. A person who inherits one abnormal gene from a parent has a two to three fold increase in likelihood of developing macular degeneration. If a person inherits an abnormal gene from each parent, their risk of developing the disease increases seven-fold. Thirty-five percent of people are estimated to have 1 or 2 abnormal copies of complement factor H. Defects in several other proteins, complement factor B and factor 3 are also associated with the development of macular degeneration. Work is on-going to tease out all of the genes that are associated with macular degeneration. At the current time, genetic testing for patients or family members is not recommended, nor are there any treatments that address the underlying genetic defects.
Aside from genetic factors (over which an individual has no control), smoking is the strongest risk factor for the development of macular degeneration. British studies have shown that 25% of patients with severe vision loss from macular degeneration are smokers. Smoking tobacco or living with a smoker increases an individual’s risk of developing macular degeneration by two to three fold. Avoiding smoking is critical for patients with macular degeneration and their family members.
The Age-Related Eye Disease Study (AREDS) was completed in 2001 and showed that patients with moderate macular degeneration in at least one eye benefited from vitamin supplements by a reduction in the rate of progression of the disease by about 25%. Patients with mild macular degeneration and family members without the disease did not show any benefit from this intervention when it was taken for an average of six years. The vitamins used in this study were vitamin C (500 mg), vitamin E (400 IU), vitamin A as beta-carotene (15 mg/25,000 IU), zinc (80 mg), and copper oxide (2 mg).
Smokers and former smokers should not take any supplements containing beta-carotene because of an increased risk of the development of lung cancer. Vitamin E acts as a mild blood thinner. People with bleeding disorders or on other blood thinners should use it with caution. High doses of zinc can cause prostate enlargement. Zinc in doses exceeding 50 mg a day can cause a copper deficiency. Supplementation with 1-2 mg of copper is advisable. Copper gluconate and copper sulfate are better absorbed than copper oxide. If you have copper water pipes in your home, you may not need an additional supplement.
The best way to increase your antioxidant intake is through dietary sources. A minimum of 5 servings of the following vegetables per week (especially the dark green leafy vegetables (members of the cabbage family, mustard greens, spinach and collards) were shown in 1994 to decrease the onset of macular degeneration. Each serving was 3.5 ounces or 3 cups of uncooked vegetables. A serving of nuts is a dozen.
Beta-carotene: cabbages (broccoli, broccoli rabe, brussel sprouts, kale), collards, mustard greens, spinach, red peppers, carrots, avocados, asparagus, squash, sweet potatoes, nectarines, apricots, cantaloupe, mango, papaya, watermelon, kiwi
Vitamin C: spinach, mustard greens, collards, red and green peppers, cabbages, turnips, citrus fruits, cantaloupe, kiwi
Vitamin E: seeds, nuts and whole wheat grains
Zinc: oysters, fish, pumpkin seeds, ginger root, pecans, Brazil nuts
Copper: Brazil nuts, almonds, hazelnuts, walnuts, pecans
Lutein and zeaxanthine are pigments present in the macula which absorb blue and UV light. Dietary intake of lutein (which the body converts to zeaxanthine) as low as 2.4 mg a day can increase the amount of pigment present in the macula. At this time the evidence that increasing the amount of pigment in the macula will decrease the severity of macular degeneration is suggestive but has not been proven. Lutein also may decrease the progression of cataracts and has no documented adverse health effects at doses under 30 mg a day. The AREDS2 study (2006 to 2013) studied the role of lutein and zeaxanthine in the prevention of macular degeneration. The doses used in this study were 10 mg of lutein and 2 mg of zeaxanthine daily. AREDS2 showed that lutein and zeaxanthine were as effective as Beta carotene in preventing progression of macular degeneration. Lutein is safe for smokers and former smokers to take. Dietary sources of lutein are: kale, collards, spinach, fresh parsley, mustard greens, fresh dill, celery, scallions, leeks, broccoli, lettuce, green peas, pumpkin, brussel sprouts, squash, yellow corn, peppers, green beans, cucumber pickles, green olives, and egg yolks.
The waste products which accumulate in macular degeneration are rich in fats. In late 2001, a study showed that people with diets weighted toward omega-3 fatty acids have less macular degeneration. Omega-3 fatty acids are antioxidant compounds that reduce inflammation in the body. Omega-3 fatty acids are very abundant in coldwater fish like salmon, mackerel, sardines, herring and cod. Flaxseed oil and nuts are also high in omega-3 fatty acids. The AREDS2 study also examined the effect of a 1 gram supplement of omega-3 fatty acids daily, but did not find any benefit at this dose over a period of 5 years. The FDA recommends limiting omega-3 fatty acid intake to 3 grams per day, with no more than 2 g coming from supplements. Omega-3 fatty acids have been linked to increased bleeding risk. Patients with clotting disorders or who take blood thinners should be closely monitored while using this supplement and it should be stopped several days before any scheduled surgery.
Wet macular degeneration has been treated since 2005 with injections of chemicals that block vascular endothelial growth factor (VEGF). These medications, Avastin and Lucentis, have revolutionized the treatment of this disease by preventing the growth of abnormal blood vessels. Around 90% of treated patients maintain their vision while 40% experience an improvement in their vision. Unfortunately, these medications often require repeated injections as frequently as every four weeks to maintain these results.
Research is continuing to produce more effective and longer lasting treatments but we do not have a cure. Many people with macular degeneration will still experience vision loss. Most activities can be continued by using a variety of low-vision devices, including magnifiers, large print materials and electronic or talking aides.
Patients with a family history of macular degeneration will often ask how they can decrease their risk of developing this disease. In June of 2011, the Rotterdam Study (Netherlands) published information that higher dietary intake of several nutrients was associated with decreased risk of developing macular degeneration. This study was of individuals 55 years of age and older, and was designed to investigate various chronic diseases. The average patient participated in the study for 8.6 years. Of the nearly 7,000 participants, 10% were diagnosed with macular degeneration during the study. Once the diagnosis was made, an analysis of the diet over the previous 1 year was performed. This analysis showed that patients with the highest intake levels of the following nutrients had the lowest risk of developing macular degeneration. The average daily intakes of these nutrients in the group with the lowest risk were:
- Zinc (RDA of 10 mg/day for males, 9 mg/day for females) intake was 11.8 mg
- Beta-carotene (no RDA) intake of 5.7 mg/day
- Lutein/Zeaxanthine (no RDA) intake of 3.3 mg/day
- Omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (RDA 450 mg/day),
intake of 300 mg/day
It has been recommended that in addition to avoiding smoking, people with a family history of macular degeneration eat a diet as detailed above and take a multivitamin daily.