Sclera of the eye: structure, functions, diseases and treatment. The sclera of the eye - what is it, what functions does it perform and what pathologies can the human eye have?

The sclera, or tunica albuginea, is a segment of the fibrous membrane of the eye, occupying about 95% of the total area, with a radius of curvature of 11 mm. Above, below, outside and inside, approximately 6-7 mm from the limbus, as well as in the equator region, the tendons of the external rectus and oblique muscles of the eye are woven into the sclera. The sclera consists of several layers (from the outside to the inside):

1) episclera (suprascleral plate) - outer loose layers of the sclera, merging with the subconjunctival tissue and rich in vessels that form the superficial (plexus episcleralis) and deep (plexus scleralis) vascular networks. In the formation of these networks, the anterior ciliary arteries and the posterior short ciliary arteries participate in the formation of these networks. Those areas of the episclera that are located anterior to the attachment sites of the rectus oculi muscles are richest in blood vessels. Here, 7 anterior ciliary arteries pass from the muscles to the surface of the eyeball - one artery from the external rectus muscle and two each from the remaining rectus muscles (Heymann V. et al., 1985) and, conversely, the corresponding veins approach the muscles from the eye. For this reason, cutting the rectus muscles or burning out the vessels is fraught with the development of necrotic processes in the anterior part of the eye. The anterior ciliary arteries enter the ocular cavity approximately 1 mm posterior to the scleral spur. The diameter of the anterior ciliary arteries is 0.3 mm (Sudakevich D.I., 1971).

Numerous connective tissue strands connect the episclera to Tenon's capsule, so that the entire space between the capsule and the eyeball is filled with loose episcleral tissue.

2) the sclera itself - consists of collagen and elastic fibers that form bundles that have a predominantly meridional and equatorial direction. The thickness of the fibrils ranges from 30 to 220 µm. In the spaces between them there are flattened fibrocytes and fibroblasts, the processes of which form syncytium. Young people have more cellular elements. The deeper the collagen fibers are located in its thickness, the greater their strength, the higher the overall density of scleral tissue. Around the optic nerve, the outer 2/3 of the fibers have a circular direction and merge with the longitudinal fibers of the dura mater of the optic nerve (in this place the sclera has a thickness of 1-1.5 mm). The inner 1/3 of the fibers having a longitudinal arrangement forms the cribriform plate (lamina cribrosa). The biomechanical properties of the sclera are determined by the content and distribution of biopolymers such as collagen, elastin, glycosaminoglycans, and glycoproteins. The modulus of elasticity of the sclera in adult eyes ranges from 1.5 kg/mm ​​2 in the posterior region to 3.0 kg/mm ​​2 in the anterior region. The sclera of newborns, as well as young children, is characterized by a relatively more uniform distribution of thickness and biopolymer content. By 4-5 years, differentiation of the sclera sections occurs: the posterior pole thickens, and the equator region becomes relatively thinner. Accordingly, the posterior section contains more collagen and elastin than the equator region (Savitskaya N.F. et al., 1982). A decrease in the content of collagen, especially soluble fractions, in the posterior pole leads to a decrease in the mechanical strength of this section and stretching under the influence of loads withstand by the normal sclera - progressive myopia develops (Avetisov E. S. et al., 1971).

3) brown plate (lamina fusca) - consists of thinned scleral fibers with an admixture of elastic tissue and chromatophores. The inner surface of the sclera is covered with endothelium.

The thickness of the sclera is approximately 0.54-0.63 mm from the limbus to the equator, behind the attachment points of the rectus muscles the sclera thins to 0.3 mm, posterior to the equator the thickness of the sclera again gradually increases to 0.6 mm, and in the region of the posterior pole it increases up to 0.8-1.5 mm due to the weaving of fibers of the optic nerve sheath into it (Zatulina N.I. 1988). In the area of ​​the central fovea, the thickness of the sclera is 0.72 mm (Emi K. et al., 1983).

