Eye nerves symptoms. Reasons for the development of pathology. Structure and functions

Inflammation of the optic nerve (optic neuritis, optoencephalitis) is a serious ophthalmic pathology, a disease characterized by the development of inflammation of the optic nerve. In this case, demyelination occurs, a decrease in the fat layer in the structure nerve fibers that provide signaling to the CNS. Inflammation of the nerve of the eye is most often combined with other diseases, pathologies of a neurological nature. When diagnosing optoencephalitis, patients note a sharp decline visual function combined with strong pain symptoms which increase with eye movement.

The optic nerve consists of one billion sensitive processes (axons) of a structure such as the retina, which transmit information, signals to the brain about the perceived image through electrical impulses. The final processing of the received data takes place in the occipital region of the brain.

The membranes, as well as the space under the sheath of the optic nerve, are inextricably linked with the brain, the central nervous system. For this reason, in inflammatory diseases of the brain, intracranial pressure may increase, pathological processes will affect the optic nerve.

Inflammation of the nerve in the eye medical practice diagnosed in people aged 18 to 50 years. In older people, younger children age groups optic neuritis is extremely rare.

Depending on the localization of inflammatory processes, ophthalmic pathology is classified into retrobulbar and intrabulbar neuritis. With the retrobulbar form of inflammation, which can occur acutely, chronically, pathological processes are localized outside the eyeball. There is a lesion of the perceiving bundle of nerve fibers. At first, inflammation covers one eye, but if timely effective treatment is not prescribed, the pathology passes to the second, healthy eye. With intrabulbar optic neuritis, the inflammatory process affects the optic nerve head.

The main causes that provoked optoencephalitis are due to endo- and exofactors of a different nature. Inflammation of the optic nerve can develop against the background of chronic viral, bacteriological, colds (respiratory) infections, local diseases.

Optic neuritis is accompanied by neurological pathologies, chronic infections, contributing to the development of destructive processes in the nerve fibers responsible for the conduction of impulses. Optic neuritis is diagnosed with multiple sclerosis. Pathology can also be a characteristic harbinger of this neurological disease CNS.

The main causes of optoencephalitis:

inflammation of the membranes of the brain;
alcoholic, drug intoxication;
acute, chronic bacterial diseases(herpes, gonorrhea, brucellosis, tuberculosis, syphilis);
focal, local ascending, descending infections (sinusitis, rhinitis, tonsillitis);
non-communicable diseases (gout, erysipelas, blood pathologies);
mechanical injuries, damage to the deep structures of the eye;
difficult pregnancy;
inflammation of the inner lining of the eye
decrease in twilight vision;
organic lesions of various parts of the central nervous system;
chronic dysfunction internal organs.

Individuals with symptoms of brain damage are at risk. Ophthalmic pathology is diagnosed with inflammatory processes in the oral cavity, serious dental diseases(caries, periodontitis). The development of optic neuritis is promoted autoimmune diseases(optic neuromyelitis), prolonged use of certain medications, radiation exposure.

If treatment is not prescribed in a timely manner, inflammation quickly passes to other, more deep structures eyes, which, in turn, can become the main reason for the weakening of visual function, leading to complete blindness.

Symptoms

Symptoms, the intensity of their manifestation depends on age, general physiological state patients, immunity, localization. Symptoms diagnosed with inflammation of the nerve of the eye:

cutting pain syndrome in the orbit, aggravated by eye movement;
headaches, severe migraine;
decreased visual acuity;
change in color perception;
"blind" white spot, blurry spots in the field of view;
narrowing the angle of peripheral vision;
pupil dilation, photophobia;
change in twilight vision;
fever, chills, nausea, vomiting, loss of consciousness.

Decreased optical function of the eye, the symptoms of neuritis are aggravated after excessive physical activity, overwork, disturbances in sleep and rest, taking hot bath, baths, saunas.

Typically, inflammation early stages develops in one eye, but if treatment is neglected, after six to seven days it is possible that the inflammatory process will pass to a healthy eye.

Symptoms of inflammation of the nerve of the eye are manifested in the form of small point infiltrations, proliferation of cellular structures. Inflammation may be varying degrees gravity, spread with soft meninges on nerve fibers, affecting the trunk of the optic nerve. If the inflammation is localized in the nerve trunk, the pathological process acquires an interstitial character, which leads to the formation of edema, infiltration of surrounding tissues.

metabolic disorder in cell structures fibers that transmit nerve impulses, if treatment is not prescribed on time, will lead to their atrophy in areas of inflammation. With retrobulbar form on initial stages there is a sharp decrease in vision, appear discomfort, discomfort when moving the diseased eye.

