Early in the development of the human body, embryogenesis as it is called, the vitreous space is filled with blood vessels. These vessels are most prominent during the 9th week of gestation. They begin to atrophy to the point where blood flow ceases entirely in this vitreous space by the 7th month of gestation. It is not known for sure what stimulates the death and disappearance of the blood vessel cells but it some form of pre-programmed death the blood vessel cells.
fig.1 Human Vitreous Body. The outer, white sclera and retina have been removed.
In fig.1, the sclera, choroid, and retina were dissected off the vitreous, which remains attached to the anterior segment. Because of the young age of the donor, the vitreous is almost entirely gel. Thus, the structure is solid and maintains its shape, although situated on a surgical towel exposed to room air. (From Duane’s Ophthalmology, Chapter 16, J. Sebag, M.D.)
The clear vitreous we are born with is 99.9% water. The remaining 0.1% consists of two large organic molecules. The molecules are Collagen and Hyaluronin (HA). Collagen is a long-stranded structural protein molecule and HA is closely associated with the collagen, coating it and giving it a surface ionic negative electrical charge. The vitreous undergoes significant growth (along with the other size measurements of the eye) during childhood and trends to stabilize near adult measurements by the early teens.
fig.2 Vitreous collagen strands are separated by a negative electrical surface charge. Overall, it is mostly water.
Figure 2 shows the bundling of different subtypes of collagen fibers. There are some branching strands that connect to other collagen bundles traversing different directions. The soft “fuzzy” coating of the bundles shown in the lower half is the hyaluronin (HA) molecules which promotes dispersion rather than clumping of the collagen fibers. Water molecules, symbolized by small blue circles fill the space in between. By mass, vitreous consist of 99.9% water molecules, so in actuality, if this drawing were to scale, the collagen fibers would be much further apart.
Collagen, by itself is normally attracted to itself and has a tendency to clump up. It may be the hyaluronin molecules that keep it separate and separated by water. If something affects the hyaluronin coating, collagen may clump, and voila!, an eye floater forms.
There may be some unknown factors that disturb the balance and affect the hyaluronin surface coating of the collagen. Some medication or toxins, perhaps, may gradually seep into the vitreous and cause some areas of the vitreous to clump up. This may be the explanation for the typical, small floaters near the retina seen in younger patients who do not otherwise have diffuse aging and degeneration of the vitreous.
