Choroidal Neovascular Membrane
Choroidal
neovascular membrane (CNVM) is a problem that is related to a wide
variety of retinal diseases, but is most commonly linked to age-related
macular degeneration. With CNVM, abnormal blood vessels stemming from
the choroid (the blood vessel-rich tissue layer just beneath the retina)
grow up through the retinal layers. Imagine the abnormal blood vessels
as weeds creeping up through the cracks of a sidewalk. These new vessels
are very fragile and break easily, causing blood and fluid to pool
within the layers of the retina.
As the vessels leak, they
disturb the delicate retinal tissue, causing the vision to deteriorate.
The severity of the symptoms depends on the size of the CNVM and its
proximity to the macula. Patient's symptoms may be very mild such as a
blurry or distorted area of vision, or more severe, like a central blind
spot.
SIGNS AND SYMPTOMS
•Blurred, grayed-out
areas
•Distorted vision
•Central blind spot
DETECTION AND
DIAGNOSIS
A simple vision test called an Amsler Grid should always be
done first for patients who notice a problem with their central vision.
This test provides the retina doctor with vital information about the
location and severity of the problem. CNVM is usually difficult to
diagnose by simply looking at the retina with an ophthalmoscope. A
special dye test called a fluorescein angiogram is used to study the
circulation of the retina and show areas of leaking blood vessels.
TREATMENT
The appropriate treatment is dependent on
several factors such as: size and location of the membrane and the
amount of time that passed since the symptoms first began. If the CNVM
is small, compact, and caught very early, a delicate surgery called a
sub-foveal excision can be performed to remove it. This procedure has
the most risk but also offers the patient the best possibility of visual
improvement.
Laser photocoagulation, a procedure that seals
leaking blood vessels, is the simplest and most common treatment for
CNVM. It is reserved for patients with bleeding outside of the central
retina because it creates a scar that affects the vision. Treating the
retina with laser gives the surgeon the most control over placement and
size of the scar. Allowing an undiagnosed leak to resolve on its own
usually causes a much more devastating affect on the vision.
Unfortunately, for some patients, no treatment is appropriate. All
patients with CNVM should monitor their vision with an Amsler Grid and
report any changes to their retinal doctor immediately.
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