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Age-related Macular Degeneration (AMD)
Macular degeneration is the
leading cause of irreversible severe visual loss in Caucasians age 50 or older
in the United States. It has been estimated that this 2.2% of those older than
age 65 have worse than 20/200 vision (legally blind) due to this condition. This
page discusses the condition known as age-related macular degeneration, or AMD.
Read this important information
before proceeding further:
These sections are not intended to replace the professional examination and
diagnosis by a physician, and they are presented here purely for informational purposes.
All possible diagnoses and treatment options are not covered, and the information
discussed should not be taken as a recommendation to self-diagnose and self-treat a
condition. A misdiagnosed or improperly treated eye condition can result in a permanent
loss of vision, or a permanent loss of function of the eye or visual system. In the case
of any eye problem, seek medical attention promptly. This can include emergency room
treatment, as well as treatment by a medical physician or eyecare provider.
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Topics Include:
For eye anatomy explanations, go to
ANATOMY
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Note: There are other similar conditions such as ocular histoplasmosis,
myopic macular degeneration, and macular degeneration related to angioid streaks
and trauma which will not be separately discussed.
 The retina is thin lining of nerve cells which lines the inside of
the eye. It receives and processes images, and sends these images to the brain
via the optic nerve. The macula is a small, but very important part of the
retina capable of perceiving the sharpest of images. It is here that our central
vision (what we look directly at), our reading vision, and our color vision are
received. Without the macula, we would be legally blind, with only peripheral
vision (side vision) to guide us. An enlarged view of the macula is shown
here. The optic nerve is the yellow circle with blood vessels leaving it. The
nerve head is about 1.5 mm in diameter. The vessels are retinal arteries and
veins which supply the inner layers of the retina. The center of the macula is
the small red and yellow dot, called the "fovea". This is our point of
visual fixation (with what we look directly at).
The condition known as "age-related macular degeneration" leads to
deterioration of the macula, and possible loss of vision. Risk factors for this
condition include:
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Advancing age, over 50 years of age, and especially over 65
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Caucasian race
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A history of visual loss related to macular degeneration in the other eye
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Certain types of retinal deposits, called drusen
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A family history of macular degeneration
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Tobacco smoking (especially for the more severe form of
macular degeneration)
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Arteriosclerosis and increased cholesterol, possibly hypertension
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A diet deficient in anti-oxidant vitamins and minerals
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A recent study
showed that sensitivity to glare and poor
tanning ability were markers of increased macular degeneration risk.
Interestingly, the study could not demonstrate that sun exposure itself was
a risk factor.
Age-related macular degeneration is broadly grouped into two categories: a
"dry" form, and a "wet" form. The next section discusses
these differences.
This form of macular degeneration consists of a slow deterioration of the
retina. Deposits form under the retina called "drusen". Drusen may
block nutrition from reaching the retina from a highly vascular layer under the
retina called the "choroid". The choroid nourishes the outer layers of
the retina, while the retinal blood circulation supplies the inner layers. Over
time, the retina atrophies, or degenerates, over these area of drusen, and a
spotty loss of vision occurs. If more and more of these atrophic areas form and
merge together, the macula can take on a moth-eaten appearance, with progressive
loss of vision. This usually occurs over a period of many years.
There is no known treatment for this form of macular degeneration.
Theoretically, it may help to reduce any risk factors one may have (listed
above), but it has not been proven that this will help prevent visual loss. If a
person with macular degeneration has a well balanced diet, nutritional
supplements may not be necessary. If not, a multi-vitamin is usually recommended
(see the section on nutrition below).
This is a more severe and rapidly progressive form of macular degeneration.
In some cases, the "dry" form of macular degeneration will lead to the
"wet" form, but in other cases this form occurs without warning.
Between the vascular choroid layer under the retina and the retina itself is a
dividing membrane called the "retinal pigment epithelium". If a break
occurs in the retinal pigment epithelium, it becomes possible that an abnormal
blood vessel could grow from the choroid to directly underneath the retina in
the macula. Such a break could occur in an area of drusen, especially drusen
that have pigmentation and appear diffuse or fuzzy. When a new blood vessel
grows under the retina, it is termed "subretinal neovascularization".
Subretinal neovascularization in the macula can be a surgical emergency. If such
a blood vessel is treatable, it should be treated as soon as possible after the
diagnosis is made. Symptoms of this condition, otherwise known as
"wet" macular degeneration, include:
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A change in vision, usually a sudden blurring in one eye.
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Distortion of vision, where straight lines appear crooked
or bent in the affected
eye.
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A blind spot appearing in the vision of the affected eye, where things
seem to disappear when looked at. Sometimes, a blind spot will occur near to
what is being looked at instead.
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A change in the size appearance of things, with objects appearing to be
smaller or larger than with the other eye.
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For a detailed account of one person's experience with subretinal
neovascularization, and for further discussion on this disease, visit Macular Degeneration and Subretinal Neovascularization.
