Central retinal artery occlusion (CRAO) is a cause of inner retinal infarction and profound, monocular vision loss, most commonly caused by embolic occlusion of the central retinal artery.
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Epidemiology
The most common etiological associations with occlusion of the central retinal artery include:
carotid emboli
cardiac emboli
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vasculitis
Clinical presentation
Characteristically presents with a painless, sudden onset, monocular loss of vision, which is often complete; patients often report a recent history of amaurosis fugax 4. In a small percentage of patients the pathology is bilateral i.e. both retinal arteries are occluded simultaneously 5. Ophthalmoscopic examination classically reveals a "cherry red" macula surrounded by a pale retina, the former finding due to the visibility of the choroidal vasculature through the delicate macula densa.
Radiographic features
Ultrasound
Spectral and color flow Doppler allow non-invasive examination of the retinal vasculature. Color flow Doppler is used to identify the location of the retrobulbar vessels, with subsequent pulsed wave Doppler interrogation of each flow signal. Arterial flow appears distinct from venous flow, with the following characteristics observed when interrogating the central retinal artery, distinguishing it from the adjacent central retinal vein:
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more exaggerated phasicity
pulsatile appearance of the spectral Doppler waveform
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higher peak systolic velocity (PSV) 2
between 4.6 and 18.6 cm/second
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higher resistive index (RI)
between 56.0 and 89.0
calculated by taking the product of PSV and the difference between PSV and end-diastolic velocity (EDV)
The absence of arterial flow is consistent with central retinal artery occlusion in a suggestive clinical context. The presence of hyperechoic retrobulbar material may also be indicative of emboli occlusion when present 1.
MRI
Standard DWI shows diffusion restriction in the retina in about 75% of cases 6.
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