Normal vision is vision without deviations in the visual system. First of all, normal vision is associated with normal refraction of the light ray in the eye. This means that the lenses, cornea and lens focus the image exactly on the retina of the eye, and not in front of it or behind it, and in its center, on the macula.
Each person has their own vision norm. It is determined by what line a person sees in the Golovin-Sivtsev table. The unit we are used to (1.0) means that a person sees the 10th line without correction means, this is his normal vision. One (1.0) also corresponds to 100%.
Now let's tell you a little more about the physical essence of normal vision.
What is the focal length of a healthy eye?
The eye is a complex optical system that consists of biological lenses. Each eye lens has its own focal length at which a clear image of visual objects is projected in the eye on the retina. The focal length has a constant value and directly depends on the curvature of the biological lens.
Before hitting the retina, the light beam passes through the cornea, then through the lens, after which it is refracted and focused on the retina.
An eye that perceives visual information without distortion has a focal length equal to the distance between two lenses that are located between the retina and the cornea. Average given distance in an adult it is about 23-24 mm. This focal length allows the eye to perceive visual information normally. When these distances differ, visual information is not focused accurately on the retina and distortion occurs.
Thus, it turns out that normal vision is vision in which visual information is projected exactly onto the retina eyeball, without distortion. And each person has his own focal length and his own standard of vision.
Refractive error
The refraction of light rays in the eye is called refraction; the refractive power of light rays is measured in diopters.
If light is refracted correctly, the visual image is focused precisely onto the retina.
Incorrect refraction of light rays (impaired refraction) leads to the development and appearance of diseases such as farsightedness, myopia, and astigmatism. If they are present, a person sees the image blurry, unclear, double, and has difficulty seeing far or near. To correct refractive error, medical glasses and contact lenses, which force the light beam to focus on the retina and make the image clear.
You can determine whether you have abnormalities in the functioning of the visual system or whether you have normal vision by undergoing a complete vision diagnostics at the EYE Microsurgery Clinic named after Academician S.N. Fedorov."
The cost of a complete comprehensive vision diagnostics at the Eye Microsurgery Clinic (Ekaterinburg)
The Clinic of Microsurgery "Eye" (Ekaterinburg) conductsfull examination and diagnostics of vision . The examination is carried out without queues or long waits, using the most modern equipment, by highly qualified ophthalmologists. If you are diagnosed with a particular vision disease, the ophthalmologist will prescribe everything necessary treatment, operations (according to indications), as well as regular monitoring.The main causes of visual impairment are glaucoma, myopia, cataracts, gerontological, diabetic changes in the fundus, while significant role Technology, particularly computers, televisions and other devices, plays a role in the development of these diseases.
World Sight Day is celebrated on the second Thursday of October at the initiative of the World Health Organization (WHO). This date is marked on the calendar to draw global attention to the problems of blindness, visual impairment and rehabilitation of people with visual impairments.
One of the factors that helps preserve vision and avoid eye diseases is timely prevention. It is important to avoid “dry eye syndrome”, which is important for people working indoors under artificial light, regularly do eye exercises, when working at a computer for a long time, take breaks every 30-40 minutes to relax the eyes, try to blink more often during prolonged visual stress.
The second factor is the timely detection of symptoms, because up to 80% of vision problems can be avoided if you consult a doctor in time. Having noticed even the slightest deviation in the usual “vision” of the world, for example, when reading, the text becomes blurred, when looking into the distance, objects seem to be in a fog, the eyes are watery or there is a feeling of “sand in the eyes”, sometimes there are “floaters” in front of the eyes, there is discomfort, pain or itching in eyes, it is important to contact an ophthalmologist without delay. It also makes sense to regularly check your visual acuity yourself so as not to miss the first symptoms.
How to check your visual acuity yourself?
At home, you can mainly check only the visual acuity indicator, although it is worth remembering that this is far from the only important characteristic human eye.
Visual acuity is the ability of the eye to distinguish between two points when minimum distance between them, that is, this is an indicator of eye vigilance. Visual acuity of 1.0 (i.e. 100%) is taken as the norm. A person may have visual acuity greater than normal, for example, 1.2 or 1.5, but most have visual acuity below normal - 0.8, or 0.4, or 0.05, and so on.
Essentially, we are testing the distance from which a person can see an object clearly. So, a person with visual acuity of 1.0 will be able to read a car license plate from a distance of 40 meters, and for a person with visual acuity of 0.4 this distance will be approximately 16 meters.
Visual acuity is determined using special tables with optotypes; the most common is the Golovin-Sivtsev table - it is the one that hangs in ophthalmologists’ offices. You can print and use this table at home.
Tables for testing visual acuity
The table for testing visual acuity is made up of similar signs (optotypes) of different sizes - these can be letters, rings with a break in different places (Landolt rings) or pictures (for children). Such a table was first developed in 1862 by the Dutch ophthalmologist G. Snellen - and it is still used abroad. In Russia, a similar table is used, developed by the Soviet ophthalmologist D. Sivtsev. It includes letters and Landolt rings.To make the table, use white matte paper. The size of each sheet of paper when printing should be A4, and the orientation should be landscape. Having printed three sheets, you need to glue them together and attach the table to the wall so that the 10th line is at eye level when testing your vision.
