At school physics lessons, we remember that the rays of light propagate in a straight line. Any object in their path partially absorbs light, partially reflects at the same angle at which it falls. The only exception is when light passes through a transparent object. At the border of two transparent media with different densities (for example, air and water or glass), light rays are refracted to a greater or lesser extent, and amazing optical effects arise, depending on the physical characteristics of the object through which the light passes.
This property of light allows you to control the course of rays by changing their direction or converting a diverging beam of rays into a converging one, and vice versa. In practice, this can be achieved using specially treated devices made of an optically transparent homogeneous material, which are called lenses (ref. Lens "lentils"). Looking at an object through lenses with different physical and chemical characteristics, we will see it straight or inverted, enlarged or reduced, clear or distorted.
The simplest lens is a carefully ground and polished piece of highly transparent material (glass, plastic, mineral), limited by two refractive surfaces, two spherical or flat and spherical (although there are lenses with more complex aspherical surfaces). Lenses whose middle is thicker than the edges are called converging (positive), scattering (negative) lenses are called lenses whose edges are thicker than the middle. A positive lens has the ability to collect rays incident on it at one point located on the other side of it, in focus. A negative lens, on the other hand, deflects rays passing through it towards the edges.
The simplest rock crystal lens.
Although the scope of use of lenses in science and technology is very large, their main functions are reduced to several main ones. This is the accumulation of thermal energy of light rays, visual approach and magnification of small or distant objects, as well as vision correction, because the lens of the eye is by its nature a lens with variable curvature of surfaces. People began to use some properties of lenses earlier, others later, nevertheless, these optical devices have been known to them since ancient times.
There are different opinions about when people learned how to get fire using sunlight and polished pieces of transparent stone or glass with a convex surface. We can say for sure that this method was known in Ancient Greece in the middle of the 1st millennium BC. e., as described in the play by Aristophanes "Clouds". However, the lenses of rock crystal, quartz, precious and semiprecious stones found during excavations are much older. One of the most ancient lenses, the so-called god with glasses, was discovered during the excavations of Uruk, an ancient city-state in Mesopotamia. The age of this lens is about 6 thousand years, and the purpose remains a mystery.
In Egypt during the IV-XIII dynasties (III-II millennia BC), crystal lenses were used for ... models of eyes at the statues. Optometric studies have shown that the models are very close to the real shape and optical qualities of the eye, and sometimes even show visual impairments such as astigmatism.
Alabaster "idols with eyes." The settlement of Tel Brak, Syria. IV millennium BC NS.
Unfortunately, over time, the secret of making such lenses was lost, the false eyes of statues began to be made of stone or faience. The technique of "glass eyes", albeit with less perfection, was also owned by the ancient Greeks. Lenses were provided, for example, bronze statues of the 5th century. BC e., found in the sea off the coast of Calabria. But before the "official" discovery of the optical properties of the eye, there were still many centuries!
During excavations on the territory of Mesopotamia, Greece and Etruria, a considerable number of crystal lenses were discovered, dating back to about the end of the 1st millennium BC. NS. Research into their finishes revealed that the lenses were used for both visual magnification and decoration. In fact, these were real small focal length magnifiers that increased the angle of view. In addition, miniature gems were found in Greece, connected by frames with convex lenses; these gems could not have been made without the optical magnification of the working field. All this indicates that magnifiers began to be used long before the magnifying effect of lenses was recorded in scientific sources.
When exactly lenses began to be used for vision correction, it has not yet been established. There is an opinion, true, not supported by anything, that it was for this purpose that the lenses discovered during excavations of ancient Troy were used. In the writings of the Roman historian of the 1st century. Pliny the Elder mentions that the emperor Nero, who suffered from myopia, watched gladiatorial battles through a concave lens, carved from emerald, it was a kind of a prototype of glasses. Some historians, based on ancient engravings, believe that glasses were invented in China in the 7th-9th centuries, but it is not known for sure whether they were optical or sunscreen.
The study of the eye as an optical system was first seriously undertaken by an Arab scientist of the 9th century. Abu Ali al-Hasan, known in Europe as Al-Khazen. In his fundamental work "The Book of Optics", he relied on the research of a Roman physician of the 2nd century. Galena. Al-Hasan described in detail how an image of an object is created on the retina of the eye with the help of a lens. However, the essence of myopia, farsightedness and other visual defects, in which the focus of the lens is displaced relative to the retina, was finally clarified only in the 19th century, and before that glasses were selected practically at random until the desired effect was achieved.
Mysterious optics
On the Swedish island of Gotland, in a hoard buried about a thousand years ago by the Vikings, lenses of a complex aspherical shape made of rock crystal were found. This lens shape was theoretically calculated only in the 17th century. René Descartes. In his work, he indicated that these lenses would give excellent images, but for a long time no optician could make them. It remains a mystery who and for what purpose could polish the lenses from the Viking hoard.
