PARADOXES OF HUMAN VISION AND THEIR ELIMINATION USING THE LAWS OF PHYSICS

Visual acuity

- the ability of the eye to distinguish small details of an object from a certain distance. Vision in different species of animals varies greatly in acuity, color perception and other parameters. Visual acuity changes with changes in illumination. In people, visual acuity changes with age, and it can be different for each eye, due to hereditary characteristics or acquired defects (myopia, farsightedness, astigmatism, cataracts and other deviations from the norm).

With the same shape of the eyeball and lens, the same refractive power of the visual system (eye), the maximum visual acuity is due to the difference in the distance between the retinal receptors (rods and cones).

[edit] Introduction

To test vision (visiometry), special tables are used, which are viewed from a certain distance under standardized lighting:

For adults, the Sivtsev (letter) and Golovin (with Landolt rings) tables are used,
For children - Orlova’s table (with pictures - symbols and silhouettes).
The first of the tables developed was the Snellen table, named after its creator, the Dutch ophthalmologist Hermann Snellen (proposed in 1862).

The tables are presented using a Roth apparatus (an illuminator named after a Berlin doctor - the creator of a system of uniform illumination for visimetry).

The influence of gadgets on eye health

How else does prolonged exposure to a screen affect vision? First of all, severe drying of the mucous membrane occurs. Normally, a person blinks approximately 11-12 times per minute. When looking intensely at the monitor, blinking occurs 5-6 times per minute, that is, the norm is halved. At the same time, the tear film dries out, the eye tends to be moistened from the inside, and a rush of blood occurs to the vessels of the conjunctiva - the transparent membrane covering the top of the eyeball. The organs of vision turn red, there is a feeling of dryness and irritation. But today it is difficult to imagine the work of most enterprises without the use of computer technology. In addition, some professions require spending quite a long time in front of a monitor, and the visual organs experience significant overload. For example, this is the work of programmers or system administrators.

In this situation, preventive measures should be taken to periodically give the eyes a rest, as well as use moisturizing drops.

[edit] Units of measurement of visual acuity

→ Resolution (optics)

Visual acuity is determined using the Snellen formula:

V = d/D,

where V( Visus

) - visual acuity, d - the distance from which the signs of a given row of the table are seen by the subject, D - the distance from which the eye with normal visual acuity sees.

It is accepted that the human eye with visual acuity equal to one - v = 1.0) distinguishes two points, the angular distance between which is equal to one arc minute or 1″ = 1/60° at a distance, for example, 5 m. Where does visual acuity come from? v

, is directly proportional to viewing distance.

At viewing distance R

= 5 m, then an eye with visual acuity v = 1.0 will distinguish two points, the distance between which x = 2×5*tg(α/2) = 0.00145 m = 1.45 mm.
This is the main criterion for determining the thickness of the stroke, the distance between adjacent strokes in the letters on the table and the size of the letters themselves (see Fig. 2, where: height of letter B
= 5 × 1.45 = 7.25 mm).

If visual acuity is poor, adjacent strokes are not distinguished, so areas of black color can exchange with white ones. Yes, in the letter Ш

instead of 3 strokes, a person will see 2, that is, he will see an inverted

letter P.

The letters in the table are made square specifically to make it more difficult to identify by its blurred silhouette. This is done to conduct acuity testing with greater clarity in assessing visual acuity.[1][2]

The decimal table proposed in 1875 by Monoyer was adopted as a standardized series of visual acuity values. This table consists of 10 rows of letters, the top of them is visible to the normal eye at an angle of 5 minutes at a distance of 50 m, the bottom - at the same angle at a distance of 5 m. The sizes of the characters change every 0.1 of visual acuity - from 0.1 to 1.0; each row is visible at an angle of 5 minutes at different distances. Subsequently, the table was expanded to include measured visual acuity values from 0.05 to 2.0. Maximum visual acuity (2.0) corresponds to the angle of observation of the gap and the width of the Landolt ring equal to 0.5 arc minutes.

↑ We evaluate how well you see at close range

To evaluate how well you can see at close range, we use a different chart. This chart is shown at life size, and unlike the chart used to test distance vision, the numbers next to each line do not refer to any distance.

