👁️ Transient Monocular Blindness (Amaurosis Fugax) refers to a temporary loss of vision in one eye, usually lasting seconds to minutes. ⚠️ It often reflects reduced flow in the ophthalmic artery and is an important warning sign of embolic stroke.

ℹ️ About

Transient Monocular Blindness (TMB) = Amaurosis Fugax.
Represents retinal ischaemia, most often due to carotid or cardiac emboli.
Identifies patients at high risk of TIA / embolic stroke.

🧬 Aetiology

🩸 Embolic occlusion or low flow in the ophthalmic artery.
💔 Ipsilateral carotid disease (plaque, stenosis) is the commonest cause.
❤️ Cardioembolism – atrial fibrillation, valvular disease, endocarditis.

🩺 Clinical Features

Classic description: “Curtain descending over vision”, lasting seconds–minutes.
Can be complete visual loss or blurred/reduced acuity.
Resolves spontaneously, but recurrence common.

Differentials

🧓 Temporal arteritis (GCA) – especially in patients >50 yrs with headache, scalp tenderness, jaw claudication, ↑ESR/CRP.
🌩️ Migraine aura – tends to have positive symptoms (zig-zag lines, flashing lights) and gradual onset.
Retinal detachment (less transient, progressive loss).
Optic neuritis (painful visual loss, often younger patients).

🔎 Investigations

🧪 Bloods: FBC, U&E, LFTs, ESR/CRP (rule out vasculitis/GCA).
🫀 ECG (AF detection), Echocardiogram (cardiac embolic source).
🧠 Carotid Doppler ultrasound (assess stenosis, plaque).
Consider MRI/MRA brain + neck vessels if stroke risk suspected.

Management – Vascular Risk Reduction

💊 Antiplatelet: Aspirin 300 mg OD stat → then 75–300 mg OD, or Clopidogrel 300 mg stat → then 75 mg OD.
🧴 Statin: Atorvastatin 20–40 mg OD (or equivalent) to stabilise atherosclerosis.
🔪 Carotid Endarterectomy: Indicated if ipsilateral carotid stenosis >50% and peri-operative risk is low.
⚡ Anticoagulation: If due to atrial fibrillation or cardioembolic source.
🌍 Lifestyle: smoking cessation, BP control, diabetes optimisation, diet & exercise.

References

🧾 Clinical Case 1 – Carotid Atherosclerosis

A 68-year-old man with a history of hypertension and smoking reports a sudden blackout in his right eye lasting 3 minutes, described as a "curtain coming down" that fully resolved. Examination is normal. Carotid Doppler reveals a 70% stenosis of the right internal carotid artery. 👉 Diagnosis: Amaurosis fugax secondary to carotid atherosclerosis. 👉 Management: antiplatelet therapy, statin, aggressive vascular risk factor control, and consideration of carotid endarterectomy.

🧾 Clinical Case 2 – Cardioembolic TMB

A 62-year-old woman with atrial fibrillation on no anticoagulation presents with transient monocular visual loss lasting 5 minutes. She describes it as a "grey fog" affecting the left eye, with spontaneous recovery. Ophthalmic exam is normal. ECG confirms AF, and echocardiography shows left atrial enlargement. 👉 Diagnosis: TMB due to cardioembolic emboli. 👉 Management: anticoagulation with a DOAC, referral to ophthalmology, and optimisation of stroke risk factors.

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Transient Monocular Blindness (TMB)