Glasses seller. An engraving after a painting by Giovanni Stradano. XVI century
It is believed that glasses were invented in Italy at the end of the 13th century, their invention is attributed to the monk Alessandro Spina or another monk Salvino D "Armata. The first documentary evidence of the existence of glasses dates back to 1289, and their first image was found in the Church of Treviso on fresco painted by the monk Tommaso da Modena in 1352. Until the 16th century, glasses were used only for hyperopia, then glasses with concave glasses for myopic people appeared. lenses that at the top are designed for distance, and at the bottom for near work.
J. B. Chardin. Self-portrait with glasses. 1775 g.
Jan van Eyck. Madonna and Child with Canon Joris van der Pale. Fragment. 1436 g.
Photochromic lenses ("chameleons") were created in 1964 by specialists from Corning. These were glass lenses, the photochromic properties of which were imparted by the salts of silver and copper. Polymer lenses with photochromic properties appeared in the early 1980s, but due to significant drawbacks, the low rate of darkening and brightening, as well as extraneous color tints, did not become widespread. In 1990, the Transition optical company released more advanced plastic photochromic lenses, which gained immense popularity.
Contact lenses are considered a relatively young invention, but Leonardo da Vinci worked on their design. Many scientists thought about how to put the lens directly on the eyeball, but it was not until 1888 that the Swiss ophthalmologist Adolph Fick described the device of a contact lens and began experiments. The mass production of contact lenses was started in Germany by the renowned optical company Carl Zeiss. The first samples were completely glass, rather large and heavy. In 1937, polymethyl methacrylate lenses appeared. In 1960, the Czechoslovak scientists Otto Wichterle and Dragoslav Lim synthesized a new polymer material HEMA, developed a method of rotational polymerization and produced soft contact lenses. At the same time, hydrogel lenses were developed in the United States.
With regard to the magnification of single lenses, it soon became clear that it was limited, as increasing the convexity of the lens would distort the image. But if you place two lenses (eyepiece and objective) in succession between the eye and the object, the magnification will become much higher. With the help of the lens, an actual image of the observed object is created at the focal point, which is then enlarged with an eyepiece acting as a magnifying glass. The invention of the microscope (from the Greek mikros "small" and skopeo "look") is associated with the names of the Dutch people John Lippersgey and the father and son Jansen (late 16th century). In 1624 Galileo Galilei created his own compound microscope. The first microscopes were able to magnify up to 500 times, while modern optical microscopes can achieve 2,000 times magnification.
Simultaneously with the first microscopes, telescopes (or telescopes) appeared (their invention is attributed to the Dutch Zachary Jansen and Jacob Mettius, although Leonardo da Vinci made the first attempts to look at the stars with the help of lenses). Galileo was the first to direct the telescope into the sky, turning it into a telescope (from the Greek tele "far"). The principle of operation of an optical telescope is the same as that of a microscope, the only difference is that the lens of a microscope gives an image of a close small body, and a distant large telescope. However, since the end of the 17th century, telescopes have used a concave mirror as an objective.
Otto Wichterle in the laboratory.
Among other things, lenses are used in photography, film, television and video filming, as well as for the projection of finished images. The lens of a camera and similar equipment is an optical system of several lenses, sometimes in combination with mirrors, which is designed to project an image onto a flat surface. The curvature of the objective lens is calculated so that possible aberrations (distortions) are mutually compensated. Joseph Niepce, who created one of the first cameras in 1816, borrowed a lens for him from a microscope.
Since the second half of the last century, electronics with a higher resolution have been used to observe various micro and macro objects along with optical systems. However, lenses are still so widely used that listing all of their applications would be difficult.
The camera of Joseph Niepce.
Telescope-refractor at the Lik Observatory. California, USA.
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19:57
History of contact vision correction.
The idea of creating lenses that would be in direct contact with the eyes and improve vision goes back five centuries.
In 1508 Leonardo da Vinci described a ball filled with water, which was able to change the optical properties of the patient's eyes (however, such a lens could not be put on the eye, you had to immerse your face in it).
There is even a drawing "An eye with a bath filled with water on it."
Three hundred years later Thomas Jung described an experiment with a short tube filled with water and a biconvex lens that, when placed on the eye, improved vision. Towards the end of the 18th century, a German ophthalmologist Adolph Fick created the first glass contact lens to match the shape of the eye. After experimenting on animals, he ventured to test it on the human eye. In parallel with the works Fick, French ophthalmologist Evgeny Kalt used lenses of a similar design in patients with keratoconus.
