Hygiene and contraindications. Hard contact lenses
Johnson & Johnson was founded in 1886. It is one of the largest American manufacturers of cosmetic and medicinal products, as well as contact lenses. Johnson & Johnson products are known throughout the world and are sold in many countries.
In 1987, Johnson & Johnson introduced the innovative Acuvue contact lenses, designed for seven-day wear. Since that time, over 2 billion contact lenses have already been produced. As for the lenses supplied to the Russian market, most of them are produced in Ireland at the famous Limerick plant.
Popular brands : 1-Day Acuvue TruEye, Acuvue Oasys, 1-Day Acuvue Moist, 1-Day Acuvue Define, Acuvue Oasys 1-Day.
CooperVision
CooperVision is an American manufacturer of contact lenses. The company was founded in 1958. The main factories for the production of contact lenses of Cooper Vision are located in the English city of Hampshire, as well as in the American cities of Rochester and Huntington Beach.
The company's headquarters are based in Irvine, California.
The US facilities primarily manufacture soft toric and spherical contact lenses, while the UK manufactures elective soft contact lenses.
It was the specialists from Cooper Vision who first developed soft contact lenses for regular replacement. The basis of these lenses is the innovative material tetrafilcon.
Popular brands : Proclear, Biofinity, Avaira, Myday, Biomedics 55.
Alcon
Alcon is a recognized world leader in the manufacture and sale of ophthalmic products. The company's headquarters is located in Texas. More than 2,500 employees work for the benefit of Alcon.
The company was originally founded in Fort Worth in 1947 (Texas). The origins of the company were two American pharmacists - Robert Alexander and William Conner. It was the first syllables of their surnames that served as the basis for creating the name of the company.
In 1977, Nestlé acquired Alcon, as a result of which the sales area of this company's ophthalmic products was expanded. This is how the manufacturer entered the European market. Currently, Alcon factories are located in Spain, Belgium, Mexico, France and Brazil.
Subsequently, Alcon also began to develop and establish production of surgical equipment for ophthalmology.
Bausch & Lomb
Bausch & Lomb is a leader in the manufacture and sale of contact lenses.
The company was founded in America in 1853. The founders of the company were emigrants from Germany J. Bausch and H. Lomb. They chose to specialize in the production of special and high-precision optics: telescopes, microscopes, binoculars, night vision devices. In 1971, Bausch & Lomb was the first company to receive FDA approval to market soft contact lenses.
Bausch & Lomb manufactures a wide range of ophthalmic products and surgical equipment, which were previously produced under the Chiron and Stortz brands.
Bausch & Lomb has sales centers and factories in 25 countries.
Popular brands : PureVision 2, Biotrue ONEday, Soflens Daily Disposable, Optima FW.
Korean companies
In the last few years, several Korean companies have appeared on the contact correction market, such as OKVision, G&G Contact Lens. The most popular among their products are colored contact lenses due to their bright colors and affordable prices.
Contact lenses have long established themselves as a reliable method of vision correction. They are extremely relevant in case of myopia. farsightedness or astigmatism. Due to the fact that the latest materials and technologies are used in their production, they are a worthy replacement for glasses. We will talk further about the features of different types of lenses, their characteristics and disadvantages.
Features of the selection of contact lenses
When selecting, you need to take into account various criteria, especially taking into account optical power, radius of curvature and, of course, the material from which they are made. The right choice allows you to gain good visual acuity and feel comfortable during use. Undoubtedly, the quality of vision that is provided by contact lenses is much higher than the quality that a person receives by wearing glasses. This is explained by the fact that lenses are capable of forming a harmonious system with the surface of the eye. Moreover, there are no restrictions on the field of view or the possibility of damage due to bad weather conditions.
Lenses have become popular because they are not only easy to use, but also relatively low cost and, most importantly, they can protect the eyes from operations to restore vision. All surgical interventions create the possibility of complications, so it is better not to risk your eye health.
Those people whose occupation is different from their usual cannot do without contact lenses. Agree, it is unlikely that an athlete, race car driver or diver will find time to care for his glasses. By the way, lenses are an excellent option for people who have different visual acuity in the left and right eyes. The modern range of such devices is represented by a wide optical range and different types: toric, aspherical, multifocal, as well as colored lenses of various shades.
Classification of modern contact lenses
Today, contact lenses can be divided into subgroups based on several parameters.
So, based on the time criterion, they distinguish:
According to the nature of wearing they are distinguished:
They can also have a special design and all kinds of colors:
Depending on what material served as the basis for manufacturing, there are soft and hard contact lenses, which we will talk about in more detail.
Benefits of soft contact lenses
Such devices are used by almost all people today. Doctors warn that you should not violate the prescribed regimen; you must take them off at night. Of course, it is much more convenient to wear lenses without removing them, but such an action can provoke swelling of the cornea. This condition can occur due to the fact that the cornea does not receive sufficient oxygen supply, and this, in turn, is fraught with very serious consequences.
The structure of the human cornea is specific because it is devoid of blood vessels, so it is forced to receive oxygen and nutritional elements from the air environment, as well as from tear fluid. Moreover, when the cornea is covered with a contact lens, then it is completely deprived of oxygen and other nutrients. Sometimes attempts to compensate for the lack of oxygen provoke the formation of new vessels, which over time grow into the corneal tissue. This process can result in a deterioration in visibility and the creation of visual interference, which together leads to a sharp decrease in vision. But soft lenses capable of preventing the possibility oxygen starvation cornea and solve the problem of vision correction.
Soft lenses can be made from a hydrogel polymer. Similar material has already been confirmed good compatibility with eye tissues, but sometimes it can cause ocular hypoxia, that is, lack of air. After the implants are installed, air is delivered to the cornea using water contained in the lens. That is, the more water there is in the optics, the more oxygen it can receive. But water tends to evaporate quickly. A person will immediately feel discomfort when wearing it, which indicates that the lens has dried out. When its water content exceeds the norm, it will no longer be able to retain its shape well.
The maximum possible oxygen transmission capacity of hydrogel lenses is no more than forty conventional units. But ophthalmologists claim that to prevent chronic hypoxia, the cornea must receive more intense doses of oxygen, which amount to a coefficient of eighty units or more.
