A glasses (also called eyeglasses ) is since the 13th century before the eyes worn construction that in the majority of cases as optical aids refractive errors and mistake corrected eye and as such prescription glasses or prescription glasses called. In addition, glasses are used to protect against external influences, injuries or overstimulation as well as for therapeutic , diagnostic and experimental purposes. Glasses are also important as a fashion accessory .
A pair of glasses consists of spectacle lenses, which either have a refractive effect as ground lenses and serve as visual aids , or of cast panes or glasses made of different materials that can serve different purposes. In addition, it has a frame for stabilizing and fixing the spectacle lenses , which can consist of different materials, sizes and shapes, as well as a holding device (ear hook, handle or behind-the-head strap).
Today's glasses manufacture in Germany is based on standards and guidelines. Often, opticians produce the end product from industrially or manually prefabricated components and deliver the finished glasses to the customer. The necessary glass thickness is determined beforehand using reading tests and technical aids, usually at the optician's or the ophthalmologist's . In Germany, around 64 percent of people over the age of 16 and around 15 percent of children need corrective glasses. In Germany, glasses have been paid for by the statutory health insurance funds (GKV) in simple designs since the 1930s . Visual aids are still listed in the GKV list of aids . However, the costs for their production are only covered with considerable restrictions.
The term glasses is derived from the late Middle High German word berille (from Greek-Latin beryllus ). This in turn is attributed to the mineral beryl . Viewing windows for reliquaries and monstrances were cut from this semi-precious stone. Around 1300 lenses and glasses were made from cut semi-precious stones . The name of the gemstone beryl (Latin form beryllus; it is also the namesake for the element beryllium it contains ) was used in the Middle Ages as a generic term for all clear crystals, even if they are made of other material such as B. Rock crystal passed. In 1303 the expression "oculus berillius" was used by Bernhard von Gordon in Montpellier.
Albrecht gave the berillus in the Younger Titurel an increased symbolic meaning. In the extensive Grail poetry from around 1270, Parille is the name for one of Senabor's sons. When listing the "kinde und kindes kint" from the Kapadoze tribe , the name is mentioned:
“A sin sun parille he hisses after the stone, / through this the eye will come with it. he makes big and small ones. / uz cleinen virtues he made di grozen. "
“He named one of his sons Parille after the stone. So that the desire of the eyes may go through there. He makes big out of small. He made big ones out of small virtues. "
The choice of the name clarifies the life of the "Parille" and shows its development. This stanza represents the oldest monument in the German-speaking area in which glasses (here still as a rock crystal reading stone) are mentioned. Many stanzas later, Albrecht takes up the comparison again:
"Sam the berillus grozet di script in the ze lesene, din the heart of the genozet, in it all virtues with essence are high, wide, wit and ouch di lenge."
"Just as the Beril enlarges the writing to be read in it, your heart resembles it, in it all virtues in their essence grow high, broad, wide and also in length."
The heart is clear and pure like a "berillus" and has the property of allowing the virtues to grow.
Forerunner of glasses
Contrary to assumptions to the contrary, the Egyptologist Alfred Wiedemann doubts that glass lenses with noteworthy optical properties already existed in ancient Egyptian times (6th century BC), but only recognizes storage vessels in them. According to Chrysippos , however, Archimedes († 212 BC) is said to have investigated the laws of refraction of lenses and to have worn a crystal attached to the head for vision correction. His discovery apparently found no practical imitation in antiquity. Emperor Nero is said to have viewed the gladiator fights through glasses, but these were without breaking effect. They were only used to protect his eyes from the sun. Seneca the Younger wrote in the 1st century AD: "Small and indistinct letters appear sharper and larger when viewed through a ball filled with water."
The book Treasure of Optics by the Egyptian mathematician, astronomer and optician Alhazen († approx. 1040) provided new approaches after it was translated into Latin around 1240 and made available in monastery libraries . Alhazen described the magnifying effect of a segment of glass spheres, the later reading stone , but without using his knowledge in practice. Alhazen's studies, the craft of writing monks and the rapidly growing use of writing in urban areas came together. The first rock crystal reading stone was probably cut in a monastery. Reading glasses and glasses followed around the second half of the 13th century.
In addition to the treasure trove of optics , a remark from The Golden Forge by the Middle High German poet Konrad von Würzburg (* 1220/1230 in Würzburg, † 1287 in Basel) showed a possible direction of development: "He [the crystal] has the great and mighty kind, [...] if someone sanded it thin and wanted to hold it on the writing, he would see the small letters appear larger through him. "
Invention of glasses
The reading glasses placed on the nose as a visual aid for both eyes were invented at the end of the 13th century in northern Italy, possibly in Tuscany . Important preparatory work was done by Roger Bacon , who in his work Opus maius , published in 1267, provided essential insights into physical optics and believed that spherical segments made of glass were excellent aids for the poorly sighted. Salvino degli Armati was long considered the inventor of glasses until it became known in 1920 that he himself was an invention. Also the doctor Petrus Hispanus, from 1276 Pope John XXI. , is considered today as an inventor. Ultimately, it is still not clear who invented glasses (between 1270 and 1290). The Dominican Giordano da Rivalto mentioned the invention only a few years ago in a sermon manuscript from 1305 and announced that the Dominican Alessandro della Spina, who worked in Pisa, had mastered the grinding of glasses ( ocularia ) around 1285 , but had also communicated that the real inventor of the glasses does not want to be named.
