11. Cameras of the eye

The anterior chamber is a space 3-3.5 mm deep, limited in front by the posterior surface of the cornea, along the periphery (in the corner) by the root of the iris, ciliary body and corneoscleral trabeculae, and behind by the anterior surface of the iris.

The anterior chamber angle, or iridocorneal angle, is formed by corneal-scleral trabecular tissue, a strip of sclera (scleral spur), the ciliary body and the root of the iris. In the corner of the chamber there is Schlemm's canal - a circular sinus, bounded by the sclera (intrascleral groove) and corneoscleral trabeculae.

Changes in the anterior chamber during ontogenesis

In the prenatal period, the angle of the anterior chamber is covered with mesodermal tissue, but by the time of birth it is largely resorbed. A delay in the reverse development of the mesoderm can lead to an increase in intraocular pressure even before the birth of the child and the development of hydrophthalmos (enlargement of the eye).

By the time the child is born, the anterior chamber is morphologically formed, but its shape and size differ significantly from those of adults. This is explained by the short anteroposterior axis of the eye and the convexity of the anterior surface of the lens.

In old age, as a result of the growth of the lens and some sclerosis of the fibrous capsule of the eye, the anterior chamber gradually becomes smaller again and the angle becomes sharper (a physiological age-related change).

The posterior chamber is a space bounded anteriorly by the posterior surface of the iris and the ciliary body, zonular fibers, the anterior part of the lens capsule, and posteriorly by the posterior lens capsule and the vitreous membrane. Has a depth of 0.01 to 1 mm.

During accommodation of the eye, the shape and size of the posterior chamber constantly changes. The posterior chamber communicates with the anterior chamber through the pupil.

12. Intraocular fluid

Intraocular fluid, or aqueous humor, is produced by the epithelium of the ciliary processes, and its main depot is the anterior and posterior chambers of the eye in an amount of 0.2-0.3 ml.

Compound: 98% water, the rest - proteins, glucose. Characteristic. The intraocular fluid is transparent, its density is 1.0036, and the refractive index is 1.33, which is almost indistinguishable from that of the cornea. Consequently, chamber moisture practically does not refract light rays penetrating into the eye.

Function. Aqueous humor nourishes the avascular structures of the eyeball (lens, vitreous body, corneal endothelium).

Circulation of intraocular fluid. The process of its renewal is necessary for proper nutrition of the eye tissues. The amount of circulating fluid is constant, which ensures relative stability of intraocular pressure. The outflow of intraocular fluid from the posterior chamber goes mainly through the pupil area into the anterior chamber, and then through the angle of the anterior chamber the fluid enters the venous sinus of the sclera, and then into the venous system. Impaired outflow can lead to increased intraocular pressure.

13. Eye socket

The orbit, or orbit, is a paired depression in the skull where the eyeball with its auxiliary apparatus (vessels, nerves, muscles, fiber, fascia, lacrimal glands, connective membrane and part of the lacrimal ducts) are located. The depth of the adult orbit is 4 cm, the width of the entrance to the orbit is 4 cm, the height is 3.5 cm. Walls:

The upper wall is represented by the frontal bone and the lesser wing of the sphenoid bone. On the inner third of the upper edge of the orbit there is a supraorbital notch for the vessels and nerve. In the upper internal part of the orbit, at the border of the orbital plate of the ethmoid bone and the frontal bone, there are anterior and posterior ethmoidal foramina through which the arteries, veins and nerves of the same name pass. There is also a bone spike here (in young people - a cartilaginous spike), to which a cartilaginous block is attached - the tendon of the superior oblique muscle.

The lower wall is formed mainly by the orbital surface of the upper jaw, on the lateral side by the orbital surface of the zygomatic bone and in the posterior sections by the orbital process of the palatine bone. In the thickness of the lower wall of the orbit there is an infraorbital canal, which opens on the facial surface of the upper jaw with an infraorbital foramen (intended for the passage of the vessels and nerve of the same name).

The medial, or inner, wall (located on the side of the nose) is the thinnest. Formed (from front to back) by the frontal process of the maxilla, the lacrimal bone, the orbital plate of the ethmoid bone, and the lateral surface of the body of the sphenoid bone. In the anterior-inferior part of the wall there is a fossa for the lacrimal sac, which passes downwards into the nasolacrimal canal.

