|
What is a branch retinal
vein occlusion?
The retina is a thin tissue in the back of your eye that
consists of nerve cells. These nerve cells capture
images that you see, much like the film of a camera.
These nerve cells transmit the image via the optic nerve
to your brain allowing you to see. The center portion of
the retina is called the macula and this where our best
vision comes from. Our ability to do things like driving
and reading comes from the function of the nerve cells
in our macula.
|
|
|
Normal |
|
|
|
BRVO |
The retina is nourished
by tiny blood vessels that bring blood flow into the eye
(arteries) and out of the eye (veins). The arteries
travel very close to the veins and occasionally an
artery will compress the underlying vein, making it
difficult for blood to exit the eye. This blockage,
called a branch retinal vein occlusion (BRVO), causes
increased back-pressure in the vein, causing it to
expand and leak fluid and blood. The main central vein
exiting the eye can also become blocked as it travels
through the optic nerve, and this is called central
retinal vein occlusion (CRVO). Retinal vein occlusions
are eye conditions commonly seen by retina specialists.
They are second only to diabetic retinopathy as a cause
for vision loss due to retinal blood vessel diseases.
While there are similarities in the causes and clinical
nature of branch retinal vein occlusions (BRVO) and
central retinal vein occlusions (CRVO), there are
significant differences in their management and
prognosis.
What are the causes of
a branch retinal vein occlusion?
Branch retinal vein occlusions are the most common form
of retinal blood vessel blockages. Males and females
are, in general, affected equally. Most occlusions occur
after the age of 50, although younger patients are
sometimes seen with this disorder. The highest incidence
is in individuals in their 60s and 70s. The major risk
factor for a branch retinal vein occlusion is
atherosclerosis or hardening of the blood vessels.
Specifically, the artery gets hardened and thickened and
compresses the underlying vein. Therefore, the risk
factors for this disorder are similar to those for other
blood vessel blockages elsewhere in the body, such as
stroke and coronary artery disease. Specifically, aging,
high blood pressure, diabetes, elevated blood lipids,
and smoking are all risk factors. Having glaucoma has
also been identified as a risk factor in some studies.
There are other much less common conditions which may
put a patient at risk for developing a vein occlusion,
including blood clotting abnormalities such as elevated
blood homocystine levels, antiphospholipid antibodies,
hyper viscosity of the blood and genetic diseases that
make a person at an increased risk for blood clotting.
Occasionally, inflammatory and infectious conditions
which cause blood vessel inflammation such as
sarcoidosis, Lyme disease, lupus, and syphilis are also
risk factors for vein occlusion. In general, unless
there is a reason to suspect these much less common
conditions, (such as a young age, or history of other
systemic problems suggestive of clotting disorders,
inflammation, or infection), extensive laboratory
testing is usually not necessary. Most patients are
asked to see their internist for a medical evaluation.
What are the symptoms
of a branch retinal vein occlusion and how is it
diagnosed?
The symptoms of a branch retinal vein occlusion depend
on which branch of the vein is involved. Most often the
affected branch involves the center of the retina
(macula), causing a reduction in vision and usually a
loss of a portion of the field of vision. Usually, this
will affect either the top half or bottom half of the
field of vision along with the central vision.
Occasionally, a branch retinal vein occlusion will
affect a vein draining a portion of the retina away from
the center vision and will not cause any symptoms and
will only be detected on examination. Sometimes patients
may be completely asymptomatic when the other eye sees
normally, and not realize that there has been decreased
vision in one eye. For this reason, it is always a good
idea to periodically close one eye, and then the other,
to make sure that the vision in each eye is stable.
A person cannot diagnose
a retinal vein occlusion by looking in the mirror
because the eye looks and feels normal. A branch retinal
vein occlusion will not cause any discomfort in the eye.
The diagnosis is made through a retinal examination
through a dilated pupil. Additional testing, including a
fluorescein angiogram, is often performed to better
diagnose and assess the need for treatment. A
fluorescein angiogram is a test involving photographs,
not x-rays, in which a colored vegetable-based dye is
injected into an arm or hand vein. Several photographs
are taken as the dye passes through the blood vessels in
the back of the eye to evaluate the circulation of the
retina.
 If
you do not have a copy of Acrobat Reader you can get one
for free by clicking on the icon, or 'Get
Acrobat® Reader'. This will take you to
Adobe's website and enable you to download the Acrobat
program to your computer.
|
|
