Who invented contact lenses for the eyes. Who invented the first contact lenses. The state of lens products in the modern world

Contact lenses- small made from transparent materials lenses worn directly on the eyes to correct vision (that is, to increase visual acuity), with the exception of decorative and cosmetic contact lenses - they can not only correct vision, but also decorate the eyes.

Contact lenses, according to experts, are worn by about 125 million people (2%) in the world.

people wear contact lenses by functional or optical reasons. Compared to glasses, contact lenses generally provide better peripheral vision and do not collect moisture such as rain, snow, condensation or sweat (extreme weather). This makes them ideal for sports and activities on outdoors. In addition, there are diseases such as keratoconus and aniseikonia that tend to be corrected better with contact lenses than glasses.

More than 40% of those who wear contact lenses are young people between the ages of 12 and 25. And among those who wear contact lenses for the first time, the proportion of young people under the age of 35 is almost 90%, while women among them - 70%.

Difference from points

The main optical difference: lenses leave visible objects without distortion (distortion) due to the proximity to the eye. Glasses change the shape and size of objects.

Story

The idea to use contact correction was first expressed by Leonardo da Vinci in 1508. In the archive of his works, they found drawings of a ball filled with water, through which a person with poor eyesight saw better. In his notes, there are also schemes of lenses - the prototype of modern contact lenses. In 1637, Rene Descartes published his work, in which he presented drawings optical instrument. This device consisted of a glass tube filled with water, a magnifying glass was attached to one end, and the other end was attached to the eye. Subsequently, the English physicist Thomas Jung improved the apparatus of René Descartes by using a shorter tube, thereby compensating for the shortcomings of refraction. In 1888, the German physiologist Adolf Gaston Eugene Fick described the first glass lens with optical power. The first lens was made and introduced into medical practice in 1889 by the German ophthalmologist and inventor August Muller. He defended his doctoral dissertation on the topic "Spectacles and corneal lenses". August Müller used the first lenses to correct vision in myopia.

Until the 1960s, contact lenses were made only from organic glass (PMMA). Rigid PMMA lenses were uncomfortable to wear, caused a sensation of a foreign body in the eye and did not pass to the cornea of ​​​​the eye necessary for it. normal functioning oxygen.

In early 2016, Alcon launched the world's first 4th generation contact lenses - water-gradient contact lenses, with moisture content up to 100% and oxygen permeability 156 Dk/t

Types of contact lenses

Exist various classifications contact lenses: according to the material from which they are made, according to the frequency of replacement (the period after which the lenses are replaced with new ones), wearing mode (daily, flexible, prolonged, continuous), design (spherical, toric, multifocal), degree of transparency (transparent , colored, decorative).

In general, contact lenses are divided into two large groups:

• Soft contact lenses
• Rigid contact lenses.

Soft contact lenses are worn by about 90% of contact lens wearers in the world. Soft contact lenses, in turn, are divided into 2 classes: hydrogel lenses and silicone hydrogel lenses.

Rigid contact lenses are mainly used for vision correction in difficult cases (for example, with high degrees of astigmatism, with keratoconus) and in orthokeratology. Rigid lenses allow to achieve an increase in visual acuity due to the fact that they retain their shape. Such lenses are made of polymers that provide a high degree of oxygen transmission to the cornea of ​​the eye, which is why they are called rigid gas permeable contact lenses. [ ]

Colored and tinted contact lenses

colored contact lenses are used to radically change the color of the iris, tint- respectively, to enhance or change the hue. Colored and tinted contact lenses are available both with diopters, for correcting vision and changing the shade of the eyes at the same time, and “zero”, for those who want to achieve only a cosmetic effect.

Colored lenses do not affect the color perception of surrounding objects, since they are transparent in the center.

It is not recommended to wear colored contact lenses at dusk and dark time days, since the human pupil at insufficient lighting expands, the colored part of the lens enters the visibility zone, which is perceived as interference, a veil before the eyes.

