Manufacturing of contact lenses. Rigid gas permeable contact lenses: reviews, manufacturing
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 find good sharpness vision 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 in cost, and most importantly, they can protect the eyes from operations to restore vision. All surgical interventions create the likelihood 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 cornea of the human eye is specific, since it is devoid of blood vessels, so it is forced to receive oxygen and elements for nutrition 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 can prevent 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, than more water 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 also 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 boast a high degree of breathability, 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, with hard contact There are many positive aspects associated with 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 discomfort if there was no break while 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 stop using it prematurely. hard lenses.
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 path to good vision is choosing the most suitable 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
Rigid lenses became widespread 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 a wide range of 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 and ensures normal exchange of 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. She assumes 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, and various inflammatory processes, 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 is also necessary for rigid gas-permeable contact lenses. 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 damage 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 ulcers, and allergic reactions. Rigid gas permeable contact lenses are an excellent solution for vision correction in many cases, but they require proper and careful care.
Hard contact lenses
Yashina Olga Nikolaevna
Candidate of 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 a 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 develops, corneal edema, vascular ingrowth - all this leads to a decrease in the transparency of the cornea and long term to irreversible visual impairment.
Silicone has high gas permeability - many times higher than soft contact lenses. Silicone hydrogel contact lenses have enough high coefficient oxygen transmission, but still inferior to hard silicone-based lenses in this indicator.
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 production of hard gas permeable lenses are evolving all the time. 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 the positive qualities of 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.
- Protein deposits get onto the optics from the tear fluid. 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.
- In the composition of the material manufacturing hard There is no water in GP contact lenses. 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 vision best quality. 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.
There are a large number of medical centers offering detailed eye examination services, diagnostics, and selection of optics that are 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.
30-11-2011, 12:33
Description
In specialized laboratories in the country, both domestic and imported equipment is used for the manufacture of contact lenses.
The set of technological equipment includes: precision lathes for pre-processing (facing, preliminary rounding) of workpieces; sphere lathes for processing the inner and outer surfaces of lenses (Fig. 73, 74); polishing machines to remove roughness and improve the cleanliness of spherical lens surfaces (Fig. 75); special machines for polishing the edge of the lens and making technological equipment.
The machines are equipped with special devices and accessories, which include: a centering device, sets of mandrels and satellites for holding contact lens blanks during their processing, a set of parts for the manufacture of polishing pads.
Diamond cutters of a special profile are used as a cutting tool for processing the concave, convex and edge surfaces of lenses.
The composition of the technological equipment of the laboratory should also include: a heating cabinet for annealing workpieces, an electric hotplate with a thermostat for gluing and centering workpieces on mandrels, an ultrasonic bath for washing lenses and a magnetic stirrer for carrying out the hydration process of soft contact lenses.
When processing the surfaces of contact lenses, the following technological materials are used:
Compositions for the manufacture of polishing pad;
Polishing suspensions;
Bonded materials used to secure and center lens blanks during the turning process;
Polishing cloth.
In the late seventies and eighties, our country developed and then put into practice in laboratories of contact vision correction the following materials:
1. Compositions for casting polishing pads, consisting of fine abrasive powder, paraffin and polyethylene or polypropylene wax.
2. Polishing suspension for the treatment of hard lenses when using polishing pads, consisting of specially prepared barium carbonate, glycerin and water.
3. Polishing suspension for the treatment of soft lenses, consisting of fine magnesium oxide and kerosene.
4. Glued material (adhesive composition) for fixing and centering hard and soft lens blanks on a flat metal mandrel during lens turning, consisting of modified pine rosin and paraffin.
Production of liquid crystals by turning
Procurement operations
For the manufacture of rigid corneal contact lenses from PMMA, cylindrical blanks with a diameter of 12.0 to 12.5 mm and a thickness of 4.0 to 5.0 mm are used.
Workpieces of the specified sizes can be obtained from sheet material using a hollow tool (tubular drills or cutters).
Preparatory work
Before manufacturing LCL from PMMA The workpieces are annealed in order to relieve internal stresses in the material, leading to changes in the dimensions of the finished lens. To do this, the workpieces are placed in a laboratory oven, in which the temperature is set to +130-135°C, where they remain for at least 8 hours. Temperature fluctuations in the heating cabinet should not exceed ± 5°C. Then, over the next 8-10 hours, the temperature in the cabinet is gradually reduced to room temperature (the temperature is monitored using a thermometer). After cooling, the workpieces are removed from the heating cabinet and the residual stresses in them are checked using a polariscope for the presence of color patterns. Their observation is carried out from the side of the cylindrical generatrix, i.e. perpendicular to the axis of symmetry of the workpiece. If there are residual stresses, the annealing process is repeated. After annealing, the workpieces go into production.
