How to restore binocular vision with strabismus: mechanism, research, treatment of disorders. Why do you need binocular vision?

Use a device designed by the Tochmedpribor plant or a similar test projector of test marks. The operation of the device is based on the principle of dividing the fields of vision of both eyes using color filters.

The removable cover of the device has four holes with light filters arranged in the shape of a lying letter “T”: two holes for green filters, one for red and one for white. The device uses light filters of complementary colors; when placed on top of each other, they do not transmit light.
The study is carried out from a distance of 1 to 5 m. The subject is wearing glasses with a red filter in front of the right eye and with a green filter in front of the left eye.

When examining the colored holes of the device through red-green glasses, a subject with normal binocular vision sees four circles: red on the right, two green ones vertically on the left, and a middle circle, as if consisting of red (right eye) and green (left eye) colors.

• If there is a clearly defined dominant eye, the middle circle is painted in the color of the light filter placed in front of this eye.
• With monocular vision of the right eye, the subject sees through the red glass only red circles (there are two of them), with monocular vision of the left eye - only green circles (there are three of them).
• With simultaneous vision, the subject sees five circles: two red and three green.

Raster haploscopy (Bagolini test)

Raster lenses with the thinnest parallel stripes are placed in the frame in front of the right and left eyes at an angle of 45° and 135°, which ensures mutually perpendicular direction of the raster stripes, or ready-made raster glasses are used. When fixing a point light source placed at a distance of 0.5-1 cm in front of the glasses, its image is transformed into two luminous mutually perpendicular stripes. With monocular vision, the patient sees one of the stripes, with simultaneous vision, two unaligned stripes, with binocular vision, the figure of a cross.

According to the Bagolini test, binocular vision is recorded more often than according to the color test, due to the weaker (non-color) separation of the right and left visual systems.

Chermak's method of sequential visual images

They evoke successive images by illuminating the right and left eyes alternately while fixing the central point: with a bright vertical stripe (right eye), and then with a horizontal stripe (left eye) for 15-20 s (with each eye). Next, successive images are observed on a light background (screen, sheet of white paper on the wall) with light flashes (after 2-3 s) or when blinking the eyes.

By the location of the stripes of foveal visual images in the form of a “cross”, the misalignment of the vertical and horizontal stripes, or the loss of one of them, one judges, respectively, their combination (in persons with binocular vision), misalignment with the same or cross localization, suppression (suppression of one image), presence of monocular vision.

Assessment of binocular functions using a synoptophore

The device performs mechanical haploscopy using two separate movable ones (for installation at any angle of strabismus) optical systems- right and left. The set consists of three types paired test objects: for combination (for example, “chicken” and “egg”), for fusion (“cat with a tail”, “cat with ears”) and stereotest.

The synoptophore allows you to determine:

• ability for bifoveal fusion (when both images are combined at a strabismus angle);
• the presence of a zone of regional or total suppression (functional scotoma), its location and size (according to the measuring scale of the device in degrees);
• the amount of fusion reserves according to tests for fusion - positive (with convergence), negative (with divergence of paired tests), vertical, torsion;
• presence of stereo effect.

Synoptophore data allows you to determine forecast and tactics complex treatment, and also choose the type of orthoptic or diploptic treatment.

Depth Vision Assessment

A Howard-Dolman type device is used. The study is performed in natural conditions without dividing the field of view.

Three vertical poibor rods (right, left and movable middle) are placed in the frontal plane on one horizontal straight line. The subject must perceive the displacement of the middle rod as it approaches or moves away in relation to the two fixed ones. The results are recorded in linear (or angular) quantities, components for persons mature age 3-6 mm for near (from 50.0 cm) and 2-4 cm for distance (from 5.0 m), respectively.

Depth vision is well trained in a real environment: ball games (volleyball, tennis, basketball, etc.).