"Save and print all three parts of the table"
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Before the vision test, the table must be illuminated with a lamp. We check each eye separately, cover one eye with our palm, and “read the letters” with the other. Do not close your closed eye. The table should be 5 meters away from the eyes. It should take 2-3 seconds to recognize the sign.
The numerical value of visual acuity is equal to the numerical value of the letter V in the last of the lines in which you did not make errors beyond the norm.
Visual acuity is considered complete if in the rows with V=0.3-0.6 you made no more than one error when reading, and in the rows with V>0.7 - no more than two.
If you receive a visual acuity value of less than 1.0, that is, you do not see or do not see all the letters below the conditional 10th line, then you should undergo a professional examination by an ophthalmologist, where they will check the characteristics of your vision in more detail - eye refraction, fundus, functional and anatomical features of the visual apparatus.
Office workers are at risk
If your line of work requires you to spend a lot of time sitting in front of a computer screen, then take care to protect your eyes:
- Move the monitor further away, the distance from your eyes to the screen should be at least 50-60 cm.
- Do not place your computer in front of a window.
- Keep the screen clean - wipe it with special wipes at least once a week.
- Make sure that the light in the room is not too bright or too dark.
- If your eyes are tired, do a set of special gymnastics.
- In the evening, if your eyes are very tired, wash them with tea, chamomile infusion, or apply special compresses to your eyes.
- Strengthen your vision with nutrition: yellow and bright orange fruits and vegetables (pumpkin, carrots, sweet peppers, oranges, persimmons), honey, apricots in any form, blueberries, carrots and others will help with this.
Age-related changes
The most common eye diseases that lead to vision loss are glaucoma, age-related macular degeneration (AMD is colloquially called retinal dystrophy) and cataracts. Vision can be restored only with cataracts; changes with glaucoma and AMD are irreversible. Moreover, glaucoma is chronic illness, which can occur without any symptoms, so mandatory preventive examinations are needed for timely diagnosis.
Macular degeneration is one of the most common causes of blindness in humans retirement age, therefore, every person over 40 years of age, especially if he is at risk, should regularly visit an ophthalmologist.
9024 09/18/2019 5 min.The human eye is an entire optical system, quite complex in its design. It contains biological lenses that have their own separate and unique focus. This is how, when light is refracted, a picture is projected. And if the system is working properly, the image will be clear. The focal length has its own value; it is constant and depends on how curved the biological lenses are. In healthy eyes, the average distance should not exceed 24 mm - this is the norm, which is equal to the distance between the cornea and the retina.
When light is refracted, a process called refraction occurs, which has its own measurement values - diopters. If refraction occurs without any deviation, the image falls directly on the retina and is focused there. The definition of normal vision is usually considered to be one or 100%, but this value is relative depending on the individual case.
What is the norm
It has been established that visual acuity is considered to be the norm - 100% or V = 1.0, the refraction of the eye is 0, - 22-24 mm Hg.
The norm is considered to be a combination of refraction and acuity indicators, pressure in in this case refers to third-party assessment factors, but in some cases plays a significant role, because primarily affects the clarity of vision.
Why acuity and refraction are key:
- Refraction is the position of the focal point relative to the retina. Optical system the eye is made up of a lens, vitreous, cornea and aqueous body. The incoming ray passes through each refractive medium in turn and reaches the macula - a small spot on the back wall the eye, consisting of nerve endings, cones responsible for color perception, and blood vessels. The reflected beam projects the image and transmits it visual analyzer in the brain. And as a result, we see the image, and how well it enters the analyzer is the work of refraction. During the normal functioning of the totality of all systems, the focal point is on the surface of the retina, and this is called emmetropia (indicators are equal to 0). Refraction is measured in Diopters.
- Visual acuity- this is the ability to perceive two points at a minimum distance between them. Simply put, this indicator determines the quality of the reproduced picture in the brain. The difference between refraction is that acuity does not have an exact mathematical model of calculation, unlike refraction. All designations for visual acuity are conditional and vary depending on the individuality of the organism.
- Farsightedness. In this case, the focus of the image is behind the retina. A person sees poorly at a distance close to the eyes. Fogging occurs, it is obvious on the face, and may occur.
Treatment of farsightedness is possible with the information available.
- . Here there is an inability to focus on the retina. The basis of the disorder is the irregular shape of the cornea or lens. The main symptoms: distortion of the image, doubling of objects, fatigue after a short period of time (asthenopia), persistent tension and, as a result, headaches.
- Glaucoma. A complex of diseases based on deviations from normal intraocular pressure. Increased IOP is diagnosed more often than decreased IOP, and has different consequences. When reduced, it develops, when. In case of severe damage optic nerve There is a severe deterioration in vision up to complete blindness. This disease can only be treated surgically and varies slightly various forms, some of which are irreversible.
Read about the causes of congenital glaucoma.