In 1887 another scientist Friedrich Müller placed a blown glass lens over the eye of a patient whose eyelids were removed. The lens protected the eye and prevented moisture loss, the patient has worn this lens for over 20 years. In the early 1920s, a mass production of glass contact lenses was launched by the optical enterprise Carl Zeiss Jena (Germany), and special trial sets were made for their selection.
Further development of contact correction was aimed at improving the portability of contact lenses and the search for new materials for their manufacture.
In 1937, an American optometrist William Finebloom began to produce lenses in which the scleral part was made of plastic, and the corneal (optical) part was made of glass. And in 1938 the Hungarian ophthalmologist Istvan Djerfi was the first in Europe to manufacture scleral lenses entirely of plastics (PMMA). However, practice has shown that neither new materials (PMMA) nor new production methods (the turning method proposed by T. Obrig in 1938) had a significant impact on the portability of such lenses. They were still too heavy, motionless, and sensitive.
And by the end of the 50s, the Czech scientist Otto Wichterle developed a polymer hydrogel, which became the basis for the materials used in the manufacture of modern soft contact lenses today. Hydroxyethyl methacrylate polymer (HEMA) is a material that has the ability to retain water. At the same time, it is soft, flexible and oxygen-permeable.
Since the advent of soft contact lenses, many improvements have been made in their design, manufacturing methods, which made them significantly thinner, improved patient tolerance and optical properties. Most soft contact lenses are made from HEMA polymer today.
However, as it turned out, soft contact lenses also have their drawbacks: it is the need for special, sometimes difficult, care; and most importantly - limited oxygen transmission. Therefore, scientific work in contact correction was actively continued.
In 1988. the idea of a planned replacement of contact lenses was born, which implies a much easier care of lenses and ensures high safety during their use. We now have lenses with a monthly, 2 week, and even 1 day replacement mode.
In 1999. a fundamentally new material for soft contact lenses has appeared - silicone hydrogel, characterized by an unprecedentedly high oxygen permeability. We can say that in such a lens the eye receives as much oxygen as without it. In 2003-2004, second-generation silicone hydrogels with improved properties appeared. Today many companies already produce "breathing" lenses from these materials, including lenses with non-standard parameters, for the correction of astigmatism and keratoconus.
Contact vision correction does not stand still, every day brings something new - new lens designs are created, materials and production methods are improved.
In the future - the creation of contact lenses with an antibacterial coating, which will ensure complete safety when wearing contact lenses.
American scientists (USA, Washington) are developing special contact lenses with an integrated microcircuit that will allow contact lenses to enlarge the image and display various kinds of data on the lens, such as body temperature or blood pressure.
What are contact lenses?
Contact lens (hard or soft) - this is a small "cup" with optical properties and worn directly over the eye. Contact lenses are made from an oxygen-permeable material. The rear surface of the lens follows the shape of the cornea of the eye and is responsible for the fit, while the front surface corrects the irregular optical system of the eye, which allows for clear vision.
What are contact lenses for?
Soft and hard contact lenses are used to correct visual impairments - myopia, hyperopia, astigmatism. When properly selected and used, contact lenses have a number of advantages over spectacles.
First, contact lenses provide higher visual acuity than glasses, without distortion or aberration. In comparison with glasses, contact lenses greatly expand the field of view.
Secondly, the range of correction with contact lenses is much wider than that of spectacle or surgical lenses, from +20.0 to -20.0 diopters.
Thirdly, contact lenses do not restrict freedom, they allow you to lead an active lifestyle, go in for sports.
Indications for wearing contact lenses.
1. mild to high myopia and hyperopia. Lenses allow you to achieve higher indicators of visual acuity and quality than glasses.
2. Intolerance to spectacle vision correction.
3. big difference in visual acuity of the right and left eyes (more than 2.5 diopters). In this situation, the glasses do not allow for maximum correction;
4 aphakia (absence of the lens) after removal of cataracts, trauma or congenital defect of the eye;
In addition, contact lenses can be used to change the color of the eyes for cosmetic purposes.
Contact lens classification.
Based on materials:
1. Rigid contact lenses
Gas permeable
Gas tight
2. Soft contact lenses
Hydrogel
Silicone hydrogel
By production method:
1. Turning
2 .. Centrifugal molding
3. Combined method
By wearing mode:
1. Day wear lenses(Dw daily wear) - these lenses can be worn 8-12 hours a day, you cannot sleep in these lenses
2. Flexible wearing lenses (FW flexible wear) - sometimes they allow the possibility of sleeping in lenses (be sure to consult with your doctor - there may be individual restrictions depending on the condition of your eyes).
