Popular Posts

Editor'S Choice - 2019

Vision 1

Visual acuity is the ability of the eye to perceive separately two points located at some distance from each other. The measure of visual acuity is the angle of view, i.e., the angle formed by the rays emanating from the edges of the object under consideration or from two points (A, C) to the nodal point (K) of the eye (the diagram, a and b is a display of points A and B on retina). Visual acuity is inversely proportional to the angle of view, i.e., the smaller it is, the higher the visual acuity. Normally, the human eye is able to separately perceive objects, the angular distance between which is not less than 1 '(one minute).


Diagram illustrating the concept of visual acuity

Visual acuity is one of the most important functions of the organ of vision. It depends on the size of the cones in the area of ​​the yellow spot, retina, as well as on a number of factors: eye refraction, pupil width, transparency of the cornea, lens, vitreous body, condition of the retina and optic nerve, age. Determining visual acuity is one of the main methods for studying the state of the organ of vision.

For the study of visual acuity use tables consisting of 12 rows of letters, rings or drawings (tables for children) of a certain size. The tables are constructed in such a way that the thickness of the stroke of a letter or sign of the tenth row is visible from a distance of 5 m from an angle of view of 1 ', which corresponds to a visual acuity of 1.0. The distinction of letters, signs of the upper row of the table corresponds to the visual acuity equal to 0.1, the second - 0.2, the third - 0.3, etc. The distinction between signs in the 11 and 12 rows corresponds to the visual acuity of 1.5 and 2.0.

When checking the visual acuity of the table should be well lit, for which they are placed in the lighting apparatus of the Company (see. Rota device). The study is conducted from a distance of 5 m, the visual acuity of each eye is examined separately, while closing the other eye with an opaque shield. Signs on the table indicate the end of the black pointer. They propose to read the signs of the table, starting with the largest ones. Visual acuity corresponds to the last row, the signs of which the subject reads completely or does not distinguish between 1-2 characters in it. The number around this series indicates visual acuity. If the subject does not read the signs of the first row, then his visual acuity is less than 0.1. In these cases, to determine visual acuity, the person under investigation is brought to the table or individual signs approach to it (ring with a gap, black sticks on a white background), equal in magnitude to the signs of the upper row of the table, noting the distance at which he begins to distinguish them. Every 0.5 m corresponds to a visual acuity of 0.01. So determine the visual acuity from 0.09 to 0.01. With a lower visual acuity, it is suggested to distinguish the fingers or the movement of the examining hand. The distinction of hand movement at a distance of 30 cm in front of the eye corresponds to a visual acuity of 0.001. If the patient feels only light, then visual acuity is referred to as light sensation. With complete blindness, visual acuity is 0. The results of the study are recorded separately for the right and left eyes.

Visual acuity - the degree of distinguishing the boundaries and details of the objects in question. Visual acuity is one of the most important functions of the visual analyzer, which largely determines the ability to navigate in the surrounding space. The physiological basis of visual acuity is the contrast, or difference, sensitivity, i.e., the ability of the eye to notice differences in the brightness of the compared fields. Thus, a bright spot on a bright background becomes visible for the first time only when its brightness changes from the background brightness.

Visual acuity is usually characterized by the minimum gap between two objects or points at which the eye is still able to see them separately. To separate two points separately, it is necessary that between their images on the retina there remains a space, the excitation of which causes a feeling different than the excitation of those places onto which the images of these points are projected. The final process of recognizing the details and properties of the subject under consideration is due to the differentiation activity of the cerebral cortex. Along with the fractional analysis of light stimuli, this process includes the connection (synthesis) of the latter with other stimuli, primarily tactile and proprioceptive. In the act of visual perception "not only other feelings but also the activity of our thinking join our eye" (F. Engels). This explains the fact that after birth, the child’s visual acuity develops gradually and usually reaches a normal level only by 6–8 years.

A practical measure of visual acuity is considered to be the reciprocal of the angle of view (Fig. 1), i.e. the angle formed by the rays coming from the edges of the object under consideration or from the two points considered (L and B) to the nodal point of the eye (A ') in In this case - the angle of the battery. The smaller the angle of view, allowing separate vision of two points, the greater the visual acuity. For most people, the minimum value of this angle is equal to one minute (G), therefore this value is considered to be the norm, and the visual acuity of the eye, which has the smallest angle of view in 1 ', is normal visual acuity.


Fig. 1. Diagram of the angle of view.


