Transient monocular visual loss (“ocular transient ischemic attack [TIA]”) is usually caused by a retinal embolus from ipsilateral carotid disease or the heart. The visual loss is characteristically described as a curtain passing vertically across the visual field with complete monocular visual loss lasting a few minutes and a similar curtain effect as the episode passes (amaurosis fugax; also called “fleeting blindness”). An embolus is rarely seen on ophthalmoscopy. Other causes of transient, often recurrent, visual loss due to ocular ischemia are giant cell arteritis, hypercoagulable state (such as antiphospholipid syndrome), hyperviscosity, and severe occlusive carotid disease. More transient visual loss, lasting only a few seconds to 1 minute, usually recurrent, and affecting one or both eyes, occurs in patients with optic disk swelling, for example in those with raised intracranial pressure. There is a benign entity of recurrent transient visual loss ascribed to choroidal or retinal vasospasm.
In most cases, clinical assessment and investigations are much the same as for retinal artery occlusion with emphasis on identification of a source of emboli, since patients with embolic transient vision loss are at increased risk for stroke, myocardial infarction, and other vascular events. Optic disk swelling requires different investigations.
All patients with possible embolic transient visual loss should be treated immediately with oral aspirin (at least 81 mg daily), or another antiplatelet drug, until the cause has been determined. Affected patients with 70–99% (and possibly those with 50–69%) ipsilateral carotid artery stenosis should be considered for urgent carotid endarterectomy or possibly angioplasty with stenting (see Chapters 12 and 24). In all patients, vascular risk factors (eg, hypertension) need to be controlled. Retinal embolization due to cardiac arrhythmia, such as atrial fibrillation, or hypercoagulable state usually requires anticoagulation. Cardiac valvular disease and patent foramen ovale may require surgical treatment. In the benign variant of transient monocular blindness, calcium channel blockers (such as slow-release nifedipine, 60 mg/day) may be effective.
In all cases of episodic visual loss, early ophthalmologic consultation is advisable.
Referral to a stroke center or hospital admission is recommended in embolic transient visual loss if there have been two or more episodes in the preceding week (“crescendo TIA”) or the underlying cause is cardiac or a hypercoagulable state.
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et al. Prevalence and associations of retinal emboli with ethnicity, stroke, and renal disease in a multiethnic Asian population: The Singapore Epidemiology of Eye Disease Study. JAMA Ophthalmol. 2017 ...