The thinnest places of the sclera, most often affected by pathological processes (trauma, increased IOP) are:

places immediately posterior to the insertions of the rectus muscles (0.3-0.5 mm),

lamina cribrosa (formed by just the inner one-third of the sclera),

limbus - the junction of the cornea and sclera,

emissaries - the places of entry and exit of intraocular vessels and nerves (the areas with the most such places are the anterior section at the limbus, the equator and the posterior pole in the area of ​​exit of the optic nerve).

The above areas of the sclera are often the site where intraocular neoplasms extend beyond the eyeball.

The sclera itself is poor in its own vessels, but all vascular trunks intended to supply blood to the vascular tract pass through it. The perineural and perivascular spaces around the vessels and nerves passing through the sclera are loosely filled with thin suprachoriodal plates that fix the nerve and vascular trunks. The sclera is fed by the anterior and posterior ciliary vessels, which form a scleral network that sends branches into the sclera.

Sensitive innervation of the sclera is carried out by the first branch trigeminal nerve(long and short ciliary nerves). The sclera receives sympathetic fibers from the cervical sympathetic trunk.

The human eye is a complex natural optical device through which 90 percent of the information for the brain comes. The sclera is a functional element.

The condition of the shell indicates eye diseases and other pathologies of the body. In order to recognize the disease in time, you should understand what sclera is.

Shell structure

The sclera is the outer tunica albuginea made of dense connective tissue that protects and holds the internal functional elements.

The white of the eye consists of bundle-shaped, randomly arranged collagen fibers. This explains the opacity and different densities of the fabric. The thickness of the shell ranges from 0.3 to 1 mm; it is a capsule of fibrous tissue of unequal thickness.

The white of the eye has a complex structure.

1. The outer layer is a loose tissue with a branched vascular system, which is divided into deep and superficial vascular networks.
2. The sclera itself, consists of collagen fibers and elastic tissues.
3. The deep layer (brown plate) is located between the outer layer and the choroid. Consists of connective tissue and pigment cells - chromatophores.

The posterior part of the eye capsule has the appearance of a thin plate with a lattice structure.

Functions of the scleral membrane

The fibers of the cover are arranged chaotically, protecting the eye from the penetration of sunlight, which ensures effective vision.

The scleral region performs important physiological functions.

1. The eye muscles, which are responsible for eye mobility, are attached to the tissues of the capsule.
2. The ethmoidal arteries of the posterior part penetrate the sclera.
3. A branch of the ophthalmic nerve approaches the eyeball through the capsule.
4. The capsule tissue serves as the shell.
5. Whirlpool veins emerge from the eye through the protein body, which provide the outflow of venous blood.

The tunica albuginea, due to its dense and elastic structure, protects the eyeball from mechanical injuries, negative factors environment. Protein serves as a scaffold for muscular system, ligaments of the organ of vision.

What should the sclera of a healthy person look like?

The scleral cover normally has White color with a bluish tint.

Due to their small thickness, the child has blue sclera, through which the pigment and vascular layer are visible.

A change in color (dullness, yellowness) indicates problems in the body. The presence of yellowish areas on the surface of the white indicates eye infections. A yellow tint may be a symptom of liver disorders, hepatitis. In infants, the covering is thinner and more elastic than in adults. Slightly blue sclera is normal at this age. In older people, the cover thickens, becomes yellow due to the deposition of fat cells, and becomes loose.

Blue sclera syndrome in humans is caused genetically or by a violation of the formation of the eyeball in the prenatal period.

Changing the type of protein is a justified reason for visiting a doctor. The condition of the integument affects the functioning of the visual system. Diseases of the sclera are divided into congenital and acquired.

Congenital pathologies

Melanosis (melanopathy)- a congenital disease that is expressed by pigmentation of the skin with melanin. Changes appear in the first year of life. The baby's whites have a yellowish tint, and pigmentation appears in the form of spots or stripes. The color of the spots may be gray or light purple. The cause of the anomaly is a violation of carbohydrate metabolism.

