The vitreous body fills most of the interior of the eye and thus sits between the lens and the retina. Consequently, light entering through the pupil and lens must pass through the vitreous before it reaches the retina.

The vitreous body consists of a gel-like substance that is 98 percent water, as well as sugar and protein (hyaluronic acid) and a network of collagen fibers. Surrounded by a thin membrane layer, it is almost completely transparent due to the high water content - it maintains the shape of the eye. The vitreous body is only partially connected / attached to the retina.

In the course of life, the vitreous body can also change due to age: Thus, its protein components can separate from the water and float as small, collected structures (floaters) in the vitreous body. Especially against a bright background, these are perceived as "flying gnats".