Selection of spectacle vision correction. Professional advice on choosing vision glasses. Does frame matter for spectacle correction?

Vision is the greatest value for any of us. Vision gives us 80% of information about the world around us. The ability to see is perhaps the most important of all perceptions of the surrounding world.

Scientists, explaining the phenomenon of vision, often compare the eye to a camera. A normal human eye can see very far clearly. Light rays falling on the eye from an object pass, refracted in a certain way, through the optical system of the eye and draw a reduced and inverted image on the retina. A person sees objects not upside down thanks to the work of the visual centers of the brain.

Our eyes are capable of distinguishing about ten million gradations of light intensity and about seven million shades of colors. To see, a person simultaneously uses both his eyes and his brain, and for this, a simple analogy with a camera is not enough. Every second, the eye sends about a billion nerve impulses to the brain (more than 75 percent of all information we perceive).

Selecting glasses for vision correction is an extremely important matter. Incorrectly chosen glasses can cause significant harm to health and significantly impair vision. All over the world there is a special profession - optometrist - these are specialists with higher education, specially trained to correctly select vision correction products. Unfortunately, such specialists are not trained in our country. Our ophthalmologists select glasses. The problem is that ophthalmology offices in district clinics often do not have at their disposal all the necessary equipment to fully determine all parameters of vision.

The purpose of this work is to study various visual impairments and means of their correction.

To achieve this goal, it was necessary to solve the following tasks:

1. To study optical defects of the eye, disturbances of binocular vision and means of their correction,

2. Consider methods of vision examination when selecting glasses,

3. Study methods for selecting spectacle correction using specific examples.

1.1 Optical defects of the eye

There are three types of clinical refraction: emmetropia, hypermetropia and myopia. Only the first provides (at rest of accommodation) a clear image of distant objects on the retina and, therefore, normal vision. The other two types of refraction are combined with the term “ametropia”; with such refraction, the image of objects located at an infinite distance from the eye appears unclear on the retina, in circles of light scattering.

In hypermetropia, the focal point lies behind the retina, the deterioration of vision is caused by insufficient refractive power of the eye, and, therefore, can be corrected to some extent by the tension of accommodation. In myopia, it is caused by excess refractive power of the eye and, therefore, cannot be corrected by accommodation.

For both types of ametropia, vision can be corrected by placing lenses in front of the eye: for hyperopia - convex (positive), for myopia - concave (negative). Lenses move the back focus of the eye onto the retina and make the image of objects sharp (Fig. 1).

Rice. 1. Correction of ametropia for hypermetropia (a) and myopia (b).

Visual defects vary not only in type, but also in degree. The further the focus is from the retina, the higher the degree of ametropia. The degree of ametropia is measured by the refractive power of the lens that corrects the visual defect, i.e., placing the focus on the retina.

If myopia is corrected with a concave lens - 1.0 diopters, then myopia is said to have a degree of 1.0 diopters. If hyperopia is corrected with a +4.0 D convex lens, then the hyperopia is said to have a degree of 4.0 D.

Visual defects that can also be corrected with stigmatic lenses include presbyopia, or age-related weakening of accommodation. With presbyopia, it is impossible to obtain a clear image of nearby objects on the retina. Usually we are talking about objects of visual work - texts, computer monitors. In order to make the object clear, a positive (convex) lens is placed in front of the eye. It shifts focus to the retina. This lens (usually a power of 0.5 to 3.0 D) takes on first part and then all of the work of accommodation. Presbyopic glasses are used only for close work. For simultaneous vision at distance and near, special lenses are used that have different refraction in different parts - bifocal, trifocal, multifocal.

Rice. 2. Refraction in different meridians of an astigmatic eye

Eye astigmatism also requires correction. Astigmatism can accompany both emmetropia and ametropia. This happens when the refractive surfaces of optical media (cornea and lens) are not spherical, but elliptical or toric. In this case, the eye combines, as it were, several refractions: if you look at the astigmatic eye from the front and mentally dissect it with planes passing through the anterior pole of the cornea and the center of rotation, it turns out that the refraction in such an eye smoothly changes from the strongest in one of the sections to the weakest in another section, perpendicular to the first (Fig. 2).

Within each section, the refraction remains constant (this distinguishes correct astigmatism from incorrect one). The sections (meridians) in which the refraction is greatest and least are called the main meridians of the astigmatic eye.

Based on the combination of refractions in the main meridians, types of astigmatism are distinguished, and based on their relative position, types of astigmatism are distinguished.

There are 5 types of astigmatism:

1 - complex hypermetropic (CH) - a combination of hypermetropia of varying degrees;

2 - simple hypermetropic (H) - a combination of hypermetropia in one meridian with emmetropia in the other;

3 - mixed (NM or MN) - a combination of hypermetropia in one meridian with myopia in the other;

4-simple myopic (M) - a combination of emmetropia and myopia;

5 - complex myopic (MM) - a combination of myopia of varying degrees in two meridians.

There are 3 types of astigmatism:

I - direct type astigmatism - the meridian with stronger refraction is located vertically or in a sector ± 30° from the vertical;

II - reverse type astigmatism - the meridian with stronger refraction is located horizontally or in a sector ± 30° from the horizontal;

III - astigmatism with oblique axes - both meridians lie in sectors from 30 to 50° and from 120 to 150° on the TABO scale.

Optical correction of astigmatism is carried out with astigmatic cylindrical and spherocylindrical lenses. For simple types of astigmatism, a cylindrical lens is placed in front of the eye, the axis of which is parallel to the emmetropic meridian. As a result, in this meridian the rays continue to converge on the retina, and in the second meridian they are converged on the retina using a lens. The conoid turns into a cone, the image on the retina becomes clear.

For complex and mixed types of astigmatism, correction is carried out using a combination of spherical and cylindrical lenses. First, a spherical lens is placed in front of the eye, compensating for ametropia in one of the meridians (usually the one that has a lower absolute value of ametropia), then a cylindrical lens is added to it, corresponding to the astigmatic difference, the axis is placed parallel to the previously corrected meridian.

It follows that the path of rays in an astigmatic eye can be corrected by two combinations of spherical and cylindrical lenses: in each of them, the spherical lens is selected according to the refraction of one of the main meridians. From these combinations, for complex astigmatism, you should choose the one in which the spherical and cylindrical lenses have the same sign, and for mixed astigmatism, the one in which the value of the spherical component is less.

1.2.1 Strabismus

Strabismus is a deviation of the visual line of one of the eyes from the joint point of fixation.

If this line deviates by the same angle with equal directions of gaze, then strabismus is called concomitant. If the deviation in any direction of gaze decreases, increases or disappears, then strabismus is called paralytic.

Based on the direction of deviation of the eye, strabismus is classified into convergent, divergent and vertical. Based on whether one eye constantly deviates or alternately one or the other, monolateral (right- or left-sided) and alternating strabismus are distinguished. Finally, a distinction is made between obvious (heterotropia) and hidden (heterophoria) strabismus. With obvious strabismus, one of the eyes is constantly deviated from the point of fixation. With hidden strabismus, deviation of one eye appears only when the vision of the two eyes is separated, for example with the help of a shutter.

A careful study of muscle balance shows that hidden strabismus is present in most people, but in only a few it causes visual disturbances.

To compensate for strabismus, especially hidden ones, glasses with prismatic action can be used. In order to compensate for strabismus using a prism, it is necessary to place a prism in front of this eye, with its base directed in the direction opposite to the deviation of the eye. The power of the prism should correspond to the angle of strabismus. Thus, with convergent strabismus, the base of the prism should be directed towards the temple, and with divergent strabismus, towards the nose (Fig. 3).

