Early in the development of the human body, embryogenesis as it is called, the 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 Vitreous from a 9-month-old child.
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. Specimen Courtesy of the New England Eye Bank, Boston, MA)
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.
The clear vitreous we are born with is 99.9% water with two large organic molecules also present. The molecules are collagen and Hyaluronin (HA). Collagen is a long-stranded structural molecule and HA is closely associated with the collagen, coating it and giving it a surface ionic negative electrical charge.
This illustration 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.
Normally the vitreous is optically clear. In a young person, the examining eye doctor can't see this material. If there are changes such as clumping of the vitreous as occurs with aging and other factors, the transparent ocular media is no longer perfectly clear. If the density is increased enough, it will cast a shadow onto the retina and the person will see a moving shadow in their vision - A VITREOUS EYE FLOATER!
Next, we will explore the derangements of the vitreous and learn all about what causes eye floaters <HERE>
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