Binocular vision - research, treatment of disorders. Binocular vision status: how to check? Strabismus and its consequences

The eye is the most difficult optical system, for the normal functioning of which the coordinated work of all its parts is necessary.

Man with healthy eyes sees not only the outlines of surrounding objects.

But he also distinguishes what color they are, evaluates their size, shape, determines their relative position in space and perceives their volume.

One of the mechanisms that provides three-dimensional vision of the surrounding world is binocular vision.

What it is?

Binocular vision- the ability of a person to see with both eyes simultaneously in such a way that the images received by each eye separately ultimately merge into one.

It is thanks to the mechanism of binocular vision that we can easily determine at what distance objects are located, do not lose orientation in space, and also see three-dimensional objects in three dimensions at once.

In addition, if this mechanism is not broken, we see not only in front of us, but also on the sides, above and below.

This stereoscopic vision starts to appear from infancy: Already at the age of two years, a child is able to see a three-dimensional image.

The formation of binocularity ends only by the age of 14-16 years.

What is necessary to develop binocular vision?

Not all people can develop binocular vision. For its full development, the following conditions must be simultaneously met:

• equal vision in the right and left eyes (no less than 0.5 dioptre);
• the same shape of the cornea in both eyes (the degree of refraction must be the same);
• symmetry of the eyeballs (due to injuries, infectious diseases or the growth of the tumor, the position of the eyeballs may change);
• proper functioning of the eye muscles;
• correct functioning of the central and peripheral nervous system;
• the same projection of the image on the retina of both eyes;
• normal operation of each optical medium;
• absence pathological changes retina, lens and cornea, optic nerves.

If one of the conditions is violated, vision cannot be fully binocular.

How it works?

It is believed that binocular vision occurs due to the work of the cerebral cortex. It is this part of the brain that seems to connect the two images received from both eyes into a single whole.

Each point of the retina of the eye has an identical (corresponding) point on the retina of the second eye. Images of the same size and shape are projected onto corresponding points on the retina.

If images are projected onto a disparate point, the connection of the two images cannot occur. Then the person sees the surrounding objects as double.

How to check binocular vision?

There are many methods for determining binocular vision. You can test your vision without special devices.

Sokolov's experience

The patient brings the rolled-up form to the eye. spyglass a piece of paper (or any other hollow object that resembles a tube) and looks through the hole at any object in the distance.

Next, the subject brings his palm to the second eye at the same distance as the end of the folded sheet. If binocular vision is not impaired, a person will see a hole in his palm through which the objects in question will be visible.

Kalf's Experience

The patient is given two pencils, one of which he holds horizontally and the other vertically. The patient’s task is to hit the horizontal pencil with a vertical pencil.

If vision is not impaired, the subject copes with the task with ease, since binocular vision helps to correctly assess the position of objects in space and determine the distance between them.

Reading experience

The patient is given a piece of paper with printed text and a pencil. He should hold the pencil at a distance of 2-3 centimeters from the tip of his nose and try to read the text without moving his head, hand or moving the piece of paper with the text.

If binocular vision is formed correctly, the pencil will not prevent the subject from reading the entire written text. This occurs by merging two images obtained from both eyes.

Four point test

This verification method is the most accurate. The doctor places objects of different colors in front of the patient: red, white and two green. Next, the patient is asked to put on special glasses.

One lens of the glasses is red and the other is green. If the mechanism of binocular vision is not impaired, a person will see all four objects.

Red and green will not change color, but white will look like red-green, since the finished image is formed by both eyes at once.

If vision is monocular, then the subject will see only the object whose color matches the color of the lens placed on the dominant eye. The white object will also be colored the same color as the lens of the dominant eye.

Binocular vision can also be tested using special ophthalmic devices:

• slit lamp;
• ophthalmoscope;
• perimeter;
• autofluorofractometer;
• monobinoscope.

Causes of binocular vision impairment

There are many known causes of impaired binocular vision. It is very important to install the real reason pathology, because only in this case is adequate and effective treatment possible.

Here are the main reasons:

• anisometropia (different eye refraction);
• various lesions of the eye muscles;
• disruption of muscle innervation;
• pathology of the bones of the orbit;
• pathology of the orbital cavity;
• brain stem diseases;
• infectious diseases of the eyes, surrounding tissues, and brain;
• poisoning with toxic substances;
• tumor diseases of the organs of vision and brain.

