Central Retinal Artery Occlusion

Topic Overview

Summary

Central retinal artery occlusion (CRAO) is an acute interruption of blood flow through the central retinal artery, causing sudden, painless, profound monocular vision loss. [1] It represents an ocular stroke and is an ophthalmic emergency. The retina tolerates ischaemia for approximately 90-110 minutes before irreversible photoreceptor damage occurs. [2] The classic fundoscopic finding is a "cherry-red spot" at the macula, representing preserved choroidal perfusion contrasting with pale ischaemic retina. CRAO is predominantly caused by embolism (carotid atherosclerosis, cardiac sources) or arteritic inflammation (giant cell arteritis). [3] Beyond immediate vision loss, CRAO serves as a marker for systemic vascular disease with a 25% risk of stroke within 3 months and 30% cumulative cardiovascular event rate within 3 years. [4] Management focuses on emergent treatment within the therapeutic window, exclusion of giant cell arteritis (GCA), and aggressive secondary stroke prevention.

Key Facts

• Incidence: 1-2 per 100,000/year, increasing with age [5]
• Presentation: Sudden painless monocular vision loss (typically count fingers or worse)
• Critical time window: 90-110 minutes for irreversible retinal damage [2]
• Fundoscopy: Pale oedematous retina + cherry-red spot at fovea + attenuated arteries
• Aetiology: Embolic (70-80%), arteritic GCA (1-2%), hypercoagulable (less than 5%) [3]
• Stroke risk: 25% within 3 months; same vascular risk profile as cerebral stroke [4]
• Visual prognosis: Poor — only 20-30% achieve meaningful visual recovery [6]
• Action: Urgent ophthalmology + exclude GCA + stroke pathway + consider thrombolysis if less than 4.5-6h

Clinical Pearls

Treat CRAO as an ocular stroke — activate stroke pathway, consider IV thrombolysis within 4.5h

Always exclude GCA in patients > 50 years: check ESR/CRP/platelets; start steroids immediately if suspected

Cherry-red spot = intact choroidal circulation at fovea vs pale ischaemic inner retina (supplied by CRA)

Presence of cilioretinal artery (15-30% of patients) may spare central vision and improve prognosis

RAPD is always present in CRAO (unless bilateral or previous severe contralateral disease)

Why This Matters Clinically

CRAO represents a dual emergency: immediate catastrophic vision loss and a harbinger of life-threatening cardiovascular events. Despite the narrow therapeutic window, emerging evidence supports intravenous thrombolysis for selected patients presenting within 4.5 hours. [7,8] More critically, CRAO patients face a 3-fold increased risk of stroke compared to age-matched controls, mandating urgent cardiovascular workup identical to cerebral stroke. [4] Early recognition and management can prevent the second eye from being affected in arteritic cases and reduce systemic vascular morbidity and mortality.

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Visual Summary

Visual assets to be added:

• Fundus photograph: Classic cherry-red spot with pale retina
• Retinal artery anatomy and blood supply diagram
• CRAO vs BRAO vs cilioretinal sparing comparison
• Management algorithm: Emergency treatment within 4.5-6h window
• Fluorescein angiography: Delayed arterial filling
• OCT: Inner retinal layer hyperreflectivity and oedema
• Cardiovascular workup flowchart

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Epidemiology

Incidence and Prevalence

Central retinal artery occlusion is a rare but devastating condition affecting 1-2 per 100,000 people annually. [5] The incidence increases exponentially with age, with most cases occurring in the 6th-7th decades of life (mean age 60-65 years). [1] Branch retinal artery occlusion (BRAO) is approximately 4 times more common than CRAO. [5]

Population-based studies demonstrate male predominance (male:female ratio approximately 2:1), though this may reflect higher prevalence of cardiovascular risk factors in men. [5] The condition is more common in Caucasian populations compared to Asian or African populations, mirroring patterns seen in atherosclerotic cerebrovascular disease. [9]

Recent epidemiological data (2020-2024) suggest the incidence may be increasing, potentially due to improved recognition, better imaging capabilities, and aging populations with multiple cardiovascular comorbidities. [9]

Risk Factors

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Pathophysiology

Vascular Anatomy

The central retinal artery (CRA) is the first branch of the ophthalmic artery and provides blood supply to the inner retinal layers (nerve fibre layer, ganglion cell layer, inner plexiform layer, inner nuclear layer). [13] It enters the optic nerve 10-15 mm behind the globe and courses through the centre of the optic nerve before emerging at the optic disc.

The outer retinal layers (photoreceptors, outer plexiform layer, outer nuclear layer) are supplied by the choriocapillaris from the posterior ciliary arteries, which explains the preservation of the foveal red reflex (cherry-red spot) in CRAO. [13]

Approximately 15-30% of individuals have a cilioretinal artery, which arises directly from the choroidal circulation and supplies the macula. [14] Presence of a cilioretinal artery can preserve central vision even in complete CRAO, significantly improving visual prognosis.