The chart is held sixteen inches (40 cm) from the eyes and the numbers refer to the corresponding visual acuity. In other words, on this small chart it should be just as difficult to see the number 20 line from a distance of sixteen inches (40 cm) as on a large chart line 20 from a distance of twenty feet (6 m) - provided, of course, that you have healthy eyes or excellent glasses. If you can read the letters on the last line of the near vision chart, you're even closer to achieving clear vision—but not there yet.

[edit] Resolution of the visual system

For example, from the condition of the presence of 6 million cones in the macula (in humans), on an area of 6 mm², which perceive color, it is possible, on the basis of known data, to show that one cone is not able to provide the necessary information about the color that reaches the retina from the object point . It is known that the resolving error of a normal eye when reading from a distance of 250 mm is in the range of 0.072 – 0.200 mm and depending on the illumination and the individual, we will take the average statistical value of the estimates of the resolving power of optical instruments, the average groups of adults undergoing testing (vehicle drivers, military personnel etc.) with an indicator of 0.0896 mm (with visual acuity of 0.8).

The number of photoreceptors in the zone of best vision (macula) in the center of the retina is ~6 million, they are located on an area of ~5.6‒6 mm². Thus, the optical image contains 1,000,000 (1 MP) different color dots; the distance between the points of the same name (photoreceptors - “pixels”) is very small (a dense packing of cones in the macula, which can be separated by rods with a cylindrical membrane size of about 2 microns). During the day, visual perception is carried out as a result of focusing image elements (dots) on “receptor mosaic blocks”, consisting of cones, in the form of circles of confusion (the side of a square “cell” measuring 7 microns), which the eye clearly sees. This is the basic principle for constructing visual acuity testing tables.

Let's consider two options:

1) For people with visual acuity = 1.0, the distance between two points (lines) = 0.0725 mm. This means that the points will be focused on the retina (focal surface) in the form of a circle of blur, covering blocks containing three cones with a membrane diameter of 2.3-4.5 µm (let’s take a membrane of 1.0 for visual acuity = 4.5 µm). The diameter of the circle of confusion is approximately = 7 µm (calculation based on the principle of constructing tables with letters, or circles or squares with gaps to test visual acuity from a distance of 5 m and from the condition when, with visual acuity 1.0, gap = 1.45 mm), which is proportional to the ratio of the working segments of the optical system of the eye and the following values: resolution = 0.0725 mm and D - circle of confusion.

Fig.2.
Scheme of focusing and perception of an object point with a visual acuity of 1.0. In this case, from the condition of the resolution of the eye (visual acuity), sharp perception is possible with a visual acuity of 1.0, when the distance between two points with a clearance between them is 0.0725 mm. From here, each point should be taken as the area of a circle or square with a side of 0.0725 mm. This means that within the boundaries of each subject “point” - a square with a side of 0.0725 mm, there is an infinite number of monobeams of RGB combinations, which cover the RGB block of the cone membrane measuring ≈7 μm and which are transduced into one output signal going through the fat droplet in the head brain. Each object point within the boundaries of, for example, a square with a side of 0.0725 microns, in sharp vision, is perceived by an RGB block with a clearance between any points of also 0.0725 microns. And in visual vision of any image, say, two adjacent object points with a gap are perceived min. two RGB blocks, that is, six cones. As we can see, there is a process of opponent perception of the image in color vision. One cone and a block of three identical cones are not able to evaluate the RGB color palette opponently. [Note necessary.]

Since the clearance, the circle of confusion have dimensions on average of 0.0725 mm at a distance of 250 mm (see Fig. 1,2 from where the calculations of the diameter of the circle of confusion C = "X" = 0.0725 mm were obtained from the condition of viewing from a distance of 0.25 m) . This means that on the retina (focal surface) they will occupy a linear size proportional to the ratio of the working segments of the optical system of the eye and the values: for resolution = 0.0725 mm and D is the circle of confusion.

