This is the first function of the sclera - providing high-quality vision, due to the fact that light rays cannot penetrate the scleral tissue, which would cause blinding. The main functions of the sclera are the protection of the inner membranes of the eye from external damage and support for the structures and tissues of the eye located outside the eyeball: extraocular muscles, ligaments, blood vessels, nerves. Being a dense structure, the sclera, in addition, is involved in maintaining intraocular pressure and, in particular, the outflow of aqueous humor, due to the presence of the Shlemov canal.
The structure of the sclera
The sclera is the outer, dense, opaque membrane that makes up most of the entire fibrous membrane of the eyeball. It makes up approximately 5/6 of its area and has a thickness in various areas from 0.3 to 1.0 mm. The sclera is thinnest in the area of the equator of the eye - 0.3-0.5 mm and at the exit point of the optic nerve, where the inner layers of the sclera form the so-called cribriform plate, through which about 400 processes of retinal ganglion cells, the so-called axons, emerge.In places where it is thinned, the sclera is susceptible to protrusion - the formation of so-called staphylomas, or the formation of excavation of the optic nerve head, which is observed in glaucoma. In case of blunt injuries to the eyeball, scleral ruptures are also observed in places of thinning - most often between the areas of attachment of the extraocular muscles.
The sclera performs the following important functions: frame - serves as a support for the inner and outer membranes of the eyeball, the attachment point for the extraocular muscles and ligaments of the eyeball, as well as blood vessels and nerves; protection from external adverse influences; and since the sclera is an opaque tissue, it protects the retina from excessive external lighting, that is, side lights, providing good vision.
The sclera consists of several layers: the episclera, that is, the outer layer, the sclera itself and the inner layer - the so-called brown plate.
The episcleral layer has a very good blood supply and is also connected to the outer fairly dense Tenon's capsule of the eye. The anterior sections of the episclera are richest in blood flow, since blood vessels pass to the anterior section of the eyeball in the thickness of the rectus extraocular muscles.
The scleral tissue consists of dense collagen fibers; between them there are cells, so-called fibrocytes, which produce collagen.
The inner layer of the sclera is externally described as a brown plate, as it contains a large number of pigment-containing cells - chromatophores.
Several end-to-end channels, the so-called emissaries, pass through the thickness of the sclera, which are a kind of conductors for blood vessels and nerves entering or exiting the eyeball. At the anterior edge, on the inner side of the sclera, there is a circular groove, up to 0.8 mm wide. Its posterior protruding edge, the scleral spur, serves as the attachment point for the ciliary body. The anterior edge of the groove is in contact with the Descemet's membrane of the cornea. Most of the groove is occupied by the trabecular diaphragm, and at the bottom is Schlemm's canal.
Due to its connective tissue structure, the sclera is susceptible to the development of pathological processes that occur in systemic connective tissue diseases or collagenoses.
Methods for diagnosing scleral diseases
- Visual inspection.
- Biomicroscopy is a study under a microscope.
- Ultrasound diagnostics.
Symptoms for diseases of the sclera
Congenital changes:- Melanosis of the sclera.
- Congenital disorders of collagen structure, for example, in Van der Hewe's disease.
- Staphylomas of the sclera.
- Excavation of the optic nerve head is observed in glaucoma.
- Episcleritis and scleritis are inflammations of the scleral tissue.
- Scleral ruptures.
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.
- The outer layer is a loose tissue with a branched vascular system, which is divided into deep and superficial vascular networks.
- The sclera itself, consists of collagen fibers and elastic tissues.
- 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.
- The eye muscles, which are responsible for eye mobility, are attached to the tissues of the capsule.
- The ethmoidal arteries of the posterior part penetrate the sclera.
- A branch of the ophthalmic nerve approaches the eyeball through the capsule.
- The capsule tissue serves as the shell.
- 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 and negative environmental factors. Protein serves as a framework for the muscular system and ligaments of the organ of vision.
What should the sclera of a healthy person look like?
The sclera is normally white with a bluish tint.
Due to their small thickness, the child has blue sclera, through which the pigment and vascular layer are visible.