The lateral, or outer, wall (located on the temporal side) is the thickest part of the orbit. Formed by the zygomatic, frontal bones and the greater wing of the sphenoid bone. In the superolateral corner of the orbit there is a fossa for the lacrimal gland.

The anterior wall of the eye (like the fifth wall when closing the eyes) is formed by the orbital septum - this is a connective tissue layer that is attached to the upper edge of the orbit and goes to the outer edges of the upper cartilage of the eyelid.

In the depth of the orbit between the greater and lesser wings of the sphenoid bone there is a superior orbital fissure - the place of entry into the orbit of the oculomotor, abducens, trochlear, first branch of the trigeminal nerves and the exit of the superior ophthalmic vein. Somewhat more medially there is a optic foramen through which the optic nerve exits the orbit and the ophthalmic artery enters. At the point where the outer wall of the orbit passes into the lower wall, the inferior orbital fissure is located: through it the infraorbital and zygomatic nerves penetrate into the orbit and the inferior ophthalmic vein emerges. The orbit communicates with various parts of the skull through the above openings.

Structure. The orbit is lined with a thin plate - the periosteum, which is loosely connected to the bone, with the exception of the edges of the orbit and the optic canal. Behind the eyeball lies fatty tissue, which occupies the entire space between the muscles, the eyeball and the optic nerve lying in the orbit. Between the eyeball and fatty tissue is the connective tissue Tenon's capsule (vagina). It covers the eyeball from the limbus to the dura mater of the optic nerve. The processes of this capsule, extending from the equator of the eyeball, are woven into the periosteum of the walls and edges of the orbit and thus hold the eye in a certain position. Between the eyeball and its vagina there is a narrow gap - the episcleral space, filled with episcleral tissue and interstitial fluid, which ensures good mobility of the eyeball.

The tendons of the muscles of the eyeball, heading to the places of their attachments in the sclera, pass through the tenon capsule, which provides sheaths for them, continuing in the fascia of individual muscles.

Eye socket in newborns. Its horizontal size is larger than the vertical, its depth is small, and its shape resembles a trihedral pyramid. Only the upper wall of the orbit is well developed. The superior and inferior orbital fissures are relatively large, which widely communicate with the cranial cavity and the pterygopalatine fossa. The rudiments of the molars lie close to the lower edge of the orbit. During the process of growth, mainly due to the increase in the large wings of the main bone, the development of the frontal and maxillary sinuses, the orbit becomes deeper and takes the form of a tetrahedral pyramid.

14. Extraocular muscles

The extraocular muscles belong to the auxiliary organs of the eye. When all muscles are in uniform tension, when looking into the distance, the pupil looks straight ahead and the lines of vision of both eyes are parallel to each other. When viewing objects near, the lines of vision converge anteriorly (eye convergence).

Types of muscles: four rectus muscles (superior, inferior, lateral and medial) and two obliques (superior and inferior).

The directions of movement of the eyeballs are carried out:

Outward (abduction) - by the lateral rectus, superior and inferior oblique muscles;

Inwardly (adduction) - by the medial rectus, superior and inferior rectus muscles;

Up - superior rectus and inferior oblique muscles;

Down - the inferior rectus and superior oblique muscles.

Start and attachment.

All muscles, with the exception of the inferior oblique, originate deep in the orbit from the common tendon ring, which encloses the optic nerve in a funnel shape. Along the way, they perforate Tenon's capsule and obtain tendon sheaths from it. The tendons of the medial rectus, lateral, and inferior muscles are woven into the sclera at the corneal edge. The tendon of the superior oblique muscle is thrown over a cartilage-like block located at the medial edge of the orbit and is attached to the sclera behind the equator of the eye, 17-18 mm from the corneal edge, passing under the tendon of the superior rectus muscle.

The inferior oblique muscle starts from the inferior inner edge of the orbit, goes back and outward and is attached to the sclera behind the equator of the eyeball between the inferior and lateral rectus muscles 16-17 mm from the corneal edge. The insertion sites, the width of the tendon part and the thickness of the muscles can vary.

Ontogenesis. Muscles begin to function from the moment of birth, but their formation ends by 2-3 years of life.

The blood supply to the extraocular muscles is provided by muscular branches from the ophthalmic artery.

