Transient dark haze, a typical symptom of internal carotid artery lesions. This symptom often occurs without any aura and often without any precipitating factors. Patients experience a sudden onset of painless vision loss in one eye. The most frequent complaint is a sudden blurring of the visual field in one eye from the top of the visual field downward to a dark gray or black curtain-like appearance that quickly covers the lower visual field vertically; sometimes the change can also spread upward from the lower visual field of one eye and gradually cover the upper visual field. The loss of vision peaks within seconds and quickly encompasses the entire visual field, appearing completely black or gray. Sometimes partial loss of vision occurs, including the upper or lower visual field. It is accompanied by a blind spot with very clear margins, and occasionally a 1/4 visual field loss in one eye may occur. Visual field loss is often completely recovered in 5 to 19 min, and vision loss is mostly recovered. The occurrence of transient black haze is the same as that of TIA in the internal carotid distribution and is caused by emboli. The embolus enters the retinal artery causing a temporary cessation of the retinal circulation. Due to the dissolution of the embolus, the temporary black haze can return to normal completely. In patients with temporary black haze, white or gray emboli can be seen passing in the small retinal arteries during the attack. These emboli are highly mobile and can quickly pass through the retinal vessels without leaving a residual embolus. This embolus pathology is composed of platelets and fibrin and originates from platelet-fibrin emboli on carotid atherosclerotic plaques or from cholesterol-fat emboli on ulcerative atherosclerotic plaques. The region of origin of retinal artery emboli is often the internal carotid artery away from the carotid bifurcation. Transient dark haze is a diagnostically important symptom. It often indicates that occlusion of the ipsilateral carotid artery is going to occur, so it is often seen clinically as a prognosis of carotid artery disease. 70% to 97% of patients with transient black haze can be predicted to have carotid artery disease. Clinical and cerebral angiography also further confirmed the interrelationship between the two. One report studied the natural history of 80 patients with transient haziness, with an average follow-up of 4 years, and found a 16.2% incidence of permanent vision loss and stroke. In another report, the incidence of permanent vision loss and stroke was 37.5% after 6 to 10 years of follow-up for temporary dark haze, with the latter incidence similar to the natural history of TIA caused by hemispheric arteries. Signs and symptoms of transient dark haze, visual impairment, fatigue, headache, and ocular motility disorders can be caused by retinal artery embolism. The sudden onset of dizziness, severe headache, blurred vision, transient black haze, and hemianesthesia should be taken very seriously. Although these symptoms quickly return to normal, the onset of the disease is likely to be due to transient cerebral ischemia. As the disease progresses, the probability of stroke is high after 3 to 5 years, and irreparable neurological dysfunction, such as hemiplegia and aphasia, may occur. Therefore, once the aura symptoms appear, it is crucial to visit the hospital promptly to eliminate its hidden problems so as not to delay the disease, which is the key to prevent strokes. The obstruction may be preceded by a vasospasm and the patient may experience a transient black haze for a few seconds or minutes. In the case of branch vessel obstruction, the retina supplied by the vessel will have a visual field defect due to loss of function, but if the obstruction is short-lived, vision and visual field defects can be partially restored. Transient dark haze. If it is caused by retinal vasospasm. It may also be caused by obstruction of the fundic artery. If the latter is the case it can cause damage to vision or even blindness …… Fundus artery obstruction is caused by acute ischemia of the retinal tissue due to thrombosis of the fundus artery. The main manifestation is a sudden and dramatic loss of vision. It is one of the emergencies leading to ocular blindness. A small number of patients have aura symptoms. In a few patients, there is an aura of a black haze in one eye. The vision returns to normal after a few minutes. It can recur several times. Eventually, obstruction occurs. Vision cannot be restored …… For healthy middle-aged and young people, transient black haze can also occur under the stimulation of flashing lights, computers or in cases of visual fatigue. Most of them are caused by retinal vasospasm. Generally, it can be relieved as long as the eyes are well rested or the mind is relaxed. If there are hazy symptoms, early examination, timely detection of lesions and timely treatment can reduce the rate of disability and death, and reduce the burden on the family.