Stereoscopic vision assessment

• Using the flying fly test. The study is carried out using a booklet with polaroid vectograms (fly-test from Titmus). When viewing the picture through the Polaroid glasses supplied with the booklet, you get the impression of a stereoscopic effect.
  Based on the recognition of the location and degree of remoteness of tests with different levels of lateral displacement of paired drawings, the threshold is judged stereoscopic vision(from the ability to have stereoscopic sensation to 40 arc seconds), using the table in the booklet.
• Using the Lang test. The study is carried out on a Polaroid booklet using Polaroid glasses, similar to the method described above. The method allows one to estimate the threshold of stereoscopic vision in the range from 1200 to 550 arc seconds.
• On a lens stereoscope with paired pictures of Pulfrich. Paired pictures are built according to the principle of transverse disparity. The details of the drawings (large, small) make it possible to register the stereoscopic vision threshold of up to 4 arc seconds based on the correct answers of the subject.
• Screening methods. Research is carried out using test mark projectors equipped with a measuring ruler for special tests (Carl Zeiss). The test consists of two vertical lines and a round luminous spot under them. A subject with stereoscopic vision, when viewed through Polaroid glasses, distinguishes three figures located at different depths (each of the strokes is visible monocularly, the spot is visible binocularly).

Definition of phoria

Maddox test

The classic technique involves using a red Maddox “stick” from a set of lenses, as well as a Maddox “cross” with a vertical and horizontal measuring scale and a point light source in the center of the cross. The technique can be simplified if you use a point light source, a Meddox “wand” in front of one eye and a prism ophthalmic compensator OKP-1 or OKP-2 in front of the other eye.

The ophthalmic compensator is a biprism of variable strength from 0 to 25 prism diopters. At horizontal position When using the rod, the examinee sees a vertical red stripe, displaced in the presence of heterophoria from the light source outward or inward in relation to the eye in front of which the rod is placed. The strength of the biprism, which compensates for the displacement of the strip, determines the amount of esophoria (when the strip is displaced outward) or exophoria (when displaced inward).

A similar research principle can be implemented using test mark projector tests.

Graefe's test

Draw a horizontal line with a vertical arrow in the middle on a piece of paper. A prism with a strength of 6-8 prism diopters is placed in front of one eye of the subject with the base up or down. A second image of the drawing appears, shifted in height.

In the presence of heterophoria, the arrow moves to the right or left. A displacement of the same name (outward) in relation to the eye in front of which the prism is placed indicates esophoria, and a cross displacement (inward displacement) indicates exophoria. A prism or biprism, which compensates for the degree of displacement of the arrows, determines the magnitude of the phoria. Tangential markings can be applied to the horizontal line with dots corresponding to degrees or prism diopters (instead of biprism). The degree of displacement of the vertical arrows on this scale will indicate the magnitude of the phoria.

How to check the presence and nature of binocular vision at home?

Firstly, a violation of binocular vision can be suspected when, when trying to pour boiling water from a kettle into a cup, you pour it past the cup.

Secondly, a simple experiment will help test the function of binocular vision. The index finger of the left hand must be placed vertically at the top at eye level at a distance of 30-50 cm from the face. Index finger right hand you need to try to quickly hit the end of the left index finger, moving from top to bottom.

If this was done the first time, then we can hope that binocular vision is not impaired.

If a person has convergent or divergent strabismus, then, of course, there is no binocular vision.

Double vision is also a sign of impaired binocular vision, or rather simultaneous vision, although the absence of it does not indicate the presence of binocular vision. Double vision occurs in two cases.

Firstly, in the case of paralytic strabismus, caused by disturbances in the nervous system that controls the work of the extraocular muscles. Secondly, if one eye is mechanically displaced from its usual position, this happens due to neoplasms, with the development of a degenerative process in the fatty pad of the orbit near the eye, or with an artificial (intentional) displacement of the eyeball with a finger through the eyelid.