Rice. 3. Actions of prisms with convergent ( A) and divergent ( b) strabismus.

The power of the prism in prism dioptres (srad) must be twice the angle of deviation of the eye in degrees. For example, convergent strabismus (esotropia) with an angle of 10° requires the installation of a 20 diopter prism with the base towards the temple.

To ensure that the prisms are not too thick, they are usually “laid out” on two eyes, but it is necessary that the total effect of the two prisms corresponds to the desired one.

It should be kept in mind that prisms do not correct strabismus. They only compensate for the relative displacement of the images on the retinas of the two eyes caused by strabismus.

Aniseikonia is a vision disorder in which the images on the retinas of the two eyes are not the same size. If the difference in size is the same in all directions, then aniseikonia is called general; if it is increased only in one direction, then it is meridional. The amount of aniseikonia is measured as a percentage. To correct aniseikonia, lenses or lens systems that combine eikonic action with other types of optical action are often used.

The main device for vision correction is glasses. According to their optical effect, spectacle lenses are divided into stigmatic (spherical), astigmatic, prismatic and eikonic (afocal). The first and second types can be combined with the third and fourth.

According to the position of the main focus, stigmatic and astigmatic lenses are divided into collective, denoted by the “+” sign, and diverging, denoted by the “-” sign.

According to the shape of the refractive surfaces of the lenses, there are:

1) bi-shape - both surfaces of the lens are convex or concave;

2) floating shapes - one of the surfaces is flat, the other is convex or concave;

3) menisci - one surface is convex, the other is concave. Currently, bi- and plan-shaped lenses are almost never used, since they have high astigmatism of oblique beams.

Depending on the number of optical zones, lenses can be single- or multifocal. Multifocal lenses are used to improve the clarity of vision of objects located at different distances, and are used in cases of weakened accommodative ability.

1.4.1 Skiascopy

Skiascopy is a method of objective study of clinical refraction, based on observation of the movement of shadows obtained in the area of the pupil when the latter is illuminated using various techniques.

The doctor illuminates the pupil of the eye being examined with an ophthalmoscope mirror and, turning the apparatus around a horizontal or vertical axis in one direction or the other, observes the nature of the movement of the shadow against the background of a pink reflex from the fundus of the eye in the area of the pupil. During skiascopy with a flat mirror from a distance of 1 m, in the case of hypermetronia, emmetronia and myopia less than -1.0 diopters, the shadow moves in the same direction as the mirror, and with myopia greater than -1.0 diopters - in the opposite direction. In the case of using a concave mirror, the relationships are reversed.

To establish the degree of refraction, the method of neutralizing the movement of the shadow is usually used. For myopia greater than -1.0 diopters, negative lenses are applied to the eye being examined, first weak and then stronger (in absolute value) until the movement of the shadow in the pupil area stops. In cases of hypermetropia, emmetropia and myopia less than -1.0 DNT, a similar procedure is performed with positive lenses.

To clarify refraction in case of astigmatism, you can use bar-skiascopy or strip-skiascopy. The study is carried out using special skiascopes that have a light source in the form of a strip that can be oriented in different directions. Having installed the light strip of the device in the desired position, skiascopy is carried out according to the general rules in each of the found main meridians, ensuring that the movement of the striped shadow stops.

Cylindroskiascopy allows you to clarify the data obtained from skiascopy. First, a regular skiascopy is carried out with rulers, the position of the main meridians of the astigmatic eye and the power of the lenses are approximately determined, when used, the movement of the shadow in each of them stops. The patient is put on a trial frame and a spherical and astigmatic lens is placed in the socket located opposite the eye being examined, which should ensure that the shadow moves simultaneously in both main meridians, and skiascopy is performed in them. The cessation of movement of the shadow in one and the other direction indicates that the skiascopic refractive indexes are determined correctly. If the shadow does not move in the direction of the cylinder axis, then the cylinder axis is not installed correctly.

Refractometers are used to objectively determine the refraction of the eye, including astigmatism. They are based on the study of a luminous mark reflected from the fundus of the eye.

Type I refractometers are based on obtaining a sharp image of a mark on the bottom of the eye being examined. The measurement of refraction in them is achieved by focusing by smoothly changing the convergence of the rays in the projection system.

Type II refractometers are based on the Scheiner phenomenon - a split image projected through different parts of the pupil. In this case, refraction measurement is achieved by combining two images also by smoothly changing the convergence of the rays.

The examiner observes both images of the mark through the eyepiece. Only with emmetropia does the picture look symmetrical: both horizontal and vertical stripes are opposite each other. With ametropia, the strips diverge and must be combined using a compensating optical system. Refraction is measured separately in two main meridians. On the side wall of the device there are two handles: for rotating the mark (degree handle) and for compensating ametropia (diopter handle). Two scales are used for counting: a degree scale, indicating which meridian the stamps are currently located in, and a diopter scale, indicating the refraction of the eye in a given meridian.

There are three concepts of visual acuity:

1) visual acuity according to the smallest visible is the size of a black object (for example, a dot), which begins to be distinguished against a uniform white background;

2) visual acuity according to the least discernible is the distance by which two objects must be removed for the eye to perceive them as separate;

3) visual acuity according to the least recognizable - this is the size of the detail of an object, for example a stroke, letter or number, at which this object is unmistakably recognized.

In optometry, only the second and third types of determining visual acuity are used. To do this, use special black characters on a white background - optotypes.

To determine visual acuity based on the smallest detectable feature, the Landolt ring optotype is used. It is a ring with a square gap. The thickness of the ring, like the width of the gap, is equal to 1/5 of its outer diameter. The rupture can have one of 4 or, less commonly, one of 8 directions. The examinee must indicate the direction of the rupture.

To determine visual acuity by the least recognizable, letters, numbers or silhouette pictures are used, and the ratio of the detail of the optotype (the thickness of the letter or number, the size of the detail of the picture) to its entire size (the side of the square in which the sign is inscribed) should be 1:5.

Visual acuity is determined without correction and with optical correction (i.e., with a lens or lens system that best corrects ametropia).

Lens fitting is the oldest method of studying refraction. It consists in determining the power of the lens, which, when placed in front of the eye, gives it the highest visual acuity. However, with working accommodation, such visual acuity can be provided not by one, but by several spherical lenses of different strengths. Only if accommodation is turned off, for example, with the help of drugs that paralyze it, can you choose one lens that gives maximum visual acuity. To determine refraction, it is necessary to select the weakest negative and the strongest positive of the spherical lenses that provide maximum visual acuity.

But even in this way it is not always possible to identify static refraction, since there is usually some constant tension (habitual tone) of accommodation. Thanks to it, when selecting lenses, myopia is revealed to a slightly greater extent, and hypermetropia to a slightly lesser extent.

It is more difficult to determine refraction using the lens selection method for astigmatism, since in this case it is necessary to simultaneously determine three components of refraction: the power of the spherical lens, the power of the cylindrical lens and the position of its axis. An error in each of them affects the accuracy of determining the other two. Therefore, before selecting astigmatic lenses based on visual acuity, at least roughly determine the type and degree of astigmatism.

The duochrome test is based on the phenomenon of chromatic aberration in the eye. It lies in the fact that rays with a shorter wavelength (blue-green) are refracted more strongly than with a longer wavelength (red), and, therefore, the focus for blue-green rays is closer to the cornea than for red ones. A myopic eye should see more clearly in red light, and a hypermetropic eye should see more clearly in green light.

The subject is shown a luminous display, the left half of which is green and the right half is red. Black optotypes are placed symmetrically on both halves. The subject with a selected lens is asked to look at the color panel and indicate against which background the signs seem clearer or blacker to him: red or green.

