The book by the famous American neurophysiologist, Nobel Prize winner, summarizes modern ideas about how the neural structures of the visual system, including the cerebral cortex, are arranged and how they process visual information. With a high scientific level of presentation, the book is written in a simple, clear language, beautifully illustrated. It can serve as a textbook on the physiology of vision and visual perception.

For students of biological and medical universities, neurophysiologists, ophthalmologists, psychologists, specialists in computer technology and artificial intelligence.

Book:

The distance estimation mechanism based on the comparison of two retinal images is so reliable that many people (unless they are psychologists and visual physiologists) are not even aware of its existence. To see the importance of this mechanism, try driving a car or bicycle, playing tennis, or skiing with one eye closed for a few minutes. Stereoscopes have gone out of fashion and you can only find them in antique shops. However, most readers have watched stereoscopic films (where the viewer has to wear special glasses). The principle of operation of both a stereoscope and stereoscopic glasses is based on the use of the stereopsis mechanism.

The images on the retinas are two-dimensional, yet we see the world in three dimensions. It is obvious that the ability to determine the distance to objects is important for both humans and animals. Similarly, perceiving the three-dimensional shape of objects means judging relative depth. Consider, as a simple example, a round object. If it is oblique with respect to the line of sight, its image on the retinas will be elliptical, but usually we easily perceive such an object as round. This requires the ability to perceive depth.

A person has many mechanisms for estimating depth. Some of them are so obvious that they hardly deserve mention. However, I will mention them. If the approximate size of an object is known, for example in the case of objects such as a person, a tree or a cat, then we can estimate the distance to it (although there is a risk of making a mistake if we encounter a dwarf, bonsai or lion). If one object is located in front of the other and partially obscures it, then we perceive the front object as being closer. If we take a projection of parallel lines, for example, railroad tracks going into the distance, then in the projection they will converge. This is an example of perspective - a very effective measure of depth. The convex section of the wall appears lighter in its upper part if the light source is located higher (usually the light sources are at the top), and the recess in its surface, if it is illuminated from above, appears darker in the upper part. If the light source is placed below, then the bulge will look like a recess, and the recess will look like a bulge. An important indicator of distance is motion parallax- the apparent relative displacement of near and more distant objects if the observer moves his head left and right or up and down. If some solid object is rotated, even at a small angle, then its three-dimensional shape is immediately revealed. If we focus the lens of our eye on a nearby object, then the more distant object will be out of focus; thus, changing the shape of the lens, i.e. by changing the accommodation of the eye (see Chapters 2 and 6), we are able to estimate the distance of objects. If you change the relative direction of the axes of both eyes, bringing them together or spreading them (carrying out convergence or divergence), then you can bring together two images of an object and keep them in this position. Thus, by controlling either the lens or the position of the eyes, one can estimate the distance of an object. The designs of a number of rangefinders are based on these principles. With the exception of convergence and divergence, all other distance measures listed so far are monocular. The most important depth perception mechanism, stereopsis, depends on the sharing of two eyes. When viewing any three-dimensional scene, the two eyes form slightly different images on the retina. You can easily be convinced of this if you look straight ahead and quickly move your head from side to side by about 10 cm or quickly close one eye or the other in turn. If you have a flat object in front of you, you won't notice much of a difference. However, if the scene includes objects at different distances from you, you will notice significant changes in the picture. During stereopsis, the brain compares images of the same scene on two retinas and estimates relative depth with great accuracy.

Suppose the observer fixes a certain point P with his gaze. This statement is equivalent to saying: the eyes are directed in such a way that the images of the point are in the central pits of both eyes (F in Fig. 103). Suppose now that Q is another point in space that appears to the observer to be located at the same depth as P. Let Q L and Q R be the images of point Q on the retinas of the left and right eyes. In this case, the points Q L and Q R are called corresponding points two retinas. It is obvious that two points coinciding with the central pits of the retinas will be corresponding. It is also clear from geometrical considerations that the point Q", estimated by the observer as located closer than Q, will give two projections on the retinas - Q "L and Q" R - at non-corresponding points located farther apart than in the case if these points were corresponding (this situation is depicted on the right side of the figure.) In the same way, if we consider a point located farther from the observer, then it turns out that its projections on the retinas will be located closer to each other than the corresponding points. what is said above about the corresponding points are partly definitions, and partly statements arising from geometric considerations.When considering this issue, the psychophysiology of perception is also taken into account, since the observer subjectively evaluates whether an object is located further or closer to the point P. Let us introduce another definition.All points , which, like point Q (and, of course, point P), are perceived as equidistant, lie on horoptera- a surface passing through the points P and Q, the shape of which differs from both a plane and a sphere and depends on our ability to estimate the distance, i.e. from our brain. The distances from the fovea F to the projections of the Q point (Q L and Q R) are close, but not equal. If they were always equal, then the line of intersection of the horopter with the horizontal plane would be a circle.

