The composition of the intraocular fluid. Circulation of aqueous humor in the eye (intraocular fluid) and its influence on the development of glaucoma

aqueous humor is a colorless jelly-like liquid that completely fills both.

The composition that aqueous humor has is similar to the composition of blood, only with the lowest protein content. The rate at which the formation of a clear liquid occurs is 2-3 μl per minute. During the day, 3-9 ml of fluid is formed in the human eye. Secretion is carried out by the ciliary processes, which in their shape resemble long and narrow folds. The processes protrude from the region located behind the iris, where the ligaments join the eye. The outflow of aqueous humor is carried out by means of the trabecular meshwork, episcleral vessels and the uveoscleral system.

How does aqueous humor circulate

Outflow pathway for aqueous humor is a complex system in which several structures are involved at once. After the aqueous humor is formed by the ciliary processes, it flows into the posterior chamber, and then through to the anterior chamber. Due to the high temperature conditions on the front surface, the aqueous humor rises up, and then falls down along the rear low-temperature surface. After that, it is absorbed in the anterior chamber and through the trabecular mesh enters the Schlemm canal and again into the bloodstream.

Functions of the aqueous humor of the eye

aqueous humor The eye contains essential nutrients for the eye, such as amino acids and glucose, which are essential for nourishing the avascular structures of the eye.

These structures include:

lens
- anterior section
- corneal endothelium
- trabecular meshwork

The aqueous humor of the eye contains immunoglobulins, through which the protective function of the internal parts of all structures of the eye is carried out.

The constant circulation of these substances neutralize various factors that can lead to damage to all structures of the eye. aqueous humor is a light-refracting medium. due to the ratio of formed and excreted aqueous humor.

Diseases

A decrease or increase in aqueous humor leads to the development of certain diseases, such as, for example, which is characterized by an increase in intraocular pressure, that is, an increase in the amount of aqueous humor due to impaired outflow. Failed operations or eye injuries can lead to a decrease in the content of aqueous humor, as a result of which there is an unhindered and uncontrolled outflow of fluid.

Aqueous moisture is formed with the participation of special epithelial non-pigmented cells that belong to the ciliary body. By filtering the blood, these cells produce about 3-9 ml of aqueous humor per day.

Circulation of aqueous humor

After the fluid has been formed with the participation of the cells of the ciliary body, it enters the cavity of the posterior chamber. Further, through the pupillary opening, aqueous humor flows into the anterior chamber of the eye. Under the influence of the temperature difference, fluid migrates to the upper layers along the anterior surface of the iris, and it flows down along the posterior surface of the cornea. After that, aqueous humor enters the angle of the anterior chamber, where it is absorbed into the Schlemm's canal through the trabecular meshwork. The aqueous humor is then returned to the systemic circulation.

Functions of aqueous humor

The intraocular fluid contains in its composition a large amount of nutrients, including amino acids and glucose, which are necessary to nourish some structures of the eye. First of all, this applies to those areas in which there are no blood vessels, in particular, the corneal endothelium, the lens, the trabecular meshwork, and the anterior third of the vitreous body. Due to the fact that immunoglobulins are dissolved in aqueous humor, this liquid helps in the fight against potentially dangerous microorganisms.

In addition, the fluid inside the eye is one of the refractive media of this organ. It also maintains the tone of the eyeball and determines the level of intraocular pressure (the balance between fluid production and its filtration).

Symptoms of a violation of the outflow of aqueous humor

Normally, intraocular pressure, which is maintained by the mechanism of aqueous humor circulation, ranges from 18 to 24 mm Hg. Art. If this mechanism is violated, both a decrease in intraocular pressure (hypotension) and its increase (hypertonicity) can be observed. With hypotension of the eyeball, there is a high probability of developing retinal detachment, accompanied by a decrease in visual acuity up to its loss. An increase in intraocular pressure may be accompanied by symptoms such as headache, impaired visual acuity, nausea. Due to progressive damage to the optic nerve, visual loss in patients with ophthalmic hypertonicity is irreversible.

Diagnostics

• Visual inspection and palpation of the eyeball
• Ophthalmoscopy of the fundus
• Tonometry
• Perimetry
• Campimetry - determination of the central scotoma and the size of the blind spot in the field of view.

Diseases affecting the outflow tract of aqueous humor of the eye

If the membranes of the eyeball are damaged, aqueous humor may leak out of its cavities. This situation occurs as a result of trauma or surgery and leads to hypotension of the eye. Hypotension also occurs with retinal detachment or cyclitis. In case of violation of the outflow of aqueous humor, there is an increase in pressure inside the eyeball, which leads to the development of glaucoma.