By 1300, eyewear production was already established in Murano . For example, the use of unclean glass was prohibited. The Great Council of Venice named 1300, 1301 and 1319 lapides ad legendum ("reading stones") and vitreos ab oculis ad legendum ("reading glasses"). Arnaldus de Villanova mentions the casual sine specillis ("reading without glasses") in his wine book in an ophthalmological section around 1310 .
“For the first appearance and the further spread of the knowledge that a specially cut rock crystal can enlarge font, far less theoretical explanations associated with a few famous names are responsible; it is much more the concrete and practical experience of those who were busy in workshops with making shrines, lecture crosses , reliquaries and the like. […] There are […] [many] examples in which such a stone with a magnifying effect is in front of particularly small relics. "
“In the medieval jewelry workshops, plano-convex cut gemstones were often used in the manufacture of shrines, lecture crosses and reliquaries. These were not only used for jewelry, but also functioned as magnifying sight glasses when they were placed in front of particularly small relics. "
Their magnification effect has long been exploited - although initially not for reading. The transition to increasing font size is considered very obvious.
The oldest representation of glasses can be found on the frescoes by the Italian painter Tommaso da Modena in the chapter house of San Niccolo in Treviso . They were created around the year 1352. With a great sense for the representational and for physiognomic peculiarities, da Modena has depicted the main representatives of the Dominican order on forty frescoes. In the portrait of the Cardinal of Rouen , a single glass is shown, which the sitter has brought close to his eye. He is reading with it in a book that he holds open in his hands. In the portrait of Cardinal Hugh of St. Cher one is Nietbrille shown that this is stuck on the nose.
The “glasses apostle” on the altar of the town church of Bad Wildungen , which was painted by Conrad von Soest in 1403 , is the earliest representation of glasses north of the Alps. The glasses apostle has become a symbol of the evangelical parish of Bad Wildungen and can be found today in its seal. An older representation of glasses can be found on the winged altar of Tyrol Castle (1370/72) in the Tyrolean State Museum Ferdinandeum in Innsbruck . On the right wing of the Sunday side, the bottom depiction is dedicated to the death of the Virgin . Two apostles sit at the foot end , one of whom holds riveted glasses in front of his face.
Two early apostles with glasses can also be seen in the choir of Aachen Cathedral . In addition to the two central statues of Mary and Charlemagne on the inner pillars of the choir, the twelve apostles are placed on consoles under canopies . After the completion of the choir hall, the sandstone figures, whose artists have not been passed down, were installed between 1414 and 1430. Thomas is on the south side. He is holding an open book in his right hand. Its attribute, the angle measure, hangs in the crook of the arm and is clamped between the chest and the left forearm. Thomas wears a knife and a glasses case on his leather belt . Matthias stands on the north side of the choir. His left hand grasps the long shaft of the halberd placed on the ground. He looks into an open book. The right hand is hidden under the cloth of his coat. Only the thumb sticks out and presses half-open rivet glasses against the book cover from below.
People who wear glasses can also be found on the altar by Friedrich Herlin in the Jakobskirche in Rothenburg ob der Tauber . Created around 1466, the Predella shows Peter with a bunch of keys and a book. The apostle holds his riveted glasses in front of his eyes to read. In the circumcision scene on a side wing of the altar, the painter has put glasses on the high priest's nose.
In the Orient, where Alhazen laid the foundations for modern optics, effective glasses were probably less common at first. So says Jami narrated his story of Salaman and Absal that he saw so bad that not even "Frankish glasses" would help.
The possibility of correcting nearsightedness with concave or biconcave diverging lenses has been known since the 16th century, but not attested before 1525. Another step is the development of the bifocal glasses , whose inventor Benjamin Franklin is considered. It was annoying for him to constantly swap his distance glasses for reading glasses. Around 1784 he came up with the idea of assembling two spectacle lenses with a corresponding optical effect for the right and left eye, a construction that was initially called Franklinglas . The first patent for the idea of a progressive lens was awarded to the American Henry Orford in 1909.
The development of spectacle frames also made progress. Around 1727, the English optician promoted Edward Scarlett with a temporal glasses with side brackets which reached to the temple. This was followed in 1752 by James Ayscough's kink rod goggles, with horizontally double-hinged side parts, who advertised them as his invention. Here for the first time the bracket (a stirrup) reached over the ear (resting on top) and was held at the back of the head (crown). These glasses were the first of the ear glasses category. Not too long later, the horizontally foldable rear stirrup bars could then be angled behind the ear with a vertical hinge. This variant was then in use until the end of the 19th century. At the same time, there was also the stirrup version without a central hinge, which was also often referred to as women's glasses. The webbing hanger followed around 1880, and it wasn't until the beginning of the 20th century that the golf hanger with a Cellhorn cover, which is still in use today, came out. In addition to temple glasses, non-wired alternatives in the form of lorgnons , monocles or pince-nez were still in demand until well into the 20th century.
Moritz von Rohr from Carl Zeiss AG , together with H. Boegehold and A. Sonnefeld, developed the aspherical punctiform lens ( aspherical Katral lens ) for highly farsighted people (star-operated patients) with well over +22.0 diopters (dpt) in 1912. From the findings of the Katral lenses, Zeiss developed the calculation basis for spherical concave-convex lenses for lens thicknesses up to max. ± 12.0 dpt. After six centuries of eyewear development, these lenses produced a clean image right down to the edge of the lens for the first time. The previous bi-convex and bi-concave lenses disappeared from the market between 1913 and 1915 and were also replaced by the new meniscus lenses at the other well-known lens manufacturers (Rodenstock, Busch, NG, etc.). The first progressive lens was brought onto the market in France in 1959 by the Société des Lunetiers and was called Varilux . The constant further developments, which have been carried out by various companies to this day, primarily serve to improve the image quality while at the same time reducing optical and cosmetic side effects as well as safety and comfort; not all companies make both glasses and frames.
