Myelin fibers in the fundus. Myelinated retinal nerve fibers - review. Myelinated nerve fibers

The eye is the sense organ that brings us the most satisfaction, because it allows us to comprehend the essence of nature.

Aristotle

16.1. Anomalies of optic disc development 1

Optic aplasia - a rare, very severe pathology in which the optic nerve does not form at all and visual functions are absent due to a delay in the growth of axons of the second neuron into the optic cup stalk or due to premature closure of the germinal fissure. At the same time, underdevelopment or absence of the ganglion layer of the retina is observed. Ophthalmoscopy reveals the absence of the optic disc and retinal vessels in the fundus. At the site of the disc, an atrophy zone or depression surrounded by a pigment rim is determined. The process can be one-way or two-way

Optic nerve hypoplasia- underdevelopment of the optic nerve head, caused by incomplete differentiation of retinal ganglion cells and a decrease in the number of axons of the second neuron, and the formation of mesodermal and glial elements is usually normal. Ophthalmoscopy reveals a decrease in the diameter of the disc to 1/2 - 1/3 of this value, monotonous pallor of the disc, narrow, sometimes thread-like vessels of the retina. Vision is low, rarely 0.1-0.2.

Aplasia and hypoplasia are often combined with microphthalmos, nystagne

1 Data on the structure of the optic nerve and the anatomy of the visual pathway are presented in section 3.1.5.

mom, strabismus and developmental defects of other organs.

Optic nerve colobomas-

crater-shaped depressions of a pale gray color, round or oval in shape, usually with an uneven stepped bottom. Colobomas can be localized in the center or along the edge of the disc and be combined with choroidal coloboma. With central localization of the coloboma, the vascular bundle of the disc shifts sharply and all the vessels emerge along the edge of the coloboma, usually along the lower edge. Visual functions depend on the size and location of the coloboma: if the coloboma has formed in the projection area of ​​the papillomacular bundle (inferior temporal quadrant), vision is poor; if the coloboma is small and located in the nasal half of the disc, vision is high, up to 1.0. Visual fields with small colobomas remain unchanged, but with large ones, corresponding defects are revealed.

Dimples of the optic nerve They are small in diameter, but significant in depth formations (up to 4-5 mm) of a dark gray color, clearly visible during biomicroscopy. With slit lighting, a beam of light, passing over the dimple, “dives” into this depression, making a beak-like bend. The mechanism of dimple formation is as follows. Normally, the retina breaks off at the edge of the disc and does not penetrate deep into the tissue of the optic nerve; with this pathology, a segment of the retina is embedded in the optic nerve and at this place

a dimple is formed. In other words, at the bottom of the dimple there is a rudiment of the retina. The anomaly may not have an effect on visual function and may be an incidental finding during examination of the patient. However, when the dimple is localized in the temporal half of the disc, the development of central serous chorioretinopathy and secondary degenerative changes in the macula with a significant decrease in vision is possible. Central serous chorioretinopathy can appear in adolescence or adulthood. The anomaly is one-sided.

Inclined discs. This pathology is caused by an oblique course of the scleral canal of the optic nerve. With ophthalmoscopy, the optic nerve has an elongated oval shape, and on the temporal side a scleral cone, reminiscent of a myopic one, is visible, and on the opposite side - a richly colored disk, standing above the level of the retina, having shaded boundaries. The entire disc tissue seems to be shifted towards the nose. The refraction of the eye is often hypermetropic with astigmatism. Visual functions with correction can be high. Differential diagnosis is carried out with neuritis and initial stagnant discs. The anomaly is in most cases bilateral.

Optic disc pigmentation. Normally, there are no pigment-containing cells in the optic disc tissue and the disc has a characteristic yellow-pink color. In pathological conditions, pigment formations are also detected in the tissue of the optic nerve. They look like pigment spots, dots, tracks, arcuate stripes. A case of diffuse pigmentation of the disc, which was painted grayish-black, is described [Tron E. Zh., 1968]. Such patients should be under medical supervision.

Myelin fibers. Myelin fibers are normally located

in the retrobulbar, namely intraorbital, part of the optic nerve, without penetrating into the eyeball. With developmental anomalies, part of the myelin fibers extends into the eye, following the course of the axons of ganglion cells. In the fundus they are identified as shiny milky-white fibers located along the edge of the disc. These fibers are usually described as "tongues of white flame"

Rice. 16.1. Disc development anomalies

optic nerve.

a - myelin fibers; b - druzy.

varying degrees of severity and density (Fig. 16.1, a).

Optic disc drusen.

Drusen are noted in one or, more often, in two eyes and are light yellow formations of a round shape, reminiscent of sago grains. They can be single and superficial, then they are easy to diagnose, but sometimes drusen are located deep in the tissue and the entire disc is stuffed with them (Fig. 16.1, b). In such cases, the disc has blurred or scalloped boundaries, is protruding, and there is no physiological excavation. The functions of the eye may not be impaired.

Double (divided) optic disc. The anomaly is extremely rare. In all the described cases, the process was one-sided. The two discs may just touch each other (“thin waist”) or almost merge (“wide waist”). Each disc has its own vascular system with abnormal variations. One disc may be close to normal in size and appearance, while the other may be significantly smaller, or both may be small (hypoplasia). The division of the optic nerve concerns not only its visible part - the disc, but also the intracranial sections. Vision is usually low (within hundredths).

