Retinal Artery Occlusions and Carotid Artery Disease
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.