Diagnostics

To establish an accurate diagnosis when the first symptoms appear, it is necessary to undergo an examination by an ophthalmologist. Treatment of optoencephalitis can be prescribed after a comprehensive diagnosis, determining the form, stage of the disease, the causes that provoked the development of inflammation in the optic nerve.

Patients are prescribed special tests to check color perception. AT without fail ophthalmoscopy is performed, which allows to determine changes in various structures of the eye using a directed light beam. If necessary, an additional MRI, fluorescein angiography is prescribed.

Therapeutic techniques

Treatment of optic neuritis should take place under full control doctor. The treatment regimen is prescribed to patients after a comprehensive diagnosis. With a timely appointment, effective treatment the prognosis is favorable. Pathological symptoms, optical functions of the eye will be fully restored. With a neglected form of the disease, unilateral blindness is possible.

Inflammation of the optic nerve, the treatment of this disease is carried out in a hospital. Taking into account the root cause that provoked the development of ophthalmic pathology, in addition to the main medical techniques, treatment is aimed at stopping the symptoms of minor diseases. It is important to stop the spread of the pathological process in time, eliminate the symptoms of inflammation, overcome the infection, restore metabolism in nerve fibers in all structures of the diseased eye.

Treatment of neuritis is carried out using antibiotics:

Streptomycin;
penicillin;
Gentamycin.

Steroid, non-steroidal, hormonal, anti-inflammatory drugs, immunomodulators are also used to increase the body's defenses. Antibacterial drugs may be prescribed to clear the infection. medical preparations a wide range actions.

To relieve swelling, reduce inflammatory reactions, glucocorticosteroids are prescribed. Local treatment involves the use of ointments, tablets, injections. Additionally, detoxification therapy is carried out, complex vitamin and mineral supplements are prescribed. Duration treatment course two to six weeks. Treatment, pharmacological preparations, duration complex therapy prescribed by the attending ophthalmologist.

Treatment of neuritis operational way, decompression of the optic nerve sheath, which is aimed at normalizing intracranial pressure, removing inflammatory edema, elimination of the main symptoms is prescribed in severe cases.

Timely prescribed treatment of retrobulbar, intrabulbar form of optonic neuritis guarantees full recovery optical functions of the eye. At the same time, relapses should not be ruled out.

Given the rapid progression of inflammation in the optic nerve, at the first symptoms, you should immediately contact the medical Center to an ophthalmologist for diagnosis.

Without a doubt, the main function of the eye is vision. However, for its proper functioning, the operation of the auxiliary apparatus, as well as protection from external influences, clear regulation is necessary. This regulation is provided by numerous nerves of the eye.

The nerves of the eye are usually divided into three groups: motor, secretory and sensory.

Sensory nerves are responsible for regulating metabolic processes, and also provide protection by warning of any external influences. For example, eye contact or inflammatory process inside the eye.

The task of the motor nerves is to ensure the movement of the eyeball through the coordinated tension of the motor muscles of the eye. They are responsible for the functioning of the dilator and sphincter of the pupil, regulate the width palpebral fissure. The motor muscles of the eye, in their work to ensure the depth and volume of vision, are under the control of the oculomotor, abducent and trochlear nerves. The width of the palpebral fissure is controlled by the facial nerve.

The muscles of the pupil itself are controlled by the nerve fibers of the autonomic nervous system.

The secretory fibers that are part of the facial nerve regulate the functions of the organ of vision.

Innervation of the eyeball

All the nerves involved in the functioning of the eye originate in groups nerve cells localized in the brain and nerve ganglions. A task nervous system eyes - regulation of muscle work, ensuring the sensitivity of the eyeball, the auxiliary apparatus of the eye. In addition, it regulates metabolic reactions and tone. blood vessels.

Five pairs of the 12 available cranial nerves are involved in the innervation of the eye: oculomotor, facial, trigeminal, as well as abducens and trochlear.

The oculomotor nerve originates from nerve cells in the brain and has a close connection with the nerve cells of the abducens and trochlear nerves, as well as the auditory, facial nerves. In addition, there is a connection with spinal cord, providing a coordinated reaction of the eyes, torso and head in response to auditory and visual stimuli or changes in the position of the torso.

The oculomotor nerve enters the orbit through the opening of the superior orbital fissure. His role is to raise upper eyelid, with ensuring the work of the internal, upper, lower rectus muscles, as well as the lower oblique muscle. Also, the oculomotor nerve includes branches that regulate the activity of the ciliary muscle, the work of the sphincter of the pupil.

Together with the oculomotor, 2 more nerves enter the orbit through the opening of the superior orbital fissure: trochlear and efferent. Their task is to innervate, respectively, the superior oblique and external rectus muscles.

