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Central Retinal Artery Occlusion (CRAO)

Definition

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  • The innermost retina (that is, the layers of the retina closest to the vitreous) is supplied by the central retinal artery

  • When this artery becomes blocked, the retina becomes ischaemic, which can lead to irreversible, severe vision loss

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Causes

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  • Occlusion of the central retinal artery can occur via 3 main mechanisms:

  1. Embolism

    • atherosclerotic disease of the internal carotid artery can throw off a clot​

    • this can pass via the ophthalmic artery, the first branch of the ICA

    • from here the clot can travel to and occlude the CRA

    • other causes: atrial fibrillation, mitral valve disease, bacterial endocarditis

  2. Thrombus

    • caused by thrombophilic (clot-forming) conditions: antiphospholipid syndrome, hyperhomocystinaemia, factor V Ledien​

  3. Vessel wall inflammation

    • ​Can be a presenting feature of giant cell arteritis – always test inflammatory markers for these patients

      • suspicion should be particularly high in patients >50y​

    • Other causes incldue systemic lupus erythematosus (SLE), granulomatosis with polyangiitis (GPA), and other vasculitides

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Risk factors

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  • Atherosclerotic risk factors (risk for embolism)

    • hypertension, diabetes, hypercholesterolaemia, smoking​

  • Other causes of emboli: arrhythmias, infective endocarditis, other valve disease

  • Underlying thrombophilic conditions

  • Inflammatory conditions - GCA, SLE, GPA

  • Infective causes - e.g. syphilis

  • Drugs - COCP, cocaine

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Presentation

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  • Sudden onset, painless loss of vision

    • visual loss is usually profound​

    • the exception is GCA when headache / jaw claudication / scalp tenderness may accompany loss of vision​

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Examination findings

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  • The retina becomes pale / white due to ischaemia, with a central "cherry red" spot

  • Cherry red area of macula = early sign of central retinal artery occlusion

    • Disappears soon after onset as retina tends to reperfuse and loses whitish colour

    • Even re-perfusion occurs, there is often no recovery in retinal function, resulting in profound blindness​

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Investigations

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  • Retinal imaging: FFA, OCT

  • Assess pulse (assess for arrhythmia) & perform ECG

  • Auscultate for cardiac / carotid murmur

  • Measure blood pressure

  • Blood tests including CRP / ESR to assess for GCA

  • Carotid doppler scan - to assess for atherosclerotic plaque

  • Select patients: thrombophilia screen, autoantibody blood tests

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Management

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  • Urgent referral to stroke specialist team

    • may require antiplatelet therapy / anticoagulation / carotid enderarterectomy​

  • If patients present within 24 hours, there are methods which may theoretically dislodge an embolus and restore bloodflow to the retina: 

    • ocular massage​

    • "rebreathing" into a paper bag - to increase inhaled CO2

    • IV acetazolamide

    • anterior chamber paracentesis - removal of some aqueous from the anterior chamber using a needle

      • however, studies show that there is a limited benefit from all of the above methods ​

  • Manage risk factors - hypertension, diabetes, hypercholesterolaemia, smoking​

  • Referral for low vision aids and social support for living with significant vision impairment

  • Follow up in eye clinic to assess for complications

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References

  • Denniston, A. K. O. and Murray, P. I. (eds) (2018) Oxford handbook of ophthalmology. 4th edn. London, England: Oxford University Press (Oxford Medical Handbooks). doi: 10.1093/med/9780198804550.001.0001.

  • Salmon, J. F. (2019) Kanski’s clinical ophthalmology. 9th edn. London, England: Elsevier Health Sciences.

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