Visual field impairment is an alarming symptom of serious diseases. Pathological changes in the visual field

Vision - the most important way to cognize and perceive the world for all people - from babies to very old people. Visual field loss is a dangerous, often incurable or partially incurable disease that can have many causes and requires regular medical care.

In ours with you modern world Vision problems have significantly lost their importance. People with problems that would previously have left them completely or partially incapacitated are now easily solved with the help of optics, surgical operations and less traumatic methods of ophthalmology.

The percentage of patients who became disabled due to loss or has dropped significantly, but there are still a lot of problems even in the most developed countries.

What is “field of view” in ophthalmology?

The field of view is what we see in front of us at a certain moment, without moving our head and concentrating on one object in space. To put it simply, our vision can be divided into 2 types - central and peripheral.

Central vision is responsible for what we intentionally or instinctively focus our attention on. It grabs central objects and helps us focus in case of danger or any other need. Example of importance central vision: A person looking for a coffee cup on the table in front of him.


Peripheral vision is everything that does not fall within the radius of central vision, but is still visible to the eye (by at least fine). If the entire surface of the retina read and transmitted information to the brain at the same speed, a person would never be able to focus on anything visually, or would achieve this through unimaginable effort.

The uniqueness of peripheral vision is that it transmits information more blurred and not as clearly as central vision. This allows us to do something, but at the same time also notice the events that occur around it (within a normal radius for a person, of course), helps to navigate in space.

An example of the action of peripheral (side) vision: a person crosses the road and notices a car coming around the corner. The visual field for all people is normally approximately the same, and their differences create diseases, of which there are quite a lot in practice, including loss of visual fields.

How to diagnose a similar problem in yourself?

If you feel that an area in your eyes is darkened, distorted, has completely fallen out, changes the color of what you see, or your overall angle of vision has narrowed, contact your doctor immediately. Other pathologies include flickering spots, a cloudy “veil” or darkening of the image.

In most cases, loss of visual fields is noticeable. The person experiences discomfort from limited opportunity see and almost always see a doctor. Therefore, there are relatively few advanced stages of diseases associated with visual field impairment compared to other branches of medicine.

There is a way to approximate self-diagnosis, but you shouldn’t rely on it completely - let it be just another argument to seek help. You definitely have brain problems, nervous system or visual organs, if you do not see your own hand, moved to the side at an angle of 85 °.

It is also possible to check for retinal problems using the Amsler grid. This simple test consists of just a sheet of paper with a square and a clear dot drawn in the center.

Set the paper aside at a distance from which you can usually read and look carefully at point 1 with your eye. If the cells around the point blur or are distorted in some other way, then the problem requires checking. Don't forget to do the same with the 2nd eye, which can also be damaged by the disease.

One more important feature are “disappearing” letters when reading - this means that your retina is not working quite correctly and does not display all the elements.

Causes of visual field loss:

• suffered a stroke;
• brain tumors;
• various inflammatory processes of the brain;
• deep sclerosis of the optic nerves.

Visual field loss is a disease that affects both central and lateral (peripheral) vision. Even with the most minor distortions, there is a chance that serious diseases of the retina, fundus of the eye, or organs not directly related to the eyes progress.

Without the help of a specialist, it is impossible to determine the causes of existing problems. The best thing you can do is see a specialist as soon as possible.

Associated diseases

After the examination, you will certainly receive an accurate diagnosis and necessary help, and some diseases you can partially determine in advance yourself:

Narrowing of visual fields

Narrowing of the visual field is a type of loss with the difference that individual parts of the picture do not fall out, but simply become smaller. The viewing radius narrows, as if reducing the active area of ​​the retina. Patients with this pathology note that the eye seems to become smaller in size. There are 2 types:

1. Concentric narrowing of the visual field - damage to the entire or almost entire eye, a more complex case. It is characteristically different in that it is often accompanied by diseases of the nervous system: neurasthenia, hysteria and other disorders.
2. Local narrowing of the visual field - only a certain area of ​​the retina becomes unusable.

A special eye test helps to identify which specific type the patient suffers from. If the patient cannot distinguish the size of different objects at a distance, then he most likely has a concentric type of narrowing. With local narrowing, doctors note that patients lose orientation in space (to varying degrees).

But the main diagnostic method is the Donders method. The patient and the ophthalmologist stand 1 m from each other, covering one eye. The doctor moves a small object from the conditional circle to the center, and if there are no deviations, then both test participants will see the object at the same time.

The most accurate result can be obtained by a computer perimeter - a device that projects an image of the patient’s visual fields onto a special spherical surface. Computer perimetry is practiced in specialized ophthalmological clinics.

Causes of narrowing of visual fields:

1. Pituitary adenoma. Benign tumor, in the presence of which the pituitary gland increases in size, due to its location, exerting significant pressure on the visual pathways.
2. Eye diseases: glaucoma, atrophy optic nerve and others.
3. Atherosclerosis. The disease itself is destructive, but, among other things, it can impair blood circulation in the optic nerve.
4. Various pathologies of the nervous system that have a destructive effect on it.
5. Hypertension. At severe attacks the field of view is temporarily narrowed.