Binocular vision disorders

The most clinically significant and common disease accompanied by impaired binocular vision is strabismus.

Strabismus is a condition in which one eye (sometimes both) deviates in any direction, and the axes of vision of the eyes no longer coincide.

Patients suffering from strabismus may complain of the following symptoms:

• double vision;
• the need to tilt the head to the side from which the eye muscle is affected;
• dizziness;
• nausea;
• severe headaches;
• impaired mobility of the affected eyeball.

Strabismus can be either hereditary or acquired. Here are the main reasons why it develops:

• ametropia;
• previous injuries;
• severe infectious diseases;
• psychiatric diseases;
• pathologies of the central nervous system;
• malformations of the eye muscles.

Treatment of strabismus

Strabismus, accompanied by impaired binocular vision, causes significant discomfort to the patient and reduces the quality of life.

Medicine offers several effective ways to treat this condition. The method of therapy should be selected only by a doctor, taking into account the characteristics of the patient’s disease and its severity:

Binocular vision is provided by two eyes. A single three-dimensional visual image is formed, which is obtained by merging two images from both eyes into one. This gives depth of perception and volume.

Benefits of Binocular Vision

Only thanks to binocular vision can a person fully perceive the surrounding reality and determine the distances between objects. This is called stereoscopic vision. Monocular vision is provided by one eye. It gives an idea of ​​the width, height and shape of an object, but does not allow one to judge how objects are located among themselves in space.

Thanks to binocular vision, the field of view expands, visual images are more clearly perceived, that is, visual acuity actually increases. For representatives of some professions (pilots, machinists, drivers, surgeons), full binocular vision is a prerequisite for professional suitability.

Mechanism of binocular vision

Binocular vision provides fusion reflex- the ability to compare two images from both retinas in the cerebral cortex into one stereoscopic picture.

In order to obtain a single image of an object, it is necessary that the images obtained on the image correspond to each other in shape and size. It is also necessary that they fall on identical, corresponding areas of the retina. Each point on the surface of one retina corresponds to a corresponding point in the other. Non-identical points are a set of asymmetrical areas, which are called disparate. In the case when the image of an object falls on the disparate points of the retina, image merging will not occur. Then double vision occurs.

Newborns lack coordinated movements of the eyeballs. They lack binocular vision. By 6-8 weeks, babies can fixate an object with both eyes. Stable binocular fixation is observed at 3-4 months. By 5-6 months, the fusion reflex is formed. Full-fledged binocular vision finishes forming by the age of 12, therefore (impaired binocular vision) is considered as a pathology of preschool age.

In order to have normal binocular vision, certain conditions are needed:

• ability to fusion (bifoveal fusion);
• coordinated work of the oculomotor muscles, which ensures parallel position of the eyes when looking at a distance and convergence (corresponding reduction of the visual axes) when looking close, as well as associated correct movements of the eyeballs in the direction of the object in question;
• position of the eyes in one horizontal frontal plane. After injury, inflammation in the orbital area, or in the presence of neoplasms, one eye may shift, which leads to disruption of the symmetry of the combination of visual fields;
• visual acuity of both eyes sufficient to form a clear image on the retina (at least 0.3-0.4).

If the images on the retina of both eyes are equal in size, it is called iseikonia. When the two eyes are different (), images of different sizes are noted. In order to preserve binocular vision, the degree of anisometropia is allowed no more than 2.0-3.0 diopters. This should be taken into account when selecting glasses, because if there is a very large difference between the corrective lenses, the patient will be able to have high visual acuity with glasses, but he will not have binocular vision.

An important condition for binocular vision is the transparency of the optical media of the eye (, and), as well as the absence of pathological changes in optic nerve, retina and higher located sections visual analyzer, such as the chiasma, optic tract, subcortical centers and cortex cerebral hemispheres brain.