Soft models can also be made from silicone hydrogel. Thanks to the two components of the lens, it is ideally compatible with the eye tissue and, most importantly, does not interfere with the normal supply of oxygen to the cornea. Silicone is such a versatile material that it can easily provide high oxygen throughput up to one hundred and fifty conventional units. This fact completely eliminates the possibility of insufficient nutrition of the cornea. The hydrogel also helps to moisturize the cornea and make the lenses comfortable to use.
Lenses of this type include less water, so evaporation of liquid is not a problem for them. Their worthy prerogative is the ability to use for a long time, without feelings of discomfort or excessive dryness. This can be explained by the fact that the manufacturer introduces special additives for moisturizing into finished products. In addition, the optical mirror passes strict methods processing using plasma materials. Such properties of these contact lenses make it possible to use them without interruption during sleep.
Due to their high density, soft lenses are easier to put on and take off, because they can keep their shape perfectly for a long time. The next advantage is that lipid and protein deposits do not appear in them over time, and this, in turn, extends their comfortable use.
Your ophthalmologist can offer you two types of silicone hydrogel contact lenses. The first ones can be safely worn for a week in a row (without being distracted by nighttime removal), and the especially durable ones allow you to use them for a month. They are perfect for those people who work for a long time without breaks, for example on duty or in a security environment.
Modern silicone hydrogel lenses help correct not only the manifestations of myopia or farsightedness. but even forget about astigmatism.
Features of hard contact lenses
Innovative models have such an important characteristic as gas permeability. This contributes to the normal ability of the cornea to receive air and nutrients from the environment. Like soft options, hard lenses have silicone as their main component. This material was not chosen by chance, because, despite its strength, it does not protect the surface of the cornea from air supply. Some lens designs may exceed the gas permeability characteristics of soft material counterparts. Although soft silicone options can boast high coefficient breathability, but they are still inferior to hard silicone models. No matter how paradoxical it may sound, hard gas-permeable contact lenses have a more gentle effect on eye health than soft counterparts.
In addition, there are many positive aspects associated with hard contact lenses, such as:
Of course, hard lenses cannot be ideal in use, as they have several negative aspects. As a rule, patients need some time to adapt and this period lasts on average at least a week. But after this, patients noted the disappearance of unpleasant sensations if there was no break in wearing lenses for a couple of days. In this case, you need to be prepared to get used to the lenses again.
Some people have noted that after they used hard lenses, their correction with glasses stopped working. That is, when using glasses, vision did not improve, it remained at the same level, and the image was devoid of clarity. This often happens because hard lenses can actually change the shape of the cornea. But if you take breaks for a while, the shape of the cornea and visual acuity are gradually restored. Therefore, there is no need to rush and give up using hard lenses prematurely.
In truth, the process of fitting lenses based on hard silicone is complex, because the doctor must ensure the ideal ratio of the hard lens to the surface of the cornea.
Contact lenses are an excellent option not only for correction, but also for preserving vision for a person of any age. The most important step on the way to good vision is to choose the most acceptable option. To do this, you will need to undergo a qualified examination by an ophthalmologist, as well as follow all his recommendations and prescriptions. In no case should you violate the wearing regime of lenses, regardless of their type.
Rigid gas permeable contact lenses: reviews, manufacturing. Hard Contact Lens Care: Daily Cleaner for Hard Gas Permeable Contact Lenses
December 8, 2015
Today there are many ways to correct vision. Very often, contact lenses are used to improve its severity and eliminate other problems. Depending on the type of material, soft and hard gas permeable contact lenses are distinguished. Of course, the first type is most often used, however, the latter also have many advantages.
Materials for making hard lenses
Hard lenses purchased wide use at the end of the twentieth century. Then the main material for their manufacture was polymethyl methacrylate. The lens itself was relatively small in size. The disadvantage of such lenses was the lack of gas exchange. Access of oxygen to the cornea was achieved only due to the mobility and small size of such a correction device. However, today more modern and high-quality materials are used. Rigid gas permeable contact lenses are made from fluoro-silicone compounds. Thanks to this, the lenses have good oxygen permeability. It is worth noting that they are quite comfortable, they are made individually, and an exact fit is made for a specific patient.
Indications for the use of hard lenses
Soft contact lenses have limitations in their optical power range. They are often prescribed for myopia up to -12 diopters, myopia no higher than 8 diopters. A more severe degree of myopia requires specific correction. Soft lenses with high optical powers will have considerable thickness in this case. This, in turn, increases the risk of complications (tight fit can lead to eye hypoxia). You can, of course, use glasses, but today experts offer modern rigid gas-permeable contact lenses. They have wide range refraction - from -25 diopters to +25 units. The use of modern material ensures sufficient oxygen supply to the eye. Moreover, the thickness of such lenses is not much different from the corresponding parameters of soft products for vision correction. 
Hard Lens Design
Modern hard lenses have an optical zone that is located in the center of the product. Its diameter does not exceed 8 mm. Thanks to the sliding zone, which has a specific structure, the lens is securely fixed on the eyeball. The marginal region has the smallest dimensions. It is she who is responsible for comfortable wearing of the product, provides normal exchange tear fluid under the lens.
The main advantages of these lenses
Many patients note that rigid gas-permeable rigid lenses are less susceptible to deformation and creasing. Due to the fact that their diameter is slightly smaller than that of soft lenses, such products leave the peripheral zone of the cornea open. This, in turn, does not disrupt the tear exchange process. They are also more resistant to protein deposits, so the period of safe operation increases. Since the composition is completely free of water, hard lenses cannot dry out, the patient does not need to use special moisturizing drops. It is important to note their cost-effectiveness: the indication for replacement is only a change in visual acuity. Rigid contact lenses are also indicated for astigmatism. Reviews from patients indicate that correction with soft lenses in this case is quite difficult; the only option is to use hard products. Orthokeratological correction is also widespread. It involves the use of hard lenses only at night. 
Orthokeratology. What is the essence of the technique
This type of vision correction allows you to maintain your vision sharpness during the day, but at night you need to wear special lenses. During sleep, the cornea of the eye changes; its optical zone becomes flatter. This form remains for the next day. As a rule, the effect of such a correction can last two days. Night lenses are good for children, patients with a progressive form of myopia, if there are contraindications for surgery to restore vision. Also, this method is often chosen by people of certain professions: athletes, military personnel, builders, etc. Contraindications to orthokeratology therapy are diseases of the cornea, eyelids, all kinds of inflammatory processes, and dry eye syndrome. 