The success of diagnosis also depends on the type of eye damage - organic or functional.

Treatment Options

It all depends on your diagnosis. Diagnosis and identification of the cause of problems with visual fields play a significant role.

If these changes are caused by a disease, then you need to go to a clinic, where you will be relieved of the disease itself, and then they will deal with the symptoms and consequences. Treatment can be medicinal, often surgical, however modern medicine can offer a lot effective methods eliminate such problems.

If the reasons for the narrowing or loss of your visual fields are diseases that are in no way related to the visual system, then be sure to deal with them first, and only then work on returning your vision to normal.

Don’t forget - first of all, you need a diagnosis from a specialist. Diseases visual system very dangerous, and even such minor changes as "spots" on the retina can be signs of very serious illnesses which lead to irreversible blindness in most cases.

The sooner you contact the clinic for help, the faster doctors will identify your problem and prescribe the necessary timely treatment.

Video

The absence of visual function in a limited area, the contours of which do not coincide with the peripheral boundaries of the visual field, is called scotoma. Such visual impairment may not be felt at all by the patient himself and may be detected during special methods research (so-called negative scotoma). In some cases, the scotoma is felt by the patient as a local shadow or spot in the field of vision (positive scotoma).

Scotomas can have almost any shape: oval, circle, arc, sector, irregular shape. Depending on the location of the area of ​​vision limitation in relation to the point of fixation, scotomas can be central, paracentral, pericentral, peripheral or sectoral.

If visual function is completely absent in the area of ​​the scotoma, such a scotoma is called absolute. If the patient only notes focal disorder clarity of perception of an object, then such a scotoma is defined as relative. It should be noted that the same patient had a scotoma on different colors can be revealed both absolute and relative.

In addition to all kinds of pathological scotomas, humans have physiological scotomas. An example of a physiological scotoma is the well-known blind spot - absolute scotoma. oval shape, determined in the temporal region of the visual field, and representing a projection of the disk (this area does not have photosensitive elements). Physiological scotomas have clearly defined sizes and localization, while an increase in the size of physiological scotomas indicates pathology. Thus, an increase in the size of the blind spot can be caused by diseases such as, hypertonic disease, papilledema.

To identify scotomas, previously specialists had to use rather labor-intensive methods of examining the visual field. Nowadays, this process has been greatly simplified by the use of automatic perimeters and central vision testers, and the examination itself takes only a few minutes.

Changing the boundaries of the field of view

Narrowing of the visual field can be global in nature (concentric narrowing) or local (narrowing of the visual field in a certain area with unchanged boundaries of the visual field throughout the rest of the area).

The degree of concentric narrowing of the visual field can be either slight or pronounced, with the formation of the so-called tube visual field. Concentric narrowing of the visual field may be due to various pathologies nervous system (neuroses, hysteria or neurasthenia), in which case the narrowing of the visual field will be functional. In practice, concentric narrowing of the visual field is most often caused by organic lesions organs of vision, such as peripheral, neuritis or optic atrophy, glaucoma, pigmentary, etc.

To establish what kind of narrowing of the patient’s field of vision the patient has, organic or functional, a study is carried out with objects different sizes, placing them at different distances. In case of functional impairment of the visual field, the size of the object and the distance to it have virtually no effect on the final result of the study. For differential diagnosis, the patient’s ability to orientate in space is also important: difficult orientation in the environment is usually caused by organic narrowing of the visual field.

Local narrowing of the visual field can be unilateral or bilateral. Bilateral narrowing of the visual field, in turn, can be symmetrical or asymmetrical. In practice, a large diagnostic value have a complete bilateral absence of half the visual field - hemiopia, or hemianopsia. Such disturbances indicate damage to the visual pathway in the area of ​​the optic chiasm (or behind it). Hemianopsia can be detected by the patient himself, but much more often such disorders are detected during visual field examination.

Hemianopia can be homonymous, when the temporal half of the visual field is lost on one side, and the nasal half of the visual field on the other, and heteronymous - when the nasal or parietal halves of the visual field are symmetrically lost on both sides. In addition, a distinction is made between complete hemianopsia (the entire half of the visual field falls out) and partial, or quadrant, hemianopsia (the border of the visual defect starts from the point of fixation).

Homonymous hemianopsia occurs when there are volumetric (hematoma, neoplasm) or inflammatory processes in the central nervous system, causing retrochiasmal damage to the visual pathway on the side opposite to the loss of the visual field. Patients may also have symmetrical hemianoptic scotomas.

Heteronymous hemianopsia can be bitemporal (the outer halves of the visual field are lost) or binasal (the inner halves of the visual field are lost). Bitemporal hemianopsia indicates damage to the visual pathway in the area of ​​the optic chiasm; it often occurs with pituitary tumors. Binasal hemianopsia occurs when the pathology affects the uncrossed fibers of the optic pathway in the area of ​​the optic chiasm. Such damage can be caused, for example, by an aneurysm of the internal carotid artery.