Rice. 103. Left: if the observer looks at point P, then two of its images (projections) fall on the central pits of two eyes (point F). Q - point, which, according to the observer, is at the same distance from him as P. In this case, we say that two projections of the Q point (Q L and Q R) fall into the corresponding points of the retinas. (A surface composed of all points Q that appear to be at the same distance from the observer, the same as point P, is called a horopter passing through point P). On right: if the point Q "is closer to the observer than Q, then its projections on the retinas (Q" L and Q "R) will be further apart horizontally than if they were at the corresponding points. If the point Q" was further, then the projections Q "L" and Q "R would have been shifted horizontally closer to each other.

Suppose now that we are fixing a certain point in space with our eyes and that in this space there are two point sources of light that give a projection on each retina in the form of a point of light, and these points are not corresponding: the distance between them is several more, than between corresponding points. Any such deviation from the position of the corresponding points we will call disparity. If this deviation in the horizontal direction does not exceed 2° (0.6 mm on the retina), and vertically does not exceed a few minutes of arc, then we will visually perceive a single point in space located closer than the one we fix. If the distances between the projections of the point are not greater, but less, than between the corresponding points, then this point will appear to be located farther than the fixation point. Finally, if the vertical deviation exceeds a few arc minutes, or the horizontal deviation is greater than 2°, then we will see two separate points, which may appear to be further or closer to the fixation point. These experimental results illustrate the basic principle of stereo perception, first formulated in 1838 by Sir C. Wheatstone (who also invented the device known in electrical engineering as the "Wheatstone bridge").

It seems almost unbelievable that before this discovery, no one seemed to have realized that the presence of subtle differences in the images projected on the retinas of the two eyes can lead to a distinct impression of depth. Such a stereo effect can be demonstrated in a few minutes by any person who can arbitrarily reduce or separate the axes of his eyes, or by someone who has a pencil, a piece of paper and several small mirrors or prisms. It is not clear how Euclid, Archimedes and Newton missed this discovery. In his article, Wheatstone notes that Leonardo da Vinci came very close to discovering this principle. Leonardo pointed out that a ball located in front of a spatial scene is seen differently by each eye - with the left eye we see its left side a little further, and with the right eye - the right. Wheatstone further notes that if Leonardo had chosen a cube instead of a sphere, he would certainly have noticed that its projections are different for different eyes. After that, he might, like Wheatstone, be interested in what would happen if two similar images were specifically projected onto the retinas of two eyes.

An important physiological fact is that the sensation of depth (i.e. the ability to “directly” see, one or another object is located farther or closer to the fixation point) occurs when two retinal images are slightly shifted relative to each other in the horizontal direction - moved apart or, conversely, are close together (unless this displacement exceeds about 2°, and the vertical displacement is close to zero). This, of course, corresponds to geometric relationships: if an object is located closer or farther with respect to a certain distance reference point, then its projections on the retinas will be moved apart or brought closer horizontally, while there will be no significant vertical displacement of images.

This is the basis of the action of the stereoscope invented by Wheatstone. The stereoscope was so popular for about half a century that almost every home had one. The same principle underlies the stereo movies that we now watch using special polaroid glasses for this. In the original design of the stereoscope, the observer viewed two images placed in a box using two mirrors that were positioned so that each eye saw only one image. Prisms and focusing lenses are now often used for convenience. The two images are identical in every way, except for small horizontal offsets, which give the impression of depth. Anyone can produce a photograph suitable for use in a stereoscope by selecting a fixed object (or scene), taking a picture, then moving the camera 5 centimeters to the right or left and taking a second picture.

Not everyone has the ability to perceive depth with a stereoscope. You can easily check your stereopsis yourself if you use the stereopairs shown in Fig. 105 and 106. If you have a stereoscope, you can make copies of the stereo pairs shown here and paste them into the stereoscope. You can also place a thin piece of cardboard perpendicularly between two images from the same stereopair and try to look at your image with each eye, setting the eyes parallel, as if you were looking into the distance. You can also learn to move your eyes in and out with your finger, placing it between the eyes and the stereo pair and moving it forward or backward until the images merge, after which (this is the most difficult) you can examine the merged image, trying not to split it into two. If you succeed, then the apparent depth relationships will be the opposite of those perceived when using a stereoscope.

Rice. 104. BUT. Wheatstone stereoscope. B. Diagram of Wheatstone's stereoscope, drawn up by himself. The observer sits in front of two mirrors (A and A"), placed at an angle of 40 ° to the direction of his gaze, and looks at two pictures combined in the field of view - E (with the right eye) and E" (with the left eye). In a simpler version created later, two pictures are placed side by side so that the distance between their centers is approximately equal to the distance between the eyes. The two prisms deflect the direction of gaze so that, with proper convergence, the left eye sees the left image and the right eye sees the right image. You yourself can try to do without a stereoscope by imagining that you are looking at a very distant object with eyes whose axes are set parallel to each other. Then the left eye will look at the left image, and the right eye will look at the right one.