As late as the 1920s, it was still a matter of dispute in Great Britain whether glasses belonged to the optical instruments (like the microscope ) or whether the spectacles , together with the monocle, formed a separate category. It concerned the import duties for optical instruments set out in the Finance Act of 1926. On October 6, 1927, the British Government's Trade Committee decided that "visual aids in everyday language as well as in the normal commercial diction [are] not optical instruments and therefore do not fall into the same class as optical instruments." not the customs regulations for optical devices.
In West Germany there were only six plastic frames for adults and two for children until the early 1980s , the costs of which were covered by statutory health insurance . They were therefore called “cash racks”. In 1972 the optician Günther Fielmann founded an optician's shop in Cuxhaven . He saw a niche in the market for prescription glasses, which were not very popular. In 1981 the eyewear company signed a special contract with AOK Esens and created 90 models made of metal and plastic in 640 variants. This ended the era of standardized checkout glasses in Germany.
The number of people who wear glasses has risen continuously since statistical records began. According to a study by the Allensbach Institute commissioned by the Board of Trustees for Good Vision in 2008, 62 percent of people over the age of 16 in Germany wear or need corrective glasses, 8 percent more women than men. At the time of the first survey in 1952, only 43 percent of the population wore glasses.
Especially in the age group of adolescents and young adults there was an increase from 13 percent to 26 percent. Due to intensive education, preventive care, early detection and improved diagnostic procedures, there is a tendency to wear glasses at an early stage. The number of children wearing glasses was given in 2010 as 15 percent and the trend is increasing. In the 1970s it was 8 percent, and in the early 1990s it was 11 percent. In addition to the general increase in glasses wearers, children and adolescents also see a trend towards beginning wearing them earlier, although 70 percent of those questioned in the study were certain that children would be teased about their glasses. According to the professional association of ophthalmologists in Germany (BVA) and the German Ophthalmological Society (DOG), around 20 percent of all children need glasses. Other sources speak of over 30 percent.
The acceptance of glasses in Germany is high, so that, according to this study, 91 percent of those who wear glasses and 82 percent of those who do not wear glasses are of the opinion that glasses do not have a negative impact on the attractiveness of the wearer. In the 2000s, glasses gained significantly in importance as a fashion accessory .
The prevalence of prescription glasses is very different worldwide, it depends on the level of development of the country and the prosperity of the inhabitants. In countries of the Third World , there is often not only a lack of the financial means to procure the glasses required, but also their regional availability. To remedy this problem, the OneDollarGlasses was developed.
Corrective lenses have an optical effect, changing the beam path of the light entering the eye and thus the position of the focal point . They are used to correct optical ametropia - also known as refractive errors or ametropia - and thus improve the often reduced visual acuity . The optical effect of a spectacle lens is also called the lens thickness and can be measured on the lens with a special device, the lensmeter . The glasses size is usually on the inside of the temple or on the bridge, for example 52–17–135 (52 mm lens size, 17 mm bridge width, 135 mm temple length). These values are available in eye prescription , which is handed out with the glasses. The type and size of the glasses correction depends on the individual needs and requirements of the user.
The first pair of glasses usually takes some time to get used to. In addition to the unfamiliar foreign body in front of the eyes, the main cause is the changed visual impressions. These can also occur if new glass thicknesses differ significantly from those previously worn. Since glasses are primarily used to correct ametropia, they also increase visual acuity to a certain extent. So there is an immediately noticeable improvement that makes it easier to use the correction regularly. While acceptance can decline for a variety of reasons, especially among children, children are usually rarely averse to wearing glasses when they meet their needs. It has therefore proven to be advantageous if you can choose your glasses yourself within the framework of the recommendations. There is also an association with growing up, which in connection with a positive attitude of the parents towards glasses has proven to be a further acceptance criterion.
Not every correction automatically leads to an immediate improvement in visual acuity. There are cases in which the wearer does not initially see much better with new glasses, and in some rare cases even worse than without the new correction. This is because in certain respects the eyes have to get used to the glasses and in no case does it mean that the correction is incorrectly adjusted or even superfluous or of little use.
To determine the extent of ametropia (ametropia) and the later lens strength, certain examinations ( objective and subjective refraction determination) are necessary, which should be carried out by an ophthalmologist before initial treatment.
In children in particular, when the objective refraction measurement is carried out for the first time, it must be prepared with special eye drops for the short-term expansion of the pupil ( mydriasis ) and the elimination of accommodation ( cycloplegia ). Only in this way can the actual values of ametropia be determined exactly, since otherwise the involuntary accommodation impulse could falsify the measurement to a considerable extent. In practice, however, this procedure is often not used in adults.
As a rule, a further examination of the subjective refraction is then necessary in order to determine the final spectacle values. This is done with a phoropter , less often with the test racks that used to be common . If a prism regulation is also necessary, further special examinations are carried out to determine the prism strength and base position .
