Sudden black eyes and fainting are mostly associated with systemic conditions such as low blood pressure, hypoglycemic malnutrition, and may also be caused by craniocerebral tumors or cerebral hemorrhage due to trauma. If there is a patient squatting and then suddenly stand up, short-term posture change, resulting in the original distribution of blood to supply the high brain, thus occurring upright low blood pressure, so that the patient has a sudden black eyes, fainting symptoms. If the patient’s diet is irregular, prolonged starvation can cause hypoglycemia, which can also lead to the patient’s eyes suddenly blackening and the symptoms of fainting. In addition, when the patient suffers from major craniocerebral trauma or craniocerebral diseases such as intracranial hemorrhage due to hemangioma, the patient may also suffer from sudden darkening of the eyes and fainting, which may even threaten the patient’s life. It is recommended that patients with sudden black eyes and fainting should seek prompt medical attention to assess their condition and undergo treatment under the guidance of a doctor.