Manufacturing of contact lenses: technology, methods. Selection of hard contact lenses

The production and sale of contact lenses is a profitable business. It is not surprising that competition in this market is very high, especially among Western companies. In other countries, as in Russia, the main market positions contact correction occupied by four main companies.

Slightly less than half of the market belongs to Johnson & Johnson. The shares of CIBA Vision Cooper Vision products account for 18% of the total volume. Bausch&Lomb takes fourth place with 12%. All other companies, including domestic manufacturers, account for the remaining 4%. Among the most popular means Contact lens care experts call: Opti - Free RepleniSH (about 23%), Renu MultiPlus (22%) and Free Express (17%). The remaining 38% are products from other brands.

As a result of the study foreign markets contact vision correction products, conducted by the independent research and consulting company Eurolens Research, the following portrait of the average lens user emerges. The average age of the consumer is 30 years. Moreover, in countries with a developed market for the consumption of contact correction products average age turns out to be higher (in Australia – 34.7, in the UK – 35.1, in Canada – 32.4).

In countries where this market is in its infancy and development, this figure is somewhat lower. Thus, in Russia the average age of an active contact lens user is 26.4 years. This is explained by the fact that young people, as a rule, care more about convenience and their appearance, they tend to experiment and try everything new, unlike older people who are more conservative.

In addition, according to statistics, women are much more likely than men to wear contact lenses. And if in other countries percentage is 67% and 37%, respectively, then in Russia more than 83% of the fair sex refuse glasses in favor of lenses. As a result, in our country the demand for colored contact lenses is especially high (about 14% of the total volume of soft contact lenses sold). Until recently, hydrogel contact lenses occupied the first place in sales. However, every year the popularity of daily contact lenses is increasing, which, however, still lags behind in sales volumes.

In developed countries, the situation is exactly the opposite: most Europeans prefer to use more harmless and comfortable contact lenses for daily wear, and lenses with a replacement period of 3-6 months have not been sold abroad for a long time. Unfortunately, Russian consumers prefer to save on their health by choosing lenses that can be changed less often.

Also, soft toric lenses are not in great demand in the domestic market. Experts are confident that the future belongs to silicone hydrogel contact lenses, which have a high moisture content and allow more oxygen to pass through to the cornea than common hydrogel lenses.

The production of contact lenses is a high-tech process that requires special equipment, qualified workers, and strict quality control. But in large areas no need: production and warehouse itself finished products can be located in the same room. There are several ways to make the most common soft contact lenses: centrifugal forming, turning, casting and a combined method.

When producing contact lenses using the centrifugal molding method, special molds are used in which the starting material, a liquid polymer, is placed. Under influence ultraviolet radiation And high temperature the polymer hardens. During this process, the mold is constantly rotating: its speed of movement, ambient temperature, and the amount of polymer directly affect the final product. After the polymer has hardened, the lens is removed from the mold and undergoes a hydration process.

This type of production is less expensive compared to others, and at the same time allows you to produce quality lenses with good stability and reproducibility of specified parameters. However, this method is not suitable for the production of lenses with a toric surface.

The production of contact lenses using the turning method is more complex and labor-intensive, therefore the cost of a product produced in this way will be higher. As a rule, lenses are produced by turning using individual orders or in small batches. The lens is literally machined from dense blanks of polymerized material.

Production consists of several stages. First, the workpiece is processed on a lathe, during which a lens with a thickness of 0.1 mm is obtained. Then it is polished, hydrated (placed in a special solution, after removal from which it becomes soft), chemical disinfection and tinted. Once the lens passes quality control, it is sterilized, packaged and labeled. Because each lens is turned almost by hand (albeit under computer control), it is thicker than lenses made by other methods and, as a result, has less oxygen permeability. Most Russian companies produce traditional lenses this way.

Large Western companies that produce lenses for routine replacement and daily wear in large volumes use a casting method that can significantly reduce costs during large-scale production. In this case, a base is first created in the form of a metal matrix with predetermined parameters. It is needed for making plastic replica molds.

The liquid polymer is then poured into bottom part form and is closed by its upper component. The mold is irradiated with ultraviolet light, under the influence of which the polymer hardens. After which the used form is deleted. The remaining steps are similar to those used in other production methods: hydration, chemical disinfection, toning, quality control, sterilization, packaging and labeling. The resulting lenses are very thin - their thickness is about 0.03 - 0.05 mm.