Even if you fail to repeat the experience with depth perception - whether because you do not have a stereoscope, or because you cannot arbitrarily move the axes of the eyes together - you will still be able to understand the essence of the matter, although you will not get stereo enjoyment.

In the upper stereopair in Fig. 105 in two square frames there is a small circle, one of which is shifted slightly to the left of the center, and the other is slightly to the right. If you consider this stereopair with two eyes, using a stereoscope or another method of image alignment, you will see a circle not in the plane of the sheet, but in front of it at a distance of about 2.5 cm. If you also consider the lower stereopair in fig. 105, the circle will be visible behind the sheet plane. You perceive the position of the circle in this way because exactly the same information is received on the retinas of your eyes as if the circle really located in front of or behind the plane of the frame.

Rice. 105. If the upper stereo pair is inserted into the stereoscope, then the circle will look ahead of the frame plane. In the lower stereopair, it will be located behind the frame plane. (You can do this experiment without a stereoscope, by convergence or divergence of the eyes; convergence is easier for most people. To make things easier, you can take a piece of cardboard and place it between two images of a stereo pair. At first, this exercise may seem difficult and tedious to you; do not be zealous at first At the convergence of the eyes on the upper stereopair, the circle will be visible farther than the plane, and on the lower one - closer).

In 1960, Bela Jules of Bell Telephone Laboratories came up with a very useful and elegant technique for demonstrating the stereo effect. The image shown in fig. 107, at first glance, seems to be a homogeneous random mosaic of small triangles. So it is, except that in the central part there is a hidden triangle of a larger size. If you look at this image with two pieces of colored cellophane placed in front of your eyes - red in front of one eye and green in front of the other, then you should see a triangle in the center protruding forward from the plane of the sheet, as in the previous case with a small circle on stereopairs . (You may have to watch for a minute or so the first time, until the stereo effect occurs.) If you swap the pieces of cellophane, a depth inversion will occur. The value of these Yulesh stereo pairs lies in the fact that if your stereo perception is disturbed, then you will not see a triangle in front of or behind the surrounding background.

Rice. 106. Another stereo pair.

Summing up, we can say that our ability to perceive the stereo effect depends on five conditions:

1. There are many indirect signs of depth - partial obscuration of some objects by others, motion parallax, object rotation, relative dimensions, shadow casting, perspective. However, stereopsis is the most powerful mechanism.

2. If we fix a point in space with our eyes, then the projections of this point fall into the central pits of both retinas. Any point judged to be at the same distance from the eyes as the fixation point forms two projections at the corresponding points on the retinas.

3. The stereo effect is determined by a simple geometric fact - if an object is closer than the fixation point, then its two projections on the retinas are farther apart than the corresponding points.

4. The main conclusion based on the results of experiments with the subjects is as follows: an object whose projections on the retinas of the right and left eyes fall on the corresponding points is perceived as located at the same distance from the eyes as the point of fixation; if the projections of this object are moved apart in comparison with the corresponding points, the object seems to be located closer to the fixation point; if, on the contrary, they are close, the object seems to be located further than the fixation point.

5. With a horizontal projection shift of more than 2° or a vertical shift of more than a few minutes of arc, doubling occurs.

Rice. 107. In order to get this image called anaglyph, Bela Jules first built two systems of randomly placed small triangles; they differed only in that 1) one system had red triangles on a white background, while the other had green triangles on a white background; 2) within the large triangular zone (near the center of the figure), all green triangles are somewhat shifted to the left compared to the red ones. After that, the two systems are aligned, but with a slight shift so that the triangles themselves do not overlap. If the resulting image is viewed through a green cellophane filter, only red elements will be visible, and if through a red filter, only green elements will be visible. If you put a green filter in front of one eye and a red filter in front of the other, you will see a large triangle protruding about 1 cm in front of the page. If the filters are swapped, the triangle will be visible behind the page plane.

The image of objects on the retinas of the eyes is two-dimensional, but meanwhile a person sees the world in three dimensions, i.e. he has the ability to perceive the depth of space, or stereoscopic (stereo - from the Greek stereos - solid, spatial) vision.

A person has many mechanisms for estimating depth. Some of them are quite obvious. For example, if the approximate value of an object (a person, a tree, etc.) is known, then it is possible to estimate the distance to it or understand which of the objects is closer by comparing the angular value of the object. If one object is located in front of the other and partially obscures it, then the person perceives the front object as being closer. If we take a projection of parallel lines, for example, railroad tracks going into the distance, then in the projection they will converge. This is an example of perspective - a very effective indicator of the depth of space.

