Wet and Dry Forms of Macular Degenertion
Macular degeneration is diagnosed
as either dry (non-neovascular) or wet (neovascular). Neovascularrefers
to growth of new blood vessels in an area, such as the macula, where they are
not supposed to be.
The dry form is more common than
the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry
AMD. The wet form of the disease usually leads to more serious vision loss.
Dry macular degeneration
(non-neovascular). 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 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 is not nearly as severe as wet
AMD symptoms. However, dry AMD through a period of years slowly can progress to
late-stage geographic atrophy (GA) — gradual degradation of retinal
cells that also can cause severe vision
loss.
Wet
macular degeneration (neovascular). In about 10 percent of
cases, dry AMD progresses to the more advanced and damaging form of the eye disease.
With wet macular degeneration, new blood vessels grow beneath the retina and
leak blood and fluid. This leakage causes permanent damage to light-sensitive
retinal cells, which die off and create blind spots in central vision.
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.
Wet macular degeneration falls into
two categories:
- Occult. New
blood vessel growth beneath the retina is not as pronounced, and leakage
is less evident in the occult CNV form of wet macular degeneration, which
typically produces less severe vision loss.
- Classic. When
blood vessel growth and scarring have very clear, delineated outlines
observed beneath the retina, this type of wet AMD is known as classic CNV,
usually producing more severe vision loss.
What Causes Macular Degeneration ?
Though macular degeneration is
associated with aging, research suggests there also is a genetic component to
the disease. Duke University and other researchers have noted a strong
association between development of AMD and presence of a variant of a gene
known as complement factor H (CFH). This gene deficiency is associated with
almost half of all potentially blinding cases of macular degeneration.
Columbia University Medical Center
and other investigators found that variants of another gene, complement factor
B, may be involved in development of AMD.
Specific variants of one or both of
these genes, which play a role in the body's immune responses, have been found
in 74 percent of AMD patients who were studied. Other complement factors also
may be associated with an increased risk of macular degeneration.
Other research has shown that
oxygen-deprived cells in the retina produce a type of protein called vascular
endothelial growth factor (VEGF), which triggers the growth of new blood
vessels in the retina.
The normal function of VEGF is to
create new blood vessels during embryonic development, after an injury or to
bypass blocked blood vessels. But too much VEGF in the eye causes the
development of unwanted blood vessels in the retina that easily break open and
bleed, damaging the macula and surrounding retina.
How Macular Degeneration Is Treated
There is as yet no outright cure
for age-related macular degeneration, but some treatments may delay its
progression or even improve vision.
Treatments for macular degeneration
depend on whether the disease is in its early-stage, dry form or in the more
advanced, wet form that can lead to serious vision loss. No FDA-approved
treatments exist yet for dry macular degeneration, although nutritional
intervention may help prevent its progression to the wet form.
For wet AMD, treatments aimed at
stopping abnormal blood vessel growth include FDA-approved drugs called
Lucentis, Eylea, Macugen and Visudyne used with Photodynamic Therapy or PDT.
Lucentis has been shown to improve vision in a significant number of people
with macular degeneration.
Nutrition and Macular Degeneration
There is as yet no outright cure
for age-related macular degeneration, but some treatments may delay its
progression or even improve vision.
Treatments for macular degeneration
depend on whether the disease is in its early-stage, dry form or in the more
advanced, wet form that can lead to serious vision loss. No FDA-approved
treatments exist yet for dry macular degeneration, although nutritional
intervention may help prevent its progression to the wet form.
For wet AMD, treatments aimed at
stopping abnormal blood vessel growth include FDA-approved drugs called
Lucentis, Eylea, Macugen and Visudyne used with Photodynamic Therapy or PDT.
Lucentis has been shown to improve vision in a significant number of people
with macular degeneration.
Age-Related Macular Degeneration
Age-related macular degeneration —
also called macular degeneration, AMD or ARMD — is deterioration of the macula,
which is the small central area of the retina of the eye that controls visual acuity.
The health of the macula determines
our ability to read, recognize faces, drive, watch television, use a computer,
and perform any other visual task that requires us to see fine detail.
Macular degeneration is the leading
cause of vision loss among older Americans, and due to the aging of the U.S.
population, the number of people affected by AMD is expected to increase
significantly in the years ahead.