Basic parameters of soft contact lenses

Contact lenses are characterized by the following main parameters:

• Material
• Radius of curvature (BC, BCR)
• Lens diameter (D, OAD)
• optical power
• Cylinder axis
• Lens center thickness
• Wearing mode
• Replacement frequency
• Design

• 1 day (one-day contact lenses),
• 1-2 weeks
• 1 month (monthly replacement lenses),
• 3 or 6 months
• 1 year (traditional lenses).

Extended wear lenses without replacement (6-12 months) are packaged in vials. More frequent replacement lenses are packaged in blister packs.

• daytime (lenses are put on in the morning and removed before going to bed),
• prolonged (lenses are put on for 7 days and are not removed at night),
• flexible (lenses are worn for 1-2 days without removing),
• continuous (continuous wearing of lenses for up to 30 days is possible without removing them at night; the mode is allowed only for some silicone hydrogel lenses; consultation of an ophthalmologist is required for its use).
• night (put on 15 minutes before bedtime and removed in the morning. During the day, the patient sees perfectly without lenses, subject to the 8-hour sleep and daily wear.)

• Spherical myopia and hyperopia.
• toric contact lenses are used to correct myopia and hyperopia in the presence of astigmatism.
• Multifocal Contact lenses are used to correct presbyopia.

Aspherical designs can be used in all types of lenses to improve the quality of vision.

Various materials are used to make contact lenses. The majority are hydrogel polymers. Silicone hydrogel There are only about 10 materials.

contact lens material largely determines its properties. The main characteristics of the material are water content and oxygen permeability.

Depending on the water content in the lens material, they are divided into:

• lenses with low content water (<50 %),
• lenses with an average water content (about 50%),
• lenses with high content water (>50%).

For hydrogel contact lenses than more content water, the more they pass oxygen to the cornea of ​​​​the eye, which has a positive effect on eye health. However, as the water content increases, hydrogel lenses become too soft and difficult to handle. That's why maximum content water in hydrogel lenses does not exceed 70%.

For silicone hydrogel lenses, oxygen transmission is not related to water content.

Contact Lens Ability pass oxygen characterized by a special coefficient Dk/t (Dk is the oxygen permeability of the lens material, and t is the thickness of the lens in the center). For hydrogel lenses, Dk/t is usually in the range of 20-30 units. This is enough for daily wear. In order for the lenses to be left on the eyes overnight, much higher values ​​are required. Silicone hydrogel contact lenses have a Dk/t of the order of 70-170 units.

Radius of curvature paired with diameter contact lens affects how the lens "sits" in the eye. Typically, lenses are available in one or two radii of curvature. Poor fit of a contact lens due to a discrepancy between the radius of curvature of the lens and the shape of the cornea can lead to refusal to wear contact lenses.

Basic optical parameters contact lens: the power of the sphere (in diopters, with a "+" or "-"), the power of the cylinder (in diopters) and the position of the axis of the cylinder (in degrees). The last two parameters are indicated for toric contact lenses used to correct astigmatism.

Eye designations in the recipe: OD- right eye, OS- left eye.

The parameters of contact lenses for the left and right eyes in one patient may not match.

Terms of use

If the lenses are chosen incorrectly, "float" in the eye - interference and discomfort are inevitable, you should consult a doctor. If the radius of curvature is too large, the lenses seem to “float” slightly in the eye, and if it is too small, they “get stuck” in one position, are fixed and do not provide this part of the cornea with the necessary oxygen supply. In both cases, the lenses should be changed: correctly fitted lenses may move slightly with some blinking (that is, not rigidly fixed), but most time are in their place in the center of the cornea. Prolonged wearing lenses with a small radius of curvature leads to oxygen starvation of the cornea and increases the risk of keratitis, since with sufficient oxygen, pathogens do not survive.

It is believed that all contact lens wearers should undergo preventive examinations ophthalmologist at least once a year.

Possible Complications

The use of contact lenses can lead to the following types of complications:

• infectious diseases (

Hydrogel lenses.

