These are called floaters. Seeing these objects seems to happen more often during middle age, although children may also observe them. Floaters are not usually harmful, although they can indicate other problems if they occur in excess. The following material answers those questions. There is a mini-quiz toward the end of this lesson.
Floaters are tiny clumps of material that are floating in the fluid inside the eye.
Some are simply blood cells or parts of other cells that have gotten loose in the fluid. After middle age, the vitreous gel in the eye degenerates and forms microscopic clumps that float around in the eye. The current in the fluid causes the floaters to move about. Although they are microscopic in size, their location between the lens of the eye and the retina magnifies their appearance in the field of vision. Floaters are usually just annoying, but if there is a sudden increase in them, it may be an indication of a detached retina.