3. Extended wear lenses (EW extended wear) - can be worn up to 7 days continuously (6 nights, 7 days). If you choose this wearing mode, during the adaptation period (1 month) you will need constant medical supervision.
4. Continuous wear lenses (CW continuous wear) - it is allowed not to take off for up to 30 days in a row; There are significant restrictions on the certification of these lenses, in Russia there are only 2 contact lenses available for continuous wear.
By replacement time:
1.Conventional contact lenses- made by turning, produced in glass bottles, service life from 6 months to 1 year.
2.Routine replacement contact lenses
- lenses of planned replacement - produced in blisters, usually replaced once every 3 months.
- lenses of frequent planned replacement - replacement of lenses once a month or more often, available in blisters.
3. Disposable contact lenses- such lenses are put on in the morning, removed in the evening and thrown away, produced in blisters.
Replacement times for lenses will vary depending on the material they are made of, the lens design, and the manufacturing method.
It is strictly forbidden to overhaul lenses longer than the period prescribed by the manufacturer, since this increases the risk of complications many times !!!
How to choose contact lenses.
SELECTION OF CONTACT LENSES for vision correction - a medical procedure that only an ophthalmologist has the right to carry out.
Contact lenses cannot simply be purchased based on a previous eyeglass prescription. In order for the lens to perfectly match the surface of the eye, it is necessary to know certain parameters of the cornea (diameter and radius of curvature). To measure these parameters, special ophthalmic devices are used (that's why, even colored lenses without optical power should also be selected by a doctor).
After calculating the optical power and choosing the lens parameters, the doctor will assess the quality of vision, fit, centering and mobility of the lens on the eye. Then she will teach you how to remove and put on lenses on your own, discuss lens care issues, as well as the time of dispensary examinations.
Incorrectly fitted lenses can cause severe corneal complications, up to and including severe vision loss.
How to put on and take off your contact lenses.
How do I wear contact lenses?
1. Sit in front of the mirror, slightly tilting your head forward and looking into the mirror as if into the distance (you don’t need to follow your finger).
2. Always start installing contact lenses with the same eye, for example with the right eye (this is especially important for those who have different vision in the right and left eyes).
3. Remove the lens from the blister (if the package is damaged, the lens cannot be used). If the lens sticks to the package, it remains sterile and can be used.
4. Carefully inspect the lens and make sure it is not damaged (no tears, cracks, foreign bodies on the surface). If in doubt, the lens seems to be damaged - do not use it, take the next one from the package.
5. Make sure the lens is turned upside down. Place the lens on the pad of your index finger and view it in profile:
Correctly positioned lens resembles a cup in shape - its edges are directed upwards.
If the lens is turned inside out, it looks more like a plate - its edges are directed to the sides.
Two ways to put on contact lenses.
Putting on the lens with one hand:
1. Place the lens on the pad of your index finger.
2. Pull back the lower eyelid with the middle finger of the same hand.
3. Lift your eyes up and carefully place the lens on the white part of the eye (sclera) below the pupil
4. Remove your index finger from the lens.
5. Lower your eyes to accurately center the lens.
6. Gently lower the retracted lower eyelid.
7. Close your eyes briefly for a better fit of the lens.
We put on the lens with both hands:
1. Place the lens on the pad of your right index finger.
2. Pull down the lower eyelid with the middle finger of your right hand.
3. Pull the upper eyelid towards the eyebrow with the middle finger of the left hand and fix it.
4. Lift your eyes up and carefully place the lens on the white part of the eye (sclera) below the pupil
5. Remove your index finger from the lens.
6. Keeping the eyelids in the indicated position, lower the eyes downward to accurately center the contact lens.
7. Gently lower the retracted eyelids.
8. Repeat the manipulation when putting the lens on the other eye.
How to remove contact lenses?
1. Pull down the lower eyelid with your middle finger.
2. Look upward without changing the position of your head.
3. Place the tip of your index finger on the contact lens and slide it down onto the sclera using a sliding motion.
4. Gently pinch the lens between your thumb and forefinger and remove it from your eye.
5. Place the contact lens in the container with the solution.
6. Do the same with the contact lens on the other eye.
If after you have removed the lens - it stuck together, do not try to straighten it by stretching the edges, as you may tear it. Place the lens in a container of solution, it will most likely straighten out on its own. If this does not happen, gently spoil it between your thumb and forefinger, after moistening it well with a solution.
How do I care for my contact lenses?
Daily care.
Step 1. Mechanical cleaning(provides removal of protein and fat deposits from the lens surface)
1. Fill the slots of the lens storage container with multifunctional solution 2/3 full.
2. Remove the lens from your right eye and place it on the open palm of your left hand
3. Apply 3-4 drops of multifunctional solution to the lens
4. Using the index finger of your right hand, gently rub the lens against the palm of your hand in horizontal or vertical movements for 20 seconds. (Do not rub the lens in a circular motion, this may damage the lens).