Innervation. The motor innervation of the lateral rectus muscle is carried out by the abducens nerve, and the superior oblique muscle by the trochlear nerve. The remaining muscles are innervated by branches of the oculomotor nerve. All these nerves enter the orbit through the superior palpebral fissure. Sensory innervation is carried out by the optic nerve and branches of the trigeminal nerve.

15. Lacrimal apparatus

Divisions of the lacrimal apparatus of the eye:

Tear-producing (lacrimal gland, accessory glands);

Lacrimal or lacrimal ducts. Tear-producing department.

The lacrimal gland is located in the lacrimal fossa of the frontal bone in the upper outer corner of the orbit. It opens with its excretory ducts into the superior conjunctival fornix. The tendon of the muscle that lifts the upper eyelid divides the gland into two parts: the upper - orbital part, larger in size (invisible when the eyelid is everted); lower - the age-old part, smaller in size (visible when the upper eyelid is everted).

Small accessory glands are localized in the fornix of the conjunctiva and at the upper edge of the cartilage of the eyelids.

Function of the lacrimal glands: production of secretion - tears, which constantly moisturizes the cornea and conjunctiva of the eye. Under normal conditions, only accessory glands function in humans, producing an average of 0.4-1 ml of tears per day. In extreme conditions, with reflex irritation of the conjunctiva (wind, light, pain, other irritants), the lacrimal gland turns on. With strong crying, up to 10 ml of liquid can be released from it. Simultaneously with the secretion of tears, salivation also occurs, which indicates a close connection between the centers that regulate the functioning of the lacrimal and salivary glands located in the medulla oblongata. During sleep, almost no tears are produced.

Characteristics of tears. A transparent liquid, its density, like saliva, is 1.001 - 1.008. Ingredients: water - 98%, the rest (2%) - protein, sugar, sodium, calcium, chlorine, ascorbic, sialic acid.

Functions of a tear:

1. By covering the outer surface of the cornea with a thin layer, it maintains normal refractive power.

2. Helps cleanse the conjunctival sac from microbes and small foreign bodies that fall on the surface of the eyeball.

3. Contains the enzyme lysozyme, which has a bacteriostatic effect. Tear fluid, as a rule, has an alkaline reaction, in which, without lysozyme or with a low content of it, many pathogenic microbes live and develop well.

The blood supply to the lacrimal gland is provided by the lacrimal artery (a branch of the ophthalmic artery).

Innervation: first and second branches of the trigeminal nerve, branches of the facial nerve and sympathetic fibers from the superior cervical ganglion. Secretory fibers pass as part of the facial nerve.

Ontogenesis. By the time the child is born, the lacrimal gland has not reached its full development, its lobulation is not fully expressed, tear fluid is not produced, so the child “cries without tears.” Only by the 2nd month of life, when the cranial nerves and autonomic sympathetic nervous system begin to fully function, active lacrimation appears.

The tear duct begins with a gap between the inner surface of the lower eyelid and the eyeball and forms a tear stream (see figure).

Through it, the tear fluid enters the lacrimal lake (located in the medial corner of the eye). At the bottom of the lacrimal lake there is a small elevation - the lacrimal caruncle, at the top of which there are upper and lower lacrimal openings. Lacrimal puncta are small openings that are the beginning of the drainage of tear fluid. They pass into the lacrimal canaliculi, which flow into the lacrimal sac 1 - 1.5 cm long, 0.5 cm wide, located in the lacrimal fossa of the orbit. Downwards, the lacrimal sac passes into the nasolacrimal duct, which has a length of 1.2-2.4 cm. The duct passes through the nasolacrimal duct and opens in the nasal cavity into the lower nasal passage.

16. Conjunctiva

The conjunctiva, or connective membrane of the eye, is the epithelial covering of the inner surface of the eyelids and the anterior part of the eyeball.

Functions:

Protective: mechanical (from exposure to dust, harmful substances, small foreign bodies), barrier (from the penetration of microorganisms), moisturizing (protects from drying out);

Suction; nourishing

Topographic-anatomical sections of the conjunctiva

The tarsal region begins from the inner (posterior) edge of the eyelids and covers the cartilaginous fibrous connective plate, tightly connecting to it. It is represented by stratified columnar epithelium with the inclusion of goblet cells - single-celled glands that secrete mucus. In the normal state of the conjunctiva, the glands located in the cartilage perpendicular to the edge of the eyelid are visible through it.

