Vessels of the eye. Blood supply to the eye. Arteries and veins of the eyeball Methods for diagnosing vascular diseases of the eye

The outflow of venous blood directly from the eyeball occurs mainly through the internal (retinal) and external (ciliary) vascular systems of the eye. The first is represented by the central retinal vein, the second by the four vortic veins (see Fig. 3.10 and 3.11).

Central retinal vein (v.centralis retinae) accompanies the corresponding artery and has the same distribution as it. In the optic nerve trunk it connects with the central retinal artery in the so-called central connecting cord through processes extending from the pia mater. It flows either directly into the cavernous sinus ( sinus cavernosus), or first into the superior ophthalmic vein ( v. oplithalmica superior).

Vorticose veins (vv.vorticosae) drain blood from the choroid, ciliary processes and most of the muscles of the ciliary body, as well as the iris. They cut through the sclera in an oblique direction in each of the quadrants of the eyeball at the level of its equator. The upper pair of vorticose veins flows into the superior ophthalmic vein, the lower one into the inferior one.

The outflow of venous blood from the auxiliary organs of the eye and orbit occurs through the vascular system, which has a complex structure and is characterized by a number of clinically very important features (Fig. 3.14). All veins of this system are devoid of valves, as a result of which the outflow of blood through them can occur both towards the cavernous sinus, i.e., into the cranial cavity, and into the system of veins of the face, which are connected with the venous plexuses of the temporal region of the head, the pterygoid process, and the pterygopalatine fossa , condylar process of the mandible. In addition, the venous plexus of the orbit anastomoses with the veins of the ethmoid sinuses and the nasal cavity. All these features make it possible for a dangerous spread of purulent infection from the skin of the face (boils, abscesses, erysipelas) or from the paranasal sinuses into the cavernous sinus.

Ophthalmic artery, a. ophthalmica (Fig.; see Fig., ), – a paired large vessel. It is directed through the optic canal into the orbit, lying outward from the optic nerve. In the orbit, the optic nerve crosses, passing between it and the superior rectus muscle, and goes to the medial wall of the orbit. Having reached the medial corner of the eye, the ophthalmic artery splits into terminal branches: supratrochlear artery, a. supratrochlearis, And dorsal nasal artery, a. dorsalis nasi. Along its path, the ophthalmic artery gives off branches (see “Organ of vision”).

1. Lacrimal artery, a. lacrimalis, starts from the ophthalmic artery at the place where it passes through the optic canal. In the orbit, the artery, located along the upper edge of the rectus lateral muscle and heading to the lacrimal gland, gives branches to the lower and upper eyelids - lateral arteries of the eyelids, aa. palpebrales laterales, and to the conjunctiva. The lateral arteries of the eyelids anastomose with medial arteries of the eyelids, aa. palpebrales mediales, using the anastomotic branch, r. anastomoticus, and form arches of the upper and lower eyelids, arcus palpebrales superior et inferior.

In addition, the lacrimal artery has an anastomotic branch with the middle meningeal artery, r. anastomoticus cum a. meningea media.

2. Central retinal artery, a. centralis retinae, at a distance of 1 cm from the eyeball, enters the thickness of the optic nerve and, having reached the eyeball, breaks up in the retina into several radiating thin branches.

3. Short and long posterior ciliary arteries, aa. ciliares posteriores breves et longae, follow along the optic nerve, penetrate the eyeball and are directed to the choroid.

4. Muscular arteries, aa. musculares, - upper and lower - break up into smaller branches that supply blood to the muscles of the eyeball. Sometimes they can arise from the lacrimal artery.

Originate from muscle branches anterior ciliary arteries, aa. ciliares anteriores, only 5-6. They are directed to the white membrane of the eyeball and, penetrating through it, end in the thickness of the iris. The branches of these arteries are:

• anterior conjunctival arteries, aa. conjunctivales anteriores, supplying blood to the conjunctiva covering the eyeball and anastomosing with the posterior conjunctival arteries;
• , which lie in the conjunctiva covering the eyelids, supply them with blood and anastomose with the arches of the upper and lower eyelids;
• episcleral arteries, aa. episclerales, supplying blood to the sclera and anastomosing in its posterior sections with short posterior ciliary arteries.

5. Posterior ethmoidal artery, a. ethmoidalis posterior(see Fig.,), like the anterior one (see below), departs from the ophthalmic artery in the area where it is located along the medial wall of the orbit, in the region of the posterior third of the orbit, and, passing through the opening of the same name, branches in the mucous membrane of the posterior ethmoid cells, giving off several small branches to the mucous membrane of the posterior sections of the nasal septum.

6. Anterior ethmoidal artery, a. ethmoidalis anterior(see Fig.,), penetrates through the hole of the same name into the cranial cavity and gives off in the area of ​​the anterior cranial fossa anterior meningeal branch, r. meningeus anterior. Then the artery is directed downwards, passes through the opening of the cribriform plate of the ethmoid bone into the nasal cavity, where it supplies the mucous membrane of the anterior part of the side walls, giving lateral anterior nasal branches, rr. nasales anteriores laterales, anterior septal branches, rr. septales anteriores, as well as branches to the mucous membrane of the anterior ethmoid cells.

7. Supraorbital artery, a. supraorbitalis, is located directly under the upper wall of the orbit, between it and the muscle that lifts the upper eyelid. Moving forward, it bends around the supraorbital margin in the area of ​​the supraorbital notch and follows upward to the forehead, where it supplies the orbicularis oculi muscle, the frontal belly of the occipitofrontal muscle and the skin. The terminal branches of the supraorbital artery anastomose with a. temporalis superficialis.

