An in-depth look at macular degeneration and how it develops, what causes it, how to treat it and much more.
What is Macular Degeneration?
Macular degeneration is commonly referred to as age-related macular degeneration, or AMD, due its tendency to affect older adults. Some cases of macular degeneration are mild and hardly affect vision at all, while other cases are severe enough to cause a large central blind spot. While most people consider this eye disease scary, it actually does not affect the entire retina. Therefore, it cannot cause total blindness by itself. Most people, even those who are severely affected, are still able to maintain a normal lifestyle and care for themselves.
This disease affects the macula, which is the part of the retina that allows you to see straight ahead and in fine detail. The macula is also the most sensitive part of the retina. By the age of 65, the macula begins to degenerate or deteriorate in one out of every four people, and in one out of every three people over the age of 80. In most cases both eyes have the disease, but it is more advanced in one eye than the other.
Types of Macular Degeneration
There are two types of macular degeneration: wet and dry. Wet macular degeneration accounts for only 10 percent of all cases, and occurs when tiny abnormal blood vessels begin growing behind the retina, toward the macula. These abnormal blood vessels leak blood and fluid, damaging the macula and causing severe and rapid vision loss. Wet macular degeneration is much more severe than the dry form.
Dry macular degeneration occurs when small, yellowish deposits called drusen begin accumulating beneath the macula. The drusen gradually break down the light-sensing cells within the macula, which leads to distorted vision in the eye.
Macular Degeneration Symptoms
Symptoms of dry macular degeneration include blurry vision and a small blind spot in the central field of vision. As time passes, the small blind spot grows larger and affects vision further,making it harder to read fine print or see details. Symptoms of wet macular degeneration include distorted shapes. The distortion is caused by fluid from leaking blood vessels that collects under the macula and lifts it.
Regardless of which type of macular degeneration you have, common symptoms of both include:
- Decreasing visual acuity
- Difficulty seeing in bright environments (photophobia)
- Difficulty adjusting from darkness to light
- Hallucinations of geometric shapes (in advanced cases)
- No pain
Diagnosing Macular Degeneration
To diagnose macular degeneration, a complete eye examination with an ophthalmoscope or a slit lamp may be all that is necessary. Occasionally, a fluorescein angiography may be performed. During this procedure, your eye doctor will inject dye into a vein and take photographs of your retina. A visual acuity test will help determine if any central vision has been lost. An Amsler grid may also be used to detect either type of macular deneration. In this test you cover one eye and stare at a black dot that is surrounded by a pattern of straight lines. If these lines appear wavy or are missing, you may be suffering from macular degeneration.
What Causes Macular Degeneration?
As of 2013, the cause for macular degeneration remains unknown. However, many experts believe certain risk factors contribute to its development. See below.
Risk Factors for Macular Degeneration
The following risk factors are known to correlate with the development of macular degeneration. They include:
- Genetics or family history of the disease
- Race: macular degeneration is more common among Caucasians, though it occurs to all races
- Skin pigmentation: fairer or lighter skinned people are at a higher risk
- Eye color: those with lighter eyes are at a higher risk than those with dark colored eyes
- Prolonged exposure to sunlight or other types of ultraviolet light
- Obesity or a fatty diet
- Sleep apnea
- Gender: women seem to be at greater risk than men
- Living near the equator or at higher altitudes
- Some medications, such as Fosamax for osteoporosis
- Severe myopia
- Cardiovascular disease
Macular Degeneration Treatment
It is important to note that there is no specific treatment for dry macular degeneration, since most severe vision loss is due to wet macular degeneration. If a patient is diagnosed with the dry form, preventive steps are usually taken to prevent the disease from advancing.
Taking a high-dose formulation of antioxidants and zinc slows the progression of macular degeneration significantly. According to the research done by the NEI, “The specific daily amounts of antioxidants and zinc used by the study researchers were 500 milligrams of vitamin C, 400 International Units of vitamin E, 15 milligrams of beta-carotene (often labeled as equivalent to 25,000 International Units of vitamin A), 80 milligrams of zinc as zinc oxide, and two milligrams of copper as cupric oxide. Copper was added to the AREDS formulation containing zinc to prevent copper deficiency anemia, a condition associated with high levels of zinc intake.” This high level of antioxidants is virtually impossible to achieve with diet or daily doses of multi-vitamins.
In the past, wet macular degeneration was treated with laser surgery to destroy the new blood vessels before they caused any more damage. But this process also caused more vision loss as it damaged nearby tissue. Then new blood vessels formed and more treatments were needed. Treatment for wet macular degeneration has significantly advanced since then. New medicines have been developed to stop problematic blood vessels from forming. These new medicines, called anti-angiogenic or anti-vascular endothelial growth factor drugs, are also known to improve treatment. The two most common are Avastin and Lucentis. The medicine is injected into the eyeball and takes effect immediately, although injections are typically repeated every month or two until the disease is stabilized.
Preventing Macular Degeneration
Prevention of macular degeneration means reducing UV exposure and eating a healthy diet containing plenty of antioxidants and zinc. Eating foods rich in Vitamins A, C, and E may also help reduce your chances of developing this disease. A study conducted by the National Eye Institute suggests that lutein and zeaxanthin (nutrients found in eggs and green vegetables) may also be protective against the disease. Exercising and staying healthy are always a good way to prevent all diseases. For more information on nutrition and eye care visit our eye care nutrition pages.
If macular degeneration has already caused vision loss, it may be best to contact a low vision specialist. Low vision specialists can be found in communities worldwide, and can help you make the most of what vision you have left.
Additional ways to prevent macular degeneration include:
- Wear sunglasses
- Avoid alcohol when possible
- Avoid all types of sugars when possible
- Avoid excessive saturated fats and foods containing fats and oils that have been subjected to air or heat (lunch meats, hamburgers, fried foods, etc.)
- Increase your consumption of legumes
- Watch your weight and blood pressure, especially as you get older
Complications of Macular Degeneration
Macular degeneration can cause varying degrees of vision loss. Some people diagnosed with this disease are able to maintain a normal lifestyle and require no significant treatment. Untreated or advanced macular degeneration can lead to severe vision loss or even blindness, however, which may complicate normal life. Simple tasks such as washing the dishes or watching TV may become too difficult. Complications can arise from the various forms of treatment for macular degeneration too. For example, injections into the eyeball can be painful and carry a small risk of infection, bleeding, and retinal detachment. Always consult with your doctor about the benefits and risks involved with treatment.
Talking to Your Eye Doctor
Here are some questions to ask your eye care professional about macular degeneration:
- Which type of macular degeneration do I have?
- Which treatment options are available for me?
- Based on my individual needs, what should my diet consist of?
- What other preventive measures can I take to avoid this disease?
- If my grandma has macular degeneration, how likely is it that I will develop it?
- Am I at a higher risk than others? Why?
- Do you know of a local support group for those with low vision?
- Can you refer me to a low vision specialist?
- How often should I schedule visits to see you?
- J. Weizer, MD, J. Stein, MD, MS “ The Reader’s Digest Guide to Eye Care” (Quantum Publishing Ltd, 2009) 60-63
- M. Beers, MD “The Merck Manual of Medical Information” 2nd Home Edition (Pocket Books, 2003) 1310-1311
- American Health Assistance Foundation, Macular Degeneration Research, April 29,2011, Gene Therapy Shows Promise Against Age-Related Macular Degeneration, http://www.ahaf.org/macular/newsupdates/gene-therapy-shows-promise.html
- J. Anshel, MD “Smart Medicine for Your Eyes” (SquareOne Publishers, 2011) 263-269