If it is red, then the eye setting is myopic and the negative lens should be strengthened or the positive lens in front of the eye should be weakened; if the signs are clearer on a green background, then the eye setting is hypermetropic and the negative lens should be weakened or the positive lens strengthened.

Laser refractometry is based on the phenomenon of interference of coherent rays of light in the eye. Scattered light from a coherent source, for example reflected from a rough metal surface, entering the eye forms a characteristic uneven illumination on the retina, the so-called laser grain. If the eye and the reflective surface move relative to each other, then this shagreen appears to the subject to also move.

The direction of this movement depends on the refraction of the eye being examined: if the eye is hypermetropic, then the shagreen moves in the same direction as the reflective surface; if it is myopic, then in the opposite direction; if it is emmetropic, then it rotates in place, as if “boiling.”

The movement of the eye relative to the screen can be carried out either due to the movement of the subject's head to the sides, or due to the movement of the screen itself. To implement the latter, more convenient method, the screen is made in the form of a slowly rotating drum.

To identify the type and degree of astigmatism, it is necessary to determine the spherical and astigmatic components of the correction, as well as the position of the axis of the astigmatic lens, which ensures maximum visual acuity. To determine astigmatism, so-called astigmatic figures are often used, and when using optotypes, crossed cylinders are used.

The research method is based on the uneven vision of lines of different orientations in astigmatic figures, or, as they are sometimes called, dials, with an astigmatic eye. These figures are used both to identify astigmatism itself and to determine its degree and the position of the main sections. Crossed cylinders are used mainly at the final stage of refraction research to clarify the degree of astigmatism and the position of its main sections, i.e., the strength and direction of the axis of the correcting cylinder.

The radiant figure is a round white board in the form of a dial with a diameter of 18-25 cm, on which thick black rays are applied every 10-30°. The ends of the rays are indicated by numbers. The radiant figure is shown to the subject from a distance of 5-6 m (Fig. 4, a).

If the subject sees all the rays of the figure equally clear or somewhat blurred, then astigmatism is either absent or evenly mixed. To find out which option occurs, you should move the conoid anteriorly by inserting a +1.0 diopter spherical lens. In the absence of astigmatism, the entire figure will become clearer or more blurry. If there is astigmatism, then the two opposing rays or sectors of the figure become more distinct. They correspond to the position of the back focal line and coincide with the direction of the stronger refractive meridian. After this, with the help of spherical lenses, the highest contrast is achieved: maximum clarity of the rays in the highly refractive meridian and maximum blur in the weakly refractive meridian.

It may also be that the entire figure appears very blurred to the examinee. In this case, the entire conoid is located far from the retina, that is, in addition to astigmatism, there is gross spherical ametropia, which must first be corrected with spherical lenses.

So, the radiant figure serves to identify astigmatism and roughly characterize the position of its main sections. For precise correction of astigmatism, other figures are needed: to clarify the position of the cylinder axis - Raubichek's “arrow”, to clarify its strength - the figure of the cross.

eye defect optical correction

Rice. 4. Radiant figure for diagnosing astigmatism ( A) and the arrow-shaped figure of Raubichech to clarify the positions of the main sections of the astigmatic eye ( b).

Raubichek's “Arrow” is a black gable symmetrical hyperbola (Fig. 4, b), the ends of which, if extended, form a right angle.

The hyperbola, about 0.5 cm thick, is placed in a circle with a diameter of 18-20 cm, which can rotate. There is a fixed scale around the circle. The subject is shown an arrow-shaped figure, having established its apex along the meridian that corresponds to a clear sector of the radiant figure. In this case, the subject sees the entire figure blurred, with the exception of a small clear area near the top of the arrow. With careful turns, a clear section of the radiant figure is moved exactly to its top. In this case, the arrow will indicate the position of one of the main meridians of the eye. After this, they begin to determine the degree of astigmatism.

The crossed cylinder was proposed by Jackson and was intended to clarify the strength and position of the axis of the corrective cylinder. Typically, a crossed cylinder with a power of ±0.5 diopters is used.

The force of the correction cylinder is specified as follows. An astigmatic lens (a combination of spherical and cylindrical lenses), found according to skiascopy, refractometry or figure studies, is placed in front of the eye. A crossed cylinder is placed in front of the frame socket in two positions alternately: 1) the axis of the correcting cylinder coincides with the axis of the same name; 2) the axis of the correcting cylinder coincides with the opposite axis of the crossed cylinder.

The subject is asked to look at the table to determine visual acuity and answer the question at what position of the crossed cylinder he sees better: when the same axes coincide or when the opposite axes coincide. In the first case, the cylinder in the frame is strengthened, and in the second case it is weakened by 0.5 or 0.25 diopters. After this, the test is repeated until the result is the opposite. The degree of astigmatism is judged by the cylinder, which gave an uncertain result.

The test with covering the eye (“carpet test”) makes it possible to establish with a high probability the presence of obvious or hidden strabismus. The examiner sits opposite the patient and asks the patient to look intently, without blinking, at some distant object located behind the examiner. At the same time, he alternately covers the patient’s right and left eyes without intervals. If at the moment of opening neither eye makes movements, then most likely there is no strabismus; if there is movement, then there is strabismus. If the movement of the eye when opening (transferring the shutter to the other eye) occurs towards the nose, then the strabismus is divergent, if towards the ear it is convergent.

In the case of obvious strabismus, when opening one of the eyes (leading), both eyes make a quick adjustment movement in one direction, and when opening the other eye (squinting), they remain motionless. In the case of hidden strabismus, when each eye opens, there is a slow movement of only that eye.

The nature of vision with two eyes open can be checked in different ways.

A study using a color test (four-point color apparatus) allows us to identify the presence or absence of binocular vision. The subject observes 4 luminous circles of different colors through filter glasses. The colors of the circles and lenses are selected in such a way that one circle is visible to only one eye, two circles -

only to the other, and one circle (white) is visible to both eyes.

To study muscle balance, the patient puts on a trial frame with lenses that completely correct ametropia. A Maddox cylinder is inserted into one of the sockets in a horizontal position of the axis, into the other -

prismatic compensator with a vertical handle position and zero marks on the scale. The subject is asked to look at a point source of light located at a distance of 5 m from him, and he must indicate on which side of the light bulb there is a vertical red stripe.

If the stripe passes along the bulb, then the patient has orthophoria, if to the side of it - heterophoria. Moreover, if the stripe passes on the same side of the light bulb on which the Maddox cylinder is located, then the patient has esophoria, if on the opposite side, then exophoria.

2.1 Correction of hypermetropia

Example 1. Child, 3 years old. Parents noticed convergent strabismus in the child at the age of 2 years. No previous treatment was carried out. Due to his young age, visual acuity could not be checked. Before the use of cycloplegic drugs, skiascopy revealed hypermetropia of 3.0 diopters in both eyes. After 3-day atropinization, the refraction revealed by skiascopy was equal to: OD +6.5 D, OS +6.0 D. Glasses were prescribed 1.0 diopters weaker than the detected degree of ametropia: OD sph +4.6 D and OS eph +4.0 D. The child willingly wears glasses.

The above example emphasizes that glasses for young children are prescribed based on objective data without subjective verification.

Example 2. 13 years old. During a preventive examination at school, a decrease in visual acuity was revealed to 0.8 in the right eye and 0.7 in the left eye. Before the use of cycloplegics, skiascopy approximately revealed hyperopia of 2.0 diopters in each eye, but spherical lenses of the indicated visual power almost did not improve. After a 3-day installation of a 1% atropine solution, the refraction revealed by skiascopy was +3.0 D in the right eye and +4.0 D in the left eye. Trial selection under conditions of cycloplegia made it possible to clarify the refraction:

VOD = 0.2 with sph + 2.75 D = 0.9,

VOS = 0.1 with sph +3.5 D = 0.8.