Aqueous moisture circulates along the episcleral and intrascleral venous network of the anterior segmented area of ​​the eyeball. It supports metabolic processes, the trabecular apparatus. Under normal circumstances, the human eye contains 300 mm of the component or 4% of the total volume.

The fluid is produced from the blood by special cells that make up the structure of the ciliary body. The human eye produces 3-9 ml of the component per minute. The outflow of moisture occurs through the episcleral vessels, the uveoscleral system and the trabecular meshwork. Intraocular pressure is the ratio of the developed component to the output.

What is aqueous humor?

Aqueous moisture (intraocular fluid)- a colorless liquid of a jelly-like appearance, with which two eye chambers are completely filled. The composition of the element is very similar to blood. The only difference is that it contains less protein. Moisture is produced at a rate of 2-3 μl / min.

Structure

The aqueous humor of the eye is almost 100% water. The dense component includes:

• anorganic components (chlorine, sulfate, etc.);
• cations (calcium, sodium, magnesium, etc.);
• an insignificant proportion of protein;
• glucose;
• ascorbic acid;
• lactic acid;
• amino acids (tryptophan, lysine, etc.);
• enzymes;
• hyaluronic acid;
• oxygen;
• a small amount of antibodies (formed only in the secondary fluid).

Functions

The functional purpose of the liquid is in the following processes:

• nutrition of the avascular elements of the organ of vision due to the constituent amino acids and glucose;
• removal of potential threatening factors from the internal environment of the eye;
• organization of light-refracting environment;
• regulation of intraocular pressure.

Symptoms

The amount of fluid inside the eye can change due to the development of eye diseases or when exposed to external factors (trauma, surgery).

If the moisture outflow system is disturbed, there is a decrease in intraocular pressure (hypotension) or its increase (hypertonicity). In the first case, the appearance is likely, which is accompanied by deterioration or complete loss of vision. With increased pressure inside the eye, the patient complains of headache, visual disturbances, urge to vomit.

The progression of pathological conditions leads to the development - a violation of the process of removing fluid from the organ of vision and its tissues.

Diagnostics

Diagnostic measures for suspected development of pathological conditions in which intraocular fluid for some reason is inside the eye in excess, in deficit or does not go through the entire circulation process, are reduced to the following procedures:

• visual inspection and palpation of the apple of the eye(the method allows you to determine the visible deviations and location of pain);
• fundus ophthalmoscopy– a procedure for assessing the condition of the retina, optic nerve head and vascular network of the eye using an ophthalmoscope or fundus lens;
• tonometry- an examination that allows you to determine the level of change in the eyeball when exposed to the cornea. Under normal intraocular pressure, deformation of the sphere of the organ of vision is not observed;
• perimetry- a method for determining visual fields by means of computer technology or special equipment;
• campimetry– identification of central scotomas and dimensional indicators of the blind spot in the visual field.

Treatment

With the above violations, within the framework of the therapeutic course, the patient is prescribed medications that restore intraocular pressure, as well as drugs that stimulate blood supply and metabolism in the tissues of the organ.

Surgical methods of treatment are applicable in cases where drugs do not have the desired effect. The type of operation performed depends on the type of pathological process.

Thus, intraocular fluid is a kind of internal environment of the organ of vision. The composition of the element is similar to the structure of blood and provides the functional purpose of moisture. Local pathological processes include violations of fluid circulation and deviations in its quantitative index.

intraocular fluid or aqueous humor is a kind of internal environment of the eye. Its main depots are the anterior and posterior chambers of the eye. It is also present in the peripheral and perineural fissures, suprachoroidal and retrolental spaces.

In its chemical composition, aqueous humor is analogous to cerebrospinal fluid. Its amount in the eye of an adult is 0.35-0.45, and in early childhood - 1.5-0.2 cm 3. The specific gravity of moisture is 1.0036, the refractive index is 1.33. Therefore, it practically does not refract rays. Moisture is 99% water.

