Transient monocular blindness (TMB) or amaurosis fugax is diagnosed when visual disturbance or loss (blindness, dimming, fogging, blurring) affects one eye for seconds or minutes. TMB may occur alone or in combination with transient hemispheric ischaemia (TIA). The cause of TMB is usually an atheromatous plaque at the carotid bifurcation in the neck liberating emboli or causing a temporary reduction in carotid and retinal blood flow. In most patients no embolus or ischaemic change is visible in the fundus. TMB should be investigated and treated in the same way as neurologic TIAs with emphasis on rapid detection of extracranial arterial disease, cardiac abnormalities and haematological disorders.