8. Medial arteries of the eyelids, aa. palpebrales mediales, are located along the free edge of the eyelids and anastomose with the lateral arteries of the eyelids (rr. a. lacrimalis), forming the vascular arches of the upper and lower eyelids. In addition, they give away two or three thin posterior conjunctival arteries, aa. conjunctivales posteriores.

9. Supratrochlear artery, a. supratrochlearis, is one of the terminal branches of the ophthalmic artery, located medially from the supraorbital artery. It goes around the supraorbital edge and, going upward, supplies the skin of the medial parts of the forehead and muscles. Its branches anastomose with the branches of the artery of the same name on the opposite side.

10. Dorsal artery of the nose, a. dorsalis nasi, like the supratrochlear artery, is the terminal branch of the ophthalmic artery. It goes anteriorly, lying over the medial ligament of the eyelid, gives off a branch to the lacrimal sac and exits onto the dorsum of the nose. Here it connects with the angular artery (branch of a. facialis), thus forming an anastomosis between the systems of the internal and external carotid arteries (see Fig.).

• lacrimal artery
• central retinal artery
• muscle branches,
• posterior ciliary arteries,
• long and short and a number of others.

Central retinal artery, moving away from the ophthalmic artery, enters the optic nerve at a distance of 10-12 mm from the eyeball and then, together with it, into the eyeball, where it divides into branches that supply the medulla of the retina. They belong to the terminal ones, which do not have anastomoses with neighboring branches.

Ciliary artery system. The ciliary arteries are divided into posterior and anterior. The posterior ciliary arteries, moving away from the ophthalmic artery, approach the posterior segment of the eyeball and, passing the sclera around the optic nerve, are distributed in the vascular tract. In the posterior ciliary arteries there are four to six short ones. Short ciliary arteries, having passed the sclera, immediately break up into a large number of branches and form the choroid itself. Before passing through the sclera, they form a vascular corolla around the base of the optic nerve.

The long posterior ciliary arteries, penetrating inside the eye, run between the sclera and the choroid in the direction of the horizontal meridian to the ciliary body. At the anterior end of the ciliary muscle, each artery is divided into two branches, which run concentrically with the limbus and, meeting with the same branches of the second artery, form a vicious circle - greater arterial circle of the iris. From the large arterial circle of the iris, branches extend into its tissue. At the border of the ciliary and pupillary zones of the iris, they form a small arterial circle.

Anterior ciliary arteries are a continuation of the muscular arteries. Without ending at the tendon of the four rectus muscles, the anterior ciliary arteries go further along the surface of the eyeball in the episcleral tissue at a distance of 3-4 mm from the limbus and penetrate the eyeball (seven tables). Anastomosing with other long ciliary arteries, they participate in the formation of the systemic circulation of the iris and in the blood supply to the ciliary body.

The upper pair of vorticose veins flows into the superior ophthalmic vein, the lower one into the inferior one.

Outflow of venous blood from the auxiliary organs of the eye and orbit occurs through the vascular system, which has a complex structure and is characterized by a number of clinically very important features. All veins of this system are devoid of valves, as a result of which the outflow of blood through them can occur both towards the cavernous sinus, i.e. into the cranial cavity, and into the system of veins of the face, which are connected with the venous plexuses of the temporal region of the head, pterygoid process, pterygopalatine fossa , condylar process of the lower Jaw. In addition, the venous plexus of the orbit anastomoses with the veins of the ethmoid sinuses and the nasal cavity. All these features make it possible for a dangerous spread of purulent infection from the skin of the face (boils, abscesses, erysipelas) or from the paranasal sinuses into the cavernous sinus. Thus, most of the blood of the eye and orbit goes back to the system of cerebral sinuses, a smaller part goes forward to the system of veins of the face. Veins of the orbit do not have valves.

Venous system of the organ of vision. The outflow of venous blood directly from the eyeball occurs mainly through the internal (retinal) and external (ciliary) vascular systems of the eye. The first is represented by the central retinal vein, the second by four vorticose veins.

Central retinal vein accompanies the corresponding artery and has the same distribution as it. In the optic nerve trunk, it connects with the central retinal artery in the so-called central connecting cord through processes extending from the pia mater. It flows either directly into the cavernous sinus or first into the superior ophthalmic vein.

Vorticose veins drain blood from the choroid, ciliary processes and most of the muscles of the ciliary body, as well as the iris. They cut through the sclera in an oblique direction in each of the quadrants of the eyeball at the level of its equator. The supply of sensory fibers is carried out by the optic nerve, which originates from the gasserian ganglion. Entering the orbit through the superior orbital fissure, the optic nerve divides into the nasociliary, lacrimal and frontal.

Any disturbances in the blood circulation of the eyeballs immediately lead to disruption of their functioning, therefore the eyes are equipped with a rich, branched network of blood vessels that ensure the functioning and nutrition of all its tissues.

The supply of blood to the eyeball is carried out by the main line of the internal carotid artery, which is the ophthalmic artery, which supplies the eye and its auxiliary apparatus. Nutrition of tissues is directly provided by a network of capillary vessels. In this case, the greatest importance is given to the vessels that supply the eyes together with: the central retinal artery and the posterior short ciliary arteries. Disruption of blood flow in them can lead to decreased vision, even absolute vision.

The ocular venous network completely repeats the structure of the arteries. A feature of the ophthalmic veins is the absence of valves in them, which limit the reverse flow of blood and connections of the venous network of the face, veins, and further, the brain. Accordingly, purulent inflammatory processes that occur on the face can spread through the venous blood flow towards the brain, which is potentially life-threatening.

Arterial system of the eye. Structure

The main role in the blood supply to the eye is assigned to one of the main highways of the internal carotid artery, which is the ophthalmic artery. It enters the orbit with the optic nerve through its canal.