After the cycloplegia ceased, correction was monitored using “fogging” according to Sheard. The optimal results were +2.5 diopters in the right eye and +3.0 diopters in the left eye.

VOD = 0.8 with sph +2.5 D = 1.0,

VOS = 0.7 with sph +3.0 D = 0.9.

Glasses are prescribed with such lenses for constant wear. The visual acuity of each eye with glasses was 1.

Example 3. 35 years old. Complains of getting tired quickly when reading:

A study using a Hartinger refractometer revealed ametropia OD +1.5 D, OS +2.0 D. During a trial selection of lenses:

VOD = 1.0 with sph +1.0 D = 1.2,

VOS - 0.9 with sph +1.5 D = 1.2.

The high visual acuity obtained during the trial selection and the age of the patient made it possible to exclude the use of cycloplegia. Since the patient does not experience difficulty viewing distant objects, it was decided to assign him glasses only for working at close range. The addition for near-age lenses to lenses that correct ametropia is +0.5 diopters. Test reading with OD sph +1.5 D and OS sph +2.0 D lenses gave a feeling of comfort. Appropriate glasses are prescribed.

Example 4. 5 years. Decreased vision was discovered in kindergarten.

Atropinization revealed refraction OD - 5.0, OS - 7.0. The fundus picture is characteristic of congenital myopia. Vision with optimal correction:

VОD with sph -5.0 D = 0.6

VOS with sph -7.0 D = 0.5.

Glasses were prescribed for constant wear with hypocorrection of 1.0 diopters.

Binocular visual acuity in them is 0.5

Example 5. 12 years old. During the next examination, a decrease in visual acuity was revealed:

OD = 0.1 with sph - 2.6 D =1.0,

OS = 0.2 with sph - 2.0 D =1.0.

The reserve of relative accommodation turned out to be equal to 1.5 diopters, i.e., significantly reduced compared to the age norm (4.0 diopters). After three days of atropinization, refraction was revealed by skiascopy:

A trial selection of lenses was carried out (under the influence of atropine):

VOD = 0.1 with sph-2.26 D = 1.0,

VOS = 0.2 with sph -1.76 D = 1.0.

The addition of cylindrical lenses does not improve vision; after cessation of cycloplegia, visual acuity with the same lenses was 1.0. With two eyes open with lenses OD sph - 2.0 D; OS sph - 1.6 D, visual acuity was 0.8. When examined on a color test, vision is binocular. Reading ordinary printed font from a distance of 30 cm with lenses of -1.0 diopters and -0.5 diopters for 20 minutes does not cause any difficulties. There are no initial eye movements when fixating an object located at a distance of 30 cm. Thus, the teenager was diagnosed with mild myopia with weakened accommodation. Distance glasses prescribed OD sph - 2.0 D; OS sph - 1.5 D, and for working at close range - 1.0 diopters less (OD sph - 1.0 D; OS sph - 0.6 D). Exercises to develop accommodation are recommended.

Example 6. 30 years. Complains of poor vision, especially in the distance. She wears glasses sph - 4.0 D on both eyes, which have not improved her vision sufficiently lately. When examined on a Hartinger refractometer, refraction is determined:

When trying out glasses:

VOD = 0.05 with sph -6.0 D =1.0,

VOS = 0.05 with sph -6.5 D = 1.0.

With the same lenses, he can freely read the text N 4 of the Sivtsev table for near from a distance of 33 cm. The relative accommodation reserve is 2.0 diopters, which corresponds to the age norm.

Glasses were prescribed for constant wear in accordance with the optimal correction: OD sph - 5.0 D; OS sph - 5.6 D.

Example 7. 6 years. Decreased vision was discovered during an examination in kindergarten. VOD = 0.3; VOS = 0.2. Spherical lenses do not improve vision. A 3-day atropinization was performed. Refraction was determined skiasscopically:

Using cylindroskiascopy, the position of weakly refractive meridians was clarified: OD -10°, OS -170°. A trial selection of glasses for atropine cycloplegia was carried out:

VОD with sph +2.0 D, cyl - 3.0 D х 10° = 0.6

VОS with sph +2.5 D, cyl - 3.6 D х 170° = 0.6.

With stronger cylinders, visual acuity decreased. Control of correction after the end of cycloplegia during normal monocular examination:

VOD with sph +0.5 D, cyl -3.0 D ax 10° = 0.6,

VOS with sph +1.0 D, cyl -3.6 D x 170° = 0.5.

After “fogging” according to Sheard:

VOD with sph +1.0 D, cyl -3.0 D ax 10° = 0.6,

VOS with sph +1.5 D, cyl -3.5 D ax 170° = 0.5.

Thus, there is refractive amblyopia, since the correction does not provide full visual acuity. In addition, there is a slight spasm of accommodation, which is partially eliminated when using the “fogging” method. Due to the tendency to excessive stress of accommodation, the spherical component of the correction was prescribed weaker than what was revealed under the influence of atropine - based on subjective tolerability:

OD sph +1.0 D, cyl -3.0 D х 10°,

OSsph +1.6 D, cyl -3.5 Dax 170°.

At the same time, a course of treatment for refractive amblyopia was prescribed using local “blinding” irritation of the central fovea of the retina.

After 3 months, visual acuity with glasses increased to 1.0 in the right eye and 0.9 in the left eye.

Example 8. 66 years old. I never wore distance glasses. For near vision I used glasses borrowed from relatives (from 1.0 to 2.0 diopters). Definition of corrective lenses for distance:

VOD = 0.8 s sph + 0.5 D = 1.0,

VOS = 0.7 s sph + 0.5 D = l.0.

When selecting glasses for near vision, +0.5 diopter lenses are inserted into the frame to correct ametropia. Reading the M4 font on the table at close range turned out to be impossible. Identical positive lenses of increasing power were added stepwise to both eyes. The minimum lens power at which reading is possible is determined to be +0.5 diopters. A +1.0 diopter lens has been added to maintain the necessary accommodation reserve. Therefore, lenses with a total power of +3.0 diopters are installed in front of each eye. Reading with these lenses did not cause any difficulties. It is possible from a distance of 25-40 cm from the eyes.

Bifocal glasses were prescribed: on top the lenses are sph +0.5 D, on the bottom - sph +3.0 D. He quickly adapted to the glasses and has no complaints.

Example 9. 48 years old. Always wears glasses OD sph - 4.0 D; OS sph -3.0 D. Lately, reading with these glasses has been causing discomfort. Correction for distance has been clarified:

VOD = 0.06 s sph -4.0 D =1.0,

VOS = 0.07 s sph -3.6 D = 1.0.

The selection of glasses for near was carried out based on age standards: spherical lenses +1.5 diopters were added to both eyes. Reading the font X 4 table at close range was possible, but required effort. To preserve the relative accommodation margin, a +1.0 D lens was added. This achieved conditions of visual comfort. The ability to read was preserved when the sphere was weakened by 1.5 diopters, which indicated a sufficient reserve of accommodation. Final correction for distance:

and for close:

Example 10. A 13-year-old boy came in with decreased visual acuity in the left eye:

VOS = 0.2 s sph -l.0D = l.0.

Using a color test without correction, binocular vision was established. Skiascopy after atropinization revealed 1.0 D. With these lenses, vision is corrected to 1.25.

The boy has unilateral initial myopia. Due to the slight difference in refraction, high visual acuity and the presence of binocular vision with two eyes open, it was decided not to prescribe glasses. Treatment was prescribed to stimulate accommodation.

It would seem that the development of refractometry methods and the study of vision functions has reached such a level that the choice of the optimal means of correction is a purely mechanical task that can be solved using a strict algorithm and even by automated systems.

