The muscle under the left eye keeps jumping may be caused by the spasm of the orbicularis oculi muscle of the left eye, which may be caused by staying up all night, visual fatigue, facial nerve injury and other reasons. 1. Staying up late: Staying up late can cause the facial nerve that innervates the orbicularis oculi muscle to become dysfunctional, resulting in abnormal electrical signals being sent out, causing the orbicularis oculi muscle to spasm, which in turn causes the muscles under the left eye to jump. 2. Visual fatigue: due to long-term close work, patients are highly concentrated, blinking times are reduced, the facial nerve sends out abnormal signals to cause orbicularis oculi spasms, and the patients feel the muscles under the left eye throbbing. 3. Facial nerve injury: due to facial trauma or viral infection and other factors lead to abnormal discharge of the facial nerve causing muscle throbbing under the left eye. The muscle throbbing under the left eye has a small impact on the patient, and can be relieved through rest and massage without special treatment, and will mostly disappear on its own. If the patient has this situation for a long time, it is recommended to seek medical treatment.