The most important human organs are the eyes. The ability to see the world is provided by central (formal) and peripheral (peripheral, lateral) vision. The first allows you to recognize the details and shapes of objects. Divided into near and far. Peripheral vision is a function regulated by a special part of the retina that helps with orientation. With its help, a person distinguishes objects at dusk and at night. Peripheral vision is characterized by the field of view. This is the space perceived by a fixed gaze. Loss of peripheral vision is often the first symptom serious pathologies. Deterioration in the perception of objects located on the sides is called hemianopsia. Loss of function, even while maintaining central vision, makes it clear to a person what it is like to lose the ability to navigate in space.

Disease on initial stages practically not felt due to the peculiarities of pathophysiology. Often the disorder is diagnosed during preventive medical examination causing shock to the patient. As the disease progresses, it becomes difficult for a person to read, watch TV, work at a computer, or navigate in space. The eyes begin to hurt more often, vision becomes less sharp, objects “float”.

The main causes of pathophysiological changes in peripheral vision are considered:

• mechanical damage to the retina (due to physical, sports activities, stressful situations, head injuries);
• glaucoma;
• cataract;
• stroke;
• atherosclerosis;
• vegetative-vascular dystonia;
• benign or malignant neoplasms;
• circulatory disorders;
• hypertension;
• osteochondrosis;
• diabetes;
• degenerative processes in the retina (detachment, thinning);
• vascular disorders;
• age (after 60 years).

After age 60, peripheral vision may deteriorate. This is a natural process.

Normal visual field values ​​are considered to be: 55° from the inner and inner upper sides, 90° from the outer and outer lower sides, 70° from the upper outer side, 50° from the inner lower side, 65° from the lower side. Violation of indicators indicates diseases of the brain or eyes.

A decrease in the boundaries of lateral vision to 5-10° is diagnosed as a concentric narrowing of the visual field. Without treatment, the disorder progresses to tunnel vision, a pathologically limited ability to see.

A change in a certain area of ​​the visual field is considered local loss. The disorder can be unilateral (homonymous hemianopsia) - loss of left or right zones, and bilateral (heteronymous hemiapsia) - loss of opposite regions.

There is symmetrical and asymmetrical impairment of peripheral vision. Symmetric loss of the temporal halves of the visual fields is classified as bitemporal hemianopsia, symmetric loss of the nasal halves is binasal hemianopsia.

There is a loss of only a quarter of the visual field on both sides - homonymous square hemianopsia.

Scotomas

Scotomas are periodically diagnosed - localized areas deprived of visual function. Violations vary in shape (arc, circle, oval) and location (sectoral, pericentral, central, paracentral, peripheral).

Scotomas are divided into negative and positive. In the first option, the pathology is not felt by the person and is detected during special examinations. In the second case, the disorder is described by the patient as cloudy spot or a shadow in the field of view.

With negative skontomas, a person does not feel any abnormalities in vision.

With an absolute scotoma, the ability to see in the affected area completely disappears. If the patient notes that objects become unclear, “blurry,” then the pathology is diagnosed as relative.

There is a physiological scotoma. The disorder has the appearance of an oval-shaped blind spot located in the temporal region of the visual field.

With spasm of the arteries of the brain or pinching of the nerve roots, atrial scotomas– reversible loss of local areas of the visual field. Often the disorders are accompanied by nausea, vomiting, and headaches. With closed and open eyelids, a person is disturbed by flickering along the contour, glare lasting up to half an hour.

Diagnostic methods

Examination helps to clarify hemianopsia.

The simplest method for diagnosing narrowing of the visual fields is to compare it between the physician and the patient using the Donders method. The technique is used when in serious condition person (paralyzed, bedridden patient), small child, in the absence of medical institution necessary digital devices. To perform the diagnosis, the specialist and the person being examined must, being at a distance of 1 m, turn to face each other. Everyone covers one eye. The patient looks into the doctor's open eye. And the specialist begins to slowly move his hand or a small table to the center of the field of view. The patient tells the doctor when he sees her.

Various methods are used to diagnose the cause and extent of peripheral vision impairment.

Perimetry and campimetry provide more accurate results. In the first case, the examination is performed using a device called a perimeter. The patient presses his chin against a special stand, closes one eye, and holds the bright dot in the center of the arc with the other. The object is directed from the sides to the periphery, and the person speaks of its appearance in the field of view.

Campimetry is performed using a large (2x2) screen. Its surface is illuminated. A person stands 2 m from the device model, closes one eye, and looks through the slit at the center of the dark screen with the other. The specialist moves a small square along it. The subject reports when he begins to see him. The test is performed several times in different directions.

To diagnose the type and cause of hemianopsia, the doctor may recommend performing a CT scan, carotid angiography, ultrasound of the brain and cervical spine spine, MRI, study of hemodynamics of the eye.

Treatment of the disease

For successful treatment pathological changes, it is important to correctly identify and eliminate the factor that provoked its occurrence.

During pregnancy, deterioration in lateral vision may be a sign of preeclampsia, a condition that is life-threatening for the woman and child. It is important to normalize blood pressure by promptly seeking medical help.

With VSD, visual impairment often occurs against the background of hallucinations, loss of consciousness, loss of strength, headaches, dizziness, fear, and nausea. Lifestyle correction and the help of a psychotherapist are necessary.

At malignant neoplasms in the eyes or brain, the patient will need surgical intervention, chemotherapy, radiotherapy.

