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Age-related macular degeneration (AMD) is a deterioration or breakdown of
the eye’s macula. The macula is a small area in the retina — the
light-sensitive tissue lining the back of the eye. The macula is the part of
the retina that is responsible for your central vision, allowing you to see
fine details clearly.
Even though the macula makes up only a small part of the retina, it is much
more sensitive to detail than the rest of the retina, called the peripheral
retina. The macula is what allows you to thread a needle, read small print,
and read street signs. The peripheral retina gives you side (or peripheral)
vision.
If someone is standing off to one side of your vision, your peripheral
retina helps you know that person is there by allowing you to see their
general shape. It is your macula that allows you to recognize the details of
the person’s face.
Many older people develop macular degeneration as part of the body’s natural
aging process. There are different kinds of macular problems, but the most
common is age-related macular degeneration.
The retina is made up of many layers that work together to help you see
clearly. AMD develops when a layer under the retina called the retinal
pigment epithelium (RPE) is affected by deposits of tiny yellow or white
pieces of fatty protein called drusen, or by other age-related changes.
With AMD, you may have blurriness, dark areas or distortion in your central
vision, and perhaps permanent loss of your central vision. It usually does
not affect your side, or peripheral vision. For example, with advanced AMD,
you could see the outline of a clock, yet may not be able to see the hands
of the clock to tell what time it is.
AMD alone almost never causes total blindness. People with more advanced
cases of AMD continue to have useful vision using their side, or peripheral
vision. In many cases, macular degeneration’s impact on your vision can be
minimal.
When AMD does lead to loss of vision, it usually begins in just one eye,
though it may affect the other eye later.
Many people are not aware that they have macular degeneration until they
have a noticeable vision problem or until it is detected during an eye
examination.
There are two types of AMD:
Dry, or atrophic, AMD (also called non-neovascular AMD). Most people who have AMD have the dry form. This condition is caused by
aging and thinning of the tissues of the macula. Macular degeneration
usually begins when tiny yellow or white pieces of fatty protein form under
the retina. These deposits are called drusen. Eventually, the macula may
become thinner and stop working properly. With dry AMD, vision loss is
usually gradual.
Wet, or exudative, AMD (also called neovascular AMD). The wet form of macular degeneration occurs in about 10 percent of all
macular degeneration cases, but it can cause more damage to your central or
detail vision than the dry form.
Capillaries, or tiny blood vessels, extend into all tissues of the body,
bringing in nutrients and carrying off waste products. Capillaries usually
don’t increase in size or number, but if they do, it is called abnormal
blood vessel growth.
Wet AMD occurs when abnormal blood vessels begin to grow underneath the
retina. This blood vessel growth is called choroidal neovascularization
(CNV) because these vessels grow from the layer under the retina called the
choroid. These new blood vessels may leak fluid or blood, blurring or
distorting central vision. Vision loss from this form of AMD may be faster
and more noticeable than that from dry AMD.
The longer these abnormal vessels leak or grow, the more risk you have of
losing more of your detailed vision. Also, if abnormal blood vessel growth
happens in one eye, there is a risk that it will occur in the other eye. The
earlier that wet AMD is diagnosed, the better chance you have of preserving
some or much of your central vision. That is why it is so important that you
and your ophthalmologist monitor your vision in each eye carefully.
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