- Cataract. A disease with progressive effects. The disease can occur in at a young age, but mainly develops in the elderly. A person begins to react painfully to light, to distinguish color shades poorly, difficulties arise when reading, and vision decreases significantly in twilight () and darkness.
Some diseases occur throughout life. This is due to factors such as the specifics of the work, daily eye strain, harmful production or poor working conditions. Often such diseases can be inherited and already in early age Children may be diagnosed with eye diseases.
Preventive methods
These methods include:
- Rejection of bad habits. Smoking causes vascular spasms, and alcohol destroys the liver, which most directly affects the eyes.
- Healthy and balanced diet will preserve the vascular system in healthy looking, which means blood circulation will be at the proper level.
- Vitamin therapy for local and general. And what eye vitamins to improve vision are described in this article. There are also .
- Regular classes exercise helps improve blood circulation.
- Avoid heavy loads, heavy loads, and prolonged work at the monitor.
- Do eye exercises and palming - this allows you to keep your muscles toned and relax your eyes after severe fatigue.
Exercises
Among the most common and simple exercises Several can be identified. They will help strengthen the muscle groups of the eyes, and therefore stimulate the strengthening of the position of the cornea and lens, blood circulation and the enrichment of all parts of the eye with oxygen.
- Sit up straight and make the following eye movements several times: left and right, up and down, circular in one direction and the other. Blink.
- Look into the distance and choose an object to look at. Hold your gaze for a few seconds. Then move your gaze to the point marked on the glass and focus your gaze on it. Look into the distance again. Blink.
- Close your eyes tightly and open them. Repeat several times.
- To relax your eyes, use palming.
According to Bates
A famous ophthalmologist of the 19th century, who stated that visual deviations depend on overexertion of groups oculomotor muscles,W. Bates invented a unique method of relaxing the eyes - palming. Nothing is required to use it. Except your own palms. Rub them to create warmth and apply to the eyeballs, pressing lightly back side. Repeat several times. Mentally imagine a beautiful landscape or picture, remember pleasant things, and continue until you feel relaxation in the eye muscles. An indicator will be the fact that the flashes will begin to disappear with your eyes closed.
In ophthalmology there are different types blindness - from complete loss of vision to partial. Depending on the causes of vision impairment, both eyes or just one of them may be affected. Human vision is the main sensory organ through which information from the outside world is received, and its loss negatively affects the quality of life and work activity.
Partial or complete blindness is not only associated with biological pathologies, but also depends on the safety of the workplace, home environment, and the presence of contact with chemicals and toxic substances. A polluted environment, pesticides in agriculture, or insufficient dietary intake of microelements can lead to partial or complete blindness.
What is visual acuity, what are the deviations?
Visual acuity is the ability of the eye to distinguish between two figures that are close to each other. When checking, Sivtsev-Golovin tables are used, consisting of 12 rows. The top line in these tables is visible to people with normal vision at 50 m, and the tenth line at 5 m. Such vision is designated 1.0. Additional lines (11-12) are visible to people with above-normal vision, 1.5 and 2.0, respectively, but this is not the limit: there is evidence of people who are able to distinguish faces at a distance of 1.5 km.
Even a person with perfect vision can go blind, this is due to for various reasons, both congenital and acquired. WHO recommends undergoing preventive examination 1 time per year. Timely diagnosis is necessary to prevent vision loss. Around the world, 300 million people suffer from this disease. In ophthalmology, blindness refers to vision anomalies in which a person completely or partially loses visual perception.
Pathologies causing deterioration or loss of vision:
- Eye cancer.
- Cataracts, clouding of the lens in old age.
- Eyeball injury or cerebral hemorrhage.
- Glaucoma, damage to the optic nerve due to high blood pressure.
- Weakened vision due to HIV or CMV infection.
- Retinoblastoma, a common form of childhood cancer.
- Retinopathy caused by diabetes.
- Amblyopia. With it, blindness in one eye occurs when the brain suppresses the functioning of the organ to obtain a clear picture.
- Strabismus.
- Infectious diseases that can cause complications on the sensory organs.
- Inherited diseases that cause decreased vision.
- The cause of blindness is an anomaly in the refraction of light rays.
The occurrence of the latter factor can cause:
- Myopia. The focal point of light rays is not on the retina, but in front of it, which makes it difficult to see distant objects.
- Farsightedness. The focal point is located behind the retina, and only with age-related farsightedness are distant objects clearly visible.
- Astigmatism. Disturbance in the shape of the lens or eyeball, causing objects to have blurred or bifurcated boundaries.
In order for a doctor to make a correct diagnosis, it is necessary to undergo a comprehensive examination.
Blindness can be either congenital or acquired. Congenital blindness occurs when hereditary diseases, intrauterine defects in fetal development, poisoning or infections suffered by the mother during pregnancy. It is placed immediately after birth. Acquired blindness occurs when oxygen starvation and birth injuries, immune diseases, diabetes, pathologies affecting the central nervous system, including infectious diseases of cardio-vascular system, injuries, poisoning with toxic substances and poor nutrition.
