What is age-related macular degeneration?
Age-related macular degeneration (AMD) is a retinal degenerative
disease that causes a progressive loss of central vision.
AMD is the most common cause of vision loss in individuals over 55.
An estimated 10 million people in the U.S. either have AMD or are at
substantial risk of developing it.
What are the symptoms?
The macula is a small region in the center of the retina, which enables
a person to see fine detail. Light sensing cells in the macula, known
as photoreceptors, convert light from the visual field into electrical
impulses and then transfer the impulses to the brain via the optic
Central vision loss from AMD occurs when photoreceptor cells in the
People with AMD may first notice a blurring of central vision,
especially during tasks such as reading or sewing.
Also, straight lines may appear distorted or warped. As the disease
progresses, blind spots may form within the central visual field. In
most cases, if one eye has AMD, the other eye will develop the disease.
The extent of central vision loss varies depending on the type of AMD
and dry or wet.
What is dry AMD?
Dry AMD accounts for about 90 percent of all cases, and normally
affects vision less than wet AMD. Dry AMD is sometimes called atrophic,
nonexudative, or drusenoid macular degeneration. A characteristic of
dry AMD is the accumulation of tiny protein and fat-containing
“drusen” deposits in a thin layer of cells beneath
photoreceptors in the retina called Bruch's membrane.
The origin of drusen is unknown, but they may be from waste products of
various cells and tissues of the retina.
Drusen may interfere with the health of the macula, causing progressive
degeneration of the photoreceptor cells. Drusen deposits can, however,
be present without vision loss.
Reduction in central vision from dry AMD occurs gradually over many
years. Vision may even remain stable between eye examinations. People
with dry AMD do not usually experience a total loss of central vision
but tasks that require finely focused vision may become more difficult.
Research suggests that medium- and large-sized drusen present a greater
risk for the progression of dry AMD to wet AMD.
Wet AMD causes more severe vision loss. Although no standard therapies
currently exist to treat dry AMD, several clinical research trials are
evaluating methods, including laser treatments, to reduce their size.
What is wet AMD?
Wet AMD accounts for about 10 percent of all cases of macular
degeneration. Wet AMD is also called choroidal neovascularization
(CNV), subretinal neovascularization, or exudative or disciform
degeneration. In wet AMD, abnormal blood vessels grow beneath the
These vessels leak blood and fluid into the macula that damage
Wet AMD often progresses rapidly and can cause substantial loss of
What treatments are available for wet AMD?
Excellent progress is being made in understanding, predicting, and
treating wet AMD. Scientists have discovered new causes of the disorder
— including genetic and environmental factors — as
possible risk indicators.
Numerous pharmaceutical companies are developing wet AMD treatments.
Researchers are also studying cell transplantation to preserve and/or
In June 2006, the FDA approved a drug called Lucentis for the treatment
of wet AMD.
Results from a large, two-year study showed that Lucentis halted vision
loss in more than 90 percent of individuals with the wet form of
age-related macular degeneration (AMD).
In addition, Lucentis restored vision in 33 percent of those study
FFB has funded dozens of research projects to better understand the
mechanisms that lead to vision-robbing blood vessel growth in wet AMD,
giving companies like Genentech, maker of Lucentis, clear targets for
the development of AMD treatments.
Numerous clinical research trials are being conducted to evaluate other
promising treatments for wet AMD.
FFB recommends that patients always discuss study participation with a
health care provider before enrolling.
How does nutrition affect AMD?
The Age-Related Eye Disease Study (AREDS), conducted by the National
Eye Institute, revealed that a dietary supplement containing a
combination of vitamins and minerals could help reduce the risk of
advanced wet AMD and vision loss in people who are at greatest risk.
The AREDS study found that high levels of antioxidants and zinc can
reduce the risk of developing advanced AMD by about 25 percent. The
specific daily amounts of antioxidants and zinc used by the study
researchers were 500 milligrams of vitamin C; 400 International Units
of vitamin E; 15 milligrams of beta-carotene (often labeled as
equivalent to 25,000 International Units of vitamin A); 80 milligrams
of zinc as zinc oxide; and two milligrams of copper as cupric oxide.
Copper was added to the AREDS formulations containing zinc to prevent
copper deficiency anemia, a condition associated with high levels of
zinc intake. Please visit www.nei.nih.gov/amd for more information
about the AREDS recommendations.
AMD may also be related to dietary fat, according to scientists
studying people with early- and intermediate-stage disease.
They found that study subjects who reported eating lower amounts of
vegetable and animal fat were less likely to develop advanced AMD.
However, fish and nuts can slow the progress of AMD. Studies have
revealed that eating fish — which is high in healthful
fatty acids — has a protective effect. Though nuts are also
protective, researchers did not determine which nuts, or how much of
them, should be consumed.
Carotenoids are also possible protectors against AMD. Researchers found
that the more dietary lutein and zeaxanthin — two carotenoids
found in green and colorful vegetables — you eat, the lower
likelihood you have of developing advanced AMD. These carotenoids are
highly concentrated in the macula and may be protecting it from damage.
What are the risk factors?
The exact causes of both dry and wet AMD are not completely understood.
However, genetics, diet, cigarette smoking, bright sunlight,
cardiovascular disease, and hypertension are considered to be possible
risk factors for AMD.
Is AMD an inherited disease?
Researchers are discovering that genetics appears to be a major factor
in more than half of the cases of AMD. In March 2005, three independent
research groups — including one funded by FFB discovered
a gene called Complement Factor H (CFH) that appears to be linked to at
least 50 percent of all cases of AMD.
Prior to this landmark discovery, FFB-funded researchers discovered
other genes that appeared to be linked to AMD, though these genes were
implicated in a smaller number of cases than CFH.
What is the Amsler grid?
Along with regular examinations by an eye doctor, people can evaluate
their eyesight for possible symptoms of AMD using a simple home testing
device known as the Amsler grid. The Amsler grid, consisting of
parallel and perpendicular lines, looks much like a sheet of graph
paper. By focusing on a marked spot in the middle of the grid, it is
quite easy to detect blurred or distorted vision. While the Amsler Grid
is not a substitute for an expert medical diagnosis, it does allow
people to check their eyesight regularly for possible symptoms of AMD.
To receive a free Amsler Grid, please call the Foundation Fighting
What low-vision aids are available?
As central vision declines, people with AMD may benefit from low-vision
aids like magnifying glasses and special lenses, screens that enlarge
small print, text-to-speech and speech-to-text computer software
programs, and any number of other specialized technologies. Low-vision
experts can also help individuals adapt daily living skills.
Low-vision specialists are available through ophthalmology centers and