However, to prescribe correct, “comfortable” glasses, subjective control and clarification of all correction elements are necessary. The trend toward automation has emerged in two directions. The first is the mechanization and computerization of the process of changing trial lenses in front of the patient’s eyes. The second direction generally excludes placing trial lenses in front of the eyes. Their action is replaced by an optical system through which the patient is shown test signs.

As a result of the work of Wollaston, Ostwalt, Tscherning, it seemed that once and for all the optimal shape of meniscal spectacle lenses was found, giving the least aberrations and, therefore, the clearest and most undistorted image in the eye. However, if you insert these lenses into modern frames that have a large area and often a bizarre shape, then the mass of glasses, especially with high-refraction lenses, reaches too large a value. Therefore, a search is underway for ways to reduce the mass of spectacle lenses while increasing the diameter. Firstly, organic materials and various polymer materials of increased hardness are widely used. Secondly, grades of silicate glass with a high refractive index are used. This makes it possible to produce high-refraction lenses with less surface curvature and, therefore, less thickness. Thirdly, high-refraction lenses are made lenticular, that is, only their central part is marked by active optical action, while the periphery is afocal, formed by surfaces of equal curvature.

1. Avetisov E.S., Kovalevsky E.I., Khvatova A.V. Guide to pediatric ophthalmology. – M: Medicine, 2008. – 496 p.

2. Kopaeva V.G. Eye diseases. – M.: Medicine, 2002. – 560 p.

3. Rosenblum Yu.Z. Optometry. – St. Petersburg: Hippocrates, 1996. – 320 p.

4. Sidorenko E.I. Ophthalmology. – M.:GEOTAR-MED, 2002. - 408 p.

5. Titov I. I. Skiascopy. Multi-volume guide to eye diseases. – M.: Mir, 1962 – T. 1. – Book. 1.

Rosenblum Yu.Z. Optometry. – St. Petersburg: Hippocrates, 1996. – 320 p.

Titov I.I. Skiascopy. Multi-volume guide to eye diseases. – M.: Mir, 1962 – T. 1. – Book. 1.

Sidorenko E.I. Ophthalmology. – M.: GEOTAR-MED, 2002. - 408 e.

The correct selection of glasses for vision is a very important point, since in the modern world glasses have become not only a necessity, but also a stylish accessory. When choosing, you should take into account not only medical indicators, but also how the model complements the overall image of a person. Choosing the right glasses so that they last a long time is an art, because you need to take into account many factors.

Selection of glasses for vision and its features

Glasses for different types of activities will differ in materials of manufacture, shape, and reliability. For work and everyday use, more attention should be paid to the thickness of the lenses, selection of the shape of the frame according to the type of face, and overall image. If glasses are used for outdoor activities, sports, or driving, then the main indicator will be their reliability, comfort, and safety.

Despite the differences in glasses according to methods of use, there are general rules for selecting glasses for vision:

Selecting frames according to face size. This means that they should not create optical distortions. It should be noted that when negative, the lenses make the eyes appear smaller than they actually appear. With a plus, on the contrary, they increase. An incorrectly selected frame can enhance this effect. If you are nearsighted, you need to choose larger frames; if you are farsighted, you need to choose thin, invisible ones.
When choosing frames, you should start from the oval of your face. Glasses should create contrast, but not completely follow the shape of the face.
Choice of material. The most popular are metal frames. They present a wide range and low prices. Unfortunately, metal is an allergenic material and often causes a reaction. When purchasing glasses, you should try on and try different options: metal, plastic, horn frames, which are right for you.
Glasses frames should not exceed the width of your cheekbones.
Glasses that cause discomfort are not suitable. The earhooks or nose pads should not press or leave marks. It is important that the glasses are not too wide and do not slide off the nose.
When purchasing a frame, it is important to check it for deformation. To do this, turn the frame and see how symmetrical all the lines are.
It is important that the selected frame does not touch the eyebrows with the upper line and the cheeks with the lower line. The contact indicates that this model is large.

Vision testing and lens selection

In case of poor vision, you should consult an ophthalmologist. He will conduct a study, make an accurate diagnosis and select glasses.

The main vision test is carried out using the Sitzev table. It is a table with lines of letters of different sizes. The patient is located at a distance of 5 meters from the table.

Closing each eye in turn, the person names the letters that the ophthalmologist points to. This determines the optical power for each eye. If the patient's vision differs from 1, he is offered a second test, but using corrective lenses.

The doctor sequentially selects the appropriate lens, first for one eye, then for the other. Finally, a general vision test is performed. It is allowed for vision in lenses to be within 0.9-1.

To obtain more accurate results, examine the fundus and identify other vision problems, a hardware test is used. The most common method is computer diagnostics of refraction.

It is necessary to accurately determine the degree of myopia or farsightedness, determine whether there is astigmatism, and calculate the curvature of the cornea. Based on the results of a computer study, you can choose contact lenses or glasses more correctly to achieve the maximum therapeutic effect.

How different diopter levels affect the choice

Unfortunately, visual acuity is not always the same in different eyes. This situation requires more careful study and proper selection of glasses.

How to select glasses if your eyes have different levels of vision? During diagnosis, the doctor will have to determine the acuity of first one eye, then the other. After this, lenses will be selected.

Lenses for each eye are selected separately. To do this, close one eye and change lenses, selecting diopters until vision becomes sharp. Then surgery is performed on the other eye. Finally, the patient looks at the table with both eyes and repeats the test.

If the difference in diopter values is not large, it is allowed to use the same lenses in both eyes. In this case, the doctor will rely on the patient’s personal feelings. Lenses should not cause discomfort or tension.

If the difference in diopters is large, then a complex prescription will be written, which indicates the parameters across a line for each eye separately. In this case, ready-made glasses from an optical shop will no longer be suitable. They must be ordered separately. The specialist will make the lenses and install them in the frame according to the prescription.

Different visual acuity in the eyes often indicates the presence of other diseases. This may be due to lens diseases, glaucoma, cataracts, and retinal detachment. Possible disturbances in the blood supply to the eyes.

Taking into account facial types

The shape of the frame can not only create a beautiful image, but also completely ruin the impression of a person. Taking this fact into account, corrective glasses are selected based on the individual characteristics of each person. In nature, faces are found in oval, elongated, square, diamond-shaped and triangular shapes.

Let's look at each:

An oval face is a classic. Any glasses look good on him. The only rule is that their width should not be much longer than the face.
Round faces are equal in size on all sides. This has its advantages, but also creates a number of difficulties. In such a situation, rectangular frames or ones with pointed edges are suitable. Such glasses should not have equal width and height. General tendencies: neatness and elongation.
An elongated rectangular face needs additional volume. Rectangular shapes and large arms are ideal for it. Butterfly glasses fit perfectly; they are distinguished by their raised outer edges. Don't try square shapes. They will make the face more massive and heavy.
A square face also has equal dimensions in width and height, but it is distinguished by massive shapes. It needs to be softened. Experts recommend choosing frames with thin, rounded lines. There should not be right angles. Oval thin glasses or a cat eye shape will look great.
A triangular face may have a point at the top or bottom. For each case, you should choose your own option. If the face has the shape of a triangle with the base at the bottom, then the best choice would be a butterfly or semi-rimless frame. For a heart-shaped face, opt for thin oval frames. Rounded models without a rim will also fit perfectly.
A diamond-shaped face is characterized by its widest line at the cheekbones. It has a narrow forehead and chin. Moreover, it has wide cheekbones. For this type, you should choose oval-shaped glasses with an extension at the top. Models with rounded glass will also look good.

