When the vitreous gel liquefies, its structure collapses, and it separates or pulls away from the retina. This event is known as a posterior vitreous detachment, and it is quite common. It occurs in most people by the age of 60 years. This vitreous separation may be may be induced by severe trauma, such as a direct punch to the eye. They also tend to occur in very nearsighted individuals at a younger age.
Several things can happen when the vitreous separates from the retina.
When tape is pulled from wallpaper, pieces or paper, or flecks of paint may come away with the tape. Floaters occur when the vitreous pulls a few fine flecks from the surface of the retina, the eye's wallpaper. These flecks float around in the vitreous and may appear as black dots, flies, blobs, or cobwebs. When bright light enters the eye, these flecks cast a shadow on the retina. Therefore, they are most noticeable when looking at brightly-lit backgrounds, such as a white wall, the sky, or the newspaper.