Be sure to follow this procedure as it removes 90% of all surface contamination.
Step 2. After mechanical cleaning, rinse the contact lens with a multifunctional solution, holding it in your open palm.
Step 3. Disinfection of lenses(ensures the destruction of microorganisms)
1. Place the lens in the appropriate compartment of the container
2. Repeat all manipulations with the other lens.
3. Make sure the fresh solution completely covers the lenses.
4. Close the container lids carefully.
5. Leave the lenses for at least 4 hours for complete disinfection (disinfection time depends on the solution you use, check it according to the instructions supplied with the solution)
At the end of the disinfection time, contact lenses can be worn without additional rinsing.
After putting on the lenses, drain the solution and rinse the container with a clean solution.
In 1508, Leonardo da Vinche created a drawing depicting a glass sphere filled with water, with which a person with poor eyesight would be able to see better.
Eye-shaped glass
130 years after this significant event, the French mathematician Rene Descartes proposed using a glass cylinder with water for the same purposes, attaching a magnifying glass to its end.
Two hundred years later, in 1827, the English physicist and astronomer John Herschel first described a glass lens that repeated the shape of an eye. And already in 1888, the German glassblower Friedrich Müller made the first glass sphere for his friend, who had lost an eyelid. This glass completely covered the eye, protecting it from the harmful effects of the environment, and improving visual acuity. After the first successful experience, the glassblower took up the production of lenses for other clients. The lenses, which he blown out, completely repeated the shape of the eye and were made in a two-color version. The white glass was adjacent to the white of the eye, and the transparent glass was adjacent to the iris and pupil.
At the beginning of the twentieth century, the German company Carl Zeiss began mass production of glass contact lenses. At that time, glass lenses were the crown of ophthalmology. However, they had significant ones. The size of the glass envelope prevented the natural flow of oxygen to the cornea and over time caused severe problems in patients due to hypoxia.
Plastic in the eye
In 1939, the Hungarian doctor Istvan Djerfi proposed to make lenses from plastic, and a little later his colleague Kevin Tauki reduced their size for greater convenience and comfort of users. But the new model also had its drawbacks. The hard plastic was awkward to use, so the introduction of the first soft contact lens was seen as a breakthrough.
Czech polymer
The material from which modernized lenses began to be made in the fifties of the twentieth century was invented by the Czech scientist Otto Wichterle. He created a polymer capable of oxygen permeability and liquid absorption. In 1988, the well-known company Johnson & Johnson released the first batch of daily lenses, which received great recognition from buyers.
Today, lenses are made from silicone hydrogel. You can even buy them in vending machines, and most importantly, with their help you can not only improve your eyesight, but also change the color of your eyes to suit your mood. However, the invention of hydrophobic lenses did not put an end to the matter of vision correction, experts are working on a material that was not rejected by the mucous membrane and would be completely devoid of the disadvantages of modern silicones.
Help to see all the colors of the world, while they themselves remain invisible. Provide comfort and self-confidence... They can even radically change their appearance in a matter of seconds.
These are contact lenses. Yet several centuries ago the great minds of the whole world began to dream of a magical device that can instantly correct a person's vision.
Leonardo da Vinci, Rene Descartes, Thomas Jung and many other scientists have worked for many years to make this dream come true.
The history of prototyping contact lenses for the eyes
The advent of contact lenses for the eyes was preceded by several major discoveries.
René Descartes
In 1637 French physicist, mathematician, physiologist Rene Descartes invented an optical instrument like a telescope.
It was a tube filled with water, into which a magnifying glass was inserted. Opposite side the device was attached to the visual organ. Direct contact with the cornea of the eye is the only similarity of Descartes's invention to a contact lens. This tube was quite traumatic and extremely inconvenient in application (the person who used it could not even blink).
Thomas Jung
In 1801 English physicist Thomas Jung improved the invention of Descartes. Jung's tube was shorter, allowing beams of light to focus on the retina. To mount the device, Jung used wax.
John Herschel
Jung, in turn, inspired the English scientist John Herschel to systematize all the inventions of that time in the field of vision correction.
In 1823 Herschel described in detail the design of the corneal lens. A in 1845- proved the possibility of treating astigmatism with a device in contact with the cornea of the eye.
The scientist called it a device "Optical capsule" and argued that it should be transparent, made of glass or some jelly-like material and repeat the shape of the cornea.
Herschel limited myself to theoretical research, but many of the principles described by him formed the basis for the manufacture of modern contact products.
