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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- CRAO presents as sudden painless severe monocular vision loss — an eye stroke and medical emergency
- Classic fundus: pale retina with cherry-red spot at the fovea; embolus may be visible
- Most common mechanism: embolus from carotid atherosclerosis or cardiac source
- Immediate stroke-center evaluation is required; assess for concurrent cerebral ischemia and vascular risk
- In patients >50 with headache, jaw claudication, or scalp tenderness, treat possible giant cell arteritis immediately with high-dose steroids
Overview
Central retinal artery occlusion (CRAO) is acute ischemia of the inner retina from obstruction of the central retinal artery. It is analogous to an ischemic stroke and carries high risk of concurrent or subsequent cerebral and cardiovascular events. Retinal ischemic tolerance is limited, so visual prognosis is often poor. Traditional ocular maneuvers have limited evidence; the high-yield clinical action is urgent diagnosis, exclusion of arteritic causes, and rapid stroke evaluation.
Epidemiology
CRAO is uncommon but disproportionately affects older adults with vascular risk factors. Risk factors include carotid artery disease, atrial fibrillation, valvular disease, recent cardiac procedures, hypertension, diabetes, hyperlipidemia, smoking, hypercoagulable states, vasculitis, and giant cell arteritis. In younger patients, consider embolic heart disease, thrombophilia, migraine/vasospasm, trauma, and inflammatory causes.
Clinical Features
Symptoms
Sudden painless monocular vision loss, often profound
May describe a curtain or blackout, but without flashes/floaters typical of retinal detachment
Transient preceding episodes of amaurosis fugax suggest carotid embolic disease
Headache, scalp tenderness, jaw claudication, polymyalgia symptoms, or fever suggest giant cell arteritis
No eye pain unless another process is present
Signs
Severely reduced visual acuity; counting fingers, hand motion, or light perception
Relative afferent pupillary defect
Retinal whitening with cherry-red spot at the fovea
Retinal arterial attenuation, boxcarring, or visible embolus (Hollenhorst plaque)
Optic disc pallor develops later; acute disc edema suggests arteritic disease or ophthalmic artery involvement
Investigations
First-line
Dilated fundus examinationRetinal whitening, cherry-red spot, arterial narrowing, embolus, or ophthalmic artery occlusion signs
ESR, CRP, and platelet countImmediately in patients >50 or with systemic symptoms to evaluate giant cell arteritis; do not wait for biopsy before steroids if suspected
Stroke evaluationUrgent ED/stroke-center workup: neurologic exam, brain imaging when indicated, ECG/telemetry, carotid imaging, and cardiac evaluation
Second-line
OCTShows inner retinal hyperreflectivity and edema acutely; later retinal thinning
Fluorescein angiographyDelayed arterial filling and prolonged arteriovenous transit time; not required before emergency stroke evaluation
Carotid duplex / CTA / MRAIdentifies ipsilateral carotid stenosis or plaque source
Specialist
Temporal artery biopsy or ultrasoundIf GCA suspected; arrange after steroids are started because vision in the other eye is at risk
Hypercoagulable and inflammatory evaluationConsider in younger patients or without typical vascular risk factors
1
Immediate emergency actions
- Treat as acute ischemic stroke: urgent transfer to ED/stroke center for time-sensitive evaluation
- Check exact time last known well; assess eligibility for acute stroke pathways where available
- Do not reassure or schedule routine ophthalmology follow-up for sudden painless monocular vision loss
- Control vascular risk factors and initiate secondary prevention after hemorrhage and contraindications are assessed
2
Exclude giant cell arteritis
- If age >50 with headache, jaw claudication, scalp tenderness, polymyalgia rheumatica symptoms, fever, or high inflammatory markers: give immediate high-dose corticosteroids
- Typical regimen: IV methylprednisolone for visual symptoms or high-risk disease, followed by high-dose oral prednisone with rheumatology/ophthalmology input
- Temporal artery biopsy should not delay treatment
3
Ocular measures
- Anterior chamber paracentesis, ocular massage, IOP-lowering drops, carbogen, and hyperbaric oxygen have limited evidence and should not delay stroke evaluation
- Manage neovascular complications with retina follow-up, anti-VEGF, and panretinal photocoagulation if needed
4
Secondary prevention
- Carotid disease management, antiplatelet therapy, statin therapy, BP and diabetes control, smoking cessation
- Evaluate for atrial fibrillation and cardioembolic sources; anticoagulate if indicated
- Educate that fellow-eye and stroke risk require urgent systemic follow-up
Complications
- Permanent severe vision loss: Common because retinal ischemia is rapidly injurious
- Neovascularization: Iris or angle neovascularization can cause neovascular glaucoma
- Stroke/TIA: CRAO is a marker of systemic embolic disease and future vascular events
- Fellow-eye blindness: Major risk in untreated giant cell arteritis
- Optic atrophy: Late sequela of retinal/optic nerve ischemia
USMLE Step 2 CK Exam Tips
- 1Sudden painless monocular vision loss + cherry-red spot = central retinal artery occlusion
- 2CRAO is an ocular stroke — next best step is emergent stroke evaluation, not outpatient ophthalmology
- 3Cherry-red spot can also occur in Tay-Sachs, but in an older adult with acute vision loss it is CRAO
- 4CRAO is pale retina; CRVO is blood-and-thunder retina
- 5Always consider giant cell arteritis in patients >50; give steroids immediately if suspected before biopsy
- 6Amaurosis fugax before CRAO suggests carotid emboli
- 7Relative afferent pupillary defect is common in severe unilateral retinal or optic nerve disease
- 8Traditional ocular massage is not the high-yield answer if stroke-center transfer is available
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