Macular degeneration (also called AMD, ARMD, or age-related macular degeneration) is an age-related condition in which the most sensitive part of the retina, called the macula, starts to break down and lose its ability to create clear visual images. The macula is responsible for central vision – the part of our sight we use to read, drive and recognize faces. So although a person’s peripheral vision is unaffected by AMD, the most important aspect of vision is lost.
AMD is the leading cause of vision loss and blindness in Americans ages 65 and older. And because older people represent an increasingly larger percentage of the general population, vision loss associated with macular degeneration is a growing problem.
It’s estimated that more than 1.75 million U.S. residents currently have significant vision loss from AMD, and that number is expected to grow to almost 3 million by 2020.
The Two Forms of AMD
Macular degeneration can be classified as either dry (non-neovascular) or wet (neovascular). Neovascular refers to growth of new blood vessels in an area, such as the macula, where they are not supposed to be.
The dry form of AMD is more common – about 85% to 90% of all cases of macular degeneration are the dry variety.
Dry macular degeneration. Dry AMD is an early stage of the disease, and may result from the aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes.
Dry macular degeneration is diagnosed when yellowish spots called drusen begin to accumulate in the macula. Drusen are believed to be deposits or debris from deteriorating macular tissue. Gradual central vision loss may occur with dry AMD. Vision loss from this form of the disease is usually not as severe as that caused by wet AMD.
Two major studies conducted by the National Eye Institute (NEI) looked into the risk factors for developing macular degeneration and cataracts. The studies, called the Age-Related Eye Disease Study (AREDS) and AREDS2, showed that nutritional supplements containing antioxidant vitamins and multivitamins that also contain lutein and zeaxanthin can reduce the risk of dry AMD progressing to sight-threatening wet AMD.
Wet macular degeneration. Wet AMD is the more advanced and damaging stage of the disease. In about 10% of cases, dry AMD progresses to wet macular degeneration.
With wet AMD, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive cells in the retina, causing blind spots or a total loss of central vision.
The abnormal blood vessel growth in wet AMD is the body’s attempt to create a new network of blood vessels to supply more nutrients and oxygen to the macula. But the process instead creates scarring and central vision loss.
Macular Degeneration Signs and Symptoms
Macular degeneration usually produces a slow, painless loss of vision. Early signs of vision loss associated with AMD can include seeing shadowy areas in your central vision or experiencing unusually fuzzy or distorted vision. In rare cases, AMD may cause a sudden loss of central vision.
An eye care practitioner usually can detect early signs of macular degeneration before symptoms occur. Usually this is accomplished through a retinal examination.
What Causes Macular Degeneration?
Many forms of macular degeneration appear be linked to aging and related deterioration of eye tissue crucial for good vision. Research also suggests a gene deficiency may be associated with almost half of all potentially blinding cases of macular degeneration.
Who Gets Macular Degeneration?
Besides affecting older individuals, AMD appears to occur in whites and females in particular. The disease also can result as a side effect of some drugs, and it appears to run in families.
New evidence strongly suggests that smoking is high on the list of risk factors for macular degeneration. Other risk factors for AMD include having a family member with AMD, high blood pressure, lighter eye color and obesity. Some researchers believe that over-exposure to sunlight also may be a contributing factor in development of macular degeneration. A high-fat diet also may be a risk factor.
How Is Macular Degeneration Treated?
There is as yet no outright cure for macular degeneration, but some treatments may delay its progression or even improve vision.
There are no FDA-approved treatments for dry AMD, although a few now are in clinical trials. While nutritional intervention may be valuable in preventing the progression of dry AMD to the more advanced, wet form, neither the AREDS1 nor the AREDS2 study demonstrated any preventive benefit of nutritional supplements against the development of dry AMD in healthy eyes.
For wet AMD, several FDA-approved drugs are designed to stop abnormal blood vessel growth and vision loss from the disease. In some cases, laser treatment of the retina may be recommended. Ask your eye doctor for details about the latest treatment options for wet AMD.
Testing and Low Vision Devices
Although much progress has been made recently in macular degeneration treatment research, complete recovery of vision lost to AMD is unlikely. Your eye doctor may ask you to check your vision regularly with an Amsler grid – a small chart of thin black lines arranged in a grid pattern. AMD causes lines on the grid to appear wavy, distorted or broken. Viewing the Amsler grid separately with each eye helps you monitor your vision loss.
If you have already suffered vision loss from AMD, low vision devices including high magnification reading glasses and hand-held telescopes may help you achieve better vision than regular prescription eyewear.