Changes in color (dullness, yellowness) indicate disturbances 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 of the musculoskeletal system, and 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 is a dense, opaque part of the fibrous (outer) membrane of the eyeball (one sixth of the outer membrane is the cornea - the transparent part).
The sclera of the eye consists of chaotically located collagen fibers, providing its strong structure. Due to the fact that this membrane is opaque, light rays are not able to penetrate through it to the retina. This provides protection to the retina from damage from excessive light rays.
The sclera also provides a shape-forming function, being a support for both the tissues of the eyeball and extraocular structures (vessels, nerves, ligamentous and muscular apparatus of the eye). In addition, this membrane is involved in the regulation of intraocular pressure (Schlemm’s canal is located in its thickness, due to which aqueous humor outflows from the anterior chamber).
Structure
The sclera makes up five-sixths of the fibrous membrane of the eyeball. In different areas its thickness is 0.3-1 mm. The thinnest part is located in the equator of the eye, as well as at the exit point of the optic nerve, the cribriform plate, where many axons of retinal ganglion cells emerge. It is in these areas that, with increased intraocular pressure, protrusions - staphylomas, as well as excavation of the optic nerve head - can form. This process is observed in glaucoma.
In case of blunt eye injuries, ruptures of the scleral membrane most often form in the area of its thinning in the area of fixation of the extraocular muscles.
Main functions of the sclera:
- frame (support for the internal and external structures of the eyeball);
- protective (protects from adverse external influences, from excessive light rays entering the retina);
- regulation of intraocular pressure (ensures the outflow of aqueous humor).
The scleral membrane consists of the following layers:
- episcleral - a layer rich in blood vessels associated with the outer dense capsule of the eye (Tenon's); the largest number of vessels is located in the anterior sections, where the ciliary arteries pass from the thickness of the extraocular muscles;
- scleral tissue itself - dense collagen fibers, between which are located fibrocytes, the processes of which form a kind of network;
- internal - a brown plate consisting of thinned fibers, as well as chromatophores - pigment-containing cells that give the appropriate color. This layer has practically no nerve endings and is poor in blood vessels.
In the thickness of the sclera there are emissaries - channels through which arteries, veins and nerves pass to the choroid. Around the optic nerve there are emissaries of the posterior short ciliary arteries, in the equator region there are emissaries of the vorticose veins, in the anterior region there are emissaries through which the anterior ciliary arteries pass.
A circular groove runs along the inner side of the sclera in the region of its anterior edge. The ciliary (ciliary) body is attached to its posterior protruding edge - the scleral spur, and its anterior edge borders the descemental membrane of the cornea. In the area of the bottom of the groove there is a venous sinus - Schlemm's canal.
Since the sclera is a connective tissue rich in collagen fibers, it is susceptible to pathological processes inherent in collagenosis, systemic connective tissue diseases.
Video about the structure and functions of the sclera of the eye
Diagnosis of scleral diseases
Diagnosis of the condition of the scleral membrane is carried out using an external examination, ultrasound examination, as well as
The sclera is the outer layer of the eyeball, which covers 5/6 of its area. Due to the high density of the tissue, the sclera acts as a kind of opaque capsule with variable thickness.
The structure of the sclera
The structure of the sclera has three layers:
- The outer one, which is called the episclera;
- Middle, or sclera itself;
- Internal (brown plate).
The episclera contains a large number of blood vessels that provide blood with oxygen. In the upper regions, the blood flow is more powerful than in the remaining parts. This pattern is due to the fact that most of the vessels come from the muscle fibers of the anterior part of the eyeball.
The middle layer contains many collagen fibers and fibrocytes. The latter produce collagen as needed.
The brown plate contains a large amount of pigment, which gives a specific color to the tissues of this layer. Pigment cells that are found in the inner layer of the sclera are called zoromatophores. The endothelium is located on top of the brown plate.
The entire thickness of the sclera is penetrated by nerve fibers and vascular bundles that pass through special channels (emissaries).
Physiological sclera
The main role of the sclera is protective; it prevents the negative impact of external factors (mechanical and physical) on the internal structures of the eye. This ensures normal functioning of the eye and clear vision of objects. In addition, some muscle fibers are attached to the sclera, which help the eye move when studying the external world. This important function of the sclera is called support.