Types of blindness
Blindness can be permanent, when irreversible changes have occurred in vision, and temporary, when the loss of senses is episodic. There are many classifications of blindness, the main ones being: according to the degree of vision loss, and the cause of its occurrence. To determine the disease, visual acuity, intraocular pressure and field of vision are determined separately for each eye.
Classification according to the degree of visual impairment contains the following concepts:
- Occupational blindness. If you lose your vision, it is impossible to continue your professional activities.
- Partial blindness. It is impossible to clearly see an object located at a distance of 3 m or count the number of objects at this distance.
- Subject or practical blindness. There is light perception, the outlines of objects are indistinguishable.
- Absolute blindness. There are no visual signals, the pupil does not respond to bright light. The optic nerve does not convey the characteristics of objects, their color, size, or distance to them.
Visually impaired:
- first category - 10-30% of the norm, with one eye, with correction with glasses;
- second category - 5-10% of the norm, with one eye.
- third category - 2-5% of the norm;
- fourth category - only the sensation of light is present;
- fifth category - there is no light perception, patients do not see anything.
Due to their occurrence, the following conditions are distinguished:
Signs of vision problems
Vision is a complex process. Due to the fact that a person has 2 eyes, the world around him is seen not as flat, but as three-dimensional. The advantage of binocular vision comes with a disadvantage when the patient notices a decrease in visual acuity in one eye. Without proper testing, signs may not be noticed for several years. Not regularly visiting an ophthalmologist is a dangerous practice that exposes the main channel of information to unnecessary risk.
Reasons for urgently visiting a doctor:
- discharge from one or both eyes;
- persistent tension in the muscles surrounding the eyeball, regardless of the degree of fatigue;
- nervous tic in a calm emotional state, lasting for 1 week;
- pain in the eyelids or eyeballs that does not go away within 3 days;
- constant drying of the eyeballs, which may indicate problems with blood supply or a fungal infection;
- sensation of a foreign object that did not go away after washing the eye;
- pain or pressure in the back of the eyeball, often a warning sign of a stroke;
- frequent cases of burst vessels, which indicates increased intraocular pressure.
When going to the doctor, not only visual acuity is measured, but also horizontal and vertical angle review, as well as intraocular pressure. These checks will allow you to notice deterioration before degeneration becomes irreversible. Children need additional training for examination.
Consequences of blindness
With a significant decrease in vision, patients feel distanced from the world, have problems with orientation in space, and become unable to know the exact size or distance to an object. A decrease or cessation of labor activity leads to a deterioration in living conditions. With such a vast increase in negative situations, people develop negative emotions, depressive states, thoughts about the wrongness of life and suicide attempts. When examining and deciding on the degree of blindness, a special scale is used.
Blind people include:
- completely lost vision;
- people who only have light perception left;
- patients who have residual vision of 0.02-0.05 from normal.
A blind patient needs psychological help, in order to cope with emotional stress. Only the help of doctors specializing in vision loss will make it clear to the patient how to prepare for changed circumstances.
When the emotional background returns to normal, the brain redistributes resources between other senses, which take on the functions of lost vision. The sense of hearing, smell and touch is enhanced, resulting in improved orientation and long-term memory. Analytical abilities increase logical thinking and attention, thanks to which blind people can navigate in space. An important component of further existence is the memory of visual images of various objects.
At timely diagnosis four out of five people with blindness could have avoided it. To detect a problem in a timely manner, you must undergo annual examination see an ophthalmologist to see if the necessary nutrients are supplied with your diet. It is also necessary to monitor personal safety and avoid toxic effects on the body. In ophthalmology, disorders of the optic nerve or cerebral hemorrhage are considered irreversible; all other diseases are treated with to varying degrees success.
People who are at risk with a predisposition to pathologies when there is visual impairment (blindness can develop unnoticed), as well as those who have suffered injury to the eyes or occipital lobes of the brain, must undergo annual diagnostics and consult a doctor if symptoms of visual impairment are detected.
Video
What is good vision?
Good to see - what does this mean? Immediately after birth, a person has good vision, which, alas, tends to deteriorate. In the article we will answer one question - how much does good vision cost?
Deviations from the norm
Rays of light passing through the eye are refracted. The power of refraction is indicated in diopters.
When the eye's ability to refract rays is impaired, vision deviates from the norm. Identified as follows:
- 0 - 20 diopters with a "-" sign - myopia.
- 0 – 20 diopters with a “+” sign – hypermetropia.
Norm
Normal in Everyday life Vision is considered when a person sees into the distance and reads without effort.
Ophthalmologists denote good vision as 1.0. Sometimes there are deviations of 0.5 diopters. In this case, correction is not needed and the person is considered to have 100% vision.
When checked by an ophthalmologist, a person with good vision clearly sees line 10 of Sivtsev’s table (letters).
How do colored lenses affect your eyes?
Colored lenses were created about thirty years ago, but they are still relevant today. Progress has not passed them by, and a lot has changed in thirty years. They have become the most comfortable, they can now be selected for a wide variety of eyes, and a variety of color variations have appeared.
Some people categorically refuse to use this eye decoration, believing that it contributes to the deterioration of vision. There are many myths created based on this opinion. But are they true?
