Age-related macular degeneration
Dry Macular Degeneration
symptoms may be very subtle at first, and scarcely noticeable. In fact, most
people who are in the initial stages of Age-Related Macular Degeneration
perceive no vision loss whatsoever. In the intermediate and advanced phases,
various vision problems may become evident. These include:
1.
The need for
increasingly bright light when doing close work or reading.
2.
Increasing blurriness of
printed words.
3.
Difficulty adapting to
low light levels. (For example, requiring a long period of adjustment when
entering a darkened theatre from a brightly lit lobby.)
4.
A dimming or decrease in the perception of the intensity of color.
5.
A gradual increase in
the haziness of overall vision.
6.
General visual disturbances.
7.
Difficulty recognizing
faces.
8.
A blurred spot in the
center of one's visual field.
If only one eye is
affected by dry AMD, the other eye may compensate, masking any symptoms.
An ophthalmologist may
be able to diagnose dry AMD before the patient notices any vision loss, by
assessing the presence of drusen during a dilated eye test. Drusen are
plaque-like deposits under the retina. If these deposits are small and few,
vision may not be affected. The proliferation or growth of drusen, however, may
indicate a progression to the next stage of the disease. Pigmentation changes
may also be noticeable.
Geographic atrophy of
the macula
During the intermediate phase of the disease, some effects of AMD may be alleviated by
providing the patient with an environment that features brighter lighting,
color contrast, and reduced glare. This may help the patient to perform tasks
such as reading, sewing, knitting, or recognizing faces. When a patient is in
advanced stages of AMD, he or she will be far less able to do these tasks.
Peripheral vision will
usually, remain unaffected by AMD, so those who develop the disease very rarely
lose all of their sights. However, even though only 2.1% of the visual field is
made up by the macula, almost half of the visual cortex is devoted to
processing signals from that area.
As vision in the blurred
central region worsens, it becomes a blind spot or "scotoma.” A rare
symptom of AMD can be "Charles Bonnet Syndrome,” a complex form of hallucination.
Sufferers may see small animals, people, or geometric shapes in the scotoma.
For example, a person with Charles Bonnet Syndrome who is watching television
may "see” a tiny monkey sitting on the television. Charles Bonnet Syndrome
is usually temporary, most often lasting one year to eighteen months.
While there is no
benefit to treating dry AMD patients in the initial phase of the disease, and
no proven effective treatment for those with advanced AMD, there is available
therapy that can help sufferers in the intermediate phase. Researchers have
found that doses of antioxidant carotenoids can delay the onset of the advanced
form of AMD. These are lutein, zeaxanthin, and meso-zeaxanthin (MZ,) the three
carotenoids that make up the pigment of the macula. Supplementing patients with
these three antioxidants, particularly MZ, can help to protect the macula,
thereby allowing dry AMD sufferers to keep vision longer.
Gene therapy or macular degeneration vitamins
Macular Degeneration has
been treated with vitamin therapy for several years now. In1996, the National
Eye Institute in the US began a broad-based, decade-long study of eye
conditions are known as AREDS (Age-Related Eye Disease Study.) The study, completed
in 2006, found that a daily supplement containing high levels of several
antioxidants plus zinc reduced the risk of developing advanced Macular
Degeneration by about 25 percent.
The multivitamin supplement used in the first AREDS contained:
·
Vitamin C - 500 mg
·
Vitamin E - 400 IU
·
Beta-carotene - 15 mg
(the equivalent of 25,000 IU of vitamin A)
·
Zinc (as zinc oxide) -
80 mg
·
Copper (as cupric oxide)
- 2 mg
A second AREDS study is
now underway; it aims to report findings in December of 2012. This study is
going to look specifically at the possible benefits of Omega-3 fatty acids and
two xanthophylls: lutein and zeaxanthin.
It's now believed
that the addition of a third substance, meso-zeaxanthin, can, in many cases,
halt progression of the disease.
The Macula, macular pigment
and macula lutea
The macula is an area at
the centre of the retina. The feature was known as the "macula lutea” in
ancient times, which means "yellow spot” in Latin. In the centre of the
macula is an area known as the macular pigment. The pigment is thought to
filter UV rays, blocking blue light from reaching the retina. This prevents the
light-induced oxidative damage that could lead to Macular Degeneration.
The macular
pigment is made up of three carotenoids: lutein, zeaxanthin, and
meso-zeaxanthin.