Fig. 2. Dependence of visual acuity on the place of the retina: the solid line is the sharpness of the cone (daytime) vision, the dotted one is the sharpness of the rod (twilight) view, the shaded rectangle is the area of ​​the blind spot.

The most perfect function of distinguishing the details of objects is the central fossa of the retina (see). As the distance from the center to the periphery of the retina increases, visual acuity for cone vision decreases sharply (Fig. 2). A significant effect on visual acuity is the state of refraction of the eye. When astigmatism, myopia, high farsightedness, visual acuity is significantly reduced compared with the visual acuity of an emmetropic eye, since fuzzy images of the objects in question are obtained on the retina. The clarity of images on the retina and, consequently, the visual acuity is somewhat impaired by a too wide and too narrow pupil, the optimum visual acuity is noted with a pupil with a diameter of 3 mm (V. K. Verbitsky, S. M. Brailovsky). Some improvement in visual acuity is observed when the object is monochromatic (for example, yellow), but not by mixed light (V. B. Weinberg and E. A. Lapinskaya).

Of great practical importance is the effect of light intensity on visual acuity.

When distinguishing black objects on a white background, visual acuity reaches the highest level only when illuminated in thousands of suites. When using white objects on a black background, other relationships are observed: visual acuity reaches a maximum when illumination is only 5-6 lux, and with further increase in illumination it decreases (E. V. Klenova).

Adaptation of the eye also affects visual acuity (see). Visual acuity worsens if the eye has been adapted to luminances less or significantly greater than the brightness of the test field. S.V. Kravkov et al. established the dependence of visual acuity on the central nervous system. This is indicated by changes in visual acuity when illuminating the second eye, under the influence of auditory stimuli and conditioned reflex changes.

For the study of visual acuity use special tables, which bear test signs of various sizes (letters, numbers, hooks, rings) - optotypes. The construction of modern tables is based on the principle proposed by Snellen (N. Snellen) in 1862. Optotypes are designed so that from a certain distance a detail of the sign would be visible from an angle of view of 1 ', and the whole sign - of an angle of view of 5 ', while the detail of the sign is understood as the thickness of the strokes of which this optotype is composed, as well as the gap between the individual strokes that are part of the sign (Fig. 3). The table consists of several rows, with signs of equal size arranged in each row. On the side of each row is the distance from which the stroke of this sign is visible at an angle of 1 '. Knowing this distance and the distance from which the researched recognizes this sign, it is easy to determine visual acuity using the formula: V = d / D, where V is visual acuity, d is the distance at which the subject is examined from the table, D is the distance from which the bar is This sign is visible at an angle of 1 '.


Fig. 3. Snellen optotypes: 1 - letter, 2 - hook.

In the USSR, the most common tables are the Golovin-Sivtsev tables (Fig. 4), in which there are 12 rows of characters — letters and rings with a gap (Landolt optotypes). When examining at a distance of 5 m, the upper row of these tables corresponds to a visual acuity of 0.1, and the tenth row corresponds to a normal visual acuity of 1.0. Thus, when going from top to bottom from one row to another, the values ​​of visual acuity increase in arithmetic progression - 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0, 8, 0.9 and 1.0. The bottom two rows — eleventh and twelfth — serve to determine visual acuity higher than 1.0 (1.5 and 2.0).


Fig. 4. Tables Golovin - Sivtseva for determining visual acuity in the apparatus for their illumination, designed at the Institute of Eye Diseases. Helmholtz.

The tables are placed in the Roth illumination apparatus in a modification of the Institute of Eye Diseases. Helmholtz with an electric lamp 40 W, closed from the side of the investigated opaque shield. This creates a relatively uniform illumination of tables in 700 lux. The illuminator is strengthened on the wall so that its lower edge is at a distance of 120 cm from the floor. During the study, the patient should keep his head straight, the eyelids of both eyes should be open. The unexplored eye is covered with an opaque white shield. Within 2-3 seconds, they show with a pointer a sign on the table and ask the researcher to name it. In evaluating the results of the study, the concepts of complete and incomplete visual acuity are used. With full visual acuity, all signs in the corresponding row are correctly researched. If in the rows of the table corresponding to visual acuity of 0.3, 0.4, 0.5, 0.6, one sign is not recognized, and in the rows of corresponding visual acuity of 0.7, 0.8, 0.9, 1, 0, - two signs, visual acuity is assessed for this series as incomplete.