The convex section of the wall appears lighter in its upper part if the light source is located higher, and the depression in its surface appears darker in the upper part. An important sign of remoteness is motion parallax - the apparent relative displacement of near and more distant objects if the observer moves his head left and right or up and down. The “railway effect” is known when viewed from the window of a moving train: the apparent speed of movement of closely spaced objects is higher than those located at a great distance.

It is also possible to estimate the distance of objects by the size of the accommodation of the eye, i.e. by the tension of the ciliary body and the zinn ligaments that control the lens. By strengthening convergence or divergence, one can also judge the remoteness of the object of observation. With the exception of the latter, all of the above distance indicators are monocular. The most important depth perception mechanism, stereopsis, depends on the sharing of two eyes. When viewing any three-dimensional scene, the two eyes form slightly different images on the retinas.

During stereopsis, the brain compares images of the same scene on two retinas and estimates relative depth with great accuracy. The fusion of two monocular images, seen separately by the right and left eyes when viewing objects simultaneously with two eyes, into one three-dimensional image is called fusion.

Assume that the observer fixes his gaze on some point R, (Fig. 1) in this case, the images of the point are in the central fovea (fovea) F both eyes. Let Q be another point in space that appears to the observer to be at the same depth as the point R, while Q L and Q R are images of the Q point on the retinas of the left and right eyes. In this case, the points Q L and Q R are called corresponding points of two retinas.

Fig 1. Geometric scheme for explaining the stereo effect

It is obvious that two points coinciding with the central pits of the retinas are also corresponding. From geometric considerations, it is clear that the point Q′, estimated by observers as located closer than the point Q, will give two images on the retinas - Q′ L and Q′ R - at non-corresponding (disparate) points located farther apart than at if these points were corresponding.

In the same way, if we consider a point located farther from the observer, then it turns out that its projections on the retinas will be located closer to each other than the corresponding points. All points which, like the points Q and R, are perceived as equidistant, lie on horoptera- the surface passing through the points R and Q, which has a different shape than a sphere and depends on a person's ability to judge distance. Distances from the fovea F up to the projections Q R and Q L for the right and left eyes are close, but not equal, if they were always equal, then the line of intersection of the horopter with the horizontal plane would be a circle.

Angles α and α′ in stereoscopy are called parallactic angles. Their value will change from zero, when the fixation point lies at infinity, and up to 15°, when the fixation point is at a distance of 250 mm.

Suppose now that we are fixing a certain point in space with our eyes and that in this space there are two point sources of light, one of which is projected only on the retina of the left eye, and the other - on the right eye in the form of points of light, and these points are non-corresponding: the distance between them slightly more than between the corresponding points. Any such deviation from the position of the corresponding points is called disparity. If this deviation in the horizontal direction does not exceed 2° (0.6 mm on the retina), and in the vertical direction - no more than a few minutes of arc, then we will visually perceive a single point in space located closer than the fixation point.

If the distances between the projections of a point are no more, but less than between the corresponding points, then this point will seem to be located further than the fixation point. Finally, if the vertical deviation exceeds a few arc minutes, or the horizontal deviation is greater than 2°, then we will see two separate points, which may appear to be further or closer to the fixation point. Such an experiment illustrates the basic principle of stereo perception, first formulated by C. Wheatstone in 1838 and underlying the creation of a whole series of stereoscopic instruments, starting with the Wheatstone stereoscope up to stereo rangefinders and stereo television.

Not everyone has the ability to perceive depth with a stereoscope. You can easily check your stereopsis yourself if you use Fig.2. If you have a stereoscope, you can make copies of the stereo pairs shown here and paste them into the stereoscope. You can also place a thin sheet of cardboard perpendicularly between two images from the same stereopair and try to look at your image with each eye, setting the eyes parallel as if you were looking into the distance.

Fig 2. Examples of stereopairs

In 1960, Bela Yulesh (Bell Telephone Laboratories, USA) proposed an original method for demonstrating the stereo effect, excluding monocular observation of an object.

Based on this principle, by the way, a whole series of entertaining books has been published, which, at the same time, can also be used to train stereopsis. Figure 3 shows one of the drawings from this book in black and white. By setting the visual lines of your eyes in parallel (for this you need to look into the distance, as if through a drawing), you can see a stereoscopic picture. Such patterns are called autostereograms. Based on the method of Bel Yulesh, the Novosibirsk State Medical Institute, together with the Novosibirsk State Technical University, created a device for studying the threshold of stereoscopic vision, and we proposed its modification, which makes it possible to increase the accuracy of determining the threshold of stereoscopic vision. The measurement of the threshold of stereoscopic vision is based on the presentation of test objects to each eye of the observer against the so-called randomized background. Each of these test objects is a set of points on the plane, located according to an individual probabilistic law. Moreover, each test object has identical areas of points, which can be a figure of arbitrary shape.