That is:
D = (bxc):a
or D = (24×72.5):250 = 6.96 µm;

Where:

D—diameter of the circle of confusion in microns; a - distance from the object under consideration to the optical center of the lens = 250 mm; b — focal length of the eye lens = 24 mm; c is the accepted resolution of the eye with visual acuity 1.0 = 0.0725 mm.

2) For people with visual acuity = 0.8, membrane diameter 4.5 µm, the distance between two points (lines) = 0.0896 mm. This means that on the retina (focal surface) the points will be focused in the form of circles of confusion containing at least three cones with a membrane diameter of 4.5 µm (lower visual acuity requires an enlarged membrane) with a circle of confusion diameter of approximately = 8.6 µm (the principle of constructing tables with letters, or circles with gaps to check visual acuity from a distance of 5 m, from the condition when, with visual acuity 1.0, the gap = 1.45 mm) will be equal to the size proportional to the ratio of the working segments of the optical system of the eye and the values: for resolution = 0.0896 mm and D—circle of confusion.

That is:
D = (bxc):a
or D = (24×89.6):250 = 8.6 µm;

Where:

1) option: the sizes of focused object “dots” (circles of confusion) of the order of 7 microns freely accommodate roughly at least 3 cones with a membrane diameter = 3 microns in 1 block. In any case, with three cones in each block (S, M, L) with colors of bluish, greenish and reddish hues, the visual system in the opponent selection mode receives clear information about the object point in the RGB system - color, brightness with a high color depth, what one cone is unable to do.
2) option: the dimensions of the focused object “dots” (circles of confusion) are about 8.6 µm and accommodate 3 cones with a membrane diameter = 4 µm in one block. Also, in any case, with three cones (S, M, L) with colors of bluish, greenish and reddish hues, the visual system in the opponent selection mode has the opportunity to obtain clear information of object points in the RGB system - color, brightness with a high color depth, which is also one cone unable to do this. (The options are selected for people with normal vision, but differing in visual acuity of 1.0 and 0.8).

And according to two options we have:

subject points 72.5 µm with circles of confusion 6.96 µm
subject points of 89.6 μm with circles of confusion of 8.60 μm are projected onto the focal surface of the cones in the zone of membranes (cones) arbitrarily, covering blocks with dimensions of 6.9 μm or 8.6 μm so that the subject point of the image is focused on the focal surface of the retina in the form of circles of confusion , covering RGB blocks consisting, for example, of three cones with a membrane thickness of about 4.5 microns. In this case, it is not necessary that the focus coincide with the centers of the blur circles. Considering the dense packing of blocks with RGB cones in the yellow spot (in an area of 6 mm² there are about 6:3 = 2 million blocks. From where, out of 2 million blocks, 1.5 million work. Dispersed monobeams of object points with a circle of confusion diameter of approximately 7 µm or 8.6 µm cover cones of at least one block (the diameter of the cone membrane is approximately = 3 - 4.5 μm). Photosensors of modern professional cameras consist of pixels with sizes of 5 - 9 μm. The same order and single-layer CMOS type photosensors consist of a constant mosaic of RGB cells (blocks) (and here nature helped us in the invention of an analogue of the retina - a photosensor), which provides color optical images in which it is visually impossible to distinguish grain from a distance of 250 mm with a normal visual acuity of, say, 0.8 (for an object point measuring 0.0725 mm , with a visual system with visual acuity of 1.0 and the size of the circle of confusion = 7 µm, the eye can detect grain).

↑ Clear vision

Clear vision

is more than the ability to see clearly at long or short distances. Even if you can see the tiniest letters on the charts from a distance of twenty feet sixteen inches (6 m 40 cm), this is no guarantee of clear vision. Just because you can read half a dozen letters doesn't mean you can read a whole page, or you can read that page and then focus your vision on an object far away. Clear vision requires the flexibility to see well at all distances—both far and near—or to keep an object in focus for long periods of time.

In addition to our imaginary visual muscle in the brain, there are real visual muscles in the eyes called ciliary muscles, one for each eye. These muscles relax when we look into the distance and contract when we look at something up close. If our eyes are like cameras, then our clear vision muscles focus the lens of that camera. But it is not enough to be able to hold an image in focus for a few seconds to read a line of six or eight letters on a chart.