Video about the structure of the sclera of the eye
Symptoms of scleral damage
Scleral disease is characterized by the appearance of the following symptoms:
- Scleral rupture;
- Formation of dark spots on the surface;
- Decreased overall visual acuity;
- Changes in the structure of collagen fibers.
Diagnostic methods for scleral lesions
To identify pathology when scleral disease is suspected, perform the following manipulations:
- External visual inspection;
- eyes;
- eyes using a microscope.
Once again, it should be recalled that the main function of the sclera is protective, due to which it protects the eye from mechanical influence and negative environmental factors. In this regard, it is very important to care for this structure of the eye properly and undergo examinations by doctors to identify pathologies.
Diseases of the sclera
Due to the fact that the sclera protects the eye from external influences and provides a supporting function, disruption of its functioning negatively affects the entire optical system. Among scleral diseases, the following groups are distinguished:
- Congenital (in particular, melanosis);
- Acquired (for example, staphyloma,).
As the thickness decreases, the color of the sclera changes. Sometimes this is due to a disorder in the hearing aid. With melanosis, dark spots appear on the surface of the sclera.
When there is inflammation in the area of the eyeball, the process can affect other systems of the body, and therefore intervention is required.
It is a rather complex system, all the parts of which only together allow us to see. The opportunity to see the world around us is truly unique, so every person must know about the structure of the eye.
Of course, there is simply no need to study the anatomy of an organ with specification of the slightest structural elements, but getting acquainted with the main components of the eye will not be superfluous, at least for general development.
In today's material we will talk about one of the main parts of the eyeball, or rather, about it. More information about the anatomical structure, functions and possible pathologies of the sclera can be found below.
The sclera is dense tissue
The sclera of the human eye is a multilayered and dense tissue of this organ. You can see it simply by looking in the mirror, because the scleral formation is the very “white” of the eye that surrounds and. According to its anatomical characteristics, the sclera is a tissue with a fibrous and very dense structure.
Despite its relatively complex structure, the scleral formation of the eye can be characterized as a bundle-shaped and randomly organized accumulation of collagen. It is because of this substance that the “protein” of the organ is opaque and quite dense in structure.
Multilayering is the main characteristic of the sclera. In science, it is customary to distinguish three main layers, or more precisely:
- The outer layer or episclera is a well-supplied tissue. The main purpose of this part of the sclera is the formation of superficial and deep vascular networks that provide the previously mentioned blood supply to the anterior part of the eye.
- The middle layer or the sclera itself is the part of the sclera consisting mainly of collagen and the fibrocytes that form it. The sclera itself is intended to perform the basic functions of the sclera and organize in it the pathways for nerves and vessels that approach the eye and are necessary for its functioning.
- The inner layer or brown plate is a small part of the sclera, consisting of collagen fibers and some other elastic substances. It is responsible for the formation of the outer and inner colors of the sclera, and also performs a number of applied functions.
Structurally, the scleral tissue is thick enough for such a miniature organ as the eye. On average, its thickness ranges from 0.3 to 1 millimeter. It is worth noting that the anterior part of the sclera that a person sees is thicker than that which is located in the eye socket and is inaccessible for viewing. Despite this, the anatomical structure of the sclera is the same both front and back.
Functions of the sclera
The sclera is a multilayered membrane The functional purpose of the sclera is very great and important for humans. In many ways, this phenomenon is associated with the unique structural scleral tissue and its anatomical features. In general, the functions of the sclera are as follows:
- Firstly, it protects the particularly sensitive components of the eye from the adverse effects of sunlight. This occurs due to the fact that randomly located and fairly dense collagen refracts sunlight and reduces solar radiation reaching the same pupil or lens to an insignificant amount.
- Secondly, not only collagen, but also other components of the sclera protect the same sensitive components of the eye from other external factors that can negatively affect them.
- Thirdly, the scleral formation forms a kind of frame to which the ligamentous, muscular, vascular and other apparatus of the eye necessary for its stable functioning are attached.