The orbital section begins at the level of the edge of the cartilage (superior edge on the upper eyelid and lower edge on the lower eyelid), loosely connected with the underlying subconjunctival tissue, in which there are single follicles, pseudopapillae and adenoid tissue, and reaches the fornix region. There are goblet cells, mucous glands, tubular glands of Henle, and in the conjunctiva of the upper eyelid there are a large number of lacrimal glands of Krause.

The transitional section is represented by the upper fornix - the place of transition of the conjunctiva from the eyeball to the posterior surface of the upper eyelid and the lower fornix - the place of transition of the conjunctiva from the eyeball to the posterior surface of the lower eyelid. The department is a multilayered squamous epithelium with a significant number of glands that produce mucus and tears. Under the epithelium there is a large amount of adenoid tissue with follicles and papillae. Here the epithelium is very loosely connected to the underlying tissue, resulting in free mobility of the eyeball. The depth of the upper arch is about 22 mm, the lower - 12 mm.

The scleral, or boulevard, section is formed by stratified squamous epithelium and begins in the area of ​​the internal section of the outer limbus. It is loosely connected with the subconjunctival substance, very poor adenoid tissue.

The limbal part of the conjunctiva almost imperceptibly passes into the stratified squamous epithelium of the cornea. In this section, the epithelium does not have adenoid tissue and is firmly connected to the halo along its entire length.

The lunate section is a vestige of the third century. Adjacent to this section is the lacrimal caruncle with rudiments of sweat and sebaceous glands and small hair follicles from which delicate hairs grow. A lake of tears appears in this area.

All these sections of the connective membrane form the conjunctival sac - the space between the conjunctiva of the eyelids and the conjunctiva of the eyeball.

Its capacity with closed eyelids is up to 2 drops. It, together with the lacrimal lake, is like an intermediate link between the lacrimal gland and the lacrimal drainage system.

Ontogenesis. The conjunctiva in early childhood is relatively dry, thin and tender. The lacrimal and mucous glands are insufficiently developed and small in number, as well as the subconjunctival tissue is insignificant; there are no follicles and papillae.

Blood supply to the conjunctiva: branches of the lateral and medial arteries of the eyelids, branches of the marginal arteries of the arches of the eyelids, from which the posterior conjunctival vessels are formed; branches from the anterior ciliary arteries (continuation of the muscular ones), from which the anterior conjunctival vessels are formed. The anterior and posterior arteries anastomose widely, especially in the area of ​​the conjunctiva of the fornix. Thanks to the abundant anastomoses that create an external and deep vascular network, the nutrition of the connective membrane is quickly restored in case of disturbances. The outflow of blood occurs through the facial and anterior ciliary veins. The conjunctiva also has a developed network of lymphatic vessels running from the limbus to the preauricular and submandibular lymph nodes.

Innervation: nerve endings from the first and second branches of the trigeminal nerve.

17. Eyelids

The eyelids are semicircular flaps that make up the anterior wall of the orbit; when closed, they completely isolate the eye from the environment.

Function: protective.

The palpebral fissure is located between the free edges of the eyelids. Through it the anterior surface of the eyeball is visible. The lateral angle of the fissure is sharp, the medial angle is rounded. The gap in adults is almond-shaped, on average 30 mm long, up to 8-15 mm wide (in newborns the gap is narrow, 16.5 mm long, 4 mm wide).

The upper eyelid is larger than the lower; its upper border is the eyebrow. Along the edges of the eyelids, hard hairs grow in three or four rows - eyelashes, which protect the eye from small foreign particles.

Topographic-anatomical layers of the eyelids: skin, muscle, connective tissue (cartilaginous) and conjunctival.

The skin layer is superficial. The skin of the eyelids is thin, delicate (in children - with good turgor, the underlying vessels are visible through it). Unlike the skin of other areas, there is very loose subcutaneous tissue, devoid of fat. Thanks to this, the skin is not fused to the muscles of the eyelids and is easily displaced. The looseness of the subcutaneous tissue explains the rapid occurrence of eyelid edema during local inflammatory processes, as well as during disorders of local and general (especially venous) circulation. With age, the skin of the eyelids becomes rougher, wrinkled, and flabby.

