Should a embolus on routine eye exam prompt carotid duplex studies?

Kimmy Goyal, MD Ohio State University, Columbus, Ohio

Should a cholesterol embolus on routine eye exam prompt carotid duplex studies?

Evidence-based answer

Carotid duplex studies should only be initiated if there are symptomatic visual complaints by the patient. In asymptomatic patients, these retinal emboli (a.k.a Hollenhorst plaques) have a poor predictive power for further hemispheric events and are not highly correlated with significant carotid artery disease (strength of recommendation [SOR]: C, 4 case series, 1 expert opinion). No randomized controlled trials [RCT] were found.

Evidence summary

Cholesterol emboli, or Hollenhorst plaques (HP's), are the most common type of emboli. They can be an incidental finding on routine eye exams and appear as small, bright, golden crystals that are refractile and made of cholesterol. They are thought to originate from ulcerations of atherosclerotic disease of the carotids arteries. Found most commonly at bifurcations of retinal arteries, they usually do not cause any visual signs or symptoms because blood flow is not obstructed. If vision is affected, it is often transient because the emboli are pliable. If the emboli obstruct a retinal vessel, which is rare, then subsequent occurs, resulting in loss of vision.

Patients with Hollenhorst plaques tend to be elderly, and have a higher prevalence of systemic diseases such as hypertension, hyperlipidemia, coronary artery disease, and diabetes mellitus (1).

Available research consists primarily of case series studies and expert opinions. The general consensus among these is that, in asymptomatic patients, findings of Hollenhorst plaques do not correlate with significant carotid artery disease or subsequent cerebrovascular events. Therefore, no urgent workup is necessary.

Asymptomatic HP's are not highly correlated with surgically correctable carotid disease

In 1986, Bunt published a case series report in which 60 people with visual complaints were evaluated (2). 18 patients had asymptomatic HP's, 50% of whom had ipsilateral carotid bifurcation disease. However, only 16% of these had a surgically correctable amount of stenosis. Half of the patients with asymptomatic HP were evaluated with serial fundoscopic exams, which showed that the plaque persisted in all of them. Four patients had a persistent plaque for greater than 6 months, and five patients for greater than 1 year. Despite this, no patients had retinal or cerebrovascular symptoms, transient or permanent. This study concluded that cholesterol emboli are poorly predictive of future symptomatic embolic events and not highly correlated with surgically correctable carotid disease.

Visual complaints in patients with HP's does not frequently correlate with the location of emboli

In 1990, Schwarcz et al performed a retrospective review of 64 patients with HP's to determine if any had associated visual complaints or significant (3). The focus was to determine if carotid endarterectomy prevented the occurrence of visual symptoms or plaques. 109 HP's were seen in 75 eyes. 14 of the 75 eyes with HP's had visual defects, but only 4 of these defects corresponded to the location of the emboli. The study concluded that the cerebral hemisphere ipsilateral to the asymptomatic emboli had only a slight increase in risk of TIA or .

A survey of physicians’ responses

Alexander carried out a pilot survey in 1992 regarding the management of patients with asymptomatic HP's by various health care providers (4). These emboli were detected on routine health examination. He surveyed various specialties of medicine and noted a wide variation in the methods of workup and management. He concluded that there is a need to standardize the care for patients with asymptomatic Hollenhorst plaques.

Asymptomatic HP and the risk of stroke

Between 2000 and 2005, Dunlap et al. performed a retrospective case series from the Cleveland Clinic (5). They identified 130 patients, 95 of whom had Hollenhorst plaques. The study also included patients with other ocular findings – central or branch retinal artery occlusion. During the study, patients with a mean age of 68 had optical exams. 39% of these patients were asymptomatic. This cohort included a high prevalence of hypertension, diabetes, hyperlipidemia, and tobacco use of 73%, 33%, 75% and 38%, respectively. Most of the patients had carotid studies. These showed only 8% of the patients to have ipsilateral carotid bifurcation stenoses of >60%. Ipsilateral stenosis of <30% occurred in 68% patients and 30-60% stenosis in 22%.

Despite the presence of co-morbidities, none of the patients experienced any documented or TIAs during a follow up period ranging 1 to 49 months (median of 22 months). Serial dopplers did not show progression of the carotid stenoses. The study concluded that the presence of an HP was not associated with a high risk of stroke and had a low prevalence of carotid disease requiring surgical intervention.

Coutu, O.D., published a report in 1993 (6) concluding that there is no correlation between asymptomatic cholesterol emboli and ipsilateral carotid artery disease. He opined that these emboli are a poor predictor of future hemispheric events such as transient ischemic attacks or strokes.

Even symptomatic HP's are a poor predictor of significant carotid stenosis

Another retrospective study, performed by Wakefield et al., reviewed all patients between 1996 and 2001 who were evaluated for vision complaints and received a carotid duplex exam (7). A total of 3560 carotid duplex exams were performed and the results showed that only 11.1% of the patients found to have Hollenhorst plaques had significant carotid disease. Though this study focused on symptomatic patients, in whom they recommend a screening carotid doppler exam, the cholesterol emboli were still a poor predictor of significant carotid stenosis.

Recommendations

A thorough literature search through the Agency for Healthcare Research and Quality Evidence Reports, National Guidelines Clearinghouse, Institute for Clinical Systems Improvement, and the Cochrane Database of Systematic Reviews did not yield any guidelines or consensus statements regarding carotid imaging studies following incidental discovery of Hollenhorst plaques. The US Preventive Services Task Force did not comment on this either.

A review of the literature produced four case series reports, each suggesting that asymptomatic Hollenhorst plaques did not correlate with significant carotid artery disease or a high prevalence of future neurologic events. Based on this, no urgent carotid workup is necessary.

References

1. Sowka J, Gurwood A, Kabat A. Hollenhorst plaque. Handbook of ocular disease management. Available at www.revoptom.com/handbook/sect51.htm. Accessed December 2, 2008.

2. Bunt TJ. The clinical significance of the asymptomatic Hollenhorst plaque. Journal of vascular surgery. 1986; 4(6): 559-62.

3. Schwarcz TH, Eton D, et al. Hollenhorst plaques: retinal manifestations and the role of carotid endarterectomy. Journal of vascular surgery. 1990; 11(5): 635-41.

4. Alexander LJ. Variations in physician response to consultation requests for Hollenhorst plaques: a pilot study. Journal of the American optometric association. 1992; 63(5): 326-32.

5. Dunlap AB, et al. The fate of patients with retinal artery occlusion and Hollenhorst plaque. Journal of vascular surgery. 2007; 46(6): 1125-9.

6. Coutu R. Treatment and management of the Hollenhorst plaque. Clinical eye and vision care. 1993; 5(2): 52-8.

7. Wakefield M, O’Donnell S, Goff J. Re-evaluation of carotid duplex for visual complaints: Who really needs to be studied? Annals of vascular surgery. 2003; 17(6): 635-40.