Disadvantages of using hard lenses
In addition to the above advantages, hard lenses also have their disadvantages. First of all, a certain period of adaptation is required (about a week). After getting used to it, the discomfort disappears, but even a short break in wearing requires new getting used to the products. Some degree of corneal deformation is observed if rigid gas permeable contact lenses have been used. Reviews from patients indicate that using glasses after such lenses does not bring the desired result: the image becomes blurry and the sharpness decreases. However, this is a temporary effect. After the cornea has been restored, you can safely use glasses without losing the quality of your vision. Also, the process of selecting products is quite lengthy; their initial cost will also be an order of magnitude higher than that of soft lenses. 
How to choose the right gas permeable lenses
In order to choose hard lenses wisely, you first need to consult a specialist. It determines visual acuity and the maximum degree of correction. Using special equipment, the ophthalmologist measures the necessary parameters of the patient’s cornea. What follows is trying on several pairs. All these manipulations are necessary for perfect lens fit. The production of hard contact lenses is carried out purely individually, taking into account more than 20 parameters of the eye. The engineer models the required design (optical zone, sliding zone, edge region). Next, the product is turned on a special machine in full accordance with the layout. Most famous manufacturer in this area - the German company Wohlk. This manufacturer ensures high quality products. As a rule, after 14 days you can receive a ready-made set of lenses. 
Daily care of hard contact lenses
First of all, any lenses require proper personal hygiene. Hands should be washed with soap and water before removing or putting on. It is best to wipe them with a waffle towel to avoid getting various lint on the lens. Storage containers must be kept clean. For women there are special rules. Makeup should only be applied after the lens is in place. Accordingly, remove it after removing the product from the eye. A daily cleaner for hard gas permeable contact lenses is also necessary. With its help, impurities and tear fluid are removed. A deeper cleaning is carried out once a week. It is worth noting that you cannot rub the lenses too much, so as not to disturb the optical properties. Today, a multifunctional cleaner for hard contact lenses is widely used. It allows you to effectively remove protein deposits (for example, Boston Simplus solution) and does not require additional enzymatic purification. It also perfectly disinfects and softens contact lenses. Over time, the product becomes more difficult to clean. In this case, hard lenses can be polished in a special laboratory. 
Special requirements for owners of hard lenses
Wearing hard lenses imposes certain responsibilities on the patient. Visits to the ophthalmologist should be regular. This will enable the specialist to assess the condition of the eyes. If there is the slightest change in the condition of the eyes, you should consult a specialist. Timely treatment will help avoid conditions such as corneal edema, microbial keratitis, conjunctivitis, corneal ulcer, allergic reactions. Rigid gas permeable contact lenses - excellent remedy for vision correction in many cases, but they require proper and careful care.
Hard contact lenses
Yashina Olga Nikolaevna
Candidate medical sciences, Head of the Department of Refractive Pathology
In the world of contact correction, the leader is, of course, occupied by soft contact lenses.
In the minds of the average person, hard lenses are associated with the very first contact lenses, which were made first from glass, then from polymethyl methacrylate (PMMA). These lenses were very uncomfortable to wear, did not allow oxygen to pass through at all, they had to be boiled, special cleaners used, etc.
Today, rigid lenses generally refer to gas permeable contact lenses (GP lenses).
What are the features of hard lenses?
If the contact lens has low gas permeability, then the cornea under it “does not breathe.”
Modern rigid gas permeable lenses are made from silicone-based materials. As you know, one of the most important characteristics of any contact lenses is the oxygen transmittance coefficient (Dk/t).
The cornea receives oxygen from the surrounding air, and if the contact lens has low gas permeability, then the cornea “does not breathe”, chronic hypoxia, corneal edema, and vascular ingrowth develop - all this leads to a decrease in the transparency of the cornea and, in the long term, to irreversible deterioration of vision.
Silicone has high gas permeability - many times higher than soft contact lenses. Silicone hydrogel contact lenses have a fairly high oxygen transmittance, but still this indicator inferior to hard silicone-based lenses.
Providing a high supply of oxygen, rigid gas permeable lenses have minimal impact on the physiology of the cornea and are the safest for the health of your eyes.
Benefits of rigid gas permeable lenses
In addition to high oxygen transmission, rigid gas permeable contact lenses have other positive properties:
Most importantly, rigid gas permeable lenses can provide better visual acuity in some cases compared to soft contact lenses:
Disadvantages of hard lenses
It will take you some time to get used to wearing hard contact lenses.
Hard contact lenses are naturally inferior to soft lenses in terms of wearing comfort. It will take you some time to get used to them. Adaptation can reach 5-7 days, then most users stop feeling any discomfort, but if you take a break from wearing them for at least a few days, you will have to get used to hard lenses again.
In some patients, after wearing hard lenses, spectacle correction no longer works, i.e. If such patients remove their lenses and put on glasses, their vision is poor and the image is blurry.
This is due to the fact that hard lenses slightly change the shape of the cornea (the same principle, only to a greater extent, underlies orthokeratology). Gradually, the cornea returns to its shape and vision with glasses is restored, but many users stop wearing hard lenses as a result.
The selection of rigid gas permeable lenses is more complex compared to soft contact lenses, since a rigid lens must perfectly fit the surface of the cornea, accordingly, the time required to select lenses will be longer and the cost will be higher.
Technologies for the production of rigid gas permeable lenses are constantly evolving. Manufacturers strive to create lenses that are as comfortable as soft contact lenses. But today, many users primarily choose the safety and health of their eyes, giving preference to gas permeable lenses.
Hard contact lenses
Hard contact lenses are often perceived as outdated, uncomfortable optics made of glass and polymethyl methacrylate. Such samples previously did not allow oxygen to pass through and required boiling and the use of purifiers. Modern LCDs are gas permeable. The site obaglaza.ru will introduce you to positive qualities this "solid" optics.
Features of LCD
The Dk/t coefficient, which characterizes oxygen permeability, is important for any contact lenses. The cornea of the eye will not receive oxygen from the atmosphere and will not breathe if the optics material has low gas permeability. Consequences &minus swelling, hypoxia, vascular ingrowth. Vision is irreversibly deteriorated due to decreased transparency of the cornea.
