The vitreous humor helps to keep the retina firmly in place, according to WebRN-MacularDegeneration.com. Additionally, the vitreous humor fills much of the eye, allowing light to pass through the lens to the retina and helping the eye to keep its round shape. The space the vitreous humor fills is called the vitreous body.
Healthline explains that vitreous humor is composed primarily of water, but other substances, such as salts, sugars and collagen, are also constituents of the gel. As it is necessary for light to penetrate the substance, it must remain very clear. The vitreous humor is a static collection of fluid. This means that it is not replenished or replaced by the human body. By contrast, the aqueous humor, which resides near the front of the eye, is routinely replaced. This means that if some substance enters the vitreous humor, usually blood, fibers or blood vessels, it remains there until removed surgically.
According to WebRN-MacularDegeneration.com, the vitreous humor can become less gel-like and more liquefied as people age. This liquefaction can cause fibers from the retina to detach and float freely through the vitreous humor. These free-floating fibers sometimes become noticeable in people's field of vision, appearing as dust, strings, dots or cobwebs, and physicians call them floaters.