Patients with flashes at the edge of the eyes may be caused by refractive error, posterior vitreous detachment and retinal diseases. 1. Refractive error: Most common in patients with moderate to high refractive errors, the flashing sensation at the edge of the eye often occurs after eye fatigue. 2. Posterior vitreous detachment: As the vitreous body pulls on the retina during the process of posterior detachment, it can lead to flashes of light around the edges of the eyes. 3. Retinal diseases: When retinal diseases or eye diseases involve the retina, it may lead to flashes of light at the edge of the eyes, such as retinal tear, retinal detachment and so on. It is recommended that patients with flashes of light around the edges of the eyes should consult a hospital in time to assess their condition and follow the doctor’s instructions for treatment.