The facial nerve includes motor nerve fibers, as well as branches that regulate the activity of the lacrimal gland. It regulates facial movements of the muscles of the face, the work of the circular muscle of the eye.

Function trigeminal nerve mixed, it regulates the work of muscles, is responsible for sensitivity and includes autonomic nerve fibers. As its name suggests, the trigeminal nerve divides into three large branches.

The first main branch of the trigeminal nerve is the ophthalmic nerve. Passing into the orbit through the opening of the superior orbital fissure, the ophthalmic nerve gives rise to three main nerves: nasociliary, frontal and lacrimal.

In the muscular funnel, the nasolacrimal nerve passes, in turn dividing into ethmoid (anterior and posterior), long ciliary, and nasal branches. He also gives the connecting branch to the ciliary node.

Lattice nerves are involved in providing sensitivity to cells in the lattice labyrinth, nasal cavity, skin of the tip of the nose and its wings.

Long ciliary nerves lie in the zone. Further, their path continues in the supravascular space in the direction of the anterior segment of the eye, where they and the short ciliary nerves extending from the ciliary ganglion form the nerve plexus of the corneal circumference and the ciliary body. This nerve plexus regulates metabolic processes and provides sensitivity to the anterior segment of the eye. Also, the long ciliary nerves include sympathetic nerve fibers that branch from nerve plexus belonging to the internal carotid artery. They regulate the activity of the pupil dilator.

The beginning of short ciliary nerves falls on the region of the ciliary ganglion, they run through the sclera, surrounding the optic nerve. Their role is to ensure the nervous regulation of the choroid. ciliary, also called ciliary, ganglion is an association of nerve cells involved in sensory (with the help of the nasociliary root), motor (through the oculomotor root), and also autonomic (due to sympathetic nerve fibers), direct innervation of the eye. The ciliary node is localized at a distance of 7 mm posterior to the apple of the eye from below the external rectus muscle, in contact with the optic nerve. At the same time, the ciliary nerves jointly regulate the activity of the pupillary sphincter and dilator, provide a special sensitivity of the cornea, iris, ciliary body. They maintain the tone of blood vessels, regulate metabolic processes. The subtrochlear nerve is considered the last branch of the nasociliary nerve, it is involved in the implementation of sensitive innervation of the skin of the root of the nose, as well as the inner corner of the eyelids, part of the eye.

Entering the orbit, the frontal nerve splits into two branches: the supraorbital nerve and the supratrochlear. These nerves provide sensitivity to the skin of the forehead and the middle zone of the upper eyelid.

The lacrimal nerve, at the entrance to the orbit, splits into two branches - the upper and lower. Wherein, upper branch responsible for nervous regulation activity of the lacrimal gland, as well as the sensitivity of the conjunctiva. At the same time, it provides innervation of the skin of the outer corner of the eye, capturing the area of the upper eyelid. lower branch unites with the zygomatic-temporal nerve - a branch of the zygomatic nerve and provides sensitivity to the skin of the cheekbone.

The second branch becomes the maxillary nerve and is divided into two main highways - infraorbital and zygomatic. They innervate the auxiliary organs of the eye: the middle of the lower eyelid, the lower half of the lacrimal sac, the upper half of the lacrimal duct, the skin of the forehead and zygomatic region.

The last, third branch, separated from the trigeminal nerve, does not participate in the innervation of the eye.

Video about the innervation of the eye

Diagnostic methods

External visual inspection- the width of the slit of the eye, the position of the upper eyelid.
Determination of pupil size, pupil reactions to light (direct and friendly).
Evaluation of eyeball range of motion - function test oculomotor muscles.
Evaluation of the sensitivity of the skin, in accordance with the innervation of their corresponding nerves.
Determination of possible pain at the exits of the trigeminal nerve.

Symptoms in diseases of the nerves of the eye

Disorders of the lacrimal gland.
up to blindness.
Change in field of view.
Paralysis or paresis of the motor muscles of the eye.
The occurrence of paralytic.

Diseases affecting the nerves of the eye

Marcus-Gunn syndrome.
Horner's syndrome.
Tumors of the optic nerve.

The optic nerve is the first link in the transmission of visual information from the eye to the cerebral cortex. The process of formation, structure, organization of impulse conduction distinguish it from other sensory nerves.

Formation

Bookmark occurs in the fifth week of pregnancy. The optic nerve, the second of twelve pairs of cranial nerves, develops from diencephalon together with, resembling the leg of an eye cup.

In fact, this is a special neuron, closely connected with the deep parts of the central nervous system.

As part of the brain, the optic nerve has no interneurons and directly delivers visual information from the eye's photoreceptors to the thalamus. The optic nerve does not have pain receptors, which changes clinical symptoms with his diseases, for example, with his inflammation.

