Before we look at what macular degeneration is, let’s quickly review some ocular
physiology and anatomy. In the beginning there was light, and this light was focused, or
“bent” when it passed through the cornea and lens of the eye. When this light enters the
eye, its focused beams fall on the inner back membrane of the eye, the retina, and located
in the center of the retina is the macula. The macula is responsible for our sharp, central
vision. In the macula, the nerve cells of the retina are composed mainly of cone cells
closely clustered together. Cone cells are highly sensitive to light and make detail vision
and the perception of colors possible. The macula is nearly one hundred times more
sensitive than the outlying regions of the inner eye. Since the central focus of light in the
eye is upon the macula we are provided with clear, focused, and “straight-ahead” vision.
This is why when we are interested in seeing fine details of something, be it a threading a
needle, driving on the road, reading a book, watching TV, or recognizing a face, we focus
our gaze directly at the object.
A common condition that occurs as one ages is a degeneration of the macula. This
condition is known as Age Related Macular Degeneration or ARMD. ARMD simply
describes a condition in which there has been a deterioration of the macula. An eye
affected by macular degeneration will not be able to perceive details or colors as well as
a healthy eye. Progressive deterioration of the macula can lead to loss of central sight.
However, it does not lead to complete blindness because the peripheral regions of the
retina remain unaffected. According to the American Academy of Ophthalmology,
"Macular degeneration is the most common cause of severe vision loss among people
over 65, and, as life expectancy increases, the disease is becoming an increasingly
important problem."
Macular degeneration causes a progressive loss of central sight, however, it does not cause
total blindness. Peripheral vision is unaffected so one will always be able to get about in
normal surroundings. Unfortunately, the cause of macular degeneration is unknown.
Although your ophthalmologist will be able to readily detect the disease during an eye
exam, he or she won't be able to cure it. The goal is to help the patient see better and
stabilize the condition. Although there is no “magic pill “ or treatment for macular
degeneration, research in this field is very active and promising, and depending upon
the form of macular degeneration, there are treatments that can help to control the
progression of the condition.
There are two forms of macular degeneration:
“Dry” Macular Degeneration:
The dry type of macular degeneration is the most common form of this condition (>90%).
It is also the most insidious, for there is no form of treatment that is known to stop its
progression, although vitamin supplements are often prescribed. In this slow developing
type of macular degeneration, the delicate tissues of the macula becomes thin, typically
due to aging, and ceases to function properly. There may be a slight dimming in the center
of the field of vision with this form of macular degeneration depending on its progression.
This form of macular degeneration usually starts with the appearance of spots on the retina.
These spots are called "drusen". Once the retinal tissues are affected by the dry type of
macular degeneration, there is little that can be done to stop its slow progression and
nothing has been found effective to restore sight lost to its effects.
“Wet” Macular Degeneration:
Though this form of macular degeneration is less common (<10%), it is typically more
damaging. The wet type of macular degeneration is caused by the growth of abnormal
blood vessels behind the macula (beneath the retina). The abnormal blood vessels tend to
hemorrhage or leak, with the result being the formation of scar tissue if left untreated. This
in turn creates a large, permanent blind spot in the center of the field of vision. In some
instances, the dry type of macular degeneration can turn into the wet type.
The wet form of macular degeneration can be somewhat controlled through laser treatments,
provided they are performed at an early stage of the condition. The laser treatment seals the
leaking blood vessels closed, halting the damage they can inflict upon the retina. These
laser treatments are effective preventing or slowing the progress of wet type macular
degeneration; however as with dry macular degeneration, no treatment has been discovered
to restore sight lost to this condition.
If this form of macular degeneration is not treated, it tends to progress at a steady pace. As
the condition progresses, it significantly reduces central sight.
Symptoms and Diagnosis
Macular degeneration develops differently in each person. Though
it is more common to develop in people over 60, depending upon
risk factors, it may develop much earlier. Because it will affect
different regions of the macula from person to person, the
symptoms tend to vary. In general, the following symptoms are
indicative of macular degeneration:
- The loss of the ability to see objects clearly.
- Vision that is noticeably distorted.
- Straight lines appear wavy.
- Objects may appear as the wrong shape or size.
- The loss of clear, correct colors.
- Blurry or a dark, empty area in the center of vision.
If you experience any of these symptoms in either one or both eyes, schedule an
appointment with your ophthalmologist for an examination immediately.