Today, rigid gas permeable lenses are made from silicone-based raw materials. Their Dk/t value exceeds that of soft contact lenses (even silicone hydrogel). Therefore, GCLs have minimal impact on the cornea. The gentle effect on the eyes has a positive effect on their health.
Advantages and disadvantages of hard GP lenses
Advantages
- Thanks to high density Made from the original material, hard contact lenses retain their shape and wrinkle little when blinking, ensuring image stability.
- It attracts users, especially older ones, because it is easy to use. LCD cannot be accidentally torn, but can be broken purely theoretically.
- From the tear fluid they reach the optics protein deposits. The resistance of the surface of hard lenses to them increases comfort and prolongs the period of safe wearing.
- The peripheral extreme zone of the cornea is accessible to oxygen, since its diameter is slightly larger than the diameter of the GCL. A tear washes away dead cells and foreign particles without interference.
- The material used to make hard contact lenses contains no water. In unfavorable conditions ( strong wind, heat) they do not dry. There is no need to use moisturizing drops.
- Economic benefit: the duration of use is unlimited, with the exception of changes in the patient's vision. Obaglaza.ru specialists advise only to properly care for your optics.
Rigid gas permeable lenses sometimes provide better quality vision. Cases when correction using LCD is preferable:
Flaws
You need to get used to wearing hard lenses; they are not as comfortable as soft ones. Adaptation occurs within a week, the main thing is not to interrupt wearing, otherwise you will have to adapt again.
Some patients who wore GCLs experience a decrease in vision with glasses and the cessation of the effect of spectacle correction. Hard lenses act on the cornea, changing its shape. However, it is gradually restored with a pause in the use of liquid crystal lenses, and visual acuity returns when wearing glasses. Obaglaza.ru recommends taking this nuance into account and not rushing to categorically exclude the use of such contact lenses.
It is difficult to choose rigid GP lenses - the optics must ideally fit into the surface of the cornea. This also determines the high cost of housing and communal services.
Selection of hard contact lenses
Continuous improvement of production technologies is a priority for manufacturers of rigid gas permeable lenses. Hard optics are constantly approaching soft optics in terms of comfort, which encourages users to prefer safe hard GP lenses.
Great quantity medical centers with detailed eye examination services, diagnostics, selection of optics suitable for a particular patient. The choice of the necessary treatment should be trusted only to professional ophthalmologists, experts at obaglaza.ru are confident. Never neglect a comprehensive eye examination.
IN Lately Contact lenses are becoming the main means of vision correction.
It’s understandable, it’s convenient, it provides a full view (and not cut off at the periphery like glasses), they don’t need to be adjusted (at least not as often as glasses), and generally lead an active lifestyle.
Year after year, lenses become more and more comfortable and safe, and lenses released just 10 years ago cannot be compared with what is produced now. But, as happens with any product of progress, we often do not know how they are produced. Let's briefly look at production methods, but for a better understanding of the technical process, let's look at the types of contact lenses that exist.
Types of contact lenses
In general, contact lenses are divided into two groups (according to the degree of hardness):
- Soft;
- Tough.
Hard contact lenses
Rigid lenses were invented back in 1888 (by Swiss ophthalmologist Adolf Fick, although drawings of nothing similar were found by Leonardo da Vinci, but the first “working” prototypes were created by Fick). They are used for vision correction in severe cases (such as astigmatism), as well as orthokeratology (changing the shape of the cornea using a special lens).
Due to their rigidity and shape, the use of these lenses can maximize visual acuity. The main disadvantage is that hard lenses are much more likely to cause eye irritation than soft ones.
Soft contact lenses
Soft lenses were invented in 1960 (by Otto Wichterl and Dragoslav Lim, from Czechoslavakia), and since then 90% of contact lens wearers on the planet have switched to them. They were called “soft” because of the main polymer in their composition. He has unusual ability absorb water (up to 38% of its weight) and when saturated it becomes very soft and elastic. Subsequently, this polymer was improved.
And now soft lenses are divided into 3 classes (based on the name of the polymer included in their composition):
— Hydrogel (invented in the 1970s);
— Silicone hydrogel (invented in 1999);
— Water-gradient (presented in 2016);
Silicone hydrogel lenses, in addition to their high elasticity, have become permeable to oxygen (although it would be more correct to say that the cornea receives the necessary oxygen through the liquid of the lens; in any case, this was a “breakthrough” for soft lenses).
Doesn't have its own blood vessels, and the supply of oxygen and nutrients comes from the regional vascular network(in the case of oxygen, also partially from the environment), which is located along the periphery of the cornea (in the so-called limbus region). And the main problem of lenses is the creation of oxygen starvation of the cornea (in scientific terms - hypoxia), because the lens covers the cornea, which does not receive the oxygen it needs in the required amount. Hypoxia stimulates the production of special substances, which in turn cause the growth of old and the appearance of new vessels, which will have to compensate for the lack of oxygen (neovascularization).
However, along with new vessels, dense fibrous tissue will grow on the cornea. It allows the body to heal damage faster. But this fibrous tissue is not transparent. And this can subsequently manifest itself as visual interference (an incomprehensible veil before the eyes), deterioration of vision (up to its complete loss). Therefore, doctors recommend that you be careful when choosing lenses, and even more so advise not to leave them on overnight (this was one of the reasons that spurred the creation daily lenses).
In other matters, silicone hydrogel lenses became the first lenses suitable for continuous use for quite a long time (from 7 days to 30 days), this is due to the slower evaporation of water from the surface of the lens, and the cornea remains moisturized longer.
The next step in the development of soft lenses was water-gradient lenses. The researchers set the task of combining the high permeability of the lens to oxygen and its high moisture content. And they succeeded. The moisture content of such lenses is 2-3 times higher than that of the best silicone hydrogel analogues, and the thickness is close to a record 80 micrometers (people who previously wore lenses of other types described that water-gradient lenses are almost not felt).
Methods for making contact lenses
Currently used in the medical industry following methods production:
— Centrifugal molding;
— Turning;
— Casting;
— Pressing;
In addition to the above, production techniques are used that combine some of the above methods.