The muscle layer is located under the skin of the eyelids and is represented by the circular muscle. The orbital part of the orbicularis muscle is a circular sphincter, the fibers of which start from the edge of the orbit of the convenient process of the upper jaw, pass subcutaneously outward, go around the outer corner and return to the beginning of their attachment.

Function: closing (squeezing) the eyelids.

The palpebral part is represented by a group of muscle fibers starting at the medial and ending at the lateral commissure of the eyelids. Its main function is the closure of the palpebral fissure, including blinking movements. In the inner corner, two fiber legs extend from both ends of the palpebral part of the muscle, which cover the lacrimal sac in front and behind (Horner's lacrimal muscle).

During blinking, they contract and relax, creating a vacuum in the bag and causing tear fluid to be sucked from the lacrimal lake through the lacrimal canaliculi. Part of the fibers of the palpebral part of the muscle, located parallel to the edge of the eyelid, covering the roots of the eyelashes and excretory ducts, forms the ciliary muscle of the meibomian glands - the Riolan muscle, which helps remove their secretions.

The connective tissue layer of the eyelids is represented by a convex outward semilunar plate (tarsal), which, due to its dense consistency, is called cartilage, which gives the eyelids their shape. With the help of horizontally located ligaments (internal and external), the cartilage of the eyelids is attached to the edges of the bony part of the periosteum. The middle tendon part of the muscle that lifts the upper eyelid is woven into the upper edge of the cartilage. The tendon of the upper part of this muscle is attached to the orbicularis muscle and the skin of the eyelid, and the lower part is attached to the conjunctiva of the upper fornix.

The eyelids are innervated by the first and second branches of the trigeminal nerve, the facial and sympathetic nerves. The skin of the upper eyelid receives innervation from the supraorbital, frontal, supra- and infratrochlear and lacrimal nerves, and the lower eyelid - from the infraorbital. The orbicularis muscle is innervated by the facial nerve; the muscle that lifts the upper eyelid is the oculomotor nerve; The tarsal muscle receives innervation from the cervical sympathetic trunk.

Article from the book: .

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 clefts, 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. Consequently, it practically does not refract rays. Moisture is 99% water.

Most of the dense residue consists of anorganic substances: anions (chlorine, carbonate, sulfate, phosphate) and cations (sodium, potassium, calcium, magnesium). Most of the moisture contains 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 humor contains glucose - 0.098%, ascorbic acid, which is 10-15 times more than in the blood, and lactic acid, because the latter is formed during 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 secondary moisture - a new portion of liquid formed after 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, vitreous body, and partially the cornea. In this regard, constant renewal of moisture is necessary, i.e. outflow of waste liquid and influx of freshly formed liquid.

The fact that intraocular fluid is constantly exchanged in the eye was already 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 mostly enters the posterior chamber. The posterior chamber is bounded by the posterior surface of the iris, the ciliary body, the zonules of Zinn, and the extrapupillary portion of the anterior lens capsule. Its depth in different sections varies from 0.01 to 1 mm. From the posterior chamber, through the pupil, the fluid enters the anterior chamber - a space limited in front by the posterior surface of the iris and lens. Due to the valve action of the pupillary edge of the iris, moisture cannot return from the anterior chamber back to the posterior chamber. Next, the waste aqueous humor with tissue metabolic products, pigment particles, and cell fragments is removed from the eye through the anterior and posterior outflow tracts. The anterior outflow tract is the Schlemm's canal system. Fluid enters Schlemm's canal through the anterior chamber angle (ACA), an area limited 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 to aqueous humor leaving the eye is trabecular apparatus.

In section, the trabecula has a triangular shape. The trabecula has three layers: 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 represent a bundle of collagen fibers covered with endothelium. Between the crossbars there are slots with a diameter of 25 to 75 mu. The uveal plates are attached to Descemet's membrane on one side and to the fibers of the ciliary muscle or the iris on the other.

Corneoscleral layer consists of 8-11 plates. Between the crossbars in this layer there are ellipsoidal holes located perpendicular to the fibers of the ciliary muscle. When the ciliary muscle is tense, the trabecular openings 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. This fabric has fairly wide Sondermann channels ranging from 8 to 25 mu in width.

