People often think these floaters are flying bugs. These are due to pulling on the retina as the gel separates. This pulling stimulates the retina resulting in a flash of light. If a retinal blood vessel is broken from the pulling a vitreous hemorrhage can occur. A small amount of blood may be seen as a shower of spots.
Larger hemorrhages can cause large dark blobs in the visual field or a overall decrease in vision.
If the gel is abnormally adherent to the retina or the retina is weak in a certain area a retinal tear can occur as the gel separates and pulls away from the retina. Once a retinal tear develops there is a significant risk of the liquid vitreous going through the break and detaching the retina from the back wall of the eye. This is why a PVD is such a significant event. A PVD is the initiating event of most retinal detachments. Awareness of the symptoms of a PVD is the critical first step in preventing a retinal detachment.