Macular degeneration is a term that includes a variety of eye diseases that affect your central vision. Age-related macular degeneration (AMD) is the most common form of macular degeneration. AMD is a premature aging of the cells in the area of retina responsible for detailed central vision. This area of the eye is called the macula. Age-related macular degeneration is the leading cause of legal blindness in people older than 55 years in the United States. The disease affects more than 10 million Americans, including 23% of Americans older than 90 years. Because overall life expectancy continues to increase, age-related macular degeneration has become a major public health problem.
There are 2 types of age-related macular degeneration.
“Dry” Macular Degeneration: Multiple, small, yellowish deposits develop underneath the central retina called drusen. Drusen are the main feature of dry macular degeneration. As drusen accumulate underneath the central retina in an area called the macula, the macula can become thin and the retinal cells begin to function poorly.
Many people with drusen have excellent vision and no symptoms at all. However, some develop mild to moderate vision loss if the drusen worsen and the retinal cells are significantly affected. When visual loss develops, this generally happens slowly over a period of years.
Most people with age related macular degeneration begin with the “dry” form of the disease. The dry form accounts for 90% of all cases of age-related macular degeneration. Dry AMD progresses slowly, and most patients maintain useful vision throughout life.
“Wet” macular degeneration: Choroidal neovascularization – CNV : Newly-formed abnormal blood vessels, called choroidal neovascularization, are the hallmark of wet macular degeneration. These abnormal blood vessels grow between the retina and the deeper layers of the eye wall,in the area of the macula.
These blood vessels will spontaneously leak fluid, bleed, and scar the retina. This process causes distortion and damage of the central retina. Vision distortion, visual blur, and/or a blind spot can develop suddenly with the development of choroidal neovascularization.
Most patients who develop wet macular degeneration have some degree of pre-existing dry macular degeneration. Although wet macular degeneration affects only 10% of people who have age-related macular degeneration, it accounts for the majority of people who have significant visual loss. More than 200,000 new cases of wet age-related macular degeneration occur each year in the US.
Initial tests include measurement of the sharpness of your vision and a retina exam. If your doctor finds signs of macular degeneration, pictures of the retina can be taken to assess the extent of the disease and to detect “wet” macular degeneration. Tests may include these:
Optical Coherence Topography (OCT): A special scanning retinal camera that takes images of the retina and is able to visual the various layers of the retina. Often an OCT can determine that the macular degeneration is either “dry” or “wet.” Subsequent pictures can be taken to follow the disease progress and also to follow patients through their treatments protocols to determine if further treatment is needed.
Fluorescein angiography: A special dye is injected into your arm. Then photographs of your retina are taken as the dye passes through the retina. The test is used to determine if “wet” macular degeneration exists. It also locates and measures the extent of the disease to determine the best treatment option.
Indocyanine green angiography: This test uses infrared wavelengths to view your retina. ICG angiography may help further characterize “wet” macular degeneration, and can be helpful in cases where the exact origin of the abnormal blood vessel cannot be determined by fluorescein angiography alone (i.e. occult neovascular membranes).
As there is no cure for aging, there is no cure for macular degeneration. However, proven treatments are available which can slow or halt the progression of the disease and sometimes improve vision in many patients.
1. Vitamins: The Age Related Eye Disease Study (AREDS) showed that antioxidants and vitamins reduce the risk of vision loss in patients with moderate to advanced “dry”age-related macular degeneration. The nutrients evaluated by the AREDS are contained in several different formulations, which are now available over the counter. However, these formulations are not without risk (i.e. increased chance of lung cancer in smokers). A consultation with your eye doctor is recommended to determine if vitamins may benefit you. More information regarding the AREDS vitamin formulation is available on the website of the National Eye Institute: www.nei.nih.gov/amd/
2. Intravitreal Injections: Several medicines have been proven effective for treatment of “wet” macular degeneration by injection directly into the eye. Drug therapy is currently the preferred first-line treatment for “wet” age related macular degeneration.
3. Laser treatment: Laser surgery was the first proven treatment for “wet” macular degeneration. Patients with neovascularization outside the center of vision may be treated with a “hot” laser to directly destroy the abnormal blood vessels. Only a small percentage of patients with “wet” macular degeneration are good candidates for this treatment as newer treatment modalities have proven to be more effective for this disease process.
The dry form accounts for ninety percent of all cases of Age-related Macular Degeneration ( AMD ). Dry AMD progresses slowly, and patients keep most of their vision throughout life. A certain percentage of patients with dry AMD can progress to the wet AMD form of the disease, therefore it is very important that the patient is seen by the ophthalmologist semi-annually or if any sudden changes in vision occur.
The wet form comprises ten percent of all cases of AMD. Wet AMD is a leading cause of irreversible legal blindness in patients older than 55 in the United States. Approximately 60% of those who lose vision in one eye lose vision in the other eye as well. When both eyes have wet AMD, quality of life can be severely affected. However, people rarely lose all of their vision from macular degeneration as the peripheral or side vision stays intact. Despite poor central vision, most people with macular degeneration are able to care for themselves and perform most of the activities of daily living.
Treatments for macular degeneration are constantly evolving. Research and a better understanding of the disease process have led to new treatments and better visual outcomes for patients with the “wet” form of the disease.