Abdur Rehman MBBS, Samar Mehdi MBBS, Junaid Kalia MD
IntroductionEpidemiologyAnatomyFigure 1: Ophthalmic artery and its branchesMicrosurgical Anatomy Figure 2: Cilioretinal retinal arteryRisk FactorsTypes of Central Retinal Artery Occlusion1. Non-arteritic permanent CRAO2. Non-arteritic transient CRAO3. Non-arteritic CRAO with cilioretinal sparing4. Arteritic CRAOPathophysiologyClinical PresentationClinical FeaturesFigure 3: Cherry red spot , retinal edema and vessel attenuation visible in CRAOOcular Evaluation in different types of CRAOVisual Field Defects In Central retinal Artery OcclusionDifferential DiagnosisInvestigationsManagementLower IOPVasodilatorsReduce Retinal EdemaDislodge the ClotEmbolus ThrombolysisFactors Which Influence the Visual OutcomeSite of Occlusion Of Central Retinal Artery Dural sheathLamina cribrosaCauses of OcclusionLength of CRAOPatent Cilioretinal ArteryConclusionFurther ReadingBibliography
Introduction
- Opthalmological Emergency
- Complete vision loss in one eye
- Analoguous to Acute Ischemic Stroke
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Central Retinal Artery Occlusion (CRAO) is an ophthalmologic emergency that may result in a complete vision loss that is frequently irreversible. It is considered as having a stroke of the eye.
Epidemiology
- Occurs in an estimated 1 in 100,000 people
- Occurs in 1.90 per 100,000 in the United States white population
- Accounts for 1 in 10,000 ophthalmologic outdoor visits
- 80% of patients have a visual acuity of 20/400 or worse
- Incidence in men is 1.47 times higher than in women
- <2% patients present with bilateral involvement
- Mean age of presentation is early 60s
Anatomy
- Central retinal artery originates from the intra-orbital part of the ophthalmic artery which is the first branch of internal carotid artery
- Arises medial to the ciliary ganglion
- Usually, the first branch of the ophthalmic artery (67%), may present as a second branch (28%)
- Follows a tortuous path inside the orbital cavity
- Enters optic sheath 18.6 mm from the distal end of the optic canal, 8.0 mm behind the posterior pole of the globe
- Penetrates lower surface of the dura matter in an oblique manner 1 cm behind the eyeball on the inferomedial side of the optic nerve
- Courses through the meninges and crosses the cranial nerve to be located in its center
- Reaches the optical papilla where it divides to give branches
- Cilioretinal artery is present in 49.5% of patients and it supplies the papillomacular bundle
Figure 1: Ophthalmic artery and its branches

Microsurgical Anatomy
- Has narrowing at the level of the dural sheath and at the level of the cribriform plate
- Distance Between the dural perforation point of the Central retinal artery and the optic disc is 8.36 mm
- The average diameter is 0.4 mm
Figure 2: Cilioretinal retinal artery

Risk Factors
- Hypertension
- Hyperlipidemia
- Smoking
- Diabetes Mellitus
- Hyperhomocysteinemia
- Family history of vascular disease
- Use of cocaine
- Polycythemia vera
- Vasculitis
- Thrombophilia
- Sickle cell anemia
- Multiple myeloma
- Systemic lupus erythematosus
- Prothrombin III mutation
- Giant Cell Arteritis
- Intravitreal Injection of VEGF Therapy
- Orbital or Head Injuries
Types of Central Retinal Artery Occlusion
Central retinal artery occlusion can be classified into four types as follows:
1. Non-arteritic permanent CRAO
- This accounts for >2/3rd of cases of CRAO.
- Non-arteritic permanent CRAO occurs when a thrombus or embolus, as a result of atherosclerotic disease, blocks the central retinal artery.
2. Non-arteritic transient CRAO
- This accounts for 15โ17% of cases of CRAO.
- According to a proposed mechanism, transient vasospasm occurs due to serotonin release from platelets on atherosclerotic plaque. This vasospasm is reversible hence this form of CRAO has the best prognosis.
3. Non-arteritic CRAO with cilioretinal sparing
- Preserved perfusion of the macula by the cilioretinal artery, which is present in 49.5% of the population, results in macular sparing.