Treatment depends on the underlying cause of the peripheral vision loss.

Results of injury age-related changes retinas are partially or completely corrected by surgery.

For neurological pathologies, they can be prescribed medications(in the form of injections, tablets, drops), restrictive diet (with the exception of caffeine-containing drinks), vitamin and mineral complexes.

Traditional methods of treating the disease will not help eliminate the disease. Various infusions and decoctions of herbs will only slightly alleviate a person’s condition, softening the symptoms of the disease.

There are several computer techniques that can restore or improve a patient’s vision. Using execution special exercises and tasks, hemianopsia is partially or fully compensated, which facilitates a person’s orientation in space.

The result largely depends on the physiology of the disease that caused the narrowing of visual fields, the stage of the diagnosed disorder, the age of the patient, and the characteristics of therapeutic tactics.

Exercises to develop peripheral vision

To prevent disturbances in lateral vision, it is important to active image life, control nutrition, avoid stress, get enough sleep. All these habits increase the resistive capabilities of the body. You need to stop drinking alcohol and smoking, treat diseases in a timely manner, and regularly have your eyes checked by an ophthalmologist.

Workout, proper nutrition, an active lifestyle and a lack of stress are ways to avoid problems with peripheral vision.

Train lateral vision by performing special gymnastics:

• standing near the window opening and choosing an object on the street, you must, without making movements with your pupils, try to distinguish objects located on the sides;
• A vertical line must be drawn in the center of the page of the book selected for reading. While trying to look at the strip, you should try to read the horizontal words printed in the peripheral area. This exercise perfectly develops speed reading skills;
• sit on a chair and lay out images with large symbols on the floor. It is necessary to lift them one by one, allowing them into the periphery zone. Gradually the viewing angle increases. Having mastered the exercise, a person begins training with smaller images;
• you need to select and hold a certain object in front of your eyes. Without looking away, you need to remember another object. Then add a new one. So you need to fix 7-9 objects. Exercise promotes the rapid development of peripheral vision.

Light eyelid massage thumbs hands for a minute, rotation eyeballs left and right, frequent flashing helps improve microcirculation.

Developed lateral visibility is important for representatives of many professions: drivers, seamstresses, athletes, military personnel.

Normal peripheral vision allows you to lead a fulfilling lifestyle. When the first symptoms of the disorder appear, you must consult a specialist and undergo comprehensive examination and begin treatment for the cause of the disease. Timely therapy will help avoid serious complications and deterioration in quality of life.

Oct 25, 2017 Anastasia Tabalina

Campimetry. Campimetry is a method of studying the visual field on a flat surface using special devices (campimeters). Campimetry is used only to study areas of the visual field within 30-40? from the center in order to determine the size of the blind spot, central and paracentral scotomas. For campimetry, a black matte board or screen made of black cloth measuring 1x1 or 2x2 m is used. The distance from the subject to the screen is 1 m, the illumination of the screen is 75-300 lux. White objects with a diameter of 1-5 mm are used, glued to the end of a flat black stick 50-70 cm long. For campimetry, it is necessary correct position heads (without tilting) on ​​the chin rest and the patient accurately fixes the mark in the center of the campimeter; The patient's second eye is closed. The doctor gradually moves the object along radii (starting from horizontal on the side where the blind spot is located) from the outer part of the campimeter to the center. The patient reports the disappearance of an object. A more detailed study of the corresponding area of ​​the visual field determines the boundaries of the scotoma and notes the results on a special diagram. The sizes of scotomas, as well as their distance from the fixation point, are expressed in angular degrees. Perimetry. Perimetry is a method of studying the field of view on a concave spherical surface using special devices (perimeters) shaped like an arc or hemisphere. There are kinetic perimetry (with a moving object) and static perimetry (with a stationary object of variable brightness). Currently, automatic perimeters are used to conduct static perimetry (Fig. 3.6).

Kinetic perimetry. The inexpensive Förster perimeter is widely used. This is a 180? arc, coated on the inside with black matte paint and having divisions on the outer surface - from 0? in the center up to 90? on the periphery. To determine the outer boundaries of the visual field, white objects with a diameter of 5 mm are used, and to identify scotomas, white objects with a diameter of 1 mm are used. The subject sits with his back to the window (the illumination of the perimeter arc with daylight must be at least 160 lux), places his chin and forehead on a special stand and fixes with one eye a white mark in the center of the arc. The patient's other eye is closed. The object is moved along an arc from the periphery to the center at a speed of 2 cm/s. The subject reports the appearance of the object, and the researcher notes which division of the arc the position of the object corresponds to at that time. This will be the outer boundary of the field of view for a given radius. Determination of the outer boundaries of the field of view is carried out along 8 (every 45?) or 12 (after 30?) radii. It is necessary to carry out a test object in each meridian to the center to ensure that visual functions are preserved throughout the entire visual field.

Normally, the average boundaries of the visual field for white color along 8 radii are as follows: inwards - 60?, from above inward - 55?, from above - 55?, from above outwards - 70?, from outside - 90?, from below outwards - 90?, from below - 65 ?, from bottom to inside - 50? (Fig. 3.7).

