Sudden darkening of the eye is clinically referred to as a blackout, and its immediate cause is transient ischemia of the ophthalmic artery. There are two common clinical causes of ophthalmic artery ischemia, one of cerebral origin and the other of cardiac origin. The brain-derived cause is transient ischemic attack, which causes transient neurological dysfunction due to focal ischemia of the brain and retina. The mechanism is mainly due to the formation of microscopic thrombus leading to cerebrovascular ischemia, and spontaneous thrombus dissolution occurs, blood flow is restored, and symptoms disappear. Or there is a narrowing of the cerebral vessels and there is hypotension resulting in reduced cerebral blood flow, and the symptoms improve when the blood pressure is restored. Cardiogenic factors are mainly cardiac arrhythmias or cardiac valve disease causing insufficient ejection fraction of the heart, which causes cerebral ischemia and thus black mask. In addition, neuropsychological reflexes can also cause transient blackouts, such as excessive nervousness, excitement and anxiety, which can lead to the dilation of neurological reflexes and blood vessels and cause blackouts.