If identical points of figures on the test object have zero values ​​of parallax angles, then the observer sees the total picture in the generalized image in the form of a random distribution of points, in other words, the observer is not able to distinguish the figure against a randomized background. Thus, monocular vision of the figure is excluded. If one of the test objects is displaced perpendicular to the optical axis of the system, then the parallactic angle between the figures will change, and at a certain value of it, the observer will see a figure that, as it were, breaks away from the background and begins to approach or move away from it. The parallax angle is changed using an optical compensator inserted into one of the branches of the instrument. The moment the figure appears in the field of view is fixed by the observer, and the corresponding value of the stereoscopic vision threshold appears on the indicator.

Fig 3. Autostereogram

Studies of the last decades in the field of neurophysiology of stereoscopic vision have made it possible to identify specific cells tuned to disparity in the primary visual cortex of the brain. Cells were found that react only if the stimuli hit exactly the corresponding areas of the two retinas. Cells of the second type respond if and only if the object is located further than the fixation point. There are also cells that respond only when the stimulus is closer to the fixation point. Apparently, in the primary visual cortex there may be specific neurons for different degrees of disparity. All these cells also have the property of orientational selectivity and respond well to moving stimuli and to the ends of lines. According to D. Hubel, “although we still do not know exactly how the brain “reconstructs” a scene that includes many objects at different distances, cells that are sensitive to disparity are involved in the first stages of this process.”

When studying stereopsis, researchers faced a number of problems. It turned out that the processing of some binocular stimuli occurs in the visual system in a completely incomprehensible way. For example, if we turn again to the stereopairs shown in Fig. 37a and 37b, then we get the feeling that in one case the circle is located closer, in the other - further than the plane of the frame. If two stereopairs are combined, i.e. in each frame, place two circles located next to each other, then it would seem that we should see one circle closer, the other farther. However, in reality this will not work: both circles are visible at the same distance as the frame.

The second example of the unpredictability of binocular effects is the so-called struggle of the visual fields. If very different images are created on the retinas of the right and left eyes, then often one of them ceases to be perceived. If you look with your left eye at a grid of vertical lines and with your right eye at a grid of horizontal lines (for example, through a stereoscope), it is impossible to see both sets of lines at the same time. Either one or the other is visible, and each of them is only for a few seconds; sometimes you can see a mosaic of these images. The phenomenon of visual field struggle means that in cases where the visual system cannot combine images on two retinas, it simply rejects one of the images, either completely or partially.

So, for normal stereoscopic vision, the following conditions are necessary: ​​normal functioning of the oculomotor system of the eyes; sufficient visual acuity and not a very big difference in the acuity of the right and left eyes; strong connection between accommodation, convergence and fusion; small difference in image scales in the left and right eyes.

Size inequality or different scale of images obtained on the retinas of the right and left eyes when viewing the same object is called aniseikonia. Aniseikonia is one of the reasons for the instability or lack of stereoscopic vision. Aniseikonia is most often based on a difference in the refraction of the eyes, i.e. anisometronia. If aniseikonia does not exceed 2-2.5%, then it can be corrected with conventional stigmatic lenses, otherwise aniseikonic glasses are used.

Disruption of the connection between accommodation and convergence is one of the reasons for the appearance of various types of strabismus. Explicit strabismus, in addition to being a cosmetic defect, as a rule, leads to a decrease in visual acuity of the squinting eye until it is turned off from the process of vision. Hidden strabismus, or heterophoria, does not create a cosmetic defect, but may prevent stereopsis. So, persons with heterophoria more than 3 ° cannot work with binocular devices.

Threshold of stereoscopic vision characterize the minimum difference of parallactic angles Δα, which is still perceived by the observer. Relationship between Δα (in seconds) and minimum distance Δ l between objects that are perceived by the observer as being at different distances, the following:

,

where b is the distance between the pupils of the observer's eyes;
l is the distance from the eye to the nearest object under consideration.

The threshold of stereoscopic vision depends on various factors: the brightness of the background (the greatest sharpness is observed at a background brightness of about 300 cd/m2), the contrast of objects (with increasing contrast, the depth vision threshold decreases), and the duration of observation (Fig. 4).

Figure 4. Dependence of the threshold of stereoscopic vision on the duration of observation

The depth perception threshold under optimal observation conditions ranges from 10 - 12 to 5″ (for some observers it reaches 2 - 5″).

Taking the value Δα =10″ as the threshold, we can calculate the maximum distance at which the eye still perceives depth. This distance l= 1400 m (radius of stereoscopic vision).

There are several ways to assess, define and study stereoscopic vision:

1) using a stereoscope according to the Pulfrich tables (the minimum threshold for stereoscopic perception determined by this method is 15″);
2) using various types of stereoscopes with a set of more accurate tables with a measurement range of 10 - 90″;
3) using the device mentioned above, using a randomized background, which excludes monocular observation of objects, the measurement error is 1 - 2″.

