Floaters are small specks or clouds moving in your field of vision. You often see them when looking at a plain background. Floaters are actually tiny clumps of gel or cells inside the vitreous, the clear jelly-like fluid that fills the inside of your eye. Even though they are actually floating inside, what you see are the shadows they cast on the retina.
A common cause of floaters is posterior vitreous detachment. The retina can tear if the shrinking vitreous gel pulls away from the wall of the eye. A torn retina is serious since it can lead to a retinal detachment which can lead to blindness if untreated. When the vitreous pulls hard enough to tear the retina, fluid may pass through the retinal tear, lifting the retina off the back of the eye.
Most retinal tears need to treated with laser surgery or cryotherapy which seals the retina to the back wall of the eye. Almost all retinal detachments require surgery to put the retina back in its proper place.