In many cases, ophthalmologists prescribe the corrective glasses. The strength of spectacle lenses is the result of measurements of the objective and subjective refraction carried out beforehand . The values determined are transferred to a special prescription for vision aids , which is given to the optician to manufacture the glasses. The optician can issue a glasses pass for documentation .
Myopia and farsightedness are corrected with spherical lenses , astigmatism with cylindrical lenses that only have an effect in a certain axis (main section) . The value of a spectacle lens therefore consists of a spherical and possibly a cylindrical part with the designation of its axis position. If it is necessary to incorporate prisms in one or both lenses, the corresponding values (power in prism diopters, base position in degrees) are also entered in the fields provided.
In the case of particularly thick glasses, it is important that the correction is positioned very precisely in order to achieve an optimal result. The distance between the lenses and the eye plays a decisive role. This value is called the corneal vertex distance or simply vertex distance . The distance between the eyes, the pupillary distance (PD), is also important. If necessary, both values are entered in the prescription for vision aids and given in millimeters.
For visual documentation of the main section information of a cylinder value, this can be drawn in the semicircular TABO scheme .
Corrective glasses are mostly manufactured industrially. The main components of eyeglass lenses and eyeglass frames are created in different production processes , which are then usually processed by the optician into the finished product and then delivered to the customer. Nevertheless, the technical aspect in the manufacturing process plays a major role for many opticians.
The equipment and quality of glasses varies from product to product. In general, however, they meet the basic requirements with regard to their use in all aspects of durability, functionality and safety. Their manufacture is subject to standards and quality rules that are defined in Germany by the Precision Mechanics and Optics Standards Committee (NAFuO) .
The blanks for spectacle lenses are made as round lenses from different materials. The materials differ in optical and mechanical properties. A rough distinction can be made between mineral glass and plastic. Mineral glass is harder, but also heavier than plastic. Both mineral glass and plastic are available with different refractive indices . A high refractive index allows a thin and therefore light spectacle lens. In earlier times spectacle lenses were made almost exclusively from mineral glass. After advances in polymer chemistry and manufacturing technology , plastic glasses have been predominant in Germany for several years.
The optician uses computer-controlled grinding machines to shape the blanks into a shape that fits into the glasses frame. The distance between the eyes, which varies from person to person, is taken into account.
The refractive power, also known as the refractive index , or power of a spectacle lens is given in the unit dioptre (dpt) . Since the corrective lenses are positioned in front of the eye, they cause aberrations in certain areas to which spectacle wearers usually get used. With regard to the optical effect, a distinction is made between spherical , cylindrical / toric , multifocal and varifocal lenses .
A further development of the surface geometry with the aim of correcting imaging errors are the aspherical , biaspherical , front and rear surface progressive free forms . These have the same dioptric power as spherical, toric or varifocal lenses. These terms describe the optically effective design of the two glass surfaces through which the light falls, i.e. the course of their curves.
Spherical positive lenses (plus lenses) are used to correct farsightedness . Since the focal point lies behind the retina with this refractive error , they have a collecting effect ( converging lenses or convex lenses ). Your value is given a plus (e.g. +0.75 D) as a sign . The viewed object is enlarged. If you move the plus lenses back and forth horizontally or vertically in front of your eyes, you can see that the object viewed through the glass is shifting in the opposite direction to the direction of movement (in the opposite direction ) . A pincushion distortion occurs as an imaging error .
Minus glasses are negative spherical glasses that have a scattering effect (diffusing lenses or concave lenses ) and reduce the size of the object being viewed. They correct a nearsightedness in which the focus is in front of the retina. Its value is given a minus sign (e.g. −1.25 dpt). In contrast to plus lenses, objects viewed through a minus lens move in the same direction as a lens is moved back and forth in front of the eyes (moving) . A barrel-shaped distortion occurs as an imaging error .
With cylinder lenses a is astigmatism (astigmatism, astigmatic) corrections. This is a toric glass , which has its optical effect only in one axis (main section) of the glass and consequently has no focal point, but a focal line. Since the correction consists of a combination of spherical and toric lenses , these are also called sphero-toric lenses. It has two main sections perpendicular to each other, the arithmetic mean of their refraction being referred to as the spherical equivalent . This combination also allows the value of a cylinder to be represented both positively and negatively using a conversion formula. However, nothing changes in the refractive effect. During the conversion, the sum of the sphere value and the cylinder value forms the new sphere value, the sign of the cylinder value changes and the axis value shifts by 90 ° (but is always between 0 ° and 180 °). The following glasses values , for example, have an identical effect: +1.00 −0.50 / 0 ° and +0.50 + 0.50 / 90 ° . The reading for these two values is:
- +1.0 sphere combined with −0.5 cylinder in axis 0 degrees or
- +0.5 sphere combined with +0.5 cylinder in axis 90 degrees.
While in optometric terminology opticians prefer the notation with plus cylinders and the invoices to the customer are formulated accordingly, ophthalmologists mostly use the notation with minus cylinders - also in the prescriptions, which regularly leads to corresponding uncertainty among patients or customers with regard to their actual situation Glasses strength leads and repeatedly causes need for explanation.
In many cases, the glass thickness is also noted directly by specifying the existing main cuts. In the example above, the reading is as follows:
- HS1 +1.0 HS2 0.5 in axis 0 degrees. or.
- HS1 +0.5 HS2 1.0 in axis 90 degrees.