Risk Factors
Macular degeneration tends to have a higher incidence of occurrence when the following
risk factors are present:
- Age: Macular degeneration can occur at any age; however, the chance of its
occurrence increases nearly five-fold after the age of sixty-five.
- Heredity: Macular degeneration tend to "run in families." This means that there is a
genetic factor that predisposes a person toward developing the condition. Anytime a
close genetic relative has macular degeneration, you run an increased chance of
developing the condition.
- Gender: Women have a slightly higher incidence of developing macular
degeneration than men.
- Ethnic Background: Fair-skinned people of northern European ancestry
(Scandinavian, English, or German descent) have a slightly higher chance of
developing macular degeneration.
- Eye Color: Blue-eyed individuals are more prone to develop the condition than
brown-eyed persons.
- Cardiovascular History: A history of heart disease or stroke is associated with a
higher incidence of macular degeneration.
- High Cholesterol Levels: High levels of blood serum cholesterol are associated
with an increased tendency to develop macular degeneration.
- Smoking: Macular degeneration tends to occur more frequently in persons who
smoke. Even after treatment, smokers are reported to have a greater chance of having
macular problems recur. A report published in the Journal of the American Medical
Association confirmed that cigarettes contribute to age related macula degeneration.
Two large studies of over 50,000 people concluded that smokers face at least two
and a half times greater risk for ARMD than non-smokers.
How is Macular Degeneration Treated?
Although there is no proven treatment for dry macular degeneration, some people believe
that antioxidants or zinc supplements may help. A study from the Department of Veterans
Affairs seems to confirm the long suspected relationship of antioxidant nutrients and
ARMD. This study showed that men taking a broad spectrum antioxidant tablet containing
vitamin E, beta carotene, selenium, vitamin C and other micronutrients stabilized or halted
the progression of the disease. Good sources of these include greens, carrots, spinach,
broccoli and the like.
Out-patient laser surgery may be an option for people with more severe wet macular
degeneration. The laser beam is used to destroy the abnormal blood vessels and works
best when these vessels have not grown under the macula. Laser surgery is less helpful
when the abnormal blood vessels have already grown under the macula. In this case,
the laser might cause as much damage as the presence of abnormal blood vessels. This
is why early diagnosis is so important.
The "good" news about macular degeneration is that even though people who have it
experience mild to severe vision loss, macular degeneration does not affect peripheral,
or side vision. One does not go blind. With the help of low vision aids, people can
continue to enjoy many of their favorite activities and can still lead normal, independent lives.
Most of low vision aids combine magnification and bright lights. But vision aids aren't like
glasses which allow you to see whatever you're looking at when you put them on. One
kind of vision aid may be helpful when you read but totally ineffective when you watch
TV or focus on something in the distance. People need to try different types for different
situations.
For an individual with macular degeneration, it is highly recommended that a regular
schedule of eye examinations be maintained. During these examinations, detailed
documentation is made through photographs and fluorescein angiography scans of the
health of the retina. With this information, your eye doctor is better able to monitor the
condition and note any changes that may occur.
What is an Amsler Grid?
Early detection of changes in the central sight area is vital to safeguarding vision from
needless loss due to macular degeneration and diabetic retinopathy. If you are at risk for
developing macular degeneration or have diabetes, it is wise to check the vision in each
eye each day. Early detection of a problem with vision increases the chance of saving
eyesight through timely laser treatment.
A simple test of vision quality that detects even minor changes when they first occur is the
use of the Amsler Grid. The Amsler Grid is a chart that can reveal signs of wet macular
degeneration. You can get one from your ophthalmologist and test your vision at home.
This easy test only takes a moment for each eye. The results can give you timely warning
of changes in your retina that warrant immediate attention by an ophthalmologist.
Instructions for using Amsler Grid at home:
1. Wear your reading glasses
2. Hold the Amsler grid at a normal reading distance
3. Cover one eye
4. Look at the dot in the center of the grid
5. Note how the lines and squares appear.
6. Test the other eye in the same manner
All of the lines should be straight and the squares of a uniform size. If you note any
changes in the appearance of the grid, such as distortion, blurring, discoloration, dark or
missing areas of the grid, or any other changes, call and see your eye doctor immediately.
Do not wait to see if the changes will clear on their own. Timely treatment is vital to
safeguarding your vision.
If a diagnosis for wet macular degeneration is made by your ophthalmologist, you should
use the grid on a daily basis to check for changes in your vision.
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