The following experiment confirms the presence of binocular vision. the subject looks at a point in the distance. One eye is slightly pressed upward with a finger through the lower eyelid. Next, observe what happens to the image. If you have full binocular vision, vertical double vision should appear at this moment. A single visual image bifurcates, and one image goes upward. After the pressure on the eye stops, a single visual image is restored again. If during the experiment no double vision is observed and nothing new happens to the image, then the nature of vision is monocular. In this case, the eye that has not been displaced works. If double vision is not observed, but during the displacement of the eye a single image is shifted, then the nature of vision is also monocular, and the eye that was displaced is working.

Let's do one more experiment (installation movement). The subject looks at some point in the distance. Let's try to cover one eye with our palm. If after this the fixed point moves, the nature of vision is monocular and with both eyes open, the one that was covered works. If the fixed point disappears, then the nature of vision with the same eye is also monocular, and the eye that was not covered does not see at all.

Binocular vision means seeing with two eyes, but an object is seen as a single object, as if with one eye. The highest degree of binocular vision is depth, relief, spatial, stereoscopic. In addition, with binocular perception of objects, visual acuity increases and the field of view expands. Binocular vision- the most complex physiological function, the highest stage of evolutionary development of the visual analyzer.

Full depth perception is possible only with two eyes. Vision with one eye - monocular - gives an idea only of the height, width, shape of an object, but does not allow one to judge the relative position of objects in space “in depth”. Simultaneous vision is characterized by the fact that in the higher visual centers, impulses from one and the other eye are perceived simultaneously, but there is no fusion into a single visual image.

In life, many objects are located in front of a person’s eyes at different distances from each other, and thus conditions constantly exist for the occurrence of diplopia. However, most people do not experience double vision. This is explained by the fact that diplopia is suppressed by our consciousness. However, such suppression of the double image of objects during vision with two eyes does not go unnoticed. On the contrary, the presence of diplopia (although not perceived by consciousness) determines binocular vision. The brain “unconsciously understands” that with cross diplopia the object lies closer to the point of fixation, and with the same one, it lies further away. If such physiological double vision did not exist, then there would be no deep vision.

Binocular vision is determined in various ways. One of the most successful and generally accepted is research using the four-point color test (Belostotsky). To get a visual representation of binocular vision in yourself, you can do Sokolov’s experiment with a “hole in the palm,” as well as experiments with knitting needles and reading with a pencil.

Sokolov’s experiment consists of having the subject look with one eye into a tube (for example, into a notebook rolled up into a tube), to the end of which he places his palm on the side of the other, open eye. In the presence of binocular vision, the impression of a “hole” in the palm is created, through which the picture visible through the tube is perceived. The phenomenon can be explained by the fact that the picture visible through the hole in the tube is superimposed on the image of the palm in the other eye. With simultaneous vision, unlike binocular vision, the “hole” does not coincide with the center of the palm, and with monocular vision the phenomenon of the “hole” in the palm does not appear.

An experiment with knitting needles (they can be replaced with ballpoint pen refills, etc.) is carried out as follows. The needle is fixed in a vertical position or held by the examiner. The task of the subject, who has the second knitting needle in his hand, is to align it along the axis with the first knitting needle. If you have binocular vision, the task is easily accomplished. In its absence, a miss is noted, which can be verified by conducting an experiment with two and one eyes open.

The test of reading with a pencil (or pen) consists of placing a pencil a few centimeters from the reader’s nose and 10-15 cm from the text, which naturally covers some of the letters of the text. Reading in the presence of such an obstacle without moving your head is possible only if you have binocular vision, since letters covered with a pencil for one eye are visible to the other and vice versa.

Binocular vision is a very important visual function. Its absence makes it impossible to perform high-quality work as a pilot, installer, surgeon, etc. Binocular vision is formed by the age of 7-15. However, a child aged 6-8 weeks shows the ability to fix an object with both eyes and follow it, and a 3-4 month old has fairly stable binocular fixation. By 5-6 months, the main reflex mechanism of binocular vision is formed - fusion reflex- the ability to merge two images from both retinas in the cerebral cortex into a single stereoscopic picture. If a 3-4 month old child still has dissociated eye movements, he or she should be consulted by an ophthalmologist.

