| What
is the Carotid Artery?  The
two carotid arteries are the main arteries in the neck.
They supply blood to the head, including the eyes and the
brain. One carotid artery supplies the right side, while
the other serves the left. Cholesterol and blood clots can
form in the carotid artery, which can cause blockage at
that site or can break off in small pieces that flow downstream
and cause blockage of smaller branches in the eye or brain.
Because the eye and the brain share the same source of blood
supply, blockages or conditions of the carotid artery can
affect either.
What
Happens When the Carotid Artery is Blocked?
 Depending
on where the blockage occurs and how complete the blockage
is, different symptoms can result: If a piece of cholesterol
or a blood clot breaks off from the carotid artery and travels
to the eye, the circulation to some part or all of the retina
can become affected.
A Central Retinal Artery Occlusion
(CRAO) occurs when the main artery to the retina becomes
totally blocked, causing sudden total vision loss. Later
complications may include growth of abnormal vessels and
bleeding inside the eye, or a severe, painful form of acute
glaucoma (high eye pressure).
In a Branch Retinal Artery Occlusion (BRAO), one of the
smaller branches inside the eye is blocked, and only a portion
of the vision may be lost. This appears as a sudden “blackout”
of a segment of the vision. Sometimes, a piece of cholesterol,
known as a Hollenhorst Plaque, can be seen at the edge of
the blockage. Sometimes such a plaque is seen in a retinal
artery with no sign of active blockage. Although this causes
no symptoms, it serves as a warning sign of possible imminent
problems.
When the branches of the carotid artery going
to the brain are blocked, a Cerebrovascular Accident (CVA
or stroke) may result. Depending on the part of the brain
involved and the size of the area affected, the effects
of a stroke may be mild or devastating. Severe effects can
include paralysis of one side of the body and loss of speech.
If the part of the brain having to do with vision is involved,
a stroke can lead to loss of side vision. If blood supply
to the eye or brain is slowly cut off, more subtle symptoms
may occur. Chronic poor circulation to the brain can cause
dementia-like symptoms and vague neurologic problems. Slow
circulation to the eye, known as Ocular Ischemic Syndrome,
can cause vague episodes of vision loss, pain and sometime
small hemorrhages within the retina. These eyes can rapidly
develop abnormal new vessel growth inside the eye and severe
glaucoma after otherwise uneventful cataract surgery.
Is
This Damage Permanent?
Not everyone who suffers a blocked
blood supply to the eye or brain has permanent damage. A
temporary blockage of blood supply to the brain, called
a transient ischemic attack (TIA), may result in muscle
weakness in the face or an arm or leg, lasting only a few
minutes to a few hours. A temporary blockage of blood supply
to the eye, called amaurosis fugax, or fleeting blindness,
can cause a temporary loss of vision in one eye. This sometimes
appears as a dark curtain descending over all or part of
the vision in that eye and may last for a few minutes to
several hours. Both amaurosis fugax and transient ischemic
attacks are possible warnings of a serious problem involving
the blood supply to the eye or brain. They should be reported
to your eye doctor or primary care physician.
Are
There Other Signs of Carotid Artery Disease?
As part of a routine eye exam,
the eye doctor may dilate the pupil to examine the retina
at the back of the eye. During this procedure conditions
are sometimes discovered, which may indicate an increased
risk of stroke. If a piece of cholesterol, or plaque, is
found during a routine eye exam, further evaluation may
be indicated. Other similar plaques may break off from the
carotid artery, block the brain's blood supply and cause
a stroke.
What
Further Tests or Treatments May Be Needed?
Rarely, an inflammatory condition
called Giant Cell Arteritis can inflame smaller vessel supplying
the eye or brain. This can be diagnosed with a blood test
and/or small artery biopsy. Ultrasound can provide a very
detailed look at the carotid flow. Sometimes, a special
X-ray test called a carotid angiogram may be done. Angiography
involves injecting an iodine-containing dye into the artery
and taking pictures of the blood flowing into the brain.
If an abnormality is found, surgery may be recommended to
correct the blockage. With some obstructions, only medications
are necessary.
Routine, comprehensive medical eye examination can help
ensure healthy vision and can provide important information
concerning carotid artery disease. If problems are detected,
your eye doctor will work with your other medical doctors
to coordinate your complete medical care.
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to the Retina Center
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