Sudden blackness in front of the eyes of patients who can’t see clearly may be related to hypoglycemia, low blood pressure, cervical spondylosis, etc. 1. Hypoglycemia: If patients do not eat on time or eat too little, drink a lot of alcohol on an empty stomach, or exercise too much, it can cause hypoglycemia, which leads to the phenomenon of sudden blackness in front of the patient’s eyes, making it hard to see, and can be accompanied by sweating, hunger, trembling, palpitations, pallor and other symptoms. 2. Upright hypotension: because of autonomic dysfunction, abnormal blood pressure control and other factors, the patient suddenly stands up or lies down and suddenly sits up can cause upright hypotension, resulting in insufficient blood supply to the head, causing the patient to have sudden blackness in front of the eyes, and the phenomenon of not being able to see clearly. 3. Cervical spondylosis: degenerative changes in the cervical spine, chronic strain injury, long-term head-down work can lead to cervical spondylosis, when the nucleus pulposus is protruding or prolapsing, the patient’s intraocular blood supply is compressed, which can lead to sudden blackness in front of the eyes, and it is difficult to see. It is recommended that patients with worsening symptoms of sudden blackness and blurred vision should consult a doctor in a timely manner to assess their condition and follow the doctor’s instructions for treatment.