February 01, 2010
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Quickly refer patients with potential carotid artery occlusion

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In potentially fatal carotid artery disease, optometrists have the opportunity to make the first diagnosis. If carotid artery occlusion is suspected, noninvasive testing and scoring can determine whether a patient needs to be urgently referred to a vascular surgeon.

Identify at-risk patients

Carotid artery occlusion is seen in a specific patient group. Typical at-risk patients are older than 55, and many have diabetes and a history of smoking.

John A. McGreal, OD
John A. McGreal

John A. McGreal, OD, advises optometrists to pay close attention to elderly patients meeting those criteria who report transient vision loss.

“Typically, a patient has ipsilateral blurred vision, or some focal neurological deficit. But the most telling clinical sign is transient ischemic attack, which is when there is temporary loss of vision or neurological function but the patient quickly recovers,” Dr. McGreal told Primary Care Optometry News.

Another symptom that might raise a red flag would be when a patient reports ischemic diplopia, PCON Editorial Board member John A. McCall Jr., OD, said in an interview.

“Anytime a patient has double vision, it’s due to a microclot,” he said. “At this point in time, I want to find out if this is a sign this patient has a blockage or some malignant flow through a carotid artery. And at this stage, this patient is a walking time bomb for a stroke.”

Calculating stroke potential

Tammy P. Than, MS, OD, FAAO, determines how likely it is a patient will have a stroke based on a prognostic score first presented by Johnston and colleagues in the Lancet.

The ABCD2 score is an acronym for Age, Blood pressure, Clinical features, Duration and Diabetes. This assessment can determine the likelihood of stroke after a transient ischemic attack.

“If a patient is older than 60, they get a point,” she said. “If their blood pressure is high and they’re diabetic, that’s two more points. And if their score is high enough, you need to send the patient right away.”

Damage to the eye

Patients with carotid artery occlusion are also at risk for permanent damage to the eye from retinal vascular occlusions and glaucoma.

“If you have poor blood flow to one or both sides due to occlusion, then you are at risk for other problems related to the poor blood flow and poor oxygenation of that eye, such as branch retinal artery occlusions or central retinal artery occlusions,” Dr. McGreal said.

John A. McCall Jr., OD
John A. McCall

Another risk is low or normal-tension glaucoma, which can be caused by inadequate blood flow to the back of the eye.

“People wonder why a patient with normal or possibly even low pressure has glaucoma and why they’re progressing,” Dr. McCall said. “They’re progressing because they have a poor vascular system, and part of that might be due to them not getting sufficient flow to the brain and/or optic nerve.”

Diagnosing carotid artery disease

Optometrists can use many noninvasive tests when diagnosing the severity of carotid artery occlusion, Dr. McGreal said.

“The most important thing is to do a detailed retinal examination and look carefully at the retinal vasculature,” he said. “Clinical signs would be evidence of emboli in the retinal vascular tree, which are little cholesterol plaques that have broken off from inside the carotid artery and moved up into the retinal circulation. I also listen for turbulence in the flow of the carotid artery with a stethoscope.”

The degree of flow through the carotid artery is extremely important, Dr. McCall said. Malignant blood flow could be a sign of the most dangerous occlusion possible in the carotid artery.

“If you have a blockage, it could be just a gradual thinning of the lumen of the artery,” he said. “The worst case scenario is if the plaque starts building unevenly on one side of the artery instead of all over. When the blood flows through there, it creates a turbulent flow that could break off a piece [of the blockage] and cause instant stroke.”

Send patients for testing

Patients with turbulent flow and a high score on the ABCD2 formula should be sent for testing immediately.

“I schedule a carotid Doppler from our office,” Dr. McCall said. “And if I feel like there’s a reason to go further, I’ll order an MRI, which will show parts of the brain that have ischemia and show if this has been a series of mini-strokes. The follow-up test to that is an echocardiogram, but we don’t order a lot of those. By that time I’m going to get the patient to a vascular surgeon.”

Optometry at the forefront

According to Dr. Than, heightened awareness of the signs and symptoms of carotid artery disease is crucial when diagnosing a potential at-risk patient.

Tammy P. Than, MS, OD, FAAO
Tammy P. Than

“In the past we may not have been quite so urgent in our referrals,” Dr. Than said. “Looking at these predictors when a patient comes into your office can really make the difference in a patient’s life, and certainly in their quality of life.”

This is especially true considering how common carotid occlusive disease is in the elderly population.

“The number one most common cause of death in our country is heart disease. The third most common is stroke,” Dr. McGreal said. “And both of those patient subsets could walk through the door for an eye exam reporting symptoms of carotid occlusive disease.”

To catch these potential at-risk patients, Dr. McCall advises optometrists to look at the patient holistically.

“Sometimes we tend to get so concentrated on the eyeball that we lose the big picture,” he said. “We should never let one of these patients come through our office without a prompt referral.”

For more information:

  • John A. McGreal, OD, can be reached at Missouri Eye Associates, 11710 Old Ballas Rd., St. Louis, MO 63141; (314) 569-2020; fax: (314) 569-1596; e-mail: jamod1@aol.com.
  • John A. McCall, Jr., OD, is a Primary Care Optometry News Editorial Board member, a private practitioner and senior vice president of vendor relations for Vision Source. He can be reached at 711 East Goliad Ave., Crockett, TX 75835; (936) 544-3763; fax: (936) 544-7894; e-mail: jmccall@visionsource.com.
  • Tammy P. Than, MS, OD, FAAO, can be reached at the University of Alabama School of Optometry, HPB 513, 1530 Third Avenue South, Birmingham, AL 35294-0010; (205) 934-2941; e-mail: tthan@uab.edu.

Reference:

  • Johnston WC, Rothwell PM, Nguyen-Huynh MN, et al. Validation and refinement of scores to predict very early stroke risk after transient ischaemic attack. Lancet. 2007;369: 283-292.