Synonyms in a broader sense
Medical: Corpus vitreum
Definition
The vitreous body is a part of the eye. It fills a large part of the posterior chamber of the eye and is primarily responsible for maintaining the shape of the eyeball (bulbus oculi). Changes to the vitreous body can lead to visual disturbances in the broader sense.
Anatomy Vitreous body
The vitreous body is a spherical, transparent structure inside the eye. To the front it is limited by the lens, to the back by the retina. It consists of about 98% water, the remaining 2% are collagen fibers and hyaluronic acid molecules.
Hyaluronic acid belongs to the glycosaminoglycans (abbreviation: GAG, polysaccharides) which together form part of the extracellular matrix of the body. They therefore fill the space between the cells. Due to their structure, many of the glycosaminoglycans – including hyaluronic acid – have the ability to bind a lot of water, they have a high water-binding capacity. Thus their environment is often of jelly-like consistency. So is the vitreous body of the eye.
Function of the glass body
Each ray of light passes through the entire vitreous body after being refracted and bundled at the cornea (cornea) and lens – depending on the angle of incidence. It then falls on the retina behind the vitreous where the photoreceptors are located. These convert light stimuli into electrical signals, which are the beginning of a complex signal cascade that reaches into the central nervous system and at its end ensures the creation of the image we see. The vitreous body itself, with its spherical shape, which fills a large part of the posterior chamber of the eye, is primarily responsible for maintaining the round shape of the eyeball. In addition, its transparency is a prerequisite for the unhindered passage of incoming light rays to the retina.
Changes and diseases
Serious diseases of the vitreous body are rather rare. Nevertheless, there are some processes in which it can lead to vision impairment. However, this rarely changes the visual acuity (visual acuity) per se, but rather leads to disturbing spot or speckle vision in the visual field of the affected eye.
In the case of vitreous detachment, the posterior part of the vitreous detaches itself partially from the retina. Depending on the severity, this can lead to “spot or streak vision” of the affected eye. In the case of a vitreous detachment, there is a risk of simultaneous retinal detachment, which is an ophthalmologic emergency.
A clouding of the vitreous usually leads to the small dots known as “mouches volantes” (French: flying mosquitoes), which move through the field of vision as if floating. To a certain degree this phenomenon is physiological (i.e. normal) and can also occur at a young age. In these cases it does not affect the visual acuity.
A significant increase in the number of volantes may be an indication of a pathology, such as a vitreous detachment or a vitreous hemorrhage, and should then be clarified by a doctor. Vitreous shrinkage is a slowly progressing reduction of the vitreous body. It is caused by degenerative processes, which can be different for each person.
The vitreous body loses its shape with age. Due to the agglutination of stabilizing fibers, the vitreous body can no longer store enough water to completely fill the interior of the eye. If the vitreous body shrinks more strongly, this can lead to vitreous detachment.
Since the retina is no longer sufficiently stabilized, it can subsequently detach. Even if the vitreous is glued to the retina, it can damage it through its shrinking. However, this is the exception.
Often a shrinking of the vitreous body is not noticed. Mostly, so-called “Mouches volantes” (French: flying mosquitoes) occur, which can be perceived as disturbing. They are normally harmless.
However, if they appear suddenly or in larger quantities, they can indicate damage to the eye. Flashes of light caused by an irritation of the retina should be examined by an ophthalmologist. The same applies to the so-called “sooty rain”.
These are many small dark spots that are suddenly perceived. They can be signs of retinal damage. With age, the vitreous body shrinks and changes its consistency.
While it still has the consistency of thick pudding in children, it becomes more and more fluid with age.The reason for this is a separation of stabilizing fibers and water, which makes up about 98% of the glass body. The vitreous body develops an irregular shape that no longer fits smoothly to the retina and shrinks slightly. Free water collects in the resulting gaps.
A gap is formed between the vitreous body and the retina. At the front of the eye, the vitreous body is more firmly fixed, which means that in most cases no detachment can take place here. The vitreous detachment is widespread and in most cases harmless.
It occurs in about 65% of all people over 60 years of age. Those affected often complain about “mouches volantes”. These are serpentine or punctiform shapes that are mainly seen when looking at bright surfaces.
In addition, flashes of light can be perceived by irritation of the retina. Although vitreous detachment is usually harmless, it can lead to more threatening diseases such as retinal detachment. More about this:
- Vitreous detachment
With increasing age the vitreous body degenerates.
The normally evenly distributed support fibers separate from the water content and clump together. This results in 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 shapes are called “Mouches volantes” (French: flying mosquitoes). These are usually snake-like lines or dots. The visual acuity is not affected.
Mouches volantes are mainly perceived against a light background. Even people with a non-clouded vitreous body sometimes see these shapes. 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 mouches volantes are perceived as very disturbing or if complications are imminent, surgery may be advisable. In the so-called vitrectomy, parts of the vitreous body are surgically removed and replaced with saline solution. A modern method is laser vitreolysis.
Both techniques have advantages and disadvantages and must be discussed in detail with the treating physician. The actual vitreous body has no blood vessels. The vitreous hemorrhage is therefore a bleeding into the vitreous.
The blood comes from the vessels of the surrounding eye. If blood spreads in the body, it follows the path of least resistance. While the eye is enclosed from the outside by the sinewy dermis, the vitreous body is soft and deformable.
Inflowing blood can therefore spread almost unhindered. Since the vitreous body is hardly penetrated 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 the case of severe vitreous hemorrhages, the ability to see can be severely impaired as a result. The possible causes of a vitreous hemorrhage are manifold. It is often caused by an external force acting on the eye, for example a blow.
It can also be the consequence of inflammatory diseases if eye vessels are damaged. High blood pressure also damages the vessels of the eye. In the rare Eales syndrome, vitreous haemorrhages occur, among other things. No exact causes are known for this disease.