Several main branches go into the orbit from it: the lacrimal artery, the central retinal artery, the posterior short and long ciliary arteries, the supraorbital artery, the muscular arteries, the posterior and anterior ethmoidal arteries, the supratrochlear artery, the internal arteries, and the nasal dorsum artery.

The task of the central retinal artery is to participate in the nutrition of the optic nerve, through a small branch, which it gives off to the central artery of the optic nerve. Passing inside the optic nerve, the artery pierces its disc and exits into the fundus. Here it divides into branches and forms a dense network of vessels that nourish the four inner layers of the retina, as well as the intraocular part of the optic nerve itself.

Sometimes in the fundus you can identify an additional blood vessel that supplies the area. This is the cilioretinal artery, a branch of the posterior short ciliary artery. If the blood flow of the central retinal artery is disrupted, this branch can continue to supply the macular area without reducing central vision.

The posterior short ciliary arteries also have branches arising from the ophthalmic artery. Their number ranges from 6 to 12, all of them lie in the area surrounding the optic nerve, forming an arterial circle, which participates in the blood supply to part of the optic nerve after it leaves the eye. In addition, they ensure blood flow in the choroid of the eye. As for the posterior short ciliary arteries, they have no connection with the ciliary body and the iris, due to which the processes of inflammation in the anterior or posterior segment of the eye occur relatively in isolation.

Two branches depart from the ophthalmic artery, these are the long posterior ciliary arteries. They pass through the sclera on the side of the optic nerve, bypass the perivascular space and reach. At this point they join the anterior ciliary arteries - branches of the muscular arteries, with partial addition of the posterior short ciliary arteries to form the large arterial circle of the iris membrane. The circle is localized at the root of the iris and directs its branches to the pupil. The pupillary and ciliary bands of the iris at the junction form a small arterial circle. These two arterial circles (large and small) supply blood to the ciliary body and iris.

Muscular arteries supply blood to all the muscles of the eye, however, the arteries of all rectus muscles have branches, the so-called anterior ciliary arteries. They, in turn, dividing, form a network of vessels in the limbus, where they join the posterior long ciliary arteries.

From the inside of the skin, their internal arteries approach the eyelids, which then spread over the surface of the eyelids. Here they join the external arteries of the eyelids, forming branches of the lacrimal arteries. The result of the fusion is the lower and upper arterial arches of the eyelids, which provide their blood supply.

Several branches for blood supply depart from the arteries to the back surface of the eyelids - these are the posterior conjunctival arteries. At the fornix of the conjunctiva, the anterior conjunctival arteries join them through the branches of the anterior ciliary arteries, which are involved in feeding the conjunctiva of the eye.

The lacrimal artery is occupied by the blood supply to the nearby lacrimal gland, as well as the external and superior rectus muscles, in addition, it takes part in the nutrition of the eyelids. The supraorbital artery emerges through the supraorbital notch in the frontal bone, carrying blood to the area of ​​the upper eyelid together with the supratrochlear artery.

The ethmoidal arteries (anterior and posterior) are busy in the process of feeding the nasal mucosa, as well as the ethmoidal labyrinth.

The blood supply to the eye is also created by other vessels: the infraorbital artery, which is a branch of the maxillary artery (takes part in supplying the lower eyelid, as well as the rectus and oblique muscles, the lacrimal gland and the lacrimal sac), in addition, there is a facial artery that gives off the angular artery, which nourishes the inner area of ​​the eyelids.

Venous system of the eye. Structure

The vein system is occupied by the outflow of blood from the tissues of the eye. The central retinal vein provides the outflow of blood from the structures supplied by the corresponding artery, then it flows into the cavernous sinus or into the superior ophthalmic vein.

Vorticose veins provide blood drainage from the choroid of the organ of vision. Four vorticose veins are occupied in the corresponding segment of the eye, the two upper veins further connect with the superior ophthalmic vein, and the two lower ones with the inferior one.

Then the venous outflow from the supporting organs of the orbit and eye, in essence, repeats the arterial blood supply, although everything happens in the reverse order. The main part of the veins goes to the superior ophthalmic vein, which leaves the orbit through the superior orbital fissure; a much smaller part goes to the inferior ophthalmic vein, which often has two branches. One branch joins the superior ophthalmic vein, and the second leaves through the inferior orbital fissure.

The absence of valves in the veins and free communication between the venous systems of the face, eye, and brain are a feature of the venous system of the eye. In this case, venous outflow is possible both in the direction of the face and in the direction of the brain, which creates potentially life-threatening situations in cases of purulent inflammatory processes.

Method for diagnosing pathologies of eye vessels

– inspection and assessment of the condition of blood vessels in the fundus.

Fluorescent - examination of the vessels of the retina using a contrast agent.

Doppler ultrasound is a study of blood volume in vessels.

Rheography is an assessment of the outflow and inflow of blood per unit of time.

Symptoms of vascular diseases of the eyes

Disruption of blood flow to the central retinal artery or its branches.

Formation of blood clots in the central retinal vein and its branches.

Posterior ischemic neuropathy.

Anterior ischemic neuropathy.

Papillopathy.

Ocular ischemic syndrome.

When there are disturbances in blood flow, swelling and hemorrhages in the area of ​​the macula, as well as disturbances in the blood flow of the vessels of the optic nerve, vision loss occurs.

If the changes that occur in the retina do not affect the macula area, then only peripheral vision is impaired.