Mechanisms of Occlusion

1. Embolic (70-80% of cases) [3]

Carotid artery embolism accounts for 40-50% of CRAO cases. Atherosclerotic plaques at the carotid bifurcation release cholesterol emboli (Hollenhorst plaques), platelet-fibrin emboli, or calcific emboli. These lodge at the lamina cribrosa where the CRA enters the eye.

Cardiac embolism (20-25% of cases) arises from:

• Atrial fibrillation (thrombus in left atrial appendage)
• Valvular disease (mitral stenosis, prosthetic valves, endocarditis)
• Recent myocardial infarction with left ventricular thrombus
• Cardiac tumours (atrial myxoma)
• Patent foramen ovale with paradoxical embolism [11]

Visible emboli are identified on fundoscopy in approximately 20-40% of patients (Hollenhorst plaques—refractile cholesterol; platelet-fibrin emboli appear greyish-white). [3]

2. Thrombotic (10-20% of cases)

In situ thrombosis occurs at sites of pre-existing atherosclerotic stenosis of the CRA, typically at the lamina cribrosa. This mechanism is more common in patients with systemic atherosclerotic risk factors (hypertension, diabetes, hyperlipidaemia). [3]

3. Arteritic (1-2% of cases) [10]

Giant cell arteritis (GCA) causes granulomatous inflammation of medium and large arteries, affecting the posterior ciliary arteries and occasionally the CRA. Arteritic CRAO is often associated with concurrent anterior ischaemic optic neuropathy (AION). GCA is a critical diagnosis because:

• It is eminently treatable with high-dose corticosteroids
• Untreated GCA causes bilateral blindness in 25-50% within days to weeks
• Systemic complications include aortic aneurysm and cerebrovascular events

Features suggestive of arteritic CRAO include:

• Age > 50 years (mean age 70 years)
• Systemic symptoms: headache, jaw claudication, scalp tenderness, polymyalgia rheumatica
• Markedly elevated inflammatory markers (ESR often > 50 mm/hr)
• Poor or absent response to acute CRAO therapies
• Presence of concurrent AION or bilateral involvement

4. Hypercoagulable States (less than 5% of cases) [11]

Thrombophilias should be considered in younger patients (less than 50 years) without traditional vascular risk factors:

• Inherited: Factor V Leiden, prothrombin G20210A mutation, protein C/S deficiency, antithrombin III deficiency
• Acquired: Antiphospholipid syndrome, hyperhomocysteinaemia
• Haematological: Polycythaemia vera, essential thrombocythaemia, sickle cell disease

5. Vasospasm (Rare)

Retinal artery vasospasm may occur in:

• Migraine (retinal migraine)
• Cocaine or amphetamine use
• Raynaud's phenomenon
• Post-orbital or retrobulbar anaesthesia

Cherry-Red Spot: The Pathognomonic Sign

The cherry-red spot at the macula is caused by:

1. Pale ischaemic retina: Acute oedema of the inner retinal layers supplied by the CRA, causing whitening
2. Preserved foveal vasculature: The foveal centre (foveola) is avascular and relies on choroidal blood supply (via posterior ciliary arteries), which remains intact
3. Contrast effect: The thin, transparent foveola allows the underlying red choroidal vasculature to show through, contrasting sharply with the surrounding pale retina

The cherry-red spot is not specific to CRAO and can be seen in other causes of inner retinal ischaemia or storage diseases (Tay-Sachs, Niemann-Pick, sialidosis).

Time-Critical Ischaemic Tolerance

Retinal ischaemic tolerance is approximately 90-110 minutes. [2] Experimental and clinical studies demonstrate:

• less than 90 minutes: Potential for near-complete recovery if reperfusion achieved
• 90-240 minutes: Partial recovery possible; degree depends on duration of ischaemia
• > 240 minutes (4 hours): Irreversible inner retinal damage; minimal chance of recovery

This narrow therapeutic window makes CRAO a true ophthalmic emergency, analogous to acute ischaemic stroke ("time is retina").