Single vision lenses
Corrections for glasses whose lenses only have one focal point are collectively referred to as single vision glasses . As a rule, they represent the full correction of an existing ametropia (nearsightedness, farsightedness) and thus result in an artificial emmetropia with age-appropriate visual acuity at all distances. Some single vision lenses are only used for a certain distance range. These include, for example, so-called long- distance glasses for good vision at maximum distance, which may not have to be used if there is near-sightedness. Reading glasses, on the other hand, are intended for close distances (usually up to around 40 centimeters), which, however, can be superfluous for long-distance vision. But corrections can also be made for all intermediate distances, for example for screen activity at a distance of about 60 centimeters.
Single vision glasses are ideal if a visual aid is necessary over a certain period of time and within a roughly constant distance. The advantage here is that the lenses are lighter and enable a clear picture over their entire size. On the other hand, it can be a disadvantage that the glasses may have to be removed or changed for different distances.
Corrective glasses whose lenses have more than one focal point are collectively referred to as multifocal or multifocal glasses. These include bifocal glasses as visual aids for two fixed distance ranges (usually distance and near) and varifocals for seamless correction for all areas between distance and near or as so-called near comfort lenses for the extended near area between 40 and 100 cm. For special areas of application there are special trifocal glasses with optical effects for three different distances.
Multifocal glasses are ideal if, in addition to a refractive error, presbyopia is to be corrected, as well as for activities that involve different distances and for which a different correction value is necessary. The advantage is that you don't have to change glasses every time you switch between the individual distances. A disadvantage can be that only part of the spectacle lens is available for the desired optical effect. In addition, in the case of spectacle lenses with an optical effect for the close-up range in the lower half of the lens, more distant things on the floor etc. may become blurred when looking down (climbing stairs).
Due to the manufacturing process, the optimal area of a progressive lens runs in a curve from top to bottom and a little inward (the progression canal ). The optimal diopter values in the varifocal area are only achieved on this line. How wide the tolerance range is to the left and right of this line depends on the quality of the lens, but also on the close-up correction.
A further development of the varifocal lenses (progressive lenses) are the free-form lenses ("FreeForm"): lenses that are created individually for each eye of the customer and are therefore unique. The concave surface of the lenses is calculated using complex algorithms in LDS (Lens Design Software). These surfaces are then processed on high-quality CNC precision machines with high speed cutting .
- Density : Plastic is lighter than glass
- Hardness : Glass is harder than plastic, but can break more easily and therefore in some cases carries an increased risk of injury.
- Refractive index : A higher refractive index enables thinner and therefore lighter glasses. The values for the refractive index range from around 1.5 to 1.75 for plastic glasses and from 1.5 to 1.9 for mineral glasses.
- Abbe number : It indicates the dispersion of the glass that leads to color aberrations at the edge. Glasses with a higher refractive index and plastic glasses have disadvantages in this aspect.
- Glasses made of the plastic CR-39 are lighter than conventional mineral glasses, they significantly reduce the weight of glasses and are comparatively thicker. The plastic is unbreakable, but scratches faster than glass. This can be remedied to a certain extent by special lacquer hardening, which the health insurance companies do not pay for.
- Polycarbonate is a particularly light, highly refractive plastic that can be processed thinly and is extremely break-proof. That is why polycarbonate is particularly suitable for the production of spectacle lenses for children's and sports glasses. The disadvantages mentioned are that disruptive color scattering can occur and that the surface is sensitive to scratches, and even a seal cannot guarantee optimal scratch resistance.
The size of the lenses is primarily determined by the frame. Diameters of around 23 to 35 millimeters are sufficient for children; in adults they can also be significantly larger, especially with multifocal lenses.
The smaller the lenses, the lower their weight and the overall weight of the glasses becomes lighter. If larger blanks than required are used to manufacture plus lenses, the thickness and weight of the later lenses increases unnecessarily. With all glasses, the thickness, material and surface geometry also have an influence on the weight.
Tints reduce the incidence of light and can therefore worsen visual acuity. Therefore, they are only useful in certain situations with increased light exposure or with increased sensitivity to glare . They can be equipped with a special feature so that they automatically change their degree of tint depending on the current light conditions (self-tinting, phototropic ) . Because of the slow response time, they are only partially suitable for driving.
Anti-reflective coatings reduce annoying light reflections on the spectacle lens by means of an anti-reflective coating and ensure more pleasant vision without annoying mirror images, especially under artificial lighting conditions. Depending on the degree of anti-reflection effect, different degrees of anti-reflection can be used: single, multiple or “super anti-reflection”. They are used in combination with mineral and plastic glasses. Anti-reflective coatings are ideal for driving at night, for example, because of the possible glare from oncoming vehicles.
A hard layer increases the resistance of the surface of plastic glasses to scratches and wear. This coating is either vapor-deposited - here, quite brittle silicon dioxide is usually used - or applied as a flexible paint in an immersion bath. However, the hard layer does not provide increased protection against breaking the glasses.
Special requirements are placed on the frame of prescription glasses in terms of material and appearance. Optimal glasses are light and flexible, but also very stable and durable. It sits well and tightly without pressing and meets the requirements for its design and shape.
In the 21st century the range of spectacle frames is very diverse, such as full-rim frames , supporting rim frames , Rimfassungen or rimless frames. They are available in a wide variety of sizes, shapes, materials, colors and their combinations. Historical versions such as lorgnon , monocle or pince-nez are rarely used.