Clear vision involves four different qualities:

1) precision to see tiny letters, 2) strength to see up close, 3) flexibility to change focus from far to close, and 4) endurance to see clearly over time.

Let's look at each of these four qualities separately.

↑ Accuracy

The size of the letters that we can see on the visual acuity chart gives us an idea of the accuracy of our clear vision muscles. Surprisingly, we don't need advanced focusing skills to see letters 20/20, because 20/20 vision—despite its reputation—is far from perfect. Letters as large as 20/20 give our clear vision muscles some wiggle room—even if the muscles in our eyes are contracting too much or not enough, we'll still consider the letters on that line during an eye exam. It is very common for both children and adults to complain of “blurry vision” despite having 20/20 vision. On the other hand, viewing 20/10 letters (which are half the size of 20/20 letters) requires absolute precision from the eye muscles. If these muscles are unable to contract exactly to the required level, we will not be able to see small letters such as the letters 20/10.

↑ Strength

We determine the strength of our clear vision muscles by measuring how well we can see tiny letters at close range.

Fifteen-year-olds with normal vision can see small letters from three or four inches. With age, however, these forces begin to decrease. As a result of the natural aging process, around the age of thirty, we lose half our power of clear vision and the ability to maintain focus at a distance of four to eight inches (10 to 20 centimeters). Over the next ten years we again lose half our strength and our focus slips to sixteen inches (40 cm). The next time we lose half of our clear vision is usually between forty and forty-five years. During this period, the focus increases to thirty-two inches (80 cm), and suddenly our arms are too short to allow us to read. Although many of the patients I saw stated that the problem was more with their arms than their eyes, all of them chose to get reading glasses rather than undergo arm lengthening surgery.

However, not only older people

need to increase the strength of the visual muscles. Sometimes I meet young people and even children who need to significantly increase this strength in order to read or study without experiencing fatigue. To get an immediate idea of the strength of your own vision, cover one eye with your hand and move closer to the Near Visual Acuity chart so that you can see the letters on line 40. Now close the other eye and repeat the process. If you wear reading glasses, wear them during the test. After you have done the clear vision exercises for two weeks, repeat the test in the same way and note if any changes occur.

↑ Flexibility

Those with objects blurring before their eyes

During the first few seconds when they look up from a book or computer, they have difficulty with the flexibility of their clear vision muscles. If your hobbies or work require your eyes to change focus frequently and the outlines of objects take time to become clear, then you have probably lost many hours waiting for your vision to become clear again. For example, a student who takes longer than others to look away from the board and focus on his notebook will take longer to complete the assignment written on the board.

↑ Endurance

As I said before, it is not enough to be able to name half a dozen letters on a chart during a test. You should be able to keep your vision clear for some time, even if you can read the 20/10 line. Those with stamina problems find it difficult to maintain clear vision when reading or driving. They usually see objects blurred, their eyes become inflamed, and they even get headaches when they have to look closely at something for a long time. The degree of ease with which you can perform the exercises described in the second half of this chapter will give you an idea of both the flexibility and endurance of your vision.

In the first chapter, I told the story of Bill and how his eyesight deteriorated due to surfing the Internet for a long time. This was an example of how 20/20 vision may be a good starting position, but it is only a starting position. Having 20/20 vision doesn't guarantee that things will be clear when we look up from a book or computer monitor, or that we won't suffer from headaches or stomach discomfort when reading. Having 20/20 vision does not guarantee that we can clearly see what is written on road signs at night, or see as well as other people.

The most that can guarantee 20/20 vision is that we can, at a distance from a table created in the nineteenth century, keep our vision in focus long enough to read six or eight letters.

«So why should we settle for 20/20 vision?

? - you ask.

My answer, of course: “ But really, why?”

?»

Why settle for sore eyes or headaches while working on a computer? Why settle for extra effort that subtly wears us down when we read and leaves us feeling like a lemon at the end of the day? Why settle for the stress with which we try to make out road signs when driving in the evening traffic? Shouldn't this Old Testament eye test chart have been buried long before the end of the twentieth century? In short, why should we accept that our vision is not up to par with the Internet era?