To determine visual acuity of less than 0.1, the patient gradually approaches the table (intervals of 0.5 m) until he correctly names the signs of the upper row. Visual acuity is assessed by the above formula. For example, if the subject sees signs from a distance of 3 m, visual acuity is 0.06 (3m / 50m). But it is better to use a set of optotypes of B. L. Polyak to determine visual acuity less than 0.1. The set consists of 6 ring and 6 three-line optotypes of various sizes pasted on cardboard sheets. The dimensions of optotypes are calculated so that the thickness of the lines and the width of the gaps correspond to visual acuity of 0.09, 0.08, 0.07, 0.06, 0.05 and 0.04 for a distance of 5 m. If the visual acuity of the subject is below 0, 04, it is checked from a distance of 2.5 m. When determining visual acuity below 0.1, an optotype is placed in an apparatus for illuminating tables.

In the tables for the study of visual acuity, based on the principle of arithmetic progression, the difference in visual acuity during the transition from one series to another is very uneven. So, during the transition from the first row to the second (0.1 and 0.2), visual acuity increases by 2 times, and during the transition from the fifth row to the sixth row (0.5 and 0.6) - only 1.2 times. In this regard, the tables were made according to the principle of a geometric progression. Of these, the greatest practical application is the table of V. E. Shevaleva.


Fig. 5. Table for determining visual acuity in children of preschool age.

To determine visual acuity in children of preschool age, tables with pictures are used (Fig. 5). Before the research, the child is usually taken to the table and asked to name the items depicted on it so that he can get comfortable with what is required of him. During the determination of visual acuity, children quickly get tired. Therefore, in the study of visual acuity, starting from the top row of the table, only one picture is shown to the child in each row. If he cannot name it, then all other pictures of the given row are indicated for recognition, then above the arranged row, and so on, until most of the characters in the same row are correctly named. This series will determine the visual acuity of the child under study.

Using the above tables, visual acuity for distance is determined. There are, in addition, tables for the study of visual acuity at close range. They consist mostly not of individual numbers or letters, but of several printed texts, differing from each other in the size of letters. These tables are usually used when assigning points for reading. A number of authors [Ohm (J. Ohm), Gunther (G. Gunther), and others] proposed an objective method for determining visual acuity using optokinetic nystagmus. The latter occurs only when the objects moving in front of the eye are different. This method is especially valuable in cases of detection of aggravation or examination, when subjective methods of visual acuity research are not reliable enough.

Vision 1.0. What does it mean?

By visual acuity is meant the ability of the human eye to recognize two different points in space, located at a distance from each other. The measure of the work of an eye is the angle of view created by a pair of rays emanating from the borders of the object in question. The smaller it is, the greater the sharpness of the eyes. Normally, the indicator should be equal to one, in this case, patients can easily distinguish ten lines of the Sivtsev table at a distance of five meters.

Sight indicator 1

What does visual acuity mean? It is important to understand that this is a normal level of vision (or 100%). According to the standards, an eye with such an indicator is able to distinguish two separate points with an angle between them of 1 minute or 1/60 of a degree. In Western terminology, this value is equivalent to 20/20.

If this value is less than one, then treatment is necessary.

Check Tables

For the diagnosis used special posters. They may contain images of various patterns, letters, badges or hooks.

  • The most popular among Russian ophthalmologists is a poster with the image of letters (Sivtsev's table).
  • Sometimes doctors use the Golovin table, which shows rings with breaks.
  • When checking children, ophthalmologists prefer the Orlova poster with different pictures.

Letters or pictures are located on twelve lines, while their size decreases with each line (starting from the top and going down lower and lower). On the left side of each line, the symbol “D” indicates the distance from which, with good vision, the subject should see all the characters. For the top line it is 50 meters, and for the bottom one 2.5. On the right side of the lines, the letters “V” indicate visual acuity indicators that are correct when the subject reads characters from 5 meters. This indicator is 2 if the subject distinguishes between the bottom line and 0.1 if he sees only the first.

How is the diagnosis

Surveyed put five meters from the poster. Further, the doctor conducts the diagnosis of each eye separately. He starts from the right and then goes to the left.

  1. First, the ophthalmologist asks to name a series of letters located on the tenth line of the table. The correct answer means that the indicator of visual acuity is equal to one.
  2. If the subject calls the letters on the 10th line incorrectly or often makes mistakes, the doctor moves to the top, and with the correct answer goes lower and lower until the patient starts to make mistakes again.
  3. The last line, which he can distinguish and will indicate visual acuity (if he sees all 12 lines, then this value will be 2).