Retinal Changes Over Time

Acute phase (0-24 hours):

• Inner retinal oedema causing retinal whitening
• Cherry-red spot at fovea
• Attenuated retinal arteries (may be normal acutely)
• Segmentation of blood column ("box-carring" or "cattle-trucking")
• Visible embolus (in 20-40%)

Subacute phase (1-6 weeks):

• Progressive retinal oedema resolution
• Attenuation and arterial sheathing develop
• Optic disc pallor (often sectoral)
• Cherry-red spot fades as oedema resolves

Chronic phase (> 6 weeks):

• Optic atrophy (pale disc)
• Attenuated, sclerotic retinal arteries
• Retinal thinning on OCT (especially ganglion cell layer)
• Potential development of neovascularisation (rubeosis iridis, neovascular glaucoma) in 10-20% of cases if extensive retinal ischaemia

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Clinical Presentation

Symptoms

Cardinal Symptom: Sudden Painless Monocular Vision Loss

Patients report sudden, painless, profound vision loss in one eye, typically described as:

• "Like a curtain coming down"
• "Sudden blackout"
• Complete loss of vision or severely reduced to counting fingers/hand movements

Vision loss is maximal at onset (within seconds to minutes). [1]

Preceding Transient Visual Loss (Amaurosis Fugax)

Approximately 10-15% of patients report episodes of transient monocular vision loss (amaurosis fugax) in the days to weeks before CRAO, reflecting transient embolic showers or hypoperfusion. [15] This is an important warning sign and should prompt urgent investigation.

Associated Symptoms

Patients should be specifically asked about symptoms suggestive of giant cell arteritis:

• New-onset headache (often temporal)
• Scalp tenderness (pain when brushing hair)
• Jaw claudication (pain with chewing)
• Systemic symptoms: fever, weight loss, malaise, night sweats
• Polymyalgia rheumatica symptoms (shoulder and hip girdle pain and stiffness)

Symptoms of cerebrovascular or cardiovascular disease:

• Recent stroke or TIA
• Chest pain, palpitations (cardiac source)
• Limb claudication (peripheral vascular disease)

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Clinical Examination

Visual Acuity

Visual acuity is typically severely reduced:

• Counting fingers (CF) or hand movements (HM): 60-70% of patients [6]
• Light perception (LP) only: 10-20%
• No light perception (NLP): Rare, suggests concurrent ophthalmic artery occlusion

Better presenting visual acuity (≥6/60) is associated with:

• Presence of cilioretinal artery sparing the macula [14]
• Branch retinal artery occlusion (BRAO) rather than complete CRAO
• Partial or transient occlusion with spontaneous reperfusion

Pupillary Examination

Relative afferent pupillary defect (RAPD) is present in almost all cases of CRAO, reflecting significant optic nerve dysfunction from inner retinal ischaemia. [1] The RAPD is:

• Always present unless:
  • Bilateral CRAO (very rare)
  • Previous severe contralateral disease
• Proportional to the extent of retinal ischaemia
• Absent or mild in BRAO (depending on area affected)

Fundoscopy: The Diagnostic Cornerstone

Classic Findings in CRAO

1. Cherry-red spot at the fovea: Pathognomonic finding (present in 90% of cases within first 24 hours) [1]
2. Pale, oedematous retina: Diffuse retinal whitening due to inner retinal oedema, most prominent in the posterior pole
3. Attenuated retinal arterioles: Narrowed arteries (may be normal in hyperacute phase)
4. Box-carring (cattle-trucking): Segmentation of blood column within retinal arterioles
5. Optic disc: Normal acutely; may develop pallor over 4-6 weeks

Visible Emboli (20-40% of cases) [3]

• Hollenhorst plaques: Refractile yellow-orange cholesterol emboli (from carotid atheromatous plaques)
• Platelet-fibrin emboli: Greyish-white, less refractile
• Calcific emboli: White, often at bifurcations (from cardiac valves)

Variants

CRAO with cilioretinal artery sparing:

• Island of preserved retinal perfusion around macula
• Cherry-red spot may be absent
• Better visual prognosis (50-60% achieve ≥6/60) [14]

Branch retinal artery occlusion (BRAO):

• Sectoral retinal whitening (typically superotemporal quadrant)
• Visual field defect corresponding to affected area
• Better prognosis than CRAO

Combined CRAO and CRVO (rare):

• Retinal whitening + retinal haemorrhages
• Usually indicates ophthalmic artery occlusion or severe ocular ischaemic syndrome
• Very poor prognosis

Cardiovascular Examination

A thorough cardiovascular examination is mandatory:

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Investigations

Immediate Bedside Investigations

1. Fundoscopy (Dilated)

Essential for diagnosis. Perform dilated fundoscopy urgently to identify:

• Cherry-red spot
• Retinal pallor and oedema
• Attenuated arteries
• Visible emboli
• Optic disc appearance

2. Visual Acuity and RAPD

Document baseline visual acuity and RAPD to:

• Assess severity
• Guide prognosis
• Monitor treatment response

Urgent Laboratory Tests: Exclude GCA

In all patients aged > 50 years (or younger if clinically suspected), check:

Important notes:

• Normal ESR/CRP does not exclude GCA (10-20% have normal inflammatory markers) [10]
• If clinical suspicion for GCA is high, start corticosteroids immediately before biopsy
• Temporal artery biopsy can be performed within 2 weeks of starting steroids without affecting histology

