Age-related macular degeneration (AMD) is an eye disease that may get worse over time. It’s the leading cause of severe, permanent vision loss in people over age 60. It happens when the small central portion of your retina, called the macula, wears down. The retina is the light-sensing nerve tissue at the back of your eye. Because the disease happens as you get older, it’s often called age-related macular degeneration. It usually doesn’t cause blindness but might cause severe vision problems. Another form of macular degeneration, called Stargardt disease or juvenile macular degeneration, affects children and young adults.
This eye disease occurs when there are changes to the macula, a small portion of the retina that is located on the inside back layer of the eye. AMD is a loss of central vision that can occur in two forms: "dry" (atrophic) and "wet" (exudative).
There are three stages of Age-related Macular Degeneration (AMD).
· Early AMD – Most people do not experience vision loss in the early stage of AMD, which is why regular eye exams are important, particularly if you have more than one risk factor. Early AMD is diagnosed by the presence of medium-sized drusen (yellow deposits beneath the retina).
· Intermediate AMD – At this stage, there may be some vision loss, but there still may not be noticeable symptoms. A comprehensive eye exam with specific tests will look for larger drusen and/or pigment changes in the retina.
· Late AMD – At this stage, vision loss has become noticeable.
TYPES OF AGE RELATED MACULAR DEGENRATION
There are two main types of age-related macular degeneration:
The dry form is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. The less common wet AMD usually leads to more serious vision loss.
· Dry AMD. Dry macular degeneration is an early stage of the disease. It appears to be caused by aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes.
Dry AMD is diagnosed when yellowish spots known as drusen begin to accumulate in and around the macula. It is believed these spots are deposits or debris from deteriorating tissue. Gradual central vision loss may occur with dry macular degeneration; but usually the visual impairment is not as severe as that caused by wet AMD. However, visual impairment from dry AMD can continue to progress year after year, eventually leading to significant vision loss.
Though there is not yet an effective medical treatment for dry AMD, nutritional studies have shown that dietary supplements containing antioxidant vitamins and lutein and zeaxanthin may reduce the risk of dry AMD progressing to the more severe wet stage of the disease. Currently, it appears the best way to protect your eyes from developing early (dry) macular degeneration is to eat a healthy diet, exercise and wear sunglasses that protect your eyes from the sun's harmful UV rays and high-energy visible (HEV) radiation.
· Wet AMD. In wet macular degeneration, abnormal blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells (photoreceptors) in the macula and creates a central blind spot (scotoma) in the affected person’s visual field.
Choroidal neovascularization (CNV), the underlying process causing wet AMD and abnormal blood vessel growth, is the body's misguided way of attempting to create a new network of blood vessels to supply more nutrients and oxygen to the eye's retina. Instead, the process creates scarring, leading to sometimes severe central vision loss.
In its early stages, the following signs of macular degeneration can go unnoticed.
· Gradual loss of ability to see objects clearly.
· Shape of objects appears distorted.
· Straight lines look wavy or crooked.
· Loss of clear color vision.
· A dark or empty area in the center of vision.
Central vision that is lost to macular degeneration cannot be restored. However, low-vision devices, such as telescopic and microscopic lenses, can maximize existing vision.
Aging is a primary risk factor for AMD. Each decade of life after age 40 significantly increases one’s risk for the disease. This is one reason why having routine eye exams after age 40 is so important.
Other risk factors for age-related macular degeneration include:
· Heredity. As stated above, recent studies have found that specific variants of different genes are present in most people who have macular degeneration.
· Smoking. Smoking is a major risk factor for AMD. Research has shown that, in some populations, smoking was associated with about 25 percent of AMD cases causing severe vision loss. Another study found that people who live with a smoker have twice the risk of developing AMD.
· Obesity. Researchers have found that people with dry AMD who were obese had more than double the risk of developing advanced macular degeneration, compared with people of normal body weight.
· Inactivity. People with dry AMD who perform vigorous activity at least three times weekly reduced their risk of developing advanced AMD, compared with people with dry AMD who were sedentary.
· High blood pressure. A European study found that high blood pressure may be associated with development of macular degeneration.
Also, certain medications — such as anti-psychotic drugs and medications used to treat malaria (chloroquine) — may increase your risk for AMD.
TREATMENT OF AMD
"dry" macular degeneration, the tissue of the macula gradually
becomes thin and stops working properly. There is no cure for dry AMD, and any
loss in central vision cannot be restored.
However, researchers and doctors believe there is a link between nutrition and the progression of dry AMD. Making dietary changes and taking nutritional supplements can slow vision loss.
Less common, "wet" macular degeneration occurs when fluids leak from newly formed blood vessels under the macula. This leakage blurs central vision. Vision loss can be rapid and severe.
If detected early, wet AMD can be treated with intraocular injections of anti-VEGF medications.
Researchers have linked eye-friendly nutrients such as lutein and zeaxanthin, vitamin C, vitamin E and zinc to reducing the risk of certain eye diseases, including macular degeneration. For more information on the importance of good nutrition and eye health, please see the diet and nutrition section.