Two of these
organic compounds are naturally occurring in food. Lutein and zeaxanthin are
found in green leafy vegetables such as kale, spinach, turnip greens, and
collards. Smaller amounts of these xanthophylls can be found in green peas,
broccoli, corn, carrots, and green beans. A non-vegetable source for them is
egg yolk.
Meso-zeaxanthin is
created in the retina from ingested lutein.
The xanthophylls are
thought to protect the retina against free radicals, unstable molecules that
play a part in many diseases.
New Research
Recent research suggests
that the key to preventing and treating Macular Degeneration lies with the
macular pigment.
Two studies, one
in Investigative Ophthalmology and one in Visual Science, found that eyes with
greater levels of macular pigment were less likely to have or develop Macular
Degeneration.
In a 2010 article
published in the Archives of Biochemistry and Biophysics, study authors concluded
that lutein, zeaxanthin and meso-zeaxanthin filter short-wavelength light and
prevent or reduce the generation of free radicals in the retinal pigment
epithelium and choroid.
Two studies in
Archives of Ophthalmology found that elevated levels of lutein and zeaxanthin
coincided with a lower incidence of cataracts, as well as Macular Degeneration.
Nutrition &
Metabolism published study findings to suggest that a nutritional supplement
containing meso-zeaxanthin, lutein and zeaxanthin effectively increased the
optical density of the macular pigment in the eyes of the majority of human
subjects.
Preserve
This recent research
suggests new ways to prevent and treat Macular Degeneration. A healthy diet,
regular exercise, protecting eyes from sun damage and supplementing with
xanthophylls can help patients at risk of developing advanced Macular
Degeneration – preserving vision and improving quality of life.
Macular Degeneration test
Macular degeneration is
one of the leading causes of vision loss among those over 65. The disease
involves the deterioration of the macula -- the central part of the retina --
and results in the loss of central vision. This detailed vision is necessary
for reading, driving, and even recognizing faces. Age-related macular
degeneration (or AMD) results in a serious loss of independence and quality of
life for sufferers of the condition.
However, in recent
years, researchers have found promising new treatments for both types of
macular degeneration, wet and dry. These treatments are now being tested, and
hold out new hope for seniors diagnosed with AMD.
Photodynamic therapy
Wet AMD occurs when
abnormal, leaky blood vessels grow behind the macula. Bleeding and scarring
damages the eye's photoreceptors, often causing severe damage in a relatively
short amount of time.
Previous
treatments for wet AMD were laser surgery and photodynamic therapy. These
proved somewhat effective, but laser surgery sometimes damaged healthy tissue,
and photodynamic therapy had to be repeated very often. The latest treatments
involve regular anti-VEGF injections into the vitreous humor of the eye. These
anti-growth factor agents inhibit the growth of abnormal veins, and can cause an improvement of vision.
Multiple system atrophy
Perhaps the most
exciting research is being done on the "dry” form of AMD, which causes
atrophy of the cells of the macular region. Previously, there was no medical
treatment proven to cause improvement for dry AMD, but in 2001 a large study
proved that vitamin supplements during the intermediate phase of dry AMD could
slow the disease's progress. And now, recent studies on antioxidant carotenoids
are showing promising results.
It's now thought
that dry AMD may be caused by life-long oxidated insult, which leads to the
death of photoreceptors in the central retina. Increased risk for AMD may
happen due to insufficient levels of the carotenoids that make up macular
pigment. This macular pigment is believed to shield photoreceptors from blue
light, which causes photooxidation and to fight free radicals, which
proliferate in the area.
Several new
studies featuring human subjects have used supplements of these carotenoids in
an effort to increase the density of macular pigment. One study gave subjects high
doses of lutein and zeaxanthin; a second added meso-zeaxanthin to the mix. Both
studies, which were broad-based and included a placebo control group, used
flicker photometry to take measurements. And both studies showed increases in
pigment density, in active groups, but not in placebo groups. No adverse
effects on other organ systems were found.
Perhaps the most
exciting findings were from the group that included meso-zeaxanthin in its
study. MZ, as it's known, lutein, and zeaxanthin were supplemented in equal
measures to some subjects. The mix proved to be much more effective than any of
the carotenoids on their own, and more effective than the lutein-zeaxanthin
mixture. Researchers hypothesize that although North Americans ingest
relatively high levels of lutein and zeaxanthin through food, they don't get
much MZ from their diets. This could mean that MZ deficiency is common, and may
perhaps be a cause of AMD.
Conclusion
Further research is
required, but it may be that these exciting breakthroughs in the treatment of
age-related macular degeneration will lead to a cure in our lifetime.
Click here for more interesting articles.