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

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

Some tubules go directly 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 into the episclera, bypassing the deep veins, are called aqueous veins. In them, for some distance, you can see 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 a two-month-old fetus. In a three-month-old child, the corner is filled with mesoderm cells, and in the peripheral parts of the corneal stroma the cavity of Schlemm’s canal is distinguished. After the formation of Schlemm's canal, a scleral spur grows in the corner. In a four-month fetus, corneoscleral and uveal trabecular tissue differentiates 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 unique 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 that of adults (3.0-3.5 mm). With 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 of 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 secretion 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, and vice versa, a decrease in inflow reduces the outflow to the same extent.

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

The fluid is continuously produced by the ciliary crown with the active participation of the non-pigment epithelium of the retina and, in smaller quantities, 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 angle of the anterior chamber. About 15% of the fluid leaves the eye, seeping through the stroma of the ciliary body and sclera into the uveal and scleral veins - the uveoscleral outflow pathway of the fluid. 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 influence on secretory processes is exerted by changes in pressure and the rate of blood outflow in the vessels of the ciliary body. The outflow of intraocular fluid is regulated by the ciliary muscle – scleral spur – trabecula mechanism. The longitudinal and radial fibers of the ciliary muscle are attached to the scleral spur and trabecula with their anterior ends. When it contracts, the spur and trabecula move posteriorly and inwardly. The tension of the trabecular apparatus increases, and the openings in it and the scleral sinus expand.

And the structures of the anterior chamber.

Intraocular pressure depends on how freely it moves through the anterior chamber.

Its increase accompanies the “green eye disease” - glaucoma. Due to stagnation of fluid, the cornea becomes dull, the pupil dilates, and the lens turns green, deprived of nutrition. Glaucoma also has a latent form and is not always accompanied by high IOP.

Intraocular fluid or aqueous humor is produced by the ciliary body. It is excreted through Schlemm's canal in the corner of the anterior chamber of the eye.

Causes of fluid stagnation:

• changes in the anterior chamber angle:
• vascular neoplasms, diabetic retinopathy;
• plugs of pigment particles, blood cells separated from impact, injury;
• tumor.
• final stage cataract;
• increase in acetylcholine.

Failure in the mechanism of secretion and circulation of moisture increases intraocular pressure and the risk of developing glaucoma.

Risk group

People who are predisposed to accumulation of ocular fluid and high IOP are:

• with diseases of the thyroid, pancreas, pituitary gland, diabetes;
• with lens displacement;
• with severe myopia;
• over 40 years of age;
• with hereditary predisposition.

The causes of stagnation or excess aqueous humor differ between types of glaucoma.

Classification of glaucoma

By origin:

• primary - develops after 40 years, associated with pathological processes inside the eyeball;
• secondary - occurs after injuries, illnesses, operations.

According to the mechanism of increased eye pressure:

• open angle- “silent”, occurs hidden with the free movement of moisture;
• closed angle- “stagnant”, the fluid outlet channel is blocked.

By eye pressure level:

• hypertensive;
• normotensive.

According to the course of the disease:

• stable - the patient’s condition does not change for six months;
• unstabilized - deterioration with repeated studies.

Stages of optic nerve damage:

• initial - no noticeable changes in the visual field;
• developed - narrowing 10° from the fixation point;
• far advanced - limited field of view of 15°;
• terminal - blindness, sometimes light perception is preserved.

Secondary glaucoma occurs with cyclic crises.

Symptoms

The accumulation of fluid inside the eye is not felt. Signs of the condition:

• reduction in lateral vision;
• halos around objects;
• unclear edges of the image.

Symptoms of a crisis:

• acute pain with a sharp increase in IOP;
• vision drops to light perception;
• nausea;
• headache;
• pain radiating under the shoulder blade, in the heart, in the stomach.

The attack must be relieved within 24 hours. Otherwise, adhesions in the tissues of the eye will further complicate the outflow of fluid.

Diagnostics

Basic methods for detecting elevated IOP and glaucoma:

• computer scan.

Measuring eye pressure helps determine abnormalities. Examination of the vessels of the fundus and optic nerve reveals pathology at normal pressure. Computer modeling of the eyeball allows us to trace the dynamics of the disease.

Treatment

At the initial stage of the process, eye drops are prescribed:

• stimulating fluid outflow
• suppress its production.

They can also be combined.

The attack is relieved with drops of Pilocarpine, Timolol, Betaxolol. If after 20 hours the IOP does not decrease, surgery is performed:

• trabeculectomy - surgical formation of a drainage channel;
• iridectomy - partial excision of the iris;
• Optociliary neurectomy - removal of part of the ciliary optic nerve.