During the development of the embryo, along with the nerve, the membranes of the brain are pulled out, which later form a special case of the nerve bundle. The structure of the cases of peripheral nerve bundles differs from the sheath of the optic nerve. They are usually formed by sheets of dense connective tissue, and the lumen of the cases is isolated from the spaces of the brain.

Beginning of the nerve and its ophthalmic part

The functions of the optic nerve include receiving a signal from the retina and carrying the impulse to the next neuron. The structure of the nerve is fully consistent with its functions. The optic nerve is formed from a large number of fibers that start from the third neuron of the retina. The long processes of the third neurons gather in one bundle in the fundus, transmit an electrical impulse from the retina further to the fibers that gather in the optic nerve.

This area is visually highlighted in the fundus and is called the optic disc.

In the area of visual disc the retina is devoid of receptive cells because the axons of the first transmitting neuron gather on top of it and block the underlying layers of cells from light. The zone has another name - a blind spot. In both eyes, the blind spots are located asymmetrically. Usually a person does not notice image defects, because the brain corrects it. You can detect a blind spot with the help of simple special tests.

The blind spot was discovered at the end of the 17th century. There is a story about a French king Louis XIV who amused himself by watching courtiers "headless". Slightly above the visual disc against the pupil at the bottom of the eye is the zone of maximum visual acuity, in which photoreceptor cells are maximally concentrated.

The optic nerve is made up of thousands of fine fibers. The structure of each fiber is similar to an axon - a long process of nerve cells. Myelin sheaths insulate each fiber and accelerate the conduction of an electrical impulse through it by 5-10 times. Functionally, the optic nerve is divided into right and left halves, along which impulses from the nasal and temporal regions retina is transmitted separately.

Numerous nerve strands pass through the outer membranes of the eye and are collected in a compact bundle. The thickness of the nerve in the orbital part is 4-4.5 mm. The length of the orbital part of the nerve in an adult is about 25-30 millimeters, and total length can range from 35 to 55 millimeters. Due to the bend in the eye socket, it does not stretch with eye movements. Loose fiber fat body eye socket fixes and additionally protects the nerve.

In the orbit, before entering the optic canal, the nerve is surrounded by the membranes of the brain - hard, arachnoid and soft. The sheaths of the nerve are tightly fused with the sclera and the shell of the eye on one side. On the opposite side, they are attached to the periosteum of the sphenoid bone at the site of a common tendon ring at the entrance to the skull. The spaces between the membranes are connected to similar spaces in the skull, due to which the inflammation can easily spread inward through the optic canal. The ophthalmic nerve, together with the artery of the same name, leaves the orbit through the optic canal, 5-6 millimeters long and about 4 millimeters in diameter.

Cross (chiasm)

The nerve, having passed through the bone canal of the sphenoid bone, passes into special education- chiasm, in which the threads are mixed and partially crossed. The length and width of the chiasma is about 10 millimeters, the thickness usually does not exceed 5 millimeters. The structure of the chiasma is very complex, it provides a unique protective mechanism for certain types of eye damage.

The role of the chiasma has long been unknown. Thanks to the experiments of V.M. Bekhterev, in late XIX century, it became clear that in the chiasm the nerve fibers partially cross. The fibers leaving the nasal part of the retina move to opposite side. The fibers of the temporal part follow further from the same side. Partial cross creates an interesting effect. If the chiasma is crossed in the anteroposterior direction, the image on both sides does not disappear.

Having passed the crossroads, the nerve bundle changes its name to "optic tract", although in fact these are the same neurons.

Path to the centers of vision

The optic tract is formed by the same neurons as the optic nerve lying outside the skull. The optic tract begins in the chiasm and ends in the subcortical visual centers of the diencephalon. Usually its length is about 50 millimeters. From the cross paths under the base temporal lobes pass to the geniculate body and thalamus. The nerve bundle transmits information from the retina of the eye of its side. If the tract is damaged after exiting the chiasm, the patient's fields of vision from the side of the nerve bundle fall out.

In the primary center of the geniculate body, from the first neuron of the chain, the impulse is transmitted to the next neuron. Another branch departs from the tract to the auxiliary subcortical centers of the thalamus. Directly in front of the geniculate body, the pupillary-sensitive and pupillary-motor nerves depart and go to the thalamus.

These fibers are responsible for closing the reflex circuits of the friendly photoreaction of the pupils, convergence (mowing) of the eyeballs and accommodation (changes in focus on objects located at different distances from the eye).

Near the subcortical nuclei of the thalamus are the centers of hearing, smell, balance, and other nuclei of the cranial and spinal nerves. The coordinated work of these nuclei provides basic behavior, such as a quick response to jerky movements. The thalamus is connected to others brain structures, participates in somatic and visceral reflexes. There is evidence that signals coming through the visual pathways from the retina affect the alternation of wakefulness and sleep, autonomic regulation of internal organs, emotional state, menstrual cycle, water-electrolyte, lipid and carbohydrate metabolism, production of growth hormone, sex hormones, menstrual cycle.