Imaging Investigations

1. Optical Coherence Tomography (OCT)

OCT findings in acute CRAO (within 24 hours): [16]

• Increased reflectivity of inner retinal layers (NFL, GCL, IPL)
• Inner retinal thickening due to oedema
• Shadowing of outer retinal layers

OCT findings in chronic CRAO (> 4 weeks):

• Marked thinning of ganglion cell complex (GCC)
• Thinning of inner nuclear layer and inner plexiform layer
• Normal outer retinal layers (photoreceptors)

OCT angiography (OCTA): May show delayed or absent flow in retinal vasculature. [16]

Prognostic value: Degree of inner retinal thickening acutely correlates with visual outcome; greater oedema predicts worse outcomes.

2. Fluorescein Angiography (FA)

FA findings in CRAO:

• Arterial phase: Delayed or absent filling of retinal arteries
• Arteriovenous phase: Prolonged arm-to-retina circulation time (normally 10-12 seconds; > 20 seconds in CRAO)
• Venous phase: Delayed venous filling; mottled choroidal fluorescence
• Late phase: No dye leakage (unlike CRVO)

Clinical use: FA is rarely performed acutely but can be useful to:

• Confirm diagnosis when fundoscopy is equivocal
• Identify concurrent retinal ischaemia
• Guide prognosis based on extent of capillary non-perfusion

3. Carotid Doppler Ultrasound

Indications: All patients with CRAO (unless clear cardioembolic or arteritic source).

Findings:

• Degree of carotid stenosis (> 50% or > 70% thresholds)
• Plaque characteristics (ulcerated, heterogeneous)
• Vertebral artery patency

Follow-up: If significant stenosis (> 70%), consider CT angiography or MR angiography for surgical planning.

4. Electrocardiogram (ECG)

Identify:

• Atrial fibrillation
• Recent myocardial infarction
• Left ventricular hypertrophy (hypertension)

5. Echocardiography

Transthoracic echocardiography (TTE): Identify:

• Valvular disease
• Left ventricular thrombus (recent MI)
• Cardiac tumours (atrial myxoma)
• Left ventricular dysfunction

Transoesophageal echocardiography (TOE): Consider if:

• TTE is normal but high suspicion for cardiac source
• Young patient (less than 50 years) without vascular risk factors
• Suspected patent foramen ovale (PFO) with bubble study [11]

Haematological and Metabolic Workup

Neuroimaging

Indications for Brain MRI/CT

• Concurrent neurological symptoms (stroke, TIA)
• Multiple embolic events
• Suspected cerebral vasculitis
• Young patient without identified embolic source

MRI findings: May show concurrent cerebral infarcts (in 20-30% of CRAO patients), suggesting shared embolic source. [4]

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Classification & Staging

By Anatomical Extent

By Aetiology

Timing Classification (for Treatment)

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Management

Immediate Management (less than 4.5-6 Hours)

CRAO should be managed as an ocular stroke. The American Heart Association (AHA) 2020 scientific statement classified CRAO as an acute ischaemic stroke eligible for thrombolysis. [7]

1. Activate Stroke Pathway

• Alert stroke team and ophthalmology
• Transfer to stroke unit or ED with stroke protocol
• Document time of symptom onset accurately

2. Intravenous Thrombolysis (IVT)

Indications (based on emerging evidence): [7,8]

• CRAO presenting within 4.5 hours of symptom onset
• No contraindications to IV alteplase
• Severe visual loss (VA less than 6/60)
• Shared decision-making with patient (off-label use)

Dosing: IV alteplase 0.9 mg/kg (maximum 90 mg), with 10% as bolus, remainder over 60 minutes (same as cerebral stroke protocol).

Evidence:

• Cochrane 2023 systematic review: No RCT evidence supporting thrombolysis; however, observational data suggest potential benefit if given within 4.5h [1]
• Mac Grory et al. 2020 (Stroke): Individual patient-level meta-analysis showed improved visual outcomes (visual acuity improvement ≥3 lines) in 48% of IVT-treated patients vs 28% in controls (OR 2.33) [8]
• REVISION study (ongoing): Phase III RCT of IV tenecteplase for CRAO less than 4.5h (results pending)

Contraindications (standard thrombolysis contraindications):

• Active bleeding or bleeding disorder
• Recent surgery (less than 14 days)
• Recent stroke/TIA (less than 3 months)
• Severe uncontrolled hypertension (SBP > 185 mmHg, DBP > 110 mmHg)
• Platelet count less than 100 × 10⁹/L
• INR > 1.7 (if on warfarin)

Risks: Intracranial haemorrhage (0.6% in stroke trials), systemic bleeding.

Reality check: Most CRAO patients present beyond the 4.5-hour window; thrombolysis use remains off-label and controversial.