Enlarged discs (megalopapilla). Congenital pathology, often bilateral. Normally, the diameter of the optic nerve head varies from 1.2 to 1.9 mm, with an average of 1.5-1.6 mm. With this pathology, an increase in the diameter of the disc to 2.2-2.5 mm is detected, regardless of the refraction of the eye. During ophthalmoscopy, a characteristic picture is observed: large discs of a rich gray-pink color prominence significantly above the level of the retina, the edges of the disc are shaded, “combed,” the surrounding retina has radial striations. The vessels seem to slide off the disc, making a characteristic bend. The arteriovenous ratio is not changed, but

Increased tortuosity of the veins is often noted. In some cases, an abnormality in the branching of blood vessels on the disc is detected - a scattered type of division, whereas normally it is dichotomous. It is based on excessive growth of glial tissue - glial hyperplasia. Perhaps this is a consequence of insufficient reverse development of the embryonic processes of formation of the optic nerve head.

Pseudostagnant discs. This pathology is a type of megalopapilla. The ophthalmoscopic picture is stable throughout the patient's life.

Pseudoneuritis. This is also a type of optic nerve gliosis, but the degree of development of glial tissue is even lower than with pseudostagnation. Unlike neuritis, there is no exudative effusion or hemorrhage. The ophthalmoscopic picture is also stable throughout life.

Anomalies in the development of optic nerve vessels. Various variants of anomalies of the arterial and venous systems of the optic nerve are described: spiral and loop-shaped course of vessels with the formation of arteriovenous and veno-venous anastomoses, entanglement of the optic nerve with vessels.

Prepapillary membranes. Translucent films form over the optic disc, sometimes associated with the remnants of the vitreous artery. The degree of membrane density may vary. With pronounced compaction, the optic disc is not clearly visible. Differential diagnosis is carried out with exudative effusion in the posterior layers of the vitreous.

16.2. Inflammation of the optic nerve

An inflammatory process in the optic nerve - neuritis - can develop both in its fibers and

in shells. According to the clinical course, there are two forms of optic neuritis - intrabulbar and retrobulbar.

16.2.1. Intrabulbar neuritis

Intrabulbar neuritis (papillitis) is inflammation of the intraocular part of the optic nerve, from the level of the retina to the cribriform plate of the sclera. This section is also called the head of the optic nerve. With ophthalmoscopy, this part of the optic nerve is accessible for examination, and the doctor can trace in detail the entire course of the inflammatory process.

Etiology. The reasons for the development of the disease are varied. The causative agents of inflammation can be:

Staphylo- and streptococci;

Pathogens of specific infections - gonorrhea, syphilis, diphtheria, brucellosis, toxoplasmosis, malaria, smallpox, typhus, etc.;

Influenza viruses, parainfluenza, herpes zoster, etc.

The inflammatory process in the optic nerve is always secondary, that is, it is a complication of a general infection or focal inflammation of an organ, therefore, if optic neuritis occurs, consultation with a therapist is always necessary. The development of the disease can lead to:

Inflammatory conditions of the eye (keratitis, iridocyclitis, choroiditis, uveopapillitis - inflammation of the vascular tract and head of the optic nerve);

Diseases of the orbit (cellulitis, periostitis) and its trauma;

Inflammatory processes in the paranasal sinuses (sinusitis, frontal sinusitis, sinusitis, etc.);

Tonsillitis and pharyngolaryngitis;

Caries;

Inflammatory diseases of the brain and its membranes (encephalitis, meningitis, arachnoiditis);

Common acute and chronic infections.

Of the latter, the most common causes of the development of optic neuritis are acute respiratory viral infection (ARVI), influenza and parainfluenza. The anamnesis of such patients is very characteristic: 5-6 days after acute respiratory viral infection or flu, accompanied by an increase in body temperature, cough, runny nose, malaise, a “spot” or “fog” appears in front of the eye and vision sharply decreases, i.e. symptoms of optic neuritis arise nerve.

Clinical picture. The onset of the disease is acute. The infection penetrates through the perivascular spaces and the vitreous body. There are total and partial damage to the optic nerve. With total damage, vision is reduced to hundredths and even blindness may occur; with partial damage, vision can be high, up to 1.0, but central and paracentral scotomas of round, oval and arch-like shapes are noted in the field of view. Dark adaptation and color perception are reduced. Indicators of the critical frequency of flicker fusion and lability of the optic nerve are low. The functions of the eye are determined by the degree of involvement of the papillomacular bundle in the inflammatory process.

Ophthalmoscopic picture: all pathological changes are concentrated in the area of ​​the optic nerve head. The disc is hyperemic, its color can blend in with the background of the retina, its tissue is edematous, the edema is exudative in nature. The boundaries of the disc are blurred, but large prominence, as with stagnant discs, is not observed. Exudate can fill the vascular funnel of the disc and imbibe the posterior

layers of the vitreous body. The fundus of the eye in these cases is not clearly visible. Banded and streak-like hemorrhages are visible on or near the disc. Arteries and veins are moderately dilated.

Fluorescein angiography shows hyperfluorescence: with total damage to the entire disc, with partial damage to the corresponding zones.