Visual stimuli from the primary visual nucleus are transmitted along the central visual pathway to the hemispheres. The highest center of vision in humans is located in the cortex of the inner surface occipital lobes, spur groove, lingual gyrus.

The higher center receives an inverted mirror image from the eye and transforms it into a normal picture of the world.

Up to 90% of information about the world around a person receives through vision. It is necessary for practical activities, communication, education, creativity. Therefore, people should know how visual apparatus how to keep your eyesight when you need to see a doctor.

Vision is one of the most significant functions human body. It is thanks to him that the brain receives the main part of the information about the world around us, and the optic nerve plays the leading role in this, through which terabytes of information pass per day, from the retina to the cerebral cortex.

The optic nerve, or nervus opticus, is the second pair cranial nerves inextricably linked to the brain and eyeball. Like any organ in the body, it is also subject to various diseases, as a result of which vision is rapidly, and most often irretrievably lost, since nerve cells die and are practically not restored.

To understand the causes of diseases and methods of treatment, it is necessary to know the structure of the optic nerve. Its average length in adults varies from 40 to 55 mm, the main part of the nerve is located inside the orbit, a bone formation in which the eye itself is located. On all sides, the nerve is surrounded by parabulbar tissue - adipose tissue.

It has 4 parts:

Intraocular.
Orbital.
tubular.
Cranial.

Optic disc

The optic nerve begins in the fundus, in the form of an optic nerve disk (OND), which is formed by processes of retinal cells, and it ends in a chiasm - a kind of "crossroads" located above the pituitary gland inside the skull. Since the optic disc is formed by a cluster of nerve cells, it protrudes slightly above the surface of the retina, which is why it is sometimes called the "papilla".

The area of the optic disc is only 2-3 mm 2 and the diameter is about 2 mm. The disk is not located strictly in the center of the retina, but is slightly shifted to the nasal side, in connection with this, a physiological scotoma is formed on the retina - a blind spot. The optic nerve is practically not protected. Sheaths near the nerve appear only when it passes through the sclera, that is, at the exit from the eyeball to the orbit. The blood supply of the optic nerve disc is carried out by small processes of the ciliary arteries and has only a segmental character. That is why, when blood circulation is disturbed in this area, a sharp and often irreversible loss of vision occurs.

Sheaths of the optic nerve

As already mentioned, the optic disc itself does not have its own membranes. Sheaths of the optic nerve appear only in the intraorbital part, at the site of its exit from the eye into the orbit.

They are represented by the following tissue formations:

Pia mater.
Arachnoid (arachnoid, or vascular) membrane.
Dura mater.

All membranes envelop the optic nerve in layers until it exits the orbit into the skull. In the future, the nerve itself, as well as the chiasma, is covered only by a soft membrane, and already inside the skull they are in a special cistern formed by the subarachnoid (vascular) membrane.

Blood supply to the optic nerve

The intraocular and orbital parts of the nerve have many vessels, but due to their small size (mainly capillaries), the blood supply remains good only under conditions of normal hemodynamics throughout the body.

ONH has no a large number of vessels of small sizes are the posterior short ciliary arteries, which only segmentally provide this important part optic nerve with blood. Already deeper structures of the optic disc supply blood central artery retina, but again, due to the low pressure gradient in it, small caliber, blood stasis, occlusion and various infectious diseases often occur.

The intraorbital part already has a better blood supply, which comes mainly from the vessels of the pia mater, as well as from the central artery of the optic nerve.

The cranial part of the optic nerve and chiasm are richly supplied with blood also due to the vessels of the soft and subarachnoid membranes, into which blood comes from the branches of the internal carotid artery.

Functions of the optic nerve

There are not very many of them, but they all play a significant role in human life.

List of main functions of the optic nerve:

transmission of information from the retina to the cerebral cortex through various intermediate structures;
quick response to various third-party stimuli (light, noise, explosion, approaching car, etc.) and as a result - operational reflex protection in the form of closing the eyes, jumping, jerking hands, etc.;
reverse transmission of impulses from the cortical and subcortical structures of the brain to the retina.

Visual path, or scheme of movement of the visual impulse

Anatomical structure visual pathway complex.