The first hydrogel polymer materials for contact lenses (in particular HEMA hydroxyethyl methacrylate) were synthesized in the 60s of the 20th century. These polymers were hydrophilic, i.e. ability to attract water. 38% of these polymers consisted of water, which actually carries oxygen to the cornea of ​​the eye. For a normal supply of oxygen to the eyes, tear fluid must continuously flow under the surface of the lens.
Bausch & Lomb has acquired a license for the production of HEMA material and the technology for molding soft contact lenses since about the end of the 60s. The company began to improve the hydrophilicity of contact lenses, launched the production of hydrogel contact lenses Optima FW, Soflens 59 and others, constantly improving their properties and increasing the hydrophilicity of soft contact lenses. However, the peculiarity of this material has limitations and today, almost all gyrogel contact lenses from all manufacturers have equal indicators of moisture content and oxygen transmission to the cornea (For hydrogel products, this indicator is usually 20-30 * 10-9 Dk / t) . By the way, for safe daytime wear, the oxygen transmittance (Dk) should be 24 - 26 units.

Like any item that makes our life easier, hydrogel contact lenses have a number of pros and cons.
Pros.

• Not high price contact lenses.
• Easy selection and replacement. Rapid eye contact with the material.

• Only day mode wearing lenses.
• Low level of gas transmission, as a result - hypoxia and redness of the eyes when wearing lenses in enclosed spaces.

Silicone hydrogel lenses.

At its core, silicone hydrogel contact lenses are a combination of two copolymers - hydrogel and silicone. The hydrogel is the basis of the material, and added to chemical composition silicone - has hydrophobicity, that is, the contact lens already contains water. In this regard, the silicone hydrogel lens allows more oxygen to pass through (- 70-170 * 10-9 Dk / t) and this allows you to wear contact lenses not only in daytime, but also in a prolonged state - continuously, for a week! At the same time, the eyes do not experience hypoxia (oxygen starvation).

• Higher cost of lenses
• Some period of getting used to the lens itself.
• Individual intolerance to the material.
• Tendency to dry out.

Some features of silicone hydrogel lenses that cannot be ignored.
The presence of silicone in the composition of the lens material increases the modulus of elasticity of the lens. This means that the more silicone the lenses contain, the stiffer they become. This affects the properties of the lenses, because with an increase in the modulus of elasticity, the lenses become brittle. Also, with an increase in the silicone content in contact lenses, the moisture content decreases. The lens dries out and becomes less comfortable.

• The possibility of wearing contact lenses in prolonged mode (without taking off at night).
• More high level breathability.

What material to choose? What's better?

Research statistics recent years indicates an increase in demand for silicone hydrogel lenses (up to 40%). Experts say that soon almost all manufacturers will switch to the production of silicone hydrogel contact lenses. This is primarily due to the success of research in the field of silicone hydrogel materials. Manufacturers have found a balance of interaction between breathability, moisture content and modulus of elasticity, combined with high optical performance and wearing comfort of silicone hydrogel contact lenses.
Which material to choose, of course, the consumer himself chooses, based on his personal preferences and capabilities.

For our part, we would advise you to follow simple rules:

• regularly (at least 2 times a year) visit an ophthalmologist, check vision and eye condition. Acquire and use vision correction products selected by a competent specialist.
• take regularly vitamin complexes for eye health
• spend more time outdoors
• do eye exercises for at least 10 minutes a day.
• Do not purchase contact lenses and care products of dubious quality and from random manufacturers.

Contact lenses allow great amount vision related problems. Currently, their range is so large that an ignorant person simply does not understand what to do and which ones to choose. Today, properly selected ones give a person the opportunity to feel comfortable from the very first day of their use. And thanks to the wide variety of products, you can easily choose the most suitable in terms of price and quality.