Centrifugal molding
The very first method of making soft lenses, invented by employees of the Institute of Macromolecular Chemistry in Prague in 1960 (in fact, like the soft lenses themselves). The method, however, is still used today. Its essence is simple, it lies in the fact that the required portion of liquid rotating at a certain speed gradually solidifies.
At the first stage, the liquid monomer is placed in a special mold (representing a cylinder with a concave bottom) which then begins to rotate. Under the influence of centrifugal forces, the liquid monomer spreads inside the mold. Due to the fact that there is a certain amount of monomer in the mold, it rotates at a certain speed and all this happens at a certain temperature, the monomer hardens in the desired form (polymerizes, or simply turns into a solid polymer). Often faster hardening is achieved by using ultraviolet rays.
The hardened polymer preform is removed from the mold and hydrated. In short, this is the process of saturation with water (absorption) to the desired concentration. The main difficulty with hydration is that after hydration the dimensions of the lenses will be different than initially, so a preliminary calculation of the change in the geometric dimensions of the contact lens is carried out.
This is followed by computer photo control (size, shape, quality of polishing, etc.), after which the sterilization stage begins. During the sterilization process, the surface of the lenses is cleaned of all microorganisms that “settled” on the lens during the processing of the original polymer blank. Usually they also use ultraviolet radiation (occasionally microwave), but they can also use chemicals (something based on hydrogen peroxide), or the old proven method is to heat the lens to 120 degrees and wait a little.
After sterilization, all that remains is for the contact lenses to be tinted in the desired color (if necessary), packaged and labeled. Ready-made packages of contact lenses are stored in sealed containers at a constant temperature. But that’s not all, a certain part of the percentage of all finished lenses is sent to the laboratory for more detailed quality control, and if everything is fine, then the entire batch is sold.
Rotomoulded contact lenses have an aspherical back surface (not spherical, but its shape depends mainly on the centrifugal force acting on it during the hardening process in the mold). Centrifugal molding is the cheapest production method. You can get soft contact lenses with a thin outer edge and good performance.
Turning
The method is suitable for the production of both soft and hard lenses (for example with high optical characteristics).
Solidification of the monomer occurs in forms that are not subject to rotation. After solidification, the workpieces are transferred to a computer-controlled lathe, where, using specially developed software, lenses with complex geometric shapes (for example, with several radii of curvature) can be obtained. This requires maintaining constant environmental conditions (temperature +22 degrees, relative humidity 45%).
After turning, to give the surfaces the necessary smoothness, the lenses are sent for polishing. The lenses are then hydrated, chemically cleaned, quality controlled if required to be tinted, and sterilized.
But this method is about 4-5 times more expensive than centrifugal molding.
Casting
Casting (also called “in-mold polymerization”) is a less expensive method than turning. First, a metal matrix mold is cast (unique for each set of lenses), polymer copy molds are cast over it, into which the monomer is later poured. It hardens with the help of ultraviolet rays. The resulting solid polymer is sent for polishing and, depending on the required hardness, it is hydrated. And then, similar to other production methods - tinting, quality control, sterilization, packaging and labeling.
With the invention of silicone hydrogel contact lenses, after casting into a mold, they began to use plasma (the lens is placed in a special liquid through which it is passed electricity certain type) polishing. This allows for increased future wettability of the lens.
Currently, soft contact lenses for routine replacement and approximately half of disposable (one-day) lenses are produced by casting.
Pressing
Occasionally, a production method that is no longer particularly popular, such as pressing, is used. This method is reminiscent of casting, only the liquid monomer is not poured into the mold, but the already hardened polymer “blank” is pressed using specially prepared molds (dry pressing), or the “blank” that has undergone hydration is pressed directly
Mixed methods
The most common of the mixed methods is the so-called.” Reversible process III.” In it, the front surface of the lens is made by centrifugal molding, and the back surface is made by turning.
All this contributes to the fact that the front surface is extremely smooth (and this is comfortable to wear), and the back surface (adjacent directly to the cornea) has any fairly complex geometric shape.
As a result, contact lenses of the most complex shapes are produced using this method. Also a plus is the good oxygen permeability of the lenses. The disadvantages include a longer manufacturing process (in time), and more high cost production.
Promising types of contact lenses
Nowadays, it has almost reached the production of prototypes. new type lenses called “Bionic contact lenses”. Of course, this will be the next step in the evolution of contact lenses, because the lenses will include ultra-small electronic circuits. But how about modern lenses, bionic lenses will be of both a medical nature (vision correction) and an entertainment-professional nature (an electronic display in the eye). In the case of a medical application, it will even be possible to “correct” lens defects with electronics (say, due to inaccurate recording of the topography of the patient’s eye).
But the production of bionic lenses will also require a fundamentally new approach to their production. If production methods have already been worked out with the lenses themselves, then with the electronic filling it is more difficult. At the first stage, electronic circuits are made, assembled from metal plates several nanometers thick (1 millimeter is 1 million nanometers). On the other hand, the LEDs are planned to be only one-third of a millimeter thick, and applying them with tweezers will obviously not be easy, so they are sprayed as “powder” onto the surface of the lens. To accommodate such miniature components, a method called microfabrication or self-organizing assembly is used.
Finally
Unfortunately, the final result is still far away. Now the stage of searching for materials that will not irritate the user’s eye has been completed, and the fact of the direct presence of the emitting LED on the surface of the eye is also being studied. It is also too early to talk about the cost of such a “new product,” but it is clear that the first prototypes will be very expensive.
Hard contact lenses
Modern rigid contact lenses are made from gas-permeable materials containing silicone, which makes them more flexible than earlier gas-permeable PMMA lenses and also allows large amounts of oxygen to pass through the lens to the cornea. This allows rigid gas permeable contact lenses to provide a significantly more comfortable and healthier wearing experience compared to their gas-permeable predecessors, which are no longer commonly prescribed.
Benefits of hard contact lenses
Compared to soft contact hard lenses Gas permeable contact lenses provide significantly better vision because, due to their higher rigidity, they retain their shape during blinking and therefore the image remains stable at all times. Soft contact lenses crumple slightly when closing the eyelids, which leads to the fact that the picture seems to “float”.