The last, combined method, as the name implies, includes all methods of making lenses: first, using centrifugal formation, a lens with a smooth surface is produced, which then undergoes additional processing by turning.

The main domestic manufacturers of contact vision correction products are Optikon (Moscow), Optimedservice (Ufa), Concor (Vologda), Octopus (Samara). They work on modern computerized production lines and use imported material, produce lenses and produce lens care products (although more often solutions for lens care are made to order abroad under their own brand).

Their main advantages: low cost products, strict quality control, wide choose large diopter lenses (from -26 to +26). Lenses of such refractions are not available in the range of Western companies. However, domestic products cannot yet withstand competition with foreign brands. Most of it consists regular lenses, while all over the world they have long been replaced by daily lenses and scheduled replacement lenses.

The profitability of enterprises that produce lenses using the turning method is 10-12%. The profitability of production using injection molding technology reaches 100%. However, the costs of equipment in the latter case are many times higher, and they can only be recouped through large sales volumes. Meanwhile, sales volumes of the largest Russian manufacturers, which have their own representative offices in various Russian regions, produce no more than 300 thousand lenses per year. To promote sales, lens manufacturers actively cooperate with specialists in contact vision correction, offering them training, bonus programs, preferential conditions, etc.

Experts recommend Russian companies who run the business of producing contact lenses, pay attention to the niche of special lenses - toric and bifocals, which are more expensive than regular ones. The demand for them, although not high, is still there, but there are practically no offers.

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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 additional funds They do not require cleaning.
2 weeks. Vision correction products have increased content moisturizing agents, 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 highlight following modes:

day- put on in the morning and take off at night;
prolonged- duration of wearing up to 7 days, are not removed 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. One 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.

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 production 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 eye drop dispenser,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. Started her work as official representative global manufacturers of contact lenses and care products. On currently 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 Great Britain where the company was founded in 1999. The main goal of the manufacturer is to develop high-quality ophthalmic products from modern materials, which are available 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.

Currently, the company is actively Scientific 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- lenses trademark Acuvue most often prescribed by ophthalmologists. Next comes the brand Alcon, which produces various eye drops and lens solutions. On the third place American brand is located Bausch+Lomb. We especially love products from the Soflens, Optima, and PureVision series.

Contact lenses were invented over a hundred years ago. For a long time, only hard lenses were produced, but in 1960 soft contact lenses were invented and received wide use. Unlike hard lenses, they are comfortable to wear and do not take a long time to get used to. Today, about 90% of users prefer soft lenses made of elastic, gas-permeable materials. When properly selected, they provide the owner with comfort, safety and ideal vision correction. Modern hard lenses are also gas-permeable, but due to difficulties in getting used to them, they are usually used only in isolated, particularly difficult cases.

Lens making methods

The production of modern contact lenses is based on several technologies:
- turning (turning);
- casting;
- centrifugal molding;
- combined methods that combine elements of the above methods, for example, the reverse reverse process.

Turning

The turning method is used for the manufacture of both soft and hard ones. Their production is carried out on the same equipment, but has some differences. Disc-shaped workpieces are processed on special lathes; this process is almost completely automated. A computer program monitors compliance with all parameters.

At the first stage, a diamond-tipped cutter forms the inner curve of the lens, then polishes the surface to make it absolutely smooth. Next, the outer surface that will be in contact with the eyelid is processed, and the workpiece is given the required diameter. The outer surface and edges of the lens are also carefully polished. At the end of this stage, its thickness and other parameters are measured using a very precise instrument.

The difference between the production of soft lenses is that after the turning stage they are subjected to hydration - immersed in saline solution with optimal pH factor. Hydrogel and silicone hydrogel, from which soft lenses are made, absorb moisture well and swell, increasing to the right size. During hydration, the hard workpiece acquires the missing softness and elasticity. At the end, the finished product is tested for compliance with optical and geometric parameters. Before sale, lenses are cleaned, packaged and labeled.

Casting

Casting begins with the manufacture of a matrix with specified parameters that correspond to the characteristics of the future lens. Form copies are made from the matrix from plastic, which can be either disposable or reusable. The lower half is filled with liquid polymer and covered top part, forming an internal space shaped like a lens. The workpiece is irradiated with ultraviolet light, under the influence of which the polymer hardens. The lens is then hydrated, measured, cleaned and packaged.