Methods for determining binocular vision

Binocular vision can be tested in several ways:

• Sokolov’s experiment is called the “hole in the palm” method. A tube (for example, a folded piece of paper) is placed on the patient's eye. Through it he looks into the distance. The person places his or her palm against the far end of the tube. If he has normal binocular vision, then due to the superimposition of images, it seems that there is a hole in the center of the palm through which the picture is viewed. But he actually sees her through the tube.
• Reading test with a pencil. A person is given a text to read and a pencil is placed a few centimeters from his nose. It covers some of the letters. If you have binocular vision, you can read by superimposing images from both eyes. In this case, there is no need to change the position of the head, because the letters that the pencil buries for one eye are clearly visible to the other eye.
• Kalfa method, or miss test. Conduct a study of binocular function using two pencils or knitting needles. The subject holds a pencil horizontally outstretched arm and tries to hit the tip of the second pencil, which the knitting needles are in vertical position. If his binocular vision is not impaired, then this is not difficult to do. When it is absent, the person misses. This is easy to verify if the experiment is carried out with one eye closed.
• The four-point color test allows you to more accurately determine binocular vision. The method is based on the principle of separating the visual fields of the left and right eyes. This is achieved using color filters. Take two green, one white and one red objects. The patient puts on glasses with green and red lenses. If binocular vision is available, then a person sees green and red objects, and a colorless object will be colored red-green, since it is perceived by both the left and right eyes. If there is a pronounced dominant eye, the colorless circle will be colored in the color of the glass that is placed in front of it. If vision is simultaneous, in which the higher visual centers perceive impulses from one eye, then from the other eye, the subject sees 5 circles. When there is monocular vision, then, depending on which eye takes part in vision, a person will see only those objects whose color will match the filter of that eye, as well as a colorless object that was colorless.

Strabismus and binocular vision

With strabismus, binocular vision is almost always absent, because one eye deviates in one direction and the visual axes on the object in question do not converge. One of the main goals of strabismus treatment is to restore binocular vision. By whether binocular vision is absent or not, one can distinguish imaginary, apparent, strabismus from real, and from heterophoria (hidden strabismus).

The optical axis passes through the center of the cornea and the nodal point of the eye. The visual axis goes from the central fovea of ​​the spot through the nodal point to the object that is being viewed. There is a small angle between them (3-4°). With imaginary strabismus, the discrepancy between the visual and optical axes is very large (in some cases 10°). For this reason, the centers of the corneas of both eyes shift in one direction or another. This creates the false impression of squint. Its difference from true strabismus is preserved binocular vision. Imaginary strabismus does not need correction.

Hidden strabismus is manifested by the fact that one eye deviates at the moment when a person does not fix his gaze on any object. With heterophoria, there is an adjustment movement of the eyes. If the subject fixes his gaze on any object and covers one eye with his palm, then this eyeball, in the presence of hidden strabismus, deviates to the side. When he removes his hand, then, if the patient has binocular vision, this eye will make an adjustment movement. If heterotopia is present, there is no need for treatment.

You can find many tests on the Internet to check visual acuity or color vision. Just download standard table Sivtseva-Golovin and find out if you have any violations visual functions. There are online tests to test binocular vision. How do they work and can they replace hardware research methods?

Binocular vision: what is it?

Binocular vision is the ability to see three-dimensionally. The fusion reflex provides this function of the visual analyzer. It works as follows: the brain receives two images from both retinas and combines them into a complete picture. Stereoscopic vision is possible under certain conditions. A person must have good eyesight, eyeballs it must move synchronously, in concert. There are other conditions that ensure stereo vision works. In most cases, they relate to the presence or absence of diseases, ocular and non-ophthalmological. When binocular vision is impaired, a person cannot see normally with both eyes. One partially or completely falls out of the visual process, and without stereo vision it is difficult to navigate in space, since a person cannot determine the distance between visible objects.

Determination of binocular vision online

You can determine whether you have binocular vision yourself at home. This is done using a series of simple experiments or computer programs. An online binocular vision test will give you the opportunity to find out whether or not you have problems with visual functions.

How to pass the binocular vision test?

To do this, you need to upload a picture to the server, for example, an apple. It should be large (about 15 cm in diameter) and located in the center of the monitor. Adjust the brightness of the image. The monitor should not be dim or too bright. You should place it at a distance of 40-45 cm from the monitor. The image is at eye level. Next, you need to extend your finger up and keep it on the same visual axis with the object (apple). Look at the apple. You should be able to see the object between your two fingers. At the same time, your hands and fingers will appear transparent. After this, look at your finger. You will notice that the apple has split in half.

Next step- look at the apple and close your left eye. You should see a finger to the left of the object. When you close your right eye, you will see a finger to the right of the apple.