The types of lenses for the eyes today are determined by the following features:

Hard Features

Rigid lenses are always prescribed only by an ophthalmologist. An indication for this may be a change in the shape of the cornea or lens when it is impossible to treat with soft lenses (for example, astigmatism). Adaptation to them may take some time, in the first few days they will be felt and “interfere” when blinking, but this is normal, you can get used to it over time. The undoubted advantage of such lenses is that they are made personally for each person, since the contours and structure must exactly match the patient's cornea, otherwise it will be impossible to wear them. Can be both plus and minus.

Among them, there are also two types: gas-permeable, through which oxygen can pass, and gas-tight.

Pros of hard types:

• Long service life;
• Form stability;
• Good visual effect, sharp image;
• Easily cleaned from dirt.

Description of soft

According to statistics, these lenses are the most popular today. They are prescribed in cases of visual impairment - such as, for example, myopia or hyperopia. Besides, they are used to apply to the surface eyes medicines when treating after any injury.

Pros of soft types:

• Fast adaptation and wearing comfort;
• Good gas permeability;
• They do not give a feeling of "something superfluous" on the retina;

Soft lenses, in turn, are also divided into types: hydrogel (having great elasticity and resilience, do not "dry" the eye due to its own moisture) and silico-hydrogel - slightly less elastic, with a good gas permeability coefficient. They also have a high moisture content.

These lenses, due to the peculiarities of their structure, have some nuances when used. You have to be extremely careful with them. because they are simply may break if not handled carefully. It is also necessary to store them in a small container with a special solution.

By wear time

Each eye lens company sets certain limits on the "shelf life" of their product, after which it is necessary to replace them with new ones.

Each manufacturer has its own individual service life, described in the instructions, but there is general classification, which looks like this:

All types require replacement after some time, determined by the manufacturer. You can’t save on this and walk with old pairs, because, losing in hygiene and quality, they negatively affect a person’s vision.

By time of use

It is worth distinguishing between “time of use” (the same as “wearing mode”) and “wearing period”. The first implies the maximum time period that allows the wearing of lenses without interruption. What exactly will this time be?, depends on the product itself and the manufacturer.

According to the mode of wearing, the following can be distinguished:

It is important to remember that all lenses have an individual period of use indicated in the instructions. Wearing them beyond the specified time will entail the risk of harm to the health of the patient's eyes. This is due to the fact that the materials from which they are made lose their properties over time. As a result, it turns out that when wearing such lenses, there is almost no gas exchange at all. and there is no proper hydration of the eye. Thus, you can get not only visual impairment, but also redness, itching and dryness of the mucous membranes.

Cosmetic Varieties

Initially, these products were created to hide any eye defects, whether acquired or congenital. But time runs and trends are changing. Today, images have become fashionable that a few years ago would have seemed too unusual. And just cosmetic lenses are great for this, changing the natural color of the eyes.

They, in turn, have two subtypes: colored and tinted. It is worth noting that the latter do not completely change the color of the iris, but only “correct” it. And in the case of a brown shade, it will be very difficult to do this, so this technology is most often used by people with a light iris.

Both types come with and without optical power. This allows you to change the aesthetic properties while improving vision.

Colored allow you to achieve exactly the color that the patient wants. Their pupillary area remains colorless, thanks to which excellent optical characteristics. If a few years ago it was possible to find such products that differ only in color, now new types are appearing, allowing you to experiment even more with appearance.

A recent novelty in the world of optics - "crazy" lenses. They involve not just changing the natural color of the eyes, but “applying” some patterns and patterns. This accessory is perfect for going to a holiday, carnival, theme party. They are also in great demand among professional theater actors.

Various congenital or acquired diseases visual system can lead to changes in the structures of the eye. One type of conservative solution to such problems is the wearing of specially made contact lenses.

Not everyone knows what lenses for the whole eye are called. This is one of the types of special lenses - scleral. They are used when it is impossible to wear ordinary, due to the shape or some other features of the cornea. There are several subtypes of such lenses, depending on their size and diameter.

Orthokeratology lenses- perhaps the most difficult to manufacture of all presented. In order to ideally select such a pair, you need to conduct research on a keratotopograph. And yes, they will be very expensive.

