The most common cause is a vitreous detachment, when the gel or vitreous in the eye separates from the retina. In most people, vitreous detachments cause no problems; the vitreous separates painlessly over several weeks and creates some temporary floaters and flashes of light. In some people, however, a vitreous detachment creates a retinal tear or hole or retinal detachment, which requires repair with either retinal surgery or laser surgery. Since we don’t know who will have a problem when a posterior vitreous detachment occurs, it’s important for people to be checked by an ophthalmologist if they experience eye floaters or flashes of light.