Rice. 3.7. Normal peripheral boundaries of the visual field for white and chromatic colors

Perimetry using colored objects is more informative, since changes in the color field of vision develop earlier. The boundary of the visual field for a given color is considered to be the position of the object where the subject correctly recognized its color. Usually blue, red and green colors. The color closest to the boundaries of the field of view to white is blue, followed by red, and closer to the setting point - green (Fig. 3.7).

Static perimetry, in contrast to kinetic one, also makes it possible to determine the shape and degree of the visual field defect.

Changes in field of view

Changes in visual fields occur during pathological processes in various parts of the visual analyzer. Identification of characteristic features of visual field defects allows for topical diagnostics.

Unilateral changes in visual field(only in one eye on the affected side) are caused by damage to the retina or optic nerve.

Bilateral visual field changes detected when the pathological process is localized in the chiasm and above.

There are three types of changes in the visual field:

- focal defects in the field of view (scotomas);

- narrowing of the peripheral boundaries of the visual field;

- loss of half the visual field (hemianopsia).

Scotoma is a focal defect in the visual field, not associated with its peripheral boundaries. Scotomas are classified according to the nature, intensity of the lesion, shape and location. According to the intensity of the lesion, absolute and relative scotomas are distinguished. Absolute scotoma is a defect within which visual function is completely lost. Relative scotoma is characterized by decreased perception in the area of ​​the defect.

By nature, positive, negative, and also atrial scotomas are distinguished. The patient notices positive scotomas himself in the form of a gray or dark spot. Such scotomas indicate damage to the retina and optic nerve. The patient does not feel negative scotomas; they are detected only during an objective examination and indicate damage to the overlying structures (chiasma and beyond).

According to shape and location, they are distinguished: central, paracentral, ring-shaped and peripheral scotomas (Fig. 3.8).

Rice. 3.8. Different kinds absolute scotomas: a - central absolute scotoma; b - paracentral and peripheral absolute scotomas; c - ring-shaped scotoma

Central and paracentral scotomas occur with diseases of the macular region of the retina, as well as with retrobulbar lesions of the optic nerve. Ring-shaped scotomas are a defect in the form of a more or less wide ring surrounding the central portion of the visual field. They are most characteristic of retinal pigmentary dystrophy. Peripheral scotomas are located in various places in the visual field, except for those listed above. They occur with focal changes in the retina and choroid.

Based on the morphological substrate, physiological and pathological scotomas are distinguished. Pathological scotomas appear due to damage to the structures of the visual analyzer (retina, optic nerve, etc.). Physiological scotomas are caused by structural features of the inner lining of the eye. Such scotomas include the blind spot and angioscotomas. The blind spot corresponds to the location of the optic nerve head, the area of ​​which is devoid of photoreceptors. Normally, the blind spot has the appearance of an oval, located in the temporal half of the visual field between 12? and 18?. The vertical size of the blind spot is 8-9?, horizontal - 5-6?. Typically, 1/3 of the blind spot is located above the horizontal line passing through the center of the campimeter, and 2/3 is located below this line.

Subjective visual disturbances with scotomas are different and depend mainly on the location of the defects. Very small absolute central scotomas can make it impossible to perceive small objects (for example, letters when reading), while even relatively large peripheral scotomas do little to hinder activity.

The narrowing of the peripheral boundaries of the visual field is due to defects in the visual field associated with its boundaries (Fig. 3.9). There are uniform and uneven narrowing of the visual fields.

Rice. 3.9. Types of concentric narrowing of the visual field: a) uniform concentric narrowing of the visual field; b) uneven concentric narrowing of the visual field

Uniform (concentric) narrowing characterized by more or less equal proximity of the boundaries of the visual field in all meridians to the point of fixation (Fig. 3.9 a). In severe cases, only the central area remains from the entire field of vision (pipe, or tubular vision). In this case, orientation in space becomes difficult, despite the preservation of central vision. Causes: retinal pigmentary dystrophy, optic neuritis, atrophy and other lesions of the optic nerve. Uneven narrowing field of view occurs when the boundaries of the field of view unequally approach the point of fixation (Fig. 3.9 b). For example, with glaucoma, narrowing occurs predominantly on the inside. Sectoral narrowing of the visual field is observed with obstruction of the branches of the central retinal artery, juxtapapillary chorioretinitis, some optic nerve atrophies, retinal detachment, etc.

Hemianopsia is bilateral loss of half the visual field. Hemianopsias are divided into those of the same name (homonymous) and those of different names (heteronymous). Sometimes hemianopsia is discovered by the patient himself, but more often they are detected during an objective examination. Changes in the visual fields of both eyes are the most important symptom in the topical diagnosis of brain diseases (Fig. 3.10).

Rice. 3.10. Changes in the visual field depending on the level of damage to the visual pathway: a) localization of the level of damage to the visual pathway (indicated by numbers);

b) change in the visual field according to the level of damage to the visual pathway

Homonymous hemianopsia- loss of the temporal half of the visual field in one eye and the nasal half in the other. It is caused by a retrochiasmal lesion of the optic pathway on the side opposite to the visual field defect. The nature of hemianopsia varies depending on the level of the lesion: it can be complete (with loss of the entire half of the visual field) or partial (quadrant).

