What is the diagnosis and recommended urgent work‑up and management for a patient who has had three brief episodes of transient loss of the lower visual field in the left eye?

Transient Monocular Visual Field Loss: Diagnosis and Emergency Management

Diagnosis: Transient Monocular Vision Loss (Amaurosis Fugax) - Retinal Transient Ischemic Attack

This patient has experienced three episodes of transient monocular visual field loss (affecting the lower visual field), which represents amaurosis fugax—a retinal transient ischemic attack that is a stroke equivalent requiring immediate emergency department evaluation at a certified stroke center within 24 hours. 1, 2

The altitudinal (lower visual field) pattern of vision loss is particularly concerning, as this pattern strongly predicts embolic etiology from carotid artery stenosis, carotid ulceration, or cardiac embolic sources. 3

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Immediate Management Algorithm

Step 1: Confirm Vascular Etiology (Same-Day Ophthalmologic Examination)

• Perform fundoscopic examination to look for retinal emboli (Hollenhorst plaques), retinal whitening, or cherry-red spot 4, 1
• Check for relative afferent pupillary defect (RAPD), which indicates significant retinal or optic nerve dysfunction 5
• Document visual acuity with current correction 5
• Assess red reflex bilaterally—any asymmetry indicates serious pathology 5

Critical Action: Once vascular TMVL is confirmed, immediately send the patient to the nearest emergency department affiliated with a certified stroke center with a note stating "Ocular TIA"—do not delay for additional ophthalmologic testing. 4, 2

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Step 2: Emergency Department Stroke Protocol (Within 24 Hours)

Neuroimaging

• Brain MRI with diffusion-weighted imaging (DWI) within 24 hours to identify silent brain infarctions, which occur in 19-25% of patients with retinal artery events 1, 2

Vascular Imaging

• Carotid artery imaging (CTA, MRA, or duplex ultrasound) is critical—up to 70% of patients with symptomatic retinal ischemia have clinically significant carotid stenosis 1, 2
• The altitudinal pattern of this patient's visual loss makes carotid stenosis highly likely 3

Cardiac Evaluation

• ECG and continuous cardiac monitoring for atrial fibrillation 1, 2
• Echocardiography to evaluate for valvular disease and cardiac embolic sources 1, 2

Laboratory Testing

• ESR and CRP in all patients over 50 years to rule out giant cell arteritis, even without classic symptoms 2, 5

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Step 3: Immediate Medical Therapy (Do Not Delay)

• Start antiplatelet therapy immediately (aspirin or dual antiplatelet therapy) without waiting for test results 1, 2
• High-intensity statin for hyperlipidemia 1, 2
• Blood pressure control 1, 2

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Step 4: Risk Stratification and Definitive Management

If High-Grade Carotid Stenosis (>70%) is Identified:

• Carotid endarterectomy (CEA) should be performed within 2 weeks of symptom onset to achieve maximal stroke prevention benefit 1, 2
• The benefit of CEA declines sharply after 2 weeks and is greatly diminished beyond this period 1
• This is the most time-sensitive intervention—the window for maximum benefit is narrow 1

If Cardiac Embolic Source is Identified:

• Anticoagulation may be indicated depending on the specific cardiac pathology 1

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Critical Pitfalls to Avoid

Do Not Delay Emergency Referral

• Only one-third of ophthalmologists currently transfer these patients immediately, despite clear guideline recommendations 1
• Eye care providers should serve as "gate-keepers" for rapid diagnosis, then immediately refer without attempting further workup themselves 4, 5

Do Not Underestimate Stroke Risk

• The risk of stroke is highest within the first 7 days after TMVL, with up to 24% risk in the first 3 months if untreated 1, 6
• Never assume that resolution of symptoms eliminates stroke risk—patients with TMVL have the same cardiovascular risk as patients with cerebral TIAs 4, 6

Do Not Miss the Surgical Window

• Carotid endarterectomy benefit is time-dependent—greatest within 2 weeks, greatly diminished after 4 weeks 1

Do Not Overlook Giant Cell Arteritis

• In patients over 50 years, always check ESR/CRP regardless of whether classic symptoms (jaw claudication, scalp tenderness, headache) are present 2, 5
• If giant cell arteritis is suspected, start empiric high-dose corticosteroids immediately to prevent bilateral blindness—do not delay for temporal artery biopsy 2

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Prognosis and Long-Term Management

• Up to 70% of patients with retinal ischemia have newly discovered significant cardiovascular conditions requiring ongoing management 2
• Risk of stroke and acute coronary syndrome remains elevated for 30 days after the initial event 1, 2
• Permanent blindness may develop in the affected eye after initial or subsequent ischemic episodes 1
• Aggressive secondary prevention with antiplatelet therapy, statin, blood pressure control, and smoking cessation is essential 1, 2
• Neurology follow-up within 2 weeks after discharge to optimize secondary stroke prevention 4, 1