Note: other conditions such as ocular histoplasmosis, myopic macular
degeneration, and macular degeneration related to angioid streaks and trauma can
lead to subretinal neovascularization.
When an ophthalmologist examines the retina, the blood vessel growing under
the retina can often be seen. Other times, there may be hemorrhage in or under
the retina, obscuring the view of the vessel. Swelling of the retina can often
be observed as well.
Additional tests, such as OCT (Optical Coherence Tomography), fundus
photography, and fluorescein angiography, are
usually done as immediately as possible to better determine where the new,
abnormal blood vessel is and if it can be treated.
A fluorescein angiogram is a
test done in the office where a pigmented dye is photographed as it passes
through the retinal blood vessels. For this test, the eyes are dilated, and
initial color photographs are taken of the retina by the photographer. Then, the
fluorescein dye is injected into an arm vein by a physician. This is similar to
having blood drawn. Once the dye is in, the needle is removed, and the
photographs are taken. The dye reaches the eye in a matter of seconds. Abnormal
vessels under the retina and areas of leakage from vessels can be clearly
identified using this technique, and it is often done to verify the disorder and
plan treatment.
Optical Coherence Tomography is a non-invasive test of the retina where
reflections from scanning light beam can be reconstructed using a computer to
give detailed cross-sectional views of retinal anatomy. This is also used
for diagnosis and to monitor treatment success.
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The diagnosis of macular degeneration depends on several factors:
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A careful history taken by the examiner as to possible risk factors and
symptoms of macular degeneration.
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A careful retinal examination to look for evidence of macular
degeneration, or for any precursors of it (drusen).
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Additional tests such as fluorescein angiography,
fundus photography, OCT testing, and Amsler grid testing
(discussed below).
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Scheduling appropriate follow-up visits, and self-monitoring of vision by
the patient.
The "Amsler grid" is a small graph-like chart with a central dot.
It is useful for testing for distortion of vision. To do the test, the grid is
held at normal reading distance (16 inches) with glasses on if needed. With one
eye covered, the central dot is looked at. Any missing lines, distorted lines,
or other abnormality on the chart is then noted by the patient. The other eye is
then tested. This is a way for patients with risk factors for macular
degeneration, or with previously treated macular degeneration to monitor their
vision for development of "wet" macular degeneration (subretinal
neovascularization).
Treatment of "dry" macular degeneration
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Unfortunately, there is currently
no successful treatment for this form of the disease.
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Vision should be monitored with the Amsler grid for early detection of the
"wet" form of macular degeneration.
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Follow-up appointments should be kept as directed
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Nutritional supplements are often
recommended to help slow or prevent further vision loss.
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Discontinuation of tobacco use in encouraged.
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Treatment of "wet" macular degeneration
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Once diagnosed with "wet" macular degeneration, it is implied
that subretinal neovascularization is present. If this finding meets certain
criteria on the fluorescein angiogram, laser treatment may be able to
eliminate the abnormal blood vessel.
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If treated with laser, a blind spot will result in the vision.
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The purpose of the laser treatment is to prevent severe loss of vision.
Sometimes some loss of vision may occur with the laser treatment in order to
prevent further loss of vision.
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After successful laser treatment, the situation needs to be closely
monitored for signs of recurrence. This includes follow-up examinations and
possibly more fluorescein angiograms.
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The Amsler grid should be closely monitored by the patient in both the
affected and unaffected eye for a change in vision.
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Nutritional supplements can be considered.
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Intravitreal Drug Injections
The use of drugs injected directly into the eye
has become increasingly used for virtually all forms of wet macular
degeneration as well as many other retinal vascular disorders, including
vein occlusions and diabetic retinopathy. The identification of the
naturally occurring chemical (VEGF - Vascular Endothelial Growth Factor)
that leads to the development of abnormal vessels in macular degeneration
was a major breakthrough. Various drugs that block VEGF have been
developed, and these are known as "anti-VEGF" drugs.
As of 2011, there are several injected drug therapies that are used to treat
exudative AMD. Two therapies are approved by the US FDA for this indication:
pegaptanib sodium (Macugen®) and ranibizumab (Lucentis®). Intravitreal
bevacizumab (Avastin®) and triamcinolone acetonide (and other injectable
corticosteroids) are also widely used off-label for the treatment of
exudative AMD.
There has been great excitement with the development of these drug
treatments, as many patients not only show a decrease in vision loss, many
have improvement in vision. While injection of medication directly
into the eye does not sound particularly appealing, it is a safe and almost
painless procedure performed countless times by retinal specialists.
Many patients require multiple injections to control the disease, and slow
release medications are under development.
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Photodynamic Therapy
Laser treatment of macular
degeneration, especially that involving the sharpest area of the vision, has
been frustrating, because the laser treatment itself is damaging.
Furthermore, the condition often recurs after treatment. An alternative treatment for the "wet" form of macular degeneration has been
FDA approved, called Photodynamic Therapy. The "wet" form of macular
degeneration consists of abnormal blood vessels growing under the retina,
ultimately leading to distortion in the vision, hemorrhaging, and scarring. If
these blood vessels (subretinal neovascular membranes) grow under the most
sensitive part of the macula (the fovea), laser treatment of the vessels would
also destroy the fovea itself, leading to a loss of central vision.