The material of the frame is an important criterion for compatibility and durability, and some glasses are even named after them, for example horn-rimmed glasses or nickel-plated glasses . Different metals and metal alloys , for example nickel silver , spring bronze , stainless steel , titanium or gold , as well as plastics such as cellulose acetate or various injection molding materials are usually used . In addition, more and more exotic materials are being used, such as wood, hemp, leather or composite materials made from various raw materials such as recycled jeans and old books.
If allergic reactions occur when wearing or if allergies to certain substances are known beforehand, this must be counteracted by a suitable choice of material or special coatings. Manufacturers offer a range of solutions here. Particularly flexible and durable frames, which can be bent almost at will without any problems and which spring back to their original shape automatically due to the material properties, are made from a combination of titanium and steel.
The size of the frame depends on the size of the face, the size of the eye socket ( orbit ) and the existing eye relief . The outer boundaries should end upwards under the eyebrows and still leave them visible, which is important for the facial expression. At the bottom they are in the border area between the skin of the eyelids and the cheekbones , without resting on the cheekbones. To the side, they reach no more than the edge of the temples . The smaller the frame is chosen, the lower the associated restrictions. In particular, the occurrence of visual field restrictions in the case of higher myopia and farsightedness can be reduced to a minimum by using a smaller frame and lenses that are close to the eyes. However, it must be large enough to prevent you from looking over it when looking up.
The frame is precisely machined in compliance with strict centering regulations (RAL-RG 915) so that the position of the optical center of the lenses corresponds exactly to the center of the pupil . The center-to-center distance (MA) of the lenses must correspond exactly to the distance between the eyes , i.e. the so-called pupillary distance (PD).
Eyeglass temples establish the connection between the lens holder and the head of the wearer. They have to be long enough not to cause pressure points, but to ensure a secure fit. A plastic cover, the cell end or the end of the temple , is often attached to the metal bracket . Some frames have interchangeable arms with different colors and patterns.
The temples are generally attached to the frame with small hinges. Plastic caps that are pulled over the hinges can reduce the potential for risk of injury here. It is also possible to equip the mostly stiff temples with spring hinges from an opening width of around 90 degrees, which enable movement beyond the right angle and thus ensure more durability and flexibility when putting on and taking off.
Special temples, which reach almost to the earlobe behind the ear and ensure a secure hold with an elastic component, are called webbing, articulated or sports temples and are found on frames for children and sports glasses. A plastic cover on the flexible part that runs behind the ear often helps against possible pressure points or allergic reactions.
Another variant that ensures a secure fit is an elastic rubber band that is attached to two straight, non-curved brackets and runs behind the head. For infants and toddlers, there is the option of working such a fastening into a cap so that the child cannot tear off the glasses.
Nose bridge / pads
The nose carries a large part of the weight of the glasses. In order to avoid slipping or the formation of pressure points, the contact surface of the nose bridge is therefore correspondingly large and usually consists of soft material.
Side bars or nose pads made of different materials offer good individual adaptation to the bridge of the nose . Their brackets can be adjusted to the nasal area by bending them with pliers and hand, but bending can also occur when a sports ball hits the ground or as a result of accidents. Side bars and especially the nose pads are wearing parts and can sometimes be replaced if necessary.
In children, the bridge of the nose is not yet fully developed ( epicanthus ). In order to take this anatomical fact into account, there are special saddle bars or loop bars made of plastic that have a larger contact surface and evenly distribute the weight. In addition, they can be shaped and adapted within certain limits by the optician.
Any initial treatment with glasses should be preceded by an ophthalmological examination. For an adult, first aid can also be carried out by an optician if there are no other symptoms.
Children and young people
The prescription of glasses in infancy or childhood almost always has a medical - therapeutic background. Higher grade ametropia such as farsightedness , nearsightedness or astuteness can impair the normal development of vision in early childhood and must be corrected in good time with appropriate glasses. Otherwise there is a risk of irreversible impaired vision ( amblyopia ), which later can not be cured even with optimal glasses or contact lens correction.
Another criterion for the immediate provision of glasses is an impending or already existing strabismus . Here, the risk of amblyopia is even higher due to not using the cross-eyed eye (suppression) . Even with fully developed visual acuity , this risk persists until the beginning of puberty. In addition, in some cases the glasses can influence the position of the eyes and thus the two-eyed vision , which is why correction is necessary as early as possible. In certain cases, spectacle lenses have a prismatic effect that changes the path of the light through the spectacle lens. This property can be achieved by working a prism directly into a glass or by sticking it to the glass using a film that can be removed at any time.
Adults need glasses for the same reasons as children, namely to achieve better visual acuity, to correct a squint position or to eliminate asthenopic symptoms. In contrast to children, however, no serious damage remains if a necessary correction should not be worn. The requirement to wear glasses also arises from other aspects. In certain situations, for example, wearing glasses is required by law, for example when using machines or driving a motor vehicle. 62 percent of all drivers need glasses, but only 34 percent use them all the time.
Wearing glasses at work can also be subject to certain guidelines. Employees who usually use a display device for a not insignificant part of their normal work are subject to EC Directive 90/270 / EEC of May 29, 1990 on minimum requirements for safety and health protection when working with display devices. In Germany, several EC directives, including EC Directive 90/270 / EEC, based on the authorization under Occupational Safety and Health Act, the Federal Government issued an ordinance on safety and health protection when working with display devices (BildScharbV) of December 4, 1996. The employer can request an ophthalmological report on the suitability for working on display devices, which may document whether it is mandatory to wear display workstation glasses.