The duration of the acute period is 3-5 weeks. Then the swelling gradually subsides, the boundaries of the disc become clear, and the hemorrhages resolve. The process can result in complete recovery and restoration of visual functions, even if they were initially very low. In severe forms of neuritis, depending on the type of infection and the severity of its course, the death of nerve fibers occurs, their fragmentary disintegration and replacement with glial tissue, i.e. the process ends with atrophy of the optic nerve. The severity of atrophy varies - from minor to complete, which determines the functions of the eye. Thus, the outcome of neuritis is a range from complete recovery to absolute blindness. With optic nerve atrophy, a monotonously pale disc with clear boundaries and narrow thread-like vessels is visible in the fundus.

16.2.2. Retrobulbar neuritis

Retrobulbar neuritis is an inflammation of the optic nerve in the area from the eyeball to the chiasm.

The reasons for the development of retrobulbar neuritis are the same as intrabulbar neuritis, to which is added a descending infection in diseases of the brain and its membranes. In recent years, one of the most common causes of this form of optic neuritis has become demyelitis.

debilitating diseases of the nervous system and multiple sclerosis. Although the latter does not refer to true inflammatory processes, throughout the world ophthalmological literature, lesions of the organ of vision in this disease are described in the section devoted to retrobulbar neuritis, since the clinical manifestations of lesions of the optic nerve in multiple sclerosis are characteristic of retrobulbar neuritis.

Clinical picture. There are three forms of retrobulbar neuritis - peripheral, axial and transversal.

At peripheral form the inflammatory process begins with the optic nerve sheath and spreads through the septa to its tissue. The inflammatory process is interstitial in nature and is accompanied by the accumulation of exudative effusion in the subdural and subarachnoid spaces of the optic nerve. The main complaints of patients with peripheral neuritis are pain in the orbital area, aggravated by movements of the eyeball (mechanical pain). Central vision is not impaired, but the field of vision reveals an uneven concentric narrowing of the peripheral boundaries by 20-40 o. Function tests may be within normal limits.

At axial form(observed most often), the inflammatory process develops mainly in the axial fascicle, accompanied by a sharp decrease in central vision and the appearance of central scotomas in the field of vision. Functional tests are significantly reduced.

Transversal form- the most severe: the inflammatory process involves the entire tissue of the optic nerve. Vision decreases to hundredths and even to blindness. Inflammation may begin in the periphery or in the axial fasciculus, and then along

The septum spreads to the rest of the tissue, causing a corresponding picture of inflammation of the optic nerve. Functional tests are extremely low.

In all forms of retrobulbar neuritis in the acute period of the disease there are no changes in the fundus; only after 3-4 weeks does decoloration of the temporal half or the entire disk appear - descending partial or total atrophy of the optic nerve. The outcome of retrobulbar neuritis, as well as intrabulbar neuritis, ranges from complete recovery to complete blindness of the affected eye.

Treatment. The main direction of treatment for neuritis (intra- and retrobulbar) should be etiopathogenetic, depending on the identified cause of the disease, but in practice it is not always possible to establish it. First of all, prescribe:

Broad-spectrum antibiotics; it is undesirable to use streptomycin and other antibiotics of this group;

Sulfonamide drugs;

Antihistamines;

Local hormonal (para- and retrobulbar) therapy, in severe cases - general;

Complex antiviral therapy for viral etiology of the disease: antiviral drugs and interferonogenesis inducers; the use of corticosteroids is controversial;

Symptomatic therapy: detoxification agents (glucose, hemodez, reopolyglucin); drugs that improve redox and metabolic processes; vitamins C and group B.

In the later stages, when symptoms of optic nerve atrophy appear, antispasmodics are prescribed that act on the microcirculatory level.

culations (trental, sermion, nicergoline, nicotinic acid, xanthinol). It is advisable to carry out magnetic therapy, electrical and laser stimulation.

16.3. Toxic lesions of the optic nerve

Many toxic lesions of the optic nerve occur as retrobulbar neuritis, but the basis of the pathology is not an inflammatory process, but a dystrophic one. As a result of the toxic effect on nerve fibers, their trophism is disrupted until the breakdown of nervous tissue and its replacement with glial tissue. Such conditions can arise as a result of exogenous or endogenous intoxication.

Methyl alcohol intoxication. One of the most frequently reported causes of damage to the optic nerve is poisoning with pure methyl alcohol or its derivatives (denatured alcohol, varnishes and other liquids). The toxic dose is very individual - from inhalation of vapors to ingestion of a significant amount of a toxic substance.

In the clinical picture, the manifestations of general intoxication come to the fore: headache, nausea, vomiting, gastrointestinal disorders, coma. Sometimes after a few hours, but more often after 2-3 days, the central vision of both eyes decreases significantly. When examining a patient, first of all, pay attention to wide pupils that do not react to light. No other changes in the eyes are detected. The fundus and optic nerve head are unchanged.

The further course of the disease may be different. In some cases, the initial decrease in vision is replaced by improvement, in others there is a remitting course: periods of deterioration alternate with periods of improvement.

After 4-5 weeks, descending atrophy of varying severity develops. Decoration of the optic disc appears. Morphological examination reveals changes in the layer of retinal ganglion cells and the optic nerve, especially pronounced in the intracanalicular zone.