Evaluation of results

The test is deciphered very simply. If you see all the images described above (a forked apple and a forked finger), then your stereoscopic vision function is working. If there are violations, you will see other images:

• one finger is larger than the second;
• You only ever see one finger;
• fingers disappear and appear, and you cannot focus normally;
• the left finger covers the apple, and the right finger is located very far from it.

What to do if the results are negative?

All these signs indicate that one eye is dominant in you. This is not a reason to panic. You may not be able to pass the online vision test the first time. In addition, there are various exercises to train your vision. However, it is better to consult an ophthalmologist for an examination. The test can only give a rough idea of ​​how spatial vision works. In the presence of pathologies, for example, with strabismus, an examination for special devices. One such device is a sign projector.

Wars test. Checking on the sign projector

A sign projector is a device used by ophthalmologists to determine the degree of visual impairment. A projector shows signs on the wall, and a person looks at them through green and red lenses. There are only 5 signs: two green, two red and white. In the presence of binocular vision, the subject sees four figures, if the vision is simultaneous (that is, one and then the second eye works alternately) - 5 figures, and with monocular vision (one eye works) - the patient distinguishes either two red or three green figures.

Advantages of the technique

The sign projector experiment is also called the four-point experiment. It is the most common in ophthalmology, as it allows you to accurately determine the nature of vision. The results of the study can only be deciphered by a doctor. The advantage of this technique is its accuracy. However, it is not suitable for testing vision in very young patients who cannot tell themselves what they see. They are examined using other instruments.

Binocular disturbances can lead to various diseases. In most cases, the prognosis for treatment is favorable. It is important to start treating any disease on time and systematically

Normally, every person perceives the world two eyes at the same time. The images received by the right and left eyes merge in the brain into a single image, and we get a three-dimensional, stereoscopic picture. If the two images do not merge, they speak of impaired binocular vision.

Binocular vision can only exist under certain conditions. The brain will merge images together if both eyes have the same visual acuity, the shape of the cornea matches, the eyeballs are symmetrical, and eye muscles work correctly. Important has the correct functioning of the nervous system, the absence pathological disorders in the retina, lens, optic nerve.

Is it possible to test binocular vision at home?

If you suspect you have a binocular vision disorder, then you need to contact an ophthalmologist, who will conduct a thorough diagnosis and be able to accurately determine the presence or absence of this problem.
Methods for testing binocular vision at home can be used as a preliminary diagnosis; you can conduct the test yourself. The most popular methods of self-diagnosis are the Sokolov method, known as the “hole in the palm”, the Kalf method, the four-point color test and reading with a pencil.
It should be borne in mind that all these methods of testing vision for binocularity are of an auxiliary nature and do not replace consultation with a specialist.

How to test binocular vision using the Sokolov method?

To test binocular vision using this method, You will need a tube with a through hole: this could be a bushing from food foil or just a folded sheet of cardboard. Place the tube on one eye and look through it into the distance. Place the palm of your free hand in front of your other eye, aligning back side palms and the far edge of the tube. If you do not have problems with binocular vision, then you will see a “hole in the palm” - a round hole through which the distant image is visible. This optical illusion This is explained by the fact that with normal binocular vision, two images overlap: your palm and the image that you see through the hole in the tube. The absence of a “hole in the palm” indicates monocular vision, in which the brain perceives information from only one eye. If the “hole” is present, but not located in the center of the palm, then this may indicate simultaneous vision, in which the brain receives information from both visual organs, but does not connect the resulting images together.
When conducting the Sokolov test, it is important to examine distant objects through the tube, located at least 4-5 meters from you. Alternatively, you can look out the window or, while in one room, look at objects in another.

Checking binocular vision using the Kalf method

Another simple one, but effective method check binocular vision - Kalf method. To carry it out you will need two pencils, two knitting needles or other objects of a similar shape with sharp edges. Take them in different hands. Place one pencil vertically and the other horizontally, then try to connect them so that you get a right angle. With monocular vision, patients usually miss the mark and fail to achieve the correct connection even after several attempts. If stereoscopic vision is normal, such a test will not cause difficulties.

Reading with a pencil

You can check for binocular vision using regular reading. To conduct a self-diagnosis, you will need any book and pencil. While reading, place the pencil at a distance of 15 cm from the book and a few centimeters from your nose - so that it covers part of the text for you.