Other aspects of eyeglass correction
Functional and therapeutic importance of glasses
In principle, glasses only fulfill their function when they are worn. If it is stopped, its effect is no longer available. However, glasses that are used to correct ametropia have no influence on their extent and do not objectively improve them. Conversely, ametropia does not worsen if you do not wear glasses. The changes that the eyes are exposed to over the years will therefore take place regardless of whether the necessary glasses are worn or not.
The elimination of complaints and poor visual acuity that exist without glasses can only be achieved with the use of an appropriate correction. In addition, in some cases of farsightedness ( hyperopia ), an accommodation spasm can occur if a necessary correction is not used.
The eyes are subject to certain changes. Regular checks are required, especially with children's glasses, for two reasons. On the one hand, intensive use often bends the frame or scratches the lenses. Since an optimal fit and the best possible image quality are essential, corresponding controls cannot be avoided. On the other hand, the development and growth of children change the optical refraction of the eyes. This leads to the fact that the once determined glass thickness no longer corresponds to the current requirements after a certain period of time and has to be adjusted. The time intervals at which this happens are individually different and are related to other findings. Unless the ophthalmologist recommends otherwise, a check-up is necessary six to eight weeks after the initial prescription to ensure that the medical and functional expectations have been met. Further checks are to be carried out at regular intervals by arrangement. If there is amblyopia or strabismus, eyeglass controls can be carried out as part of the ophthalmological examinations. Otherwise, regular visits to an optician are recommended to check glasses and visual acuity. If it is found that the eyes have changed significantly, a new lens determination should be carried out by an ophthalmologist, again using eye drops if necessary.
For adults, we recommend checking the glass thickness every two to three years, earlier in the case of subjective complaints or deterioration in visual acuity.
Glasses can certainly cause problems. This may be the case if the ametropia to be corrected is very high and the lenses must be correspondingly strong. In addition to the weight problem of the glasses, which can now be minimized with suitable materials and manufacturing processes, there are in many cases incompatibilities with regard to the image size on the retina, the pillow distortions and visual field restrictions with tall plus glasses (example: star glasses ), prismatic side effects when decentering and generally glass zones different image quality. Likewise, very different refractive ratios of the right and left eyes ( anisometropia ) can only be corrected satisfactorily to a certain extent with spectacle lenses. The reason for these difficulties lies not least in the distance between the lenses and the eye. Therefore, contact lenses may be preferable to glasses in the appropriate cases .
Wearing glasses is not associated with an increased risk of injury, not even with children's glasses. On the other hand, glasses can prevent serious injuries to the eye. Nonetheless, external influences such as fist blows, bruises , bruises and / or a glasses hematoma can occur, which can also occur independently of wearing glasses.
There are alternatives to correcting ametropia with corrective glasses. One of them is the adaptation of contact lenses , which, however, has to meet certain requirements, for example with regard to tolerance. In Germany, the costs for this are only covered by the statutory health insurance companies in medically justified exceptional cases. In addition to the greater freedom of movement and the cosmetic aspect, a clear advantage over eyeglass corrections is the possibility of being able to correct very high ametropia satisfactorily with very few optical and functional side effects.
Another alternative is to perform refractive surgery ; H. operative interventions on the eye to reduce existing refractive errors. Such operations are not without some risk; In addition, there are restrictions with regard to the dosability, resulting in over- or under-corrections. Long-term studies are not yet available. The costs must be borne by the patient himself. Such a treatment can, however, offer itself in the case of very severe ametropia, in which neither glasses nor contact lenses are sensible or possible.
Health insurance costs and benefits
The services provided by statutory health insurance companies are regulated in guidelines for aids. This does not generally affect the possibility of taking out private supplementary insurance such as glasses insurance, which can offer different services and conditions.
Although visual aids are listed in the list of medical aids provided by the statutory health insurance (GKV), only children and young people are entitled to reimbursement of costs within the framework of various flat-rate fixed amounts. Severely visually impaired people are an exception . When the HHVG came into force on April 11, 2017, it was stipulated that in future the costs of "glasses with a refractive power of at least 6 diopters" and "astigmatism of at least 4 diopters" for adults will be covered by health insurance companies ( (2) sentence 2 SGB V )
The end consumer prices of glasses are generally based on quality and features, but are also subject to a clear price policy by companies due to increased competition . There are certain standards that can be implemented with less financial outlay, whereas complex processing or special materials result in higher costs. The costs for anti-reflective coatings and tints, for example, usually have to be borne by the customers themselves. The statutory health insurance (GKV) in Germany differentiates between lenses and frames when it comes to costs. She does not cover the costs for the frame, those for glasses up to the age of 18 at the latest only within the framework of a flat rate based on the age of the child and the glass thickness. If it is not a first-time supply, but a re- prescription, you are only entitled to reimbursement of costs after the age of 14 if the glass thickness has changed by at least 0.5 diopters compared to the last prescription. Repair costs are covered by the health insurance companies.
For a time, the cost of plastic glasses was only borne by preschoolers. With a resolution of October 16, 2008, however, the Federal Joint Committee , the highest body of joint self-administration in the German health care system , revised the Medical Aids Directive for a generally better supply of visual aids at the expense of the statutory health insurance. In the resolution, on the one hand, the exclusion of trifocal glasses , varifocals and high refractive lenses was largely abolished and adjusted to market requirements. In addition, plastic glasses can be prescribed beyond preschool age for minor ametropia.