Siegrist and Lonstein
Late 19th century the British Lonstein and Siegrist created a device for the treatment of deformed cornea - hydroscope... They were large goggles, like a scuba diver's mask. The hydroscope was sealed to the face and in contact with the eyes through the liquid with which it was filled. The glasses were bulky and uncomfortable, long-term wearing damaged the skin around the eyes: it softened due to constant contact with water.
When the first models were invented that stay on the eye
The invention of lenses that hold onto the eyes is merit of several outstanding personalities.
Adolph Fick
1888 year is the date of the invention of the first products that can truly be called contact lenses. A famous Swiss doctor described such a product Adolph Gaston Eugene Fick... It was made of glass and weighed about 0.5 grams. The scientist did a great job to bring his idea to life.
He started from the manufacture of corneal optical products(which cover only the cornea of the eye), and a little later created and scleral(which are partially adjacent to the sclera).
The scientist preferred the latter, as they were more securely attached to the eye. Manufacturing was a very painstaking process, they cast on the basis of plaster casts of cadaveric eyes.
First, Fick tested them on animals, and then decided to "try" them on to people, tested them on himself. He studied in detail the impact of his invention on the eye, detailed the adaptation period and compiled a very detailed guide to the use of his lenses.
In 1896 the light saw the textbook of Adolf Fick, where it was described eight directions development of the science of vision correction. Fick lenses have been used to treat astigmatism and keratoconus.
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Eugene Calte
March 20, 1888 Frenchman Eugene Calte announced the invention of special corneal lens products for the treatment of keratoconus. In fact, Kalt's lenses could not be called corneal, because they also had an opaque part that rested on the sclera. Kalt's invention held firmly on the eye, but irritated the eyelids.
August Müller
German inventor August Müller did not know about the discoveries of Adolf Fick, so he began to work on the creation of contact lenses literally from scratch... And he tested his inventions before his own eyes. In 1889 Müller was the first to start making products by the method of casts from the visual organs.
Photo 1. One of the first prototypes of scleral contact lenses. The items were made of glass.
This technology was adopted by many of his followers. And also he became the first to think about over the problem of lack of oxygen under the lens eyepiece... Müller tried to solve this problem by filling the space between the lens and the cornea with water, but the water caused the corneal edema.
Carl Zeiss
In 1913 the mass production of contact products was started by the factory of the German inventor Carl Zeiss... Zeiss produced polished products which were better tolerated by the eye than Mueller lenses. Corneal lenses were not very successful because they were poorly adhered to the eye. From scleral such problems did not arise.
In the 20s of the twentieth century the factory began to produce different sets, from which doctors could choose lenses individually for each patient. Of course, this selection was pretty rough.
In what year did the method of correcting vision with lenses appear?
In 1938 the americans D. Mahler and T. Obrig began a new chapter in the history of vision correction.
They decided to use it to make scleral lenses synthetic plastic polymethyl methacrylate, or abbreviated PMMA.
This made it possible to make lenses practically weightless... Now they fit perfectly on the eye and did not slip, unlike glass ones.
This advantage of PMMA allowed the transition to the production of corneal types. AND in 1947 corneal plastic lenses appeared with a diameter of 1.2 centimeters. They were much lighter and more comfortable than the scleral ones. With its obvious advantages plastic also had disadvantages: it caused severe discomfort and irritated the cornea of the eye.
In the sixties of the twentieth century German ophthalmologist Otto Wichterle patented a new material for making lenses - synthetic polymers. Thanks to him, the lenses became not only very light, but also soft. Now they were practically not felt on the eye. Patients' confidence in this type of vision correction has grown significantly.
The state of lens products in the modern world
In our time, ophthalmology has reached the highest level, and the choice of contact lenses is huge. You can choose hard types: they are gas-permeable or gas-tight. Or opt for more popular soft lenses. There are two varieties soft types: hydrogel- very firm, elastic and smooth, and silicone hydrogel- good air permeability and keep in shape.
Photo 2. Modern soft contact lenses. The products are very light, practically not felt before our eyes.
There are several types of products that differ in the mode of wearing and replacement period. Modern types of lens eyepieces are distinguished even by purpose. In addition to optical, designed to correct vision, there are cosmetic ones designed to change the color of the eyes.
Attention! The main advantage of a contact lens over glasses is no distortion of objects.
When they came up with colored eye lenses
For the first time such decorative lenses appeared in 1981. Their release was started by a corporation CIBI Vision. It is interesting that initially colored items were produced not to change their appearance, but for more convenient handling, because such a product is more difficult to lose than a transparent one.
In 1984 at CIBI Vision began to produce lenses for changing the color of light eyes. People with dark eyes were able to try on a different shade only in 1991.
