Prognosis after Transient Monocular Blindness Associated with Carotid-Artery Stenosis

BACKGROUND: Transient monocular blindness associated with internal-carotid-artery stenosis is a risk factor for stroke. The effect of carotid endarterectomy in patients who present with transient monocular blindness has not been determined. METHODS: We compared the risk of stroke among patients presenting with transient monocular blindness with the risk among patients presenting with hemispheric transient ischemic attack. The effect of endarterectomy was assessed in patients with transient monocular blindness. The analyses were based on data from the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: A total of 198 medically treated patients with transient monocular blindness had a three-year risk of ipsilateral stroke that was approximately half of that among 417 medically treated patients with hemispheric transient ischemic attack (adjusted hazard ratio, 0.53; 95 percent confidence interval, 0.30 to 0.94). Six factors were associated with a higher risk of stroke in patients with monocular blindness--an age of 75 years or more, male sex, a history of hemispheric transient ischemic attack or stroke, a history of intermittent claudication, stenosis of 80 to 94 percent of the luminal diameter, and the absence of collateral circulation. The three-year risk of stroke with medical treatment for patients with zero or one risk factor was 1.8 percent, with two risk factors 12.3 percent, and with three or more risk factors 24.2 percent (P=0.003). The three-year absolute reduction in the risk of stroke associated with endarterectomy was -2.2 percent (i.e., a 2.2 percent increase in risk) among patients with zero or one risk factor, 4.9 percent among those with two risk factors, and 14.3 percent among those with three or more risk factors (P=0.23 by a test for interaction). CONCLUSIONS: Among patients with internal-carotidartery stenosis, the prognosis was better for those presenting with transient monocular blindness than for those presenting with hemispheric transient ischemic attack. Among patients with transient monocular blindness, carotid endarterectomy may be beneficial when other risk factors for stroke are also present.