Can colored lenses stain your eyes?
Some believe that since these lenses contain dye and are placed so close to the eye, the dyes gradually become absorbed into the eyes, dramatically impairing vision.
The appearance of this myth is easy to explain - most likely, it was invented at a time when lenses were not so comfortable and of high quality. And, he's not being truthful. The substance that gives the color effect is located in the center of the lens. There are protective shells along its edges. The outer shell protects the eyes from a variety of external negative factors, and the inner one increases the comfort when wearing them and, in fact, prevents dyes from penetrating into the eye.
It is worth considering that this applies only to high-quality eye colored lenses created by manufacturers with a good reputation.
Do colored lenses harm brown eyes?
About the dangers of colored lenses for brown eyes legends are made. Considering that only a few colored lenses look good on brown eyes, the idea that suitable lenses are very dense and disrupt many of the processes occurring in the eyes lives in many minds. Many people think that tinted lenses suitable for light-eyed people do not cause harm, but colored lenses are what contribute to severe vision deterioration.
Of course, not all lenses can cover the color of brown eyes, especially very dark ones. But, if you choose them wisely, the desired result can be achieved. There is some truth in the myth - tinted lenses will not “make friends” with brown eyes. But they affect eyes in exactly the same way as colored eyes, and on eyes of very different colors.
It is possible to contribute to ending the existence of this myth. Take a closer look at the color chart of colored lenses, which will help you choose the most suitable shades if you have dark brown eyes. But, do not forget that there are no ideal lenses that completely cover the natural color of the eyes, and sometimes the natural color will still show through. For example, if you look at a bright light, the iris near the pupil will be brown.
| Bright green | + | |
| Emerald | + | |
| Walnut | + | |
| Lilac | + | |
| Sapphire | + | |
| Grey | + | |
| Blue | + |
If the shade you're eyeing for your brown eyes isn't here, you can think logically. In case it looks darker than the others, it will probably work. If you prefer the lightest shade, especially one that is very different from your native color, such lenses will look bad.
Do colored lenses worsen vision due to dioptres?
This question may be asked by people who have little information about colored lenses. The myth that any colored lenses can correct vision is very old, but still relevant.
There are colored lenses with and without diopters. Therefore, if you are not bothered by vision problems, you need to purchase the most ordinary lenses without diopters. But, if you are pursuing two goals at once, that is, you want to change the color and improve your vision, contact a specialist.
Do colored lenses narrow your field of vision?
The opinion about this can hardly be called completely untrue, because in some situations the lenses slightly narrow the field of vision, for example, impairing the visibility of what is happening from the side.
But this problem does not bother everyone. If this object decorating the eyes is selected taking into account the radius of curvature, the risk of its occurrence is reduced to zero. If you find it difficult to choose and have no idea about this radius, it is better to ask an ophthalmologist for help.
Do colored lenses distort color reproduction?
This myth is extremely easy to dispel if you finally dare and try on something that has scared you for so long. But, if you don't need to, and you're wondering why the myth doesn't carry the truth, there is a reasonable explanation.
If you look at the lens, you will notice that there is not a fraction of color in the pupil area. And, it is designed in such a way that if selected correctly and worn correctly, it will not close the pupil. Consequently, the colored part covers only the iris and does not distort the color rendition in any way.
Can wearing colored lenses cause chronic conjunctivitis?
If you have a friend or acquaintance who insists that their eyes have been damaged by colored lenses. Having acquired chronic conjunctivitis, you should not completely believe their words.
It can be said that their eyes have suffered from the use of colored lenses. But the reason lies not in the composition and features of this item, but in its careless use. If you handle lenses carelessly and do not follow hygiene rules, they can cause harm to your eyes and even cause certain diseases. But if you handle them properly and consult with specialists, no problems will arise.
Do colored lenses hurt your eyes?
Ophthalmologists have often heard stories that trying on lenses and wearing them is a painful and painful task, after which the eyes turn red, make them want to scratch and hurt. Such stories, told by those who have direct affiliation with medical professions, scare them and give them a reason not to allow themselves to use lenses. But should these stories be believed?
Undoubtedly, they can be true in cases where the basic rules for using colored lenses have not been followed. Don't assume that these delicate eye color changing products can be handled as you please.
If you do not have experience in the use and selection of conventional lenses, be sure to familiarize yourself with the basic rules for their use. If you buy a box of lenses and try them on without learning how to do it and purchasing the right related products, the risk of harm to your eyes is really high.
Can colored lenses cause dry eyes?
Some people using colored lenses have complained about discomfort, the cause of which was dry eyes. Moreover, it is difficult to eliminate it with special drops, because when wearing lenses it appears again. There was only one way out - to get rid of the lenses. But isn't this too radical a measure?
Most likely, the cause of dry eyes in this case was wearing lenses too often, if, of course, other hygiene measures were followed.
The recommended time for their use is eight hours. Next, it’s better to shoot from. You shouldn't wear them every day without breaks. Despite the fact that they are created from safe materials, your eyes need to rest, because they are still foreign body in them.