The ability to see the world in volume gives a person binocular vision. With its violations, visual acuity worsens, problems arise with orientation in space. This happens for various reasons. Binocularity can be restored by hardware and surgical methods. The doctor also prescribes exercises for the eyes.

In this article

Before you begin to consider techniques for restoring binocular vision at home, you should understand what binocularity is, how this function of the visual apparatus works, and what causes the loss of binocular vision.

What is binocular vision and how does it work?

Binocular vision is vision with both eyes. It is also called stereoscopic and spatial, because it allows you to see in 3D projection. Thanks to this function, a person sees objects, recognizing their dimensions by width and height, shape, and the distance between them. Both eyes of a person receive one image each, which they transmit to the brain. It combines these images into one picture.

If there is no binocular vision, the brain will receive two different visual images that cannot be combined into one. As a result, diplopia occurs - double vision. This happens with anisometropia (a strong difference between the refraction of the right and left eyes), diseases of the lens, cornea and retina, damage to the nervous system, and for other reasons. Binocular vision is impossible if one eye is not involved in the process of visual perception, as is the case with strabismus.

The development of binocular vision begins in childhood. From the very first months, the prerequisites for its emergence and development begin to form. First, the child develops photosensitivity, color perception, and central vision. Over time, visual acuity improves, the field of vision expands. All this contributes to the formation of binocularity. This process is completed by about 12-14 years. Violations can occur at any age. A variety of factors can provoke them.

Causes of impaired binocular vision

The main reason for the lack of binocular vision is uncoordinated movements of the eyeballs. This occurs due to weakening of the eye muscles or damage to the oculomotor muscles. The eyes begin to look in different directions, the visual axis shifts, which leads to a deterioration in the visual functions of one eye. In some cases, there is a complete loss of vision by one of them. This pathology often occurs in childhood and manifests itself in strabismus, the most common form of binocular vision impairment.

There are other reasons for the loss of binocularity. In fact, there are a lot of them. Hemorrhages in the retina, cataracts, rupture of the retina cause a strong deterioration in the visual abilities of the eye, and one of the conditions for the existence of stereoscopic vision is the absence of pathologies of the retina and cornea.

Thus, the loss of binocular vision is caused by various pathologies of the body, in general, and the eyes, in particular. Any disease that adversely affects the health of the eyes and vision can become a factor that provokes violations of spatial perception.

Recovery of binocular vision

The restoration of binocularity begins with the treatment of the pathology that led to visual impairment. Only after eliminating the causes, you can return stereoscopic vision.

The most common pathology in which binocular vision is absent is strabismus. This ophthalmic disease is treated with the help of surgery, hardware methods and eye gymnastics. Surgical intervention is necessary only in extreme cases, when the eye is strongly displaced from its normal position and is not involved in the process of vision.

Recovery and training of binocular vision at home

Daily training of spatial vision is the key to its rapid recovery. There are various exercises that you can do on your own right at home. The simplest is the exercise with a sheet of paper.

leaf exercise

You will need a paper sheet on which you need to draw a vertical line 10 cm long and 1 cm wide with a felt-tip pen. Attach the sheet to the wall at eye level and move 1 meter away from it. Look at the line and tilt your head down a little, continuing to look at the line until it begins to double. Next time, take your head up, and then to the sides. It is necessary to perform such exercises three times a day for five minutes. A prerequisite for implementation is good lighting in the room.

This exercise is the simplest in terms of technique. There are other techniques related to focusing. They also contribute to the training and restoration of binocular vision.

Exercise "Workout"

Place some object (a sheet with an image) on the wall and move away from it at a distance of 2-3 meters. Next, you should clench your fist, but at the same time the index finger should be extended upwards. The hand is located at a distance of 40 cm from the face, and the tip of the index finger should be on the same visual axis as the object on the wall. Look at an object through your fingertip. It will immediately begin to split. After that, you need to move the focus from the wall to the finger. At this point, the visual object will begin to double. So you can train both eyes alternately. It is the weak eye that should be loaded more. The workout will take you about 3-5 minutes. It is advisable to perform it several times a day. Over time, you will notice that your visual acuity has improved.

Focusing exercise

It will require a colored object (any picture). First you need to look at the whole picture, then at its individual details (the image should be complex, multi-colored). Then an even smaller object is selected. So, if the object is a butterfly, then first you examine it as a whole, then outline its contour with your eyes, then examine the wing or its half. The last object to focus on it should be no more than 0.5 cm in size. This way you will gradually learn to focus faster and more accurately without straining your eyes.