■ Eye development

■ Eye socket

■ Eyeball

Outer shell

Middle shell

Inner layer (retina)

Contents of the eyeball

Blood supply

Innervation

Visual pathways

■ Auxiliary apparatus of the eye

Oculomotor muscles

Eyelids

Conjunctiva

Lacrimal organs

EYE DEVELOPMENT

The eye rudiment appears in the 22-day embryo as a pair of shallow invaginations (ocular grooves) in the forebrain. Gradually, the invaginations increase and form outgrowths - eye vesicles. At the beginning of the fifth week of fetal development, the distal part of the optic vesicle is depressed, forming the optic cup. The outer wall of the optic cup gives rise to the retinal pigment epithelium, and the inner wall gives rise to the remaining layers of the retina.

At the stage of the optic vesicles, thickenings appear in the adjacent areas of the ectoderm - lens placoids. Then the formation of lens vesicles occurs and they are drawn into the cavity of the optic cups, while the anterior and posterior chambers of the eye are formed. The ectoderm above the optic cup also gives rise to the corneal epithelium.

In the mesenchyme immediately surrounding the optic cup, the vascular network develops and the choroid is formed.

Neuroglial elements give rise to the myoneural tissue of the sphincter and pupillary dilator. Outside the choroid, dense fibrous unformed scleral tissue develops from the mesenchyme. Anteriorly, it becomes transparent and passes into the connective tissue part of the cornea.

At the end of the second month, lacrimal glands develop from the ectoderm. Oculomotor muscles develop from myotomes, represented by striated muscle tissue of the somatic type. The eyelids begin to form as folds of skin. They quickly grow towards each other and grow together. Behind them a space is formed, which is lined with stratified prismatic epithelium - the conjunctival sac. At the 7th month of intrauterine development, the conjunctival sac begins to open. Eyelashes, sebaceous and modified sweat glands form along the edge of the eyelids.

Features of the structure of the eyes in children

In newborns, the eyeball is relatively large, but short. By the age of 7-8 years, the final eye size is established. A newborn has a relatively larger and flatter cornea than an adult. At birth, the shape of the lens is spherical; throughout life, it grows and becomes flatter, which is due to the formation of new fibers. In newborns, there is little or no pigment in the stroma of the iris. The bluish color of the eyes is given by the translucent posterior pigment epithelium. When pigment begins to appear in the parenchyma of the iris, it acquires its own color.

ORIENTAL

Orbit(orbita), or orbit, is a paired bone formation in the form of a depression in the front of the skull, resembling a tetrahedral pyramid, the apex of which is directed posteriorly and somewhat inward (Fig. 2.1). The orbit has inner, upper, outer and lower walls.

The inner wall of the orbit is represented by a very thin bone plate that separates the orbital cavity from the cells of the ethmoid bone. If this plate is damaged, air from the sinus can easily pass into the orbit and under the skin of the eyelids, causing emphysema. In the top-inside

Rice. 2.1.Orbital structure: 1 - superior orbital fissure; 2 - small wing of the main bone; 3 - optic nerve channel; 4 - posterior ethmoidal opening; 5 - orbital plate of the ethmoid bone; 6 - anterior lacrimal ridge; 7 - lacrimal bone and posterior lacrimal crest; 8 - fossa of the lacrimal sac; 9 - nasal bone; 10 - frontal process; 11 - lower orbital margin (upper jaw); 12 - lower jaw; 13 - inferior orbital groove; 14. infraorbital foramen; 15 - inferior orbital fissure; 16 - zygomatic bone; 17 - round hole; 18 - large wing of the main bone; 19 - frontal bone; 20 - upper orbital margin

In the lower angle, the orbit borders the frontal sinus, and the lower wall of the orbit separates its contents from the maxillary sinus (Fig. 2.2). This makes it likely that inflammatory and tumor processes will spread from the paranasal sinuses into the orbit.

The inferior wall of the orbit is often damaged by blunt trauma. A direct blow to the eyeball causes a sharp increase in pressure in the orbit, and its lower wall “falls in,” dragging the contents of the orbit into the edges of the bone defect.

Rice. 2.2.Orbit and paranasal sinuses: 1 - orbit; 2 - maxillary sinus; 3 - frontal sinus; 4 - nasal passages; 5 - ethmoid sinus

The tarso-orbital fascia and the eyeball suspended on it serve as the anterior wall delimiting the orbital cavity. The tarso-orbital fascia is attached to the orbital margins and cartilages of the eyelids and is closely associated with Tenon's capsule, which covers the eyeball from the limbus to the optic nerve. In front, Tenon's capsule is connected to the conjunctiva and episclera, and behind it separates the eyeball from the orbital tissue. Tenon's capsule forms the sheath for all extraocular muscles.

The main contents of the orbit are fatty tissue and extraocular muscles; the eyeball itself occupies only a fifth of the orbital volume. All formations located anterior to the tarso-orbital fascia lie outside the orbit (in particular, the lacrimal sac).

Connection of the orbit with the cranial cavity carried out through several holes.

The superior orbital fissure connects the orbital cavity with the middle cranial fossa. The following nerves pass through it: oculomotor (III pair of cranial nerves), trochlear (IV pair of cranial nerves), orbital (first branch of the V pair of cranial nerves) and abducens (VI pair of cranial nerves). The superior ophthalmic vein also passes through the superior orbital fissure, the main vessel through which blood flows from the eyeball and orbit.

Pathology in the area of ​​the superior orbital fissure can lead to the development of the “superior orbital fissure” syndrome: ptosis, complete immobility of the eyeball (ophthalmoplegia), mydriasis, paralysis of accommodation, impaired sensitivity of the eyeball, skin of the forehead and upper eyelid, difficulty in venous outflow of blood, which causes the occurrence of exophthalmos.

The orbital veins pass through the superior orbital fissure into the cranial cavity and empty into the cavernous sinus. Anastomoses with facial veins, primarily through the angular vein, as well as the absence of venous valves, contribute to the rapid spread of infection from the upper part of the face into the orbit and further into the cranial cavity with the development of cavernous sinus thrombosis.