Complete homonymous hemianopsia is observed when one of the visual tracts is damaged: left-sided hemianopsia (loss of the left halves of the visual fields) - when the right optic tract is damaged, right-sided - when the left visual tract is damaged.

Quadrant homonymous hemianopsia is caused by brain damage and is manifested by loss of the same quadrants of the visual fields. In case of damage to the cortical parts of the visual analyzer, the defects do not cover the central part of the visual field, i.e. projection zone macular spot. This is explained by the fact that fibers from the macular region of the retina go to both hemispheres of the brain.

Heteronymous hemianopsia characterized by loss of external or inner halves visual fields and is caused by damage to the visual pathway in the area of ​​the optic chiasm.

Bitemporal hemianopsia is loss of the outer halves of the visual fields. Develops when the pathological focus is localized in the middle part of the chiasm (often accompanies pituitary tumors).

Binasal hemianopsia is loss of the nasal halves of the visual fields. Caused by bilateral damage to uncrossed fibers of the optic tract in the area of ​​the chiasm (for example, with sclerosis or aneurysms of both internal carotid arteries).

Light perception and adaptation

Light perception is the ability of the eye to perceive light and determine varying degrees of its brightness. The rods are mainly responsible for light perception, since they are much more sensitive to light than the cones. Light perception reflects the functional state of the visual analyzer and characterizes the ability to orient in low-light conditions; breaking it is one of early symptoms many eye diseases.

When studying light perception, the ability of the retina to perceive minimal light stimulation (light perception threshold) and the ability to detect the smallest difference in brightness of light (discrimination threshold) are determined. The light perception threshold depends on the level of preliminary illumination: it is lower in the dark and increases in the light.

Adaptation- changes in the light sensitivity of the eye due to fluctuations in illumination. The ability to adapt allows the eye to protect photoreceptors from overstrain and at the same time maintain high light sensitivity. A distinction is made between light adaptation (when the light level increases) and dark adaptation (when the light level decreases). Light adaptation, especially with a sharp increase in light levels, may be accompanied by a protective reaction of closing the eyes. Light adaptation occurs most intensely during the first seconds; the threshold of light perception reaches its final values ​​by the end of the first minute. Dark adaptation occurs more slowly. In low-light conditions, visual pigments are consumed little, their gradual accumulation occurs, which increases the sensitivity of the retina to stimuli of reduced brightness. The light sensitivity of photoreceptors increases quickly within 20-30 minutes, and only reaches its maximum by 50-60 minutes.

The state of dark adaptation is determined using a special device - an adaptometer. An approximate determination of dark adaptation is carried out using the Kravkov-Purkinje table. The table is a piece of black cardboard measuring 20 x 20 cm, on which 4 squares measuring 3 x 3 cm made of blue, yellow, red and green paper are glued. The doctor turns off the lighting and presents the table to the patient at a distance of 40-50 cm. Dark adaptation is normal if the patient begins to see a yellow square after 30-40 s, and a blue square after 40-50 s. The patient's dark adaptation is reduced if he saw the yellow square after 30-40 s, and the blue square after more than 60 s or did not see it at all.

Hemeralopia is a weakening of the eye's adaptation to darkness. Hemeralopia is manifested by a sharp decrease in twilight vision, while daytime vision is usually preserved. There are symptomatic, essential and congenital hemeralopia.

Symptomatic hemeralopia accompanies various ophthalmological diseases: retinal pigmentary abiotrophy, siderosis, high myopia with pronounced changes in the fundus.

Essential hemeralopia is caused by hypovitaminosis A. Retinol serves as a substrate for the synthesis of rhodopsin, which is disrupted by exo- and endogenous deficiency of the vitamin.

Congenital hemeralopia is a genetic disease. No ophthalmoscopic changes are detected.

BINOCULAR VISION

Vision in one eye is called monocular. We speak of simultaneous vision when, when viewing an object with both eyes, there is no fusion (fusion in the cerebral cortex of visual images that appear on the retina of each eye separately) and diplopia (double vision) occurs.

This ability to merge individual images; received in each eye, in a single whole provides the so-called binocular vision. This ability to merge individual images; received in each eye, in a single whole provides the so-called binocular vision.

Binocular vision in humans is detected already in the fourth month of life and is formed by the age of two, but its development and improvement ends only at 8-10 years of age. Its external manifestation is stereoscopic (3D) vision, without which it is difficult to perform driving, flying and a number of other jobs, as well as playing many sports. The study of binocular vision is carried out using special devices. Binocular vision in humans is detected already in the fourth month of life and is formed by the age of two, but its development and improvement ends only at 8-10 years of age. Its external manifestation is stereoscopic (3D) vision, without which it is difficult to perform driving, flying and a number of other jobs, as well as playing many sports. Study binocular vision carried out using special devices.

Binocular vision is the ability to view an object with both eyes without causing diplopia. Binocular vision is formed by the age of 7-15 years. With binocular vision, visual acuity is approximately 40% higher than with monocular vision. With one eye, without turning the head, a person is able to capture about 140? space, two eyes - about 180?. But the most important thing is that binocular vision allows you to determine the relative distance of surrounding objects, that is, to carry out stereoscopic vision.