There is also a hybrid species - the toughest on the list. It is prescribed only by the attending physician.

Just before you go to the optics store and order the lenses you need, you should definitely go through full examination at the ophthalmologist. Most of the changes and deviations from the norm can be noticed by a specialist at such a reception. Next, depending on clinical picture will be appointed necessary medicines and selected lenses.

This does not apply to cases where the lenses are not medical in nature, such as colored lenses. They serve only for aesthetics and are selected personally by the client. But even here, many would prefer to play it safe and consult a doctor first.

When buying such a product, you need to understand that this is not a toy, and such a thing directly affects health. Therefore, care and use must be appropriate.

If you follow the rules and fully comply with and follow all the recommendations of the attending ophthalmologist, then contact types won't be a problem at all. This is a kind of convenient “gadget” that allows you to restore your vision without unnecessary discomfort without wearing classic glasses.

Attention, only TODAY!

Today, many people increasingly prefer contact correction vision. Many are faced with the problem, which contact lenses are best? Today we will try to determine how to choose the best quality lenses for the eyes.

Who needs contact lenses and why?

Modern breathable materials, wide optical range and the latest technology allow you to restore your vision. It is necessary to choose contact lenses for such eye diseases as:

• Age-related changes (presbyopia);
• Violation of the shape of the cornea and lens (astigmatism);
• Farsightedness (hypermetropia);
• Myopia (myopia of varying degrees).

When deciding to choose the most suitable lenses for your eyes, you need to consider optical power, radius of curvature and individual features. The best contact lenses are able to form a real system with the eye, providing high vision:

• Without limiting the field of view (as is the case with glasses);
• Not subject to weather influences (rain, snow);
• Suitable for active sports
• Ideal for people with a big difference range on the right and left eye.

Choice of lenses

Some believe that you can switch from glasses to lenses of any company on your own, because there is nothing difficult in this - just look at the prescription for glasses and select the required optical power. However, this may lead to strong consequences– from dry eye syndrome to sharp deterioration vision as a result of hypoxic changes in the cornea.

An ophthalmologist should choose the most suitable lenses for you. A regular eye test will not be able to give anything - lenses with the same optical power and radius may differ in other parameters not indicated on the package:

• Thickness and shape of the product;
• The elasticity of the material;
• Edge processing method.

The procedure for choosing lenses for the eyes begins with consideration individual characteristics patient - work schedule, lifestyle, chronic diseases, bad habits, possible contraindications and motivation to wear them. Before choosing which company is better to choose lenses, the doctor will prescribe the following examinations:

• Assessment of the state of the ocular anterior segment;
• Determination of the degree of visual acuity;
• Examination of the eye day for possible pathologies;
• Carrying out computer diagnostics.

Thinking about which lenses are better, you need to take into account the tripling of the eyes - the density of the eyelids and the incision, the features of the vessels, the qualitative and quantitative composition of the mucous fluid. Using special tests, the ophthalmologist will evaluate the fit of the lens to the cornea, local reaction the surface of the eye and the level of vision correction.

If eye lenses are prescribed for the first time, the doctor must show the patient how to put them on and take them off. Provide information on wearing and caring for them.

Types of contact lenses

Rigid lenses

Until the end of the 60s of the last century, lenses were created from organic glass - this material could not pass oxygen and delivered a lot of discomfort. The gas-permeable rigid lenses created after them allowed the eyes to “breathe”, but caused corneal edema and mechanical irritation of the eyes.

Modern varieties of rigid eye lenses are made of silicone: they do not fall out when you blink, do not dry out and have a long service life, not like one-day types. They are very inferior in terms of wearing comfort compared to the soft types in some cases, they lead to blurry vision. Modern doctors do not recommend choosing this type of lens for wearing, recommending choosing a more suitable option.

