4. Painless Vision Loss

Central Retinal Artery Occlusion (CRAO)

The central retinal artery (CRA) is a branch of the ophthalmic artery that travels within the optic nerve to supply blood to the retina. Occlusion of the central retinal artery is an ophthalmic emergency as the remaining posterior ciliary artery cannot sufficiently supply the retina’s needs. Emergent Opthalmology consult must be placed and hyperbaric oxygen therapy may be required.

Central Retinal Artery Occlusion Illustration
Central Retinal Artery
CRAO Illustration with only Venous Flow

CRAO commonly occurs from carotid artery atherosclerosis and plaque embolism. Some contributing risk factors for include diabetes, hypertension, cardiovascular disease, and hyperlipidemia (Varma et al).

Patients with CRAO usually have sudden, painless monocular vision loss. If you suspect CRAO, it is important to measure the blood pressure as there is a strong relationship between CRAO and hypertension (Varma et al). Another important area to assess is the radial pulse rate and rhythm. Atrial fibrillation has a high risk for embolisms and can be detected as an irregularly irregular pulse.

Central Retinal Artery Occlusion (CRAO) Ultrasound Findings

CRAO is a rare finding and requires color Doppler mode to diagnose with ocular ultrasound. On the ocular ultrasound exam, you will find diminished or absent flow of the central retinal artery (see below). You may also only see flow from the central retinal vein (blue on color Doppler) with absent central retinal arterial flow (red on color Doppler)

(Editor’s Note: In some circumstances, you may also still see some arterial flow on color Doppler from the posterior ciliary artery, even though the central retinal artery is occluded)

Normal Central Retinal Artery Flow Ocular Ultasound
Normal Flow of Central Retinal Artery and Vein
Ocular Ultrasound - Central Retinal Artery Occlusion
Central Retinal Artery Occlusion with only Venous Flow

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