- Fourthly, the sclera provides a path for the ethmoidal arteries to the posterior part of the eye, as well as the exit of the venous branches of the organ, which is very important for stable blood circulation in it.
- And fifthly, it is the scleral tissue that allows nerves to approach the eye and eye muscles, as a result of which the eyeball functions perfectly.
Together, the functions of the sclera provide a person with a stable, comfortable and uninterrupted ability to see. Thanks to this, the scleral formation is not only a protective shell, but also a strong framework for organization.
Possible pathologies
The sclera performs a very important function Considering such a high importance of the sclera for the human eye, it is not difficult to guess that any of its pathologies can cause considerable discomfort to a person. The first thing that indicates problems with the scleral tissue is a change in its color.
Normally, the sclera of an adult is a white-bluish formation; for children, pronounced blue pigmentation is acceptable, and in older people, a white-yellowish tint of the tissue is also considered normal.
If you deviate from the norms described above, most likely there is some problem with the sclera. Often it either fades greatly or turns yellow. A pronounced yellow tint to the tissue often indicates the presence of an infectious disease of the eye or liver pathologies, while the tarnishing of the tissue is often caused by secretive disturbances in the body.
Modern medicine divides scleral pathologies into two large categories: congenital and acquired. Congenital diseases of scleral tissue include:
- Melanosis or melanopathy is a pathology expressed in the formation of the color of the sclera and giving it yellowness. This disease occurs due to increased melanin pigmentation, which is provoked by metabolic disorders in the body. The disorder is observed, as a rule, from early childhood.
- Blue sclera syndrome is a pathology similar to the one described above, but manifests itself in the staining of the scleral tissue with a pronounced white-blue tint. As recent studies show, this disease is associated with a lack of iron in the body; it often goes away simultaneously with disturbances in visual and auditory functions.
Among the acquired pathologies of the sclera of the eye, the following are often found:
- Staphyloma is a depletion of the scleral tissue membrane and its protrusion. The appearance of pathology is associated with the development of a destructive disorder in the eyes.
- Episcleritis is an inflammatory process of the outer part of the sclera. The pathology is expressed in the appearance of nodular seals around the corneas of the eyes. It often does not require treatment, as it goes away on its own, but sometimes the pathology recurs.
- Scleritis is an inflammatory process of the inner part of the sclera. A more serious pathology, accompanied by pain in the eyes, a person’s immunodeficiency state and swelling of the tissues close to the organ.
Regardless of the type of acquired pathology of the sclera, it appears due to depletion of the membranes of the eyes, as a result of which their protective functions decrease, and under the influence of unfavorable microflora, inflammation begins to develop.
As a rule, problems with scleral tissue occur simultaneously with malfunctions in other nodes of the body.
Diagnosis of scleral defects
The sclera has clear pigmentation Despite the relative safety of scleral pathologies, they should not be ignored. It happens that such eye ailments develop into more serious diseases and require thorough treatment. In order to prevent such complications, it is very important to diagnose scleral tissue pathologies in a timely manner.
Today, their identification takes place in three stages:
- The ophthalmologist talks with the patient and identifies clear symptoms of his illness. Problems with the sclera often cause symptoms such as:
- Pain in the eyes;
- feeling of a foreign body in the eyeball;
- frequent and involuntary lacrimation;
- modification of the shade of scleral tissue;
- problems in the anatomical structure of the eyeball: dilated blood vessels, protrusion of the eye, and so on.
Then an external analysis of the organ and the sclera in particular occurs, which allows a preliminary diagnosis to be made. After this, an ophthalmologist performs a thorough examination of the eye under a microscope or a special radiographic diagnosis.
Such a comprehensive examination helps to diagnose a potentially dangerous pathology in a timely manner and take some measures to treat it. It is worth noting that ignoring getting rid of scleral pathologies is quite dangerous, because they can develop into clouding of the cornea or its deformation, and this can partially or completely deprive a person of vision.
This concludes, perhaps, the most significant information on today’s topic. We hope the material presented above helped you understand what the sclera of the eye is and what functions it performs. Good health to you!
Sclera (white membrane of the eye) - structure and functions:
