Presbyopia correction with progressive spectacle lenses. Correction with progressive spectacle lenses

Presbyopia, or senile farsightedness, is an age-related insufficiency of accommodation of the eye, manifested by a slowly progressive deterioration of uncorrected vision when working at close range.

Such a weakening of accommodation - presbyopia, or senile farsightedness - has long caused the need to use biconvex, collective glasses, and therefore until recently it was not completely separated, or not sufficiently separated from hypermetropia, and both of these conditions of the eye were called in one word: farsightedness.

The Dutch ophthalmologist Donders established the difference between these two conditions of the eye: refractive error and weakening of accommodation, retaining the word presbyopia only to denote the age-related decrease in accommodation. Donders considers the beginning of the appearance of such presbyopia in a normal eye to be the moment when the nearest point of clear vision is more than 20 cm away.

In the presence of emmetropic refraction, presbyopia occurs at the age of 40-46 years, with myopic - later, with hypermetropic - much earlier, often accompanied by a deterioration in distance vision.

The diagnosis is established on the basis of characteristic asthenopic complaints, clarification of the patient's age, determination of visual acuity and refraction; sometimes they additionally examine the position of the nearest point of clear vision for each eye, the volume of accommodation.

Causes of Presbyopia

The reason is the weakening of accommodation due to age-related physiological changes in the lens, which consist in progressive dehydration of the lens tissues, an increase in the concentration of albuminoid, an increase in the yellowish tint, a thickening of the nucleus and lens capsule and, consequently, a decrease in its elasticity while maintaining transparency (phacosclerosis).

Also, an important role is played by the phenomena of involutional dystrophy of the ciliary muscle (cessation of the formation of new muscle fibers, their replacement with connective tissue and fatty degeneration), as a result of which its contractility weakens.

The pathogenesis of presbyopia

The leading role belongs to the compaction of the substance of the lens, as a result of which it ceases to change its refractive power when the gaze moves to a finite distance. This is the oldest theory in the historical sense, but has not lost its relevance to this day.

Despite the obvious process of phacosclerosis, this is not the only factor in the pathogenesis of presbyopia. A certain role is played by age-related changes in the elasticity of the lens capsule: by the age of 60-75, the capsule becomes thicker, then becomes thinner, its elasticity sharply decreases with age, which prevents the lens shape from changing.

Some authors point to the role age-related changes in the ligamentous apparatus of the lens. Due to the increase in the size of the lens, the zone of attachment of the zinn ligaments to the equator of the lens shifts forward, the angle between the capsule and the ligaments in the attachment zone decreases. This leads to the fact that in the process of disaccommodation, the tension created by the ligaments on the lens capsule becomes insufficient for its flattening, the lens remains convex and, as it were, accommodates all the time.

Involutional changes in the human eye also affect the ciliary muscle. It was found that from 30 to 85 years the ciliary muscle is shortened by 1.5 times; the area of ​​the radial portion decreases, the area of ​​the circular portion increases, the amount of connective tissue increases in the meridional portion, the apex of the muscle approaches the scleral spur, acquiring the form of an accommodating muscle young man. In addition, the number of lysosomes in myocytes in the ciliary body decreases, myelination of nerve endings is disturbed, the elasticity of collagen fibers decreases, which leads to a decrease in muscle contractility.

Presbyopia is a physiological condition of the eye, however, an age-related increase in the size of the lens and a violation of the processes of accommodation and disaccommodation can play a significant role in the pathogenesis of glaucoma. Presbyopia itself, without being the cause of glaucoma, in eyes with an anatomical and biochemical predisposition can lead to changes that cause an increase in intraocular pressure. Small eyes with a narrow anterior chamber angle may develop angle block and angle-closure glaucoma. Most often, these eyes have hyperopic refraction. In eyes with a wide anterior chamber angle, changes of a different nature may occur. An increase in the size and compaction of the lens leads to a decrease in the amplitude of excursions of the ciliary body, which in turn reduces the volume of fluid displaced from the anterior chamber. This leads to a state of hypoperfusion of the drainage system of the eye. Normally, in the trabecular apparatus, there is a balance between the processes of synthesis and leaching of glycosaminoglycans. Hypoperfusion of the drainage system leads to an increase in the content of sulfated glycosaminoglycans in it and, as a result, to a decrease in its permeability and the development of open-angle glaucoma.

Presbyopia invariably develops in all people, regardless of refraction, and usually manifests itself at the age of 40-50 years.

Symptoms of presbyopia

1. Slowly progressive deterioration in near vision, especially in low light conditions.
2. Characteristically fast, already after 10 - 15 minutes of visual work, fatigue of the ciliary muscle (asthenopia), expressed in the fusion of letters and lines;
3. Blurring near and momentary blurred vision when looking between near and far objects.
4. Feeling of tension and dull pain in the upper halves of the eyeballs, eyebrows, bridge of the nose, less often in the temples (sometimes even nausea).
5. Mild photophobia and lacrimation
6. In extreme presbyopia, many complain that their arms have become "too short" to hold material at a comfortable distance.
7. The symptoms of presbyopia, like other visual defects, become less pronounced with bright light. sunshine due to the fact that the iris of a smaller diameter is used.

Age-related changes take place differently in people with different pathologies of refraction. For example, presbyopia in people with congenital farsightedness manifests itself more often in a decrease in vision, both for reading and for distance. Thus, presbyopia exacerbates congenital farsightedness and such patients will require glasses with a large "plus"

Complaints of patients are reduced to a decrease in visual acuity near, including in the usual glasses. It is obvious that myopes of 2.0-4.0 diopters suffer the least from presbyopia - their near visual acuity without correction remains high. Correction of presbyopia is reduced to the selection of additional correction for near - addition (ADD, Add), which gradually increases with age-related weakening of the ability to accommodate and the severity of symptoms of presbyopia. Tentatively, the amount of addition can be determined by the age of the patient. Most Russian ophthalmologists know the formula A = (B - 30)/10, where A is the amount of addition; B is the age of the patient. This formula only applies to a working distance of 33 cm.

Yu.Z. Rosenblum et al. (2003) proposes to introduce a correction factor of 0.8 (A = 0.8 (B – 30)/10) into this formula, which makes it more appropriate for the optical needs of a modern presbyop, however, such a calculation can only serve as a guideline, since when choosing additions take into account not so much age as the usual working distance and the amount of residual accommodation.

Diagnostics

Presbyopia is diagnosed using age characteristics, asthenopic complaints, as well as objective diagnostic data.

To detect and evaluate presbyopia, visual acuity is checked with a refraction test, refraction (skiascopy, computer refractometry) and accommodation volume are determined, and a study is made to find the nearest point of clear vision for each eye.

Additionally, with the help of ophthalmoscopy and biomicroscopy under magnification, the structures of the eye are examined. To exclude concomitant presbyopia glaucoma, gonioscopy and tonometry are performed.

During the diagnostic appointment, the ophthalmologist, if necessary, selects glasses or contact lenses to correct presbyopia.

Treatment

Correction of presbyopia consists in adding to the lenses correcting ametropia (nearsightedness or farsightedness), positive spherical lenses for working at close range. However, with spectacle correction, it is necessary to strictly individual approach to each patient according to his initial clinical refraction and age.

The criterion for the correctness of the selected lenses is the feeling of visual comfort when reading with glasses the text corresponding to the font No. 5 of the Sivtsev table for working near from a distance of 30-35 cm. With age, it is not vision that changes, but accommodation, and only the illusion is created that myopes see better in old age .

Reading Glasses- the simplest and most common way to correct presbyopia, which is used only when working at close range.

Spectacles with bifocals or progressive lenses are a more modern version of spectacle correction of presbyopia.

Bifocals have two focuses: the main part of the lens is designed for distance vision, and its lower part is for close work.

progressive lenses are analogous to bifocals, but have an undeniable advantage - a smooth transition between zones without a visible border and allow you to see well at all distances, including medium distances.

If you wear contact lenses, your eye doctor may prescribe reading glasses for you to wear without removing your lenses. A better option would be just the selection of reading glasses.

The modern contact correction industry today offers gas permeable or soft multifocal contact lenses, the principle of which is similar to multifocal glasses. The central and peripheral zones of such lenses are responsible for the clarity of vision at different distances.

Another option for using contact lenses for presbyopia is called monovision. In this case, one eye is corrected for good distance vision, and the other near one, and the brain itself chooses the clear image that is needed at the moment. However, not every patient is able to get used to this method of correcting presbyopia.

Changes in the eye will continue until about 60 - 65 years of age. This means that the degree of presbyopia will change and, as a rule, every 5 years it will increase by 1 diopter. Therefore, periodic change of glasses or contact lenses to stronger ones is required.

Surgical treatment of presbyopia

Surgical treatment of presbyopia is also possible and involves several options.

Laser thermokeratoplasty uses radio waves to change the curvature of the cornea in one eye, modulating temporal monovision.

Multifocal LASIK is a new way to correct presbyopia, but is still in clinical trials. This innovative excimer laser procedure creates different optical zones in the patient's cornea for different distances.

Replacement of transparent lenses- a more radical way to correct age-related farsightedness, but is associated with a certain operational risk. If the presbyopic age coincides with the onset of a cataract, then this method will optimal solution problems with vision correction.

23-10-2011, 06:58

Description

Spectacle correction is one of the types of ametropia correction.

A lens is an optical transparent body bounded by refractive surfaces, at least one of which is a surface of revolution. According to the shape of the refractive surfaces of the lens can be:

spherical(both surfaces are spherical or one of them is flat);

cylindrical(both surfaces are cylindrical or one of them is flat),

prismatic.

Convex lenses (collective or positive) have the ability to collect the rays incident on them, which is used in the correction of hypermetropia. Concave (diffusing or negative) lenses scatter light rays, which is why they are used to correct myopia. Cylindrical lenses used to correct astigmatism. Prismatic lenses find their application for the correction of heterophoria.

All materials used for the production of spectacle lenses are divided into two classes: mineral glass (inorganic materials) and plastics (organic materials). Regardless of its nature, the material must be transparent to the visible range of light rays, homogeneous and not have high dispersion for white light, i.e. not cause chromatic aberrations.

By light transmission, lenses can be distinguished: colorless, colored (sun protection), photochromic.

Lenses are divided depending on the value of the refractive index into groups:

With a standard refractive index (1.54, for organic materials - 1.5);

Average index (1.64 and 1.56 respectively);

High index (1.74 and 1.6 respectively);

Super-high index (more than 1.74 and 1.7 and above).

The use of spectacle lenses with a higher refractive index makes it possible to reduce the thickness and improve their design, reduce the prismatic effect of the peripheral part of the spectacle glass.

According to the number of optical zones, spectacle lenses are divided into:

Single vision;

Bi- and trifocal;

Progressive.

According to the design of the lens surface - into spherical and aspherical.

primary goal any optical correction of refractive errors - moving the focal point of the optical system eyeball on the retina.

Indications:

Hypermetropia;

All types of complex and mixed astigmatism;

Presbyopia;

heterophoria;

Aniseikonia.

Contraindications are relative. These include the infancy of patients, some mental illnesses, individual intolerance to spectacle frames.

Astigmatism. Various types of astigmatism, accompanied by a decrease in visual acuity, are considered an indication for the appointment of spectacle correction.

In this case, it is necessary to determine the spherical and cylindrical correction components and the axis of the cylinder. The value of the spherical component is determined according to general rules prescription of glasses for myopia and hypermetropia. The astigmatic correction component is prescribed according to subjective tolerance with a tendency to maximum values.

If, during an additional study of refraction under conditions of cycloplegia, other values ​​\u200b\u200bof the size and position of the axis of the cylinder are determined, a cylindrical component of a lower optical power should be assigned. The position of the axis of the cylinder, determined under conditions of cycloplegia, is considered optimal.

It should be noted that the early and timely appointment of optimal spectacle correction for various types of astigmatism makes it possible to achieve good tolerability of astigmatism glasses and their high efficiency.

Presbyopia. With presbyopia, visual performance at close range is reduced, asthenopic complaints occur.

For optical correction, positive spectacle lenses are used, taking into account the preliminary spectacle correction for the distance.

At the same time, they are guided by age norms. The first glasses with a positive component +1.0 D are prescribed at the age of 40-43 years, then the strength of the positive glass is increased by 0.5-0.75 D every 5-6 years. At 60 years of age, the positive component of the correction is +3.0 D.

The cylindrical component of the correction, as a rule, remains unchanged.

When presbyopia correction glasses are prescribed, their individual tolerance and visual comfort when working at close range are taken into account.

For the correction of presbyopia, there are bifocal glasses, with a distance zone and a near zone, which allows you to use them constantly.

Currently, progressive spectacle lenses with variable optical power are becoming more common for the correction of presbyopia.

A progressive lens is a lens with a gradual change in the curvature of its surface from top (distant zone) down (near zone). The optical power of such a lens also changes continuously.

A progressive lens has three optical zones:

Distance zone:

The zone of vision for close distance has an additional optical power (the so-called addition), which provides the necessary correction for comfortable near vision;

Intermediate zone or "corridor of progression".

These three zones smoothly transition into one another and provide clear vision at various distances. However, the presence of zones of different optical power leads to the appearance of distortions at the periphery of the lens, which limits the field of clear vision.

The designs of modern progressive lenses take into account the solution of certain problems. For example, lenses with a special design for office work have been created that provide comfortable vision at the distances required for an office space. Created progressive lenses optimized for working on a computer or specifically for reading texts, for sports.

In general, progressive lenses do not provide high quality vision at all distances. Specialized lenses provide visual comfort in a limited range of distances.

heterophoria(eye muscle imbalance). Correction of heterophoria with prismatic optical elements is carried out in case of asthenopic complaints, i.e. decompensation phenomena.

Prismatic correction is also appropriate for eye muscle paresis and diplopia.

Prismatic lenses have the property of deflecting light rays towards the base of the prism. Correction of heterophoria is carried out using prisms, the base of which is located on the side opposite to the deviation of the eye. With exophoria - the base is turned inward, with esophoria - outwards, etc.

Before the appointment of prismatic elements, ametropia is corrected according to the general rules. The total force of the prismatic component is laid out equally for both eyes, while the lines of the prisms coincide, but the bases of the prisms are located in opposite directions.

Aniseikonia. A high degree of aniseikonia is considered an indication for the appointment of iseicon spectacle correction, which is carried out using glasses of a special design. Iseicon glasses use the principle of telescopic systems. Two lenses are placed in front of each eye - positive and negative. In one case, a positive lens is located closer to the eye, in the other, a negative one. In the first case, a direct telescopic system is formed, in the other, a reverse one. Thus, it is possible to achieve approximately equal size of the perceived objects.

However, at present, iseicon glasses are used extremely rarely, since the modern possibilities of contact and surgical correction of refractive disorders make it possible to compensate for high degrees of anisometropia.

Criteria for optimal selection of spectacle correction:

High visual acuity:

Full functions of binocular vision;

Refractive balance, determined using the duochromium test;

Good tolerability, visual comfort.

The main advantages of spectacle correction:

Availability;

No complications;

The ability to change the strength of spectacle lenses;

effect reversibility.

Main disadvantages:

Change in the size of the retinal image with lenses of high optical power;

The presence of a prismatic effect of the peripheral part of spectacle lenses. The prismatic action of a positive spectacle lens leads to the appearance of annular scotomas and a narrowing of the visual fields. A negative lens causes a doubling of the peripheral portion of the visual field;

The impossibility of complete correction of ametropia in cases of high degrees of anisometropia.

Alternative methods:

Contact correction of ametropia;

Keratorefractive operations.

Progressive spectacle lenses are the most modern and most convenient way to correct presbyopia with spectacles. Presbyopia is an age-related change in the normal operation of the optical system of the eye due to the fact that after 40-45 years the lens of the eye and eye muscles, responsible for changing the shape of the lens, lose their elasticity and can no longer provide the volume of accommodation necessary for focusing at close range. Presbyopia occurs when it becomes difficult to read printed materials up close and in order to distinguish letters, it is necessary to move the text away from the eyes (at arm's length). In the case of presbyopia, the following types of glasses can be used to correct vision: - Reading glasses - Bifocals - Trifocals - Progressive glasses.

Reading glasses have single-vision spectacle lenses that provide the visual acuity necessary for reading (at a distance of 30-40 cm. Over time, a person will need additional glasses for vision at long distances. Bifocal glasses have, unlike conventional single-vision spectacle lenses (used to correct myopia) , hypermetropia and astigmatism) two optical zones. In the upper part of the spectacle lens there is a zone used for distance vision. And for near vision, when the direction of gaze drops down to the ground, the lower optical zone (the so-called segment) is used, the optical power of which is higher than the power zones for distance by a positive value, which is called addition and which is designed to compensate for the age-related deficit in the volume of accommodation.The amount of addition required for reading gradually increases with age (from 0.5 D -0.75 D to 3.0 D). The areas for distance vision and near vision in bifocal spectacle lenses are separated by a visible line, which is hallmark bifocal spectacle lenses. Bifocal spectacle lenses will replace two pairs of glasses if the person was already wearing glasses before the onset of presbyopia. Spectacle lenses with 3 optical zones are inserted into trifocal glasses: for distance vision (upper), for near vision (lower) and for vision at intermediate distances (an intermediate zone lying between the upper and lower optical zones of the lens). All zones are separated by visible borders. Trifocal spectacle lenses are used by those patients with presbyopia who previously wore glasses, and bifocal glasses are not enough to see at intermediate distances. Progressive spectacles use special progressive spectacle lenses, the optical power of which gradually increases from top to bottom by the amount of addition. Therefore, for each distance, it is possible to choose a specific zone of the spectacle lens through which it will be possible to see clearly. Progressive spectacle lenses do not differ in appearance from ordinary single-vision spectacle lenses. Progressive glasses are the most advanced non-surgical way to correct presbyopia to date, with a number of advantages compared to the other three types of glasses indicated.

The structure of progressive spectacle lenses Progressive spectacle lenses are a complex optical device, in the manufacture of which the latest scientific and technological achievements are used. In the upper part of a progressive spectacle lens there is a zone of distance vision, the center of which is opposite the pupil when looking straight ahead in the natural position of the body and head. Therefore, a person in progressive spectacle lenses, when looking into the distance, uses progressive glasses, as usual. For reading or doing other work near, in the lower part of a progressive spectacle lens there is a special zone, the optical power of which is greater than the power of the upper zone for distance by an amount called addition (from +0.75 D to +3.00 D). This supplement will provide the patient with presbyopia good vision close, if he looks through this zone. Thus, when reading or doing other work at close range, it is necessary to use the lower part of a progressive spectacle lens, for which the gaze drops down. Note that the position of the eyes and body when reading in progressive glasses does not cause any inconvenience to users of these glasses. The zone of distance vision (upper) and near vision (lower) are connected by the so-called progression corridor, in which the optical power of the spectacle lens smoothly changes from the minimum value at the top to the maximum at the bottom. The progression corridor is used for vision at intermediate distances: between the reading distance (30-40 cm) and 5-6 m (which practically corresponds to distance vision). The length of the progression corridor, depending on the design of spectacle lenses, lies in the range of 10-20 mm. The progression corridor is called the "corridor" because clear vision at intermediate distances can only be obtained by looking through a rather narrow area (only a few millimeters wide) connecting the upper and lower optical zones. The corridor of progression on the sides is limited by areas that are not suitable for vision due to large optical distortions. Unfortunately, it is impossible in principle to significantly expand the progression corridor and completely eliminate unwanted distortions. However, practice shows that the vast majority of users of modern progressive spectacle lenses perfectly use them for vision at all distances, including intermediate ones. At the same time, novice users should simply remember, with lateral directions of gaze, to always turn their head towards the object of observation (so that the line of sight passes through the progression corridor), and not look at it through the peripheral regions of progressive spectacle lenses. Note that this habit is easily acquired in the process of wearing progressive spectacle lenses, and all movements quickly become automatic. Despite their complex design, progressive eyeglass lenses are easy to use and provide high quality vision at all distances. Wearing progressive spectacle lenses is practically no different from regular glasses for the correction of myopia or hyperopia. Cases of intolerance to modern progressive eyeglasses are extremely rare and are almost always due to errors by the optician's staff or the doctor who wrote the prescription for progressive eyeglasses.

The main types of progressive spectacle lenses. There are currently many various types progressive eyeglass lenses. They differ in purpose, design, degree of consideration of the individual parameters of the patient and the spectacle frame chosen by him, and manufacturing technology. By appointment, progressive spectacle lenses are universal and special. Universal progressive eyeglass lenses provide high quality vision at all distances. Special progressive spectacle lenses are designed for vision at a certain distance or when performing certain types of activities. Typical examples of special spectacle lenses are office and computer spectacle lenses. These spectacle lenses are designed to work in the office (where the distance does not exceed 3-5 m) or on the computer (working distances from 30-40 cm to 70 cm). Since these spectacle lenses do not need a distance zone, it is possible to significantly expand the progression corridor, which is mainly used for vision at these distances. Many manufacturing companies produce special spectacle lenses for sports (for example, golf or shooting). According to the complexity of the calculation of the design of the spectacle lens and the process of its manufacture, progressive spectacle lenses can be divided into traditional, optimized and individual. Traditional spectacle lenses are made from semi-finished spectacle lenses with a finished progressive surface (anterior), and the refractive parameters necessary for vision correction (the parameters specified in the prescription for spectacle lenses) are obtained by giving the necessary spherical-cylindrical shape to the rear surface of the spectacle lens. Moreover, for the manufacture of spectacle lenses, a limited set of semi-finished lenses with an already formed progressive surface is used. This limitation leads to the fact that the quality of vision in such progressive spectacle lenses will be suboptimal. However, given the relatively low cost of such spectacle lenses and the rather high quality of vision in them, such spectacle lenses are very widespread in the world. Currently, there are more modern progressive spectacle lenses (optimized and individual) on the market, in the manufacture of which special high-precision technologies for obtaining free-form surfaces are used, which make it possible to implement designs (designs of spectacle lens surfaces) of almost any complexity. These technologies are based on the use of high-precision diamond cutters, the movement of which is controlled by a computer, to give the surfaces of a spectacle lens the necessary shape.

Optimized progressive spectacle lenses use more complex designs than traditional progressive spectacle lenses. For example, design calculations may take into account prescription parameters, or a second (non-progressive) surface may be used to compensate for optical distortion caused by the progressive surface of a spectacle lens (with some companies using wavefront analysis); in some spectacle lenses, the progressive design (changing the optical power of a spectacle lens from top to bottom) is implemented not on the front, but on the back (the inner surface of the spectacle lens) or even distributed between both surfaces of the spectacle lens. For their manufacture, high-precision modern technology FreeForm, which allows you to get surfaces of a "free" shape. Individual progressive spectacle lenses differ from optimized ones in that their designs are calculated taking into account the individual visual parameters of the patient (for example, the distance from the pupil to the back surface of the spectacle lens, the features of the visual movements of the head and eyes, etc.) and the spectacle frame chosen by him (for example, bending angle of the plane of the frame). Individual spectacle lenses are made using FreeForm technology, and to explain their main advantages over other spectacle lenses, a comparison is made between a bespoke suit and a ready-to-wear store. Currently, individual progressive spectacle lenses are the most advanced type of progressive spectacle lenses, providing the highest quality of vision. However, their advantages are especially pronounced in cases where the individual parameters of the patient or the spectacle frame chosen by him differ significantly from the average values ​​included in the calculation of the optical design of spectacle lenses. In other cases (i.e. for most patients), modern FreeForm progressive spectacle lenses will provide high quality vision at all distances.

Moscow School of Medical Optics

Course project on the topic:

"Presbyopia: correction with progressive spectacle lenses"

Introduction

Chapter 1. Age-related changes in eye optics, presbyopia

1 Presbyopia

2 Causes and signs of presbyopia

3 Diagnosis and treatment of presbyopia

Chapter 2. Correction with progressive spectacle lenses

1 The structure of a progressive lens

2 Fitting spectacle lenses

3 Comparative evaluation of the effectiveness of subjective and objective methods of selection of addition when assigning progressive glasses to children

Conclusion

Bibliographic list

Introduction

Presbyopia is known to be one of the first physiological signs of aging. This is why many young presbyopes delay getting their first pair of glasses until their arms are long enough. However, the development of multimedia tools (CD, Internet, use of cell phones) makes it impossible to postpone for the future the solution of the problem of deterioration of visual perception. We all live in a world of fierce competition, and the younger generation is ready to do the work that the older generation is doing now. 45 years is the time for summing up personal results. At this age, everyone wants to look younger and elegantly solve the problem of accommodation when it arises. This is the time to pay a visit to the ophthalmologist, check your eyesight, make sure that everything is within the age range and listen carefully to the doctor's advice. The doctor, for his part, must demonstrate various options for solving the problem of age-related loss of accommodation. In the United States, there is a specific term for physicians, “duty to inform”. With regard to spectacle correction, the doctor should inform the patient about the possible options for spectacles.

It can be:

progressive glasses;

glasses with lenses of the "office" type with a vision range of up to 3-4 m;

bifocals;

regular reading glasses with a clear vision range of up to 50 cm.

It is also possible to solve the problem using two pairs of glasses, but manipulation various types glasses leads to a limitation of visual perception.

The disadvantages of bifocals are obvious:

lack of image integrity;

the appearance of the image shift effect;

the absence of an image in the middle zone when the object hits the interface between the zones;

"jump" of accommodation when looking away;

unaesthetic "senile" appearance of the patient in such glasses.

Thus, the purpose of our work is: to consider the method of presbyopic correction with progressive spectacle lenses.

A more physiological way of presbyopic correction is correction with progressive glasses. The advantages of such a correction are obvious:

clear zone in the middle distance area;

the physiological nature of vision without a jump in accommodation;

maintaining existing visual habits;

great aesthetics without the "window" characteristic of bifocals.

In addition, the surroundings do not see any significant changes in the appearance of the patient who wears such glasses, and with the help of progressive glasses, under the pretext of changing the image, you can hide your age.

With such a correction, the patient's self-esteem increases, self-confidence increases.

Chapter 1. Age-related changes in eye optics, presbyopia

The optics of the eyes is an unstable value, changes in the refraction of the eyes continue throughout life. There is a division of human life into refractive periods:

Thoracic (1 year of life);

Infant period (1-3 years);

Preschool age (3-7 years);

School age (7-18 years);

Age maximum activity(18-45 years old);

Age of presbyopia (45-60 years);

Involutionary age (over 60 years old)

In a premature baby, myopia is usually detected, which depends on intrauterine protrusion of the posterior scleral pole. By birth, the protrusion disappears. In addition, with prematurity, the cornea and lens are more strongly refracted.

The eyes of a newborn are noticeably different from the eyes of an adult. According to A. I. Dashevsky, the lens of a newborn is almost round, and the total refractive power of the eye is high - about 80 diopters. The eye itself is small - 17 mm. The main focus is located behind the retina and there is hypermetropia of about 2.5-4.0 diopters (in cyclopedic conditions). Under natural conditions, due to the increased tone of parasympathetic innervation, the ciliary muscle is in a state of persistent tension. Due to all of the above, in 95% of children under 2 months of age, myopia is found in the study without cycloplegia. By the way, it is called "food myopia." Most newborns (40-65%) are characterized by astigmatism up to 1-2 diopters and often slight anisometropia.

In the first year of life, the optics of hyperopic eyes is enhanced, the number of eyes with myopia decreases, and astigmatism and anisometropia also decrease.

The child grows, the eyeball grows, the lens flattens, and by the age of 3-4, hypermetropia decreases, it is about 2.0 diopters. Clinical refraction is emmetropized.

At 6-7 years old, hypermetropia is 1.0 diopters. By the age of 8, the focus of parallel rays is on the retina - emmetropic refraction is established. The stimulus for eye growth is probably the retina. Apparently, it grows primarily, and the sclera grows, stretches behind it. Professor M.I. Averbakh argued that “any axial refraction is a function of retinal growth. It is her ability that is in the bud."

Ideally, normal proportionate optics, emmetropia, is determined by the age of 8-10. The focus of parallel rays at rest of accommodation is located on the retina. Weak optics - hypermetropia - is apparently the result of growth retardation of the eye, and myopia is already a consequence of its pathological stretching.

From childhood and for many years, the eyes perform their most complex function - and provide excellent distance vision, and tirelessly work at close distances. Imagine again the length of accommodation - the area of ​​clear vision - a huge space, during which the normal eye sees perfectly, clearly from the farthest to the nearest points of clear vision.

But - alas - everything comes to an end, and near vision is vulnerable. Somewhere around 40 years old, an emmetrop, who saw perfectly into the distance, notices that small print is uncomfortable, difficult for him to read, he wants to improve the light, and move the text away. And distance vision is excellent.

1.1 Presbyopia

presbyopia diagnosis lens child

Presbyopia (senile vision, short hand disease) is a disease that occurs mainly in people over 40 years of age and is associated with a change in the physicochemical composition of the lens (dehydration, thickening, loss of tissue elasticity, etc.). All these processes lead to disruption of the accommodation process. The eye is a complex complex optical system, thanks to which a person can clearly see objects at different distances.

The process of forming the image that we see begins with the passage of light through the cornea of ​​​​the eye (a strong lens with a large optical power). Then, after passing through the transparent intraocular fluid in the anterior chamber of the eye, the light bursts into a hole in the iris, the diameter of which depends on the amount of this light. This hole is the pupil of our eye.

The lens of the eye - the second lens in the optical system after the cornea, allows you to accurately focus the image on the retina (it perceives upside down and converts electromagnetic radiation in the visible part of the spectrum into nerve impulses). Further, nerve impulses along the optic nerve reach the visual analyzer in the brain, where the final processing of the resulting image takes place. At a young age, the lens is able to change its curvature and optical power. This process is called accommodation. In other words, this is the ability of the eye to change its focal length, due to which the eye can simultaneously see well both far and near. With age, accommodation is disturbed. This process is called presbyopia.

1.2 Causes and signs of presbyopia

Presbyopia is natural process lens aging. Such age-related changes do not occur immediately, but gradually. But there are other opinions about the etiology this disease. This is due to the fact that not all people who have reached the so-called presbyopic age experience a decrease in vision. As well as the fact that it is possible to prevent and eliminate this violation. In one theory, it is proved that when the eyes are "strained" to see the printed text, the focus shifts forward. Therefore, a person cannot see the image clearly. In addition, pain, discomfort and fatigue appear. In the event that it is possible to relieve the “stress” for a long time, it is possible to return the lost vision. Another theory says that there is no such disease as presbyopia, and such a condition is caused by one of the forms of farsightedness - in the case when a decrease in both distance and near vision is combined. In the third theory, visual impairment is associated with malnutrition and a lack of vitamins, mainly group B, and vitamin C. Treatment in this case is carried out with the help of diet and simple eye exercises.

Signs of presbyopia

When working with small objects, it is difficult to see them (for example, threading a needle).

Reduced contrast when reading small text (letters become gray).

There is a need for brighter and more direct light for reading.

However, people with nearsightedness and farsightedness experience presbyopia differently. In people with congenital farsightedness, vision decreases with age, both near and far. And in people with myopia (myopia), the process of presbyopia may go unnoticed. So, with a slight myopia, about -1D; -2D, there is a compensation of two processes, and a person will need to purchase reading glasses much later. With a higher degree of myopia, of the order of -3D; -5D, most likely a person will not need such glasses. People with this degree of myopia wear glasses for distance and remove glasses for near work.

3 Diagnosis and treatment of presbyopia. The diagnosis of presbyopia does not differ from the diagnosis of other types of refractive errors (the refractive power of the optical system of the eye, expressed in arbitrary units - diopters), for example, myopia or hyperopia.

To diagnose near vision loss, you can take a test at home. Wear glasses or contact lenses if you use them.

You must sit at least 35 cm away from the computer screen.

Look at the image with both eyes open.

Write down which side there is a gap in the rings (right, left, top, bottom)

If you did not see all the rings correctly, then repeat this experience the next day.

If on the second day you again did not see the rings correctly, then it is advisable to contact an ophthalmologist.

Presbyopia treatment

Glasses or contact lenses are used to correct visual impairment in presbyopia. If a person has not previously had vision problems, then reading glasses will be needed. If glasses or lenses were previously used, then they need to be changed. It is convenient to use bifocal glasses, the lenses of which consist, as it were, of two parts. The top one is for distance vision and the bottom one is for near vision. In addition, there are trifocal glasses and progressive contact lenses that create a smooth transition between far, medium and near vision. Another option is the so-called mono vision (one eye is tuned to see near, the other - far). If there is no desire or ability to wear glasses or contact lenses, presbyopia can be treated with surgical operations. To methods surgical treatment presbyopia include LASIK (laser keratomileusis) and PRK (photorefractive keratectomy). Both of these methods involve the use of a laser to reshape the cornea. This allows one eye to be "tune" for near work and the other for distance work. It should be emphasized that monocular vision is artificially created - the patient sees well with one eye either near or far. And you still need to be able to get used to such a vision. Another surgical method The treatment for presbyopia is the removal of the patient's own lens and the implantation of an artificial lens. However, the implantable lens imposes serious restrictions on the patient's lifestyle.

Chapter 2. Correction with progressive spectacle lenses

.1 Construction of a progressive lens

Progressive spectacle lenses are the most modern and most convenient way to correct presbyopia with spectacles. Presbyopia is an age-related change in the normal functioning of the optical system of the eye due to the fact that after 40-45 years the lens of the eye and the eye muscles responsible for changing the shape of the lens lose their elasticity and can no longer provide the amount of accommodation necessary for focusing at close range. Presbyopia occurs when it becomes difficult to read printed materials up close and in order to distinguish letters, it is necessary to move the text away from the eyes (at arm's length). In the case of presbyopia, the following types of glasses can be used to correct vision: - Reading glasses - Bifocals - Trifocals - Progressive glasses.

Reading glasses have single-vision spectacle lenses that provide the visual acuity necessary for reading (at a distance of 30-40 cm. Over time, a person will need additional glasses for vision at long distances. Bifocal glasses have, unlike conventional single-vision spectacle lenses (used to correct myopia) , hypermetropia and astigmatism) two optical zones. In the upper part of the spectacle lens there is a zone used for distance vision. And for near vision, when the direction of gaze drops down to the ground, the lower optical zone (the so-called segment) is used, the optical power of which is higher than the power zones for distance by a positive value, which is called addition and which is designed to compensate for the age-related deficit in the volume of accommodation.The amount of addition required for reading gradually increases with age (from 0.5 D -0.75 D to 3.0 D). The areas for distance vision and near vision in bifocal spectacle lenses are separated by a visible line, which is a characteristic feature of bifocal spectacle lenses. Bifocal spectacle lenses will replace two pairs of glasses if the person was already wearing glasses before the onset of presbyopia. Spectacle lenses with 3 optical zones are inserted into trifocal glasses: for distance vision (upper), for near vision (lower) and for vision at intermediate distances (an intermediate zone lying between the upper and lower optical zones of the lens). All zones are separated by visible borders. Trifocal spectacle lenses are used by those patients with presbyopia who previously wore glasses, and bifocal glasses are not enough to see at intermediate distances. Progressive spectacles use special progressive spectacle lenses, the optical power of which gradually increases from top to bottom by the amount of addition. Therefore, for each distance, it is possible to choose a specific zone of the spectacle lens through which it will be possible to see clearly. Progressive spectacle lenses do not differ in appearance from ordinary single-vision spectacle lenses. Progressive glasses are the most advanced non-surgical way to correct presbyopia to date, with a number of advantages compared to the other three types of glasses indicated.

The structure of progressive spectacle lenses Progressive spectacle lenses are a complex optical device, in the manufacture of which the latest scientific and technological achievements are used. In the upper part of a progressive spectacle lens there is a zone of distance vision, the center of which is opposite the pupil when looking straight ahead in the natural position of the body and head. Therefore, a person in progressive spectacle lenses, when looking into the distance, uses progressive glasses, as usual. For reading or doing other work near, in the lower part of a progressive spectacle lens there is a special zone, the optical power of which is greater than the power of the upper zone for distance by an amount called addition (from +0.75 D to +3.00 D). This supplement will provide a presbyopic patient with good near vision if they look through this area. Thus, when reading or doing other work at close range, it is necessary to use the lower part of a progressive spectacle lens, for which the gaze drops down. Note that the position of the eyes and body when reading in progressive glasses does not cause any inconvenience to users of these glasses. The zone of distance vision (upper) and near vision (lower) are connected by the so-called progression corridor, in which the optical power of the spectacle lens smoothly changes from the minimum value at the top to the maximum at the bottom. The progression corridor is used for vision at intermediate distances: between the reading distance (30-40 cm) and 5-6 m (which practically corresponds to distance vision). The length of the progression corridor, depending on the design of spectacle lenses, lies in the range of 10-20 mm. The progression corridor is called the "corridor" because clear vision at intermediate distances can only be obtained by looking through a rather narrow area (only a few millimeters wide) connecting the upper and lower optical zones. The corridor of progression on the sides is limited by areas that are not suitable for vision due to large optical distortions. Unfortunately, it is impossible in principle to significantly expand the progression corridor and completely eliminate unwanted distortions. However, practice shows that the vast majority of users of modern progressive spectacle lenses perfectly use them for vision at all distances, including intermediate ones. At the same time, novice users should simply remember, with lateral directions of gaze, to always turn their head towards the object of observation (so that the line of sight passes through the progression corridor), and not look at it through the peripheral regions of progressive spectacle lenses. Note that this habit is easily acquired in the process of wearing progressive spectacle lenses, and all movements quickly become automatic. Despite their complex design, progressive eyeglass lenses are easy to use and provide high quality vision at all distances. Wearing progressive spectacle lenses is practically no different from regular glasses for the correction of myopia or hyperopia. Cases of intolerance to modern progressive eyeglasses are extremely rare and are almost always due to errors by the optician's staff or the doctor who wrote the prescription for progressive eyeglasses.

The main types of progressive spectacle lenses. There are many different types of progressive eyeglass lenses available today. They differ in purpose, design, degree of consideration of the individual parameters of the patient and the spectacle frame chosen by him, and manufacturing technology. By appointment, progressive spectacle lenses are universal and special. Universal progressive eyeglass lenses provide high quality vision at all distances. Special progressive spectacle lenses are designed for vision at a certain distance or when performing certain types of activities. Typical examples of special spectacle lenses are office and computer spectacle lenses. These spectacle lenses are designed to work in the office (where the distance does not exceed 3-5 m) or on the computer (working distances from 30-40 cm to 70 cm). Since these spectacle lenses do not need a distance zone, it is possible to significantly expand the progression corridor, which is mainly used for vision at these distances. Many manufacturing companies produce special spectacle lenses for sports (for example, golf or shooting). According to the complexity of the calculation of the design of the spectacle lens and the process of its manufacture, progressive spectacle lenses can be divided into traditional, optimized and individual. Traditional spectacle lenses are made from semi-finished spectacle lenses with a finished progressive surface (anterior), and the refractive parameters necessary for vision correction (the parameters specified in the prescription for spectacle lenses) are obtained by giving the necessary spherical-cylindrical shape to the rear surface of the spectacle lens. Moreover, for the manufacture of spectacle lenses, a limited set of semi-finished lenses with an already formed progressive surface is used. This limitation leads to the fact that the quality of vision in such progressive spectacle lenses will be suboptimal. However, given the relatively low cost of such spectacle lenses and the rather high quality of vision in them, such spectacle lenses are very widespread in the world. Currently, there are more modern progressive spectacle lenses (optimized and individual) on the market, in the manufacture of which special high-precision technologies for obtaining free-form surfaces are used, which make it possible to implement designs (designs of spectacle lens surfaces) of almost any complexity. These technologies are based on the use of high-precision diamond cutters, the movement of which is controlled by a computer, to give the surfaces of a spectacle lens the necessary shape.

Optimized progressive spectacle lenses use more complex designs than traditional progressive spectacle lenses. For example, design calculations may take into account prescription parameters, or a second (non-progressive) surface may be used to compensate for optical distortion caused by the progressive surface of a spectacle lens (with some companies using wavefront analysis); in some spectacle lenses, the progressive design (changing the optical power of a spectacle lens from top to bottom) is implemented not on the front, but on the back (the inner surface of the spectacle lens) or even distributed between both surfaces of the spectacle lens. For their manufacture, high-precision modern FreeForm technology can be used, which makes it possible to obtain surfaces of a “free” shape. Individual progressive spectacle lenses differ from optimized ones in that their designs are calculated taking into account the individual visual parameters of the patient (for example, the distance from the pupil to the back surface of the spectacle lens, the features of the visual movements of the head and eyes, etc.) and the spectacle frame chosen by him (for example, bending angle of the plane of the frame). Individual spectacle lenses are made using FreeForm technology, and to explain their main advantages over other spectacle lenses, a comparison is made between a bespoke suit and a ready-to-wear store. Currently, individual progressive spectacle lenses are the most advanced type of progressive spectacle lenses, providing the highest quality of vision. However, their advantages are especially pronounced in cases where the individual parameters of the patient or the spectacle frame chosen by him differ significantly from the average values ​​included in the calculation of the optical design of spectacle lenses. In other cases (i.e. for most patients), modern FreeForm progressive spectacle lenses will provide high quality vision at all distances.

2.2 Fitting spectacle lenses

In order to offer the patient the optimal means of vision correction, it is necessary to clearly understand why this person needs glasses and in what conditions they will be used. When considering the parameters of a future correction tool and analyzing the nature of visual tasks, special attention should be paid to the presence of presbyopia. Of course, we cannot imagine in great detail the visual environment in which the patient will use the glasses, so the best approach is to be open and learn as much as possible about this environment through conversation. Then the information received must be correlated with what lenses are currently offered by manufacturing companies, with the recommendations of the latter for selection and use, as well as with what parameters are available from suppliers.

Any visual tasks should be analyzed according to a number of characteristics:

adaptive effects.

Reaction time.

Flicker.

The position of the object in the field of view.

Line of sight.

working distance.

The size of the objects in question.

Contrast.

Dynamics.

Strepsis.

Eye hazard and eye protection.

Education.

Depending on its importance, one or another characteristic within the framework of a specific visual task should receive priority in recommendations for choosing a means of correction. In this part of the work, we will consider the visual needs of "beginner" presbyopes, in particular characteristics such as flicker, position of the object in the field of view, working distance, object sizes and fields of view.

flicker

The basic threshold for flicker perception varies depending on the modulation frequency of the light source, as well as on the brightness - the higher it is, the higher this threshold is. If multiple lights in a room have a flicker rate below this basic threshold, the worker may experience visual discomfort. Often, fluorescent lamps are used as the main source of illumination. Lamps with electromagnetic ballast can have a flicker frequency of 100-120 Hz and cause asthenopic complaints and headaches: lamps with electronic ballast do not cause such symptoms. Some patients may have a lower baseline threshold; in addition, it may decrease with visual fatigue. Since the response time of rods is lower than that of cones, flickering can be felt in peripheral areas of the visual field; this explains the fact that when looking at one end of a long fluorescent lamp with peripheral vision, one can feel flickering at its other end.

Another source of flickering light is a computer monitor. Typically, older monitors, such as those with a cathode ray tube, in which the flicker frequency is lower than the patient's baseline threshold, can cause discomfort. Most modern LCD monitors have a refresh rate of 200 Hz and therefore do not lead to visual discomfort.

If it is not possible to adjust the brightness of the light source, glasses with colored lenses can be used; some manufacturers offer special lens colors for office workers. Coloring can reduce the brightness of the light source and remove flicker, the main thing is that photopic vision is not disturbed. If you lower the brightness and switch to scotopic lighting conditions, flickering may return.

The position of the object in the field of view

The maximum visual acuity is achieved in the very center of the fovea. It accounts for 2 ° field of view, at its edge, visual acuity decreases by half. Therefore, if visual acuity is 1.0 in the center of the foveola, then it is 0.5 at its edge. For a working distance of 50 cm, the zone of the fovea accounts for an area of ​​the field of view with a diameter of 17 mm. On the screen of a computer monitor, a 25 mm field of view is projected onto the central fovea. In the presence of fixation, as the distance from the central fovea is 10 °, visual acuity drops to 0.1. At a distance of 6 m from the patient to the fixation point, 10° corresponds to a deviation of 1 m to the side.

Computer monitors are recommended to be placed in such a way that their working area is below the eye level of the worker. If you place the monitor screen at eye level, then the visual system will consider it as a distant object, with a weakening of convergence and accommodation. At the same time, accommodation is necessary because the monitor is close to the eyes; convergence is also required - to eliminate ghosting. Incorrect display position is the cause of asthenopic complaints from patients. Since there is a 20% increase in accommodation when the gaze is lowered by 20°, a lower monitor position may be beneficial for patients with early stage presbyopia. True, this is not always possible in real office work conditions. line of sight

The size of the field of view required may influence the choice of vision correction aid. It can be limited by the distortion of progressive lenses, the size of the aperture, the shape of the light apertures of the frame, and other physical barriers. Working distance

Considering the working distance plays a huge role in the selection of glasses for presbyopes. The presence of an addition causes a zone beyond which clear distance vision is impossible. The table shows the size of the zone of clear vision depending on age, addition and working distance. Object size visible to the eye the angular size of the object indicates the required visual acuity. For example, lowercase letters on a monitor might be 3mm high. If the distance to the screen is 70 cm, then the ability to see such a font corresponds to a visual acuity of 0.3. However, discomfort and fatigue may develop with prolonged use, so you should at least double the value of the required visual acuity. In order to provide the patient with comfortable visual work with a 3 mm text at a distance of 70 cm, visual acuity in the correction tool should be at least 0.7. Contrast

The resolution of the eye depends on the contrast of the image. The contrast of a black line on a white background is 1, or 100%. Light scattering or ghosting can affect the contrast between the subject and the background.

Clear vision zone for various working distances, taking into account the fact that patients have 0.5 accommodation volume in reserve:

case study 1

In this case, consider a high school in a small town. There are three tables in the room, two of them are occupied by the school administration, the third is used from time to time by another specialist. Patient A., a school administrator, aged 55, works full-time. Her responsibilities include entering data into the computer system and making entries in the logs by hand. She also has to receive visitors to the school. For almost four years, the woman has been using near glasses. She last had her eyes tested in January 2012; at the appointment, the doctor told her that the changes were minimal, so the glasses were left the same. The glasses are a frame with narrow light apertures, in which single-vision lenses are installed; looking over them, the patient examines distant objects. Obviously, over time, latent hypermetropia became more and more pronounced, the data of the last refractometry are as follows: Sph +0.75; Cyl-0.25; ax 90. Visual acuity 1.2.: Sph +1.75; Cyl-0.75; ax 55. Visual acuity 1.0.

Addition for the right and left eyes 1.75 diopters for reading font No. 5 at a distance of 40 cm.

According to the subjective feelings of the patient, recently she began to experience difficulties in visual work at close range, so she considered that her vision should be checked. She travels to school by car and has no problems with distance vision.

Flicker. Despite the fact that all the monitors in the office are over 5 years old, they are LCD. The layout of the tables puts restrictions on where these monitors can be placed. Lighting in the office is provided by blocks of fluorescent lamps.

The position of the object in the field of view. The monitor is located at a distance of 65 cm from the patient's eyes, its center is at a height of 28 cm from the table surface. The level of her eyes is at a distance of about 60 cm from the surface of the table; thus, the inclination of the visual axis from the horizontal during operation is approximately 25°.

Line of sight. On the computer, the patient usually works with tables, and on the table she fills out journals and documents by hand. The latter lie next to the keyboard, at a distance of 45-50 cm from the eyes. The window for communication with visitors is located to the left of A.'s workplace, its height is 120 cm.

Working distance

Most of the time the patient works with a computer, the monitor is at a distance of 65 cm from her, the keyboard is at a distance of 45 cm. The essence of the work is entering data into spreadsheets and filling out documents by hand. The lock for closing the window for visitors is located below it, at a distance of 100 cm from the patient's chair. Due to the shelf for filling the registration book by visitors, they are at a distance of 180 cm from the seated administrator when talking.

Object size

The font size of printed text in magazines where the names of schoolchildren are entered, the class number is No. 12, sheets of A 4 format. The sheets are yellow, therefore, the contrast is slightly reduced. Font No. 14 is also used. From time to time, clear detail is required, for example, the names of medicines used by schoolchildren - this information is read from the package, the font on which corresponds to font size No. 10.

On a bright sunny day, light entering the office through the main window reduces image contrast and creates glare on the computer screen. There are blinds on the window that allow you to get rid of them, however, this requires turning on the fluorescent lamps.

The glasses prescription was issued in January 2012: OD:Sph+1.75. OS: Sph + 2.75; Cyl-0.75; ax 45.

Options for choosing a means of correction in accordance with working conditions

Separate glasses with single vision lenses with an average addition for a working distance of 70 cm. At this distance, the addition will be 1.25 or 1.50 diopters - depending on the subjective sensations of the patient.

Advantages. These glasses are ideal for working at a computer. In this case, the patient retains the ability to look into the distance over the glasses. These glasses provide a wide field of vision, limited only by the size of the lenses. They have a low price. Adaptation to them is not required - the correction has not changed much.

Flaws. The patient notes that when looking at close objects she has difficulty. Objects that are far away in the office also do not look as sharp as we would like. For long-term work at close range, additional glasses will be required.

Glasses with progressive lenses

Advantages. One glasses are enough, they can be used as the main means of vision correction at work, at home, during leisure. Large selection of designs and options, all objects in the office are clearly visible. Flaws. Conventional lenses tend to have superficial astigmatism, and the length of the progression corridor, lens aperture, and lens shape must be taken into account. Limited field of view at medium distances. The cost of points increases, adaptation is required to them. Mild anisometropia will increase as the gaze deviates downward while reading. In principle, this problem can be solved by choosing lenses with a short progression corridor, or even by fitting a lens with a short corridor for one eye and a long corridor for the other, but in this case one must be very meticulous in choosing a design. However, this does not solve the problem of limiting the field of view at an intermediate distance.

Improved reading glasses (regression lenses)

Similar lenses are offered by various manufacturing companies. Two typical examples (on the market for 10 years) are Essilor's Interview and Carl Zeiss Vision's Business. Interview lenses (refractive index 1.561) have two options: Interview 080 (when adding less than 2.00 diopters) and Interview 130 (when adding from 2.00 diopters), the index indicates the amount of reduction in optical power (regression by 0.80 or 1 .30 diopters) in the pupil area compared to the total optical power for reading, which characterizes the area 9 mm lower. In our case, we would choose Interview 080 lenses because the required addition is less than 2.00 diopters; in this case, the further point of clear vision will be somewhat further than 1 m.

Business lenses from Carl Zeizz Vision (refractive index 1.5) are also available in two versions: Business 10 and Business 15, and here the numbers express the amount of regression. For our patient, we would choose the first option, the further point of clear vision in this case would be located at a distance of 1.33 m.

Power regression lenses are also produced by other companies, such as BBGR, Noya, Nikon, Rodenstock, Seiko Optical.

Lenses optimized for computing

Among these lenses are Computer 2V (Essilor), Hoyalux Tact (Noya), etc. These lenses have a slight change in optical power, so they have only a small surface astigmatism, which facilitates adaptation.

Progressive Special Purpose Lenses

These are true progressive lenses. For example, Gradal RD (RD is an abbreviation of the words "Room Distance": "distance in the room") from Carl Zeiss Vision are lenses of soft design, with a wide intermediate zone; 0.50 diopters were added to the optical power for the distance, while maintaining the addition unchanged. This means that the power profile is reduced by 0.50 diopters, resulting in reduced astigmatism compared to traditional progressive lenses.

Due to this, the further point of clear vision is removed at a distance of 2 m, which makes these lenses ideal for performing visual tasks, but only at close and intermediate distances, and you can periodically glance at distant objects through the upper zone of the lens. Other examples are AO Technica, Hoyalux iD work Eyas 200/400 and Essilor Computer 3V lenses. The specialist needs to be well versed in the individual characteristics of certain lenses in order to choose the most suitable for a particular patient. When talking with him, you need to focus on the fact that glasses with such lenses should not be used for driving a car.

As you can see, there is currently a wide range of options for vision correction, but not all of them are suitable for a particular situation. In our case, we settled on progressive lenses for special purposes. Thanks to them, the patient received improved near vision, good intermediate vision, and the ability to clearly see visitors through the window without changing glasses or looking over them. Recommendations were given regarding the features of such glasses and the rules for caring for new lenses, as well as general instructions for organizing visual work at a computer.

case study 2

Patient B. is a woman aged 45, works at the same school, workplace organized in the same way as patient A. She is in charge of the financial reporting of the school, and is also responsible for the health and safety of schoolchildren. As in the previous case, a significant amount of visual work is connected with the computer, B. often has to go to other rooms in the school, in particular to the teacher's room and the director's office. The window for visitors is located at a distance of 6 m from her workplace. In a patient with adolescence myopia. Recently, she has noticed that it is easier for her to see small details when looking out from under her glasses. With her current glasses, which she has been using since 2010, B. is able to read font number 5.

The recipe is as follows: Sph -2.50; Cyl-0.75; ax 160. Visual acuity 1.2.: Sph -1.75; Cyl-1.25; ah 180. Visual acuity 1.2.

Last refractometry data:: Sph -2.75; Cyl-0.75; ax 155. Visual acuity - 1.2.: Sph -2.00; Cyl-1.25; ah 180. Visual acuity - 1.2.

However, the measurement of the amplitude of accommodation in her glasses showed 3.00 diopters, which indicates that soon enough she will have problems with near vision. This was demonstrated to her with an additional +1.00 diopter lens. During the conversation, it became clear that high distance visual acuity is important for B., in particular, for driving a car at night. Because she has different type visual tasks, it is necessary to consider lenses for distance with an increase in diopter.

In particular, Essilor produces Anti Fatigue lenses in Orma 1.5 and Stylis 1.67 materials. These are single-vision corrective lenses that are selected for the manufacture of distance glasses and are prescribed for permanent wear. The upper part of the lens provides distance vision according to the chosen correction. In the lower part of the lens, regardless of the selected correction, there is an increase in optical power by 0.6 diopters, which helps prevent the appearance of visual fatigue when working close.

As an alternative - in our case it is even more preferable - modern free-form lenses can be used. Conclusion

As noted at the beginning, a flexible approach to the individual visual needs of the patient, their study and analysis allow the specialist to find the most optimal means of spectacle vision correction. We are not affiliated with any lens manufacturer; The technical information presented is taken from the available catalogues.

2.3 Comparative evaluation of the effectiveness of subjective-objective methods of selection of addition in the appointment of progressive glasses for children

Add is a positive near addition that indicates the difference in diopter between distance and near correction values. According to foreign authors, positive supplementary lenses are prescribed for accommodative insufficiency (short accommodation, accommodation inertia, accommodation inequality and accommodation paralysis). In recent years, the prescription of progressive spectacle lenses has also been used in pediatric practice, especially for myopia, in order to reduce the rate of its progression. In an influence study various methods correction - with the help of progressive glasses and conventional, single-vision glasses - for the development of myopia (Correction of myopia evaluation trial - COMET study), it was shown that during 3 years of observation, the decrease in the rate of its progression in the group of users of progressive glasses compared with carriers of single-vision glasses was only 0.20 diopters. At the same time, when comparing children with initially reduced accommodative response and near esophoria, the advantage of correction with progressive lenses was 0.64 diopters over 3 years.

Existing methods for determining the value of the required addition are subjective and more often calculated. It is known that tables for determining visual acuity at close range are used to select the amount of addition. There are no strict rules regarding the font size to be guided by. A positive spherical lens (addition to distance correction) is selected, with which it is most comfortable for the patient to read text from a working distance. This method has been preferred by most domestic ophthalmologists for many years, however, modern requirements for choosing a near correction method are increasingly forcing doctors to use it as an indicative one, and to clarify the correction method, apply additional tests: by margin of distance, with a fixed cross-cylinder, duochrome for near, with a Helmholtz target, with a striped figure of Duane, etc. However, these methods are not very applicable in pediatric practice. The well-known rule “glasses are not selected for children, but prescribed” is also true in relation to the appointment of progressive and bifocal glasses. Therefore, objective criteria for choosing the amount of addition are needed.