In ophthalmology, people are known who have developed visual abilities of up to five to six units. This was manifested in the fact that they clearly saw objects located at a distance of 100 meters and beyond. There were exceptional cases in the history of medicine when this figure was sixty units and a person could see the rings of Saturn in the starry sky, which, with an average value (ie, one), can only be seen using a telescope.

Patient record

After diagnosis, the doctor makes entries in the patient's card. Most often they are the following: ViS OD and ViS OS. Decrypt these characters is quite simple. The first entry relates to the right eye, the second, respectively, to the left. In the normal state of the visual function of both eyes, 1.0 will be written opposite each entry.

Snellen table

Snellen's table is more often used by foreign countries, especially the United States. Just like on Sivtsev's poster, large letters occupy the top lines and their size decreases downwards.

The poster is made so that if a person has 100% vision, then he can read each line from a distance of 60, 36, 24, 18, 12, 9, 6 and 5 meters (which equals 100, 70, 50, 40, 30, 25 and 20 feet respectively) up to the red line.

To diagnose the subject, they are seated at a distance of 6 m (20 feet) from the poster. He is asked to close one eye, and others to read the letters. The bottom row, which the patient can distinguish and will indicate the sharpness of his vision.

  • Normally, this indicator is 6/6 (or 20/20). In this case, the subject can read the 8th line from a distance of 6 m. (20 feet).
  • If he sees only 5 lines, then the visual acuity on the Snellen scale is 6/12 (20/40). В этом случае, чтобы прочитать 5 строку ему нужно подойти к плакату на расстояние 6 м. (20 футов), в то время как обследуемый с хорошим зрением увидит эту строку с 12-и метров (40 футов).

Если с расстояния в 6 метров человек видит только одну, первую строчку, то в Соединенный Штатах его признают «законно слепым».

Summarizing, we can say that if a person has a normally developed visual apparatus, then his visual acuity will most often equal one, sometimes two.

Many people confuse visual acuity with refractive ability. The first value is represented only by positive values, which vary from zero to infinity. Moreover, one is an average value, and two is a good indicator. Refraction of the eye is measured by diopters, the indicators of which can be both negative and positive. Negative dioptries indicate that a person develops myopia (myopia), and positive values ​​- hypermetropia (farsightedness). The normal value of refraction is zero (indicates good eye health).

Eye examination by an ophthalmologist

To diagnose doctors use special signs, which depict letters and pictures. Most often in the office of the oculist there is a poster for an eye test, designed by Sivtsev. It consists of twelve lines, each row shows letters of different sizes. From above the largest font is used, it gradually decreases.

Prerequisites for research

In order for the diagnosis to be carried out without errors, not only the patient, but also the doctor must observe several conditions. Otherwise, the reliability of the results will be low.

The plate for checking visual acuity should be evenly illuminated. Sometimes outdoor lights are used for this purpose, but it is better to place a poster in the Rota apparatus. It is equipped with mirror machines that provide the same lighting. In the office of the oculist should be light.

Definition of visual acuity

The doctor examines in turn the condition of each eye. First, the right is checked, then the left. The patient sits at a distance of five meters from the table. Diagnosis takes place in the following sequence:

  • First of all, the optometrist asks to name the letters located on the tenth line. If everything is called correctly, then the vision is equal to one,
  • When making numerous mistakes during the "study" of the tenth row, the doctor rises to the top of the poster and begins to gradually decline until the patient makes a mistake again,
  • The last line that a person could see and determines visual acuity.

In practice, ophthalmologists have come across people who have developed the abilities of their eyes and increased their sharpness to five units. They clearly saw objects located at a distance of one hundred meters. There were completely unique cases. For example, one person developed sharpness up to sixty points and was able to make out rings on the planet Saturn.

How is the procedure for determining the sharpness of the eye, learn by watching the video

Refraction of vision

Under this concept lies the ability of the optical system to refract light rays. The power of refraction depends on the curvature of the lens and the cornea. There are several types of refraction:

  • Emmetropia. The system works without deviations,
  • Myopia. A person cannot distinguish objects located at a distance,
  • Hypermetropia. The patient is problematic to consider objects near.

When hypermetropia is detected, the eyes have a weak refractive power and the rays “meet” behind the retina. For this reason, the visual apparatus has to strain, even when a person looks into the distance. In myopia, the eyes have great refraction, the light rays intersect in front of the retina. Both anomalies adversely affect visual acuity. Pathologies have three degrees:

  • Weak. The deviation in refraction does not exceed three diopters,
  • Average. From four to six
  • High. More than six diopters.