The inferior orbital fissure connects the orbital cavity with the pterygopalatine and temporomandibular fossae. The inferior orbital fissure is closed by connective tissue into which smooth muscle fibers are woven. When the sympathetic innervation of this muscle is disrupted, enophthalmos occurs (recession of the eyes).

no apple). Thus, when the fibers running from the superior cervical sympathetic ganglion to the orbit are damaged, Horner's syndrome develops: partial ptosis, miosis and enophthalmos. The optic nerve canal is located at the apex of the orbit in the lesser wing of the sphenoid bone. Through this canal the optic nerve enters the cranial cavity and the ophthalmic artery enters the orbit - the main source of blood supply to the eye and its auxiliary apparatus.

EYEBALL

The eyeball consists of three membranes (outer, middle and inner) and contents (vitreous body, lens, and aqueous humor of the anterior and posterior chambers of the eye, Fig. 2.3).

Rice. 2.3.Diagram of the structure of the eyeball (sagittal section).

Outer shell

Outer, or fibrous, membrane of the eye (tunica fibrosa) represented by the cornea (cornea) and sclera (sclera).

Cornea - the transparent avascular part of the outer membrane of the eye. The function of the cornea is to conduct and refract light rays, as well as protect the contents of the eyeball from adverse external influences. The diameter of the cornea is on average 11.0 mm, thickness - from 0.5 mm (in the center) to 1.0 mm, refractive power - about 43.0 diopters. Normally, the cornea is transparent, smooth, shiny, spherical and highly sensitive tissue. The impact of unfavorable external factors on the cornea causes a reflexive contraction of the eyelids, providing protection to the eyeball (corneal reflex).

The cornea consists of 5 layers: anterior epithelium, Bowman's membrane, stroma, Descemet's membrane and posterior epithelium.

Front multilayered squamous non-keratinizing epithelium performs a protective function and, in case of injury, completely regenerates within 24 hours.

Bowman's membrane- basement membrane of the anterior epithelium. It is resistant to mechanical stress.

Stroma(parenchyma) cornea makes up up to 90% of its thickness. It consists of many thin plates, between which there are flattened cells and a large number of sensitive nerve endings.

"Descemet's membrane represents the basement membrane of the posterior epithelium. It serves as a reliable barrier to the spread of infection.

Posterior epithelium consists of a single layer of hexagonal cells. It prevents the flow of water from the anterior chamber moisture into the corneal stroma and does not regenerate.

The cornea is nourished by the pericorneal network of vessels, moisture from the anterior chamber of the eye and tears. The transparency of the cornea is due to its homogeneous structure, the absence of blood vessels and a strictly defined water content.

Limbo- the place of transition of the cornea into the sclera. This is a translucent rim, about 0.75-1.0 mm wide. Schlemm's canal is located in the thickness of the limbus. The limbus serves as a good guide when describing various pathological processes in the cornea and sclera, as well as when performing surgical interventions.

Sclera- the opaque part of the outer membrane of the eye, which is white (the tunica albuginea). Its thickness reaches 1 mm, and the thinnest part of the sclera is located at the exit point of the optic nerve. The functions of the sclera are protective and formative. The sclera is similar in structure to the parenchyma of the cornea, however, unlike it, it is saturated with water (due to the absence of epithelial cover) and is opaque. Numerous nerves and vessels pass through the sclera.

Middle shell

The middle (choroid) layer of the eye, or uveal tract (tunica vasculosa), consists of three parts: the iris (iris), ciliary body (corpus ciliare) and choroids (choroidea).

Iris serves as the automatic diaphragm of the eye. The thickness of the iris is only 0.2-0.4 mm, the smallest is at the point of its transition to the ciliary body, where the iris can be torn off due to injury (iridodialysis). The iris consists of connective tissue stroma, blood vessels, epithelium covering the iris in front and two layers of pigment epithelium behind, ensuring its opacity. The stroma of the iris contains many chromatophore cells, the amount of melanin in which determines the color of the eyes. The iris contains a relatively small number of sensitive nerve endings, so inflammatory diseases of the iris are accompanied by moderate pain.

Pupil- a round hole in the center of the iris. By changing its diameter, the pupil regulates the flow of light rays falling on the retina. The size of the pupil changes under the action of two smooth muscles of the iris - the sphincter and the dilator. The sphincter muscle fibers are arranged in a ring and receive parasympathetic innervation from the oculomotor nerve. The radial dilator fibers are innervated from the superior cervical sympathetic ganglion.

Ciliary body- part of the choroid of the eye, which in the form of a ring passes between the root of the iris and the choroid. The border between the ciliary body and the choroid passes along the dentate line. The ciliary body produces intraocular fluid and participates in the act of accommodation. The vascular network is well developed in the area of ​​the ciliary processes. The formation of intraocular fluid occurs in the ciliary epithelium. Ciliary

the muscle consists of several bundles of multidirectional fibers attached to the sclera. By contracting and pulling anteriorly, they weaken the tension of the ligaments of Zinn, which go from the ciliary processes to the lens capsule. When the ciliary body is inflamed, the processes of accommodation are always disrupted. The innervation of the ciliary body is carried out by sensory (I branch of the trigeminal nerve), parasympathetic and sympathetic fibers. There are significantly more sensitive nerve fibers in the ciliary body than in the iris, so when it is inflamed, the pain syndrome is pronounced. Choroid- the posterior part of the uveal tract, separated from the ciliary body by a dentate line. The choroid consists of several layers of vessels. A layer of wide choriocapillaris is adjacent to the retina and is separated from it by a thin Bruch membrane. On the outside there is a layer of medium-sized vessels (mainly arterioles), behind which there is a layer of larger vessels (venules). Between the sclera and the choroid there is a suprachoroidal space in which vessels and nerves pass in transit. Pigment cells are located in the choroid, as in other parts of the uveal tract. The choroid provides nutrition to the outer layers of the retina (neuroepithelium). Blood flow in the choroid is slow, which contributes to the occurrence of metastatic tumors and the settling of pathogens of various infectious diseases. The choroid does not receive sensitive innervation, so choroiditis is painless.

