Sudden dizziness and blackness in front of the eyes is a symptom of blackness. The main reason for blackness is temporary lack of blood supply to the brain caused by various clinical conditions. The common causes are postural hypotension, anemia, and some cardiogenic factors. For the darkness caused by postural hypotension, it is necessary to change the position slowly and actively treat the underlying diseases that may cause postural hypotension. For the blackout caused by anemia, it is necessary to actively treat the cause of anemia and correct the anemia; for the blackout caused by cardiac diseases, the most common is caused by severe slow arrhythmia, and the common ones are sick sinus node syndrome, third degree atrioventricular block, etc. For the blackout caused by severe slow arrhythmia, it is necessary to give pacing treatment.