3. Intra-Arterial Thrombolysis (IAT)

Indications: CRAO within 6 hours at centres with interventional neuroradiology expertise.

Procedure: Selective catheterisation of ophthalmic artery via femoral access; local infusion of alteplase (2-10 mg) or urokinase. [17]

Evidence:

• Meta-analysis (Page et al. 2018, Front Neurol): Visual improvement in 62% of IAT-treated patients; higher complication rate than IVT (stroke, ophthalmic artery dissection) [17]
• Benefit vs risk: Limited use due to invasiveness, availability, and mixed evidence

Complications: Cerebral embolism, ophthalmic/carotid dissection, groin haematoma.

4. Conservative Acute Measures

These measures have limited evidence but are low risk and may be attempted if thrombolysis is not available or contraindicated:

a) Ocular Massage

• Rationale: Dislodge embolus downstream; improve retinal perfusion
• Technique: Firm digital pressure on closed eyelid for 5-10 seconds, then release; repeat for 5-10 minutes
• Evidence: No RCT data; case reports of benefit if performed very early (less than 90 minutes) [1]

b) Anterior Chamber Paracentesis (ACP)

• Rationale: Rapidly reduce IOP to increase ocular perfusion pressure (OPP = MAP - IOP)
• Technique: Remove 0.1-0.3 mL aqueous via 30G needle at limbus
• Evidence: Observational data show modest benefit; no RCT [1]
• Complications: Hyphaema, endophthalmitis, lens injury (rare)

c) Intraocular Pressure (IOP) Reduction

• IV acetazolamide 500 mg: Rapidly lowers IOP by 30-40% within 30 minutes [1]
• Topical IOP-lowering agents: Timolol 0.5%, apraclonidine 1%
• Rationale: Increase retinal perfusion pressure

d) Hyperbaric Oxygen Therapy (HBOT)

• Rationale: Increase dissolved oxygen in plasma to sustain ischaemic retina
• Protocol: 100% oxygen at 2-2.5 atmospheres for 90 minutes
• Evidence: Observational studies show modest benefit if started within 24 hours; no RCT [18]
• Availability: Limited; not widely accessible

e) Carbogen Inhalation (95% O₂ + 5% CO₂)

• Rationale: Increase retinal oxygenation + CO₂-induced vasodilation
• Evidence: Weak; rarely used [1]

Summary of acute treatments: Only IV thrombolysis has emerging evidence. Conservative measures are low risk but of unproven benefit.

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Urgent: Exclude Giant Cell Arteritis

Critical importance: Untreated GCA causes bilateral blindness in 25-50% of patients within days to weeks. GCA is the only treatable cause of CRAO. [10]

Step 1: Assess Clinical Probability

Red flag features:

• Age > 50 years (especially > 70)
• New-onset headache (temporal, severe)
• Scalp tenderness (pain when combing hair)
• Jaw claudication (pain with chewing)
• Polymyalgia rheumatica symptoms
• Systemic symptoms: fever, weight loss, malaise
• Concurrent anterior ischaemic optic neuropathy (AION)

Step 2: Urgent Blood Tests

• ESR and CRP: If ESR > 50 mm/hr and/or CRP > 20 mg/L, strongly suspect GCA
• FBC: Thrombocytosis (platelets > 400) and normocytic anaemia support GCA

Step 3: Immediate Corticosteroid Therapy

If GCA is suspected clinically (even with normal inflammatory markers): [10]

• IV methylprednisolone 500-1000 mg daily for 3 days, then
• Oral prednisolone 40-60 mg daily (1 mg/kg)

Start steroids immediately; do not wait for biopsy.

Step 4: Temporal Artery Biopsy (TAB)

• Arrange within 1-2 weeks of starting steroids (positive yield up to 2 weeks)
• Biopsy ≥2 cm segment (skip lesions common)
• Consider bilateral biopsy if unilateral negative but high clinical suspicion

Histology: Granulomatous inflammation with giant cells, disruption of internal elastic lamina.

Step 5: Long-Term Steroid Management

If GCA confirmed:

• Continue high-dose prednisolone (40-60 mg) for 2-4 weeks
• Gradual taper over 12-18 months guided by symptoms and ESR/CRP
• Monitor for steroid side effects (osteoporosis prophylaxis, PPI, diabetes screening)
• Consider steroid-sparing agents: methotrexate, tocilizumab (IL-6 inhibitor—NICE approved for GCA)

Visual prognosis in arteritic CRAO: Poor despite steroids; steroids prevent second eye involvement.

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Secondary Stroke Prevention (All Patients)

CRAO patients have a 25% risk of stroke within 3 months and 30% cumulative cardiovascular event rate within 3 years. [4] Management mirrors acute ischaemic stroke secondary prevention.