28-08-2013, 19:13
Description
The following dates are important in the history of contact lenses. In 1801 T. Jung used in the experiment a short tube filled with water with a biconvex lens, which, when attached to the eye, compensated for the lack of refraction of the eye.In 1845, an English physicist J. Herschel published theoretical studies that substantiated the correction of corneal astigmatism using an optical system in contact with the eye. In 1888, a Swiss ophthalmologist A. Fick published article "Contact glasses", where he described a contact lens: “A glass cornea with a radius of curvature of 8 mm sits with a base of 7 mm on the glass sclera, the latter being 3 mm wide and corresponding to a ball with a radius of curvature of 15 mm. Glass cornea with parallel walls inside and out, ground and polished; in the same way, the free edge of the glass sclera was ground and polished. The weight of one contact glasses is 0.5 g. " After experimenting on animals, Fick ventured into the human eye. First, he made plaster casts, and he used them to blow his first trial lenses.
The first contact lenses were scleral, large in diameter (from 21 to 16 mm), consisted of a haptic part resting on the sclera and a central optical part refracting the rays. The lens space was filled with glucose-containing fluid or saline. The first production of contact lenses was carried out by a renowned glass blower Müller from Wiesbaden(Germany). The lenses were ordinary ocular prostheses. The scleral part was made of white glass. In place of the pupil, the lens had a transparent part. Later (1914–1924), the mass production of contact lenses was undertaken in Germany by a famous optical company "Karl Zeiss" which released their sets. Using sets containing lenses of different parameters, the optimal shape for a given eye was selected and an individual lens was made using it.
The first scleral lenses were made from glass. In 1937, an American ophthalmologist V. Finebloom began to make lenses in which the scleral part was made of plastic, and the corneal part was made of glass. In the same year I. Dyerfi and T. Obrig made contact lenses entirely from plastic, polymethyl methacrylate. In 1948 K.Tuokhi proposed solid corneal contact lenses, which were made of plastic, polymethyl methacrylate. Their sizes were much smaller than scleral ones. Unlike scleral lenses, which have been held on the eye for centuries, corneal lenses are held on the cornea by capillary attraction. The small size of the corneal lenses, the easier access of oxygen to the cornea made it possible to significantly improve their portability and wear period (up to 10–12 hours). With the advent of corneal contact lenses, the rapid development of contact vision correction began, the designs and methods of selecting hard corneal contact lenses were improved.
In 1960, Czechoslovak scientists - academician O. Wichterle and engineer D. Lim- synthesized a new polymer material, developed a method of rotational polymerization and carried out the production of soft contact lenses. Soft lenses are well tolerated due to their hydrophilicity, elasticity, and oxygen permeability. The indications for the appointment of contact lenses have also expanded: soft lenses are used not only for optical correction of refractive errors, but also for therapeutic purposes in certain eye diseases. In addition, it became possible to produce cosmetic, colored lenses.
Types of contact lenses
All types of contact lenses can be divided into several groups depending on the material from which they are made, the mode of wearing, the design of the lenses, their purpose, the degree of transparency. According to the material, they are divided into hard and soft.
Rigid lenses, in turn, are divided into rigid gas-tight and more modern rigid gas-permeable. Soft lenses are divided into hydrogel and silicone hydrogel... Hydrogel lenses are divided into 4 main groups (FDA groups) based on the moisture and ion content of the material. 1st group - low hydrophilic non-ionic material; 2nd group - highly hydrophilic non-ionic material; 3rd group - low hydrophilic ionic material; 4th group - highly hydrophilic ionic material.
According to the mode of wearing, contact lenses are divided into:
- traditional (service life of soft lenses - up to a year, hard lenses - several years);
- planned replacement (replacement of lenses once a month or every few months);
- frequent planned replacement (service life - one day, week, two weeks);
- prolonged wearing period (can be worn without removing for up to 30 days in a row).
There is also a flexible wearing regime where lenses can sometimes be left on for one or two nights.
By design, contact lenses are divided into:
- spherical (lenses are designed to correct myopia and hyperopia);
- toric (correct astigmatism);
- multifocal (used to correct presbyopia).
By appointment, contact lenses are:
- optical - designed to correct refractive errors (myopia, hyperopia, astigmatism); decorative - designed to change the color of the eyes; tinted - change the color of light eyes; colored - change the color of dark brown eyes; "Crаzy" - lenses with a pattern applied to them, for example, "Red Spiral", "Wolf's Eye"). These lenses are worn for 2-3 hours, they are not intended for daily wear; therapeutic - lenses are used in clinical practice to treat corneal pathologies.
Contact lens care
Because lenses are mostly water, they can become susceptible to microbial contamination; in addition, deposits can form on the lens surface. Therefore, soft contact lenses should beclean and disinfect thoroughly.