Rigid type silicone lenses are most preferred for the following types of eye conditions:

• Refractive anomalies (orthokeratological correction);
• Senile farsightedness (presbyopia);
• Keratoconus (thinning and reshaping of the cornea);
• Severe astigmatism that cannot be corrected with toric lenses.

soft lenses

Soft eye lenses contain a large percentage of water, which makes them very comfortable to wear, limits the period of use, some of them may be one-day. Based on the purpose, three types of soft lenses can be distinguished:

• Toric - for patients with astigmatism;
• Spherical - to correct hypermetropia and myopia;
• Multifocal and bifocal - for the correction of presbyopia.

Separately, it is necessary to highlight carnival and colored lenses (they can both correct vision and be simple), orthokeratological (worn at night to improve vision during the day) and therapeutic (used to protect the eyes after surgery).

Mode and timing of wearing MKL

Depending on the duration of wearing, three groups of lenses can be distinguished:

• One-day (change every day);
• Classic (replacement every 6-12 months);
• Planned replacement lenses (from two weeks to three months).

The longer the service life of the product, the more careful care they need. If wearing daily lenses, only drops to moisturize the eyes may be needed, then planned replacement lenses require the use of disinfectant and moisturizing solutions, and the traditional option requires additional cleaning of protein deposits using special tablets.

According to the wearing mode, soft lenses can be:

• Daily wear (be sure to remove before going to bed);
• Prolonged wear (can be worn without removal from 3 to 30 days without damage to the eyes);
• Deep wearing (removed periodically at night).

According to ophthalmologists, it is better not to abuse long-wear lenses, in this case one-day lenses are better. If these are not daily lenses, then daily care should not be neglected - they accumulate microbes and natural deposits on their surface that can cause infectious diseases. Only one-day lenses are an exception, tonies are individually packaged and discarded after each wear.

What are soft lenses made of?

Soft contact lenses contain hydroxyethyl methacrylate and various copolymers of silicone and hydrogels. polymer material NEMA, has incredible ability moisture absorption. It was first synthesized in 1960 in Czechoslovakia. The first soft lenses were created by Dragoslav Lim and Otto Wichterle. Subsequently, this technology was purchased by Bausch & Lomb. She managed to open new level in the field of contact vision correction.

Continued development of new lenses continued in the 70s of the last century, and in 1999 the first silicone hydrogel lenses were created with the ability to wear 30 days without interruption. by the most important characteristics that can affect the duration of wearing and the quality of lenses are:

• Oxygen transmittance (Dk/t), which takes into account the ability to let oxygen to the corneal vessels and the thickness of the lens. The higher this indicator is, the longer period continuous wear and lower probability of hypoxia;
• Fluid content: Low hydrophilic lenses have less than 50% moisture, high hydrophilic lenses have 50 to 80% moisture. The higher this indicator, the higher their strength;
• The elasticity model (MPa) affects the wearing comfort and ease of donning the lens.

Manufacturers can use materials under various proprietary names, indicating characteristics on the packaging.

Soft modern lenses

Hydrogel lenses

The first mass-produced contact correction product is still popular today. Hydrogel contact lenses can provide a high level of wear due to their softness and thinness.

Low gas permeability levels are offset by a high water content, which conducts oxygen molecules to the cornea. When choosing such lenses, you need to focus on the level of moisture content in them.

Silicone hydrogel lenses

Adding silicone to the material allows you to create a kind of "lattice" that is transparent to the passage of oxygen. The degree of elasticity is higher compared to hydrogel, so the lenses keep their shape better. This type of lenses is very demanding on the mode of their wearing:

• It is recommended to wear in the daytime with the removal of them at night;
• Prolonged mode - no more than two weeks, after which you need to throw out the old lenses and open a new package;
• Mandatory consultation on the choice of product;
• Use of a peroxide cleaning system.

Biocompatible lenses

Wearing any type of contact lenses can cause defensive reaction- the body perceives it as foreign body, the active production of proteins begins. Protein deposits allow the lens to be part of the eye, but at the same time degrade its optical properties. New developments have involved biocompatible materials that are as close as possible to natural composition eye tissues. Such components have many advantages:

• resistance to dehydration;
• Resistance to deposit formation;
• Minimizing the possibility of dry eye syndrome and an allergic reaction.