Photodynamic Therapy does not damage the retina overlying abnormal vessels,
and offers treatment for an otherwise largely untreatable condition.
With Photodynamic Therapy, the drug Visudyne (verteporphin) is first
injected into an arm vein. After a short waiting period, a light of a specific
wavelength is shined upon the part of the retina that contains the abnormal
blood vessels. This light, which has the brightness of a flashlight and is
non-damaging, activates the injected drug to destroy the abnormal blood
vessels, where it accumulates. Thus, the subretinal neovascular membrane is
destroyed while sparing the overlying retina. The whole procedure takes about
20 minutes, and is painless.
The 1 year results of a study
looking at the effectiveness and safety of the procedure are favorable. The
group of patients treated by Photodynamic Therapy had a 34% better
likelihood of retaining vision than an untreated group of patients with the
same disorder. In some cases, the vision improved. The procedure did need to
be repeated in many patients over a 1 year period to achieve the desired
effects. However, there was very little in the way of adverse side effects,
with the most common being sensitivity to light for 1 to 2 days.
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Other Surgical Options for macular degeneration include manual
removal of abnormal neovascular membranes from under the retina in the
operating room. Alternatively, the retina itself can be trans-located away
from the abnormal membrane and laid back down on a more healthy area of the
eye internally. These techniques are undergoing evaluation in carefully
selected patients but have not been met with widespread success.
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It has been found that people with diets deficient in certain
"anti-oxidant" vitamins and minerals may be at increased risk for
age-related macular degeneration. However, a well-balanced diet with the
possible supplementation of a multivitamin will usually prevent such a
deficiency. Should extra doses of these vitamins be taken by those at
risk for macular degeneration?
The retina is at risk for light induced damage termed "oxidative"
damage. This damage could possibly lead to macular degeneration. The retina has
relatively high concentrations of anti-oxidant vitamins and minerals. These
substances help to prevent this oxidative damage. These vitamins and trace
minerals include:
Different studies have been done to try to determine if there is any
relationship between blood level and dietary intake of these substances with
age-related macular degeneration (AMD). Some earlier studies were fairly
inconclusive as to the benefits of dietary supplements on reducing vision loss
from macular degeneration:
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One study showed that high blood levels of Vitamin E were
protective for AMD. Similarly, a combination of high blood levels of Vitamin
C, Vitamin E, and b-carotene was also protective. However, the study was
unable to demonstrate that the consumption of the vitamins themselves helped
to preserve vision!
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Another study found that high blood levels of a combination of
carotenoids, Vitamin C, Vitamin E, and selenium had a reduction of risk for
the "wet" form of AMD. However, the authors of the study stated
that it would be premature to translate these findings into nutritional
recommendations.
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A high dietary intake of zinc was found to be weakly protective in
some early stages of AMD in another study , while the intake of carotenoids,
Vitamin C, Vitamin E, and of nutritional supplements were found not to be
significantly protective.
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High intake of certain foods containing carotenoids not normally found in
vitamin supplements was found to reduce the risk of the "wet" form
of AMD. These foods included spinach, collard greens, kale, mustard greens,
and turnip greens. Intake of supplemental Vitamin A, C, and E were not found
to improve the risk of AMD.
AREDS
The landmark AREDS (Age-Related
Disease Study Research Group) results indicate a definite reduction in risk of vision loss from macular
degeneration with dietary supplementation of antioxidants and zinc. This
protection was only evident in those already at moderate or high risk for the disease at
baseline. Those studied with minimal or no evidence of macular degeneration at
baseline had such a low rate of vision loss from macular degeneration that no
treatment effect could be determined. The antioxidants that were found to be
effective were:
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Antioxidants (500mg vitamin C, 400 IU vitamin E, 15 mg beta carotene)
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80 mg zinc, as zinc oxide, and 2mg copper, as cupric oxide
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Both antioxidants plus zinc together
The antioxidants alone reduced the risk of advanced macular degeneration by 10%,
the zinc alone by 14%, and the combination of zinc and antioxidants reduced risk
by 21%. For more information on this study, and potential risks of these
vitamin supplements, go to
AREDS Results: High-Dose
Supplementation with Antioxidants and Zinc Found Beneficial for those at High
Risk for Age-Related Macular Degeneration.
Please note
that many vitamins, especially Vitamins A and E can be stored by the body, and
dangerous side effects can occur when high dosages of these are consumed. In
many people, supplementation with high amounts of zinc may lead to anemia. One study was terminated because high levels of
B-carotene consumption were found to increase the risk of lung cancer in
male and female smokers. Thus, vitamin supplementation is not without risk, and
one's general physician should be consulted prior to taking vitamin supplements.
Finally, the body regulates the absorption of many vitamins and minerals. If the
body does not need a particular one of these, it may leave the body undigested.
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