1. Antiplatelet Therapy

First-line:

• Aspirin 75-300 mg daily (start immediately unless contraindicated) [4]
• Alternative: Clopidogrel 75 mg daily if aspirin-intolerant

Dual antiplatelet therapy (DAPT): Consider aspirin + clopidogrel for 21 days in high-risk patients (as per stroke guidelines).

2. Anticoagulation (if Cardioembolic Source)

Indications:

• Atrial fibrillation
• Left ventricular thrombus
• Mechanical heart valve
• High-risk cardioembolism

Agents:

• DOACs (apixaban, rivaroxaban, edoxaban, dabigatran): First-line for AF
• Warfarin: If mechanical valve or contraindication to DOACs

Timing: Initiate anticoagulation within 3-14 days of CRAO (balance stroke recurrence vs haemorrhagic transformation risk).

3. Statin Therapy

• High-intensity statin: Atorvastatin 80 mg or rosuvastatin 40 mg daily [4]
• Target LDL less than 1.8 mmol/L (less than 70 mg/dL)

4. Blood Pressure Control

• Target BP less than 130/80 mmHg (as per stroke guidelines) [4]
• Avoid aggressive lowering in acute phase (maintain cerebral perfusion pressure)

5. Carotid Revascularisation

Indications for carotid endarterectomy (CEA) or stenting:

• Ipsilateral carotid stenosis ≥70% (symptomatic) [19]
• Ipsilateral carotid stenosis 50-69% (case-by-case; consider if high-risk features)

Timing: Within 2 weeks of CRAO if symptomatic severe stenosis (same as stroke/TIA guidelines).

Evidence: Carotid intervention reduces stroke risk by 50-70% in symptomatic severe stenosis. [19]

6. Diabetes Management

• Target HbA1c ≤53 mmol/mol (7%)

7. Lifestyle Modifications

• Smoking cessation
• Limit alcohol
• Regular exercise
• Healthy diet (Mediterranean diet)

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Management of Complications

1. Neovascular Glaucoma (NVG)

Incidence: 10-20% of CRAO patients develop rubeosis iridis (iris neovascularisation) within 3-6 months. [20]

Risk factors:

• Severe retinal ischaemia (large area of capillary non-perfusion on FA)
• Diabetes
• Combined CRAO + CRVO

Mechanism: Retinal ischaemia → VEGF release → iris/angle neovascularisation → angle closure → refractory glaucoma.

Monitoring: All CRAO patients should have regular slit-lamp examination (monthly for 6 months) to detect early rubeosis.

Treatment:

• Pan-retinal photocoagulation (PRP): Ablate ischaemic retina to reduce VEGF drive
• Anti-VEGF intravitreal injections: Bevacizumab or ranibizumab to regress neovascularisation
• IOP control: Topical/systemic agents
• Glaucoma surgery: Tube shunt (Ahmed/Baerveldt valve) if refractory NVG

2. Optic Atrophy

Almost all CRAO patients develop optic atrophy over 4-6 weeks. This is an expected sequela, not a complication requiring treatment.

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Referral Pathways

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Prognosis & Outcomes

Visual Prognosis

Overall: CRAO has a poor visual prognosis. [6]

Prognostic factors for better visual outcome:

• Presence of cilioretinal artery: 50-60% achieve ≥6/60 [14]
• Early presentation and treatment (less than 90 minutes)
• Initial VA better than CF
• Younger age (less than 60 years)
• Visible embolus (potentially dislodgeable)

Prognostic factors for worse visual outcome:

• Late presentation (> 4 hours)
• No light perception at presentation
• Arteritic CRAO (GCA)
• Concurrent ophthalmic artery occlusion
• Diabetes

Systemic Cardiovascular Prognosis

CRAO is a powerful marker for systemic vascular disease. [4]

Mortality: Standardised mortality ratio 1.5-2.0 compared to age-matched controls. [4]

Important message for patients: "CRAO is not just an eye problem—it's a warning sign of serious cardiovascular disease."

Fellow Eye Involvement

Non-arteritic CRAO: Risk of CRAO in fellow eye is low (less than 5% over 5 years). [6]

Arteritic CRAO (GCA): Risk of bilateral involvement is 25-50% within days to weeks if untreated. [10] High-dose corticosteroids reduce second eye involvement to less than 10%.

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Evidence & Guidelines

Key Guidelines

1. American Heart Association (AHA) Scientific Statement (2020): "Retinal Ischemia and Stroke: An Update." CRAO classified as acute ischaemic stroke; eligible for thrombolysis. [7]

2. Royal College of Ophthalmologists (RCOphth) Guidelines (2022): Recommends urgent ophthalmology referral, cardiovascular workup, and GCA exclusion in all CRAO cases.

