Sudden flashes of light in the eyes after a while may be due to physiological reasons, may also be caused by pathological reasons. 1. Physiological causes: when there is physiological posterior vitreous detachment, it may be caused by turning the eyes or head, resulting in the posterior vitreous membrane pulling on the retina and causing a transient flashing sensation, which generally does not require special treatment. 2. Pathological causes: the sudden appearance of black shadows in front of the eyes, increased flash sensation, blocked vision and other symptoms, it is suspected that trauma, inflammation and other causes of pathologic vitreous detachment, retinal detachment and so on. In this case, timely medical treatment is needed to deal with the cause of the disease. If you have frequent flashes of light in your eyes, accompanied by increased dark shadows in front of your eyes, blocked vision and other visual abnormalities, it is recommended that you go to the hospital for examination and treatment in a timely manner in order to avoid delaying your condition.