Although most flashes and floaters occur in people with healthy or merely nearsighted eyes, they can be symptoms of serious problems including injury and retinal and posterior vitreous detachments. Flashes in vision are caused by pressure on the retina, the bundle of nerves in the back of the eye where images are detected and transmitted to the brain. Patients complain of flashing lights or lightning streaks.
Floaters are often seen when fibers move within the vitreous humor, the gelatinous substance made of water and protein fibers that fills the eye. Patients complain of small specks or dots that ccan be seen against clear backgrounds. Serious vision loss can occur if the retina or vitreous detach from the eye wall. Patients experiencing flashes and floaters should contact their doctor immediately so an examination can be performed.