When providing assistance to the victim, first of all, you need to try to remove the poison from the body (gastric lavage, saline laxative) and introduce an antidote - ethyl alcohol. If the patient is in a coma, then a 10% solution of ethyl alcohol is administered intravenously at the rate of 1 g per 1 kg of body weight, on average 700-800 ml for a body weight of 70-80 kg. Orally - 50-80 ml of alcohol (vodka) every 5 hours (for 2 days). Hemodialysis, infusion therapy (administration of 4% sodium bicarbonate solution), and diuretics are indicated. On the 1st day, the introduction of methyl alcohol oxidizing agents (glucose, oxygen, vitamins) is not advisable.

Alcohol and tobacco intoxication. Toxic lesions of the optic nerve develop with alcohol abuse and smoking. The disease occurs as bilateral chronic retrobulbar neuritis. Its development is based not only on the direct toxic effects of alcohol and nicotine, but also on the occurrence of endogenous vitamin B deficiency: due to damage to the mucous membrane of the gastrointestinal tract and liver, B vitamins are not absorbed.

The disease begins gradually, unnoticeably. Vision deteriorates gradually; patients consult a doctor when vision is already reduced by several tenths. Blindness usually does not occur, vision remains within 0.1-0.2. The field of view reveals a central scotoma and an enlarged blind spot. Gradually expanding, they merge, forming a characteristic centracecal

no scotoma. A characteristic complaint of patients is decreased vision in bright light: at dusk and in low light they see better than during the day, which is explained by damage to the axial fascicle and greater preservation of peripheral fibers coming from ganglion cells located on the periphery of the retina. At the onset of the disease, no changes are detected in the fundus; later, descending atrophy of the optic nerve develops, and pronounced decoloration of the temporal half, and then the entire disc, occurs. A morphological study reveals foci of demyelination and fragmented disintegration of fibers in areas corresponding to the papillomacular bundle of the optic nerve (especially in the intracanalicular region), chiasm and optic tract. Subsequently, the dead fibers of the nervous tissue are replaced by glial tissue.

During treatment, first of all, it is necessary to stop drinking alcohol and smoking; 2-3 times a year, courses of treatment are carried out using B vitamins (parenterally), drugs that improve redox processes, antioxidants and other symptomatic agents.

Toxic lesions of the optic nerve are also observed in case of poisoning with lead, quinine, carbon disulfide and overdose or individual intolerance to cardiac glycosides and sulfonamide drugs.

16.4. Ischemic neuropathy

The disease is based on an acute disturbance of arterial circulation in the vascular system supplying the optic nerve. The following three factors play a major role in the development of this pathology: disturbance of general hemodynamics,

Rice. 16.2.Anterior ischemic neuropathy.

local changes in the wall of blood vessels, coagulation and lipoprotein changes in the blood.

General hemodynamic disorders most often caused by hypertension, hypotension, atherosclerosis, diabetes, stressful situations and heavy bleeding, atheromatosis of the carotid arteries, occlusive diseases

Rice. 16.3.Wedge-shaped loss of visual field in ischemic neuropathy.

diseases of the brachiocephalic arteries, blood diseases, and the development of giant cell arteritis.

Local factors. Currently, great importance is attached to local local factors causing the formation of blood clots. Among them are changes in the endothelium of the vessel wall, the presence of atheromatous plaques and areas of stenosis with the formation of turbulence in the blood flow. The presented factors determine pathogenetically oriented therapy for this serious disease.

There are two forms of ischemic neuropathy - anterior and posterior. They can manifest themselves in the form of partial (limited) or complete (total) damage.

Anterior ischemic neuropathy- acute circulatory disturbance in the intrabulbar part of the optic nerve (Fig. 16.2).

With total damage to the optic nerve, vision is reduced to hundredths and even blindness; with partial damage, it remains high, but characteristic wedge-shaped scotomas are noted, and the apex of the wedge is always facing the point of fixation.

Rice. 16.4.Inferior hemianopsia in ischemic neuropathy.

tions of the gaze (Fig. 16.3). Wedge-shaped prolapses are explained by the sectoral nature of the blood supply to the optic nerve (see Fig. 3.9). Wedge-shaped defects, merging, cause quadrant or half loss in the field of view (Fig. 16.4). Visual field defects are most often localized in the lower half. Vision decreases over several minutes or hours. Usually, patients accurately indicate the day and hour when their vision sharply decreased. Sometimes there may be warning signs in the form of headache or transient blindness, but more often the disease develops without warning. Ophthalmoscopy reveals a pale, swollen optic disc. The vessels of the retina, primarily the veins, change secondaryly. They are wide, dark, convoluted. There may be hemorrhages on the disc and in the parapapillary zone.

The duration of the acute period of the disease is 4-5 weeks. Then the swelling gradually decreases, the hemorrhages resolve and optic nerve atrophy of varying severity appears. Visual field defects persist, although they may be significantly reduced.

Posterior ischemic neuropathy. Acute ischemic disorders develop along the optic nerve behind the eyeball - in the intraorbital region. These are posterior manifestations of ischemic neuropathy. The pathogenesis and clinical course of the disease are identical to those of anterior ischemic neuropathy, but in the acute period there are no changes in the fundus. The optic disc is a natural color with clear boundaries. Only after 4-5 weeks does decolorization of the disc appear and partial or complete atrophy begins to develop. With total damage to the optic nerve, central vision can be reduced to hundredths or to blindness, as with anterior ischemic neuropathy, with frequent

Typically, visual acuity may remain high, but characteristic wedge-shaped loss is detected in the visual field, more often in the lower or inferior nasal regions. Diagnosis in the early stage is more difficult than with ischemia of the optic nerve head. Differential diagnosis is carried out with retrobulbar neuritis, space-occupying formations of the orbit and the central nervous system.