Video - is it worth wearing colored and decorative lenses?
How to use colored lenses so they can't cause harm
There are several rules, knowledge and use of which will ensure wearing colored lenses with comfort:
- So that buying lenses does not turn out to be a waste of money and a provocateur of various eye problems, do not be lazy to go to the ophthalmologist, even if you have not observed any problems. There are many factors due to which it is strictly not recommended to use lenses. Find out if you have any.
- An important rule is proper selection. If, for example, you buy lenses with diopters for eyes that have perfect vision, you will ruin it. Therefore, do not hesitate to ask sales consultants and ophthalmologists, especially if you have a minimum of information about colored lenses.
- You need to ask not only about the colored lenses themselves, but also about the products that go with them. Don't skimp on what you should buy to make wearing them as comfortable as possible.
- When trying on lenses, basic hygiene is required. Wash your hands before applying them to your eyes. If there is no source nearby clean water, use an antiseptic. You should also remove the lenses with clean hands.
- Pay attention to how long these small eye decorations are designed to last. Wearing them longer than the period indicated on the package is strictly not recommended. For example, if you bought disposable lenses for an event, you can wear them for no more than one day. Even if you only wore them for a few hours, you should dispose of them the next day.
- Not removing your lenses at night is a huge mistake, fraught with extreme consequences. unpleasant consequences. To avoid them, remember to take them off before going to bed.
- If you are sure that you did everything correctly, but the lenses cause particular discomfort, stop wearing them and go for a consultation with a good ophthalmologist. Perhaps with initial examination eye features were not identified or were acquired later.
Our vision makes our life richer, more informative, more active. Therefore, it is so important for a person to promptly solve all problems that arise with the eyes, because even the slightest possibility of stopping seeing this beautiful world is frightening.
The eyes are a window to the world, they are a reflection of the state of our soul, they are a repository of riddles and secrets.
In this article we will pay special attention to central and peripheral vision.
What are their differences? How is their quality determined? What are the differences between peripheral and central vision in humans and animals, and how do animals see in general? And how to improve peripheral vision...
This and much, much more will be discussed in this article.
Central and peripheral vision. Interesting information.
First about central vision.
This is the most important element visual function person.
It received this name because... provided by the central portion of the retina and the central fovea. Gives a person the opportunity to distinguish shapes and small details of objects, therefore its second name is shaped vision.
Even if it decreases slightly, a person will immediately feel it.
The main characteristic of central vision is visual acuity.
Her research has great importance in assessing the entire human visual system, to track a variety of pathological processes in the organs of vision.
Visual acuity refers to the ability of the human eye to distinguish between two points in space located close to each other, at a certain distance from the person.
Let us also pay attention to such a concept as the visual angle, which is the angle formed between the two extreme points of the object in question and the nodal point of the eye.
It turns out that the larger the visual angle, the lower its acuity.
Now about peripheral vision.
It provides a person’s orientation in space and makes it possible to see in darkness and semi-darkness.
How to understand what is central and what is peripheral vision?
Turn your head to the right, catch an object with your eyes, for example, a picture on the wall, and fix your gaze on any individual element of it. You see him well, clearly, don’t you?
This is thanks to central vision. But besides this object, which you see so well, a large number of different things also come into your field of vision. This is, for example, a door to another room, a closet that stands next to the painting you have chosen, a dog sitting on the floor a little further away. You see all these objects unclearly, but, nevertheless, you see, you have the ability to capture their movement and react to it.
This is peripheral vision.
Both human eyes, without moving, are capable of covering 180 degrees along the horizontal meridian and a little less - about 130 degrees along the vertical.
As we have already noticed, the acuity of peripheral vision is less than central. This is explained by the fact that the number of cones, from the center to peripheral departments retina is significantly reduced.
Peripheral vision is characterized by the so-called visual field.
This is the space that is perceived by a fixed gaze.
Peripheral vision is invaluable to humans.
It is thanks to it that free, habitual movement in the space surrounding a person and orientation in the environment around us is possible.
If peripheral vision is lost for some reason, then even with full preservation of central vision, the individual cannot move independently, he will bump into every object on his way, and the ability to see large objects with his gaze will be lost.
What kind of vision is considered good?
Now consider the following questions: how the quality of central and peripheral vision is measured, as well as what indicators are considered normal.
First about central vision.
We are accustomed to the fact that if a person sees well, they say about him “one in both eyes.”
What does it mean? That each eye individually can distinguish two closely spaced points in space, which give an image on the retina at an angle of one minute. So it turns out to be one for both eyes.
By the way, this is only the lower norm. There are people who have vision of 1,2, 2 or more.
We most often use the Golovin-Sivtsev table to determine visual acuity, the same one with the well-known letters Ш B in the upper part. A person sits in front of the table at a distance of 5 meters and closes alternately his right and left eyes. The doctor points to the letters in the table, and the patient says them out loud.
The vision of a person who can see the tenth line with one eye is considered normal.
Peripheral vision.
It is characterized by a field of view. Its change is an early and sometimes the only sign of some eye ailments.