Blue sclera syndrome often accompanied by other eye defects, anomalies musculoskeletal system, hearing aid. The deviation is congenital. Blue sclera may indicate iron deficiency in the blood.

Acquired diseases

Staphyloma is an acquired disease. It manifests itself as thinning of the membrane, protrusion. It is a consequence of eye diseases associated with destructive processes.

Episcleritis is an inflammation of the surface of the integument, accompanied by nodular seals around the cornea. It often goes away without treatment and may recur.

Scleritis is an inflammatory process affecting the inner layers of the scleral body, accompanied by pain. A rupture of the eye capsule may form at the site. The disease is accompanied by immunodeficiency and tissue swelling.

Necrotizing scleritis- develops as a consequence of long-term rheumatoid arthritis. It manifests itself as thinning of the membrane and the formation of staphyloma.

Diseases of inflammatory origin can occur as a result of infections and disruptions in the functioning of organs of the human body.

Timely contact with a doctor helps to promptly identify diseases of the sclera, establish the cause and begin treatment.

The sclera covers the outside of the eyeball. It belongs to the fibrous membrane of the eye, which also includes. However, what distinguishes the sclera from the cornea is that it is considered an opaque tissue because the collagen fibers that form it are arranged randomly.

Sclera of the eye

The main function of the sclera is to provide high-quality vision. This occurs due to the fact that light rays simply cannot penetrate the scleral tissue, which would cause blinding. The main functions of the sclera also include protecting the inner membranes of the eye from external damage and supporting the structures and tissues of the eye that are located outside the eyeball:

• oculomotor muscles;
• ligaments;
• vessels;
• nerves.

Being a dense structure, the sclera is also involved in maintaining an optimal level of intraocular pressure and the outflow of intraocular fluid through the Helmet canal.

Deeper layers

The sclera itself consists of fibrocytes and collagen. These components are quite important for the body as a whole. The first group of substances takes an active part in the production of collagen itself, as well as in the separation of its fibers. The inner, very last layer of tissue is called the “brown plate”. It contains a huge amount of pigment, which determines the specific shade of the eye shell.

Certain cells called chromatophores are responsible for coloring such a plate. They are contained in the inner layer in large quantities. The brown plate most often consists of a thin fiber of the sclera, as well as a slight admixture of the elastic component. On the outside, this layer is covered with endothelium.

Burst vessels in the sclera

All blood vessels and nerve endings that are located in the sclera pass through emissaries - special channels.

Now let's take a closer look at each layer of the sclera:

1. The episcleral layer has a good blood supply and is connected to the outer fairly dense teno capsule of the eye. The anterior sections of the episclera are considered to be the richest in blood flow, since blood vessels pass to the anterior section of the eyeball in the thickness of the straight lines oculomotor muscles.
2. The scleral tissue consists of dense collagen fibers, between them there are cells, so-called fibrocytes, that produce collagen.
3. The inner layer of the sclera is externally described as a brown plate, as it contains a lot of chromatophores.

What functions does the sclera perform?

The functions of the sclera are quite diverse. The first of them is due to the fact that collagen fibers inside the tissue are not arranged in a strict order. Because of this, light rays are unable to penetrate the sclera. This fabric protects the retina from intense exposure to light and sunlight. It is thanks to this function that a person is able to see quite well.

This fabric is intended not only to protect the eyes from intense light, but also from various damage. Including those that are physical or chronic in nature. In addition, the sclera also protects the organs of vision from the effects of harmful environmental factors.

Also, some experts highlight another important function of this tissue. Conventionally, it can be called a frame structure. It is the sclera that is a high-quality support and reliable element for attaching ligaments, muscles and other components of the eye.

Methods for diagnosing scleral diseases

The most common diagnostic methods include:

• visual inspection;
• biomicroscopy – a study carried out under a microscope;
• ultrasound diagnostics.

Congenital diseases of the sclera

The sclera has a fairly simple structure, but there are certain diseases and pathologies of the sclera. We should also not forget that such tissue performs important functions and if any disturbances occur, the functioning of the visual apparatus as a whole sharply deteriorates. Diseases can reduce visual acuity and lead to irreparable consequences. Diseases of the sclera can be not only congenital, but also caused by various irritants.