It consists of two consecutive sections:

peripheral part . It is represented by rods and cones of the retina (1 neuron), then by bipolar cells of the retina (2 neurons), and only then by long processes of cells (3 neurons). Together, these structures form the optic nerve, chiasm, and optic tract.
Central part of the visual pathway . The optic tracts terminate at the lateral geniculate body (which is the subcortical center of vision), the posterior thalamus, and the anterior quadrigemina. Further, the processes of the ganglia form visual radiation in the brain. An accumulation of short axons of these cells, called Wernicke's area, from which long fibers extend, forming sensory visual center- cortical field 17 according to Brodmann. This area of the cerebral cortex is the "head" of vision in the body.

Normal ophthalmic picture of the optic disc

When examining the fundus with the help of ophthalmoscopy, the doctor sees the following on the retina:

The optic disc is usually light pink in color, but with age, with or with atherosclerosis, blanching of the disc is observed.
Normally, there are no inclusions on the optic nerve disc. With age, small yellowish-gray disc drusen (deposits of cholesterol salts) sometimes appear.
The contours of the optic nerve disc are clear. The blurring of the contours of the disk may indicate increased intracranial pressure and other pathologies.
The optic disc normally does not have pronounced protrusions or depressions, it is almost flat. Excavations are observed in, in the late stages of glaucoma and in other diseases. Disc edema is observed with congestion both in the brain and in retrobulbar tissue.
The retina in young and healthy people is bright red in color, without various inclusions, and is attached tightly over the entire area to the choroid.
Normally, along the vessels there are no bands of bright white or yellow color as well as hemorrhages.

Symptoms of damage to the optic nerve

Diseases of the optic nerve in most cases are accompanied by the main symptoms:

Rapid and painless visual impairment.
Loss of visual fields - from minor to total cattle.
The appearance of metamorphopsia - distorted perception images, as well as misperceptions of size and color.

Diseases and pathological changes of the optic nerve

All diseases of the optic nerve are usually divided due to the occurrence of:

Vascular - anterior and posterior ischemic neuroopticopathy.
traumatic . There can be any localization, but most often the nerve is damaged in the tubular and cranial part. In case of fractures of the bones of the skull, mainly the facial part, a fracture of the process of the sphenoid bone, in which the nerve passes, often occurs. With extensive hemorrhages in the brain (accident, hemorrhagic strokes, etc.), compression of the chiasm region may occur. Any damage to the optic nerve can result in blindness.
Inflammatory diseases of the optic nerve - bulbar and retrobulbar neuritis, opto-chiasmal arachnoiditis, and papillitis. Symptoms of inflammation of the optic nerve are in many ways similar to other lesions of the optic tract - vision deteriorates quickly and painlessly, fog appears in the eyes. Against the background of the treatment of retrobulbar neuritis, a complete restoration of vision very often occurs.
Non-inflammatory diseases of the optic nerve . Frequent pathological phenomena in the practice of an ophthalmologist are represented by edema various etiologies, .
Oncological diseases . The most common tumor of the optic nerve is benign gliomas in children, which appear before the age of 10-12 years. Malignant tumors - a rare event are usually metastatic in nature.
congenital anomalies - an increase in the size of the optic disc, hypoplasia of the optic nerve in children, coloboma and others.

Research methods for diseases of the optic nerve

For all neuro-ophthalmic diseases diagnostic examinations include both general ophthalmic methods and special ones.

To common methods relate:

visometry - the classic definition of visual acuity with and without correction;
perimetry - the most revealing method of examination, allowing the doctor to determine the localization of the lesion;
ophthalmoscopy - with a lesion primary departments nerve, especially with ischemic opticopathy, pallor, disc excavation or edema, its blanching or, conversely, an injection is detected.

To special methods diagnostics include:

Magnetic resonance imaging of the brain (to a lesser extent, computed tomography and targeted radiography). Is optimal study in traumatic, inflammatory, non-inflammatory (multiple sclerosis) and oncological causes diseases (glioma of the optic nerve).
Fluorescein angiography of retinal vessels - the “gold standard” in many countries, which makes it possible to see in which area the cessation of blood circulation occurred, if anterior ischemic optic neuropathy occurred, to establish the localization of the thrombus, to determine further predictions in the restoration of vision.
HRT (Heidelberg Retinal Tomography) - a survey that shows in great detail the changes in the optic disc, which is very informative in glaucoma, diabetes dystrophies of the optic nerve.
Ultrasound of the orbit It is also widely used for lesions of the intraocular and orbital nerve, it is very informative if a child has an optic nerve glioma.

Treatment of diseases of the optic nerve

Due to the variety of causes that cause damage to the optic nerve, treatment should be carried out only after setting the exact clinical diagnosis. Most often, the treatment of such pathologies is carried out in specialized ophthalmological hospitals.

Ischemic optic neuropathy - a very serious disease that needs to be treated within the first 24 hours from the onset of the disease. More prolonged absence therapy leads to a persistent and significant decrease in vision. In this disease, a course of corticosteroids, diuretics, angioprotectors, as well as drugs aimed at eliminating the cause of the disease are prescribed.