Well, if you want the quality of your vision to meet the demands of the twenty-first century, then it's time to work on the flexibility of your eye muscles.

But before we begin, let me give you a word of caution. As with any exercise, testing your eye muscles may initially cause pain and discomfort. Your eyes may burn from tension. You may feel a slight headache. Even your stomach can resist exercise because it is controlled by the same nervous system that controls the focus of your eyes. But if you don’t give up and continue to exercise for seven minutes a day (three and a half minutes for each eye), the pain and discomfort will gradually go away, and you will stop experiencing them not only during the exercises, but also during the rest of the day. time of day too.

Accuracy. Force. Flexibility. Endurance

.
These are the qualities your eyes will acquire as a result of eye fitness classes.
Well. Enough has been said already. Let's get started. Even if you decide to skim through the entire book first and start practicing later, I still recommend that you try the Clear Vision I exercise right away, just to get an idea of how your eye muscles work. Or if you prefer to sit still, try the Clear Vision III exercise—just don't try too hard.

When you are introduced to the exercises in this book, do not read the description of the entire exercise at once. Before reading the description of the next step of the exercise, complete the previous one. It is better to do the exercise rather than just read about it. This way you won’t get confused and everything will work out.

[edit] Conclusions

As a result, with visual acuity 1.0, from the condition of the eye morphology data:
D = (bxc):a
or D = (24×72.5):250 = 6.96 µm;

Where:

we obtain the resolution of the visual system = 6.96 microns. That is, we get a circle of blur of size = 6.96 microns, which is guaranteed to cover a block of three cones with dimensions of 3-4.5 microns (the size of one object point, which an eye with an acuity of 1.0 clearly sees with the same size or smaller, the size 6.96 µm). In this case, there are exactly three cones with a membrane size of 3-4.5 microns that perceive RGB colors, which can be located in adjacent blocks (see Theory of three-component color vision).

Considering that the size of the subject point under consideration with visual acuity of 1.0 = 0.0725 mm, covering the retinal area with blocks measuring 6.96 μm, emits a stream of monochromatic rays, for example, RGB, which are selected differentially from the total mass by three photoreceptors that are sensitive to their flowers. Blocks located nearby oppositely select a stronger central color signal from the surrounding cones with suppressed weaker opposing color signals using three antagonistic mechanisms:

green-red
yellow-blue
black and white (brightness),

which makes it possible to do this with the help of 6 million cones and select and form 1–1.5 million ready-made color selected strong signals sent to the brain to the visual sections of the two hemispheres. (See Opponent Color Vision Theory).

How do e-books affect vision?

Electronic books (readers) today are everywhere replacing paper books. If the rules for handling them are not followed, vision can also be damaged. Ophthalmologists give some tips on how to protect your eyes when using such gadgets.

1. Choose an e-reader with an E-Ink (electronic ink) display rather than a TFT screen. Devices with the E-Ink function only reflect the light falling on them, without being its source, so any information (text and graphic) is perceived by the eyes in almost the same way as an image on plain paper. TFT displays run on gas-discharge lamps, which creates frequent flickering, which negatively affects the health of our eyes and leads to poor vision. 2. Do not read in uncomfortable situations, when shaking in transport, when the text in front of your eyes is “smeared”, or while lying in bed or in low light. 3. Maintain the recommended distance to the screen of about 30 cm to avoid the development of myopia. 4. When reading, also take breaks to give your eyes a rest. 5. Many “readers” have audio playback, and at times you can simply listen to the text rather than read it, which provides a rest for the visual organs.

Hardware treatment

Hardware treatment is often prescribed in Russia, especially for children. There is an opinion that it allows you to improve vision by influencing vision with devices with different operating principles. There are many methods of hardware treatment:

Magnetic therapy (treatment with a magnetic field) is used for inflammation, swelling and hemorrhages of various origins, optic neuritis, and accommodation anomalies.
Laser stimulation and electrical stimulation may help increase the conductivity of impulses in the optic nerve and improve nutrition of the eye.

