Amaurosis fugax progressing to retinal artery occlusion with anterior migration of a retrobulbar embolus on orbital color Doppler imaging

Abstract

Purpose: Orbital color Doppler imaging (CDI) is useful in the evaluation of sudden monocular vision loss, providing information on etiology which may guide management. We present two cases of amaurosis fugax progressing to retinal artery occlusion (RAO) associated with migration of a hyperechoic particle within the central retinal artery (CRA) and altered vascular dynamics found on CDI.

Observations: Both patients presented with amaurosis fugax, and CDI revealed a hyperechoic particle 2.8 mm from the optic nerve head in both patients. Patient 1 was found to have severe aortic stenosis and a thoracic aortic aneurysm and was managed with dual antiplatelet therapy (DAPT) while awaiting evaluation for cardiothoracic surgical repair. Ten days later, Patient 1 returned with a central RAO, and a repeat CDI showed a 1.0 mm anterior migration of the embolus with reduced CRA blood velocity and an increased resistivity index. Patient 2 was managed with DAPT and oral corticosteroids, but symptoms recurred during steroid tapering which necessitated a prolonged course of steroids. Systemic complications required reduction of steroid dosing, and the patient developed a branch RAO six months after initial presentation. Repeat CDI revealed a 0.9 mm anterior migration of the embolus, with increased CRA blood velocity and resistivity index. Systemic thrombolysis with tissue plasminogen activator and resumption of steroids did not result in visual improvement in Patient 2.

Conclusions and importance: The presence of a hyperechoic particle in the CRA on CDI can be seen with amaurosis fugax, and anterior migration with subsequent alterations in CDI parameters may correlate with clinical progression to embolic retinal ischemia. Visualization of an embolus may predict nonresponse to thrombolytic or anticoagulation-based treatment.

Keywords: Amaurosis fugax; Color Doppler imaging; Embolism; Orbital ultrasound; Retinal artery occlusion; Transient monocular vision loss.

Fig. 1

Case 1 clinical findings A. Initial orbital color Doppler imaging (CDI) of the left eye (OS) shows a hyperechoic particle within the central retinal artery (CRA), 2.8 mm posterior to the optic nerve head (ONH). B. Initial CDI OS shows patent CRA flow with peak systolic velocity (PSV) and end diastolic velocity (EDV) of 10.8 and 5.6 cm/s, respectively. C. Ten days after initial presentation, repeat CDI shows anterior migration of the same hyperechoic particle in the CRA OS, to 1.8 mm posterior to the ONH. D. Ten days after initial presentation, CDI OS shows obstruction of CRA flow by the hyperechoic particle, with decreased PSV and EDV of 6.8 cm/s and 3.2 cm/s, respectively. E: A computed tomography scan with contrast shows radiopaque calcification of the patient's aortic valve (black arrowhead). F: Optical coherence tomography OS at three month follow up shows thinning of the inner retinal layers including the ganglion cell layer. Note differences in scanning angle (A,C) and deviation from an ideal 0-degree angle (white vertical guideline probe) between the vessel of interest and ultrasound beam (B,D), which may contribute to minor error in measurements of embolus (A,C) and flow (B,D).

Fig. 2

Case 2 orbital color Doppler imaging (CDI) findings A. Initial CDI of the symptomatic right eye (OD) shows a 1.5 mm in diameter hyperechoic particle within the central retinal artery (CRA), 2.8 mm from the optic nerve head (ONH). B. Initial CDI OD shows CRA peak systolic velocity (PSV) and end diastolic velocity (EDV) of 8.9 and 3.4 cm/s, respectively. C. Initial CDI of the asymptomatic left eye (OS) shows a PSV of 16.9 cm/s and EDV of 3.2 cm/s. D. One month after initial presentation, repeat CDI OD shows a 1.5 mm in diameter hyperechoic particle within the CRA 2.8 mm from the ONH. E. One month after initial presentation, repeat CDI OD shows CRA PSV and EDV of 10.2 and 4.0 cm/s, respectively. F. One month after initial presentation, repeat CDI OS shows CRA PSV of 11.9 cm/s and unmeasurable EDV. G. Six months after initial presentation and one day prior to clinical branch retinal artery occlusion OD, repeat CDI OD shows a 1.5 mm in diameter hyperechoic particle within the CRA 1.9 mm from the ONH. H. Six months after initial presentation, repeat CDI OD shows CRA PSV of 17.5 cm/s and EDV of 4.4 cm/s. I. Six months after initial presentation, repeat CDI OS shows CRA PSV of 13.3 cm/s and EDV of 3.4 cm/s. Note differences in scanning angle (A,D,G) and deviation from an ideal 0-degree angle (white vertical guideline probe) between the vessel of interest and ultrasound beam (B,C,E,F,H,I), which may contribute to minor error in measurements of embolus (A,D,G) and flow (B,C,E,F,H,I).

Fig. 3

Patient 2 optical coherence tomography (OCT) and visual field (VF) findings in the right eye (OD) OCT of the ganglion cell layer (GCL) (A,D,G,J) and retinal nerve fiber layer (RNFL) (B,E,H,K) and visual fields (C,F,I,L) prior to (A–C) and following (D–L) branch retinal artery occlusion (BRAO). GCL shows progressive thinning from 0.9 (A) to 0.37 mm³ (J). Initial retinal nerve fiber layer (RNFL) thickening from 98 (B) to 118 μm (E) is observed shortly after BRAO and is followed by progressive thinning to 63 μm (K). Following BRAO VF demonstrate persistent superior and temporal defects (F,I,L).