As the eye ages, changes occur in the structure of the vitreous. The gel slowly becomes more liquefied. The fine fibers collapse and clump together, becoming string like. These clumps and strings are noticeable in the vision because light can not pass through them and they cast tiny shadows on the retina. They are commonly referred to as floaters because they move or float as the eye moves. As the vitreous gel shrinks, it starts to pull away from the retina. This is called POSTERIOR VITREOUS DETACHMENT. When the vitreous detaches, the number of floaters may suddenly increase appearing like cobwebs, hair or flies in the vision. Flashes of light may also be noticeable, caused by stimulation of the retina as the vitreous gel tugs on areas where it is still attached. Flashes are most apparent in dim light and are usually noticed in the vision "off to the side".

Most often, posterior vitreous detachment does not cause harm. The floaters tend to become less noticeable over time and the light flashes subside. In some cases however, when the vitreous detaches it pulls a tear in the retina, sometimes causing a small amount of bleeding. This may appear as a shower of tiny black spots in the vision. It is very important to have a retinal tear diagnosed and treated immediately because it can lead to a retinal detachment. If detected early, a retinal tear can usually be treated with laser.

Posterior vitreous detachment is more likely to occur in people who are very nearsighted. It is also more common after cataract surgery, hereditary eye disease, trauma and inflammation inside the eye.

You should have a dilated retinal exam if you experience any of the following symptoms: a shower of new floaters, intense flashes of light, a shadow or curtain coming over the vision or a sudden loss of vision.