Surgical treatment is also prescribed if the conservative method is ineffective.

Complications

Difficulties after surgery:

• overgrowing of the drainage channel;
• hemorrhage;
• time in the seam that allows moisture to pass through;
• deviation of the outlet channel.

Untreated glaucoma will lead to gradual loss of vision. Glaucomocyclic crisis causes irreversible changes in tissues, during which it is impossible to reduce the pressure. The patient loses an eye.

Forecast

The outcome of treatment depends on the stage, type of disease, and anatomy of the eye. Surgery for congenital glaucoma is effective in 80% of cases. At the initial stage of primary glaucoma, eye pressure can be reduced to normal. But to prevent relapse, the patient must follow the doctor’s recommendations and prevention rules.

Prevention

How to prevent recurrence of glaucoma:

• undergo an examination every 3 months;
• avoid darkness;
• when working at the computer or watching TV, turn on the lamp;
• watch TV no more than 3 hours a day;
• give up alcohol and smoking;
• wear safety glasses with green lenses;
• Perform eye massage daily;
• refuse heavy physical activity.

The diet should include fish, vegetables, but you should limit the sugar content and give up coffee.

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Vision is restored up to 90%

The eye is a closed cavity bounded by the outer capsule (sclera and cornea). There is an exchange of fluids in the eye - their inflow and outflow. The main place in their products is occupied by the ciliary body. The fluid it produces enters the posterior chamber of the eye, then passes through the pupil into the anterior chamber, from where, through the angle of the anterior chamber and Schlemm’s canal, it enters the venous network (see Fig. 4). Apparently, the iris also takes part in this. In a normal eye, there is a strict correspondence between the inflow and outflow of ocular fluids, and the eye has a certain density, which is called intraocular pressure. It is designated by the letter T (the initial letter of the Latin word tensio - pressure). Intraocular pressure is measured in millimeters of mercury and depends on many factors. The main factors are the amount of intraocular fluid and blood in the internal vessels of the eye. The technique for studying intraocular pressure is described in Chapter IV.

Sometimes, for various reasons, there is a disproportion between the inflow and outflow of intraocular fluids and intraocular pressure increases, and glaucoma develops. Among the causes of blindness, glaucoma is in first place worldwide - it accounts for up to 23% of blind people.

Glaucoma is a Greek word meaning “green.” Indeed, during an acute attack, the pupil becomes slightly greenish, the eye seems to be filled with greenish water. Hence its name in folk medicine “green water”. There are two types of glaucoma - primary and secondary. Primary glaucoma is those cases of the disease where the cause of the increase in intraocular pressure is unknown. In secondary glaucoma, the reasons for the increase in intraocular pressure are clear (blood in the anterior chamber, circular synechia, corneal scar fused to the iris, etc.). We will consider only primary glaucoma, since the causes and treatment of secondary glaucoma are clear.

The following 3 signs are characteristic of glaucoma: increased intraocular pressure (the main symptom), decreased visual function and excavation of the optic nerve head.

Intraocular pressure is normally 18-27 mmHg. Art. It can change for many reasons. Pressure equal to 27 mm Hg. Art., already makes you wary, but if it is higher, then you need to talk about glaucoma.

With increased intraocular pressure, the light-receiving elements of the retina are damaged, central and peripheral vision decreases. This drop can be short-term, since the increased pressure causes swelling of the cornea (it becomes somewhat dull, its surface looks like foggy glass); Retinal edema usually occurs. The swelling goes away and vision is restored. When the nerve elements of the retina are damaged due to high intraocular pressure, vision loss is permanent. It can no longer be restored, even if the pressure returns to normal. This moment determines the treatment tactics for a patient with glaucoma. With glaucoma, peripheral vision is also impaired (narrowing of the visual field). Glaucoma is characterized by a narrowing of the visual field on the nasal side; this pathology is called “nasal jump”. The field of view can be narrowed and concentric on all sides.

The thinnest part of the sclera is the cribriform plate. Due to increased intraocular pressure, the nerve tissue on the optic disc atrophies, and the cribriform plate itself bends back. Normally, this is a flat place, but with glaucoma, a depression is formed, shaped like a rinse cup. At its bottom, an atrophic optic disc is visible, and on the sides there are bent vessels - excavation of the optic disc.