Macular degeneration is a slowly progressive disease that causes a reduction in central vision. In the early stages of the disease, the effect on vision may be minimal or unnoticeable. As the disease progresses, fine details become more difficult to see, especially when reading small print.
Vision may also appear distorted or parts of an object may appear to be missing. It is extremely important to remember that some patients are at risk for vision loss even if no symptoms are present.
There is no pain associated with macular degeneration. Risk factors for macular degeneration include age, genetics, ethnicity, smoking, obesity, and high cholesterol.
Types of Macular Degeneration
There are two forms of macular degeneration: dry and wet. In the dry form, which is more common, small deposits called drusen develop under the macula, causing mild to moderate decrease in vision. In the wet form, abnormal blood vessels grow under the retina and leak, causing a scar to develop. This can result in severe vision loss.
Treating Macular Degeneration
At this time, there is no cure for macular degeneration, but the doctors at Philadelphia Retina Associates offer solutions to slow down the progression of the disease. For patients with the dry form of macular degeneration, lifestyle modifications will be recommended, including:
- Maintaining ideal body weight and cholesterol level
- Vitamin and mineral supplements
- Dietary modifications
- Stopping smoking
- Self-monitoring to detect any changes in vision
- Routine eye examinations
Patients with the wet form of macular degeneration can benefit from intravitreal injections with the latest specialized medications as well as argon green, red, and yellow laser therapy.
Please visit our patient education library to learn more about age-related macular degeneration (AMD) or read our FAQs below.
FAQs about Age-Related Macular Degeneration (AMD)
There are two forms of AMD: dry (also known as non-exudative or non-neovascular AMD) and wet (also known as exudative or neovascular AMD).
Dry AMD is the more common manifestation, accounting for about 90% of all cases. It develops slowly and is characterized by the death of critical cells in the macula, the central part of the retinal lining of the eye that allows you to see fine detail. Dry AMD often causes mild vision loss. Many eyes with the dry type remain dry indefinitely. However, some will progress to the wet stage.
Wet AMD is the less common variety, accounting for about 10% of all cases. However, this form is a much greater threat to central vision, and accounts for about 90% of severe vision loss from AMD.
In the early stages, abnormal new blood vessels (subretinal or choroidal neovascularization) grow underneath the macula. These often leak fluid and blood, causing disturbance of central vision. Later, degeneration of the overlying light-sensitive retinal cells (photoreceptors) occurs. As the condition progresses, scar tissue can eventually form in the macula, causing a blind spot in the center of vision.
It is believed that macular degeneration is caused by the interaction of a multitude of factors, broadly grouped into several categories.
- Age is the major risk factor, with people over age 60 at greater risk than other age groups.
- Genetic factors play a role. Scientists have identified several gene mutations that increase the risk of AMD and others that protect against it.
- Smoking cigarettes is a major risk factor, doubling, tripling, and in some studies, quadrupling the chances of developing the more advanced stages of AMD.
- Some studies have shown an association between AMD and cardiovascular disease, obesity, and lack of physical activity.
- Nutritional factors play a role, with increased intake of certain items being protective, and others being potentially harmful. (Some of these are addressed in the prevention section below.)
Many patients with the earlier stages of AMD in both eyes have no symptoms. And, many patients with even more advanced stages of the disease in one eye but not in the other will not be aware of symptoms.
The only way to know for sure whether you have AMD is to have a thorough eye examination. This will involve measurement of your visual acuity (by reading the eye chart), examination of the front of the eye with a microscope, checking the eye pressure, and dilation of the pupils to allow for a complete view of the macula, the rest of the retina, and other structures in the back of the eye.
Your eye care professional can determine if you need additional special testing, such as optical coherence tomography or fluorescein angiography.
As the disease progresses, the gradual onset of slightly blurred vision or a blurred spot in the center of vision is the most common symptom of dry AMD. Over time, this blurred spot may become larger and the sharpness of vision within the spot can decrease further. Affected individuals may need more light for reading and other tasks.
Wet AMD may also cause blurred or fuzzy vision. In addition, straight lines, such as telephone poles, or the sides of buildings may appear wavy. A grid pattern, such as the tiles in your bathroom or an Amsler grid, may appear distorted.
The onset of symptoms in wet AMD is often sudden, in contrast to dry AMD. Over time, a dark or “empty” patch may appear in the center of vision as photoreceptor degeneration and scarring occurs.
