The small specks or "bugs" that many people see moving in their field of vision are called floaters. They are frequently visible when looking at a plain background such as a blank wall or blue sky. Floaters were described long ago, in Roman times as flying flies ("muscae volitantes").
Floaters are small clumps of gel that form in the vitreous, the clear jelly-like fluid that fills the inside cavity of the eye. Although they appear to be in front of the eye, they are actually floating in the fluid inside the eye and are seen as shadows by the retina (the light sensing inner layer of the eye).
The appearance of floaters, whether in the form of little dots, circles, lines, or cobwebs, may cause much concern, especially if they develop suddenly; however, they are usually of little importance, representing an aging process. The vitreous gel shrinks with time, pulls away from the retina and causes floaters. This is especially common in near sighted people or after a cataract operation.
As the vitreous gel pulls away, the retina may be torn, sometimes causing a small amount of bleeding in the eye which may appear as a group of new floaters. If this tear becomes a retinal detachment it can be serious and vision loss may ensue.
Without examination by an ophthalmologist, there is no way for a person to determine whether floaters are serious. Any sudden onset of many new floaters or flashes of light should be evaluated by your eye doctor.
The vitreous gel which fills the inside of the eye sometimes pulls or tugs on the retina. This pulling causes the appearance of flashing lights or lightning streaks, though there is no flashing light actually present.