Age
Related Macular Degeneration, or ARMD, is a common,
chronic eye disorder that affects older people
and whose central feature is visual loss and blindness.
The onset of the disease occurs around 50 years
of age and total blindness usually at around 75
years of age, in people in developed countries.
Despite considerable research on the disease the
causes remain unknown.
ARMD occurs due to degeneration of the macula,
which is located at the center of the retina
and is the most sensitive part of it, containing
the cones. It is these cones that are responsible
for giving us daylight, sharp and central vision
needed to do common tasks like reading or moving
around. It is because the macula is affected
that the central vision is lost in ARMD. The
disease, however, causes no pain.
Types of Age Related Macular Degeneration
Macular degeneration is of two types, dry or
non-neovascular and wet or neovascular. Dry ARMD
accounts for 80% of the diagnosed cases but wet
ARMD accounts for 80% of the severely visually
impaired cases.
Dry or non-neovascular ARMD: Dry ARMD is an
early stage of the disease resulting from aging
and thinning of the macular tissues, pigment
deposits or both. In dry ARMD, light sensitive
cells of the macula gradually break down, slowly
blurring the central vision. You will then need
more light to see objects.
It is diagnosed as dry ARMD when yellow spots
called drusen, formed from the deposits, are
observed on the macula. Dry ARMD usually produces
a gradual loss of vision, but the condition is
not as severe as in wet ARMD. The disease can
affect both eyes but vision may be lost in only
one eye.
Wet or neovascular ARMD: About 10% of the dry
ARMD cases progress to a more severe form of
the disease called wet or neovascular ARMD. Neovascularization
refers to growth of new blood vessels, which
is what happens in wet ARMD. Forming new blood
vessels is body’s aberrant way of responding
to the degenerating retina’s demand for
more blood. These new arteries are formed beneath
the retina. They have weak walls which leak blood
and fluid to the retina, thus permanently destroying
some light sensitive retinal cells, producing
dark spots in your vision. This leakage may lead
to scarring and central vision loss. With wet
ARMD loss of vision can occur quickly.
Signs and symptoms
For dry ARMD the most common early sign is blurred
vision. As the macula deteriorates you will less
and less. However, in bright light you will see
well. With further deterioration of the macula
you will see a growing blind spot in the centre
of your vision.
In wet ARMD the classic early symptom is straight
lines appearing crooked. This happens when the
leaking fluid lifts the macula distorting the
vision.
For ARMD in general, viewing the Amsler grid,
which is a chart containing black lines in a
graph pattern, is a surer way to see if you have
this disease.
Visiting an eye practitioner is the best way
to confirm ARMD. He will often detect early signs
of ARMD before the symptoms appear. He will do
all the tests including fluorescein angiography,
which examines the blood vessels on the retina.
Risk factors in ARMD
Besides older people, whites and female seem
to be more prone to ARMD. The disease may be
a side effect of some drugs. In some cases it
is believed to be hereditary.
Latest evidence suggests that smoking could
be a high risk factor. Other risk factors include
obesity, high blood pressure and lighter eye
color. However, conclusive evidence is lacking
about these risk factors.
Treatment
There is no FDA approved cure for ARMD. There
are some treatments which slow down the progress
of the disease or improve the vision. Treatment
depends on whether it is dry or wet ARMD.
For dry ARMD, a study conducted by a major research
institute has produced strong evidence that vitamin
A, C and E may slow down the progress of the
disease, if not prevent it. The study also concluded
that high doses of certain nutritional supplements
could reduce the chances of progression by 25%.
Some doctors advise sun glasses for dry ARMD
patients as protection against ultra violet light.
For wet ARMD, drugs like the FDA approved Lucentin
and Macugen used with Photo Dynamic Therapy have
been shown to stop or slow down the formation
of new blood vessels. Lucentis has also been
able to improve vision in some cases.