The dynamics of changes in the visual field makes it possible to assess the course of the disease, as well as the effectiveness of its treatment. In addition, through the study of this parameter, atypical processes in the brain are revealed.
Studying the visual field is determining its boundaries, identifying defects in visual function within them.
To achieve these goals, we use various methods.
The simplest of them is the control one.
Allows you to quickly, literally in a few minutes, without using any instruments, determine a person’s field of vision.
The essence of this method is to compare the physician’s peripheral vision (which should be normal) with the patient’s peripheral vision.
It looks like this. The doctor and the patient sit opposite each other at a distance of one meter, each of them closes one eye (opposite eyes close), and open eyes act as a fixation point. Then the doctor begins to slowly move his hand, which is located on the side, out of the field of view, and gradually bring it closer to the center of the field of view. The patient must indicate the moment when he sees her. The study is repeated from all sides.
Using this method, a person's peripheral vision is only roughly assessed.
There are also more complex methods that give deeper results, such as campimetry and perimetry. 
The boundaries of the visual field may vary from person to person and depend, among other things, on the level of intelligence and the structural features of the patient’s face.
Normal indicators for white color the following: up - 50o, outwards - 90o, up outwards - 70o, up inwards - 60o, downwards outwards - 90o, downwards - 60o, downwards inwards - 50o, inwards - 50o.
Color perception in central and peripheral vision.
It has been experimentally established that human eyes can distinguish up to 150,000 shades and color tones.
This ability has an impact on various aspects of a person’s life.
Color vision enriches the picture of the world, gives the individual more useful information, and influences his psychophysical state.
Colors are actively used everywhere - in painting, industry, scientific research...
Behind color vision The so-called cones, light-sensitive cells that are found in the human eye, respond. But the rods are responsible for night vision. There are three types of cones in the retina, each of which is most sensitive to the blue, green and red parts of the spectrum.
Of course, the picture we get thanks to central vision is better saturated with colors compared to the result of peripheral vision. Peripheral vision is better at capturing more bright colors, red, for example, or black.
Women and men, it turns out, see differently!
Interestingly, women and men see things somewhat differently.
Due to certain differences in the structure of the eyes, representatives of the fair sex are able to distinguish more colors and shades than the strong part of humanity.
In addition, scientists have proven that men have better developed central vision, while women have better peripheral vision.
This is explained by the nature of the activities of people of different sexes in ancient times.
Men went hunting, where it was important to clearly concentrate on one object and not see anything else. And the women looked after the housing and had to quickly notice the slightest changes, disturbances in the usual flow of everyday life (for example, quickly notice a snake crawling into a cave).
There is statistical evidence to support this statement. For example, in 1997, in the UK, 4,132 children were injured in road accidents, of which 60% were boys and 40% were girls.
Besides, Insurance companies note that women are much less likely than men to get into car accidents that involve side impacts at intersections. But parallel parking is more difficult for beautiful ladies.
Women also see better in the dark and notice more small details in a wide field compared to men.
At the same time, the eyes of the latter are well adapted to tracking an object at a long distance.
If we take into account other physiological characteristics women and men, the following advice will be formed - during a long trip it is best to alternate as follows - give the woman the day, and the man the night.
And a few more interesting facts.
U beautiful ladies eyes get tired more slowly than in men.
In addition, women's eyes are better suited for observing objects at close range, so they can, for example, thread a needle much faster and more dexterously than men.
People, animals and their vision.
Since childhood, people have been fascinated by the question - how do animals, our beloved cats and dogs, birds soaring in the heights, creatures swimming in the sea see?
Scientists for a long time We were studying the structure of the eyes of birds, animals and fish so that we could finally find out the answers that interest us.
Let's start with our favorite pets - dogs and cats.
The way they see the world is significantly different from the way a person sees the world. This happens for several reasons.
First.
Visual acuity in these animals is significantly lower than in humans. A dog, for example, has vision of approximately 0.3, and cats generally have 0.1. At the same time, these animals have an incredibly wide field of vision, much wider than that of humans.
The conclusion can be drawn as follows: the eyes of animals are maximally adapted for panoramic vision.
This is due to both the structure of the retina and the anatomical location of the organs.
Second.
Animals see much better than humans in the dark.
It is also interesting that dogs and cats see even better at night than during the day. All thanks to the special structure of the retina and the presence of a special reflective layer.
Third.
Our pets, unlike humans, distinguish moving objects better than static ones.
Moreover, animals have a unique ability to determine the distance at which an object is located.
Quadruple.
There are differences in the perception of colors. And this despite the fact that the structure of the cornea and lens in animals and humans is practically no different.
Humans can distinguish many more colors than dogs and cats.
And this is due to the structural features of the eyes. For example, a dog’s eyes have fewer “cones” responsible for color perception than a human’s. Therefore, they distinguish less colors.
Previously, there was a general theory that the vision of animals, cats and dogs, is black and white.
This is if we talk about differences human vision pets.
Now about other animals and birds.
Monkeys, for example, see three times better than humans.
Eagles, vultures, and falcons have extraordinary visual acuity. The latter can clearly see a target up to 10 cm in size at a distance of about 1.5 km. And the vulture is able to distinguish small rodents that are located 5 km away from it.