Most of the dense residue is made up of anorganic substances: anions (chlorine, carbonate, sulfate, phosphate) and cations (sodium, potassium, calcium, magnesium). Most of all in the moisture of chlorine and sodium. A small proportion is accounted for by protein, which consists of albumins and globulins in a quantitative ratio similar to blood serum. Aqueous moisture contains glucose - 0.098%, ascorbic acid, which is 10-15 times more than in the blood, and lactic acid, because. the latter is formed in the process of lens exchange. The composition of aqueous humor includes various amino acids - 0.03% (lysine, histidine, tryptophan), enzymes (protease), oxygen and hyaluronic acid. There are almost no antibodies in it and they appear only in the secondary moisture - a new portion of the liquid formed after the suction or expiration of the primary aqueous humor. The function of aqueous humor is to provide nutrition to the avascular tissues of the eye - the lens, the vitreous body, and partially the cornea. In this regard, a constant renewal of moisture is necessary, i.e. outflow of waste fluid and inflow of freshly formed.

The fact that the intraocular fluid is constantly being exchanged in the eye was also shown in the time of T. Leber. It was found that the fluid is formed in the ciliary body. It is called primary chamber moisture. It enters mostly in the rear chamber. The posterior chamber is bounded by the posterior surface of the iris, the ciliary body, the ligaments of zon, and the extrapupillary part of the anterior lens capsule. Its depth in various departments varies from 0.01 to 1 mm. From the posterior chamber through the pupil, the fluid enters the anterior chamber - a space bounded in front by the back surface of the iris and lens. Due to the valve action of the pupillary edge of the iris, moisture cannot return back to the posterior chamber from the anterior chamber. Further, the spent aqueous humor with tissue metabolism products, pigment particles, cell fragments is removed from the eye through the anterior and posterior outflow tracts. The anterior outflow tract is the Schlemm canal system. Fluid enters the Schlemm's canal through the anterior chamber angle (ACA), an area bounded anteriorly by trabeculae and Schlemm's canal, and posteriorly by the root of the iris and the anterior surface of the ciliary body (Fig. 5).

The first obstacle in the way of aqueous humor from the eye is trabecular apparatus.

On cross section, the trabecula has a triangular shape. Three layers are distinguished in the trabecula: uveal, corneoscleral, and porous tissue (or the inner wall of Schlemm's canal).

Uveal layer consists of one or two plates, consisting of a network of crossbars, which are a bundle of collagen fibers covered with endothelium. Between the crossbars there are slots with a diameter of 25 to 75 mu. On the one hand, the uveal plates are attached to the Descemet's membrane, and on the other hand, to the fibers of the ciliary muscle or to the iris.

Corneoscleral layer consists of 8-11 plates. Between the crossbars in this layer there are elliptical holes located perpendicular to the fibers of the ciliary muscle. With tension of the ciliary muscle, the openings of the trabeculae expand. The plates of the corneoscleral layer are attached to the Schwalbe ring, and on the other hand to the scleral spur or directly to the ciliary muscle.

The inner wall of Schlemm's canal consists of a system of argyrophilic fibers enclosed in a homogeneous substance rich in mucopolysaccharides. In this tissue, there are rather wide Sonderman canals with a width of 8 to 25 mu.

Trabecular fissures are abundantly filled with mucopolysaccharides, which disappear when treated with hyaluronidase. The origin of hyaluronic acid in the chamber angle and its role have not been fully elucidated. Obviously, it is a chemical regulator of the level of intraocular pressure. Trabecular tissue also contains ganglion cells and nerve endings.

Schlemm's channel is an oval-shaped vessel located in the sclera. The channel clearance is on average 0.28 mm. From the Schlemm's canal in the radial direction, 17-35 thin tubules depart, ranging in size from thin capillary filaments of 5 mu, to trunks up to 16r in size. Immediately at the exit, the tubules anastomose, forming a deep venous plexus, representing gaps in the sclera lined with endothelium.

Some tubules run straight through the sclera to the episcleral veins. From the deep scleral plexus, moisture also goes to the episcleral veins. Those tubules that go from Schlemm's canal directly to the episclera, bypassing the deep veins, are called water veins. In them, one can see for some distance two layers of liquid - colorless (moisture) and red (blood).

Posterior outflow tract These are the perineural spaces of the optic nerve and the perivascular spaces of the retinal vascular system. The angle of the anterior chamber and the Schlemm's canal system begin to form already in the two-month-old fetus. In a three-month-old, the angle is filled with mesoderm cells, and in the peripheral sections of the corneal stroma, the cavity of the Schlemm's canal is distinguished. After the formation of the Schlemm's canal, the scleral spur grows in the corner. In a four-month-old fetus, corneoscleral and uveal trabecular tissue differentiate from mesoderm cells in the corner.

