Central retinal arterial occlusion
Overview
Central retinal artery occlusion (CRAO) - acute occlusion of the central retinal artery causing sudden, severe, painless monocular vision loss. The ocular equivalent of ischaemic stroke.
Aetiology
•Atherosclerotic thrombosis - most common (~80%); local plaque in CRA; associated with hypertension, diabetes
•Embolism - carotid (cholesterol/fibrinoplatelet plaques), cardiac (AF, valvular disease, mural thrombus)
•GCA (vasculitis) - must be excluded in all patients >50 years
•Thrombophilia - consider in younger patients (antiphospholipid syndrome, protein C/S deficiency)
•Pharmacological - oral contraceptive pill, cocaine
Presentation
•Sudden painless monocular vision loss - onset over seconds; reduced to counting fingers or worse in ~94%
•Amaurosis fugax - transient monocular visual loss preceding CRAO in up to 10%; TIA-equivalent warning sign from carotid/cardiac source
•Relative afferent pupillary defect (RAPD) - swinging torch test; ischaemic retina transmits weaker afferent signal
•Pale retina with cherry red spot - defining fundoscopic appearance; pale oedematous inner retina (lost CRA supply) with preserved fovea (thin, supplied by choroid) appearing bright red
•Boxcarring (segmentation) of blood in retinal arterioles - sign of very low/absent retinal blood flow
•Attenuated retinal arterioles - narrow, thread-like appearance
Investigations
🥇 First-line
•Fundoscopy - pale retina, cherry red spot, attenuated arterioles, Hollenhorst plaques at bifurcations
•Exclude GCA urgently: ESR, CRP, platelets (ESR typically >50 mm/hr in GCA)
•ECG - identify AF as cardioembolic source
•Carotid Doppler ultrasound - identify carotid stenosis as embolic source
•Fluorescein angiography - gold standard; demonstrates delayed/absent retinal arterial filling
•Echocardiogram - structural cardiac sources (mural thrombus, valvular disease)
•Thrombophilia screen - in younger patients or no conventional risk factors
Management
•Irreversible retinal damage within ~90-100 minutes - treat with same urgency as acute ischaemic stroke
🥇 First-line
•Immediate ophthalmology referral - same-day emergency
•Ocular massage - firm intermittent digital pressure on closed eyelid 10-15 seconds, repeated; aims to dislodge embolus distally and lower IOP
•Anterior chamber paracentesis - removal of aqueous humour to acutely reduce IOP; performed by ophthalmologist
•IOP-lowering agents - acetazolamide IV, topical timolol; improve arterial perfusion pressure
•Exclude and treat GCA immediately - if suspected, start high-dose prednisolone orally (or IV methylprednisolone if vision at risk) before temporal artery biopsy
•Long-term secondary prevention - manage as TIA/stroke equivalent: antiplatelet therapy (or anticoagulation if AF), statin, hypertension management, referral to TIA/stroke service
Complications
•Permanent severe visual impairment - most common outcome; most patients do not regain useful vision
•Ischaemic stroke - significantly elevated risk in weeks/months following CRAO
•Neovascular glaucoma - weeks to months later; retinal ischaemia drives VEGF release causing rubeosis iridis (iris neovascularisation)
•Optic atrophy - chronic phase; optic disc becomes pale as ischaemic ganglion cells die
Key differentials - fundoscopy findings
Differential diagnosis of sudden painless visual loss - fundoscopy findings
| Condition | Key fundoscopy findings |
|---|---|
| CRAO | Pale retina + cherry red spot, attenuated arterioles |
| Anterior ischaemic optic neuropathy (GCA) | Engorged pale optic disc with blurred margins |
| Central retinal vein occlusion | Widespread flame haemorrhages, disc swelling, tortuous veins |
| Diabetic retinopathy (proliferative) | Cotton wool spots, hard exudates, blot haemorrhages, neovascularisation |
| Papilloedema | Elevated optic disc, blurred margins, no pallor |
| Macular degeneration | Drusen + pigmentary changes at macula |