The mechanism of binocular vision. If an object is equidistant from the optical centers of both eyes, then its image is projected onto identical (corresponding) areas of the retinas. The resulting image is transmitted to one area of ​​the cerebral cortex, and the images are perceived as a single image (Fig. 3.11). If an object is further away from one eye than from the other, its images are projected onto non-identical (disparate) areas of the retinas and transmitted to different areas of the cerebral cortex; as a result, fusion does not occur and diplopia should occur. However, in the process of functional development of the visual analyzer, such double vision is perceived as normal, because in addition to information from disparate areas, the brain also receives information from the corresponding parts of the retina. In this case, the subjective sensation of diplopia does not arise (unlike simultaneous vision, in which there are no corresponding areas of the retina), and based on the differences between the images received from the two retinas, a stereoscopic analysis of space occurs.

The conditions for the formation of binocular vision are as follows:

Visual acuity of both eyes must be at least 0.3;

Correspondence between convergence and accommodation;

Coordinated movements of both eyeballs;

Iseikonia is the same size of images formed on the retinas of both eyes (for this, the refraction of both eyes should not differ by more than 2 diopters);

The presence of fusion (fusion reflex) is the ability of the brain to merge images from the corresponding areas of both retinas.

Methods for determining binocular vision. Miss test. The doctor and the patient are located opposite each other at a distance of 70-80 cm, each holding the needle (pencil) by the tip. The patient is asked to touch the tip of his needle to the tip of the doctor's needle in an upright position. First, he does this with both eyes open, then covering one eye in turn. With binocular vision, the patient easily performs the task with both eyes open and misses if one eye is closed.

Sokolov's experience (with a “hole” in the palm). With his right hand, the patient holds a sheet of paper rolled into a tube in front of his right eye, and places the edge of the palm of his left hand on the lateral surface of the end of the tube. With both eyes, the subject looks directly at some object located at a distance of 4-5 m. With binocular vision, the patient sees a “hole” in the palm, through which the same picture is visible as through the tube. With monocular vision, there is no “hole” in the palm.

The four-point test is used for more precise definition nature of vision using a four-point color device or a sign projector.

Rice. 3.11. Mechanism of binocular vision

There are several simple ways to determine binocular vision without using instruments.

The first is to press your finger on the eyeball in the eyelid area when the eye is open. In this case, double vision appears if the patient has binocular vision. This is explained by the fact that when one eye is displaced, the image of the fixed object will move to asymmetrical points of the retina.

The second method is the pencil experiment, or the so-called slip test, during which the presence or absence of bipocularity is detected using two ordinary pencils. The patient holds one pencil vertically in an outstretched arm, the doctor holds the other in the same position. The presence of binocular vision in a patient is confirmed if, with a quick movement, he hits the tip of his pencil with the tip of the doctor’s pencil.

The third method is the “hole in the palm” test. With one eye, the patient looks into the distance through a rolled-up paper tube, and in front of the other eye places his palm at the level of the end of the tube. In the presence of binocular vision, images are superimposed and the patient sees a hole in the palm, and in it there are objects visible with the second eye.

The fourth method is a test with an installation movement. To do this, the patient first fixes his gaze with both eyes on a nearby object, and then covers one eye with his palm, as if “turning off” it from the act of vision. In most cases, the eye deviates towards the nose or outwards. When the eye is opened, it usually returns to its original position, that is, it makes an adjustment movement. This indicates that the patient has binocular vision.

To more accurately determine the nature of vision (monocular, simultaneous, unstable and stable binocular) in clinical practice hardware research methods are widely used, in particular the generally accepted Belostotsky-Friedman technique using a four-point device "Color test TsT-1 (Russia). Four points are illuminated on its screen: white, red and two green. The subject looks through glasses with red glass in front of right eye and green in front of the left.Depending on what answers the patient gives, being at a distance of 5 m, you can accurately determine the presence or absence of binocular vision, as well as determine the leading (right or left) eye.

To determine stereoscopic vision, the “Fly” stereo test (with the image of a fly) from Titmus Optical (USA) is often used. To determine the magnitude of aniseikonia, a phase-separating haploscope is used. During the study, the patient is asked to combine two semicircles into a complete stepless circle, changing the size of one of the semicircles. The amount of aniseikonia present in the patient is taken as a percentage of the size of the semicircle for the right eye to the size of the semicircle for the left eye.

Hardware methods for studying stereoscopic vision are widely used in pediatric practice in the diagnosis and treatment of strabismus.

Accommodation

Accommodation is a person’s ability to clearly see objects located at different distances from the eye. It is realized due to the elasticity of the lens and the contractility of the ciliary muscle. Accommodation has its limits. Thus, with a normal, proportionate eye, a person cannot clearly see small details of objects under consideration closer than 6-7 cm from the eye. With myopia, even complete relaxation of the ciliary muscle does not allow you to clearly see objects located in the distance.

The volume of accommodation (the space between the nearest and further points of clear vision) will be largest with normal optical alignment of the eye, and smallest with high myopia; the volume of accommodation will be reduced even with high farsightedness. Accommodation weakens with age and as a result of various diseases.

