Age-Related Macular Degeneration
What is AMD?
Age-related macular degeneration (AMD) is one of the most common causes of poor vision after age 60. AMD is a deterioration or breakdown of the macula. The macula is a small area at the center of the retina in the back of the eye that allows us to see fine details clearly and perform activities such as reading and driving.
The visual symptoms of AMD involve loss of central vision. While peripheral (side) vision is unaffected, with AMD, one loses the sharp, straight-ahead vision necessary for driving, reading, recognizing faces, and looking at detail. Early AMD changes can be detected at home with the use of an Amsler grid. Patients should test one eye at a time, covering the other eye and looking at the grid. If the lines of the grid appear wavy, distorted or missing, the test is abnormal and the finding should be investigated by an optometrist or ophthalmologist.
Although the specific cause is unknown, AMD seems to be part of aging. While age is the most significant risk factor for developing AMD, heredity, blue eyes, high blood pressure, cardiovascular disease, and smoking have also been identified as risk factors. AMD accounts for 90% of new cases of legal blindness in Canada.
Nine out of 10 people who have AMD have atrophic or “dry” AMD, which results in thinning of the macula. Dry AMD takes many years to develop. A specific vitamin regimen based on the AREDS (Age Related Eye Disease Study) has been shown to slow progression of dry AMD.
Exudative or “wet” AMD is less common (occurring in one out of 10 people with AMD) but is more serious. In the wet form of AMD, abnormal blood vessels may grow in a layer beneath the retina, leaking fluid and blood and creating distortion or a large blind spot in the center of your vision. If the blood vessels are not growing directly beneath the macula, laser surgery is usually the treatment of choice. The procedure usually does not improve vision but tries to prevent further loss of vision. For those patients with wet AMD whose blood vessels are growing directly under the center of the macula, intravitreal injections with an anti-vascular endothelial growth factor agent called Lucentis (ranibizumab) has been shown to preserve vision in 95% of patients and restore or partially restore it in 40% of patients. A procedure called photodynamic therapy (PDT), is also sometimes used. Intravitreal injections of other medications can also be used in some cases.
Age-related macular degeneration (AMD) is a disease caused by damage or breakdown of the macula, the small part of the eye’s 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.
Although the exact causes of AMD are not fully understood, a recent scientific study shows that antioxidant vitamins and zinc may reduce the effects of AMD in some people with the disease.
Among people at high risk for late-stage macular degeneration (those with intermediate AMD in both eyes or advanced AMD in one eye), a dietary supplement of vitamins C, E, and beta-carotene, along with zinc, lowered the risk of the disease progressing to advanced stages by about 25% to 30%. However, the supplements did not appear to benefit people with minimal AMD or those with no evidence of macular degeneration.
Light may affect the eye by stimulating oxygen, leading to the production of highly reactive and damaging compounds called free radicals. Antioxidant vitamins (vitamins C and E and beta-carotene) may work against this activated oxygen and help slow the progression of macular degeneration.
Zinc, one of the most common minerals in the body, is very concentrated in the eye, particularly in the retina and macula. Zinc is necessary for the action of over 100 enzymes, including chemical reactions in the retina. Studies show that some older people have low levels of zinc in their blood. Because zinc is important for the health of the macula, supplements of zinc in the diet may slow down the process of macular degeneration.
The levels of antioxidants and zinc shown to be effective in slowing the progression of AMD cannot be obtained through your diet alone. These vitamins and minerals are recommended in specific daily amounts as supplements to a healthy, balanced diet.
It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision 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. It is also important to note that current smokers and new non-smokers should not take supplements containing beta-carotene, as in these patients; beta-carotene increases the risk of developing lung cancer. You should speak with your ophthalmologist to determine if you are at risk for developing advanced AMD and to learn if supplements are recommended for you.
Anti-VEGF treatment is a way to slow vision loss in people who have a condition known as “wet” age-related macular degeneration (AMD).
Researchers have found that a chemical called vascular endothelial growth factor, or VEGF, is critical in causing abnormal blood vessels to grow under the retina. Scientists have developed several new drugs that can block the trouble-causing VEGF. These are referred to as “anti-VEGF” drugs, and they help block abnormal blood vessels, slow their leakage, and help reduce vision loss.
Treatment with the anti-VEGF drug is usually performed by injecting the medicine with a very fine needle into the back of your eye. Prior to injection. Usually, patients receive multiple anti-VEGF injections over the course of many months. In 95% of patients receiving these injections, further vision loss is arrested. About 40% of AMD patients experience visual improvements with these injections, with some patients gaining significant amounts of vision. Complications with this procedure are rare, but include retinal tear (1%) and infection (0.1%). For most people, the benefits of this treatment outweigh the small risk of complications. Anti-VEGF medications are a step forward in the treatment of wet AMD because they target the underlying cause of abnormal blood vessel growth.