For polishing lens surfaces preparing lapping-polishing pads. For their manufacture, a special polishing material PMP-3 or PMP-1, developed by the domestic industry, is used. Polishing material PMP-3 is used for polishing concave surfaces, and PMP-1 is used for polishing convex surfaces. The softening temperature of the polishing material is 100-120°C. It is possible to use imported materials.
To make a polishing pad, the material is melted in a porcelain cup until it becomes creamy. A brass shaping cylinder, placed on a special substrate, is placed on a hot electric stove. Before casting internal walls The cylinder is lubricated with petroleum jelly. The mold is then filled with molten polishing material. After the mold has cooled, the polishing pad is removed from the cylinder. As a rule, several polishing pads are produced simultaneously.
The technological process of manufacturing hard corneal lenses by turning includes the following steps:
Calculation of technological processing parameters (radii, thicknesses, diameters of the corresponding surfaces, spindle feed of a sphere lathe), based on the standard size of the lens being manufactured;
Processing the overall diameter and edge zone of the lens;
Turning and polishing of the concave surface of the lens, its control;
Turning and polishing convex surface, its control;
Polishing the edge zone of the lens;
Control of geometric and optical characteristics of the lens.
Turning and polishing of concave surface
Using a special glued wax material NV-N, the blank from which the lens will be made is glued and centered on a steel substrate preheated on a tile. After cooling to room temperature, the substrate with the glued workpiece is fixed in the collet of the machine for turning the concave surface of the lens. In some machines, the backing is not used, and the workpiece itself is fixed in the collet.
Processing begins with turning the workpiece to the specified overall diameter of the lens. The diameter value is set using the appropriate dial indicator. Then the edge zone is turned, and then the concave surface of the lens is machined according to the specified parameters.
Formation of a multi-radius surface is carried out in accordance with the calculated parameters specified in the “Tables of technological and control parameters of hard corneal contact lenses” (1981), or according to photokeratometry data. These parameters contain the values of the radii of curvature of the zones, the spindle feed rate, the total diameter of the lens and the diameter of the optical zone. By spindle feed we mean the amount of displacement of the workpiece along its axis in the direction of the axis of the rotary support.
The radius value is set by a dial indicator installed on the rotary support of the machine, and the feed amount is controlled by the spindle feed indicator. Turning begins with a surface of larger radius. Its processing is carried out in several successive passes with a cutting depth of 0.2 mm for roughing and 0.05 mm for finishing. After this, the spindle feed indicator is set to zero. Then, using the indicator of the rotary support, the next (smaller) turning radius according to the table is set, the cutter is removed from the cutting zone, and the spindle moves to specified value submissions. Turning of the remaining surfaces is carried out sequentially. Then polishing is done.
First, prepare the polishing pad for work. To do this, the cast blank of the wax polishing pad is placed on a sphero-lathe (for convex surfaces), where the working surface of the polishing pad of the required radius is machined.
Polishing is carried out on a special polishing machine (single or multi-spindle). The surface of the polishing pad is wetted with a polishing suspension. Polishing the concave surface of the lens begins with the optical zone. The peripheral zone of the lens is polished using special polishing pads moistened with a suspension. Polishing time - from 0.5 to 1 min.
After polishing, the cleanliness of the lens surface is checked using a binocular microscope or magnifying glass with a magnification of 5-10x. The radius of curvature of the optical zone is measured using a radius meter. There should be no scratches, bubbles, or gouges on the polished surface; the surface should be smooth, shiny, without rough areas. The radius of the optical zone must correspond to the specified one, within the established tolerance. If after control it turns out that the specified requirements are not met, then the processing process is adjusted.
The inspected workpiece is removed from the steel substrate by heating it on a hotplate until the adhesive wax softens. After this, it is thoroughly cleaned of wax. Then, its central thickness is measured using a thickness gauge (indicator). The measured thickness value is taken into account when processing the outer (convex) surface of the lens.