In 1/3 of patients with ischemic neuropathy, the second eye is affected, on average after 1-3 years, but this interval can range from several days to 10-15 years.

Treatment ischemic neuropathy should be complex, pathogenetically determined, taking into account the general vascular pathology of the patient. First of all, it is intended to use:

Antispasmodics (sermion, nicergoline, trental, xanthinol, nicotinic acid, etc.);

Thrombolytic drugs - plasmin (fibrinolysin) and its activators (urokinase, hemase, cavikinase);

Anticoagulants;

Symptomatic remedies;

B vitamins.

Magnetic therapy, electrical and laser stimulation of the optic nerve are also performed.

Patients who have suffered ischemic neuropathy of one eye should be under clinical supervision and should receive appropriate preventive therapy.

16.5. Congestive optic disc

Congestive optic disc is a non-inflammatory swelling that is a sign of increased intracranial pressure.

There are quite a lot of processes that lead to increased intracranial pressure. The first place among them is occupied by intracranial tumors: they are the cause of congestive optic discs in 2/3 of cases. Other, less significant, causes of increased intracranial pressure, and consequently the development of congestive optic discs, include traumatic brain injury, post-traumatic subdural hematoma, inflammatory damage to the brain and its membranes, space-occupying formations of a non-tumor nature, damage to the blood vessels and sinuses of the brain , hydrocephalus, intracranial hypertension of unknown origin, spinal cord tumor. The severity of congestive optic discs reflects the degree of increase in intracranial pressure, but does not depend on the size of the space-occupying formation in the cranial cavity. The rate of development of a congestive disc is largely determined by the localization of the tumor in relation to the cerebrospinal fluid system of the brain and venous collectors, in particular to the sinuses of the brain: the closer the tumor is located to the cerebrospinal fluid outflow pathways and sinuses, the faster the congestive optic disc develops.

Clinically, a stagnant disc is manifested by its edema, which causes blurred patterns and boundaries of the disc, as well as hyperemia of its tissue. Typically, the process is bilateral, but in rare cases, a congestive disc may develop in only one eye. Sometimes a unilateral congestive optic disc is combined with disc atrophy and poor visual function in the other eye (Foster-Kennedy sign).

Swelling occurs first along the lower border of the disc, then along the upper, then swells successively

Rice. 16.5. Congestive optic disc.

nasal and temporal halves of the disc. There are the initial stage of development of a stagnant disc, the stage of maximum edema and the stage of reverse development of edema.

As the edema increases, the optic disc begins to protrude into the vitreous, and the edema spreads to the surrounding peripapillary retina. The disc increases in size (Fig. 16.5), and the blind spot expands, which is revealed by examining the visual field.

Visual functions can remain normal for a fairly long period of time, which is a characteristic symptom of congestive optic disc and an important differential diagnostic sign. Such patients are referred to an ophthalmologist by therapists and neurologists for fundus examination due to complaints of headache.

Another symptom of a congestive disc is a sudden, short-term sharp deterioration in vision, even to the point of blindness. This symptom is associated with a transient spasm of the arteries supplying the optic nerve (see Fig. 3.9). The frequency of such

attacks depend on several factors, including the severity of disc swelling, and can amount to several attacks within 1 hour.

As the congestive disc develops, the caliber of the retinal veins increases, indicating difficulty in venous outflow. In certain cases, hemorrhages occur, the typical localization of which is the disc area and the surrounding retina. Hemorrhages may appear with severe disc swelling and indicate a significant impairment of venous outflow. However, hemorrhages are also possible with initial or mildly expressed swelling. The reason for their development in such cases may be the rapid, sometimes lightning-fast development of intracranial hypertension, for example, with rupture of an arterial aneurysm and subarachnoid hemorrhage, as well as with a malignant tumor and toxic effects on the vascular wall.

In the stage of developed edema, in addition to the symptoms described above, cotton wool-like whitish lesions and small hemorrhages in the paramacular area may appear against the background of edematous tissue, which can cause a decrease in visual acuity.

A pronounced decrease in visual acuity is observed in the case of the development of an atrophic process in the optic nerve and the transition of the congestive optic disc to secondary (post-congestive) atrophy of the optic nerve, in which the ophthalmoscopic picture is characterized by a pale optic disc with an unclear pattern (Fig. 16.6) and borders, without edema or with traces of swelling. The veins retain their plethora and tortuosity, the arteries are narrowed. As a rule, hemorrhages and whitish lesions no longer occur at this stage of the development of the process. Like any at-

Rice. 16.6. Secondary (post-congestive) optic nerve atrophy.

rophic process, secondary atrophy of the optic nerve is accompanied by loss of visual functions. In addition to decreased visual acuity, defects in the visual field of various types are detected, which can be caused directly by the intracranial lesion, but more often begin in the inferior nasal quadrant.

