Overview
This lecture discusses amaurosis fugax (transient monocular vision loss), emphasizing its causes, evaluation, and clinical significance, particularly as a potential sign of transient ischemic attack (TIA).
Definitions and Terminology
- Amaurosis fugax means fleeting (transient) blindness, usually affecting one eye.
- Transient monocular vision loss refers to brief loss of vision in one eye; bilateral refers to both eyes.
Causes and Clinical Importance
- Amaurosis fugax can be due to TIA, which is a warning sign of possible stroke and considered a medical emergency.
- Most ischemic transient vision loss events last seconds to minutes; longer durations (hours to days) suggest different causes (e.g., optic neuritis).
- Sudden vision loss lasting more than two hours is unlikely to be reversible ischemia.
Circulation and Etiology
- Monocular (one eye) vision loss is usually due to carotid artery disease on the same side.
- Bilateral (both eyes) vision loss suggests involvement of the vertebrobasilar circulation or can be cardiogenic.
- Other causes include heart issues: atrial fibrillation, valvular disease, bacterial endocarditis, arrhythmias, or cardiac tumors such as myxoma.
Diagnostic Workup
- All suspected TIA cases need urgent evaluation: carotid Doppler ultrasound, echocardiogram (echo), and brain MRI.
- MRI with diffusion-weighted imaging helps detect silent or acute ischemia.
- Consider hypercoagulable state workup but defer to stroke specialists.
Key Symptoms and Clinical Clues
- Classic ischemic pattern: vision loss respects horizontal or vertical meridians; "curtain coming down" indicates possible TIA.
- Patient description of one-sided loss may reflect visual field loss instead of true monocular loss.
- Retinal claudication: vision loss triggered by changes in lighting, indicating retinal ischemia and carotid disease.
Elderly Patient Considerations
- Always include erythrocyte sedimentation rate (sed rate) and C-reactive protein (CRP) testing to rule out giant cell arteritis in elderly patients.
Key Terms & Definitions
- Amaurosis fugax — sudden, transient blindness in one eye.
- TIA (Transient Ischemic Attack) — temporary loss of blood flow to the brain, eye, or spinal cord.
- Retinal claudication — transient vision loss after changes in lighting, indicating retinal ischemia.
- Carotid Doppler — ultrasound test to assess blood flow in carotid arteries.
- Diffusion-weighted imaging (DWI) — MRI technique to detect early ischemic changes in the brain.
Action Items / Next Steps
- Order carotid Doppler, echo, and brain MRI for patients presenting with transient monocular vision loss.
- Assess sed rate and CRP in elderly patients to rule out giant cell arteritis.
- Refer for urgent stroke team evaluation and defer hypercoagulable workup as needed.