3. American Academy of Ophthalmology (AAO) Preferred Practice Pattern (2019): "Retinal and Ophthalmic Artery Occlusions." Comprehensive diagnostic and management framework.

4. European Society of Cardiology (ESC) Stroke Guidelines (2021): CRAO should trigger stroke-equivalent cardiovascular workup.

Key Evidence

Level of Evidence Summary

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Examination Focus

MRCP PACES / Clinical Examination Stations

CRAO is a high-yield topic for clinical examinations (MRCP PACES, FRACP, OSCEs) due to its diagnostic fundoscopy findings and emergency management requirements.

Station 5: Integrated Clinical Assessment

Scenario: 68-year-old man presents with sudden painless loss of vision in the right eye 2 hours ago. BP 165/95 mmHg, irregular pulse.

Tasks:

1. Take a focused history
2. Examine the eyes and cardiovascular system
3. Formulate differential diagnosis
4. Outline immediate management plan

Expected Findings

History:

• Sudden painless monocular vision loss (right eye)
• No preceding trauma, flashes, floaters
• Vascular risk factors: hypertension, diabetes, smoking
• Ask about: amaurosis fugax, GCA symptoms, palpitations (AF)

Examination:

• Visual acuity: Right eye counting fingers; left eye 6/6
• RAPD: Present in right eye
• Fundoscopy (dilated):
  • "Right eye: Cherry-red spot at fovea, pale oedematous retina, attenuated arteries"
  • "Left eye: Normal"
• Cardiovascular: Irregularly irregular pulse (AF), BP 165/95 mmHg

Structured Approach to Fundoscopy Findings

When presented with fundoscopy images in exams, use this systematic approach:

1. Identify cherry-red spot: Confirms inner retinal ischaemia
2. Assess retinal pallor distribution:
   • Diffuse = CRAO
   • Sectoral = BRAO
   • Central sparing = Cilioretinal artery present
3. Examine retinal arteries: Attenuated? Box-carring? Visible embolus?
4. Optic disc: Pale (chronic)? Swollen (arteritic AION + CRAO)?
5. Other features: Haemorrhages (combined CRVO + CRAO)? Neovascularisation (rubeosis)?

Key Examination Viva Questions

Q: What is your differential diagnosis for sudden painless monocular vision loss?

A:

• Vascular: CRAO, BRAO, CRVO, anterior/posterior ischaemic optic neuropathy (AION/PION), amaurosis fugax
• Retinal: Retinal detachment, vitreous haemorrhage
• Optic nerve: Optic neuritis (often painful), optic nerve compression
• Other: Functional (non-organic), occipital lobe stroke (bilateral if complete)

Q: How would you distinguish CRAO from CRVO on fundoscopy?

A:

• CRAO: Pale retina, cherry-red spot, attenuated arteries, minimal/no haemorrhages
• CRVO: Swollen retina, widespread flame/blot haemorrhages, dilated tortuous veins, optic disc swelling, "blood and thunder" appearance

Q: What investigations would you request immediately?

A:

• Bedside: Visual acuity, RAPD, dilated fundoscopy, BP, ECG
• Bloods: ESR, CRP, FBC (if age > 50: exclude GCA), glucose, lipids
• Imaging: Carotid Doppler, echocardiography (TTE), OCT retina

Q: When would you consider IV thrombolysis?

A: CRAO presenting within 4.5 hours, severe visual loss, no contraindications to alteplase, shared decision-making with patient (off-label use). Activate stroke team.

Q: What are the systemic implications of CRAO?

A: CRAO indicates high cardiovascular risk—25% stroke risk within 3 months. Requires full stroke-equivalent workup: carotid Doppler, echocardiography, ECG, vascular risk factor management (antiplatelets, statin, BP control), ± carotid revascularisation.

Q: How would you manage a 75-year-old woman with CRAO, headache, and ESR 85 mm/hr?

A: Suspect GCA. Start immediate IV methylprednisolone 1 g daily for 3 days, then oral prednisolone 60 mg daily. Arrange urgent temporal artery biopsy (within 1-2 weeks). Do not delay steroids awaiting biopsy—prevents second eye involvement.

Common Examination Pitfalls

1. Forgetting RAPD: Always check for RAPD—absent RAPD suggests bilateral disease or misdiagnosis.
2. Not asking about GCA symptoms: In patients > 50, always ask headache, jaw claudication, scalp tenderness.
3. Confusing CRAO with CRVO: Know differentiating features on fundoscopy.
4. Missing stroke risk: Emphasise systemic vascular workup and secondary prevention.
5. Overestimating acute treatment efficacy: Be realistic—most patients have poor visual prognosis despite treatment.

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Patient & Family Information

What is Central Retinal Artery Occlusion (CRAO)?