To implement binocular vision, which can be considered as a closed dynamic system of connections between the sensitive elements of the retina, subcortical centers and the cerebral cortex (sensory), as well as 12 extraocular muscles (motor), a number of conditions are necessary: ​​visual acuity in each eye, as a rule, not lower than 0.3-0.4, parallel position of the eyeballs when looking at a distance and corresponding convergence when looking close, correct associated eye movements in the direction of the object in question, the same size of the image on the retinas, the ability for bifoveal fusion (fusion).

By the presence or absence of binocular vision, one can distinguish real strabismus from imaginary, apparent, and from hidden - heterophoria.

Most people have a small angle (within 3-4°) between the optical axis passing through the center of the cornea and the nodal point of the eye, and the visual axis running from the central fovea of ​​the macula through the nodal point to the object fixed by the gaze. Imaginary strabismus is caused by the fact that the discrepancy between the visual and optical axes reaches a greater value (in some cases 10°), and the centers of the corneas shift to one side or another, creating the impression of strabismus. However, the preservation of binocular vision in such individuals makes it possible to establish correct diagnosis. Imaginary strabismus does not need correction.

Hidden strabismus, or heterophoria, is associated with the lack of complete harmony in the tone and activity of the oculomotor muscles and is expressed in the deviation of one of the eyes during a period when a person does not fix any object with his gaze, for example, he thinks, “withdrawing into himself.” Hidden strabismus is much more common than orthophoria - a condition in which the centers of the corneas correspond to the middle of the palpebral fissure, and the visual axes of both eyes are parallel and directed to infinity.

Hidden strabismus is detected by turning off one eye from the act of binocular vision. The simplest way to determine heterophoria is as follows. The subject is asked to fixate with both eyes an object, for example, a researcher’s finger, and then one eye is covered with his hand, like a screen. After a few seconds, the hand is removed and the position of the eye is observed. If he made an adjustment movement towards the object fixed by the second eye, then it was rejected behind the screen, which indicates the presence of strabismus, corrected by an impulse to binocular vision. Based on the described eye movement, the presence of binocular vision is also judged. With orthophoria, the eye remains at rest.

Heterophoria, since it is corrected by the act of binocular vision, does not require treatment, except for persons in whom binocular vision is difficult due to significant hidden strabismus. In such cases, prismatic glasses are prescribed, they resort to decentering of conventional corrective glasses, and sometimes to surgical treatment.

Thus, neither false strabismus nor most cases of heterophoria are pathological. It includes only obvious strabismus, which is divided into friendly and paralytic. This division is somewhat schematic, but nevertheless convenient for understanding the essence and principles of treatment of both pathological process.

Our eyes have the unique ability to form a single visual image. This skill is called binocular vision. It helps us navigate space, see objects in volume, and correctly assess distances.

Thanks to this natural gift, our eyes see not only in front of us, but also capture images to the sides, above and below. This ability of the eye is directly related to many conditions.

• both eyes have approximately equal visual acuity;
• the degree of refraction in both eyes should also not differ;
• equal muscle balance is important;
• eyeballs must be located on the same plane or axis, etc.

Each of these conditions is important to a certain extent. If one ability of the eye is impaired, binocular vision may also be impaired.

How does this happen?

The ability to see three-dimensionally is formed in the cerebral cortex and is called fusion. The picture must fall on symmetrical points on the retinas of the two eyes, which are in interaction, and from there it is transmitted to the brain. If the image is transmitted to asymmetrical points, ghosting occurs. A newborn baby does not have binocular vision because he does not yet have the ability to move his eyes in a coordinated manner. Only at 6-8 weeks little man the ability to focus on an object with both eyes appears. And the fusion reflex is fully formed by 5-6 months. This is why it is important to take your child to an ophthalmologist in the first year of life. Fully stereoscopic vision develops by 8-9 years of age, which means that if you have problems, you will have time to fix them. to correct.