However, evidence-based medicine does not yet have a clear answer to the question of what is the actual effect of different types of hardware treatment for various eye diseases.

Vitamin B12

Taking an active part in the processes of hematopoiesis, vitamin B12 helps saturate the eyes with nutrients. If there is not enough of it, then the eyes begin to water, get tired faster, and dark circles form under them.

To avoid such troubles, you need to consume up to 3 mcg per day

To do this, you need to include in the diet (the amount is presented in mcg per 100 g):

Grocery list	In mcg per 100 g
Beef liver	60
Pork liver	30
Chicken liver	16,5
Sea fish - mackerel	12,5
Sardines	11
Rabbit meat	4,3
Beef meat	2,6
Sea bass	2,4
Pork and lamb pulp	2
Cod	1,6
River carp	1,5
Dutch cheese	1,4
Crab	1
Chicken egg	0,5
Sour cream	0,4

Zinc

In order to maintain the organs of vision in proper condition, it is necessary to consume zinc daily.

The adult body requires 15 mg per day. This amount will help the retina function normally and prevent diseases such as cataracts and blepharitis.

Another benefit of zinc is that it helps vitamin A to be absorbed. With its deficiency, vision gradually begins to decline.

Therefore, to get zinc from food, it is important to include in your diet foods such as (amount in mg per 100 g):

Stewed beef (9.5) and meat products in the form of fried veal (16) and lamb liver (5.9). Offal products such as boiled chicken hearts (7.3) and beef tongue (4.8) are useful.
You should not ignore the seafood - these are oysters (60) and anchovies (3.5), as well as boiled eel (12). Salmon (0.9) will be useful as canned food.
Delicacies such as nuts and dried fruits are rich in this microelement. It is important to consume pine nuts (6.5), Brazil nuts (4), walnuts (2.7), hazelnuts (1.9), and pistachio nuts (1.4). Don't forget pecans (5.3), almonds (2.2), coconut (2) and cashews (2.1). Slightly lower zinc content is in dried apricots (0.75) and prunes (0.45).
Fruits and vegetables - kohlrabi (3.5) and radishes, boiled carrots, cauliflower and avocado (0.3 mg each) contain this trace element in small quantities.
It is important to consume cereals and legumes - wheat bran (16), lentils (3.8), peas (3.3), beans (1.4), oats (0.5), corn (0.5), rice (0 ,45). Sesame seeds (7.8) and poppy seeds (8.1), pumpkin (7.5) and sunflower (5.6), flax (5.5) are important.
Do not ignore animal products, for example, egg yolk (3.9), yeast (8), milk (0.4).
Porcini mushrooms (1.5), nettles (1) and green onions (0.4) contain small amounts of zinc.

Beta-carotene (vitamin A)

A substance found in foods of animal and non-animal origin that is beneficial for human vision is beta-carotene. It is a powerful immunomodulator and antioxidant.

Thanks to the intake of beta-carotene from food in the doses necessary for a person, it will be possible to restore vision, normalize the functioning of the retina, and get rid of dry eye syndrome and increased lacrimation caused by a lack of vitamins. In addition, beta-carotene reduces the risk of developing cataracts and is a preventive agent for the progression of dystrophic diseases of the retina.

The daily requirement for this useful substance is 5 mg for an adult.

You can find it in many products, however, the record holder is:

Red palm oil is the world record holder for beta-carotene content, 5 mg in 1 teaspoon!
Among greens, sorrel (7 mg) and parsley (5.7 mg) come first, followed by watercress (5.6 mg), then spinach and celery (4.5 mg), almost half as much as green onions. (2 mg), garlic (2.4 mg) and lettuce (1.8 mg). There is very little of it in dill (1 mg).
Berries are not deprived of a substance that benefits human vision: most of it can be obtained by eating sea buckthorn (7 mg), rose hips (5 mg) and wild garlic (4.2 mg), it is found in mountain ash (1.2 mg), not Apricot (1.6 mg) will be less useful; cherries and plums (0.1 mg) close this list.
As for fruits, it is beneficial to consume both mangoes (2.9 mg) and peaches (0.5 mg).
Among the vegetables, carrots lead (9 mg), followed by red peppers (2 mg), non-bitter green peppers (1.2), pumpkin (1.5), and tomatoes (1.2). Separately, we can distinguish broccoli (1.5), Brussels sprouts (0.3 mg) and red cabbage (0.3 mg), as well as potatoes (0.02 mg).
Legumes are not distinguished by their high content; only 1.4 mg of useful substance can be found in green peas and beans.
There is quite a lot of it in melon (2 mg) and much less in watermelon (0.1 mg).
Among products of animal origin, the leader is liver (1 mg), followed by butter and sour cream 0.2 and 0.15 mg, respectively, and at the end there is cottage cheese - 0.06 mg.