Since congestive optic disc is a sign of intracranial hypertension, its timely recognition and differential diagnosis with other similar processes in the eye are very important. First of all, it is necessary to distinguish between true papilledema and pseudocongestive disc, in which the ophthalmoscopic picture resembles that of congestive papilledema, but this pathology is caused by a congenital anomaly of the structure of the disc, the presence of disc drusen, is often combined with a refractive error and is detected in childhood . You cannot completely rely on such a symptom as the presence or absence of a venous pulse, especially in cases of abnormal

orbit of the disk. One of the main symptoms that facilitate differential diagnosis is a stable ophthalmoscopic picture during dynamic monitoring of a patient with pseudocongestive optic disc. Fluorescein angiography of the fundus also helps clarify the diagnosis.

However, in some cases it is very difficult to differentiate a congestive optic disc from diseases such as optic neuritis, incipient central retinal vein thrombosis, anterior ischemic neuropathy, and optic meningioma. With these diseases, swelling of the optic disc also occurs, but its nature is different. It is caused by pathological processes developing directly in the optic nerve and is accompanied by a decrease in visual functions of varying degrees of severity.

In some cases, due to difficulties arising in establishing a diagnosis, it is inevitable to perform a spinal cord puncture with measuring the pressure of the cerebrospinal fluid and studying its composition.

If signs of congestive optic disc are detected, the patient must be immediately referred for consultation with a neurosurgeon or neurologist. To clarify the cause of intracranial hypertension, computed tomography (CT) or magnetic resonance imaging (MRI) of the brain is performed.

16.6. Optic atrophy

Optic nerve atrophy is clinically a set of symptoms: impaired visual functions (decreased visual acuity and development

visual field defects) and pallor of the optic disc, detected by ophthalmoscopy. It is not an independent disease, but develops as a result of a pathological process in the axons of the optic nerve or in retinal ganglion cells. Optic nerve atrophy is characterized by a decrease in the diameter of the optic nerve due to a decrease in the number of axons and their demyelination.

Optic nerve atrophy can be acquired or congenital.

Acquired Optic nerve atrophy develops as a result of damage to the fibers of the optic nerve (descending atrophy) or retinal cells (ascending atrophy).

Descending atrophy is caused by processes that damage the fibers of the optic nerve at different levels of the visual pathway (orbit, optic canal, cranial cavity).

The nature of damage to the optic fibers is different: inflammation, trauma, glaucoma, toxic damage, circulatory disorders in the vessels supplying the optic nerve with blood, metabolic disorders, tumor of the optic nerve, compression of the optic fibers by a space-occupying formation in the orbital cavity or in the cranial cavity, degenerative process, myopia and etc.

Various etiological factors can lead to optic nerve atrophy with certain ophthalmoscopic features, such as glaucoma, circulatory disorders in the vessels supplying the optic nerve with blood. Nevertheless, there are characteristics common to atrophy of any nature: blanching of the optic disc and impaired visual function.

The degree of decrease in visual acuity and the nature of visual field defects depend on the process that caused the atrophy. Visual acuity can range from 0.7 to practical blindness.

Based on the ophthalmoscopic picture, primary and secondary atrophy are distinguished. Primary (simple) atrophy is characterized by blanching of the optic disc with clear boundaries. The number of small vessels on the disc is reduced (Kestenbaum's symptom). The retinal arteries are narrowed, the veins may be of normal caliber or also slightly narrowed. Optic nerve atrophy, which has developed against the background of papilledema of various natures, is characterized by the fact that even after the edema disappears, the boundaries of the disc remain unclear. This ophthalmoscopic picture corresponds to secondary (post-flux) optic nerve atrophy. The retinal arteries are narrowed, while the veins are dilated and tortuous (Fig. 16.7).

Depending on the degree of damage to the optic fibers, and therefore on the degree of decrease in visual functions and blanching of the optic nerve head, there are initial (partial) And full optic nerve atrophy.

The time during which pallor of the optic nerve head develops and its severity depend not only on the nature of the disease that led to optic nerve atrophy, but also on the distance of the source of damage from the eyeball. Thus, if blood circulation in the vessels of the optic nerve is impaired, changes in its disc occur immediately. With inflammatory or traumatic damage to the optic nerve, the first ophthalmoscopic signs of optic nerve atrophy appear several days or several weeks after the onset of the disease or from the moment of injury.

Rice. 16.7. Primary optic nerve atrophy.

At the same time, the effect of a space-occupying lesion on the optic fibers in the cranial cavity initially manifests itself only as visual disturbances, and changes in the fundus, characteristic of optic nerve atrophy, appear after many weeks and even months.

Congenital genetically determined optic atrophy is divided into autosomal dominant, accompanied by an asymmetric slow decrease in visual acuity from 0.8 to 0.1, and autosomal recessive, leading to a rapid decrease in visual acuity, often to complete blindness in early childhood.

If ophthalmoscopic signs of optic nerve atrophy are detected, a thorough general clinical examination of the patient is necessary. In order to establish the cause of the development of this process and the location of damage to the optic fibers, a CT and/or MRI of the brain and orbits is performed. When assessing the ophthalmoscopic status, special attention is paid to the study of visual acuity and the boundaries of the visual field

into white, red and green colors.

Data on the condition of the optic nerve head can be obtained using such high-precision research methods as fluorescein angiography (FA), scanning the disc using a laser (HRTII) or optical coherence tomograph (OCT).

