External carotid artery to ophthalmic artery flow associated with internal carotid artery stenosis

Purpose: One of the most devastating complications of facial filler injection is sudden ischemic blindness. However, its mechanisms and predisposing factors are poorly understood. The purpose of this study was to investigate the prevalence of external carotid artery (ECA) to ophthalmic artery (OA) anterograde flow in patients with internal carotid artery (ICA) stenosis and in a control population without carotid disease. Methods: In this cross-sectional cohort study, two groups of patients who underwent catheter cerebral angiography over a 5-year period were identified: patients with symptomatic ICA stenosis and a control group of patients with refractory epistaxis undergoing embolization. Angiograms were reviewed by an interventional neuroradiologist. The primary outcome measure was the presence of ECA to OA flow, defined as choroidal blush before filling of the circle of Willis. Secondary outcome measures included the percentage and location of ICA stenosis and ECA anastomotic branches involved. Results: The study included 149 patients with ICA stenosis and 69 control patients. ECA to OA flow was more prevalent in patients with ICA stenosis (34.9%) compared to controls (2.9%) (p <.001). Logistic regression demonstrated that for each 10% increase in ICA stenosis over 70%, there was 2.8 times increased risk of ECA to OA flow (p <.001). Conclusions: ECA to ICA anterograde flow can be demonstrated in approximately 3% of control patients and in over 1/3 of patients with symptomatic carotid stenosis. This provides a plausible pathway for small filler particles to pass with blood flow from the facial to the ophthalmic circulation.