Aspherical lenses

The parameters of each type of lens for the eyes are designed exactly in its center. As it moves towards the eyes, visual acuity will decrease, and eye strain occurs. The surface of this type of lens is created in the form of an ellipse - the radius of curvature gradually changes from the center to the periphery. This form of lenses is able to neutralize the aberrations of the eye as much as possible, providing a high degree of wearing comfort.

This type of lens is especially relevant for people with large diopters (more than 4.5) - they reduce eye strain.

Contact lens care

Lenses chosen incorrectly can cause serious eye diseases, so it is not recommended to make a decision in their purchase on your own. A visit to the ophthalmologist should become a rule - you need to go to the doctor 1-2 times a year (in case of discomfort - immediately).

Observe the exact terms of wearing lenses - mark in advance the day of replacement of lenses. The service life of the product must be counted from the moment the package is opened, it does not matter how many days the lenses were actually worn. It is necessary to observe the rules of personal hygiene - always wash your hands before putting on and removing lenses, do not use drops and solutions with an expired date. If there is no time for daily care, it is better to choose one-day lenses for eyes.

Choose suitable type Only an ophthalmologist can wear lenses. You should not try to do it yourself, because you can only harm your eyesight. And proper care of the lenses will help to avoid inflammation and other complications with the eyes.

Approximately 2% of the world's population uses eye lenses for vision correction. This invention of human thought greatly simplified life, allowing you to see more and at the same time look better. Having made them an important attribute of their lives, few people think about the question of what eye lenses are made of.

Lenses can be divided into soft and hard. The first appeared in late XIX century, remaining relevant until the 1960s. They were rigid and were made of Plexiglas. Over time, silicone-based lenses began to be made, which are able to correct vision more efficiently, achieving maximum sharpness even with serious illnesses eye. Rigid lenses based on silicone have a higher oxygen saturation. The disadvantage of these lenses is that they require getting used to and more careful selection, based on anatomical features eye.

The vast majority of people prefer to wear soft lenses which have the following advantages:

• soft lenses are universal;
• they are saturated with moisture and pass enough oxygen;
• have a wide range of uses from vision correction to cosmetic effects.

Lenses become soft due to the presence of water: the more moisture in the lens, the softer and more elastic it is. Empirically, the optimal water content was found to be 70%. If the water content is above this level, the lenses become too soft and uncomfortable to use, if the contact lenses are made with less ability to absorb water, dryness and discomfort are felt in the eye.

Soft eye lenses are made from two main types of hydrophilic polymers: hydrogel and silicone hydrogel. The first polymer is characterized by poor oxygen permeability to the eye cornea, as a result, hydrogel lenses are intended only for daytime wear and require frequent shift. The second polymer partially eliminates the disadvantages of the first. Silicone hydrogel lenses have a high gas permeability, so they can be worn for several days without removing them without the threat of eye hypoxia. However, increasing the proportion of silicone reduces the moisture content of the lens, making it more rigid and brittle.

Although the production of lenses has long been established: consumers choose the best for themselves and are generally satisfied with the quality, complaints remain about fatigue eyes and feeling of dryness. Therefore, in May 2016, Alcon introduced its innovative development - water-gradient lenses made using a special technology of combining materials. These new generation lenses have increased moisture content, which is 80% inside, and reaches 100% on the surface, making them almost invisible to the eye. In fact, Alcon offered non-contact lenses.

Note that materials for the manufacture of contact lenses can be precious. So, the Indian Sanjay Shah presented to the public women with brilliant eyes. The basis of his designer lenses, which cost a fortune and weigh about 6 grams, is yellow or White gold with diamond inserts. A water cushion is provided between the lens and the eye for comfortable wearing.
Knowing the material from which the lenses are made, you can choose the optimal quality for the eyes in accordance with the possibilities of the wallet.

26.09.2016