Seeing flashing lights or floaters can be a cause for concern. They’re caused by changes in the vitreous fluid which occupies the posterior chamber of the eye. This jelly-like fluid, which interphases with the sensory retina at the back, wants to shrink and liquify with aging, causing changes to the vitreous body as well as a traction on the retina. These changes produce the effects seen as flashes of lights or small floating spots moving in the field of vision. A more serious consequence would be a curtain which doesn’t float but covers a part of the visual field. In either event, they should be investigated with a professional eye exam.