A pathology called blue sclera can often occur as a result of genetic predisposition and improper formation of the tissues connecting the eyeball in the womb. The unusual shade occurs due to the small thickness of the layers. The pigment of the eye shell is visible through the thin sclera. This pathology can often occur with other eye anomalies and with disturbances in the formation of hearing organs, bone tissue and joints.

Most often, diseases of the sclera are congenital and include::

1. Melanosis of the sclera.
2. Congenital disorders of collagen structure, for example, in Van der Hewe's disease.

Melanosis is a serious problem, so you should immediately contact an ophthalmologist.

Acquired ailments

Inflammation of the sclera is quite common. Diseases that may appear as a result of such a process deserve special attention. The development of such ailments in the future can provoke not only general disruptions in the functioning of certain systems human body, but also infections.

The main symptoms include:

1. Staphylomas of the sclera.
2. Excavation of the optic nerve head is observed with.
3. Episcleritis and scleritis are inflammations of the scleral tissue.
4. Scleral ruptures.

Quite often, pathogenic organisms penetrate the tissues of the outer eye membrane with the flow of lymph or blood. This is the main cause of the inflammatory process.

Now you know what the sclera is and what diseases of this tissue exist. Treatment of all her ailments begins with diagnosis and consultation with a doctor. Only a qualified specialist can prescribe treatment for the disease after identifying all the symptoms. If scleral diseases develop, it is recommended to immediately contact an ophthalmologist. The specialist, in turn, must conduct a series of studies. After the diagnosis is made, therapy is prescribed.

If the disease was caused by a disorder in other body systems, then treatment will be aimed at eliminating the underlying cause. Only after this will measures be taken to restore vision. We hope this information was useful and interesting.

The sclera of the eye is the opaque outer layer of the eye. The sclera occupies the largest area of ​​the eye and has a dense composition. The sclera of the eye has different densities in different areas.

The thickness of the sclera also varies and ranges from 0.3 to 1 mm; in children it is very thin and increases over time.

Describing the structure of the sclera of the eye, three layers are distinguished. This is the outer layer, that is, the episclera, the sclera itself and the brown plate or inner layer.

The structure of the sclera of the eye

Outer layer (Episclera)– well supplied with blood, the vascular network is divided into superficial and deep. The best blood supply occurs in the anterior sections, because the vessels approach the anterior section of the eye, located in the thickness of the rectus extraocular muscles.

The sclera itself- just like it consists of collagen fibers, the space between which is occupied by fibrocytes - producing collagen.

Inner layer or brown plate– consists of thinned scleral fibers and elastic tissue. Fibers contain pigment-containing cells on their surface - chromatophores. These cells give the inner surface of the sclera a brown tint.

The thickness of the sclera contains several through channels that play the role of conductors for blood vessels and nerves, both entering and exiting the eye. The anterior edge of the inner side of the sclera has a so-called groove measuring 0.8 mm. The ciliary body is attached to the posterior edge of the groove, and its anterior edge is adjacent to Descemet's membrane. The main part of the groove is occupied by the trabecular diaphragm, above which is Schlemm's canal.

Due to the fact that the sclera of the eye is connective tissue, it is susceptible to the development of pathological processes that occur in systemic connective tissue diseases or collagenoses.

In those places where the sclera is thinned, protrusions (formations) may occur - the so-called staphyls. In addition, there may be excavation (deepening), which is observed with glaucoma. Ruptures of the sclera also occur in its thin part, most often this occurs between the areas of attachment of the extraocular muscles.

Functions of the sclera

Protective;
- Support.

The main function of the sclera, of course, is protective - it protects the membranes of the eye located inside from various external damage. Also, the sclera does not allow light rays to pass through, which would lead to blinding; due to this, high-quality vision is achieved.

The sclera is a support for the tissues of the eye and its internal and external structures, which are located outside the eye - these are vessels, nerves, ligaments, etc.

