Stroke in the eye!

Central Retinal Artery Occlusion (CRAO) is an ophthalmic emergency where patients present with sudden, severe and painless unilateral loss of vision.


The central retinal artery - first branch of the ophthalmic artery - supplies the inner 6 layers of the retina.


Occlusion of the lumen of the artery by an embolus, thrombus or inflammatory/ traumatic vessel wall damage or spasm results in ischemic whitening of the retina.





The classic findings in acute stage include:


Whitening of the retina due to ischemia of the inner retina which leads to opacification of nerve fibre layer and retinal edema


Cherry red spot at macula (due to underlying choroidal circulation supplying the outer retina) (1)

Retinal blood vessels show segmental blood flow known as box carring/ cattle trucking (2)


There may be a visible embolus within the retinal blood vessels- cholesterol plaque (Hollenhorst), gray-white platelet plaque, or white calcium plaque (3)


Arteriolar attenuation


A relative afferent pupillary defect


Causes: Nonarteritic (Ipsilateral carotid artery atherosclerosis being the most common cause, cardiogenic embolism, hypercoagulable states, etc)

Arteritic (Giant cell arteritis being the most common cause and other vasculitic diseases)


There has been no conclusive evidence to support the variety of treatments for CRAO. Immediate referral for stroke evaluation is necessary in order to minimize risk of secondary ischemic events.


Important differential diagnosis of Cherry Red Spot (1):

Metabolic Storage Diseases:

Tay–Sachs disease

Farber disease

GM1 and GM2 gangliosidoses

Metachromatic leukodystrophy

Niemann–Pick disease

Sandhoff disease

Sialidosis

Vascular: Central Retinal Artery Occlusion

Drugs:

Quinine toxicity

Dapsone toxicity

Poisoning:

Carbon monoxide

Methanol

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