The most common cause of this symptom of a flashing sensation in the eye is a phenomenon that we call posterior vitreous detachment. In our eyes, there is vitreous tissue in the vitreous cavity itself, which has a relatively tight adhesion to the retina on the posterior surface when we are young. As we age, the vitreous tissue liquefies and its stability decreases, leading to the possibility of localized such adhesions in the process of vitreous activity and separation of membrane tissue from the retina. When the retinal tissues are stimulated, this phenomenon will eventually enter the brain through the visual transmission pathway, and the brain will perceive it as a visual phenomenon. Therefore, during the formation of this posterior detachment, the tiny stimuli to the retinal tissues react to our brain, and finally the flashing sensation in the corresponding area will be manifested. Generally speaking, it occurs during the complete formation of posterior vitreous detachment, and can be observed more or less frequently in middle-aged and elderly people. For most people, the process of posterior detachment is not accompanied by retinal damage or detachment fissures, so no special treatment is usually required. In a very small percentage of patients, the process of posterior detachment may be accompanied by retinal fissures and secondary retinal detachment due to retinal diseases or other fragile reasons. For these patients, after the flashing sensation, there may be a significant loss of local vision or black shadow obscuration, which requires relevant examination or even further surgical treatment.