By
Jonathan Yoken, MD
RETINAL
ARTERY OR VEIN OCCLUSION
In the eye,
as in the rest of the body, blood is carried in by arteries and
carried out by veins. Inside each eye, there is just one main
artery and one main vein to serve all the circulation needs of
the retina. These vessels are extremely small, measuring 1/10th-
1/5th of a millimeter. If one of these blood vessels develops
a blockage, the retina served by that vessel will not function
normally, resulting in loss of vision.
What are
the different types of vessel blockages that can occur?
Blockage may occur either in a vessel bringing blood to the eye
(the artery), or carrying blood away from the eye (the vein).
If only a small branch of the circulation becomes blocked, only
a small portion of the field of vision may be affected. This is
called a branch retinal artery or vein occlusion. If the
main or central vessel is blocked, the entire field of vision
may be affected. This is called a central retinal artery
or vein occlusion.
Why do
these blood vessel blockages occur?
In many cases,
no specific "cause" is identified. These blockages probably
develop for the same reason that blood vessels become damaged
in the rest of the body. Blood vessel blockages may be more common
in patients with high blood pressure, glaucoma, diabetes, certain
blood disorders and in smokers. It is also more common in older
patients. Your doctor may suggest certain tests to rule out unusual
conditions such as blood cell abnormalities, inflammation of blood
vessels, or abnormalities elsewhere in the cardiovascular system.
These tests are extremely important in ensuring that no other
medical problems are present, but in many case, no definitive
cause can be identified.
Can these
blockages be repaired?
Unfortunately,
there is currently no definitive way to reopen a blocked vessel
in the retina. In some cases the body may be able to re-open or
bypass the blockage through natural healing mechanisms, but the
damage done, even with a temporary interruption in blood flow
may be permanent.
Can anything be done to improve my sight?
The answer
to the question very much depends on the type of blood vessel
occlusion which has occurred, and how much of the retina is involved.
Certain types of vein occlusions which cause swelling in the part
of the retina called the macula (cystoid macular edema) can benefit
from a type of laser treatment. Occasionally, surgery or steroid
injections may be recommended in severe cases. You should discuss
this issue with your doctor.
Are there any complications which can develop following a blood
vessels blockage in the retina?
When a vessel
in the eye becomes blocked, the retina no longer receives oxygen
and nutrients. This causes the retina to send out a chemical signal
which causes new blood vessels to grow. While this might seem
like a good solution, the new vessels which grow are abnormal-they
break open easily and may cause hemorrhage, and they grow in abnormal
places within the eye which can result in a sudden, severe increase
in the pressure of the eye called neovascular (new blood vessel)
glaucoma. Increased pressure in the eye is the most feared complication
of a vessel blockage, and can result in severe pain, nausea, and
further loss of vision. New blood vessel growth may occur in any
type of blood vessel blockage, but is more common in vein than
in artery occlusions, and is more common in central than in branch
occlusions.
Your doctor
will be monitoring your condition over the next several months
to watch for the development of any of these problems. If new
vessels seem to be developing, a type of laser treatment may be
performed which can be effective in treating this potentially
serious complication.