Vision refraction determination

For the analysis of refractive power, a procedure called refractometry is assigned. The doctor uses an optical lens or refractometer. Indicators in each eye may vary. If one eye is nearsighted, and the second is a far-sighted patient, anisometropia is diagnosed.

Retinoscopy is also widely used to determine refraction. The essence of the technique lies in the fact that the optometrist and the patient are sent to a darkened room, where the doctor shines in the eyes of the skiascope and analyzes the movement of the shadow. Its direction depends on the strength of refraction. Most often, the method is used to diagnose abnormalities in children.

Instruments such as an autorefractometer or aberrometer are used to automatically detect refraction. The first helps to detect astigmatism, and to assess the focus of light rays. With the help of the second, the doctor studies the internal environment of the eye.
Back to table of contents

Possible deviations

There are a number of ophthalmologic diseases that occur when the refraction of the visual apparatus is impaired.

A person is not able to view objects at a distance, since the picture falls not on the retina, but in front of it. The image is blurry, because the optical system does not match the length of the eye.

Myopia is acquired or congenital, in some cases, the progression of the disease. The main goal of corrective measures in identifying anomalies is to weaken the power of refraction. The main signs of the disease:

  • Problems with the far review,
  • Blurred outlines of objects
  • Split image.

Hypermetropia

A person is not able to see objects that are nearby, because the picture is projected behind the retina due to reduced refractive power. The older the patient, the worse his eyesight. As the muscles weaken with age, and the lens loses its elasticity.

  • Accommodation problems
  • Blurred vision
  • Eyes get tired quickly
  • Discomfort,
  • Perhaps the development of strabismus or amblyopia.

Hyperopia is divided into:

  • Functional. Detected by accommodation paralysis,
  • Simple. It is diagnosed if the organ of vision is shorter than is required to focus the light rays on the retina,
  • Pathological. Observed with a variety of eye injuries.

Astigmatism

This anomaly is accompanied by a violation of the lens and the cornea. As a result, the optical power is uneven, part of the image is focused in front of the retina, the other directly on it. Astigmatism is divided into two types: corneal and lens-shaped.

Depending on the "origin" of the disease are classified into:

  • Congenital. Diagnosed in children. If it does not exceed 0.5 diopters, it is not dangerous for the eyes. Has the degree of astigmatism exceeded one? Immediate treatment is required because there is a drop in the sharpness of the eyes,
  • Acquired. Developed with the formation of scars on the cornea. They may be a consequence of injury or surgery.

Entries in the personal medical record

After conducting diagnostic activities, the doctor makes an entry in the outpatient card. Most often there can be seen such mysterious inscriptions as ViS OD or ViS OS. In fact, this is not spyware encryption, so it will not be difficult to understand it. The first entry reflects the state of the right eye, the second - the left.

If the organ of vision works without disturbances, then the number one will be indicated opposite each line.

Visiting the office of an ophthalmologist, you will learn the health of your eyes. Vision unit means that you have no problems with refraction. However, in order to maintain eye health for a long time, it is important to treat them carefully. Do not be lazy to periodically undergo medical examinations, take vitamins, balance your diet and walk more. Remember that the organ of vision is the main source of information, so take care of it!
Back to table of contents

be careful

Recently, vision restoration operations have gained immense popularity, but not everything is so smooth.

These operations incur major complications, besides, in 70% of cases, on average one year after the operation, the vision begins to fall again.

The danger is that the glasses and lenses do not act on the operated eyes, i.e. a person begins to see worse and worse, but he can do nothing about it.

What do people with low vision do? Indeed, in the era of computers and gadgets, 100% vision is almost impossible, unless of course you are not genetically gifted.

But there is a way out. The Ophthalmological Research Center of the Russian Academy of Medical Sciences managed to develop a drug that completely restores vision without surgery (myopia, hyperopia, astigmatism and cataracts).

Currently, the Federal Program "Healthy Nation" is underway, under which one citizen of the Russian Federation and the CIS is given one package of this drug. IS FREE! Detailed information, look at the official website of the Ministry of Health.

