Sudden bleeding from the lower left side of the eyeball is considered to be caused by fundus hemorrhage, and the common causes include external stimulation, bad habits, ocular diseases, systemic diseases and other causes. 1. External stimulation: fundus hemorrhage can be caused by eye injury, head trauma, exposure to chemicals, etc. In this case, it is necessary to go to the hospital in time to check the exact degree of bleeding. In this case, you need to go to the hospital in time to check the specific degree and timely treatment, so as not to aggravate the scope of hemorrhage. 2. Bad habits: If you stay up too late and look at electronic products for too long, it can also cause fundus hemorrhage. Bad habits caused by fundus hemorrhage need to pay more attention to rest, reduce the time of eye use. 3. Eye diseases: optic neuritis, macular degeneration, high myopia and other eye diseases can cause fundus hemorrhage. Bleeding caused by eye diseases needs timely treatment of the original disease, pay more attention to rest. 4. Systemic diseases: diabetes mellitus, hypertension and other diseases, due to arteriosclerosis of the fundus, can cause blood vessel rupture and bleeding. Sudden bleeding from the lower left side of the eyeball, if it is not relieved after resting and accompanied by other discomforts, you need to go to the hospital in time to check the specific cause and treatment, so as not to delay the condition.