In addition to etiologically determined treatment, symptomatic complex therapy is carried out, including vasodilator therapy, vitamins B and C, and drugs that improve tissue metabolism. If optic nerve atrophy is not caused by a tumor process, various options for stimulating therapy are indicated, including electrical, magnetic and laser stimulation of the optic nerve.

Questions for self-control

1. List the main types of anomalies in the development of the optic nerve head.

2.Name the main reasons for the development of neuritis.

3. List the main clinical manifestations of intrabulbar and retrobulbar neuritis.

4. Treatment of neuritis.

5. List the main symptoms of damage to the optic nerves due to methyl alcohol intoxication.

6. Emergency care for methyl alcohol intoxication.

7. Features of damage to the optic nerve during alcohol and tobacco intoxication.

8. Treatment of alcohol and tobacco intoxication.

9.Name the main factors in the pathogenesis of ischemic neuropathy.

10. Clinical characteristics of anterior and posterior ischemic neuropathy.

11.Name the main points of treatment of ischemic neuropathy.

12.What does the presence of congestive optic disc indicate?

13. Differential diagnosis of congestive optic disc and neuritis.

14.Where are hemorrhages localized with congestive optic disc?

15.What is the state of visual functions in the early stage of development of a congestive optic disc?

16. Main symptoms of optic nerve atrophy.

17.What are the differences in the ophthalmoscopic picture of primary and secondary atrophy?

Myelin fibers are a rare congenital anomaly in which white bundles of myelin radiate from the optic disc in different directions, like petals. Myelin fibers in combination with myopia were first described by F.

Berg (1914).

Pathogenesis. ">! " and fibers

occur if myelination continues beyond the lamina cribrosa. The most plausible explanation for this fact is the heterotopia of oligodendrocytes or glial cells in the retinal nerve fiber layer. Another hypothesis exists that myelin spreads into the retina through a congenital defect in the lamina cribrosa. B. Straatsma et al. (І978) did not find a defect in the cribriform plate during morphological studies, therefore the second version about the pathogenesis of mnelin fibers is

Yes. 13.33. Myelin fibers. Amazed.i":i.

psrishshillar region. V. "intact. Visual acuity 1.0.

seems less likely. G.S. Baarsma (1980) reported the development of myelin fibers in a 23-year-old man. This patient's fundus had been photographed 7 years earlier during an examination by an ophthalmologist for diabetes, but no myelin fibers were identified on the first examination.

Clinical manifestations. The disease is almost always one-sided. There are isolated descriptions of bilateral lesions in the literature. On ophthalmoscopy, myelin fibers resemble white “fox tails” fan-shaped from the optic disc along the vascular arcades

Rice. 13.34. Congenital pigmentation of the optic disc. The disc is of normal size and gray-brown in color. The vascular bundle is centered, the course and caliber of the vessels are not changed. The pigment extends taka® to the peripapillary area on the temporal side

(Fig. 13.32; 13.33). In 50% of patients with myslin fibers of the optic disc, axial myopia is detected, which can reach -20.0 D.

Visual functions. Visual acuity with this anomaly is 0.01-1.0. Decreased visual acuity is usually seen in patients with lesions involving the macula. In the development of amblyopia in this syndrome, along with refractive factors, the shielding effect of myelin plays an important role. Visual field defects range from blind spot enlargement to centrocecal scotomas, depending on the area of ​​the myelin tails.

Electrophysiological studies. The amplitude parameters of the ERG are within normal limits, although asymmetry of the indicators is common (the ERG amplitude of the affected eye is usually lower than that of the healthy eye). When recording a VEP to a flare, the amplitude-time parameters of the P100 component are, as a rule, normal. Sometimes a decrease in the amplitude of the P100 component is noted. When recording VEPs on reversible patterns, almost all patients showed a decrease in the amplitude and an increase in the latency of the P100 component, mainly when using stimuli of high spatial frequency.

Treatment. Treatment of patients with mislin fibers of the optic disc and retina includes optical correction of ametropia (glasses or contact lenses) and simultaneous occlusion of the healthy eye. Treatment of children with this anomaly should begin as early as possible: optimal results can be achieved when therapy is carried out in children aged 6 mss-2 years. To monitor the effectiveness of treatment and the effect of occlusion on the paired eye in children of any age, it is necessary to use VEP registration. Early optical correction and adequate occlusion of the fellow eye make it possible to achieve high acuity even in children with myelin fibers involving the macula [Mosin I.M., 2001; Summers C.G. et al., 1991; Bradford G.M. et a!., 1992; Lee M.C., Gonzalez C, 1998].