With proper care, rigid gas permeable contact lenses can be worn for at least 1 year due to the fact that they are resistant to almost all types of deposits, since their surface is less porous and easier to clean than the surface of soft contact lenses. They are also more difficult to damage or tear than soft contact lenses.
Rigid contact lenses are made taking into account the individual parameters of the patient's cornea, so their shape is more congruent with the shape of the cornea, that is, it fits it perfectly. The mobility of a hard contact lens is 2-4 times greater than the mobility of a soft one. All this ensures a much better exchange of tear fluid in the sublens space and a much greater supply of oxygen to the cornea, and therefore a less frequent development of hypoxic (associated with a lack of oxygen) complications.
In addition, there are situations where soft contact lenses cannot be offered to the patient in principle and hard contact lenses are the only option. possible means vision correction for such people.
Hard contact lenses for high degrees of myopia (nearsightedness) and hypermetropia (farsightedness)
The range of optical power (diopters) of most modern soft contact lenses does not exceed -12.00 D - +8.00 D. And the properties of the materials of those contact lenses that will provide high-quality vision at higher degrees of myopia and farsightedness ( up to 20.00 D), unfortunately, leave much to be desired, so wearing such soft contact lenses often leads to the development of complications. In addition, you need to understand that the higher the degree of myopia, the thicker the soft contact lens along the periphery, and the higher the degree of hyperopia, the thicker it is in the center, which, taking into account the tighter fit compared to hard contact lenses, again leads to the development of hypoxic ( complications associated with a lack of oxygen supply through a thick lens) when wearing soft contact lenses.
What can these unfortunate people do? Or be content with incomplete and insufficient correction, depriving yourself of the opportunity to see and enjoy well full life, or use soft contact lenses, wearing which will almost inevitably lead to the development of complications. They, of course, can be offered spectacle correction, but in glasses with such diopters, peripheral aberrations (distortions) will be very pronounced, which will make their use very uncomfortable, and their aesthetic properties will be very questionable ( spectacle lenses will be thick, and the eyes behind them will be either very large with high degrees of farsightedness, or very small with myopia).
But in reality there is a choice! Rigid contact lenses tend to have a wider refractive range ( -25.00 D to +25.00 D), and due to the use of materials with a high refractive index, they remain quite thin even at large diopters. In addition, due to better exchange of tear fluid in the sublens space, they ensure adequate oxygen supply to the cornea.
Rigid contact lenses for high astigmatism
The optical power of the cylinder of most toric soft contact lenses does not exceed 2.25 D, some of them have restrictions on the axes of the cylinder, which in some cases makes it impossible to provide high-quality vision to patients who need it.
Rigid contact lenses, due to a fundamentally different system for correcting astigmatism, make it possible to cope with this problem.
Hard contact lenses for presbyopia (age-related farsightedness)
To correct vision in patients over 40 years of age, in addition to glasses, special multifocal soft contact lenses can be used. But all multifocal soft lenses presented on the domestic market have limitations on optical power for distance ( -10.00 D to +6.00 D) and cannot be offered to patients with astigmatism, since toric multifocal soft contacts are not represented in our country in principle.
Hard contact lenses do not have such restrictions: they can be selected for patients over 40 years of age, both with high degrees of farsightedness and myopia, and for those who have astigmatism.
Selection of hard contact lenses
So what exactly is the selection of hard contact lenses?
This procedure is carried out on the basis of examination data using an autorefractometer and visometry. After these studies are completed, lenses from a diagnostic kit are installed on the patient’s eyes, the “fit” of which is assessed after 20 minutes by a doctor during a slit-lamp examination and fluorescein staining. The visual acuity obtained with hard contact lenses is also checked. As a rule, in most cases, successful fitting requires trying on 1 to 3 diagnostic hard contact lenses in each eye. This is necessary in order to achieve complete perfect compliance of the shape of the inner surface of the hard contact lens with the surface of the cornea, and thereby ensure its correct centering, sufficient mobility and, as a result, ensure comfortable and healthy wearing.
After completing all the described procedures, having decided on the parameters of the hard contact lenses the patient needs, we can send an order for their individual production.
Manufacturing of hard contact lenses
Wanting to offer our patients the best, we collaborate with the German company Wöhlk, which has 60 years of experience in producing premium hard contact lenses. The level of this company is evidenced by the fact that such an optical giant with a worldwide reputation and excellent reputation as Carl Zeiss entrusted it with the production of its soft contact lenses. The Wöhlk plant is located in northern Germany in the town of Schenkirchen, and every product produced there is subject to the most stringent controls and has a guarantee of the highest quality. All orders for hard contact lenses are manufactured using high-precision equipment according to the individual parameters of each individual patient. The waiting time for such an order, including delivery from Germany, is usually 14 working days.
Training and dynamic observation
If you want to wear hard contact lenses, it is important to understand that they not only provide high quality vision, but also impose significant responsibility. Wearing such lenses requires more frequent visits ophthalmologist for dynamic assessment of eye condition than when using glasses and soft contact lenses. Yes, and lenses require certain procedures when caring for them. An important factor in the safety of wearing them is compliance with hygiene rules, including when putting them on and taking them off.
That is why in our vision correction offices final stage When dispensing hard contact lenses, we inform our patients in detail about how to wear and care for them correctly.
An indispensable condition is to purchase a starter kit, which includes a set of all the necessary tools and accessories for the first time.
When purchasing a starter kit patient education independent skills of putting on and removing hard contact lenses, if they are choosing lenses for the first time, as well as dynamic observation by an ophthalmologist during the entire period of wearing the lenses, for free.
They are not in the most favorable conditions, and they are also deprived of government support, but companies are doing everything in their power to win the fight for their place in the market. In this article we will review the state of affairs in this segment of the domestic manufacturing sector.
If you look at the developed markets for contact vision correction, say, EU countries, then, as follows from regularly published reports from various agencies (for example, Eurom Contact), it is quite obvious that these markets are mainly filled with routine replacement contact lenses produced by large companies . These products have, to a certain extent, displaced traditionally worn contact lenses from the market. According to leading managers of large manufacturing companies, traditional contact lenses occupy a new niche for them: increasingly, these are contact lenses for those people who have limited funds, as well as special contact lenses made according to an individual prescription. Although, according to some production workers, the latter are, one might say, the bread of contact vision correction laboratories working in various regions of the country.