Reason for violations

All reasons when binocular vision suffers can be divided into three parts:

• muscle coordination problems;
• violation of image synchronization;
• a combination of these two pathologies.

Important to install the real reason, due to which the patient experiences difficulty with vision. This ability of the eye often suffers due to visual impairment, as well as all kinds of neurological diseases. Brain stem damage infectious diseases, the most various inflammations– each of these cases must be sorted out by a specialist who will conduct a thorough examination and prescribe treatment.

Strabismus and its consequences

Most common cause This disease, according to experts, is strabismus. It can be congenital or acquired due to various diseases or injuries. There are convergent, divergent and vertical strabismus, hidden and obvious. The eye may deviate to the right left side. In adult patients with strabismus, double vision often occurs, and complaints of dizziness, headaches, and nausea appear. This often becomes the reason that a person withdraws into himself, becomes irritable, and experiences difficulties finding employment. Modern ophthalmology knows many ways to correct strabismus: corrective glasses, physiotherapy, rehabilitation exercises, as well as surgical correction. At the OPTIC CITY salon in South Butovo, in the children's vision care room, this disorder is treated using the Sinoptofor device, and computer programs and diploptics are also used.

When is surgery needed?

Squint surgery is performed if more than one and a half to two years conservative treatment nothing has changed, the angle of strabismus has a stable value. A surgical stage of treatment is also recommended for large strabismus angles. Usually the operation is performed on children aged 3 to 7 years, but adults can also change their lives with the help of ophthalmic surgery. In 80-90% of cases, doctors manage to rid the patient of this diagnosis. The operation is performed under local anesthesia, in some clinics it is carried out without hospitalization and the patient can return home on the same day. However, after surgical intervention It is still necessary to carry out hardware restoration procedures that will help consolidate the result.

Why is diagnosis important?

Often people adapt to vision problems and do not pay attention to it for years. At the same time, impaired stereoscopic vision significantly reduces the quality of life. Don’t be lazy to undergo an ophthalmological examination at least once a year. For example, in any OPTIC CITY salon, where experienced ophthalmologists always conduct appointments. As for strabismus, an extended vision test is especially important for this disease. The ophthalmologist conducts an examination of the anterior segment of the eye, a number of special tests, and checks visual acuity, including using computer equipment and using trial lenses. IN childhood early diagnosis strabismus can radically change the course of the disease. The child's brain adapts to new visual conditions much faster than adults, so correcting this disorder at an early stage is much easier. In OPTIC CITY, vision testing for children is carried out in almost every salon. If necessary, our pediatric ophthalmologists can refer the little patient to specialized clinics for a more in-depth examination.

Testing stereoscopic vision

There are several ways to independently test stereoscopic vision. Let's list the most famous:

- Hole method.

Look into the tube with one eye, like spyglass. Place your palm in front of the other eye at a distance from the tube. With unimpaired binocular vision, the subject sees a hole in the palm. This trick is explained by the fact that the image of the two eyes merges into one.

- Test with two pencils

Ask an assistant to hold one pencil vertically, and hold the other one yourself, and try, looking with both eyes, to connect the ends of the pencils so that they create one continuous line. Then repeat the experiment with one eye closed. If a vision problem exists, you will not be able to connect the pencils.

- Experience with the book

Place a pencil to your nose and, looking at it, try to read the text that is in front of you. Try not to move your head, curse or move the text away. If there are no violations, you will be able to cope with this task.

When performing diagnostics in the office, doctors most often use the four-point test. Experts consider this experience the most revealing. The patient is asked to wear special glasses in which both lenses have different colors - green and red. Circles of various shades appear on the monitor. Depending on what colors the subject sees, the doctor draws a conclusion about existing binocular vision impairments. In the OPTIC CITY salon in Butovo they also use diagnostics on a special Synoptophore apparatus.