Centrifugal molding

Centrifugal molding technology was developed by the Czech inventor of soft lenses, Otto Wichterle. A special mold with a concave bottom and cylindrical walls is filled required quantity monomer. During its rotation on special equipment, the composition spreads over inner surface and hardens. The shape and thickness of the resulting lens depend on the amount of polymerization mixture and the speed of rotation of the mold.

Reverse reverse process

The reverse reverse process successfully combines the two technologies described above. First, the convex side of the lens is obtained by centrifugal molding, then processed by turning inner part. The resulting lens acquires the advantages of each method - smoothness outer surface and edges are combined with excellent functional qualities obtained by turning.

ZhGKL are manufactured strictly according to individual order, taking into account all the patient’s parameters, as they require a more accurate match of the inner surface of the lens to the surface of the cornea.

Wholesale price from 2500 rub.

ALWAYS MADE TO CUSTOM ORDER

no prepayment - for regular customers

30% prepayment - for new clients (Moscow, Kaluga, Obninsk + all other regions of Russia)

full prepayment - for residents of other countries

REGULAR PRODUCTION (GROUP): lenses are sent for production upon placing an order (from 30 lenses), without additional extra charge.

Order formation usually takes from 3 weeks to 2 months (check the stage with the operator). The lenses are then manufactured within approximately 2-3 weeks + delivery from the manufacturer takes 3-10 days. That is, the order arrives approximately 1-3 months after placement.

URGENT PRODUCTION (INDIVIDUALIZED) : Your order is sent for production individually, right on the day of registration, without any expectations, and also arrives individually, without waiting for other orders. That is, the order arrives approximately 2-4 weeks after placing.

When ordering by large wholesale for free

When ordering by average wholesale + 600 rubles

When ordering in small wholesale + 999 rubles

When ordering retail + 1500 RUR

Material: F2 produced by CONTAMAC

Manufacturing method: turning

Packing: bottle with 1 piece

Rigid lenses for astigmatism correction:

-inner radius from 7.9 to 9.0, step 0.05

-toricity T3-T12

-eccentricity from 0.2 to 1.2, step 0.1

Rigid lenses for keratoconus correction:

-internal radius from 4.8 to 7.2, step 0.05

- internal optical zone diameter from 5.5 to 6.5, step 0.1

-eccentricity from 1.0 to 2.8, step 0.2

To place an order for rigid gas-permeable lenses, you need to indicate in the "Additional Information" the diameter of the lens (mm), the internal diameter of the optical zone (mm), the number of internal radii (chamfers), including the optical zone, the size of each radius (mm), the width of each radius (mm), feed amount for each radius (mm), lens refraction (dopter).

For example, the lens diameter is 9.6 mm, the internal diameter of the optical zone is 7.3 mm, the number of internal radii is 4, refraction is -6.5 diopters,

size of each radius, width of each radius, feed
8,69 0,45 0,000
8,11 0,35 0,680
7,82 0,35 1,016
7,60 7,30 1,260

For keratoconus, you need to indicate in the "Additional Information" the diameter of the lens (mm), the internal diameter of the optical zone (mm), the number of internal radii (chamfers), including the optical zone, the size of each radius (mm), the width of each radius (mm), the size feed for each radius (mm), lens refraction (dopter).

For example, lens diameter 9.5 mm, internal optical zone diameter 6.0 mm, number of internal radii 8, refraction -10.5 diopters,

size of each radius, width of each radius, feed

9,50 0,156 0,000

8,50 0,241 1,155

7,50 0,244 2,337

7,20 0,282 2,695

7,00 0,231 2,930

6,80 0,248 3,162

6,30 0,240 3,738

If necessary, a copy of the certificate is issued along with the order.

These lenses can be purchased at wholesale prices!

3250 rubles for 1 lens when ordering Concor products for an amount over 5,000 rubles at small wholesale prices (small wholesale)

2900 rubles for 1 lens when ordering Concor products for an amount over 10,000 rubles at average wholesale prices (average wholesale)

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 hard corneal PMMA contact lenses use cylindrical blanks with a diameter of 12.0 to 12.5 mm and a thickness of 4.0 to 5.0 mm.

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 cylinder is lubricated Vaseline oil. 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.

Technological process manufacturing hard corneal lenses using the turning method includes the following steps:

Calculation of technological processing parameters (radii, thickness, 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 of a 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 by turning, 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 mounted 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 is measured using a diopter meter. 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 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 are used and special compounds 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 a special device (“toric fork”) of the 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.