If your vision is binocular, you can still easily read the entire text because the brain combines the images received from both eyes and produces an overall picture. If you cannot read part of the text, then the brain processes only information received from one visual organ, indicating monocular vision.

Four-point color test - an option for home vision testing

Typically, a four-point color test is carried out in a clinical setting using a special apparatus. The operating principle of the device is based on separating the visual fields of the right and left eyes using multi-colored filters. The patient is put on special glasses: a red filter is placed in front of the right eye, and a green filter is placed in front of the left eye. After this, the patient looks into the holes of the device. Depending on the color of the filters, the doctor makes a conclusion about the presence of binocular, monocular or simultaneous vision.

You can conduct a similar test at home if you have red-green glasses. To carry out the test you will need red, green and white. Place them one to five meters from your eyes and look at them through glasses with colored lenses. If binocular vision is not impaired, colored objects will have the color they originally had. A white object in your perception will become half red and half green. With monocular vision, all objects are “colored” in the color of the lens of the dominant eye.

Other ways to test binocular vision at home

There are several more simple ways which will help you determine at home whether you or your child have binocular vision.
For the test, you need to select a point in the distance that you will look at. Focus your gaze on it and begin to press your finger on one eye through the eyelid, slightly lifting it up. If everything is normal with binocular vision, then at the moment of pressure on the eye the image begins to double in the vertical plane. The visual image is divided into two pictures, one of which moves upward. When the pressure on the eye stops, you again see a single visual image. If double vision does not appear during this test, then with a high degree of probability it can be assumed that the person has monocular vision. In this case, the brain perceives information precisely from the eye that was not under pressure. If the image also does not double, but when pressure is applied to the eye, a single image is displaced, this means that the brain is processing information from the displaced eye.

The second method is no less simple. If you are testing a child's binocular vision, ask him to look at a selected point in the distance, and then cover his eye with his palm. If the fixed point has shifted, then most likely the vision is monocular in nature, and the working eye is the eye that was covered with the palm. If during the experiment the fixed point disappeared altogether, this also indicates monocular vision, and means that the uncovered eye does not see at all.

Binocular vision testing should be performed by a doctor

An independent vision test for binocularity at home will help identify possible disturbances in the functioning of the eyes and visual perception. However, to determine how binocular vision is developed in you or your child, put accurate diagnosis, appoint adequate treatment Only an ophthalmologist can. The specialist has a wide range of instruments and tests in his arsenal that will help with 100% probability to give an opinion on the state of your binocular vision.

Binocular vision testing can be done different methods, among which the generally accepted method is research using a 4-point color test (test with a color device).

The subject observes 4 multi-colored circles (2 green, white and red), glowing through filter glasses (with one red and one green glass). The color of the circles and lenses are selected in such a way that one circle is visible only with one eye, two circles - only with the second, and one circle (white) is visible with both eyes.

The patient sits at a distance of 5 m from a direct and strong light source. He puts on filter glasses: the right eye is covered with red glass, and the left eye with green glass. Before starting diagnostic procedures, check the quality of the filters. To do this, cover the eyes one by one with a special shield, and the patient first sees two red circles with his right eye, and then three green circles with his left eye. The main examination is carried out at the same time open eyes.

There are three types of examination results: binocular (normal), simultaneous and monocular vision.

Sokolov's method (1901)

The method is that the patient is asked to look into a tube with one eye (for example, a sheet facing into a tube), and a palm is applied to its end on the side of the open eye. In the presence of binocular vision, the impression of a “hole in the palm” is created, through which the picture that is visible through the tube is perceived. This is because the picture seen through the hole in the tube is superimposed on the image of the palm in the second eye.

With simultaneous vision, the “hole” does not coincide with the center of the palm, and with monocular vision, the “hole in the palm” phenomenon does not appear.

The experiment with two pencils (they can be replaced with ordinary sticks or felt-tip pens) is of approximate value. The patient should try to align the tip of his pencil with the top of the pencil in the doctor's hands so that a clearly straight line is formed. A person with binocular vision easily performs tasks with both eyes open and misses when one eye is closed. In the absence of binocular vision, misses are noted.

Other, more complex methods (prism test, Bogolin striped glass test) are used.