You can perform some of these tests yourself if you suspect that you have impaired stereoscopic vision. But it is better to turn to professionals for full diagnostics on modern equipment.

Vision test for special occasions

Before studying binocular vision, a test is performed with covering the eye (“carpet test”), which makes it possible to establish with a high probability the presence of obvious or hidden strabismus. The sample is made as follows. The person conducting the study sits opposite the patient at a distance of 0.5-0.6 m from him and asks the patient to look intently, without blinking, at some distant object located behind the examiner. At the same time, he alternately covers either the patient’s right or left eye with his hand or an opaque screen without intervals.

If at the moment of opening neither eye makes movements, then most likely there is no strabismus; if there is movement, then there is strabismus. If the movement of the eye when opening (transferring the shutter to the other eye) occurs towards the nose, then the strabismus is divergent, if towards the ear it is convergent, i.e., the opposite angle of the strabismus. These eye movements are called adjustment movements. To determine the nature of strabismus (hidden or obvious), first one and then the other eye is closed and opened. In the case of obvious strabismus, when opening one of the eyes (leading), both eyes make a quick adjustment movement in one direction, and when opening the other eye (squinting), they remain motionless. In the case of hidden strabismus (heterophoria), when each eye opens, a slow (vergence) movement of only that eye occurs.

The actual study of binocular vision includes determining the nature of vision (with two open eyes), study of muscle balance (phoria), aniseikonia, fusion reserves, stereoscopic vision.

Determination of the nature of vision. The presence or absence of binocular vision is determined using the “four-point test”. This test was proposed by the English ophthalmologist Wars. The subject observes 4 glowing circles different color through filter glasses. The colors of the circles and lenses are selected in such a way that one circle is visible to only one eye, two circles are visible only to the other, and one circle (white) is visible to both eyes.

We produce a color test device TsT-1. The round lantern, the front wall of which is covered with a black lid, has 4 round holes arranged in the shape of a letter “T” turned to its side: the top and bottom are covered with green filters, the right one is covered with red, and the middle one is covered with colorless frosted glass. The flashlight is hung on the wall next to the table or screen to study visual acuity.

82. Color test TsT-1 - a device for studying binocular vision. 3 - green; K - red; B - white.

There are three possible test results: binocular (normal), simultaneous and monocular vision. In this case, the simultaneous is further divided into different kinds strabismus, and monocular has two options depending on the dominant eye.

Table 6. Interpretation of the results of the color test study

The study of phoria is carried out as follows. The patient puts on a trial frame with lenses that completely correct ametropia. A Maddox cylinder is inserted into one of the sockets (usually the right one) in a horizontal position of the axis, and a prismatic compensator with vertical position handles and zero position of marks on the scale. The subject is asked to look at a point source of light located at a distance of 5 m from him, and he must indicate on which side of the light bulb there is a vertical red stripe.

If the stripe passes along the light bulb, then the patient has orthophoria, if to the side of it - heterophoria. Moreover, if the stripe passes on the same side of the light bulb on which the Maddox cylinder is located, then the patient has esophoria, if on the opposite side, then exophoria. To determine the degree of heterophoria, rotate the compensator roller (or change the prisms in the frame) until the strip intersects the light bulb. At this moment, the division on the compensator scale will indicate the amount of heterophoria in prism diopters. In this case, the position of the prism with the base towards the temple indicates esophoria, and with the base towards the nose – exophoria.

Since subjects have a tendency to self-compensate for heterophoria, it is recommended to cover the eye against which the Maddox cylinder is located with a shield and record the position of the strip only at the first moment after its opening.

After determining the horizontal phoria, the vertical one is examined. To do this, the Maddox cylinder is positioned with its axis vertical, and the prismatic compensator is positioned with the handle horizontally. When examining, make sure that the horizontal red stripe intersects the light bulb.

