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.
The Two Forms of AMD
Macular degeneration can be classified as either dry or wet. Wet AMD is the growth of new blood vessels in the macula and usually leads to more serious vison loss.
Dry AMD is more common – about 85% to 90% of all cases of macular degeneration are the dry variety.
Dry macular degeneration. In the dry type of macular degeneration, the deterioration of the retina is associated with the formation of small yellow deposits, known as drusen, under the macula. This phenomenon leads to a thinning and drying out of the macula, causing the macula to lose its function. The amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen.
Dry age-related macular degeneration does not involve any leakage of blood or serum but loss of vision may still occur. Patients with the dry form may have good central vision (20/40 or better) but substantial functional limitations, including fluctuating vision, difficulty reading because of their limited area of central vision, limited vision at night or under conditions of reduced illumination.
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.
In the wet type of macular degeneration, abnormal blood vessels (known as choroidal neovascularization or CNV) grow under the retina and macula. These new blood vessels may then bleed and leak fluid, causing the macula to bulge or lift up from its normally flat position, thus distorting or destroying central vision. Under these circumstances, vision loss may be rapid and severe.
Macular Degeneration Signs and Symptoms
Age-related Macular Degeneration is often detected in an eye exam, before the symptoms become noticeable. In early AMD, tiny drusen or waste deposits can be seen on the surface of the retina. The macula itself sometimes shows a change in its color (pigment). In many people, the disease does not progress beyond this condition.
If the disease has progressed further than this initial stage, symptoms can include blurred or fuzzy vision; the illusion that straight lines, such as the edge of a door or sentences on a page, are wavy; the illusion that some objects are smaller than they really are; and the appearance of a gray, dark or empty area in the center of the visual field. Sometimes color vision is noticeably paler than usual.
An eye doctor 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 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 check your vision 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.
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.