As already indicated, the best vision is provided by the central fovea of ​​the macula. A straight line that conventionally connects the object in question with the fovea is called the visual line, or visual axis. If it is possible to direct both visual lines to the object in question, the eyes acquire the ability to converge, that is, change the position of the eyeballs by bringing them inward. This property is called convergence. Normally, the closer the object in question, the greater the convergence.

There is a direct relationship between accommodation and convergence: the greater the accommodation tension, the greater the convergence, and vice versa.

If the visual acuity of one eye is significantly higher than the other, the brain receives an image of the object in question only from the better-seeing eye, while the second eye can only provide peripheral vision. In this regard, the worse-seeing eye periodically switches off from the visual act, which leads to amblyopia - a decrease in visual acuity.

Thus, visual functions are closely related to each other and form a single whole, called the act of vision.

Now that you are sufficiently familiar with the structure and functions of the organ of vision, it is necessary to talk about the main eye diseases, their prevention, i.e., the prevention of diseases.

Damage to the human organ of vision does not always provide clear clinical picture which is noticeable to the patient himself. Some types of pathological changes can only be diagnosed using special texts

Since the narrowing and loss of the field of vision most often occurs gradually, a person adapts to the fact that his vision begins to decrease with the help of a lateral glance. To compensate for this deficiency, the patient can turn his head and experience virtually no negative symptoms. However, this condition may be a sign of other degenerative processes and diseases of the brain structures and central nervous system. Therefore, as soon as the first signs of pathology of loss of parts or segments of the visual field appear, it is necessary to urgently consult a doctor.

There is a functional division:

1. local or concentric narrowing along the entire perimeter of visibility;
2. the formation of scotomas - limited areas that fall out of visibility.

Both types are also divided according to the degree of severity, limitation and constancy of their presence.

Concentric pathology

With concentric narrowing, several degrees of damage are distinguished. IN initial stage There may be only a slight limitation of the visibility area. With the development of concentric pathology, the field of view may narrow to the size of the point of gaze fixation. Those. a person can only see what he is looking at at a given second. It's like looking into a tube of paper.

Reasons for this change include:

• excessive pigmentation of retinal tissue;
• inflammation of the optic nerve;
• atrophic changes in the structures of the nerve fibers of the visual apparatus;
• choreotic retinins with peripheral localization;
• progressive forms of glaucoma.

In some patients this effect visual perception may be associated with increased level excitability of the central nervous system. It may be hysterical or stressful situations which provoke the development of neurasthenia or neurosis.

At primary diagnosis It is important for a doctor to differentiate functional impairment from pathology caused by organic changes. The main difference is that during the study, different sizes of objects considered by the patient are used, and they do not affect the result in a functional disorder.

One-way and two-way locality

In the diagnosis of visual perception defects, local loss of the visual field is quite common. They can be double-sided or one-sided. The first type is much more common and is called hemianopsia. It is divided into non-heteronymous and homonymous subclasses. Their main cause is damage to the nerve fibers in the optic chiasm area. The symptoms of unilateral and bilateral localization are mild and not noticeable to the affected person.

Homonymous hemianopsia

This condition is characterized by partial simultaneous loss of vision in the temple area of ​​one eye and in the bridge of the nose in the second eye. This occurs due to retrocharismal narrowing of the visual pathway. Pathological process homonymous hemianopia is localized symmetrically to the lost area of ​​vision.

Varieties of this violation:

• partial and complete hemianopsia;
• half;
• quadrant;
• cortical;
• hemianoptic symmetrical scotoma.

The causes of this pathology may be tumor processes or hematomas after impacts and hemorrhages. Swelling also occurs in the background inflammatory processes. All these factors put pressure on the visual neural pathway and lead to its partial degradation.

Heteronymous hemianopsia

This diagnosis is established if the patient experiences symmetrical loss of fields in the lateral or internal planes simultaneously in both eyes. Pathology is divided into several types:

1. bitemporal - temporal vision zones fall out (develops with tumor growth in the pituitary gland area);
2. binasal - the patient does not see the area around the nose (may be a consequence of sclerosis nerve fiber or cerebral aneurysm).

Both conditions of heteronymous hemianopia require immediate diagnosis of the state of the brain structures. Urgently needed computed tomography in order to exclude tumor processes.

What are scotomas?

A scotoma in the practice of an ophthalmologist is the presence of a visual defect in a patient who is unable to see objects located in certain segments of the visual field. Depending on the perception of the sick person himself, scotoma can be either positive (the person admits the presence of a defect) or negative (the victim does not see any problems in his visual perception).

Areas of loss may have the outline of circles or ovals; there are arced and irregularly outlined sectors. There is also a division for complete loss or partial blurring of contours.

This pathology is also called a “blind spot”. In fact, a person cannot see anything in the area that is not visible to him due to the existing pathology.

Causes of scotomas can be hypertension, cerebral atherosclerosis, congestion in the optic disc area, and developing glaucoma.

Diagnosis of these pathologies is extremely difficult and requires long work individually with each patient. In large ophthalmological clinics There is automated equipment that allows you to detect a narrowing of the visual field in all its manifestations within 5 - 10 minutes.