4. Arteritic CRAO
- This accounts for 4.5-5% of cases of CRAO.
- This is caused by vasculitides, which in almost all cases is Giant Cell Arteritis.
Pathophysiology
- Most common cause: Thromboembolic
- Central retinal artery occlusion is embolism formed due to atherosclerotic plaques derived from carotid artery
- Cholesterol (74%)
- Fibrin (15.5%) and
- Calcific material (10.5%)
- Most common Artertic Process: Giant Cell Arteritis. GCA causes nodular granulomatous inflammation of medium and large sized arteries leading to the development of a fragmented internal elastic lamina and FFA in patients show occlusion of posterior ciliary artery which supply the optic nerve head and cilio-retinal arteries resulting in arteritic anterior ischemic neuropathy
- Occlusion of central retinal artery leads to hypoperfusion of retina, retinal cell damage and eventually necrosis
- Central retinal artery occlusion of about 240 minutes results in irreversible retinal damage
- Other less common sources of emboli include
- Tumor emboli from cardiac myxoma
- Fat emboli from bone fractures
- Bacterial endocarditis induced emboli and
- Septicemia induced septic emboli
- Thrombi due to atherosclerotic disease, collagen-vascular diseases, inflammatory or hypercoagulable diseases can cause central retinal artery occlusion
- Other causes of occlusion include a foreign body, migraine, spasm of the central retinal artery, or encephalitis
Clinical Presentation
Clinical Features
- Presents as a transient , painless monocular vision loss (amaurosis fugax) and an afferent pupillary defect
- May be preceded by transient visual obscurations ( migrating embolism or giant cell arteritis )
- May complain of a purplish hue to the blur
- May complain of hallucinations
- Simultaneous onset of CRAO in both eyes is rare
- Central vision may be preserved if cilioretinal artery is present
- Visual acuity may vary from loss of light perception to finger counting
Figure 3: Cherry red spot , retinal edema and vessel attenuation visible in CRAO

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Ocular Evaluation in different types of CRAO
Table 1: Ocular Evaluation in different types of CRAO
Changes
Permanent CRAO
Permanent CRAO with cilioretinal artery sparing
Transient CRAO
Cherry red spot present , Diffuse retinal opacity present in the posterior fundus or macular region , Retina in the macular region becomes atrophic after retinal opacity resolves
Cherry-red spot, retinal opacity and cotton-wool spots are present in 3% patients within 7 days of onset
Retinal pigment epithelial changes is present in 13% of patients
Box-carring (cattle trucking) is present in 19% of patients within 7 days of onset
Box-carring is present in 16% of patients within 7 days of onset
Box-carring is not present
Retinal venous attenuation is present in 18% of patients within 1 month of onset
Retinal venous attenuation is present in 29% of patients within 1 month of onset
Retinal venous attenuation is present in 6% of patients within 1 month of onset
Disk edema is always present in arteritic CRAO
Disk is pale in 39% of NA-CRAO patients
Disk edema is present in 6% patients
Disk is pale in 75% of patients within 2 months of onset
Disk edema is present in 6% patients
Visual Field Defects In Central retinal Artery Occlusion
- Temporal island (59%)
- Central and centrocecal scotoma (19%)
- Complete blindness (10%)
- Peripheral constriction (8%)
- Paracentral scotoma (3%)
Differential Diagnosis
- Retinal vein occlusion
- Retinal detachment
- Giant cell arteritis
- Multiple sclerosis
- Acute angle-closure glaucoma
- Papilledema
- Globe rupture
- Sickle cell anemia
- Epilepsy
Investigations
- Complete blood count and coagulation assays (PT/INR, PTT)
- ESR and CRP (more reliable) levels to rule out giant cell arteritis
- CT head without contrast to rule out intracranial hemorrhage
- Fluorescein angiography for the presence of posterior ciliary artery occlusion
- Trans esophageal echocardiography to evaluate heart lesions which can be a source of emboli
- Lipid profile(LDLs should be not more than 70s mg/dL)
- Thrombophilia evaluation by a thrombophilia screen
- Consider intravenous fluorescein angiography to confirm the diagnosis
Management
- Distinguish complete from incomplete CRAO to identify patients that might benefit from treatment
