There are many reasons for dizziness and blackness in front of the eyes, and the common reasons include the following: 1, insufficient blood supply to the cerebral arteries, for example, ischemia of the posterior circulation can lead to dizziness, and ischemia of the internal carotid artery can lead to blackness in front of the eyes; 2, blood pressure abnormalities, high blood pressure and low blood pressure can cause cerebral blood perfusion abnormalities, which can lead to the formation of dizziness and blackness in front of the eyes; 3, hypoglycemia, people with blood glucose lower than 3.9 mmol/L in general will appear to be Dizziness, blackout symptoms; 4, autonomic dysfunction, such as upright position intolerance, urinary reflex syncope, high collar syndrome, etc., are due to autonomic dysfunction caused by dizziness, blackout, and even syncope and other symptoms; 5, cardiac arrhythmia, such as sinus arrest, sick sinus node syndrome of the patient will also affect the cerebral blood perfusion, and dizziness, blackout symptoms before the eyes; 6, part of the patients with subarachnoid hemorrhage also start with symptoms of dizziness and blackout.