Inner layer (retina)

The inner layer of the eye is represented by the retina (retina) - highly differentiated nervous tissue designed to perceive light stimuli. From the optic disc to the dentate line is the optically active part of the retina, which consists of the neurosensory and pigment layers. Anterior to the dentate line, located 6-7 mm from the limbus, it is reduced to the epithelium covering the ciliary body and iris. This part of the retina is not involved in the act of vision.

The retina is fused to the choroid only along the dentate line anteriorly and around the optic disc and along the edge of the macula posteriorly. The thickness of the retina is about 0.4 mm, and in the area of ​​the dentate line and in the macula - only 0.07-0.08 mm. Retinal nutrition

carried out by the choroid and the central retinal artery. The retina, like the choroid, does not have pain innervation.

The functional center of the retina, the macula (macula), is an avascular, rounded area, the yellow color of which is due to the presence of the pigments lutein and zeaxanthin. The most photosensitive part of the macula is the fovea, or foveola (Fig. 2.4).

Retinal structure diagram

Rice. 2.4.Diagram of the structure of the retina. Topography of retinal nerve fibers

The first 3 neurons of the visual analyzer are located in the retina: photoreceptors (first neuron) - rods and cones, bipolar cells (second neuron) and ganglion cells (third neuron). Rods and cones represent the receptor part of the visual analyzer and are located in the outer layers of the retina, directly next to its pigment epithelium. Sticks, located on the periphery, are responsible for peripheral vision - field of view and light perception. cones, the bulk of which are concentrated in the area of ​​the macula, provide central vision (visual acuity) and color perception.

The high resolution of the macula is due to the following features.

The retinal vessels do not pass through here and do not prevent light rays from reaching the photoreceptors.

Only the cones are located in the fovea; all other layers of the retina are pushed to the periphery, which allows light rays to fall directly on the cones.

A special ratio of retinal neurons: in the central fovea there is one bipolar cell per cone, and for each bipolar cell there is its own ganglion cell. This ensures a “direct” connection between photoreceptors and visual centers.

In the periphery of the retina, on the contrary, several rods have one bipolar cell, and several bipolar cells have one ganglion cell. The summation of irritations provides the peripheral part of the retina with exceptionally high sensitivity to the minimum amount of light.

The axons of the ganglion cells converge to form the optic nerve. The optic disc corresponds to the point where nerve fibers exit the eyeball and does not contain light-sensitive elements.

Contents of the eyeball

Contents of the eyeball - vitreous humor (corpus vitreum), lens (lens), as well as aqueous humor of the anterior and posterior chambers of the eye (humor aquosus).

Vitreous body in weight and volume it is approximately 2/3 of the eyeball. This is a transparent avascular gelatinous formation that fills the space between the retina, ciliary body, fibers of the ligament of zinc and the lens. The vitreous body is separated from them by a thin limiting membrane, inside which there is a skeleton of

thin fibrils and gel-like substance. The vitreous body consists of more than 99% water, in which small amounts of protein, hyaluronic acid and electrolytes are dissolved. The vitreous body is quite firmly connected with the ciliary body, the lens capsule, as well as with the retina near the dentate line and in the area of ​​the optic nerve head. With age, the connection with the lens capsule weakens.

Lens(lens) - a transparent, avascular elastic formation, having the shape of a biconvex lens with a thickness of 4-5 mm and a diameter of 9-10 mm. The lens substance has a semi-solid consistency and is enclosed in a thin capsule. The functions of the lens are to conduct and refract light rays, as well as participate in accommodation. The refractive power of the lens is about 18-19 diopters, and at maximum accommodation voltage - up to 30-33 diopters.

The lens is located directly behind the iris and is suspended by fibers of the ligament of zinn, which are woven into the lens capsule at its equator. The equator divides the lens capsule into anterior and posterior. In addition, the lens has anterior and posterior poles.

Under the anterior capsule of the lens is a subcapsular epithelium that produces fibers throughout life. At the same time, the lens becomes flatter and denser, losing its elasticity. The ability to accommodate is gradually lost, since the compacted substance of the lens cannot change its shape. The lens consists of almost 65% water, and the protein content reaches 35% - more than in any other tissue of our body. The lens also contains very small amounts of minerals, ascorbic acid and glutathione.

Intraocular fluid produced in the ciliary body, fills the anterior and posterior chambers of the eye.

The anterior chamber of the eye is the space between the cornea, iris and lens.

The posterior chamber of the eye is a narrow gap between the iris and the lens with the ligament of zinn.

Aqueous moisture participates in the nutrition of the avascular media of the eye, and its exchange largely determines the value of intraocular pressure. The main pathway for the outflow of intraocular fluid is the angle of the anterior chamber of the eye, formed by the root of the iris and the cornea. Through the trabecular system and the layer of internal epithelial cells, the fluid enters Schlemm's canal (venous sinus), from where it flows into the veins of the sclera.

Blood supply

All arterial blood enters the eyeball through the ophthalmic artery (a. ophthalmica)- branches of the internal carotid artery. The ophthalmic artery gives off the following branches going to the eyeball:

The central retinal artery, which supplies the inner layers of the retina;

Posterior short ciliary arteries (6-12 in number), dichotomously branching in the choroid and supplying it with blood;

Posterior long ciliary arteries (2), which pass in the suprachoroidal space to the ciliary body;

The anterior ciliary arteries (4-6) arise from the muscular branches of the ophthalmic artery.