Sometimes it is worth playing with contrasts and choosing a form that is not quite suitable. The image will be more vibrant.

Video

Correction rules for farsightedness

Farsightedness is a disease in which the patient clearly sees objects located at a distance, but visual disturbances are observed near. Most often, farsightedness occurs as a result of a shortened eyeball. This disease occurs in both adults and children.

To correct farsightedness, special glasses are used. Only a specialist can select them. Glasses and their choice have their own characteristics.

Glasses for farsightedness are used only for vision correction. They are not curative or preventative. The main task of glasses is to correct vision and restore its sharpness.
Farsightedness glasses are worn constantly only in cases of relatively poor distant vision. Also indicators for their use are eye discomfort, headache, tension of the eye muscles.
When choosing glasses, it is important to consider the working distance. It indicates how and at what distance the patient works with small objects. Depending on this, the glasses can be weaker or stronger.
It is important that the distance from the lens to the eye is approximately 12 mm. This indicator is considered optimal, otherwise glasses can be harmful to health.
If you plan to wear glasses constantly, you should choose a bifocal or progressive type. In them, the optical power of the lenses changes. In the progressive type, it increases from top to bottom; in the fibocal type, the lens is divided into two areas for distance and near.
To choose the right glasses, you need to wear them for at least half an hour.
For different types of work, glasses with different optical powers may be prescribed. They should be changed when changing activities.

Choosing for myopia

Myopia is a disease in which the patient complains of problems with distance vision. He cannot see clear outlines of objects at a great distance. At the same time, he distinguishes objects well close up.

In most cases, myopia occurs as a result of increased tension in the eye muscles, reading in poor lighting, or in the presence of heredity.

Depending on the diopter value, the doctor may prescribe glasses for constant use or only for reading and computer work. Wearing glasses intermittently is indicated for those with vision no more than -1.

The choice of glasses for myopia has its own characteristics.

The frame is selected depending on the quality of vision. In case of large diopters, it is recommended to take a wide frame. This shape will not only cover the thick edge of the glass, but will also ensure reliable fixation of the lens in the frame.
If the degree of myopia is low, then you can choose semi-rimless frames, rimless glasses and other shapes that are most suitable for a specific face type.
Lenses for myopia can be made of thin glass or modern plastic. They are thinner in the central part and thicker at the edges. These lenses make your eyes appear smaller.

Consequences of the wrong choice

Glasses for vision correction are not just an accessory that will complement your look. They are necessary to provide a therapeutic effect and enhance visual acuity. If the vision test and glasses selection are carried out incorrectly, then such glasses can negatively affect your health. For this reason, only an ophthalmologist should write a prescription for glasses.

If glasses are chosen incorrectly, the patient may experience rapid eye fatigue, increased fatigue, poor health, and worsened vision.

Negative consequences do not appear immediately; in some situations they accumulate gradually.

Among the most common consequences of incorrect selection of glasses are:

regular headaches;
feeling of nausea and dizziness;
reduced performance;
unstable emotional state;
blurred vision.

If one or more of these signs appear while using glasses, you should contact your doctor and have your vision tested again.

Types of glasses frames

The quality of use of glasses directly depends on the frame. If it is chosen correctly and looks good on the face, then such an accessory will not only correct the vision problem, but will also fit well into the overall image.

All frames are divided into several types according to the material from which they are made.

Rimless glasses. These glasses are lenses that are attached to the temples. This option is perfect for those who cannot decide on the shape or color of the frame. The lenses look invisible on the face. The main disadvantage is that they cannot be used with large diopters. With a strong minus or plus, the lenses are too thick and the design looks bulky.
Aluminum frame. This option is the most common on sale. Glasses can be in the form of a full rim or half of it. Typically, such frames look light and are thin. The most popular color is golden, although the whole range of colors is available for sale. Among the shortcomings is the fragility of the frame. If dropped, it may bend.
Horn frame. The horn frame in a modern interpretation is made of highly durable and safe plastic. Such glasses were popular not only in the last century. Now they are also coming back into fashion. These glasses are suitable for almost every face type. The colors are natural. Beige, golden, brown, black tones are common. They look quite cumbersome.
Plastic frame. Plastic has become widespread for the manufacture of glasses due to the ability to create a wide variety of shapes and shades. Aviator glasses, Lennon glasses, and semi-rimless frames are in fashion. Plastic is used not only in classic glasses, but also in frames for sports or driving glasses.

In addition to the material from which frames are made, they can be divided by shape.

The selection of glasses is made according to the Donders principle - to prescribe the minimum negative lens that gives maximum visual acuity. If you add another -0.25D to the selected correction, and visual acuity does not improve, then this lens is already redundant. Control - duochrome test (should show a slightly clearer image on a red background) or test with a grid and cross-cylinders: set the negative axis of the cylinder to 90 degrees. If the patient sees vertical stripes better, then you need to increase the negative component (add - 0.25D) until the horizontal and vertical lines are seen equally.

Congenital myopia

Congenital myopia(its frequency does not exceed 2%), if bilateral up to 5.0 D, then in children under 3 years of age correction is not prescribed, because the child sees close objects and there is no threat of amblyopia.

For unilateral myopia and signs of DECOMPENSATION, namely: progression, amblyopia, asthenopia, strabismus, tolerable spectacle correction is recommended or, preferably, contact correction, especially for children.

There are many different, sometimes completely opposite, views on the correction of myopia, so the recommendations given are somewhat conditional.

According to modern views, the correction should be complete, especially if there is asthenopia or special requirements for the profession. Binocular visual acuity must be at least 1.0

Low myopia

With myopia up to 1.0 D, glasses or contact lenses can be worn only as needed, for example, when driving a car. If the visa is 0.4-0.5, the age is from 7 to 18 years, the correction is prescribed depending on the desire - permanent or impermanent. With this type of refraction, there is always a zone of clear vision at a certain distance from the eye and amblyopia does not develop. “Glasses in your pocket” - only when necessary, for distance.

Moderate myopia

For distance, it is recommended that children and adults always wear glasses, a complete but tolerable correction. For a long time it was believed that incomplete correction and bringing visual acuity to 0.7-0.8, no more, was sufficient. Now researchers warn against incomplete correction, because They believe that it contributes to the progression of myopia and insist on the most complete correction as tolerated.

When working at close range, myopes usually remove glasses or use weaker glasses for near.

There are studies that show the negative effect of constant undercorrection and have proven that UNDERCORRECTION DOES NOT LEAD TO A SLOW OFF THE PROGRESSION OF MYOPIA (two-year study by Chung, Mohidin, O, Leary).
The theory of RETINAL DEFOCUS - emmetropization near (Van Alphen -1961, Earl Smith).

The theory is based on the well-known mechanism for regulating the length of the eyeball - the physiological mechanism of emmetropization. An unclear image on the retina (defocus) leads to a decrease in the production of special neuromodulators in it. This, in turn, reduces the production of proteoglycans, which are responsible for the strength of the sclera. In the absence of a clear image on the retina and the appearance of aberrations, the photoreceptors of the paramacular zone are stimulated, from them information goes to the subcortical center, which controls the process of emmetropization - placing focus on the retina. The ciliary muscle and the choroid (choroid) form an elastic membrane and it is its tone that regulates the stretching of the sclera. When near vision occurs, the posterior pole of the eye shifts backward, and the sclera becomes deformed, because the mechanical properties of the sclera in the posterior sections are weaker.

