There are several possibilities: 1, anemia, if the number of red blood cells in the patient’s blood decreases, the hemoglobin content decreases, resulting in a decrease in the amount of oxygen carried by red blood cells, the brain is very dependent on the nutrients and oxygen transported by the blood, if the degree of anemia is heavy often appear dizziness, blackness in front of the eyes, patients often have a pale face, lips and conjunctiva are pale color, improve the routine blood test 2, hypotension, if the patient has heart disease, arrhythmia, weakness, resulting in low blood pressure for a long time, will also lead to dizziness and blackness in front of the eyes, mainly because the blood pressure can not be well maintained, can not make sufficient blood supply to the brain, resulting in whole brain ischemia, ophthalmic artery ischemia will have blackness in front of the eyes. 3, vascular lesions, mostly seen in elderly patients, if atherosclerosis leads to If atherosclerosis leads to narrowing or occlusion of the large blood vessels in the neck, it will also cause a reduction in blood supply to the brain, resulting in blackness and dizziness in front of the eyes.