Patients with loss of center vision in both eyes notice difficulty seeing details such as print on a page or on TV, or the facial features of people across the room. However, blindness is not an expected result, since the peripheral, or side, vision is typically unaffected.
Even with pronounced loss of center vision in both eyes, most patients with advanced AMD can see where they are walking and can do most things needed to take care of themselves. One notable exception is driving. For safety reasons, driving requires a certain degree of central vision determined by laws of the particular state in which one resides, in addition to peripheral vision.
While there is no sure way to prevent AMD, certain lifestyle changes can lower the risk to some degree. These would include:
- Eat a healthy diet high including green leafy vegetables; yellow, orange, and red vegetables; fish; and nuts.
- Lower your intake of red meat and processed snack foods and baked goods, since the fats found in some of these may be harmful.
- Don't smoke.
- Watch your weight.
- Control your blood pressure.
The National Eye Institute's Age-Related Eye Disease Study (AREDS) found that taking a specific high-dose formulation of antioxidants and zinc can significantly delay and possibly prevent the intermediate stage of dry AMD from progressing to the advanced stage, in which vision loss occurs.
The specific daily amounts of antioxidants and zinc used by the study researchers were 500 mg of vitamin C, 400 IU of vitamin E, 15 mg of beta carotene (often labeled as equivalent to 25,000 IU of vitamin A), 80 mg of zinc as zinc oxide, and two mg of copper as cupric oxide.
Therefore, people who are at high risk for developing advanced AMD should consider taking the AREDS formulation. Only a thorough eye examination can tell you if you have AMD, its stage, and your risk for developing the advanced form.
Of note, smokers should not be on any beta carotene supplementation due to an increased risk of lung cancer. There are modifications of the AREDS formula available that do not have beta carotene that are appropriate for smokers.
It is best to detect any progression to the wet stage as soon as possible, since that improves the prognosis for treatment. Early detection of changes requires not only regular eye examinations with dilation of the pupils, but also the participation of the patient in his or her own monitoring, by testing the vision with an Amsler grid and a reading test with reading glasses on, one eye at a time, every week.
Any increase in distortion of the straight lines on the grid, missing lines on the grid, or decrease in ability to read a line on a reading test that could previously be seen would be a reason to promptly schedule a retinal examination to be sure there has been no progression of the AMD to the wet stage requiring treatment.
There is not yet a treatment for dry AMD that can reverse the condition or restore any lost vision. However, the lifestyle changes noted above and taking the AREDS formula nutritional supplement can reduce the risk of progression of intermediate stage dry AMD to the more advanced stages with more significant visual loss.
The Age-Related Eye Disease Study II is evaluating the role of modifications of the original AREDS formula nutritional supplement and determining if supplemental omega 3 long-chain fatty acids or supplemental lutein or zeaxanthin will be of benefit. At this point, we don’t yet have evidence to say if adding to the original AREDS supplement or changing it in any way will be useful.
For the wet stage of AMD, several approved treatments are available, including laser therapy, photodynamic therapy, and, more recently, drugs that can be injected into the eye after making it numb.
The drugs available to date inhibit VEGF, a factor known to be important in encouraging the growth of abnormal blood vessels and the leakage from those vessels, the hallmark of the wet stage of AMD. The currently used anti-VEGF drugs can stabilize vision in most eyes and even improve vision in a minority of cases, although they require multiple injections for an indefinite period of time.
Looking at what future treatment strategies may be of benefit, scientists are:
- Studying the possibility of transplanting healthy cells into a diseased retina
- Evaluating families with a history of AMD to understand genetic and hereditary factors that may cause the disease
- Looking at certain anti-inflammatory treatments for the wet form of AMD
- Evaluating the role of neuroprotective and stem cell technologies
- Looking at the potential role of augmenting anti-VEGF therapies with low power laser or radiation therapy
- Evaluating the role of gene manipulative therapies
This research should provide better ways to detect, treat, and prevent vision loss in people with AMD.
For patients with persistent visual decrease, low vision training is available. Low vision rehabilitation involves using specific magnifying optical devices and lighting aids to assist in performing specific vision functions.
Although low vision aids are no cure for AMD, they may be helpful in performing essential visual tasks, enabling people to perform normal activities of daily living, and lead independent lives.