Convex surface turning and polishing
The radius of curvature of a convex surface can be calculated using the following formula:
where: r1 - radius of curvature of the convex surface, mm;
r2 - radius of curvature of the optical zone of the concave surface, mm;
D - vertex refraction of the lens, in diopters; n is the refractive index of the lens material;
t is the thickness at the center of the lens along its axis, mm.
Depending on the given refraction, central thickness values from 0.1 to 0.5 mm are recommended.
Gluing wax is applied to a preheated spherical mandrel with a radius corresponding to the radius of the optical zone of the semi-finished product and the semi-finished product is glued from the side of the treated concave surface. Centering is carried out on a special centering device with an accuracy of 0.02-0.04 mm.
After cooling, the mandrel, together with the semi-finished product centered on it, is installed on the landing cone of a sphere lathe for processing a convex surface.
The calculated radius is determined by the indicator located on the rotary caliper. Using another indicator mounted on the machine spindle, the thickness of the layer of material removed during processing is determined. Turning of a convex surface is carried out in several passes (similar to machining of a concave surface) until the specified thickness is achieved in the center of the lens.
Polishing of a convex surface is carried out with a special polishing pad moistened with a polishing suspension on a polishing machine (single or multi-spindle). Polishing time is from 2 to 5 minutes (depending on the material).
Cleanliness of the optical surface of the lens controlled using a binocular microscope or magnifying glass immediately after making the lens before removing it from the mandrel with a central hole. Optical power measured on a dioptrimeter. If during the control process it turns out that the processing results are not satisfactory, then the process is adjusted.
After polishing and control of the optics are completed, the lens is removed from the frame and cleaned of adhesive wax.
In the manufacture of the outer surface of lenses of negative refraction First, the spherical surface with the calculated radius of curvature of the optical zone is machined to a given thickness in the center, and then the lenticular zone is machined with a given edge thickness until it mates with the optical zone. The radius of curvature of the lenticular zone is calculated and depends on design features lenses. When calculating, it should be borne in mind that the thickness of the lens along the edge should not exceed 0.2 mm, and the diameter of the optical zone of the outer surface should be at least 7.5 mm.
When making the outer surface of positive refraction lenses, first grind the spherical surface with a calculated radius to a thickness at the center that exceeds the required by 0.03 mm. The size of the radius depends on the thickness of the lens at the center and along the edge. Then the lenticular zone is machined, starting from the edge of the workpiece to the calculated diameter of the optical zone of the outer surface, which is selected 0.4-0.5 mm larger than the diameter of the inner surface. The indicator sets the calculated radius of the optical zone. By turning the cutter mounting support and corresponding feed of the workpiece, the tip of the cutter is aligned with the peripheral portion of the optical zone and the optical zone of the convex surface is processed. Polishing is carried out on a polishing machine using a special polishing pad moistened with a suspension.
The production of GPZhKL is carried out according to the same scheme, but less intensive processing modes and special compositions are used for cleaning and polishing these materials.
Manufacturing of spherotoric hard corneal contact lenses
When processing spherotoric lenses, first the concave spherical surface of the lens is machined according to the method discussed above, and then, to obtain a toric surface at the periphery, it is processed with a toric tool (usually a grinder and polisher) with given radii of curvature of the surfaces in two mutually perpendicular planes (Fig. 76) . The number of prepared toric instruments depends on the required number of toric surfaces in the flattening (sliding) zone.
For turning the grinder use a special lathe designed for the manufacture of toric tools. In this case, the following rules should be adhered to:
1. Based on the difference between the radii in the main meridians, the lateral displacement of the spindle relative to the rotary support is determined. Movement is monitored using a dial indicator. For example, for a toric tool with radii 8.0/8.5 mm, this value, called the toric difference, will be equal to 0.5 mm.
2. By rotating the rotary caliper, grind the tool blank to a depth of no more than 0.05 mm for each pass until the specified radius is obtained, measured by the indicator of the rotary caliper.
Then the manufactured tool is installed in special device(“toric fork”) of a polishing machine.
The substrate with the machined workpiece is rigidly fixed to the driver of the toric fork. Then the driver is installed in the grooves of the fork so that the concave surface of the workpiece rests on the working surface of the toric tool. The pin of the upper spindle of the polishing machine secures the driver of the toric fork. By vertically moving the swinging head of the finishing machine, it is necessary to achieve such a position of the workpiece that it moves only in the central part of the toric tool. Grinding is carried out using M7 and M3 grinding powder until the specified size of the optical zone is obtained. The grinding time depends on the ratio of the lens radii and the toric difference of the tool. The resulting size of the optical zone is monitored using a measuring magnification magnification of 10x.