Traumatic pathology of the optic nerve in any part of its path can lead to a serious deterioration in vision, therefore, first of all, it is necessary to eliminate compression on the nerve or chiasm, which is possible using the forced diuresis technique, as well as performing trepanation of the skull or orbit. Forecasts for such injuries are very ambiguous: vision may remain 100%, or it may be completely absent.

Retrobulbar and bulbar neuritis are most often the first sign of multiple sclerosis (up to 50% of cases). The second most common cause is an infection, both bacterial and viral (herpes virus, CMV, rubella, influenza, measles, etc.). Treatment is aimed at eliminating swelling and inflammation of the optic nerve, using large doses of corticosteroids, as well as antibacterial or antiviral drugs, depending on the etiology.

Benign neoplasms occur in 90% of children. Glioma of the optic nerve is located inside the optic canal, that is, under the membranes, and it is characterized by growth. This pathology of the optic nerve cannot be treated, and the child may go blind.

Glioma of the optic nerve gives the following symptoms:

vision decreases very early and quickly, up to blindness on the side of the lesion;
bulging develops - non-pulsating exophthalmos of the eye, the nerve of which is affected by the tumor.

Glioma of the optic nerve in most cases affects precisely the nerve fibers and much less often - the opto-chiasmatic zone. The defeat of the latter usually greatly complicates the early diagnosis of the disease, which can lead to the spread of the tumor to both eyes. For early diagnosis it is possible to use MRI or X-ray according to Reza.

Optic nerve atrophies of any origin are usually treated with courses twice a year to maintain the stability of the condition. The therapy includes medications(Cortexin, B vitamins, Mexidol, Retinalamin), and physiotherapy procedures (electrical stimulation of the optic nerve, magneto- and electrophoresis with drugs).

If changes in vision are detected in oneself or in one's relatives, especially in senile or childhood age, it is necessary to contact the attending ophthalmologist as soon as possible. Only a doctor can correctly diagnose and prescribe necessary measures. Delay in diseases of the optic nerve threatens with blindness, which can no longer be cured.

The human eye is designed in such a way that it perceives light rays emanating from objects of the surrounding world, projects them onto the retina, and then the optic nerve transports electrical impulses from the zone of light-sensitive cells of the retina to the analyzer located in the back of the brain, where the processing takes place. information.

The nervous tissue of the organs of vision is the second pair of cranial nerves, which is a segment of the optic tract located between the organ of vision and the chiasm. It is the link between the human organ of vision and its central nervous system.

Anatomy

The optic nerve is a process of light-sensitive retinal cells that gather into a single bundle in the area of the posterior hemisphere of the eye. The number of these fibers exceeds a million, and yet, as the years pass, their number decreases. Clusters of these fibers are separated from each other by the myelin layer. The localization of nerve cells emerging from different regions of the retina is differentiated by its structure. In the region of the optic nerve head (OND), the layer of nerve fibers becomes thicker and this place rises to some extent above the retina. Combined together in the region of the optic nerve head, the fibers bend perpendicularly and form that section of the optic nerve that is located inside the organ of vision.

The disc diameter varies numerically in the range from 1.75 mm to 2.00 mm and occupies an area of two to three millimeters. The length of the ONH is approaching 1 mm. The area of its projection in the field of view corresponds to the size of the blind spot (the area in which a person is not able to see anything), known to scientists since the middle of the 17th century thanks to the research of E. Marriott. The presence of a blind spot is due to the fact that there are no light-sensitive cells on the surface of the optic disc. As a rule, a person is not aware of the existence of a blind spot, since both eyes work, the fields of view of which mutually overlap, and, in addition, the brain is able to ignore this zone and independently complete a non-existent image. The optic nerve disc is a non-pulmonic nerve fiber.

It is not formed by oligodedroglia and microglia, but there are a large number of capillaries and supporting fragments. The optic disc is histologically formed from astrocytes with extended processes surrounding all bundles of nerve fibers and penetrating into them. The border between the non-fleshy and pulpy parts of the optic nerve is adjacent to the outer surface of the cribriform plate and is localized inside the eye. The optic nerve stretches from the ONH zone to the chiasm (the intersection of the optic nerve from the inside of the retinas of the right and left eyes).

The length of the optic nerve of an adult healthy individual can range from 35 to 55 mm. Moreover, the optic nerve bends S-shaped, which does not allow it to stretch at a time when the human eyeball carries out its movements in the usual amplitude. Anatomically, the optic nerve, like the human brain, consists of three layers - relatively hard, arachnoid and soft. Moreover, the areas between the layers are filled with a liquid of a certain complex composition.