CRAO is a blockage of the main blood vessel that supplies your retina (the light-sensitive layer at the back of your eye). When this artery is blocked, the retina does not get enough oxygen, and the cells that allow you to see can be permanently damaged. This is sometimes called an "eye stroke" because it is similar to a stroke in the brain.

What causes CRAO?

CRAO is most commonly caused by a blood clot or fatty deposit that travels from another part of your body (usually the heart or neck arteries) and gets stuck in the artery supplying your eye. Risk factors include:

• High blood pressure
• High cholesterol
• Diabetes
• Smoking
• Irregular heart rhythm (atrial fibrillation)
• Narrowing of the neck arteries (carotid artery disease)

In rare cases (1-2%), CRAO can be caused by inflammation of the blood vessels called giant cell arteritis (GCA), which is more common in people over 50 years old.

What are the symptoms?

The main symptom is sudden, painless loss of vision in one eye. It happens within seconds to minutes and is usually severe—many people can only see hand movements or count fingers. There is no pain, redness, or other eye symptoms.

Some people notice brief episodes of vision loss (lasting a few seconds to minutes) in the days or weeks before CRAO. This is a warning sign and should prompt immediate medical attention.

How is CRAO diagnosed?

Your doctor will:

• Check your vision and examine your eyes (including looking at the back of your eye with a special light)
• Look for a "cherry-red spot" at the centre of your retina, which is a classic sign of CRAO
• Perform blood tests to check for inflammation (if you are over 50) and other causes
• Scan your neck arteries (ultrasound) to look for blockages
• Perform a heart scan (echocardiogram) to check for clots or valve problems
• OCT scan of your retina to assess the extent of damage

Can my vision be restored?

Unfortunately, most people with CRAO do not recover useful vision, even with treatment. The retina can only survive without oxygen for about 90-110 minutes, so by the time most people reach hospital, permanent damage has occurred.

However, if you arrive at hospital very quickly (within 4-6 hours), there are some treatments that may help:

• Clot-busting medication (thrombolysis), similar to treatment for brain strokes
• Lowering eye pressure to improve blood flow
• Ocular massage to try to dislodge the blockage

Even with these treatments, recovery is not guaranteed. About 20-30% of people achieve vision good enough to drive, but most remain with severe vision loss.

A small number of people (15-30%) have an extra blood vessel (cilioretinal artery) that can protect the central vision—these patients have a better chance of recovery.

Why did this happen to me?

CRAO is a sign of underlying blood vessel disease. The same blockages that caused your eye stroke can affect your brain and heart. This means you are at higher risk of:

• Brain stroke (25% risk within 3 months)
• Heart attack
• Other vascular problems

This is why your doctors will do a thorough assessment of your heart and blood vessels and start medications to prevent future problems.

What happens next?

After CRAO, you will need:

1. Urgent tests to find the cause (heart scan, neck artery scan, blood tests)
2. Medications to prevent stroke:
   • Aspirin or clopidogrel (blood thinners)
   • Statin (cholesterol-lowering medication)
   • Blood pressure tablets
   • Possibly blood-thinning medication (anticoagulation) if you have an irregular heart rhythm
3. Regular eye checks for 6 months to monitor for complications (such as abnormal blood vessel growth in the eye, which can cause glaucoma)
4. Lifestyle changes: Stop smoking, healthy diet, regular exercise

If inflammation (giant cell arteritis) is the cause, you will need high-dose steroid tablets to protect your other eye.

Will my other eye be affected?

• If your CRAO was caused by a blood clot or fatty deposit, the risk to your other eye is low (less than 5%).
• If your CRAO was caused by giant cell arteritis (inflammation), the risk to your other eye is high (25-50%) without treatment. This is why immediate steroid treatment is so important.

What are the long-term complications?

Most people do not have further eye complications, but about 10-20% develop:

• Neovascular glaucoma: Abnormal blood vessel growth in the eye causing high eye pressure and pain. This may require laser treatment or eye drops.

Living with vision loss after CRAO

Losing vision in one eye is life-changing. You may find it difficult to:

• Judge distances (depth perception)
• See objects on the affected side
• Read or watch TV

Support and rehabilitation:

• Low vision services: Magnifiers, special glasses, adaptive technology
• DVLA notification (UK): You must inform DVLA of vision loss; you may still be able to drive if your other eye meets the visual standards
• Emotional support: Many people experience grief, anxiety, or depression after sudden vision loss. Speak to your GP about counselling or support groups.

Resources

• Royal National Institute of Blind People (RNIB): www.rnib.org.uk (0303 123 9999)
• Stroke Association: www.stroke.org.uk (helpline: 0303 3033 100)
• Macular Society: www.macularsociety.org (helpline: 0300 3030 111)
• Fight for Sight: www.fightforsight.org.uk
• DVLA guidance on vision and driving: www.gov.uk/driving-eyesight-rules

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