Exercise "Stereogram"

The stereogram drawing can be downloaded from the Internet and printed. It is encrypted drawings in which you can see any figures. The stereogram should be located at a distance of 30-40 cm from the face. The gaze must be focused as if behind the image. After a while, the hidden picture will begin to appear. After this has happened, you need to increase the distance between the stereogram and the eyes, but at the same time try not to lose the found picture. The next actions are turning the head up and down and left and right while holding the seen image. It might not work the first time. However, over time, the eyes will get used to it and the visible object will be recognized from different angles. Stereograms are very useful for training binocularity, as well as for relieving tension from the visual apparatus. Especially such an exercise will be useful for people who work at a computer. Stereograms can not be printed out, but viewed directly from the monitor. It is only necessary to set its optimal brightness.

In addition to these exercises, you can perform general gymnastics for the eyes, which helps with fatigue and to improve visual acuity. There are also many such methods. Before performing them, consult an ophthalmologist.

A person with binocular (stereoscopic) vision can fully navigate in space. It is possible to distinguish objects and objects by shape even in the presence of monocular vision. However, it is possible to determine the distance between objects only with the formed stereoscopic perception. Any pathologies that lead to a violation of binocularity must be treated on time, especially if they occur in childhood, when vision is just being formed.

The shape, size and distance to the object, for example, due to binocular vision (the number of eyes can be more than 2, such as wasps - two compound eyes and three simple eyes (eye), scorpions - 3-6 pairs of eyes) or other types vision.

Functions of the organs of vision

The functions of the organs of vision include:

• central or objective vision
• stereoscopic vision
• peripheral vision
• color vision
• light perception

binocular vision

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See what "Stereoscopic vision" is in other dictionaries:

Spatial (volumetric) vision ... Physical Encyclopedia

stereoscopic vision- Perceptual perception of three-dimensional objects, due to the combination of two points of view (eyes) and the presence of visual channels that transmit information to the brain. Psychology. A Ya. Dictionary reference book / Per. from English. K. S. Tkachenko. M .: FAIR PRESS. ... ... Great Psychological Encyclopedia

stereoscopic vision- erdvinis regėjimas statusas T sritis fizika atitikmenys: angl. stereoscopic vision vok. räumliches Sehen, n; stereoskopisches Sehen, n; Tiefensehen, n rus. spatial vision, n; stereoscopic vision, n pranc. vision stereoscopique, f … Fizikos terminų žodynas

STEREOSCOPIC VISION- See vision, stereoscopic... Explanatory Dictionary of Psychology

Global stereoscopic vision- The process underlying the perception of stereograms formed by random configurations of points, requiring a complete, or global, comparison of disparate elements common to both halves of a stereopair ... Psychology of sensations: a glossary

Pathways of the visual analyzer 1 Left half of the visual field, 2 Right half of the visual field, 3 Eye, 4 Retina, 5 Optic nerves, 6 Oculomotor nerve, 7 Chiasma, 8 Optic tract, 9 Lateral geniculate body, 10 ... ... Wikipedia

Main article: Visual system Optical illusion: the straw seems to be broken ... Wikipedia

A spatial image, which, when viewed, appears to be visually voluminous (three-dimensional), conveying the shape of the depicted objects, the nature of their surface (shine, texture), relative position in space, and other external objects. signs... ... Physical Encyclopedia

I Vision (visio, visus) is the physiological process of perceiving the size, shape and color of objects, as well as their relative position and distance between them; the source of visual perception is the light emitted or reflected from objects ... ... Medical Encyclopedia

The ability to simultaneously clearly see an image of an object with both eyes; in this case, the person sees one image of the object he is looking at. Binocular vision is not innate, but develops in the first few months of life. medical terms

Binocular vision is the normal nature of human vision, it allows us to perceive the world around us in volume. We can estimate the size and shape of the object, its relief, the distance to the object, their relationship to each other. Stereoscopic vision is one of the highest manifestations of binocularity, allowing you to see in three dimensions.

Binocularity allows us to form visible objects into a single visual image. We see the picture with the left and right eyes separately.

In this article

In normal vision, the image falls on the same (corresponding) areas of the retina of both eyes, and then is formed into a single whole already in the cerebral cortex, which is called the fusion reflex. This is a reflex mechanism of binocular vision, responsible for the merging of two pictures into one. In case of violation of binocularity, the image is projected onto mismatched points, as a result of which the brain cannot combine them into one. Diplopia (double vision) occurs. This is easy to verify if, when looking at any object, lightly press on the lower or upper eyelid, the eyes will immediately begin to double.