The record holder in panoramic vision is the woodcock. It's almost circular!
But the pigeon we are all familiar with has a viewing angle of approximately 340 degrees.
Deep-sea fish see well in absolute darkness, seahorses and chameleons can generally look in different directions at the same time, and all because their eyes move independently of each other.
Here are some interesting facts.
How does our vision change throughout our lives?
How does our vision, both central and peripheral, change during life? What kind of vision are we born with, and what kind of vision do we come to old age with? Let's pay attention to these issues.
IN different periods People have different visual acuities throughout their lives.
A person is born into the world, and his blood pressure will be low. At the age of four months, the child’s visual acuity is approximately 0.06, by the year it grows to 0.1-0.3, and only by the age of five (in some cases it takes up to 15 years) vision becomes normal.
Over time, the situation changes. This is due to the fact that the eyes, like any other organs, undergo certain age-related changes, their activity gradually decreases.
This means that the older a person gets, the more light he needs for reading and other activities. In addition, in old age, changes in lighting brightness are very painful. The world an elderly person seems to fade, becomes dull.
It is believed that deterioration of visual acuity is an inevitable or almost inevitable phenomenon in old age.
Let us highlight the following points.
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With age, the size of the pupils decreases due to weakening of the muscles that are responsible for their regulation. As a result, the reaction of the pupils to the light flux worsens.
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Also, with age, the eyes recognize colors worse, the contrast and brightness of the image decreases. This is a consequence of a decrease in the number of retinal cells that are responsible for the perception of colors, shades, contrast and brightness.
What happens to peripheral vision?
It also gets worse with age - lateral vision worsens, visual fields narrow.
This is very important to know and take into account, especially for people who continue to lead an active lifestyle, drive a car, etc.
A significant deterioration in peripheral vision occurs after 65 years.
The following conclusion can be drawn.
A decrease in central and peripheral vision with age is normal, because the eyes, like any other organ human body, are subject to aging.
I can't be with poor eyesight...
Many of us have known since childhood what we want to be in adulthood.
Some dreamed of becoming a pilot, some a car mechanic, some a photographer.
Everyone would like to do exactly what they like in life – no more, no less. And what a surprise and disappointment it can be when, upon receiving a medical certificate for admission to one or another educational institution, it turns out that the long-awaited profession will not become yours, and all because of poor eyesight.
Some people don’t even think that it can become a real obstacle to the implementation of plans for the future.
So, let's figure out which professions require good vision.
It turns out there are not so few of them.
For example, visual acuity is necessary for jewelers, watchmakers, people involved in precision small instrument making in the electrical and radio engineering industries, in optical-mechanical production, as well as those who have a typographic profession (this could be a typesetter, proofreader, etc.).
Undoubtedly, the vision of a photographer, seamstress, or shoemaker must be sharp.
In all of the above cases, the quality of central vision is more important, but there are professions where peripheral vision also plays a role.
For example, a pilot aircraft. No one will argue that his peripheral vision should be as good as his central vision.
The profession of a driver is similar. Well-developed peripheral vision will allow you to avoid many dangerous and unpleasant situations, including emergency situations on road.
In addition, auto mechanics must have excellent vision (both central and peripheral). This is one of the important requirements for candidates when hiring for this position.
Don't forget about the athletes either. For example, football players, hockey players, and handball players have peripheral vision that approaches ideal.
There are also professions where it is very important to correctly distinguish colors (preservation of color vision).
These are, for example, designers, seamstresses, shoemakers, and workers in the radio engineering industry.
We train peripheral vision. A couple of exercises.
You've probably heard about speed reading courses.
The organizers undertake, in a couple of months and for not that much money, to teach you how to swallow books one by one, and remember their content perfectly. So, lion's share Time during the courses is devoted specifically to the development of peripheral vision. Subsequently, a person will not need to move his eyes along the lines of a book; he will immediately be able to see the entire page.
Therefore, if you set yourself a task in short time develop your peripheral vision perfectly, you can enroll in speed reading courses, and in the near future you will notice significant changes and improvements.
But not everyone wants to spend time on such events.
For those who want to improve their peripheral vision at home, in a calm environment, here are a few exercises.
Exercise No. 1.
Stand near the window and fix your gaze on some object on the street. This could be a satellite dish on a neighboring house, someone's balcony, or a slide on the playground.
Recorded? Now, without moving your eyes and head, name the objects that are near your chosen object.
Exercise No. 2.
Open the book you are currently reading.
Choose a word on one of the pages and fix your gaze on it. Now, without moving your pupils, try to read the words around the one on which you fixed your gaze.
Exercise No. 3.
For this you will need a newspaper.
In it you need to find the narrowest column, and then take a red pen and draw a straight thin line in the center of the column, from top to bottom. Now, glancing only along the red line, without turning your pupils to the right and left, try to read the contents of the column.
Don't worry if you can't do it the first time.
When you are successful with a narrow column, choose a wider one, etc.
Soon you will be able to look at entire pages of books and magazines.