When calculating the daily requirement of this substance, it is important to take into account the fact that it is not completely absorbed from food, so if it is deficient, it is worth consuming large amounts of food.

What is binocular vision?

The human ability to see with both eyes, forming a single visual image from two received images, is called binocularity. Exclusively thanks to this skill, people can fully perceive the world around them, assess how far various objects are from them, navigate in space, see objects not only in front, but also from above, below or from the side. That is why the presence of binocular ideal vision is a necessary condition for many professions, this is especially important for pilots, drivers, surgeons, and jewelers.

In order for visual acuity to be high, that is, the images transmitted by the retina are identical in size and shape, they must fall on the same corresponding areas of the eye: each such area of one visual organ has its corresponding point on another organ of vision. There are also disparate (asymmetrical) areas. If the pictures are transmitted to disparate points, their merging does not occur, the person sees a duplicated object.

Full development of binocular vision does not occur in all people. Thus, a newborn initially lacks coordination of the movement of the eyeballs, which means that visual acuity (binocularity) is not developed. Only at 5-8 weeks of life does the child begin to clearly distinguish the position of objects; at 3-4 months, stable fixation of the image appears. In a six-month-old child, a fusion reflex is already formed, that is, two images merge into one, and this is how the development of binocular vision begins. Ophthalmologists observe the full completion of its formation by the age of 12-14 years; in the process, pathologies may arise in the form of strabismus in preschool children; most often, this is easily corrected.

For the proper development of binocular vision it is important that:

there was the same shape of the cornea on both visual organs;
the eye muscles functioned correctly;
the eyeballs worked synchronously (failures often occur due to infectious diseases or traumatic exposure);
the body ensured stable functioning of the peripheral and central nervous systems;
There were no pathologies of the optic nerves, cornea, retina and lens.

That is why, from an early age, parents should visit the ophthalmologist’s office more often in order to promptly eliminate a possible problem at the initial stage.

Injections into the eye

To get directly into the eyeball or vitreous body, as well as behind the eyeball (for example, into the tissue near the periosteum), sometimes it is necessary to inject drugs into the eye using injections. The procedure is unpleasant even from the description and is often painful, so preliminary local anesthesia is performed using drops. Injections are used in the treatment of diseases and injuries of the sclera, cornea, pupil, various neuritis and other pathologies. Injecting the eye requires skill, so only a doctor should do it.

A special type of injection, something between an injection and surgery, is chemodenervation in the treatment of strabismus. Botox is injected into the extraocular muscle and relaxes it. As a result, the asymmetrical position of the pupils becomes more correct. Chemodenervation is often accompanied by other treatment methods (including subsequent surgery).

Learn more about chemodenervation

Operations

The advent and improvement of laser correction has made many eye surgeries much safer, even routine, so that they now involve significantly less risk than before. The excimer laser allows you to preserve the integrity of the eyeball and the biomechanics of the eye, eliminating many previously incurable diseases.

And recently, even some completely blind people have a chance to regain their sight: a bionic retina, which they have learned to implant, will help restore their sight. A microscopic device, consisting of a camera, processor, receiver, wires and microchips, is implanted directly into the human retina and transmits the image to the brain via the optic nerve. It may soon be possible to restore vision to those whose optic nerve is atrophied: the image will be wirelessly transmitted directly to the visual center of the brain, where it is also planned to install chips.