The posterior long and anterior ciliary arteries, anastomosing with each other, form the large arterial circle of the iris. Vessels extend from it in a radial direction, forming a small arterial circle of the iris around the pupil. Due to the posterior long and anterior ciliary arteries, the iris and ciliary body are supplied with blood, a pericorneal network of vessels is formed, which is involved in the nutrition of the cornea. A single blood supply creates the preconditions for simultaneous inflammation of the iris and ciliary body, while choroiditis usually occurs in isolation.

The outflow of blood from the eyeball is carried out through the vortex (whirlpool) veins, anterior ciliary veins and the central retinal vein. Vorticose veins collect blood from the uveal tract and leave the eyeball, obliquely piercing the sclera near the equator of the eye. The anterior ciliary veins and the central retinal vein drain blood from the basins of the arteries of the same name.

Innervation

The eyeball has sensitive, sympathetic and parasympathetic innervation.

Sensory innervation is provided by the ophthalmic nerve (I branch of the trigeminal nerve), which gives off 3 branches in the orbital cavity:

Lacrimal and supraorbital nerves, which are not related to the innervation of the eyeball;

The nasociliary nerve gives off 3-4 long ciliary nerves, which pass directly into the eyeball, and also takes part in the formation of the ciliary ganglion.

Ciliary nodelocated 7-10 mm from the posterior pole of the eyeball and adjacent to the optic nerve. The ciliary ganglion has three roots:

Sensitive (from the nasociliary nerve);

Parasympathetic (fibers go along with the oculomotor nerve);

Sympathetic (from fibers of the cervical sympathetic plexus). 4-6 short lines extend from the ciliary ganglion to the eyeball

ciliary nerves. They are joined by sympathetic fibers going to the pupillary dilator (they do not enter the ciliary ganglion). Thus, the short ciliary nerves are mixed, in contrast to the long ciliary nerves, which carry only sensory fibers.

The short and long ciliary nerves approach the posterior pole of the eye, pierce the sclera and run in the suprachoroidal space to the ciliary body. Here they give off sensory branches to the iris, cornea and ciliary body. The unity of innervation of these parts of the eye determines the formation of a single symptom complex - corneal syndrome (lacrimation, photophobia and blepharospasm) when any of them is damaged. Sympathetic and parasympathetic branches also extend from the long ciliary nerves to the muscles of the pupil and ciliary body.

Visual pathways

Visual pathwaysconsist of optic nerves, optic chiasm, optic tracts, as well as subcortical and cortical visual centers (Fig. 2.5).

Optic nerve (n. opticus, II pair of cranial nerves) is formed from the axons of ganglion neurons of the retina. In the fundus of the eye, the optic disc is only 1.5 mm in diameter and causes a physiological scotoma - a blind spot. Leaving the eyeball, the optic nerve receives the meninges and exits the orbit into the cranial cavity through the optic nerve canal.

Optic chiasm (chiasm) is formed at the intersection of the inner halves of the optic nerves. In this case, visual tracts are formed, which contain fibers from the outer parts of the retina of the same eye and fibers coming from the inner half of the retina of the opposite eye.

Subcortical visual centers located in the external geniculate bodies, where the axons of ganglion cells end. Fibers

Rice. 2.5.Diagram of the structure of the visual pathways, optic nerve and retina

the central neuron through the posterior thigh of the internal capsule and the Graziole bundle go to the cells of the cortex of the occipital lobe in the area of ​​the calcarine sulcus (cortical part of the visual analyzer).

AUXILIARY DEVICE OF THE EYE

The auxiliary apparatus of the eye includes the extraocular muscles, lacrimal organs (Fig. 2.6), as well as the eyelids and conjunctiva.

Rice. 2.6.The structure of the lacrimal organs and muscular apparatus of the eyeball

Oculomotor muscles

The extraocular muscles provide mobility to the eyeball. There are six of them: four straight and two oblique.

The rectus muscles (superior, inferior, external and internal) begin from the tendon ring of Zinn, located at the apex of the orbit around the optic nerve, and are attached to the sclera 5-8 mm from the limbus.

The superior oblique muscle starts from the periosteum of the orbit above and inward from the optic foramen, goes anteriorly, spreads over the block and, going somewhat posteriorly and downward, attaches to the sclera in the upper-outer quadrant 16 mm from the limbus.

The inferior oblique muscle originates from the medial wall of the orbit behind the inferior orbital fissure and attaches to the sclera in the inferior outer quadrant, 16 mm from the limbus.

The external rectus muscle, which abducts the eye outward, is innervated by the abducens nerve (VI pair of cranial nerves). The superior oblique muscle, the tendon of which is thrown over the block, is the trochlear nerve (IV pair of cranial nerves). The superior, internal and inferior rectus muscles, as well as the inferior oblique muscles, are innervated by the oculomotor nerve (III pair of cranial nerves). The blood supply to the extraocular muscles is carried out by the muscular branches of the ophthalmic artery.

Action of the extraocular muscles: the internal and external rectus muscles rotate the eyeball in a horizontal direction to the sides of the same name. The upper and lower straight lines are in the vertical direction to the sides of the same name and inward. The superior and inferior oblique muscles turn the eye in the direction opposite to the name of the muscle (i.e., superior - downward, and inferior - upward), and outward. The coordinated actions of six pairs of extraocular muscles provide binocular vision. In case of dysfunction of the muscles (for example, with paresis or paralysis of one of them), double vision occurs or the visual function of one of the eyes is suppressed.

