Age Related Macular Degeneration
- Updated by Clement C, Chow, M.D.
Macular degeneration is a deterioration or breakdown of the macula. The macula is a small area in the retina at the back of the eye that allows you to see fine details clearly and perform activities such as reading and driving.
When the macula does not function correctly, your central vision can be affected by blurriness, dark areas or distortion. Macular degeneration affects your ability to see near and far, and can make some activities - like threading a needle or reading - difficult or impossible. Although macular degeneration reduces vision in the central part of the retina, it usually does not affect the eye's side, or peripheral, vision. For example, you could see the outline of a clock but not be able to tell what time it is. Macular degeneration alone does not result in total blindness. Even in more advanced cases, people continue to have some useful vision and are often able to take care of themselves. In many cases, macular degeneration's impact on your vision can be minimal.
What causes macular degeneration?
Many older people develop macular degeneration as part of the body's natural aging process. There are different kinds of macular problems, but the most common is age-related macular degeneration (AMD). Exactly why it develops is not known, and no treatment has been uniformly effective. Macular degeneration is the leading cause of severe vision loss in Caucasians over 65.
The two most common types of AMD are "dry" (atrophic) and "wet" (exudative):
"DRY" MACULAR DEGENERATION (ATROPHIC)
Most people have the "dry" form of AMD. It is caused by aging and thinning of the tissues of the macula. Vision loss is usually gradual.
"WET" MACULAR DEGENERATION (EXUDATIVE)
The "wet" form of macular degeneration accounts for about 10% of all AMD cases. It results when abnormal blood vessels form underneath the retina at the back of the eye. These new blood vessels leak fluid or blood and blur central vision. Vision loss may be rapid and severe. Deposits under the retina called drusen are a common feature of macular degeneration. Drusen alone usually do not cause vision loss, but when they increase in size or number, this generally indicates an increased risk of devel-oping advanced AMD. People at risk for developing advanced AMD have significant drusen, prominent dry AMD, or abnormal blood vessels under the macula in one eye ("wet" form).
What are the symptoms of macular degeneration?
Macular degeneration can cause different symptoms in different people. The condition may be hardly noticeable in its early stages. Sometimes only one eye loses vision while the other eye continues to see well for many years. But when both eyes are affected, the loss of central vision may be noticed more quickly. Following are some common ways vision loss is detected:
· words on a page look blurred;
· a dark or empty area appears in the center of vision;
· straight lines look distorted, as in the following diagram.
How is macular degeneration diagnosed?
Many people do not realize that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist (Eye M.D.) can detect early stages of AMD during a medical eye examination that includes the following:
· a simple vision test in which you look at a chart that resembles graph paper (Amsler grid);
· viewing the macula with an ophthalmoscope;
· taking special photographs of the eye called optical coherence tomography (OCT) or fluorescein angiography to find swelling, fluid, or abnormal blood vessels under the retina.
How is macular degeneration treated?
Although the exact causes of macular degeneration are not fully understood, antioxidant vitamins and zinc may reduce the impact of AMD in some people. A large scientific study (AREDS) found that people at risk for developing advanced stages of AMD lowered their risk by about 25% when treated with a high-dose combination of vitamin C, vitamin E, beta carotene and zinc. Among those who have either no AMD or very early AMD, the supplements did not appear to provide an apparent benefit. In the new AREDS 2 trial (published in 2013), adding DHA/EPA or lutein/zeaxanthin to the original AREDS formulation had no additional overall effect on the risk of advanced AMD. However, trial participants who took AREDS containing lutein/zeaxanthin and no beta-carotene had a slight reduction in the risk of advanced AMD, compared to those who took AREDS with beta-carotene. Also, for a subgroup of participants with very low levels of lutein/zeaxanthin in their diet, adding these supplements to the AREDS formulation helped lower their risk of advanced AMD. Finally, former smokers who took AREDS with beta-carotene had a higher incidence of lung cancer. The investigator found no significant changes in the effectiveness of the formulation when they removed beta-carotene or lowered zinc from 80 mg to 25 mg. 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 these supplements do play a key role in helping some people at high risk for advanced AMD to maintain their vision. 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.
Original AREDS formula
Beta-carotene 15 mg
Vitamin C 500 mg
Vitamin E 400 IU
Zinc 80 mg
Copper 2 mg
The formula that was used in the AREDS 2 study is as follows (per day)
Vitamin C 500 mg
Vitamin E 400 IU
Zinc 80 mg
Copper 2 mg
Lutein 10 mg
Zeaxanthin 2 mg
**Former smokers who took AREDS with beta-carotene had a higher incidence of lung caner
**Note that participants who took 25 mg of Zinc did similarly to those who took 80 mg of Zinc
**Also note that 350 mg DHA and 650 mg EPA did NOT lead to additional benefits in this study
There are many companies who sell ocular vitamins with slight variations in the formulation. We do not promote any brands/companies as long as the formula is the same (e.g. Bausch and Lomb PreserVision AREDS 2 formula)
If you are already taking the original AREDS formula and are not a smoker or former smoker, you can safely continue and finish what you have. If you are a smoker or former smoker, we would recommend you switching to the new AREDS 2 formula. Eventually the market will likely replace smoker and non-smoker formulas to the new AREDS 2 formula.
PHOTODYNAMIC THERAPY AND ANTI-VEGF TREATMENTS
A treatment called photodynamic therapy (PDT) uses a combination of a special intravenous drug followed by laser treatment to slow or stop leaking blood vessels. It is now rarely used since Anti-VEGF treatments became available in 2005. Anti-VEGF treatment targets a specific chemical in your body that is critical in causing abnormal blood vessels to grow under the retina. That chemical is called vascular endothelial growth factor (VEGF). Anti-VEGF drugs block the trouble-causing VEGF, reducing the growth of abnormal blood vessels and slowing their leakage. These procedures may preserve more sight overall, though they are not cures that restore vision to normal. Despite advanced medical treatment, many people with macular degeneration still experience some vision loss.
Adapting to low vision
To help you adapt to lower vision levels, your ophthalmologist can prescribe optical devices or refer you to a low-vision specialist or center. A wide range of support services and rehabilitation programs are also available to help people with macular degeneration maintain a satisfying lifestyle. Because side vision is usually not affected, a person's remaining sight is very useful. Often, people can continue with many of their favorite activities by using low-vision optical devices such as magnifying devices, closed-circuit television, large-print reading materials and talking or computerized devices.
Testing your vision with the Amsler grid
You can check your vision daily by using an Amsler grid like the one pictured here. You may find changes in your vision that you wouldn't notice otherwise. Putting the grid on the front of your refrigerator is a good way to remember to look at it each day.
To use the grid:
1. Wear your reading glasses and hold this grid 12-15 inches away from your face in good light.
2. Cover one eye.
3. Look directly at the center dot with the uncovered eye.
4. While looking directly at the center dot, note whether all lines of the grid are straight or if any areas are distorted, blurred or dark.
5. Repeat this procedure with the other eye.
6. If any area of the grid looks wavy, blurred or dark, contact your ophthalmologist immediately.
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Article published in the World Journal 世界日報 on Macular Degeneration in March, 2014
Adapted from American Academy of Ophthalmology, reprint with permission, updated by Clement C. Chow, M.D.
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