There are other ways to determine heterophoria, in which the separation of the visual fields of the two eyes is not as complete, for example, when studying using filters of additional colors, the so-called color anaglyphs. This is the Schober test. Using a projector, the patient is shown two concentric green circles with a red cross in the center.

83. Schober test for studying heterophoria.

Using a prism compensator or prisms from the set, the cross is moved to the center.

In this case, the bases of the prisms should be facing in the direction where the image of a given eye is shifted.

The value of heterophoria measured using the Schober method is usually somewhat less than when determining it using the Maddox method, since in this case the separation of the visual fields of the right and left eyes is incomplete; the subject sees with both eyes the screen and objects located around it.

The less completely the division of visual fields is made, the lower the value of heterophoria. In some countries, a method for studying binocular balance with minimal field separation—fixation disparity—has become widespread.

Field separation is accomplished using Polaroid filters placed in front of the eyes. The subject watches a screen on which there are signs (letters or numbers) visible with both eyes on the periphery of the field and a horizontal stripe in the middle of the field. In the middle of this stripe there are two vertical luminous marks, covered with Polaroid glasses, that is, visible separately to the right and left eyes.

84. Test for studying fixation disparity.

Fixation disparity is measured repeatedly by applying various prisms (rotating the prism compensator) with the base to the nose and temple. By its size (no more than 30") and resistance to the “load” of prisms, the stability of binocular vision is judged.

Study of fusion reserves. Fusion reserves are examined using a synoptophore, or prismatic compensator.

A synoptophore is a device for the diagnosis and treatment of binocular vision disorders, mainly with strabismus. It is equipped with two movable heads, each of which contains a light source, a system of mirrors and lenses, and a socket for a slide.

85. Synoptophore.

The heads can move along an arc and also rotate around their axis. Thus, the angle between the visual lines of the two eyes can vary from +30° to -50°. Consequently, with strabismus, it is possible to project similar objects to the two eyes onto the central fovea of ​​the retina and cause their fusion.

Synoptophore slides contain three groups of objects:
1) objects for combination that do not have common elements, for example, an egg and a chicken, a garage and a car, a circle and a star inscribed in it;
2) objects for merging, which are silhouette figures with a large central common element, for example, two cats, one of which has ears but no tail, and the other has a tail but no ears;
3) objects in stereopsis - two similar pictures, in one of which some of the details are shifted horizontally; when merging, this creates the effect of disparity and reproduces a sense of depth - some details are visible closer to the person being examined, while others are further away from him.

Objects of the 1st group are used to determine phoria, and in the presence of strabismus, its angle. Objects of the 3rd group are used for research and training of stereo vision. Objects of the 2nd group are used to study the ability to fusion and fusion reserves.

To determine fusion reserves, slides of the 2nd group, for example “cats”, are installed in the heads of the synoptophore. Place the heads at position 0 on the arc scale. The subject is asked if he sees one cat with a tail and ears. If he doesn’t see, then slides of the first group are introduced, for example with the image of a chicken and an egg, and the heads are moved in an arc until the chicken is in the center of the egg.

If the answer is yes, then they begin to slowly move the heads in an arc towards each other until the subject begins to notice a split in the picture: instead of one cat, two appear. The sum of the divisions on which the heads are located at this moment will indicate a positive fusion reserve.

Fusional reserve, like phoria, can be measured in degrees and prism diopters.

Fusion reserves are measured using a prism compensator as follows.

The subject, wearing a trial frame, with prismatic compensators inserted into both sockets (with the handle in a vertical position), observes from a distance of 5 m a vertical black stripe on a white background. Rotate the roller of both strip compensators. At this point, the sum of the divisions on the scales will indicate a positive fusion reserve. Then the rotation of the prisms is repeated with the bases towards the nose, i.e. towards each other. The moment the band splits will indicate the negative fusion reserve in prismatic diopters.

Approximate norms of fusion reserves: 40-50 prdptr (20-25°) - positive, 6-10 prdptr (3-5°) - negative.

Yu.Z. Rosenblum