Polishing of the toric peripheral zone is carried out on a soft polishing pad with a special polishing paste. Polishing of the optical zone is carried out in the same way as for axisymmetric lenses.
Depending on the material used, contact lenses are divided into:
- on hard: gas-permeable and gas-tight;
- on soft: silicone hydrogel and hydrogel.
Wearing period
Lenses can be worn:
- 1 day. These products are the most hygienic and easy to use. After use, the lenses are discarded; no additional cleaning products are required.
- 2 weeks. Vision correction products have a high content of moisturizing substances and good oxygen permeability.
- 1 month. This type of lens can be left on overnight due to its good breathability. Doctors recommend wearing products in this mode up to 7 days.
- 3 months. These vision correction products have good mechanical strength. Ideal for those who are just starting to wear them.
- More than a year. Such products require careful care.
Wearing mode
This term refers to the period during which vision correction devices can be worn without removing them.
It is customary to distinguish the following modes:
- day- put on in the morning and take off at night;
- prolonged- duration of wearing up to 7 days, do not take off at night;
- flexible- continuous wearing up to 2 days;
- continuous- constant wearing up to 30 days.
All the best manufacturers
There are the following contact lens manufacturers.
Johnson & Johnson
In the distant 1886 three brothers, Robert, James and Edward Johnson, founded Johnson & Johnson (J&J) in the city New Brunswick, New Jersey. Initially, the company produced products intended to maintain personal hygiene.
Attention! Johnson & Johnson became the first to start selling first aid kits for emergency medical care.
The company is constantly growing and developing, opening new branches all over the world. IN 60s of XX century Johnson & Johnson acquires a number of pharmaceutical companies, thanks to which occupies a prominent place in the pharmaceutical market. One of the advances was Tylenol, an aspirin-free pain reliever that is available by prescription. A year later after opening, the product becomes over-the-counter and receives the status of drug of choice in pediatric practice.
Photo 1. Contact lenses 1 DAY Acuvue TrueEye, 30 lenses per package, manufacturer - Johnson & Johnson.
IN 1987 Vision Care, a division of J&J, introduces the world's first soft contact lenses for elective replacement ACUVUE. Later eight years the company presents first in the world contact lenses for daily replacement 1 DAY ACUVUE.
ACUVUE products are used:
- at myopia and farsightedness: 1 DAY ACUVUE (TruEye, MOIST), ACUVUE Oasis;
- at astigmatism: ACUVUE Oasis for Astigmatism, 1 DAY ACUVUE MOIST for Astigmatism;
- at presbyopia: 1 DAY ACUVUE MOIST Multifocal.
Also available beauty lenses: 1 DAY ACUVUE DEFINE.
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Adria
Adria contact lenses are released Korean company Interojo. The company was founded in 2000. Her motto: “Lenses for the young.” The company is developing, receiving certificates for the manufacture of contact lenses from the latest materials.
Adria produces the following lines of colored lenses:
Lenses for vision correction are also available:
- daily;
- monthly;
- quarterly.
Reference! Adria products are not only quality and comfort, but also attractive design, a feeling of youth, the opportunity to surprise with new images.
Alcon/CIBA Vision
Alcon is a fairly young company created in 1945 in Fort Worth, Texas.
The founders of the company were Robert Alexander and William Conner. The name of the company included the first syllables of their surnames - Alkon. After 2 years Alexander and Conner register the Alcon Laboratories company, specializing in the production of pharmaceuticals.
In 1950 Alcon presents drugs for the treatment of uncomplicated infectious eye diseases, as well as to eliminate itching and redness. This company was the first to patent dosing device for eye drops ,DROP-TAINER, which is still in use today.
In the 80s of the last century company founded Research center named after William Conner, helping Alcon significantly increase its research into the treatment and diagnosis of eye pathologies. In the future, the company is engaged in the production of equipment for ophthalmic surgery.
Photo 2. Daily contact lenses Dailies Aqua Comfort Plus, manufacturer - Alcon.
The company was the first to develop intraocular lens (IOL), used to treat cataracts. To this day, IOLs remain the most commonly implanted lenses in the world.
In 2011 Alcon and CIBA VISION are merging, allowing these companies to join forces. DAILIES TOTAL1 contact lenses are being released.