The anterior chamber, although morphologically formed, however, its shape and size are different from those in adults, which is explained by the short sagittal axis of the eye, the peculiarity of the shape of the iris and the convexity of the anterior surface of the lens. The depth of the anterior chamber in a newborn in the center is 1.5 mm, and only by the age of 10 does it become like in adults (3.0-3.5 mm). By old age, the anterior chamber becomes smaller due to the growth of the lens and sclerosis of the fibrous capsule of the eye.

What is the mechanism for the formation of aqueous humor? It has not yet been finally resolved. It is regarded both as a result of ultrafiltration and dialysate from the blood vessels of the ciliary body, and as an actively produced secret of the blood vessels of the ciliary body. And whatever the mechanism of formation of aqueous humor, we know that it is constantly produced in the eye and flows out of the eye all the time. Moreover, the outflow is proportional to the inflow: an increase in inflow increases the outflow, respectively, and vice versa, a decrease in inflow reduces the outflow to the same extent.

The driving force that causes the continuity of the outflow is the difference - a higher intraocular pressure and a lower one in the Schlemm's canal.

Methods for removing foreign bodies from the conjunctival sac and cornea:

1) foreign bodies located in the superficial layers of the cornea sometimes fall out on their own

2) to remove superficially located foreign bodies, in addition to ordinary needles, flat and grooved chisels, tweezers, a dental drill, etc. are used.

3) to remove the cornea from the stroma under local anesthesia, an incision is made in the cornea above the location of the fragment with a linear knife or a razor blade, then a magnet is used. If the foreign body cannot be removed with a magnet, it is removed with a spear or needle.

4) after epibulbar anesthesia with 0.5% solution of dicaine, foreign bodies of the conjunctiva are removed with a wet swab or a small injection needle.

Prevention of eye injuries:

a) strict observance of technical and safety rules and the implementation of sanitary and hygienic standards in industrial premises, air purification at enterprises from smoke, dust, fumes, good lighting

b) individual eye protection with goggles, masks; use of protective devices of working machines.

c) the fight against child injuries of teachers, parents, public organizations

Ticket number 16

16. Chambers of the eye. Ways of outflow of intraocular fluid.

Front camera is a space bounded by the posterior surface of the cornea, the anterior surface of the iris and the central part of the anterior lens capsule. The place where the cornea meets the sclera and the iris meets the ciliary body is called the anterior chamber angle. The angle of the anterior chamber is the narrowest part of the anterior chamber. The anterior wall of the APC with the Schwalbe ring, the trabecular apparatus and the scleral spur, the posterior wall of the APC with the root of the iris, the apex with the base of the ciliary crown. On the outer wall of the APC is the drainage system of the eye.

The drainage system of the eye consists of the trabecular apparatus, scleral sinus (Schlemm's canal) and collector tubules. The trabecular apparatus is a ring-shaped crossbar thrown through the internal scleral groove. On the section, it has the shape of a triangle, the apex of which is attached to the anterior edge of the groove (the boundary ring of Schwalbe), and the base is attached to its posterior edge (scleral spur). The trabecular diaphragm consists of three main parts: the uveal trabecula, the corneoscleral trabecula, and the juxtacanalicular tissue. The first two parts have a layered structure. Each layer (there are 10-15 in total) is a plate consisting of collagen fibrils and elastic fibers, covered on both sides with a basement membrane and endothelium. There are holes in the plates, and between the plates there are slots filled with VZH. The juxtacanalicular layer, consisting of 2-3 layers of fibrocytes and loose fibrous tissue, provides the greatest resistance to the outflow of AH from the eye. The outer surface of the juxtacanalicular layer is covered with endothelium containing giant vacuoles. The latter are dynamic intracellular tubules through which the VJ passes from the trabecular apparatus to the Schlemm's canal.

Schlemm's canal is a circular fissure lined with endothelium and located in the posterior part of the internal scleral groove. It is separated from the anterior chamber by a trabecular apparatus, outside the canal is the sclera and episclera with venous and arterial vessels. The VJ flows from the Schlemm's canal along 20-30 collector tubules into the episcleral veins (recipient veins).

The anterior chamber freely communicates with the posterior chamber through the pupil. rear camera is located behind the iris, which is its anterior wall and is bounded on the outside by the ciliary body, behind the vitreous body. The equator of the lens forms the inner wall. The entire space of the posterior chamber is permeated with ligaments of the ciliary girdle.

Normally, both chambers of the eye are filled with aqueous humor, which in its composition resembles blood plasma dialysate. Aqueous moisture contains nutrients (glucose, ascorbic acid, oxygen) used by the lens and cornea, and removes metabolic products (lactic acid, carbon dioxide, exfoliated pigment and other cells) from the eye.

