Summary

Retinal artery occlusion is an ophthalmic emergency requiring immediate assessment and transfer to a stroke centre. Ischaemia to the retina often causes severe visual loss, which may be irreversible if retinal circulation is not rapidly re-established. The majority of cases are caused by atherosclerosis-related thrombosis and embolism.

Background

Any vessels supplying the eye may become occluded. The central retinal artery is the first branch of the main artery supplying the eye: the ophthalmic artery. After entering the eye, the central retinal artery branches into superior and inferior vessels that supply nerve fibres in the inner retina as well as the optic nerve.

Another branch of the ophthalmic artery is the posterior ciliary arteries, which give rise to the cilio-retinal artery. The ciliary arteries supply the outer retina.

Blood flow through any of these vessels may become obstructed, producing a retinal artery occlusion. The causes of retinal artery occlusion are:

• Embolism - embolism and thrombus are the main causes. Emboli most commonly originate from atherosclerotic plaques in the carotid artery; the ophthalmic artery is the first branch of the internal carotid artery, so emboli can easily travel into the eye. Emboli can also travel to the eye from the heart, in conditions such as arrhythmia (e.g. atrial fibrillation), mitral valve prolapse and bacterial endocarditis.
• Thrombus - 1/3 of young patients have a thrombophilic disorder (e.g. antiphospholipid syndrome, hyperhomocystinaemia)
• Inflammatory vessel wall damage (e.g. giant cell arteritis (GCA), systemic lupus erythematous, granulomatosis with polyangiitis, polyarteritis nodosa)
• Traumatic vessel wall damage
• Vasospasm (e.g. migraine)
• Systemic hypotension

Risk factors

The risk factors for retinal artery occlusion are similar to those for ischaemic stroke:

• Age
• Male gender
• Smoking
• Hypertension
• Hyperlipidaemia