Key Facts

CRAO is effectively a retinal stroke. The priority is to identify the cause, exclude GCA, and assess/reduce future vascular risk.

Epidemiology

• Incidence: approximately 1-2 per 100,000/year
• Mean age: 60-65
• Male > female
• 25% of CRAO patients have a stroke or MI within 5 years

Aetiology

• Embolism (most common): carotid atherosclerosis, cardiac source (AF, endocarditis, mural thrombus)
• Thrombosis in situ: atherosclerosis of retinal artery
• Giant cell arteritis (5-10% of CRAO): arteritis of ophthalmic/ciliary arteries; medical emergency
• Other: vasculitis, hypercoagulable states, sickle cell, dissection
• BRAO: almost always embolic (cholesterol, platelet-fibrin, calcific emboli)

Pathophysiology

• CRA supplies inner 2/3 of retina; outer 1/3 supplied by choroid
• Occlusion of CRA → complete inner retinal ischaemia → retinal oedema (pallor) → photoreceptor death within ~90 minutes
• Cherry red spot: fovea appears red because it is supplied by choroidal circulation (normal colour against pale ischaemic surrounding retina)
• Cilioretinal artery (present in 30%): branch from ciliary circulation; may preserve central macular perfusion → better visual prognosis

CRAO

• Sudden, painless, profound monocular visual loss (counting fingers or worse)
• Usually unilateral
• Vision may fluctuate initially (if incomplete occlusion)

Signs

• Pale, oedematous retina with cherry red spot at macula
• RAPD (relative afferent pupillary defect)
• Attenuated arterioles ("box-carring" — segmentation of blood column)
• Visible embolus (Hollenhorst plaque — refractile cholesterol crystal at bifurcation)
• Optic disc pallor (develops later)

BRAO

• Sector visual field loss (corresponding to occluded branch)
• Pallor in affected sector of retina
• Visible embolus at arteriolar bifurcation
• Better visual prognosis than CRAO

Red Flags

• Age >50: always exclude GCA (headache, jaw claudication, scalp tenderness, PMR symptoms, raised ESR/CRP)
• Amaurosis fugax (transient monocular visual loss): warning sign of impending CRAO or stroke
• Young patient: investigate for thrombophilia, vasculitis

Bedside

• Visual acuity (usually severely reduced in CRAO)
• RAPD testing (positive)
• Dilated fundoscopy (cherry red spot, pale retina, attenuated arterioles)
• Blood pressure
• Pulse (irregular — AF)

Bloods — URGENT

• ESR and CRP (must exclude GCA in >50; ESR >50mm/hr highly suggestive)
• FBC (polycythaemia, thrombocytosis)
• Glucose, HbA1c, lipid profile
• Clotting, thrombophilia screen (if <50)
• Blood cultures (if endocarditis suspected)

Imaging

• Carotid duplex ultrasound: carotid stenosis assessment
• Echocardiography: cardiac source of emboli (TTE/TOE)
• ECG: atrial fibrillation
• CT/MRI brain: if stroke symptoms
• FFA: confirms diagnosis (delayed arterial filling, "pruned tree" appearance)
• OCT: retinal oedema, inner retinal thickening

Special Tests

• Temporal artery biopsy: if GCA suspected (within 2 weeks of starting steroids; do not delay steroids for biopsy)
• 24-hour ECG (Holter): paroxysmal AF

Emergency

• Exclude GCA: if >50 and clinical suspicion → start prednisolone 60-80mg OD immediately (do not wait for biopsy) + PPI
• No proven effective acute treatment for non-arteritic CRAO (window for intervention is ~90 minutes; most present later)
• Attempted treatments (limited evidence): ocular massage, anterior chamber paracentesis (reduces IOP to dislodge embolus), intraarterial thrombolysis (research only; EAGLE study showed no benefit), hyperbaric oxygen

Non-pharmacological

• Stroke pathway referral: CRAO is a stroke equivalent; high short-term risk of cerebral stroke and MI
• Cardiovascular risk factor management: BP control, smoking cessation, statin, antiplatelet
• Carotid endarterectomy: if significant ipsilateral carotid stenosis (>70% symptomatic)

Pharmacological

• Antiplatelet: aspirin 75mg OD (unless anticoagulation indicated)
• Statin: atorvastatin 80mg OD
• Anticoagulation: if AF identified (DOAC or warfarin)
• GCA treatment: prednisolone 60-80mg OD → slow taper over 1-2 years; consider tocilizumab (NICE TA518 — GiACTA trial)

Surgical/Interventional

• Carotid endarterectomy: if ipsilateral carotid stenosis >70% (symptomatic)
• PFO closure: if paradoxical embolism suspected in young patients

Referral Criteria

• CRAO: emergency ophthalmology + acute stroke pathway
• Suspected GCA: immediate high-dose steroids + urgent temporal artery biopsy
• Amaurosis fugax: urgent TIA clinic/vascular assessment
• Young patient: haematology/rheumatology for thrombophilia/vasculitis screen

• CRAO visual prognosis: poor; only 10-20% recover useful vision
• Cilioretinal artery sparing: better outcome (may retain some central vision)
• BRAO: better prognosis; majority recover to 6/12 or better
• GCA-related CRAO: irreversible if not treated rapidly; 50% risk of fellow eye involvement without steroids
• Cardiovascular risk: 25% risk of stroke or MI within 5 years after CRAO
• Amaurosis fugax: 10-15% risk of stroke within 3 months without treatment

CRAO vs CRVO Comparison

Types of Retinal Emboli