The most perfect function of distinguishing the details of objects is the central fossa of the retina (see). As the distance from the center to the periphery of the retina Oz. for the cone the sight drops sharply (Fig. 2). Significantly affects O. h. state of refraction of the eye. With astigmatism, myopia, high farsightedness O. h. significantly reduced compared with the visual acuity of an emmetropic eye, since fuzzy images of the objects in question are obtained on the retina. Distinctness of images on a retina and, therefore, O. z. somewhat too wide and too narrow a pupil, optimal O. h. it is noted at a pupil with a diameter of 3 mm (V.K. Verbitsky, S.M. Brailovsky). Some improvement in O. h. observed when the object is illuminated with monochromatic (for example, yellow), and not with mixed light (V. B. Weinberg and E. A. Lapinskaya).

Of great practical importance is the influence of the intensity of illumination on an optical system.

When distinguishing black objects on a white background. O. h. reaches its highest level only when illuminated in thousands of suites. When using white objects on a black background, different ratios are observed: O. h. reaches a maximum at an illumination of only 5-6 lux, and with a further increase in illumination decreases (E. V. Klenova).

Adaptation of the eye also affects visual acuity (see). O. h. worsens if the eye was adapted to luminances less or significantly greater than the brightness of the test field. S.V. Kravkov et al. established the dependence of O. h. from the central nervous system. This is indicated by O.'s changes. when illuminating the second eye, under the influence of auditory stimuli and conditioned reflex changes.

For research O. z. use special tables on which test marks of various sizes are applied (letters, numbers, hooks, rings) - optotypes. The construction of modern tables is based on the principle proposed by Snellen (N. Snellen) in 1862. Optotypes are made in such a way that from a certain distance the detail of the sign would be visible from the angle of view in 1 ′, and the whole sign - from the angle of view of 5 ′, While the detail of a sign is understood as the thickness of the strokes of which this optotype is composed, as well as the gap between the individual strokes that make up the sign (Fig. 3). The table consists of several rows, with signs of equal size arranged in each row. On the side of each row is the distance from which the stroke of this sign is visible at an angle of 1 ′. Knowing this distance and the distance from which the subject learns this sign, it is easy to identify O. h. according to the formula: V = d / D, where V is visual acuity, d is the distance at which the subject is examined from the table, D is the distance from which the stroke of this sign is seen from an angle of view of 1 ′.

In the USSR, the most common tables are the Golovin-Sivtsev tables (Fig. 4), in which there are 12 rows of characters — letters and rings with a gap (Landolt optotypes). When examining at a distance of 5 m, the upper row of these tables corresponds to a visual acuity of 0.1, and the tenth row corresponds to a normal visual acuity of 1.0. Thus, when going from top to bottom from one row to another, the values ​​of O. h. increase in arithmetic progression - 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0. The two bottom rows — the eleventh and twelfth — serve to define O. z. above 1.0 (1.5 and 2.0).

Fig. 4. Tables Golovin - Sivtseva for determining visual acuity in the apparatus for their illumination, designed at the Institute of Eye Diseases. Helmholtz.

The tables are placed in the Roth illumination apparatus in a modification of the Institute of Eye Diseases. Helmholtz with an electric lamp 40 W, closed from the side of the investigated opaque shield. This creates a relatively uniform illumination of tables in 700 lux. The illuminator is strengthened on the wall so that its lower edge is at a distance of 120 cm from the floor. During the study, the patient should keep his head straight, the eyelids of both eyes should be open. The unexplored eye is covered with an opaque white shield. Within 2-3 seconds, they show with a pointer a sign on the table and ask the researcher to name it. When evaluating the results of a study, use the concepts of complete and incomplete visual acuity. At full O. z. All the characters in the corresponding row are correctly labeled. If in the rows of the table corresponding to visual acuity of 0.3, 0.4, 0.5, 0.6, one sign is not recognized, and in the rows of corresponding visual acuity of 0.7, 0.8, 0.9, 1, 0, two characters, O. h. estimated for this series as incomplete.

Deviations

Myopia or myopia is a disease in which a person does not see well into the distance. In this case, the image is not focused on the retina, but in front of it. Vision becomes so blurred due to the fact that the optical system no longer corresponds to the length of the eye.

With myopia, the eyeball increases.

Myopia is congenital and acquired. Sometimes it can progress. Therefore, the goal of vision correction in myopia is to weaken the refractive power of the eyes so that the image is focused on the retina.

  • The distant sight worsens,
  • The contours of objects become fuzzy,
  • Objects can merge with each other, double, distort,
  • Near vision persists.

There is such a thing as false myopia. In this case, a spasm of accommodation occurs due to the overstrain of the lens muscle. False myopia is treated with medications and special exercises for the eyes.

How to treat accommodation spasm will tell this article.

Myopia is very dangerous because it can lead to degeneration and detachment of the retina.

Loading...