The space between the crystalline lens and the retina is filled with a clear, gel-like substance called vitreous . In a newborn, the vitreous has an egg-white consistency and is firmly attached to the retina. With age, the vitreous thins and may separate from the back of the eye. As the vitreous pulls free from the retina, it is often accompanied by light flashes or floaters. Floaters are caused by tiny bits of vitreous gel or cells that cast shadows on the retina.
Flashes occur when the vitreous tugs on the sensitive retina tissue.
There are other more serious causes of flashes and floaters, however. Retinal tears , retinal detachment , infection, inflammation, hemorrhage, or an injury such as a blow to the head may also cause floaters and flashes. Occasionally, flashes of light are caused by neurological problems such as a migraine headache . When related to a headache, the flashes of light are seen in both eyes and usually lasts 20-30 minutes before the headache starts. Notify your physician immediately if you notice a sudden shower of floaters, new light flashes, a veil or curtain obstructing your vision, or any other change.