Eyelids

Eyelids- movable skin-muscular folds covering the eyeball from the outside. They protect the eye from damage, excess light, and blinking helps to evenly cover the tear film

cornea and conjunctiva, protecting them from drying out. The eyelids consist of two layers: anterior - musculocutaneous and posterior - mucocartilaginous.

Cartilages of the eyelids- dense semilunar fibrous plates that give shape to the eyelids are connected to each other at the inner and outer corners of the eye by tendon adhesions. On the free edge of the eyelid, two ribs are distinguished - anterior and posterior. The space between them is called intermarginal, its width is approximately 2 mm. The ducts of the meibomian glands, located in the thickness of the cartilage, open into this space. At the front edge of the eyelids there are eyelashes, at the roots of which are the sebaceous glands of Zeiss and modified sweat glands of Moll. At the medial canthus, on the posterior edge of the eyelids, there are lacrimal puncta.

Skin of the eyelidsvery thin, subcutaneous tissue is loose and does not contain adipose tissue. This explains the easy occurrence of eyelid edema in various local diseases and systemic pathologies (cardiovascular, renal, etc.). When the bones of the orbit, which form the walls of the paranasal sinuses, are fractured, air can get under the skin of the eyelids with the development of emphysema.

Eyelid muscles.The orbicularis oculi muscle is located in the tissues of the eyelids. When it contracts, the eyelids close. The muscle is innervated by the facial nerve, when damaged, lagophthalmos (non-closure of the palpebral fissure) and ectropion of the lower eyelid develop. In the thickness of the upper eyelid there is also a muscle that lifts the upper eyelid. It begins at the apex of the orbit and in three portions is woven into the skin of the eyelid, its cartilage and conjunctiva. The middle part of the muscle is innervated by fibers from the cervical part of the sympathetic trunk. Therefore, when sympathetic innervation is disrupted, partial ptosis occurs (one of the manifestations of Horner's syndrome). The remaining parts of the levator palpebrae superioris muscle receive innervation from the oculomotor nerve.

Blood supply to the eyelids carried out by branches of the ophthalmic artery. The eyelids have very good vascularization, due to which their tissues have a high reparative capacity. Lymphatic drainage from the upper eyelid is carried out into the pre-auricular lymph nodes, and from the lower - into the submandibular ones. Sensitive innervation of the eyelids is provided by the I and II branches of the trigeminal nerve.

Conjunctiva

ConjunctivaIt is a thin transparent membrane covered with multilayered epithelium. The conjunctiva of the eyeball (covers its anterior surface with the exception of the cornea), the conjunctiva of the transitional folds and the conjunctiva of the eyelids (covers its posterior surface) are distinguished.

Subepithelial tissue in the area of ​​transitional folds contains a significant amount of adenoid elements and lymphoid cells that form follicles. Other parts of the conjunctiva normally do not have follicles. In the conjunctiva of the superior transitional fold, the accessory lacrimal glands of Krause are located and the ducts of the main lacrimal gland open. The stratified columnar epithelium of the conjunctiva of the eyelids secretes mucin, which, as part of the tear film, covers the cornea and conjunctiva.

The blood supply to the conjunctiva comes from the system of the anterior ciliary arteries and arterial vessels of the eyelids. Lymphatic drainage from the conjunctiva is carried out to the preauricular and submandibular lymph nodes. Sensitive innervation of the conjunctiva is provided by the I and II branches of the trigeminal nerve.

Lacrimal organs

The lacrimal organs include the tear-producing apparatus and lacrimal ducts.

Tear-producing apparatus (Fig. 2.7). The main lacrimal gland is located in the lacrimal fossa in the superior outer part of the orbit. The ducts (about 10) of the main lacrimal gland and many small accessory lacrimal glands of Krause and Wolfring exit into the upper conjunctival fornix. Under normal conditions, the function of the accessory lacrimal glands is sufficient to moisturize the eyeball. The lacrimal gland (main) begins to function under adverse external influences and certain emotional states, which is manifested by lacrimation. The blood supply to the lacrimal gland is carried out from the lacrimal artery, the outflow of blood occurs into the veins of the orbit. Lymphatic vessels from the lacrimal gland go to the pre-auricular lymph nodes. The lacrimal gland is innervated by the first branch of the trigeminal nerve, as well as by sympathetic nerve fibers from the superior cervical sympathetic ganglion.

Lacrimal ducts. Due to the blinking movements of the eyelids, the tear fluid entering the conjunctival fornix is ​​evenly distributed over the surface of the eyeball. The tear then collects in the narrow space between the lower eyelid and the eyeball - the tear stream, from where it goes to the tear lake in the medial corner of the eye. The upper and lower lacrimal openings, located on the medial part of the free edges of the eyelids, are immersed in the lacrimal lake. From the lacrimal openings, tears enter the superior and inferior lacrimal canaliculi, which empty into the lacrimal sac. The lacrimal sac is located outside the orbital cavity at its internal angle in the bony fossa. Next, the tear enters the nasolacrimal duct, which opens into the lower nasal passage.

A tear. Tear fluid consists mainly of water, and also contains proteins (including immunoglobulins), lysozyme, glucose, K+, Na+ and Cl - ions and other components. The normal pH of tears averages 7.35. Tears participate in the formation of the tear film, which protects the surface of the eyeball from drying out and becoming infected. The tear film is 7-10 microns thick and consists of three layers. Superficial - layer of lipids of the secretion of the meibomian glands. It slows down the evaporation of tear fluid. The middle layer is the tear fluid itself. The inner layer contains mucin produced by goblet cells of the conjunctiva.

Rice. 2.7.Tear-producing apparatus: 1 - Wolfring glands; 2 - lacrimal gland; 3 - Krause's gland; 4 - glands of Manz; 5 - crypts of Henle; 6 - excretory flow of the meibomian gland