Age-related macular degeneration (AMD) is a general term for deterioration of the eye's macula due to aging. The macula is a small, specialized area of the retina - the light-sensitive tissue lining the inside of the eye. The macula is responsible for central and color vision.
The macula is much more sensitive to detail than the peripheral retina. Macular vision allows you to read text and differentiate people's facial features. The peripheral retina provides side (or peripheral) vision and detects movement.
A large percentage of senior people develop macular degeneration to some degree. Different diseases affect the macula, but the most common is age-related macular degeneration.
What causes Macular Degeneration?
Deterioration of normal body mechanisms due to aging allows for formation of deposits called drusen under the retina and, in some cases, growth of abnormal blood vessels that can leak and/or bleed. Cumulative damage from ultraviolet (UV) exposure and hereditary factors play a significant role in AMD as well. Macular degeneration alone rarely causes total blindness. People with advanced macular degeneration tend to maintain useful vision using their peripheral vision. In many cases, macular degeneration's impact on vision remains relatively minimal and manageable.
What are the symptoms of Macular Degeneration?
- Distorted reading vision
- Need for increasingly bright light to see up close
- Colors appear less vivid or bright and may differ between eyes
- Blank, blurry, or grey spots in central vision
- Lines that should be straight appear bent, crooked or irregular
- Object sizes appear different for each eye
When macular degeneration does lead to loss of vision it is often unilateral (just one eye). You may not notice vision changes if only one eye is affected, as your unaffected eye will compensate for vision loss. Both eyes may be affected over time. Many people are not aware that they have macular degeneration until they discover altered vision or until it is detected during a routine optometric eye examination.
Who is at risk for Macular Degeneration?
Recently, much new information on macular degeneration has been discovered. Genetic changes (predisposition) and age, both unavoidable, remain key risk factors. The risk of developing macular degeneration increases from approximately 2 percent for middle-aged people in their 50s to at least 40 percent in people over 75 years of age.
Normal body metabolism produces toxic molecules called free radicals. This oxidative stress is thought to play a major role in AMD. Approximately 1 in 3 Caucasians have genetics that make them more prone to damage from this source of inflammation. An overactive immune system also appears to be a significant risk factor for inflammation and AMD progression.
Heredity is a major risk factor for macular degeneration. People who have a close family member with the disease have a statistically greater chance of developing AMD.
Smoking and high blood pressure are associated with the "wet" form of macular degeneration. Research also suggests there may be a link between obesity and early or intermediate-stage macular degeneration developing into advanced forms.
How is Macular Degeneration diagnosed?
Because macular disease is painless, most people do not realize they have a problem until they notice significantly blurred or distorted vision. Regular eye exams by an optometrist (O.D.) or ophthalmologist (M.D.) help to detect problems or early stages of macular degeneration before you are even aware of them.
To check for macular degeneration, your eye doctor will dilate your pupils using eye drops and examine your eyes with an ophthalmoscope, a device that allows him/her to focus inside the eye. If early macular degeneration is detected, your doctor may have you use an Amsler Grid to monitor for such as wavy, blurry, or dark areas in and around your central vision.
Special testing is indicated if your ophthalmologist suspects you may have the "wet" form of macular degeneration. The most common studies are fluorescein angiography (FA) and optical coherence tomography (OCT).
During FA, a very safe fluorescein dye is injected into a vein in your hand or arm. The dye travels through the heart and lungs and then to your eyes. Timed photographs are taken as the dye passes through the retinal blood vessels. Abnormal vessels are highlighted by leakage. Your retinologist uses the information to diagnose and plan individualized treatment. Early diagnosis is key to best outcomes.
How is Macular Degeneration treated?
"Dry" (non-exudative) AMD
While there is no proven treatment for the "dry" form of AMD, a large scientific study has shown that antioxidant vitamins may reduce the impact of macular degeneration by slowing its progression towards more advanced stages.
The Age-Related Eye Disease Study (AREDS) showed that people at high risk for developing late-stage macular degeneration lowered their risk by taking a specified dietary supplement. This protocol reduced the risk by approximately 20 percent. Supplements did not appear to provide a benefit for people with minimal macular degeneration or people without evidence of the disease.
A large study evaluating the possible benefits of lutein and fish oil (omega-3) is ongoing. Other studies have shown that eating dark leafy greens and yellow, orange and other colorful fruits and vegetables rich in lutein and zeaxanthin may reduce the risk for developing macular degeneration.
Note that these vitamins and minerals are recommended in specific daily amounts in addition to a healthy, balanced diet. Some people may not wish to take large doses of antioxidants or zinc because of pre-existing medical reasons. Beta carotene has been shown to increase the risk of lung cancer in smokers or recent past smokers. Zinc supplements may worsen high cholesterol conditions.
It is very important to remember that vitamin supplements are not a cure for macular degeneration, nor will they restore vision that has already been lost from the disease. However, specific supplements do play a key role in helping some people at high risk for developing advanced AMD minimize vision loss.
"Wet" (exudative) AMD - Anti-VEGF medication injection
A common treatment strategy for wet macular degeneration targets a specific chemical in your body that causes abnormal blood vessels to grow and leak. That chemical is called vascular endothelial growth factor or VEGF. Several new drugs have been developed for wet AMD that block VEGF. Inhibiting VEGF reduces the growth of abnormal blood vessels, slows their leakage, helps to slow vision loss, and, in some cases, actually improves vision.
"Wet" (exudative) AMD - Laser treatment
A significantly older form of treatment for select cases of wet AMD is thermal laser therapy. Laser treatment is performed as an office procedure. A highly focused beam of specific wavelength produces a small burn which closes abnormal blood vessels. The goal is to trade a small scar for otherwise uncontrolled leakage.
Approximately 50 percent of patients with wet macular degeneration who undergo standard thermal laser will need re-treatment for persistent and/or recurrent leakage.
"Wet" (exudative) AMD - Photodynamic therapy (PDT)
A photosensitive drug is injected into a vein in your hand or arm and travels throughout the body. Abnormal vessels typically absorb the photosensitizer more than normal blood vessels. A non-thermal ("cold") laser light is targeted directly on the macula to activate the drug. PDT is usually performed in the physician's office.
Blood vessels are programmed to remain open so multiple treatments may be required over time. PDT may be combined with anti-VEGF injections to treat "wet" AMD.
What happens when macular degeneration cannot be treated?
It is important to remember that only about 10 percent of all macular degeneration cases are exudative ("wet"). The great majority of these can be managed with office-based treatment.
If you have untreatable macular degeneration, you can make the most of your remaining vision with the help of special low-vision rehabilitation, devices and services. People with low vision can learn new strategies to accomplish daily activities. These skills, including mastering new techniques and devices, help people with advanced AMD regain their confidence and often live independently despite loss of central vision.