Strabismus according to the Hirshberg method

The magnitude of the strabismus angle is simply and quickly determined by the Hirshberg method: a beam of light is directed into the eyes of the subject and the location of light reflexes on the cornea is compared.

The reflex is recorded in the eye and observed near the center of the pupil, or coincides with it, and in the eye that squints, it is determined in the place corresponding to the deviation of the visual line.

One millimeter of its displacement on the cornea corresponds to a strabismus angle of 7 degrees. The larger this angle, the further the light reflex moves from the center of the cornea. So, if the reflex is located at the edge of the pupil with its average width of 3-3.5 mm, then the angle of strabismus is 15 degrees.

A wide pupil makes it difficult precise definition the distance between the light reflex and the center of the cornea. More accurately, the angle of strabismus is measured on the perimeter (Golovin’s method), on a synoptophore, using a test with covered prisms.

Subjective method for determining binocular vision

To determine the level of light refraction in the eyes using a subjective method, you need a set of lenses, a trial spectacle frame and a table for determining visual acuity.

The subjective method for determining refraction consists of two stages:

• determination of visual acuity;
• applying to a rimmed eye optical lenses(first +0.5 D and then -0.5 D).

With emmetropia, positive glass worsens Visus, and negative glass first worsens it, and then does not affect it, since accommodation is activated. With hypermetropia, “+” glass improves Visus, and “-” glass first worsens, and then, with a large accommodation stress, it is not displayed on Visus.

In young patients with visual acuity equal to one, two types of refraction can be assumed: emmetropia (Em) and mild hypermetropia (H) with the participation of accommodation.

In elderly patients with visual acuity of “one”, only one type of refraction can be assumed – accommodation is weakened due to age.

When visual acuity is less than one, two types of refraction can be assumed: hypermetropia ( high degree, accommodation cannot help) and myopia (M). In hypermetropia, a positive glass (+0.5 D) improves Visus, and a negative glass (-0.5 D) worsens Visus. In myopia, a positive glass worsens visual acuity, and a negative glass improves it.

Astigmatism ( different kinds refraction in different meridians of one eye) is corrected by cylindrical and sphero-cylindrical lenses.

When determining the degree of ametropia, the glass changes for the better. Visus with it (1.0).

Moreover, with hyperopia, refraction determines the largest positive glass, with which the patient sees better, and with myopia, the smaller negative glass, with which the patient sees better.

The different type or degree of refraction of both eyes is called anisometropia. Anisometropia up to 2.0-3.0 D in adults and up to 5.0 D in children is considered tolerable.

Objective methods for determining binocular vision

Skiascopy (shadow test), or retinoscopy – objective method determination of eye refraction. To carry out the method you need: a light source – a table lamp; mirror ophthalmoscope or skiascope (concave or flat mirror with a hole in the middle); skiascopic rulers (this is a set of cleaning or diverging lenses from 0.5 D-1.0 D in ascending order).

The study is carried out in a dark room, the light source is located to the left and slightly behind the patient. The doctor sits 1 m away from him and directs the light reflected from the skiascope into the eye being examined. In this case, a light reflex is observed in the pupils.

By slightly rotating the handle of the glass, the reflected beam is moved up and down or left and right, and through the opening of the skiascope, the movement of the skiascope reflex in the pupils is observed.

Thus, skiascopy consists of 3 points: obtaining a red reflex; obtaining a shadow, the movement of which depends on the type of mirror, the distance from which it is examined, and the type and degree of refraction; neutralizing the shadow using a skiascopic ruler.

There are 3 possible variants of the skiascopic reflex (shadows against the background of the red reflex):

• the skiascopic reflex moves in accordance with the movement of the mirror;
• it moves opposite to the movement of the mirror;
• there is no shadow against the background of the red reflex.

If the movement of the reflex and the mirror coincide, we can talk about hypermetropic vision, emetropic or myopic to one diopter.

The second option for moving the skiascopic reflex indicates myopia of more than one diopter.

Only with the third variant of the reflex movement do they conclude that myopia is one diopter and measurements are stopped at this point.

When examining an astigmatic eye, skiascopy is performed in two main meridians. Clinical refraction is calculated for each meridian separately.

In other words, binocular vision can be examined different ways, everything directly depends on the severity of the symptoms, on the patient’s complaints and on the professionalism of the doctor. Remember, strabismus can only be corrected by early stages development and this will take a lot of time.