Production and outflow of intraocular fluid (IFL).

VP is continuously produced by the ciliary corona with the active participation of the non-pigmented epithelium of the retina and, to a lesser extent, in the process of ultrafiltration of the capillary network. Moisture fills the posterior chamber, then enters the anterior chamber through the pupil (it serves as its main reservoir and has twice the volume of the posterior chamber) and flows mainly into the episcleral veins through the drainage system of the eye located on the anterior wall of the anterior chamber angle. About 15% of the fluid leaves the eye, seeping through the stroma of the ciliary body and the sclera into the uveal and scleral veins - the uveoscleral outflow pathway of the VS. A small part of the liquid is absorbed by the iris (like a sponge) and the lymphatic system.

Regulation of intraocular pressure. The formation of aqueous humor is under the control of the hypothalamus. A certain effect on secretory processes is exerted by a change in pressure and the rate of outflow of blood in the vessels of the ciliary body. The outflow of intraocular fluid is regulated by the mechanism of the ciliary muscle - scleral spur - trabecula. The longitudinal and radial fibers of the ciliary muscle are attached with their anterior ends to the scleral spur and trabeculae. With its contraction, the spur and trabecula depart posteriorly and medially. The tension of the trabecular apparatus increases, and the holes in it and the scleral sinus expand.

Front camera (camera anterior) - a space bounded in front by the cornea, behind by the iris and in the pupil by the lens. The depth of the anterior chamber is variable, it is greatest in the central part of the anterior chamber, located opposite the pupil, and reaches 3-3.5 mm. In conditions of pathology, both the depth of the chamber and its unevenness acquire diagnostic value. rear camera (camera posterior) is located behind the iris, which is its front wall. The outer wall is the ciliary body, the posterior wall is the anterior surface of the vitreous body. The inner wall is formed by the equator of the lens and the pre-equatorial zones of the anterior and posterior surfaces of the lens. The entire space of the posterior chamber is permeated with fibrils of the zinn ligament, which support the lens in a suspended state and connect it to the ciliary body. The chambers of the eye are filled with aqueous humor - a transparent colorless liquid with a density of 1.005-1.007 with a refractive index of 1.33. The amount of moisture in a person does not exceed 0.2-0.5 ml. The aqueous humor produced by the processes of the ciliary body contains salts, ascorbic acid, and microelements. drainage system The drainage system is the main way of outflow of intraocular fluid. Intraocular fluid is produced by processes of the ciliary body. Each process consists of stroma, wide thin-walled capillaries and two layers of epithelium. Epithelial cells are separated from the stroma and from the posterior chamber by the outer and inner boundary membranes. The cell surfaces facing the membranes have well-developed membranes with numerous folds and depressions, as in secretory cells. Consider the outflow of intraocular fluid from the eye (hydrodynamics of the eye). The transition of intraocular fluid from the posterior chamber, where it first enters, to the anterior one, normally does not encounter resistance. Of particular importance is the outflow of moisture through the drainage system of the eye, located in the corner of the anterior chamber (the place where the cornea passes into the sclera, and the iris into the ciliary body) and consisting of the trabecular apparatus, Schlemm's canal, collector channels, intra- and episcleral systems. venous vessels. The trabecula has a complex structure and consists of the uveal trabecula, the corneoscleral trabecula, and the juxtacanalicular layer. The first two parts consist of 10-15 layers formed by plates of collagen fibers, covered on both sides with a basement membrane and endothelium, which can be considered as a multi-tiered system of slits and holes. The outermost, juxtacanalicular layer differs significantly from the others. It is a thin diaphragm of epithelial cells and a loose system of collagen fibers impregnated with mucopolysaccharides. That part of the resistance to the outflow of intraocular fluid, which falls on the trabeculae, is located in this layer. Next comes Schlemm's canal or scleral sinus, which was first discovered in a bull's eye in 1778 by Fountain, and in 1830 Schlemm described in detail in humans. Schlemm's canal is a circular fissure located in the limbus zone. On the outer wall of the Schlemm canal there are outlets of the collector channels (20-35), first described in 1942 by Asher. On the surface of the sclera, they are called water veins, which flow into the intra- and episcleral veins of the eye. The function of the trabeculae and Schlemm's canal is to maintain a constant intraocular pressure. Violation of the outflow of intraocular fluid through the trabeculae is one of the main causes of primary glaucoma.