Synonyms in the broader sense

Medical: Corpus vitreum

English: vitreous

definition

The vitreous is a part of the eye. It fills most of the posterior chamber of the eye and is primarily responsible for the preservation of the eyeball ( bulbus oculi ). Changes in the vitreous can lead to visual disturbances in the broader sense.

Anatomy vitreous body

The vitreous is a globular, transparent structure inside the eye. Forwards it is limited by the lens, back through the retina ( retina ).
It consists of about 98% water, the remaining 2% make collagen fibers and Hyaluronsäuremoleküle. Hyaluronic acid is one of the glycosaminoglycans (abbreviation: GAG, polysaccharide) which together form part of the extracellular matrix of the body. So they fill in the space between the cells.
Many of the glycosaminoglycans - including hyaluronic acid - have the ability to bind a lot of water due to their structure, they have a high water binding capacity. So their environment is often of jelly-like consistency.
So too the vitreous body of the eye.

Figure: Horizontal section through the left eyeball, seen from below
  1. Cornea - Cornea
  2. Sclera - Sclera
  3. Iris - iris
  4. Radiation body - Corpus ciliare
  5. Choroid - Choroidea
  6. Retina - Retina
  7. Front chamber of the eye -
    Camera anterior
  8. Chamber Angle -
    Angulus irodocomealis
  9. Rear Eye Chamber -
    Camera posterior
  10. Eye Lens - Lens
  11. Vitreous humor - corpus vitreum
  12. Yellow spot - macula lutea
  13. Blind spot -
    Discus nervi optici
  14. Optic nerve (2nd cranial nerve) -
    Nervus opticus
  15. Main line - Axis opticus
  16. Axis of the eyeball - Axis bulbi
  17. Lateral straight eye muscle -
    Musculus rectus lateralis
  18. Inner straight eye muscle -
    Musculus rectus medialis

Function of the vitreous

Each light ray traverses the entire vitreous body after it has been refracted and bundled on the cornea ( cornea ) and lens, depending on the angle of incidence.

He then falls on the behind the vitreous retina in which lie the photoreceptors. These convert light stimuli into electrical signals, which are the beginning of a complex signal cascade, which reaches to the central nervous system to provide at its end for the formation of the image we see.
The vitreous itself is responsible for the preservation of the round shape of the eyeball due to its spherical shape with which it fills most of the posterior chamber of the eye. In addition, its transparency is a prerequisite for the incident rays of light to fall freely on the retina.

Changes and diseases

Serious diseases of the vitreous are rather rare. Nevertheless, there are some processes in which it can lead to a disturbance of the view.
However, this rarely changes the visual acuity ( visual acuity ) itself, but rather it comes to disturbing points or spots in the field of vision of the affected eye. In case of a vitreous detachment, the posterior part of the vitreous partially separates from the retina. This can - depending on severity - lead to "scores or Schlierensehen" of the affected. In vitreous detachment, there is a risk of simultaneous retinal detachment, which is an ophthalmological emergency.

A clouding of the vitreous body usually leads to the small dots which are called "mouches floats" (French - flying mosquitoes) which move as though floating through the field of vision. To a certain extent, this phenomenon is physiological (ie normal) and can occur even at a young age.
It does not affect visual acuity ( visual acuity ) in these cases. On the other hand, a significant increase in floaters can be indicative of a pathology, such as vitreous detachment or vitreous haemorrhage, and should be clarified by a doctor.

Vitreous shrinkage

Vitreous shrinkage is a slow progressive reduction of the vitreous body. Cause are degenerative processes, which can turn out differently with each humans. The vitreous loses its shape with age. Due to the clumping of stabilizing fibers, the vitreous body can no longer store enough water to completely fill the inside of the eye.

If the vitreous body shrinks more strongly, vitreous detachment may occur. Since the retina is no longer sufficiently stabilized, it can detach in the sequence. Even if the vitreous is glued to the retina, it can damage it by shrinking. This is the exception.

Often a vitreous shrinkage is not perceived. Most of the time it comes to so-called "floaters" (French: flying mosquitoes), which can be distracting. They are usually harmless. However, if they appear suddenly or in large quantities, they may indicate damage to the eye. Flashes of light caused by irritation of the retina should be examined by the ophthalmologist. The same applies to the so-called "soot rain". These are many small dark spots that are suddenly perceived. They can be signs of retinal damage.

Vitreous detachment

As you age, the vitreous shrinks and changes its consistency. While he still has about the consistency of thick pudding in the child, he gets smoother with older age. The reason for this is a segregation of stabilizing fibers and water, which makes up about 98% of the glass body.

The vitreous body develops an irregular shape, which no longer fits smoothly to the retina and shrinks easily. In the resulting columns, free water collects. A gap forms between the vitreous and the retina. At the front of the eye, the glass body is fixed more firmly, whereby here usually no detachment can take place.

Vitreous detachment is widespread and in most cases harmless. It occurs in about 65% of all people over 60 years. Often sufferers complain about "mouches floaters". These are serpentine or punctiform forms, which are mainly seen when viewing bright surfaces. In addition, flashes of light may be caused by irritation of the retina.

Although the glass body lift is usually harmless, it can lead to more threatening diseases such as retinal detachment.

More about this:

  • Vitreous detachment

Vitreous opacity

As you age, the vitreous degenerates. The normally uniformly distributed support fibers separate from the water content and clump together. This creates denser structures that can absorb light. Since the vitreous body lies directly in front of the retina, these light-tight forms are perceived by the affected person in the field of vision. The perceived forms are called "mouches volantes" (French: flying mosquitoes). These are mostly serpentine lines or dots.

Visual acuity is not affected. Moques floaters are perceived above all against a light background. Even people with glassy bodies that are not clouded can sometimes see these forms. However, a sudden increase in the number and density of these phenomena should be clarified by an ophthalmologist, as they can also be harbingers of serious diseases.

If the floaters are perceived as very disturbing or threaten complications, surgery may be useful. In so-called vitrectomy, parts of the vitreous are surgically removed and replaced with saline. A modern method is laser vitreolysis. Both techniques have advantages and disadvantages and must be discussed in detail with the attending physician.

Vitreous hemorrhage

The actual vitreous body has no blood vessels. The vitreous hemorrhage is therefore a hemorrhage into the vitreous humor. The blood comes from the vessels of the surrounding eye.

If blood spreads in the body, it follows the path of the least resistance. While the eye is surrounded by the sinewy dermis from the outside, the vitreous body is soft and malleable. Inflowing blood can therefore spread almost unhindered.

Since the vitreous body is scarcely crossed by nerve endings, the vitreous hemorrhage is often not painful. The affected patients usually complain of reddish discoloration and clouding of their visual field. In strong vitreous hemorrhages, the vision can be severely limited.

The possible causes of vitreous haemorrhage are manifold. Often it is a force on the eye from the outside, for example, a blow. In addition, it can be the result of inflammatory diseases when eye vessels are damaged. High blood pressure also damages the vessels of the eye. In the rare Eales syndrome, among other things, vitreous hemorrhages occur. There are no known exact causes for this disease.


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