How is the optic nerve trophic

Between the bundles of fibers of the optic nerve are the central retinal vessels (vein and artery). The outer layers of the nerve fibers of the optic disc carry out trophism partly from the central retinal artery, and partly from the capillaries of the peripapillary choroidal vessels. They are localized in glial septa containing astrocytes and enveloping bundles of nerves.

Most of the nutrition in the nervous tissue comes in the zone of the papillomacular bundle, here the trophism is also carried out through the ciliary vessels following from the cribriform plate.

According to the place of its localization along the entire length, the optic nerve is divided into four zones, namely:

Intraocular, passing through choroid eyes and sclera, where the central retinal artery adjoins it;
intraorbital;
Intracanal, located in the optic canal and having a length of 0.5 to 0.7 cm, moreover, in the canal the nerve is localized above the ophthalmic artery;
intracranial zone. This zone runs through the middle cranial fossa in the subarachnoid space above the diaphragm of the Turkish saddle.

The ophthalmic nerves from both eyes, as already noted, leave the region of the organ of vision, continue into cranium and form a chiasm, intersecting in the region of the Turkish saddle. In the region of the chiasm, the optic fibers coming from different eyes partially overlap. Moreover, only the nerve cells formed by the internal (close to the nose) parts of the retinas of the right and left eyes intersect. And the parts nervous tissue, starting from the parts of the retina facing outward (closer to the temples), do not intersect, but continue their movement along the original trajectory.

Behind the chiasm, the fibers of the optic nerve are already called the optic tracts. A separate optic tract consists of fibers from the outer retina on the same side and fibers from the inner retina on the opposite side.

Histology of the optic nerve

The optic nerve tissue is formed by the following cells:

afferent fibres. The cells of the optic nerve are formed from over a million afferent nerve cells originating in retinal ganglion neurocytes.
Oligodendrocytes that myelinate axons.
Microglia, immunocompetent phagocytic cells of the retina, triggering the process of apoptosis of its ganglion cells.
Astrocytes lining the area between axons and other structural units. If the nervous tissue atrophies and axons die, astrocytes take up all the available vacant space.
Surrounding membranes, consisting of the inner medulla, equipped with large quantity capillaries, the subarachnoid region and the outer layer, which differentiates into the arachnoid and hard layers.

Functional loading of the optic nerve

The main function of the optic nerve is the transmission of nerve impulses from the ganglion cells of the retina to the brain, where the visualization of the surrounding world takes place. The most complex branched group of nerve fibers captures the primary visual stimuli and transmits them by means of electromagnetic impulses to the areas of the brain responsible for the implementation of the visual function, after which it transmits the corresponding impulses and transports the finished analyzed image of the surrounding world to the visual department.

Even minor disturbances in the structure of the optic nerve can lead to extremely serious violations visual function, and violation of the integrity of the optic nerve is fraught with a complete loss of vision function. Structural disorders of the nervous tissue can lead to loss of some visual fields or the development of visual hallucinations.

How is the study of the ophthalmic nerve

The ONH can be studied in detail by a specialist ophthalmologist using methods such as:

Ophthalmoscopy, which allows to assess its pigmentation, shape, clarity of boundaries and blood supply;
Campimetry, which provides an opportunity to identify the localization in the field of view of the central scotomas and assess the size of the blind spot;
Optical coherence tomography(optical coherence tomography, OCT), which provides the ability to non-invasively obtain images of optically transparent eye media with high resolution. This, in turn, gives doctors the opportunity to get a detailed idea of the state of the optic nerve, its depth, the relative and absolute size of its excavation;
Heidelberg retinal tomography (HRT), which gives ophthalmologists a unique opportunity to track the direct result of the progression of eye diseases, in particular glaucoma, which cause irreversible and, to a certain point, imperceptible degeneration of nerve tissues, using a non-invasive method on a microscopic scale. Provides comprehensive information about the size, contours, and shape of the optic disc, the rim, the optic nerve excavation, and the retinal nerve cell layer. This procedure allows you to reliably quantify the changes that occur with the optic nerves at various pathological processes flowing in the organs of vision.

Pathological processes that can develop in the optic nerve

By using modern methods diagnostics, it is possible to timely diagnose the following birth defects ophthalmic nerve:

Change in the size of the optic nerve head (both increase and decrease);
Coloboma ONH;
Deposits of light-refracting substances (druze) in the optic disc;
Atrophy of the optic nerve;
False inflammation (neuritis) of the optic nerve tissue.

It is also possible to timely detect such acquired defects as:

Atrophy of the optic nerve of various etiologies;
True neuritis;
congestive optic disc;
Disturbances in the blood supply to the optic nerve due to deformation of the structure of blood vessels.