It turned out that PERIPHERAL VISION has a key influence on the process of emmetropization. Earl Smith showed that it is peripheral refraction that determines the rate of growth of the eye in length (elongation); central refraction is not so important. The posterior pole of the eye tends to correspond to peripheral focusing. If, using a correction tool, a sharp image is created in the center of the retina, then its peripheral area with a blurred image will be in the hypermetropic zone, i.e. behind the eye (Fig. 2). If the peripheral focus is behind the eye (hypermetropic type), then this accelerates the growth of the eye. If peripheral focusing is myopic, then this slows down elongation. Conventional spectacle correction, while providing central emmetropization, produces hypermetropia in the periphery. This explains why central myopic defocus when fitting glasses or contact lenses (undercorrection) does not help slow the progression of myopia.

Orthokeratology lenses reduce hyperopic defocus, thereby preventing the progression of myopia. Soft CLs reduce defocus by an average of 2 times, while hard CLs eliminate it completely.

Prolonged work near, combined with a delay in the accommodative response, with insufficient accommodation leads to an elongation of the eye axis by turning on the above physiological mechanism of emmetropization. When working at close range with uncorrected myopia, there is a delay in the accommodative response of +1.0 D or more.

According to the COMET studies, myopia progressed most strongly in the group of patients with delayed accommodation and near esophoria. In this group, progressive lenses effectively slowed the increase in myopia or contact lenses plus glasses were used for near myopes with esophoria.

High myopia

For myopia greater than 6.0 D, full correction often causes discomfort, so only well-tolerated lenses are prescribed. Intolerance to full correction may occur because strongly concave lenses reduce the image on the retina and incorrect projection of objects occurs, their size and shape are distorted, and distance assessment is impaired. With high degrees of ametropia, both myopia and hypermetropia complain that they cannot walk up the stairs with glasses, they stumble out of the blue, dizziness and nausea appear. It is recommended to start using glasses at home, first for a few minutes, then increase the wearing time, and go outside first for a short time and on familiar paths. Gradually all the unpleasant sensations will pass.

Spectacle and contact correction

Light-scattering glass - concav - acts the more strongly the closer it is to the eye. When selecting glasses, such glass must be inserted into the frame into the groove of the lens holder located closer to the eye.

A myopic eye with high myopia looks (without glasses) large, convex, the cornea is large, the anterior chamber is deep, the pupil is dilated. In strong glasses, the eye appears small and its natural dimensions are distorted.

For a combination of myopia and convergence insufficiency (distance and near exophoria), constant maximum spectacle correction for distance and near is recommended.

When myopia is combined with convergence excess, when there is distance orthophoria and near esophoria and delayed accommodation, progressive lenses effectively slow down the growth of myopia.

Myopia up to 6.0 D and weakened accommodation - full correction for distance, weaker lenses for working at close range.

Myopia up to 6.0D and normal accommodation - permanent full correction.

Myopia above 6.0 D is a permanent correction, the value of which for distance and near is determined by tolerance.

A study of refraction in children and adolescents using orthokeratology lenses showed that reverse profile lenses, creating myopic defocus, lead to a slowdown in eye growth and a cessation of myopia progression.

Special contact lenses have been developed under the leadership of B. Hodden that reduce peripheral hypermetropic defocus. Their design involves a distance zone in the center and an increase in positive refraction towards the periphery.

When examining a patient with myopia, you should always think about the possibility of accommodation spasm (exclude it by doing special studies) and keratoconus (everyone should undergo keratometry to determine the radius of curvature of the cornea).

Spectacle vision correction is a method of correcting vision using glasses. Products were invented in Italy in the 13th century.

In modern society, this is one of the most common correction methods: according to WHO about 30 percent The world's population has vision problems, and most of these people choose glasses.

Optical vision correction: what it is, how it happens

The essence of vision correction is that it corrects the optics of the eye, and light is focused on the retina.

In myopic people the image is created not on the retina, but in front of it, and therefore they see distant objects unclearly.

They need glasses with diverging lenses, through which light rays will be focused precisely on the retina, creating a clear image.

In farsighted people On the contrary, the eyes create an image behind the retina. And that's why they need collecting lenses.

It turns out that the lenses in glasses change the length of light rays so so that light is focused on the retina, thereby helping people with visual impairments to clearly see the world around them.

Indications

Spectacle vision correction is the correction of visual impairment using a special device - glasses. They are frames and lenses. A lens is an optical transparent body that refracts light rays.

Indications for the use of spectacle optics:

myopia(myopia) up to -30 diopters;
hypermetropia(farsightedness) up to +10 diopters;
all types of complex and mixed astigmatism(impaired eye sphericity) up to +/- 6 diopters;

heterophoria(hidden strabismus);
presbyopia(age-related farsightedness);
aniseikonia(a condition of the eye in which the sizes of visible objects are perceived with a significant difference);
childhood up to 13 years old;
amblyopia(low vision, often one eye);
anisometropia(with a refraction difference of no more than 2 dioptres);
inability to undergo surgical or laser correction of visual impairment due to contraindications or other reasons.

There are no significant contraindications. Unless glasses cannot be used in infancy, with certain mental illnesses and with individual intolerance. Glasses are also not suitable for people whose professional activities require a wide field of vision or take place in smoky rooms.

Types of spectacle lenses and their corrective orientation

Lenses are divided according to their shape: their correctional focus depends on this.

Spherical

One of the surfaces (or both) of these lenses is spherical. They are used for both myopia and farsightedness. In the first case, the surface is concave, and the lenses themselves are divergent. In the second version, the lenses are positive (or collective).

Photo 1. This is what a checkered piece of paper looks like when looking at it through a spherical (left) and aspherical (right) lens.

Cylindrical

This type of lens, one (or both) of the surfaces of which is cylindrical, used to correct astigmatism. In this disorder, light is focused both behind and in front of the retina. The cylindrical lens corrects this problem.

Prismatic

Glasses with prismatic lenses are prescribed with heterophoria.

In addition to the shape, lenses vary in thickness. Depending on the value of the refractive index, lenses are divided into mid-index, high-index, ultra-high-index And standard refractive index lenses. The higher the index, the thinner and less clearly the prismatic effect of the peripheral part of the spectacle glass.

Photo 2. The structure of a prismatic lens. It is a crescent thickened on one side.

Methods for diagnosing vision and selecting glasses

Before selecting products, the ophthalmologist conducts a number of studies:

determines visual acuity each eye;
conducts automatic refractometry;
determines the degree and type of ametropia based on a subjective method (determining maximum visual acuity using spectacle correction);
clarifies maximum visual acuity under diaphragm conditions;
conducts a trial wearing of spectacle optics within half an hour.

Children and people with amblyopia are also treated drug-induced cycloplegia to turn off accommodation and determine the degree and type of ametropia using subjective and objective methods.

Having completed the examination, the doctor issues a prescription with the required optical power of cylindrical or spherical lenses, interpupillary distance and the reason for selecting glasses.

Well-chosen glasses provide high visual acuity, full binocular vision functions, refractive balance, good tolerability and visual comfort.

Attention! Once a year You will need to undergo a new examination by an ophthalmologist to make sure that the glasses you are using are still suitable.

Pros and cons of wearing glasses, effectiveness of correction

Glasses have many advantages:

Their main advantage is accessibility. It is not difficult to purchase glasses with the required diopters and lens shapes even in the most remote corners of the country.
They are very easy to use. There is no addiction, no need to remember the rules of use.
If you don’t like the correction method with glasses, then There is always the opportunity to choose a more suitable option.
Products are suitable for children under 13 years of age, who, due to their age, have few correction options.

This method has the following disadvantages:

Glasses do not provide complete vision correction.
They limit peripheral vision, disrupt the stereoscopic effect and spatial perception.
Glasses, unlike soft lenses, are less convenient to use: they fog up, slide off the nose, and interfere with active sports.
Incorrectly selected optics affects your well-being: it can simply cause a headache, or can cause further deterioration of vision.

How to use black perforated glasses products?