- Advise the patient to have a low-fat diet rich in fruits, vegetables, fish and lean meats for secondary prevention
Lower IOP
- Perform an emergency anterior chamber paracentesis
- Perform ocular massage using a three-mirror contact lens by compressing the gobe for 10 seconds followed by a 5 second release or over closed eyelids for 15โ20 minutes
- Treat with intravenous mannitol 1.5โ2 g/ Kg over 30โ60 min . Contraindicated if the patient is hypersensitive, severely dehydrated, or has progressive renal disease
- Inject Intravenous acetazolamide 500 stat / 250 mg every 4 hours for 24 h . Contraindicated if the patient is hypokalemic , hyponatremic and suffers from a sulfa allergy or liver, renal disease
- Treat with timolol 0.25% ophthalmic solution 1 gtt every 12 hours . If it is not effective then increase to 0.5% 1 gtt every 12 hours
Vasodilators
- Treat with Pentoxifylline 600 mg TDS (vasodilator) if the patient is not allergic to theophylline or caffeine
- Start hyperbaric oxygen 2โ2.5 atm for 90 min within 8 hours of onset
- Treat with sublingual isosorbide dinitrate 10 mg. Contraindicated if patient is hypersensitive, anemic or has a recent use of phosphodiesterase inhibitors
- Start carbogen inhalation for 10 min per hour when awake and 10 min every 4 hours at night. Continue for 48โ72 hours
Reduce Retinal Edema
- Treat with a single dose of 1g intravenous methylprednisolone. Not recommended for non-arteritic permanent CRAO
Dislodge the Clot
- Use Nd YAG laser 0.8โ1.1 mJ intensity focused on arterial wall behind embolus to dislodge the embolus
- Perform a pars plana vitrectomy followed by embolus removal
Embolus Thrombolysis
- Administer intra arterial continuous infusion of tPA 40โ80 mg or urokinase in a dose range of 300,000 to 1 million units . Contraindicated if patient has an evidence of intracerebral hemorrhage, a suspicion of subarachnoid hemorrhage, myocardial infarction, intracranial or intraspinal surgery , serious head trauma or stroke in the last 3 months , gastrointestinal or genitourinary hemorrhage in the previous 3 weeks, a history of intracerebral hemorrhage and uncontrolled hypertension at time of treatment or a blood glucose >22.22 mmol
- Perform follow-up ophthalmic examination 1-4 weeks after the event to check for neovascularization
Factors Which Influence the Visual Outcome
Site of Occlusion Of Central Retinal Artery
- Determines the amount of residual retinal circulation
Dural sheath
- Pial and intraneural collaterals are intact and establish residual retinal circulation
Lamina cribrosa
- No collaterals present to establish retinal circulation
Causes of Occlusion
- Giant cell arteritis involves the posterior ciliary artery
- When the common trunk is occluded , both arteries are occluded which is characteristic of arteritic CRAO but rare in NA-CRAO
- The combined occlusion has a much worse visual loss than in NA-CRAO
Length of CRAO
- Central retinal artery occlusion of upto 97 min has no detectable damage
- Central retinal artery occlusion of about 240 minutes results in irreversible retinal damage
- Increased duration of ischemia results in increased duration before any improvement of function occurs after circulation is restored
Patent Cilioretinal Artery
- If it supplies the foveal region, visual acuity is almost always normal
- If its supply just reaches the foveola , there is an initial marked fall of visual acuity but it improves markedly within 2โ3 weeks
- If it supplies a small peripapillary region , a small visual field is present with poor visual acuity
Conclusion
- Although an accepted evidence-based therapy for CRAO does not exist , a quick diagnosis , ruling out giant cell arteritis and management to prevent further end-organ ischaemia within 6 hours of onset of symptoms must be done pending future management guidelines
Further Reading
- Argyrios Chronopoulos, James S. Schutz, Central retinal artery occlusionโA new, provisional treatment approach, Survey of Ophthalmology, Volume 64, Issue 4, 2019
- Dumitrascu, Oana M. MD, MSc; Newman, Nancy J. MD; Biousse, Valรฉrie MD Thrombolysis for Central Retinal Artery Occlusion in 2020: Time Is Vision!, Journal of Neuro-Ophthalmology: September 2020 - Volume 40 - Issue 3 - p 333-345 doi: 10.1097/WNO.0000000000001027
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