Central Retinal Artery Occlusion (CRAO)
Central retinal artery occlusion (CRAO) is a form of acute ischemic stroke that causes severe visual loss and is a harbinger of further cerebrovascular and cardiovascular events, requiring immediate emergency medical attention. 1
Definition and Pathophysiology
- CRAO is defined as an interruption of blood flow through the central retinal artery by thromboembolism or vasospasm with or without retinal ischemia 1
- It is a form of retinal infarction, where retinal cell death occurs due to ischemia 1
- CRAO is classified as part of the central nervous system infarction spectrum, making it a true stroke equivalent 1
Clinical Presentation
- Sudden, painless decrease in visual acuity and field of vision in one eye that occurs over seconds 1
- Fewer than 20% of affected patients regain functional visual acuity in the affected eye 1
- Classic funduscopic findings (which may develop hours after onset):
Types of CRAO
- Nonarteritic CRAO: Occurs as a result of local thrombus formation or thromboembolism 1
- Arteritic CRAO: Occurs in the context of a systemic inflammatory condition (e.g., giant cell arteritis) 1
- CRAO with or without cilioretinal artery sparing 1
Significance and Urgency
- CRAO is a medical emergency requiring immediate triage to an emergency department 1
- It is associated with high risk of recurrent stroke and cardiovascular events 1
- The risk of stroke is maximum within the first few days after onset of visual loss 1
- Delay in seeking treatment is common, with mean time from onset to presentation of 31 hours in one study 2
Management Approach
- Acute CRAO should be treated as a medical emergency with immediate referral to a stroke center for evaluation and possible intervention 1
- Current literature suggests treatment with intravenous tissue plasminogen activator (tPA) may be effective if administered early 1
- The therapeutic window for potential benefit appears to be within 4.5-6 hours of symptom onset 1, 3
- Patients should undergo urgent screening and treatment of vascular risk factors 1
- Screening for arteritis is essential, as arteritic CRAO requires immediate steroid therapy to preserve vision in the contralateral eye 1
Diagnostic Evaluation
- Immediate ophthalmological examination to confirm diagnosis 1
- Brain imaging (MRI with diffusion-weighted imaging) 1
- Vascular imaging to identify potential sources of emboli 1
- Screening for giant cell arteritis in appropriate cases 1
Treatment Considerations
- Despite >150 years of research, there are no definitively proven treatments to reverse vision loss from CRAO 1
- Intravenous tPA (0.9 mg/kg with 10% given over 1 minute and remainder over 59 minutes) may be considered within 4.5 hours of symptom onset 1
- Observational data suggests a 50% rate of clinical recovery when thrombolytic therapy is administered within 4.5 hours 1
- Supplemental oxygen therapy (including hyperbaric oxygen in some cases) has been proposed but remains investigational 4
- Long-term management focuses on secondary stroke prevention 5
Prognosis and Follow-up
- Visual prognosis is generally poor without intervention 1
- Patients require monitoring for development of neovascularization, which may require panretinal photocoagulation if it occurs 1
- Comprehensive evaluation and management of cardiovascular risk factors is essential 5
Key Pitfalls to Avoid
- Delaying emergency referral to perform additional testing in the outpatient setting 1
- Failing to recognize CRAO as a stroke equivalent requiring the same urgency as cerebral ischemia 1
- Missing giant cell arteritis as a potential cause, particularly in older patients 1
- Assuming that late presentation (>4.5 hours) negates the need for urgent evaluation, as patients still require comprehensive stroke workup 1