Myelinated retinal nerve fiber layer (MRNFL) is a retinal pathology that manifests itself in the myelination of retinal nerve fibers. The lesion usually appears as gray and white stripes with feathery edges that are located along the course of the nerve fibers. The incidence is approximately 1.0%.
The reason why nerve fibers become myelinated is not completely clear. Oligodendrocytes are the main supporting cells of the central nervous system and are responsible for insulating long axons with myelin. This insulation allows the active potential to be conducted faster and without interference. The process of myelination is a normal process that normally occurs in other parts of the nervous system. However, there are normally no myelin fibers in the retina. This is due to the fact that the layer of nerve fibers runs anterior to the photoreceptor layer and must be transparent to light so as not to block its flow to the photoreceptors. Myelin is too dense and when the retinal nerve fibers myelinate, where this occurs, light does not reach the photoreceptor layer and the eye “does not see” the part of the retina that is covered with myelin. Depending on the extent of the lesion, loss of visual fields may or may not be noticeable. During normal development, the lamina cribrosa, a perforated portion of the sclera, allows retinal nerve fibers to exit the eye at the site where the optic nerve forms and prevents the migration of oligodendrocyte precursors into the growing and developing eye.
This barrier function is carried out with the help of astrocyte processes that accumulate on the lamina cribrosa. Thus, myelination of the optic nerve stops at the level of the lamina cribrosa and the retinal fibers remain unmyelinated. When this process is disrupted, these fibers become covered with myelin, which manifests itself in the form of the pathology under discussion.
A histological study of myelinated retinal nerve fibers conducted by Straatsma and colleagues revealed the presence of oligodendrocyte-like cells in the retina. Interestingly, the same study showed that lamina cribrosa appeared completely normal. This may indicate that oligodendrocyte precursors migrated into the retina before the formation of lamina cribrosa barrier function. Myelination of retinal nerve fibers may also be the result of activation of microglial cells during fetal development.
The effect of myelinated fibers on vision can be very different and depends on the location of the lesion and its size. In most cases, milinized fibers are an asymptomatic incidental finding. However, there are also large lesions that cover the macular area and lead to deficiency. In addition, myelinated fibers can cause axial myopia in children, which often worsens the problem. Sometimes myelinated fibers can cause leukocoria.
Myelinated fibers can be either an isolated lesion or accompanied by systemic and local changes. Ocular changes may include arterial or venous occlusion, vitreous hemorrhage, optic nerve hypoplasia, and neovascularization. Some systemic changes that may be associated with myelinated retinal fibers include neurofibromatosis type 1, craniofacial abnormalities, vitrioretinopathy with skeletal changes, and basal cell nevus syndrome.
In most cases, myelinated retinal fibers do not require treatment. In other cases, treatment is carried out depending on the associated problems. For example, amblyopia is treated with occlusion. The best results can be achieved when anisometropia is not pronounced and the macula is not involved. Optic dysplasia and strabismus are usually associated with a poor prognosis. Myopia, if present, should be corrected optically. If there is neovascularization, then treatment with an argon laser should be performed.
Myelinated retinal nerve fibers can be confused with other more serious conditions such as cotton-wool spots, peripapillary epiretinal membrane, retinal pigment epithelial detachment, retinal infiltrates, and even retinoblastoma.

OPHTHALMOLOGY - EURODOCTOR.ru -2005

Optic nerve in its development and structure it is a part of the brain located on the periphery. It consists of processes of the third retinal nerve cells. These processes form the optic nerve.

In the fundus you can see the intraocular part of the optic nerve - optic disc. In the disc region, the ganglion cell processes come together to form the disc and then rotate 90 degrees. The optic nerve then leaves the eyeball, passes through a bony canal in the skull, and forms a chiasm (optic chiasm) at the base of the skull.

Then the nerve is divided into three parts, which end in the subcortical vision centers, where the primary processing of visual information and the formation of pupillary reactions is carried out. From the subcortical centers of vision begins the central visual pathway (Graziole optic radiance), which ends in the cortex of the occipital lobes of the brain.

Congenital malformations of the optic nerve:

Pathogenesis. Myelin fibers occur if myelination continues beyond the lamina cribrosa. The most plausible explanation for this fact is the heterotopia of oligodendrocytes or glial cells in the retinal nerve fiber layer. Another hypothesis is that myelin spreads into the retina through a congenital defect in the lamina cribrosa. B. Straatsma et al. (I978) did not find a defect in the lamina cribrosa during morphological studies, so the second version about the pathogenesis of myelin fibers seems less likely. G.S. Baarsma (1980) reported the development of myelinated fibers in 23 -year-old man. This patient's fundus was photographed 7 years earlier during an examination by an ophthalmologist due to diabetes, but no myelin fibers were detected during the first examination.

Clinical manifestations. The disease is almost always one-sided. There are only a few descriptions of bilateral lesions in the literature. On ophthalmoscopy, myelin fibers resemble white “fox tails” fan-shaped from the optic disc along the vascular arcades (Fig. 13.32; 13.33). U 50 % patients with myelinated optic disc fibers exhibit axial myopia, which can reach -20,0 diopter

Electrophysiological studies. The amplitude parameters of the ERG are within normal limits, although asymmetry of the indicators is common (the ERG amplitude of the affected eye is usually lower than that of the healthy eye). When recording a VEP to a flare, the amplitude-time parameters of the P100 component are, as a rule, normal. Sometimes a decrease in the amplitude of the P100 component is noted. When recording VEPs for reversible patterns, almost all patients show a decrease in the amplitude and an increase in the latency of the P100 component, mainly when using stimuli of high spatial frequency.

Treatment. Treatment of patients with mislin fibers of the optic disc and retina includes optical correction of ametropia (glasses or contact lenses) and simultaneous occlusion of the healthy eye. Treatment of children with this anomaly should begin as early as possible: optimal results can be achieved when therapy is carried out in children aged 6 month- 2 years. To determine the effectiveness of treatment and the effect of occlusion on the fellow eye in young children, it is necessary to use VEP registration. Early optical correction and adequate occlusion of the fellow eye can achieve high acuity even in children with myelin fibers involving the macula.