Apparently, a similar fate awaits traditional soft contact lenses in our country, although they currently occupy a fairly large market share (according to various estimates, up to 45% of the market). Just don’t think that this conclusion was made hastily - in principle, the Russian production workers themselves, with whom we were able to talk on this topic, agree with it, and it is to them that we will give the floor in the published material. But first, let's list those companies that produce contact lenses. This enterprise "" (Vologda) is the largest in terms of production volume, the companies "Opticon" (Moscow), "" (Ufa), "Octopus" (Samara), "Nevskaya Optics" (St. Petersburg), "Contlens", ( Arkhangelsk), "Likont" (Volgograd), PE Kunina (Belgorod) and some others. They all produce traditional wear soft contact lenses using the turning process.
To find out what problems our manufacturers face and what prospects they see for the development of their enterprises, we talked with representatives of a number of the above-mentioned companies and asked them to answer a number of questions. The director of the Concor company Viktor PROSYANYUK, the director of the Optikon company Boris DYMAN, the representative of the Optimedservice company Ural YANTURIN and one of the managers of the production and implementation company Octopus Sergei GOLOSCHAPOV shared their thoughts on this topical topic with us.
Veko: What share of the contact lens market, according to your estimates, is occupied by domestically produced products?
Victor Prosyanyuk: According to our research, about 50 percent, half of which are made by contact lenses produced by Concor.
Boris Dyman: Currently, it is difficult to estimate the market share occupied by domestic traditional contact lenses, but based on the total production volumes - which is approximately 30-40 thousand pieces per month - we can assume that this share is 10-15 percent, no more.
Veko: How do you see the prospects for the development of domestic production of contact lenses?
Victor Prosyanyuk: The sad thing is that things are not going very well for Russian manufacturers at the moment, some enterprises are even closing. It turns out that there is no single development program, no support from government programs, and our production is forced to follow the lead of large Western companies. One of the main problems is dictated by our market price policy. If, say, in the West, traditional contact lenses are sold for 8-10 dollars apiece, then we are forced to set the price for scheduled replacement contact lenses - 2-3 dollars, as a result of which we work at extremely low profitability, almost to the limit. As a result, we cannot afford a broad advertising campaign and the purchase of more modern production equipment necessary for the manufacture of modern products - scheduled replacement contact lenses, contact lenses in blisters, solutions for the care of contact lenses.
Boris Dyman: The future lies in planned replacement contact lenses, the production of which is almost impossible for our entrepreneurs. Therefore, traditional contact lenses will be forced to occupy a niche product for citizens with a low level of material income, as well as for those people who are conservative in their views and are accustomed to these contact lenses, although the funds allow them to buy more expensive contact lenses for routine replacement. And this will definitely happen - a year earlier or a year later.
Sergey Goloshchapov: I don’t see any positive trends in the domestic production of contact lenses. I just look at things realistically, since I myself am a co-owner of a chain of optical stores and I see the dynamics of growth in sales of scheduled replacement contact lenses from 10-15 percent in 1997 to 87 percent in 2003. Sooner or later, traditional contact lenses will be forced out of the market, and our manufacturers will have, like in the West, to switch to the production of special contact lenses - for keratoconus, toric (astigmatic contact lenses), with high refraction; the rest will be taken up by scheduled replacement contact lenses. And it is not possible to start the production of planned contact lenses in Russia from scratch, unless Western companies themselves build here production capacity and will finally bring down prices.
Veko: How would you assess the state of the contact vision correction market, does it contribute to the development of our enterprises?
Victor Prosyanyuk: The market has great potential - so far the share of the population using contact lenses is 1.5 percent. If you look at European countries, the share there is 5-7 percent. It is to be expected that our market should achieve a similar share of contact lens penetration. Therefore, the market has great potential. In the contact correction market itself, alarming trends are observed - the number of primary patients is decreasing. This suggests that contact doctors should think more about their civic responsibility: their task is not to sell contact lenses, but to provide a person with full vision so that he is satisfied with the service. Then he will continue to use contact lenses. In the meantime, it turns out that the number of misconceptions about contact lenses as a correction method, which is fraught with terrible complications, is growing in society.
Sergey Goloshchapov: In 2003, our sales increased by 20 percent, and, in principle, since the founding of the company, annual growth has been 15-20 percent. Sales are currently carried out in all regions of the Russian Federation and other CIS countries. The most popular contact lenses are “Elite-38” with 38 percent moisture content.
Internal competition has established in the market between domestic producers, so that the price has frozen around 2-2.5 dollars per unit of product. Profitability is declining, and at the moment it is very low - although prices for the cost of materials do not change, costs for rent, electricity, wages and so on, and therefore the cost increases.
Ural Yanturin: Over the past year, sales of contact lenses grew by 20 percent. This is due to the fact that we pursued an active marketing policy: we participated in all regional and central exhibitions and gave a lot of advertising. Are there any difficulties? Yes, in principle, no - there is good demand for our product. You just need to work more - and things will go well. The profitability of production is, of course, low. But you can stay afloat, you just need to work.
Eyelid: Many experts believe that lenses with 38 percent moisture content are unsafe for patients' eye health. Is it then worth producing such lenses at all?
Victor Prosyanyuk: Of course, we understand that contact lenses with a moisture content of 38% cannot be recommended to be worn all day. That is why we urge doctors to remember their civic responsibility and sell vision, not contact lenses. It is necessary to explain to patients the peculiarities of wearing contact lenses with low moisture content. Again, recognizing the disadvantages of contact lenses with 38% moisture content, we produce contact lenses with 70% moisture content. And now 55 percent contact lenses should be officially registered. We are also going to produce contact lenses with a 67 percent moisture content from materials from the Kontamak company - Contaflex 67.
Personally, I myself have nothing against scheduled replacement contact lenses: they need to be available in an assortment. But based on the situation in our country, offices also need to have traditional contact lenses. Not all residents of the country can now afford to change contact lenses every month; for them it is expensive. They need traditional contact lenses that last longer before being replaced with new ones.
Eyelid: Are there any difficulties with lens materials?