The company produces the following vision correction products:
- one-day: Dailes Total 1 series, Dailes Total Aquacomfort Plus, Dailes Total Aquacomfort Plus Astigmatism;
- planned replacement: Air Optix series (multifocal, for astigmatism, for round-the-clock wear, color);
- colored: Freshlook series.
Bausch+Lomb
Bausch + Lomb - one of the oldest companies in the USA, which manufactures optics. Was created John Jacob Bausch, a German emigrant, and his friend Henry Lombom in Rochester, New York. In the first years, the company was engaged in the production of rubber frames for glasses, and later - microscopes, binoculars, camera shutters, and sights.
At the beginning of the last century Bausch + Lomb were the first to produce high quality optics.
The company is also the developer of the now famous Ray-Ban sunglasses.
The same company produced lenses for spacecraft cameras, with the help of which the first photographs of the Moon were created.
By the middle of the 20th century Bausch + Lomb has taken a step forward: it has acquired the rights to produce and distribute soft hydrogel contact lenses. By the age of 80 the company finally focused on the production of vision correction products, having sold out all its other production facilities.
Currently, Bausch + Lomb's work is represented in the following areas:
- VisionCare— vision correction products (several types) and solutions.
- Pharmaceutical— block of pharmaceutical ophthalmic products.
- Surgical— surgical equipment and instruments.
The company does not stand still and is constantly developing: new pharmaceuticals, equipment, and soft contact lenses are being developed.
Bausch + Lomb produces the following vision correction products:
- one-day: Biotrue ONEday, SofLens Daily Disposable ;
- planned replacement: Ultra, PureVision (2 HD, Mulifocal, Toric, for Astigmatism), Soflens (59, Toric), Optima FW;
- colored: Soflens Natural Colors.
Ophthalmix
The manufacturer is medical group Oftaderm, based in 1996. She began her work as an official representative of global manufacturers of contact lenses and care products. On present moment the company has its own brand - Ophthalmix.
Oftaderm strives to improve the quality of its products in order to best meet customer needs.
The following lenses are known under the Ophthalmix brand:
- For vision correction: Profi, 55 UV, OneDay, Clear;
- color, one-, two- and three-tone: Gold, Butterfly One Month, Crazy;
- tint: Colors Soft.
Maxima Optics
Maxima Optics is an international manufacturer of vision correction products and related products. Homeland is United Kingdom where the company was founded in 1999. The main goal of the manufacturer is to develop high-quality ophthalmic products from modern materials that are accessible to everyone. Maxima Optics works tirelessly to improve products, introduce new technologies, and conduct tests.
Maxima Optics includes:
- lenses daily replacements: Maxima 1-Day Comfort (Premium);
- correction means monthly replacements: Maxima 55 Comfort Plus, Si Hy Plus;
- lenses quarterly replacements: Maxima 38 FW (55 FW).
CooperVision
The year the company was founded is considered 1980 . Within a decade Since its founding, CooperVision has acquired a number of companies involved in the production of vision correction products. This made it possible to significantly expand the range of products, as well as increase the volume of its production.
The company is currently conducting active research and development. In 2006 CooperVision became the third largest company in the world for the production of soft contact lenses.
CooperVision produces the following series of lenses:
- MyDay— one-day.
- Clarity- silicone hydrolic on 1 day.
- Biofinity- products with a service life 1 month.
- Avaira—for 1 month with UV filter.
- Proclear— a special series for those who experience dryness when wearing.
- Biomedics- products with an optimal ratio prices and quality.
Useful video
Watch the video about the rules for choosing contact lenses.
Conclusion: popular brands
Currently the most popular company is Johnson & Johnson- brand lenses Acuvue most often prescribed by ophthalmologists. Next comes the brand Alcon, which produces various eye drops and lens solutions. In third place American brand is located Bausch+Lomb. We especially love products from the Soflens, Optima, and PureVision series.
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 with us their thoughts on this topical topic.
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 unified development program, no support 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 pricing 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 scheduled 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 production facilities here and completely drive 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 ongoing in all regions 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 production. Profitability is declining, and at the moment it is very low - although the prices for the cost of materials do not change, the costs of rent, electricity, wages and so on are rising, and therefore the cost is increasing.
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 stock. 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: Yes, of course. 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 on large industries, 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, sales are also growing at the same time Russian companies. 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 controls. 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 (SMA) “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 the NPO Medoborudovanie, who had great 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
