Dermis of the eye
Definition - What is the dermis?
The eye consists of the outer skin of the eye, which can be divided into two sections - the opaque dermis and the translucent cornea. The main part of the eye skin is made up of the thick dermis, too Sclera called, formed.
The white dermis consists of firm connective tissue and covers almost the entire eyeball and gives it its shape. Due to the high proportion of collagen and elastic fibers, the dermis gives the eyeball its stability and forms the white of the eye.
At the front of the eye, the dermis goes into the translucent, vascular cornea (Cornea) above. The cornea is more curved than the dermis. Because of this curvature or curvature, the cornea participates in the refraction of light and bundles incident light rays.
So that you get a better idea of all layers of the eye, editorial team has sketched a picture for you: Figure of the eye
The dermis can be divided into three different layers under the microscope:
- In the one on the outside Lamina episcleralis
- In the middle in the Substantia propria
- Located inside in the Lamina fusca sclerae
The lamina episcleralis is responsible for the blood supply, and accordingly there are numerous blood vessels in it. The blood vessels, i.e. the capillaries (smallest blood vessels) go into a network of elastic and collagen fibers. This layer thus forms a loose covering tissue. In addition, immune cells, namely the lymphocytes and macrophages, can be found in the lamina episcleralis.
The substantia propria is located in the middle and consists of tight connective tissue and collagen fibers that are strongly intertwined and are 0.5 to 6 µm thick. This layer is also called the connective tissue layer, which has hardly any blood vessels.
The inner lamina fusca sclerae borders on the choroid membrane or merges into it. This lamina is formed from a thin layer of fibril bundles arranged like scissors. Fibroblasts and melanocytes are also found in this layer.
Are you interested in the structure of the eye and would like to know more about it? Read about this under: Anatomy of the eye
How thick is the dermis?
The thickness of the dermis varies depending on the region in the eye. In addition, the thickness of the dermis depends on the size of the eyeball, the larger it is, the thinner the dermis.
It can be from 0.3 to 1 mm. At its central point, it is about 0.6 mm thick. At the border areas to the transparent layer, the cornea, the dermis covers the cornea like a roof tile.
At the exit point of the optic nerve, the dermis has a recess that is approx. 3.5 mm in size, through which the nerve pulls.
Function of the dermis
The main function of the dermis is to protect the eye or the sensitive interior of the eye.
In particular, the vulnerable choroid, which is located below the dermis, is protected by it. It needs this protection because it is responsible for the blood supply to the eye and therefore carries many veins.
In order not to disturb this blood flow, there are numerous openings in the dermis, which, however, do not affect its protective function.
The protective mechanism is diverse and begins with the buffering of mechanical effects on the eye.
Furthermore, the dermis prevents solar radiation from damaging the eye, as direct radiation is prevented.
In addition, the dermis has the function of giving the eye its shape. The pressure from the dermis against the intraocular pressure creates the spherical shape of the eyeball.
Furthermore, the dermis has the function of being able to display the general state of health of the patient. The color of the normally white dermis plays a special role here, as it can be colored differently depending on the disease.
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CLINIC: Diseases of the dermis
What is dermatitis?
A dermatitis, too Scleritis called, is an inflammation in the eye that can occur both on one side and on both sides. It is also possible that a chronic or recurrent course takes place.
It is a rather rare eye disease, but it should not be taken lightly, as in the worst case it can damage eyesight. For this reason, it should always be treated by an ophthalmologist.
People between the ages of 40 and 60 are particularly common, with the inflammation occurring more often in women than in men.
A distinction is made between anterior and posterior dermis inflammation. The front is easy to see from the outside, but the rear has to be diagnosed with the help of an ultrasound device.
Viruses or bacteria are rarely the cause of dermatitis; it is usually an autoimmune disease. Examples of autoimmune diseases are rheumatism or Crohn's disease.
Those affected complain of severe, stabbing eye pain, which is often felt in the form of tenderness. This pain can be so severe that it does not allow the patient to rest all day and all night.
In addition, swelling of the dermis is also a symptom. This swelling, which is visible from the outside, also causes the pain.
In addition, discoloration of the dermis occurs when there is inflammation. The white color gives way to a dark red to bluish discoloration. In addition, there is usually blurred vision, or limited vision, due to increased tear flow.
Find out all about the topic here: The dermis of the eye.
Red dermis - where does it come from?
A red dermis or reddening of the eyes is usually caused by the fact that the blood vessels of the conjunctiva and dermis are enlarged and supplied with more blood. For this reason, the actually whitish to transparent dermis appears red because the choroid is located directly below it.
The reddening is easy to see in the front area of the eye and can appear on both sides as well as on one side.
Redness can have a harmless background that is easy to fix, such as irritation or overexertion. The reasons for this are mostly due to lack of sleep, dust, dry air, cosmetics, air conditioning, strong sunlight, etc.
If, in addition to the reddening of the eyes, there is also permanent tearing or constant itching, which is also expressed in pain, you should consult an ophthalmologist, as the dermis may have become inflamed.
What is behind a yellow leather skin?
With a yellow dermis, which is immediately recognizable from the outside, the eye itself is not directly affected, but organs in the body.
Thus, a yellow-colored dermis is an early sign of disease. It can be colored differently from a slight yellow tinge to a deep yellow discoloration.
The yellow-brownish bile pigment bilirubin is responsible for the discoloration. It arises from the breakdown of hemoglobin, which turns the blood red. Bilirubin is not soluble in water and is converted in the liver in such a way that it is now water-soluble. Ultimately, most of it is excreted in the stool via the biliary tract and the intestine.
If there is a disturbance in this process, the bilirubin cannot be excreted properly and is deposited in the blood. As a result of this accumulation in the blood, not only the dermis but also the normal skin and mucous membranes turn yellow.
Typical diseases for a yellow dermis are diseases of the liver, such as hepatitis or alcoholic diseases. In addition, the bile can also be affected, undernourishment or malnutrition.
If the respective disease is cured successfully, the dermis will get its original white color again.
Bruising of the dermis
Through a mechanical force from the outside on the eye, such as a punch, a ball, a stone, etc. or by being stubborn, the eye can be bruised or squeezed. It is possible that the eye sustains a serious injury from this, which can affect the eyelid, conjunctiva, leather and cornea.
A bruise is usually visible from the outside, as the eyelid is usually affected and swells, making it difficult to open the eyes.
This symptom, known as "violet", says nothing about the severity of the damage to the dermis, which is why an ophthalmologist should be consulted if necessary.
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Recommendations from the editorial team
These topics could nicely complete the topic of "leather skin":
- Structure of the eye
- Cornea of the eye
- Conjunctiva: structure and function
- Retina of the eye
- Eye diseases in humans - which ones are there?