According to a recent study by
researchers at the University of Wisconsin School of Medicine and Public Health
and the U.S. Centers for Disease Control and Prevention (CDC), approximately
6.5 percent of Americans age 40 and older have some degree of macular
degeneration. Other research suggests there were 9.1 million cases of early AMD
in the U.S. in 2010 and this number is expected to increase to 17.8 million by
the year 2050.
AMD is most common among the older
white population, affecting more than 14 percent of white Americans age 80 and
older. Among Americans age 50 and older, advanced macular degeneration affects
2.1 percent of this group overall, with whites being affected more frequently
than blacks, non-white Hispanics and other ethnic groups (2.5 percent vs. 0.9
percent).

Age- Related Macular Degeneration Symptoms and Signs
Age-related macular degeneration
usually produces a slow, painless loss of vision. In rare cases, however,
vision loss can be sudden. Early signs of vision loss from AMD include shadowy
areas in your central vision or unusually fuzzy or distorted vision.
Viewing a chart of black lines
arranged in a graph pattern (Amsler grid)
is one way to tell if you are having these vision problems. See how an Amsler
grid works by taking a macular degeneration
test.
Eye care
practitioners often detect early signs of macular
degeneration before symptoms occur. Usually this is accomplished through a
retinal exam. When macular degeneration is suspected, a brief test using an
Amsler grid that measures your central vision may be performed.
If your eye doctor detects some
defect in your central vision, such as distortion or blurriness, he or she may
order a fluorescein
angiography to examine the retinal blood
vessels surrounding the macula.
Who gets Age-Related Macular Degeneration?
Besides affecting older
populations, AMD occurs in whites and females in particular. The disease also
can result as a side effect of some drugs, and it seems to run in families.
New evidence strongly
suggests smoking is
high on the list of risk factors for macular degeneration. Other risk factors
for macular degeneration 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, but this theory has not been proven conclusively. High
levels of dietary fat also may be a risk factor for developing AMD.
Commonly named risk factors for
developing macular degeneration include:
- Aging. The
prevalence of AMD increases with age. In the United States, approximately
one in 14 people over the age of 40 has some degree of macular
degeneration. For those over 60, the rate is one in eight (12.5 percent);
and for seniors over age 80, one in three (33 percent) has AMD.
- Obesity
and inactivity. Overweight patients with
macular degeneration had more than double the risk of developing advanced
forms of macular degeneration compared with people of normal body weight,
according to one study reported in Archives
of Ophthalmology (June 2003). In the same
study, those who performed vigorous activity at least three times weekly
reduced their risk of developing advanced AMD, compared with inactive
patients.
- Heredity. As
stated above, recent studies have found that specific variants of
different genes are present in most people who have macular degeneration.
Studies of fraternal and identical twins may also demonstrate that
heredity is a factor in who develops AMD and how severe it becomes.
- High
blood pressure (hypertension). Investigative
Ophthalmology and Vision Science reported
the results of a European study demonstrating that high blood pressure may
be associated with development of macular degeneration.
- Smoking. Smoking
is a major AMD risk factor and was found in one British study to be
directly associated with about 25 percent of AMD cases causing severe
vision loss. The British
Journal of Ophthalmology in early 2006 also reported
study findings showing that people living with a smoker double their risk
of developing AMD.
- Lighter
eye color. Because macular
degeneration long has been thought to occur more often among Caucasian
populations, particularly in people with light skin color and eye color,
some researchers theorized that the extra pigment found in darker eyes was
a protective factor against development of the eye disease during sun
exposure. But no conclusive evidence as yet has linked excessive sun
exposure to development of AMD.
A small study reported in the British
Journal of Ophthalmology (January 2006) found no
connection between the eye disease and sun exposure. In fact, the same
study found no relation at all between lighter eye color, hair color and
AMD. That finding is contradicted by several earlier studies indicating
that lighter skin and eyes are associated with a greater prevalence of
AMD.
- Drug
side effects. Some cases of macular
degeneration can be induced from side effects of toxic drugs such as Aralen
(chloroquine, an anti-malarial drug) or phenothiazine. Phenothiazine is a
class of anti-psychotic drugs, including brand names of Thorazine
(chlorpromazine, which also is used to treat nausea, vomiting and
persistent hiccups), Mellaril (thioridazine), Prolixin (fluphenazine),
Trilafon (perphenazine) and Stelazine (trifluoperazine).