- Place the lenses on an open palm and apply a few drops of lens cleaning solution. Use your index finger to gently rub the lens surface.
- After cleaning, rinse them with solution.
- Place each lens in the corresponding cell of the container. Pour fresh solution there. It should completely cover the lens. Do not use the same solution twice. Close the case lids carefully and leave the lenses in it for at least 4 hours.
Many solutions allow lenses to be stored in it for 30 days without changing the solution. When using contact lenses for more than three months, it is recommended to add an additional enzyme cleaning to the care. There are special protein purifier tablets available that are used once a week.
- Rinse both wells of the lens storage container with solution.
- Fill the cells with fresh solution.
- Dissolve one protein cleaner tablet in each well.
- Remove, clean and rinse the lenses in the usual way, and then place them in the wells of the container.
- Close both covers, shake the container, and soak the lenses in the solution for 15 minutes. Heavily soiled lenses can be held for a longer time, but no more than two hours.
- Remove the lenses from the container and rinse them with the solution.
- Discard the used solution. Rinse container thoroughly and refill with fresh solution.
- Place lenses for disinfection and storage. After disinfection, the lenses can be worn over the eyes.
Remember! Lubricating Drops is a sterile lubricating and moisturizing solution that provides long-term comfortable contact lens wear. Use drops to relieve contact lens discomfort, especially during the adaptation period.
Modern methods of contact lens care can be divided into three categories:
- Multifunctional solutions. They combine cleaning and disinfection, some of which remove protein deposits. Such solutions are easy to use and rarely cause complaints from patients. However: disinfection takes several hours; manual cleaning must be done very thoroughly and must be learned.
- Systems in two parts. The cleaner and disinfectant are in separate containers. Such systems provide more thorough cleaning than multifunctional solutions; some of them disinfect in just 20 minutes.
- Hydrogen peroxide. Contains no preservatives and is very effective against bacteria, viruses and fungi. The peroxide must be neutralized before placing the lens in the eye.
When choosing a care system, the following points should be taken into account.
- The period of wearing contact lenses. The short-term lenses require little maintenance, so a multi-functional solution can be dispensed with.
- Elderly people require easy-to-use multifunctional solutions.
- If you rarely use lenses, then the likelihood of protein deposits is small, in this case, a multifunctional solution is sufficient.
- Sediment formation. Large deposits require serious, thorough cleaning. It is unlikely that a multifunctional solution will help here.
- Predisposition to allergic reactions. In such cases, hydrogen peroxide is preferable - it does not cause allergies.
- Previous cases of herpes or fungal infections. Such people are better off using hydrogen peroxide.
- Lifestyle and occupation. Here it is necessary to bear in mind the following: women who use a lot of cosmetics should clean their contact lenses more thoroughly; work in clinics, swimming pools increases the likelihood of microorganisms entering the eye. And if the above-mentioned type of activity applies to your client, then it is better for him to use hydrogen peroxide.
How to properly wear contact lenses
Before putting on your lenses, wash your hands with soap that does not contain fragrances or emollients. Rinse off the remaining soap from your hands under running water. Keep your nails short and clean (you have to choose between a luxurious manicure or wearing lenses). Check if the lens is turned inside out, debris, or damaged edges.
Before putting on the lens, rinse it with a small amount of solution and do not touch the inner surface of the lens with your hands. Put on the right lens first. When putting on the right lens, look up and to the left, and the left lens up and to the right. Pull the lower eyelid down with your left hand. Place the lens on the eye with your right hand, lightly press the lens and, without blinking, remove your hand. Let go of the lower eyelid and slowly close your eyes. Place two fingers on your upper eyelid and massage gently to remove the air bubble from under the lens and position the lens correctly on the cornea. If the lens has shifted to the corner of the eye, up or down, move it to the cornea with the tip of your finger, or by lightly pressing the upper or lower eyelid, push the lens towards the cornea and center it.
Close your eyes for a few seconds so that the surface of the lens is covered with a tear film. If you feel uncomfortable after putting on the lens, remove it and check if it is worn correctly, rinse it and put it back on. In the first days of wearing lenses, when the adaptation period passes, it is necessary to abandon mascara, the use of artificial eyelashes, and the use of oily face creams.
Full adaptation to contact lenses occurs in 2–4 weeks, when there is no redness of the eyes, watery eyes, and foreign body sensations. Wear lenses before applying makeup, and remove before washing off.
How to remove contact lenses correctly
When you remove your contact lenses, wash your hands with soap and water and stand in front of a mirror. Begin to remove the first lens that you put on in the beginning. Bend your head forward, look up. Use your index finger to slide the lens down onto the sclera. Gently squeeze the lens between your index finger and thumb and remove it. This method avoids corneal injury.Article from the book:.