Perforation glasses - products with lenses made of dark plastic with holes in them, arranged in a pseudo-chessboard order. Because of their structure, they provide the person using them with eye muscle training: the gaze automatically focuses, trying to see the object through the holes.

Indications and contraindications

with heavy eye strain, for example, people whose professional activities involve working on a computer;
for short-term correction myopia, hypermetropia, astigmatism;
for short-term vision correction with various opacities of the optical media of the eye (for example, the initial stage of cataracts or superficial corneal opacities);
with increased photophobia.

They have a number of contraindications:

glaucoma(disease caused by increased intraocular pressure);
nystagmus(involuntary oscillatory eye movements of high frequency).

Before use, consult an ophthalmologist:

for retinal diseases eyes;
with progressive myopia.

Appearance of optics

Perforated glasses consist of a metal or plastic frame into which thick black plastic plates are inserted instead of lenses. 1.2-1.5 millimeters with many holes diameter 1.2-1.5 millimeters. The number of the latter is not standardized and depends on the size of the plates.

Photo 3. Perforation glasses. They are a frame with black opaque lenses, in which there are many holes.

The holes are cone-shaped and arranged in a hexagonal pattern: the horizontal distance between their centers is 3 millimeters, and diagonally - 3.5 millimeters.

Reference. Some glasses models have cutout at the bottom of the lens: it allows nearsighted people to see up close.

Impact principle

A person wearing glasses with holes multiple images are focused on the retina of the eye. To make the image clearer, the ciliary muscles of the eye change the curvature of the lens. Thus, the muscles work every time the gaze moves from one object to another.

This is a device Provides continuous training to unused eye muscles, while simultaneously relaxing those who are overstressed. Wearing glasses not only trains muscles, but also improves metabolism in the tissues of the eye, slows down the process of loss of elasticity of the lens, thereby preventing cataracts and other eye diseases.

Types of lenses used in the manufacture of glasses:

spherical - both surfaces of the lens are spherical or one of them is flat. Spherical lenses are divided into collective or positive (used for hyperopia - a violation of refraction (the process of refraction of light rays in the optical system of the eye), in which light falls not on the retina, but behind it - a person sees blurry near, well - into the distance (with a high degree of hyperopia the patient sees poorly both near and far)) and concave (scattering or negative) - used for myopia - a refractive error, when light is focused not on the retina (the inner layer of the eye), but in front of it - a person sees well near, blurred into the distance;
cylindrical lenses - used to correct astigmatism - a violation of the sphericity of the eye - with this refractive error, the light is focused not in one place of the retina, but in several - astigmatists have visual impairment both near and far;
prismatic lenses - used to correct heterophoria - hidden strabismus - a condition in which there is no obvious strabismus yet, but the eyeballs already tend to deviate from parallel axes.

According to the materials from which the lenses are made:

mineral glass;
plastics.

By light transmission:

transparent;
colored (sun protection);
photochromic (changing color depending on lighting).

By the number of optical zones in the lens:

single vision;
bi- and trifocal;
progressive or multifocal - change their focus depending on the distance to the object in question.

Causes

Indications for spectacle correction:

myopia (myopia) - a violation of refraction (the process of refraction of light rays in the optical system of the eye), when light is focused not on the retina (the inner layer of the eye), but in front of it - a person sees well near, blurred into the distance;
hyperopia (farsightedness) - a refractive error in which light falls not on the retina, but behind it - a person sees blurry near, well - in the distance (with a high degree of hyperopia, the patient sees poorly both near and far);
astigmatism (impaired sphericity of the eye) - with this refractive error, light is focused not in one place of the retina, but in several - astigmatists have visual impairment both near and far;
presbyopia is an age-related change in vision associated with clouding of the lens (the transparent biological lens of the eye); people with presbyopia have blurred vision at close range;
children's age (up to 13 years);
amblyopia (poor vision, more often in one eye);
anisometropia is a condition where different eyes have different types and/or degrees of refraction;
heterophoria (hidden strabismus) - a condition in which there is no obvious strabismus yet, but the eyeballs already tend to deviate from parallel axes;
individual intolerance to contact lenses;
impossibility of surgical correction of visual impairment.

Contraindications to spectacle correction:

infancy;
some mental illnesses;
professions associated with the need for a wide field of vision and increased concentration (for example, pilots, firefighters);
anisometropia - if the difference in refraction in the eyes is more than 2 diopters (refraction measurement units);
individual intolerance to glasses.

Pros of spectacle correction:

accessibility (wide range of assortment, both in design and price category);
ease of use;
reversibility of the effect;
lack of an alternative (under 13 years of age or individual intolerance to contact lenses).

Disadvantages of spectacle correction:

incomplete vision correction - as a rule, glasses are selected in such a way that complete correction does not occur. This is done to avoid the development of lazy eye syndrome;
a foreign object on the face - glasses get dirty, fog up, may slip or fall, the cosmetic effect is important - a change in the perception of the shape of the face when wearing glasses;
injury risk - when playing active sports or, for example, falling, glasses can cause eye injury;
Incorrectly chosen glasses can make you feel worse or contribute to further deterioration of your vision.

Diagnostics

Examination by an ophthalmologist.
Visometry is a method of determining visual acuity using special tables. In Russia, Sivtsev-Golovin tables are most often used; letters of different sizes are written on these tables, larger ones at the top, small ones at the bottom. With 100% vision, a person sees the 10th line from a distance of 5 meters. There are similar tables, where instead of letters there are rings, with breaks on a certain side. The person must indicate which side the gap is on (top, bottom, right, left).
Automatic refractometry is a study of the refraction of the eye (determining the point of the ideal image relative to the retina) using a special medical device - an automatic refractometer.
Cycloplegia is a drug-induced shutdown of the accommodative muscle of the eye in order to detect false myopia. A person with normal vision will experience “physiological” myopia caused by spasm of the ciliary muscle. If myopia after cycloplegia decreases but does not disappear, then this residual myopia is permanent and requires correction.
Ophthalmometry - measurement of the radii of curvature and refractive power of the cornea (the transparent membrane of the eye).
Ultrasound biometry (USB), or A-scan, is an ultrasound examination of the anterior segment of the eye. The technique presents the obtained data in the form of a one-dimensional image, which allows one to estimate the distance to the boundary of media (organism structures) with different acoustic (sound) resistance. Allows you to assess the condition of the anterior chamber of the eye, cornea, lens, and determine the length of the anterior-posterior axis of the eyeballs.
Pachymetry is an ultrasound examination of the thickness of the cornea of the eye.
Biomicroscopy of the eye is a diagnostic method using a slit lamp - a special ophthalmological microscope combined with a lighting device.
Skiascopy is a method for determining the refraction of the eye, based on observing the movement of shadows in the pupil area when the eye is illuminated by light reflected from a mirror.
Vision test using a phoropter - determination of refraction using a special device - a phoropter.
Ophthalmoscopy is an examination of the fundus of the eye using a special mirror - an ophthalmoscope. Simple to implement, but very informative research. Allows you to assess the condition of the retina, optic nerve head, and fundus vessels.
Selection of suitable glasses (lenses).

Additionally

For various visual impairments, glasses allow you to focus light rays on the retina (the inner layer of the eye, the main function of which is to transform light rays into nerve impulses, with the help of which the brain recognizes surrounding objects), allowing you to obtain a clear and clear image of surrounding objects. Also, glasses can protect your eyes from aggressive environmental influences - strong wind, dust, sunlight, etc.
Spectacle correction for impaired visual acuity is one of the oldest and most accessible. The first glasses appeared in the 15th century and became widespread due to their ease of use and good results in correcting visual impairment.
Most people with impaired visual acuity use glasses correction.