There is a way to measure addition objectively using close retinoscopy. To determine the addition, retinoscopy is carried out from the required working distance. The subject, under conditions of full distance correction, fixes the near test, fixed directly on the retinoscope (usually just above the illuminator). If accommodation is not disturbed, at the time of the study, neutralization of the shadow will be noted. If accommodation is weakened (for example, presbyopia occurs), the shadow will move in the direction of the movement of the retinoscope. In this case, positive lenses of increasing magnitude are attached to the subject's eye until the shadow is neutralized. The positive lens with which this is achieved is regarded as the amount of required addition. However, this method using retinoscopy is not sufficiently objective, since the results obtained depend on the qualifications of the doctor (optometrist), vary different hands, that is, there is the so-called subjectivism of the researcher.

Purpose - to develop a method for objective determination of the magnitude of addition in the selection of progressive glasses for myopia in children and adolescents and to compare the effectiveness of subjective and objective selection methods.

Material and methods

Under observation were 56 children aged 8 to 17 years with myopia from -0.50 to -7.00 diopters, with a progression gradient from -0.25 to -1.50 diopters per year, with a decrease in the reserve of relative accommodation (RAR ) and an objective accommodative response. The nature of vision in both groups for distance and near was binocular.

All patients were divided into two groups. Group I included 32 children aged 8 to 15 years with myopia from -0.50 to -7.00 diopters and a progression gradient from -0.25 to -1.50 diopters per year, in which the amount of addition was determined depending on the degree of decrease in the AOR: from +0.75 to +1.25 diopters with the AoA up to 1.50 diopters and from +1.50 to +2.00 diopters with the AoA below 1.50 diopters. The average value of addition was 1.42 diopters.

Group II included 24 children aged 8 to 17 years with myopia from -1.37 to -5.50 diopters and a progression gradient from -0.25 to -1.25 diopters per year, for whom the addition value was selected by the proposed objective method . The average value of addition was 1.27 diopters.

Along with a general ophthalmological examination, all patients were examined using a Grand Seiko WR-5100K autorefractometer (Japan). The refraction was determined when the target was fixed at a distance of 5 m. Corrective lenses were placed in the test frame, completely compensating for the revealed ametropia. Dynamic refraction was measured under conditions of emmetropia induced by corrective lenses. Before the patient's eyes at a distance of 33 cm (accommodative task of 3.0 diopters), a text from the set of table No. 4 for near was placed, corresponding to a visual acuity of 0.7, and autorefractometry was performed with binocular fixation of the object. The obtained value of dynamic refraction corresponded to the objective accommodative response to a given distance, binocular and monocular, respectively.

The way to objectively determine the amount of addition was as follows. First, the refraction was studied when the target was fixed at a distance of 5 m. Then, corrective lenses were placed in the test frame. The optical power of the latter was chosen 0.25-0.50 diopters weaker, so that the binocular visual acuity in glasses corresponded to 0.8-1.0. Dynamic refraction was measured under conditions of distance correction. Before the patient's eyes at a distance of 33 cm (accommodative task of 3.0 diopters), a text from the set of table No. 4 for near was placed, corresponding to a visual acuity of 0.7, and autorefractometry was performed with binocular and monocular fixation of the object. The obtained value of dynamic refraction corresponded to the objective binocular accommodative response (BAR) at a given distance.

Positive lenses of increasing power were then added to the distance correction until the dynamic refraction with the 33 cm lens reached -2.50 diopters. This value corresponds to the normal accommodative response. The strength of the obtained positive lenses corresponded to the value of the optimal addition.

In addition, OA was determined, as well as the nature of near vision and phoria with complete correction.

All children were prescribed glasses with progressive lenses of a universal design, made by a domestic manufacturer from semi-finished products.

Adaptation results

All patients adapted to progressive glasses: 29 children - during the first hour of wearing them, 22 children - within 1-3 days and 5 children - within 5-7 days. The terms of adaptation to glasses depended on the value of the prescribed addition and the difference in refraction of the previous and new glasses. There was no correlation between the period of adaptation to progressive glasses and the presence and sign of phoria, OA and the magnitude of the objective accommodative response.

Refraction

Prior to the appointment of progressive glasses, the objective manifest (non-cycloplegic) refraction averaged in group I - (3.61 ± 0.28) diopters, and in group II - (3.67 ± 0.25) diopters; cycloplegic refraction: -(3.34 ± 0.28) diopters and -(3.24 ± 0.27) diopters, respectively. After 1 month of wearing glasses, the refraction in both groups did not change on average.

Within 6 months of wearing progressive glasses, the average manifest refraction in group I increased by 0.18 diopters compared to the initial one and amounted to -(3.79 ± 0.32) diopters (Fig. 1). In 23.75% of cases, refraction decreased on average by (0.33 ± 0.39) diopters, which was accompanied by an increase in distance visual acuity in progressive glasses by 0.1-0.3. In 66.88% of cases, the manifest refraction increased on average by (0.25 ± 0.38) diopters, in 9.37% of cases it remained unchanged.

Within 6 months of wearing progressive glasses, the average manifest refraction in group II decreased by 0.02 diopters compared to the initial one and amounted to -(3.65 + 0.26) diopters (see Fig. 1). In 33.3% of cases, refraction decreased on average by (0.23 ± 0.29) diopters, which was accompanied by an increase in distance visual acuity in progressive glasses by 0.1-0.3. In 33.3% of cases, refraction increased on average by (0.18 ± 0.28) diopters, and in 33.3% of cases it remained stable.

During 1 year of wearing progressive glasses, the average manifest refraction in group I increased by 0.45 diopters compared to the initial one and amounted to -(4.06 ± 0.25) diopters. At the same time, the manifest refraction decreased only in 3 children (9.37%) - on average by (0.12 ± 0.29) diopters.

In 3% of cases, refraction increased on average by (0.60 ± 0.26) diopters, in 9.37% of cases it did not change (see Fig. 1). In 16 children, the myopia progression gradient was 1.10 diopters per year; scleroplasty was recommended for them; 6 children left the previous correction and addition;

children have changed the addition; One child had progressive glasses canceled due to increased esophoria.

During 1 year of wearing progressive glasses, the average manifest refraction in group II increased by 0.25 diopters compared to the initial one and amounted to -(3.92 ± 0.30) diopters. In 66.7% of cases, refraction increased on average by (0.38 ± 0.34) diopters, in 33.3% its value remained the same) (see Fig. 1).

Cycloplegic refraction before the appointment of progressive glasses averaged in group I - (3.34 + 0.41) diopters, in group II - (3.24 + 0.40) diopters, and within 6 months of wearing glasses in both groups was stable . After 1 year of wearing progressive glasses, cycloplegic refraction averaged in group I - (3.79 ± 0.39) diopters, and in group II - (3.49 ± 0.38) diopters. Thus, the progression of myopia during the year was -0.45 D in group I and -0.25 D in group II (p > 0.05).

Accommodation

The binocular accommodative response before the appointment of progressive glasses was reduced compared to the calculated norm (-3.00 diopters for 33 cm) in group I by 1.27 diopters, averaging -(1.73 ± 0.22) diopters, in group II group - by 1.13 diopters, which averaged -(1.87 ± 0.22) diopters. The monocular accommodative response (MAR) before the appointment of progressive glasses was slightly higher than the binocular one [in group I, it averaged -(1.88 ± 0.19) diopters], but it was reduced by 1.12 diopters compared to the calculated norm; in group II, MAO averaged -(1.92 ± 0.18) diopters and was reduced by 1.08 diopters compared to the calculated norm. After 1 and 6 months of wearing progressive glasses, there was no tendency to weaken the binocular and monocular accommodative responses - these indicators remained stable. However, after 1 year of wearing glasses in group I, BAO and MAO decreased by (0.22 ± 0.24) diopters and (0.19 ± 0.22) diopters, respectively; in group II, the values ​​of BAO and MAO did not change.

The stock of relative accommodation before the appointment of progressive glasses in all patients was reduced compared to the age norm. In group I, the GA averaged (1.43 ± 0.28) diopters, in group II - (1.6 ± 0.27) diopters. After 1 month of wearing progressive glasses, the AOR increased in group I by an average of (0.23 ± 0.31) diopters, in group II - by (0.17 ± 0.28) diopters. The fact that in group II the DOA increased somewhat less than in group I can be explained by higher numbers at the beginning of the study. After 6 months, the GA in group I increased on average by (0.43 ± 0.29) diopters, in group II - by (0.47 ± 0.28) diopters. After 1 year, the ZA in group I decreased by 0.37 diopters and almost returned to the initial level. In group II, a year later, the GA decreased by 0.20 diopters, but remained (0.27 ± 0.27) diopters higher than the initial level (Fig. 4).

Muscular balance

The character of distance and near vision in patients of both groups was binocular during the follow-up periods of 1 and 6 months. After 1 year of wearing progressive glasses, the nature of vision in 2 children of group I became simultaneous, in all other children of groups I and II it remained binocular.

