Most of the eyeball is filled with vitreous gel, a jelly-like substance that helps maintain its round shape.  The vitreous contains millions of fine fibers that are attached to the retinal surface.  As we approach middle age, the vitreous slowly shrinks away from the retina, and if the fibers pull free, it becomes detached.  The fibers in the vitreous then cast tiny shadows on the retina that you notice as floaters, usually in a shape like a spider web or cogwheel. You may also see bright flashes of light off to the side whenever you mover your eye.  These are especially noticeable when you are in a darkened room.  Light flashes occur when the partially detached vitreous pulls on the retina at its surface.

Almost always, the floaters and light flashes decrease during the weeks or months after the vitreous detaches, though they may never disappear completely.  Most of the time a vitreous detachment is merely annoying because of its symptoms.  However, once in a while some of the vitreous fibers pull so hard on the retina that one or more retinal tears or holes are created. This can lead to a retinal detachment.  If a retinal tear happens to tear a retinal blood vessel, blood will spill into the vitreous and partially obstruct vision.

If you experience the sudden symptoms of a vitreous detachment described above, you need to be examined by an ophthalmologist for possible retinal tear or retinal detachment.  This is usually accomplished by a pupil dilated retina examination in the office.  The same examination is then repeated in about 4 to 6 weeks.  If retinal holes or tears are present, they can be sealed by laser treatment.  If retinal detachment is present, surgery is needed then to repair the retinal detachment.