The development of stereoscopic vision in a child

A child within a few weeks after birth is not yet able to fix his gaze on an object, since his eye muscles are mismatched and cannot make synchronous movements. Because of this, we observe infantile strabismus. The nature of vision after birth is monocular - the baby sees with only one eye, and then monocular alternating - either with the left or with the right eye. But by two months of life, a reflex of fixing an object should form. During this period, light excitations are already transmitted to the cerebral cortex, a connection arises between the yellow spots of the retina and the two images merge into one - the fusion reflex is triggered, without which stereoscopic binocular vision is impossible. In addition, during normal development, convergence should appear (convergence of visual axes to fix nearby objects). This is confirmation that accommodation is developing - the ability of the eyes to see at different distances.

At two or three months, the baby is actively mastering the near space - an important stage for the formation of binocular vision. At this time, he does not yet have "stereo" vision and sees objects only in two dimensions - in width and height, and can get an idea of ​​\u200b\u200bdepth only through touch. So he gets the first idea about the volume of objects.
At 4-5 months, the child has a dynamic development of the grasping reflex. The kid determines the direction of movement, but it is still difficult for him to estimate the distance, as well as the volume: he tries to grab sunbeams, glare from light sources, moving shadows with his hand.

After six months, the stage of active development of distant space begins, when the baby begins to actively crawl. At the same time, the child already better estimates the distance to the object to which he is heading, there comes an understanding that you can fall from the edge of the bed. He is able to reach a variety of things, assess their size, relief. This is a period of rapid development of stereoscopic and generally binocular vision. At this time, it is necessary to give him objects of various shapes, from various materials for games, fill the nursery with various geometric toys: cubes, balls that can be rolled.

Exploring objects of various shapes and materials, the baby forms stereoscopic vision, his own idea of ​​the world around him. The common game of rolling a ball between an adult and a child is a great example of how he learns to judge distance, one of the important features of binocular vision. Completely the formation of stereo vision is completed by about eight years of age.

Strabismus is the cause of the loss of stereoscopic vision.

Strabismus often occurs in children and indicates a clear violation of stereo vision. Professor R. Sachsenweger, as a result of many years of observation, deduced two terms:

• "stereoamaurosis" - the complete absence of stereoscopicity;
• "Stereoamblyopia" - defective development of stereoscopic vision.

The occurrence of strabismus in a child destroys his binocular and stereoscopic vision. At the same time, it should be noted that it is possible to restore stereo vision only in that part of children with concomitant strabismus; with a congenital or early onset disease, it is not possible to restore full-fledged three-dimensional vision.
Restoration of stereoscopicity is carried out at the last stage of strabismus treatment, when fusion reflexes and normal planar binocular vision are developed. In this case, the final results depend on the visual acuity of both eyes, the difference between them in diopters, the angle of strabismus. Also, the threshold limit of deep vision is affected by the timing of the onset of strabismus (it is important at what stage of formation the visual process was) and the degree of aniseikonia - a violation in which images of different sizes are formed on the retinas of both eyes. If this difference is more than 5%, then the quality of depth vision is very low.

That is why it is so important to carefully observe the process of development of the child's visual mechanism, to know what he should be able to do at a certain period of life. Developed strabismus, amblyopia can lead to a complete loss of binocular vision, including stereofunction. Most often, this disease develops in the period up to three years. In addition, as strabismus can be the cause of amblyopia, and vice versa, its consequence. With amblyopia (lazy eye syndrome), a child observes the world with only one eye, having monocularity. Naturally, volumetric vision is absent in this case. These pathologies are also dangerous because, in a neglected state, binocular functions can completely atrophy.

What prevents the lack of full-fledged binocular and stereoscopic vision?

Lack of stereo vision limits the ability to work in many areas, and also threatens with dangerous consequences for both the employee and others. Here are some examples.
Medical worker. Imagine a surgeon performing an abdominal operation. If he is not able to estimate the size of the organ he operates, as well as the distance to it? A dentist who misses a tooth? In the absence of normal binocular and even more so stereo vision in medicine, it is forbidden to work in some specialties.

Athlete in many disciplines. As a rule, almost all sports require absolutely perfect stereoscopic binocular vision. The athlete needs to constantly evaluate the distance to other players, the ball, the puck of the shuttlecock, the height of the bar when jumping, as well as the size of objects in order to visually assess how far they are. Good binocularity is not needed, for example, in chess, but in general, the results in sports depend on it.

Drivers of various types of transport, as well as pilots, the military, undergo a mandatory test of binocular vision before entering a military school and being hired. A driver who cannot judge the distance to other vehicles is a potential source of danger on the road. The lack of stereofunction of vision also prevents you from working in many other professions: a videographer, a hunter, an artist, etc.

Parents need to closely monitor the development of his visual functions from the very birth of a child. persistent infantile strabismus is already a reason to urgently visit an ophthalmologist. In addition, do not ignore the mandatory vision checks at certain stages of the baby's development: 1 month, 3 months, six months and a year. The doctor will detect abnormalities, if present, and prescribe the appropriate therapy or treatment. Thus, no time will be lost. Often, it is neglected diseases that cause the loss of visual functions.