In addition, the sclera of the eye takes part in the maintenance, namely, in the outflow through the Schlemm canal.

The opaque part of the fibrous membrane is the sclera of the eye. It covers 85% of all surfaces and is primarily responsible for transmitting visual information to the brain. Its structural features provide a wide range of functions. With anomalies and the development of pathologies, there is a risk of vision loss. Problems with the sclera cause a number of characteristic symptoms, if present, you should consult a doctor. Treatment depends on the current disease and the stage of its development, in most cases it is applied drug treatment of a local nature.

Anatomy of the sclera

The sclera is the white membrane of the eye, located on the outside and, together with the cornea, represents fibrous tissue. Reaching the iris, it forms a dense protective ring. According to its physical characteristics, it has a white color and an opaque structure, due to which a person has vision. This is a fairly dense tissue of several layers; normally the thickness of the sclera reaches up to 1 mm. Despite this structure, the protein membrane of the eyeball can stretch, but this property decreases with age.

Shell structure

Density is ensured due to anatomical features. The structure of the sclera is a very complex process. The main component is collagen, it is arranged in a chaotic manner, thus causing the opacity of the eye. Full functionality is possible thanks to the multi-layered shell, with the layers of the sclera differing in composition and density:

The shell has a very complex and intricate structure.

• Outer layer. The thinnest ball, filled with a large number of blood vessels.
• Middle layer. It is also called scleral and contains the maximum amount of collagen.
• Inner layer. It is a connective tissue in combination with the pigment part.

The visible part of the sclera is only the top layer, the subsequent ones are located inside, but when depleted, protrusion is possible. This process is observed in ophthalmic pathologies.

What functions does it perform?

The versatility of the shell is ensured by its complex structure. Each of the 3 layers plays its role and only a holistic effect guarantees full vision. All functions of the white membrane of the eye are quite diverse. First of all, we are talking about protecting the pupil from external damage. The sun has a negative effect on the condition of the eye. It is due to the refraction of light in the shell that the pupil does not dazzle and an image appears. In addition, the sclera performs the following functions:

The sclera makes it possible to move our eyes in the direction we need.

• Untangles with fastenings for the vascular and muscular apparatus.
• Provides blood outflow through venous branches.
• Responsible for eye mobility.
• Conducts moisture through the venous sinus of the sclera.
• Provides safe passage of the nerve to the eyeball.

What does healthy sclera look like?

Distinguish sick condition The protein sphere can be distinguished from a healthy one by color. In infancy, the sclera is thin, so the membranes appear blue. This condition is not considered pathological and goes away on its own over time. What color of proteins in an adult may indicate the genetic nature of the problem, dystrophic changes formed at the intrauterine level.

Yellowness of the sclera indicates possible pathologies. At the same time, the shell looks dull and cloudy. Such changes may indicate the impact of an infection. Lesions are not only local; kidney disease affects the color of the proteins. In old age, fat cells may be present in large quantities in the eyes, and they can change color to yellow.

Diseases

The organ is susceptible to inflammatory processes that are provoked by bacteria.

Pathologies that develop in the eyes at the level of the sclera are most often of an inflammatory nature, provoked by infections. However, primary sources are not always located directly in the organ. Painful manifestations in the membrane of the eye can only act as symptoms of the main processes. First of all, the ophthalmologist looks for the main diseases of the sclera, these include the following:

• Scleritis. An inflammatory pathology in which the inner layers of the membrane are affected.
• Staphyloma. The disease is caused by destructive processes, as a result of which the membrane is depleted.
• Episcleritis. Damage to the upper layer, accompanied by the formation of nodules.

Developmental anomalies

Congenital pathological forms pose a significant danger; they are difficult to diagnose and do not always respond to conservative treatment.

These include blue sclera syndrome. This color may indicate insufficient iron in the blood. Often such a disease is not a single developmental deviation; other pathologies of the eyes, ears, and musculoskeletal system are also observed.

With an excess amount of melanin, the layers become yellow.