Please tell me everything you can about the vitreous humor in the eye.?

I wanna know about the liquid inside it....the refractive index of that....its density....the source of the liquid.....in how many days is it replenished if it is replenished at all.......its colour and everything else you may know....please its urgent.....
Answer:
Vitreous humour (British spelling) or Vitreous humor (U.S. spelling) is the clear aqueous solution that fills the space between the lens and the retina of the vertebrate eyeball. The solution is 99% water, but has a gelatinous viscosity two to four times that of water. The remaining solutes include salts, sugars, phagocytes, and a network of collagen fibers. Thus, unlike water, it has a refraction index of 1.336[1]. The phagocytic cells are present to remove unwanted debris in the visual field. The primary purpose of the vitreous humor is to provide a cushioned support for the rest of the eye, as well as a clear unobstructed path for light to travel to the retina.

The collagen fibers of the vitreous are held apart by electrical charges. With aging, these charges tend to reduce, and the fibers may clump together. Similarly, the gel may liquefy, a condition known as syneresis, leading to cells and other organic clusters to float freely within the vitreous humor. These commonly lead to floaters which are perceived in the visual field as spots or fibrous strands. Floaters are generally harmless, but the sudden onset of recurring floaters may signify a posterior vitreous detachment (PVD) or other diseases of the eye.

The metabolic exchange and equilibration between systemic circulation and vitreous humor is so slow that vitreous humor is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted, or metabolized from the general circulation.

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Composition
The solution is 99% water, but has a gelatinous viscosity two to four times that of water. The remaining solutes include salts, sugars, phagocytes, and a network of collagen fibres. Thus, unlike water, it has a refraction index of 1.336[1].

Hyaluronic acid was first isolated from vitreous humour.


[edit] Function
The phagocytic cells are present to remove unwanted debris in the visual field. The primary purpose of the vitreous humour is to provide a cushioned support for the rest of the eye, as well as a clear unobstructed path for light to travel to the retina.


[edit] Pathology
The collagen fibres of the vitreous are held apart by electrical charges. With aging, these charges tend to reduce, and the fibres may clump together. Similarly, the gel may liquefy, a condition known as syneresis, leading to cells and other organic clusters to float freely within the vitreous humour. These commonly lead to floaters which are perceived in the visual field as spots or fibrous strands. Floaters are generally harmless, but the sudden onset of recurring floaters may signify a posterior vitreous detachment (PVD) or other diseases of the eye.


[edit] Clinical significance
The metabolic exchange and equilibration between systemic circulation and vitreous humour is so slow that vitreous humour is sometimes the fluid of choice for postmortem analysis of glucose levels or substances which would be more rapidly diffused, degraded, excreted, or metabolised from the general circulation.

A vitrectomy is a surgery to remove some or all of the vitreous humour from the eye.


[edit] External links
http://thebrain.mcgill.ca/flash/i/i_02/i...

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Vitreous humor filling the cavity of eye. It is gelatinous medium.
Lights beam pass through vitreous humor, refract and go on to yellow spot of retina and compose picture .Vitreous content, water, minerals,lisosimes,secretory Iga, sugar...

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The vitreous humor is a clear gel which occupies the posterior compartment of the eye, located between the crystalline lens and the retina and occupying about 80% of the volume of the eyeball. Light initially entering the eye through the cornea, pupil, and lens, is transmitted through the vitreous to the retina.

Vitreous humor has the following composition:

1. water (99%)
2. a network of collagen fibrils
3. large molecules of hyaluronic acid
4. peripheral cells (hyalocytes)
5. inorganic salts
6. sugar
7. ascorbic acid


hyaloid artery
The “hyaloid artery” (a branch of the primitive dorsal ophthalmic artery) extends, in the fetus, from the optic cup of the optic nerve into the vitreous cavity and forward to the lens to aid its development. The hyaloid artery regresses during the last trimester of fetal formation, leaving behind the “Cloquet’s canal” through the vitreous. Sometimes, the hyaloid artery remains after birth and is viewable by a doctor looking into the eye as a “persistent hyaloid artery,” but it rarely is noticeable to the person who has it.

posterior vitreous detachment (PVD)
With age, the vitreous humor changes from a gel to a liquid. As it does so, the vitreous mass gradually shrinks and collapses, separating and falling away from the retina. This is called a “posterior vitreous detachment” (PVD) and is a normal occurrence between ages 40 and 70.

Commonly, a person having experienced a PVD will report seeing flashing lights and/or floaters in his or her field of vision. The flashes of light occur as the vitreous tugs on the sensory layer of the retina as the vitreous is detaching. The floaters—which are cells or debris released when the vitreous detaches—can appear as little dots, circles, lines, cobwebs, or clouds. They especially can be apparent when looking at a bright background, as the light entering the eye casts shadows of the floaters onto the retina. Sometimes a large, single floater actually can obstruct print that is being read. The observance of flashes and floaters can last two or more weeks. Even episodes lasting as long as six months can occur.

It is said that the percent chance of having a vitreous detachment is at least the same as one’s age. However, a PVD may occur earlier than normal in moderately to extremely nearsighted people, as well as in people who have had cataract surgery. A dilated eye exam should be performed to make sure the symptoms are not due to a retinal detachment, which is a much more serious and potentially sight-threatening condition.

floaters (muscae volitantes)
As a posterior vitreous detachment (PVD) occurs—that is, as the vitreous fluid separates from the retina—organic debris or particles known as “floaters” are released. Another name for floaters is “muscae volitantes” (flying flies). Most floaters are merely compressed cells or strands of the vitreous gel which have clumped together so that they are less transparent than the rest of the vitreous. Some floaters are remnants of the hyaloid artery, which usually disintegrates before birth. These types of floaters are harmless.

Floaters sometimes interfere with vision, often during reading, and they can be quite annoying. If a floater appears directly in the line of sight, the best thing to do is to move the eye from side to side or up and down. Doing so can create a current within the internal fluids to move the floater temporarily away from the line of sight. If a floater is suspended in a portion of vitreous humor which is very viscous, it can be very persistent and bothersome. Unfortunately, in most instances, there is nothing to do but learn to tolerate the floater’s presence. Surgical removal is considered only in the most extreme cases.

Usually, the vitreous makes a clean break as it pulls away from the retina. Occasionally, however, the vitreous adheres tightly onto the retina in certain places; and a small, often horseshoe-shaped tear in the retina can result from persistent tugging by the vitreous. Unless the retinal tear is repaired, fluid can seep through this hole into or underneath the retina and cause a retinal detachment, a very serious, sight-threatening condition. As the vitreous membrane tugs on the retina, at points where the two structures remain attached, the tension can cause “flashing” sensations. Occasional flashes of light usually are nothing to be concerned about, unless they increase in frequency and occur in conjunction with a sudden onset of a large number of floaters, in which case a retinal detachment may have occurred.

asteroid hyalosis
Not uncommonly, tiny spherical or disc-shaped, “soapy” globs, can be located in the vitreous of one eye or occasionally both eyes; this is known as “asteroid hyalosis.” When present, these calcium-containing lipid complexes usually are suspended throughout the vitreous. Usually, these “asteroids” are not observable by a person who has them, and they normally do not cause any decrease in vision, since light generally passes through them unaffected. Rarely, however, if the asteroids coalesce on the visual axis, at or near the nodal point behind the lens, there can be a profound decrease in vision. In such a case, removal of the asteroids, via a vitrectomy, is an option to restore vision.

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