Muscular balance for near at the beginning of the study was distributed as follows: in group I, orthophoria - 32%, esophoria from 2.00 to 10.00 pdr - 47%, exophoria from 2.00 to 6.00 pdr - 21%; in group II orthophoria - 34%, esophoria from 2.00 to 10.00 pdr - 48%, exophoria from 2.00 to 6.00 pdr - 18%. After 6 months of wearing progressive glasses, the indicators were as follows: in group I, orthophoria - 42%, esophoria from 2.00 to 8.00 pdr - 39%, exophoria from 2.00 to 11.00 pdr - 19%, in group II orthophoria -44%, esophoria from 2.00 to 8.00 ppm - 36%, exophoria from 2.00 to 6.00 ppm - 20%. After 1 year, muscle balance for near: in group I, orthophoria - 36%, esophoria from 2.00 to 17.00 pdr - 44%, exophoria from 2.00 to 6.00 pdr - 20%; in group II orthophoria - 40%, esophoria from 2.00 to 8.00 diopters - 38%, exophoria from 2.00 to 6.00 diopters - 22% (see table).

As we can see, the number of cases of orthophoria increased in both groups. At the same time, in 1 child of group I, exophoria increased to 11.00 pdr, which gave reason to change the addition (example 2); in 1 child of group I, esophoria increased to 17.00 pdptr, an unstable deviation of up to 5 ° appeared with glasses and without glasses, which gave reason to cancel the appointment of progressive glasses (example 3).

Patient K., 10 years old. Diagnosis: moderate myopia, rapidly progressing. Refraction: OD = -4.12 diopters, OS = -4.12 diopters. Objective accommodative response: OD = -1.75 diopters, OS - -2.25 diopters. ZOA \u003d 1.50 diopters.

Initially, the addition was prescribed to the child subjectively. Progressive glasses were prescribed: OU -3.50 diopters, Add 1.00 diopters. Visual acuity with glasses - 0.8. After 6 months, the progression of myopia averaged 0.88 diopters, which reduced the visual acuity in the selected glasses to 0.5. With increasing spectacle correction for dali, the addition was determined by an objective method.

With glass +2.00 diopters, the dynamic refraction at 33 cm was -2.50 diopters. Thus, the value of addition is 2.00 diopters. After 6 months, the progression was fixed at the level of 0.38 diopters, that is, the annual progression gradient (GGP) decreased by 2 times.

Patient 3., 8 years old. Diagnosis: mild myopia, slowly progressing. Refraction: OD = -2.37 diopters, OS = -2.50 diopters. Objective accommodative response: OD = -2.00 diopters, OS = -1.87 diopters. ZOA \u003d 0.50 diopters.

Selected about progressive glasses: Oi-1.75 diopters. Initially, the child was prescribed an addition of 2.00 diopters. Visual acuity in the selected glasses was 0.8. -After 6 months, the progression of myopia averaged 0.55 diopters, which reduced the visual acuity in the selected glasses to 0.6; the nature of vision became simultaneous, and the value of near exophoria increased to 11.00 pdr. With increasing spectacle correction for dali, the addition was determined by an objective method. With a glass of +1.00 diopters, the dynamic refraction was -2.50 diopters, an addition of 1.00 diopters was chosen as optimal. After 6 months, the progression was 0.27 diopters, that is, HGP decreased by 2 times, the nature of vision was binocular, the exophoria for near was 5.00 diopters, which is normal.

Patient K., 13 years old. Diagnosis: mild myopia, slowly progressing. Refraction: OD = -1.87 diopters, OS = -1.91 diopters.

Objective accommodative response: 0D = -2.00 diopters, OS - -1.87 diopters. ZOA \u003d 2.5 diopters. The nature of vision for distance and near was binocular, esophoria for near was 8.00 pdr.

Selected progressive glasses: OU -1.50 diopters. First, the child was prescribed an addition of 1.50 diopters. Visual acuity in selected glasses - 0.8. After 6 months, the progression of myopia averaged 0.06 diopters, the nature of vision - binocular, esophoria for near -8.00 diopters. After 1 year: the progression of myopia - an average of 0.12 diopters, ZOA - 2.50 diopters, the nature of vision - simultaneous, esophoria for near - 17.00 diopters; there was an inconsistent deviation up to 5 ° with glasses and without glasses. It was decided to abolish the wearing of progressive spectacles and assign distance spectacles. The patient underwent a course of orthooptic treatment. After 6 months: the nature of vision - binocular, esophoria for near - 8.00 pdr, deviation - 0° with glasses and without glasses.

A new objective method has been developed for selecting an addition when prescribing progressive glasses to children with myopia.

The proposed method provides obtaining objective data when calculating addition in patients with myopia and accommodative insufficiency and reduces the rate of myopia progression.

When prescribing progressive glasses, children need to examine the state of muscle balance.

Conclusion

In conclusion, I would like to say that the development of ophthallogy follows the path of multifocal correction of age-related changes and diseases. These are the most modern multifocal intraocular lenses and the creation of new types of progressive contact and spectacle lenses. Therefore, the main task now facing specialists is primarily to inform the population about the possibilities of optics for solving age-related problems.

Thus, it can be argued that successful adaptation to progressive glasses depends on the correct determination of refraction and the accuracy of marking and mounting the lenses in the frame. The patient should be given simple detailed advice on their use. He must know and understand the doctor's prescriptions so that his expectations are met, and there is a motivation to order progressive lenses that help restore clear vision lost over the years to presbyopes.

Bibliographic list

1. Avetisov, S. E. Automated system for determining clinical refraction, its assessment and possibilities of application in clinical practice: autoref. dis.... cand.med. Sciences / S. E. Avetisov M., 1977. 11p.

2. Kolotov, M. G. Objective accommodative response in myopia and the possibility of its optimization: author. dis.... cand. honey. Sciences / M. G. Kolotov. M., 1999. 21s.

Rosenblum, Yu.3. Optometry / Yu.3. Rosenblum. St. Petersburg: Hippocrates, 1996. 247 p.

Modern optometry №9, 2011, scientific. - practical magazine for ophthalmologists and optometrists, pp. 35-44.

A method for determining the magnitude of addition in the selection of progressive glasses for myopia / E. P. Tarutta, N. A. Tarasova; Applicant FGU "Moscow Research Institute of Eye Diseases named after V.I. Helmholtz” of the Ministry of Health and Social Development of Russia; the applicant's representative: T. N. Vazilo. - No. 2011110150 dated March 17, 2011 [priority certificate].

Vision correction: textbook. allowance / N.S. Orlova, T.I. Osipov 3rd ed. revised and additional .. Novosibirsk: Sibmedizdat 2010-228s.

Gwiazda, J. A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children / J. Gwiazda // Investigative ophthalmology & visual science. 2003 Vol. 44. P. 1492-1500.

Harvey B. Objective and subjective refraction / B. Harvey, A. Franklin // Optician. 2005 Vol. 230, No. 8. P. 30-33.

10. Scheiman, M. Clinical management of binocular vision: Heterophoric, accommodative, and eye movement disorders / Mitchell Scheiman, Bruce Wick. 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2002. 674 p.

office glasses

Office glasses are glasses designed for work at medium and close distances. Office spectacle lenses are designed in such a way that the optical power in them smoothly changes vertically. Such lenses allow patients with presbyopia to obtain good visual acuity in the range from 30 to 400 cm (depending on the model).

Greater depth of vision is their main advantage over monofocal glasses, and a wide and comfortable middle zone is their main advantage over conventional progressive glasses. Therefore, office lenses are popular with people whose most of the working day is associated with visual load at medium and close distances.

The rules for selecting office glasses depend on the type of lenses that will be installed in the frame.

Office lenses with degression

degression means to gradually reduce something. Degression in optics- a gradual decrease in the strength of the corrective lens (positive lenses are meant here, since the degression was developed for those who use "plus" glasses). Lenses with degression are designed so that regardless of the refractive power in the lower part of the lens, it gradually decreases upward by some fixed amount. The amount of degression can be from -0.75 to -2.0 diopters, but it cannot be chosen arbitrarily. Degression is always the same for each lens brand and is determined by the manufacturer.

When prescribing office lenses with degression, a prescription is selected and written as for near glasses, the interpupillary distance for near is indicated separately for each eye and the desired brand of lenses. Mark the frame with the natural position of the head.

In lenses with degression, the depth of clear vision is inversely proportional to the addition, so before issuing a prescription, you need to calculate the lens power for the average distance, which is different for each patient, and offer to test the correction.

Lenses with degression fit:

• presbyopes of any age who require high quality near and medium distance vision (computer users, musicians, dentists, hairdressers, etc.);
• persons of young age with a pronounced weakness of accommodation, whose work is associated with intense visual load at close and medium distances.

Office progressive lenses

Fixed Addition Lenses

Not exactly office, but they are classified as such. The amount of progression in such lenses cannot be chosen arbitrarily. Regardless of the strength of the lens in the upper part, it smoothly changes downward depending on the brand of lenses: by +0.5, +0.53, +0.6 or +0.88 diopters.

They are also called lenses for supporting/unloading accommodation. They are selected in the same way as distance glasses. The prescription indicates the interpupillary distance for the distance separately for each eye and the lens model with the desired addition. Mark the frame with the natural position of the head.

These lenses are suitable for anyone who needs distance correction and has initial presbyopia or symptoms of visual fatigue when working at close range.

Lenses without fixed addition

In fact, these are ordinary progressive lenses in which there is no distance zone. The result is an expansion of the transition and near zones, the ability to accurately calculate the power of lenses for an average distance and choose an addition of up to 3.5 diopters. May be recommended in the same cases as lenses with degression.

Selection is carried out as for progressive glasses. Before issuing a prescription, you need to calculate the power of the lens for the average distance and offer to test the correction. The prescription specifies the distance correction, the addition (for some models it may be necessary to recalculate according to a special formula), the interpupillary distance for the distance separately for each eye and the lens model. Mark the frame with the natural position of the head.

Read more about what recipes are and what they mean in the note.