Victor Prosyanyuk: Of course I have. For example, “seventy” (with 70 percent moisture content) from “Lamda Polytech” does not suit us very much - its material characteristics fluctuate from batch to batch, so each time we need to reconfigure the calculation tables before production, having first run several dozen blanks. Also, when contact lenses are hydrated, the vinyl-propylene bonds of the polymer are poorly washed out, as a result of which some patients complain of a burning sensation in the eyes.
Veko: How can your company compete with the expansion of large Western manufacturing companies?
Victor Prosyanyuk: We can counter large companies with our strengths. Firstly, our contact lenses have a wide range of parameters - from -20 to +20 diopters. As a result, contact vision correction offices often purchase, say, from Bausch & Lomb lenses with a refraction of up to -6 diopters, and the rest from us. And then, having tried them, they buy all the refractions from us. Secondly, with turning and three-stage quality control, we give defects at only 1.5 percent. The contact lens is checked for chips, microcracks, etc. after dry turning, then after hydration, and again before packaging. And another thing is contact lenses produced by stamping in large factories, such as, say, the same company Bausch and Lomb - as far as I know, they check the quality of only 10 percent of the product batch.
Therefore, and I am convinced of this, according to our GOSTs, exported contact lenses for planned replacement should be considered defective in 90 percent of cases. Our traditional contact lenses are much better quality. Please understand me correctly: I am not against any specific Western companies, but against the ideology of the dominance of planned replacement contact lenses. These contact lenses are manufactured with lower quality requirements, and accordingly, their recommended wearing period is sharply reduced. Traditional contact lenses can be worn more often, as their quality is higher.
Thirdly, we have the widest dealer network - there are no regions where we do not have an official representative office. Therefore, our contact lenses are more affordable and therefore the demand for them exceeds the supply.
Sergey Goloshchapov: As for the ability to compete with Bausch & Lomb, it makes no sense. Our contact lenses are designed for low-income people who cannot spend more. If they have other money, they will definitely switch to scheduled replacement contact lenses - health is more expensive. Again, our production base is becoming outdated. Ten years ago we bought new Gfeller machines. Now they are already morally obsolete, and they are also physically worn out. Maybe they'll last another five years. What then? Then there will be contact lenses everywhere from Bausch & Lomb, Johnson & Johnson and other major Western manufacturers.
Ural Yanturin: Our contact lenses hold their shape well and are easy to handle when putting them on and taking them off - this is what appeals to some patients. But the future, naturally, lies in planned replacement contact lenses, so we understand that sooner or later the production of traditional contact lenses will be forced to switch to the production of special contact lenses, as happened in the West.
Veko: How to survive with such bleak prospects?
Sergey Goloshchapov: That is why we have to deal not only with contact lenses, but also with other areas of the optical business - for example, glasses, laser correction.
. . .
So, as follows from the statements of most of our interlocutors, the prospects for the domestic production of contact lenses for traditional wear are not very bright. The market is increasingly filled with inexpensive contact lenses for routine replacement produced by large Western companies, and public awareness is growing that contact lenses for routine replacement are safer for eye health than contact lenses that are traditionally worn and have low moisture content. Accordingly, sales of foreign-made contact lenses are growing. However, at the same time, sales of Russian companies are also growing. Thus, most of our interlocutors noted an increase in sales of contact lenses of their own production over the past year - by an average of 10-15%. In principle, this is explained by the fact that the country is currently experiencing growth in the market for contact vision correction, and it is being filled with products from both Western and Russian companies. This allows our manufacturers to stay afloat, and in the case of, for example, Concor, even expand production and produce new brands of contact lenses, since demand exceeds supply.
As for the future, it is, as follows from the words of our interlocutors, still quite vague. As can be seen from the answers to the questions, the forecasts are disappointing: either a reduction in production, or a complete re-profiling, or even withdrawal from the contact vision correction market. Only Concor, as the largest production facility, is most optimistic in this regard.
Russian manufacturers of contact lenses
Octopus
The production and implementation company "Octopus" is one of the largest enterprises in the Volga region producing high-quality soft and hard contact lenses. Contact lenses are made from material from Contamac (Great Britain) by turning on machines from Gfeller (Switzerland) using computer tools management. Here, the quality control of each manufactured contact lens is carried out.
The company was founded in 1993; so she turns 11 this year. In 1994, the company acquired production equipment from Gfeller (Switzerland), and a little later, with the help of specialists from Lamda Polytech Ltd. production was modernized. The range of manufactured contact lenses has also expanded: now Octopus produces soft contact lenses with 38 and 55% moisture content “Elite 38” and “Elite 55” from imported materials from Contamac, as well as hard and rigid gas permeable contact lenses. In addition to colorless contact lenses, Octopus produces cosmetic contact lenses using equipment from Lamda Polytech Limited.
Optimedservice
The Scientific and Medical Association (NMA) “Optimedservice” was created in 1993 and today occupies a leading position in the ophthalmological market of the Ural region. Since 1994, the company has been producing soft contact lenses under the “ ” brand on a computerized production line from City Crown (UK). One type of lenses is available: “Optimed-38” with 38% moisture content.
See more details here...
The Concor company appeared in 1991. Initially, the production of contact lenses was carried out using domestic equipment. However, it did not provide the quality of contact lenses sufficient to create competitive products, and in 1993 it was decided to purchase from Lamda Polytech Ltd. restored machines from Chase. This was a qualitative step forward, and products from Concor began to gain popularity among contact doctors.
Today the company produces soft contact lenses under the Concor brand - from the materials Hypolan-2, Benz-38 tint, LM-70VP. The registration process is for traditional soft contact lenses with 55% moisture content.
According to research conducted by the company, Concor products currently occupy Russian market 25%, another 25% is the share of the presence of other domestic manufacturers, and 50% are Western-made products, half of which are from Bausch & Lomb.
Optikon
The Optikon company was founded in 1991 by employees of NPO Medoborudovanie, who had extensive experience in the production of the first domestic soft contact lenses from the Hypolan material (as well as in the development and creation of this material itself). In addition to Gipolan, the company tried to produce contact lenses from materials from Lamda Polytech Ltd. and “Vista”, but in the end she chose the materials “Benz” and “LM”.
The Optikon company produces soft contact lenses for trademarks"Opticon 38" and "Optikon 72". The former are made from “Benz 38” material, the latter from “LM-70”; Colored versions of these lenses are also available.
Vadim Davydov, Veko No. 5 (79), 2004