In Switzerland, the costs for spectacle lenses were covered by the mandatory health insurance until 2010 in the amount of a fixed unit amount . After the Swiss Federal Office of Public Health (BAG) canceled the assumption of costs with the entry into force of the Means and Items List (MiGeL) on January 1, 2011, spectacles and contact lenses will again be available from July 2012 for patients up to the age of 18 at an annual rate of CHF 180.00 . This rule is initially valid until December 31, 2013.
In Austria glasses fall under the so-called therapeutic aids . Co-payments for glasses are covered in a certain amount by the regional health insurance funds (GKK) if these are higher than 60% of the maximum contribution basis for the calendar day. In 2018, the minimum cost contribution for the insured is 102.60 euros and for children over 15 years 34.20 euros. There are no co-payments for children up to the age of 15. Trifocal and varifocal glasses are not allowed to be paid for by the statutory health insurance.
Glasses for special areas of use
Sunglasses are light protection goggles and are used to protect the eyes from the effects of excessively bright sunlight and reflections , as well as harmful UV rays and are therefore usually only worn outdoors. The glasses have different degrees of light transmission (tint), which in certain cases can automatically adapt to the respective brightness conditions (phototropic) . Filter tints of 25%, 50%, 65%, 75%, 80% and 85%, as well as gradient tints that are dark at the top and light at the bottom, are common. Such light protection glasses can also be attached to and removed from "normal" glasses from the front by means of a special construction.
Sunglasses are not suitable for safely observing the high, dazzling sun. The use of solar eclipse glasses is necessary for this.
Another possibility of absorbing light reflections from a wide variety of surfaces (for example water surfaces or glass panes) is provided by polarization films . This makes use of the fact that light reflected on dielectric surfaces is strongly linearly polarized. The foils are usually stuck between two thin carrier layers and ensure that light glare is no longer attenuated, but rather eliminated by reducing it to the polarization direction perpendicular to that of the reflected light (see wave optics ). In another process (infusion molding) , special polymers are incorporated into the lenses for this purpose .
The UV protection is determined worldwide by different norms and guidelines, in Germany by the norm DIN EN 1836.
In particular in appropriately arranged environments, for example in high mountains, it is absolutely advisable to wear light protection goggles ( snow goggles ) to protect against significant health impairments such as flashing or snow blindness. There are also illnesses that are associated with an increased sensitivity to light and glare and can therefore make it necessary to regularly wear light protection goggles even in closed rooms. This includes, for example, albinism .
Computer workstation glasses
With normal varifocals, the mean distance (in this case the screen) can only be read in a very narrow area. This is why the lenses in the workplace glasses have a particularly wide central area. These glasses are not suitable for everyday use (e.g. when driving a car) because the distance range is unfavorably high. So they are just a second pair of glasses for the workplace. It is mainly necessary for people who constantly sit in front of monitors. The lenses are also called degressive lenses or varifocal lenses for close-up work .
A make-up glasses is a specially designed Korrektionsbrille for short range obtained by individually foldable glasses with hyperopia, or presbyopia ensures a sharp vision, while allowing unimpeded makeup of that eye, the correction lens is folded down (more rarely above). With normal glasses, the fixed glasses would hinder access to the desired eye area, without them the visual acuity would be significantly restricted. The lens strengths of make-up glasses should roughly correspond to those of the individual close-up correction.
Safety glasses are used in different areas of life and are intended to protect the eyes from injuries and harmful effects such as chemicals , radiation , flashing , flying sparks or foreign bodies. Depending on the area of application, protective goggles can be equipped with refractive effects (corrective protective goggles) and are subject to certain functional and qualitative requirements, some of which are determined by defined quality criteria and standards. In addition to the European standard EN 166 in Germany, the principles contained in BGR 192 (professional association rules for safety and health at work) stipulate the equipment and properties of protective goggles in the work environment.
In the military sector, there are various protection classes according to which the properties of protective goggles are defined, and which are specified, for example, in the common ANSI standard of the United States or the NATO standard STANAG .
The protective goggles also include various sports goggles , for example swimming goggles , cycling goggles , motorcycle goggles or the goggles that are worn with sharp weapons in academic fencing. Skydiving goggles have to withstand high airspeeds, are made up of four sheets of connected plastic film, can be folded flat and offer an unrestricted wide field of vision.
The Occupational Safety and Health are closely to tight fitting goggles that protect the eye from the Into vertebrae of particles and also offer protection against the cold for the covered eye region in the face. Visors that fold down in front of the face protect the entire face from splashes of chemicals, liquid iron or infectious material. Glasses coated with reflective (with gold) selectively reflect heat radiation from liquid iron at the blast furnace or during casting . Welding safety goggles with clear glass and rubber-padded aluminum sheet shells with oriented ventilation slots protect against welding spatter, and dark glasses that can also be folded down reduce the brightness of the incandescent gas during gas fusion welding . Welding shields were once hand-held, but are now quickly controlled by brightness; they darken as soon as the welding arc ignites so that they can be worn on a headband.
With the development of small, powerful LEDs , glasses, possibly with a magnifying glass, with 1–2 LEDs in front of the nose bridge and power supply via cable and Li- ion battery on clothing have proven successful for dentists .
With the controversial raster glasses , a protective effect is not the focus.
The diving mask is part of the diving equipment and belongs to the basic equipment of a diver . It is colloquially often as diving glasses or goggles referred to what is wrong in terms of form. The diving mask covers the nose with a nasal cavity, which enables pressure equalization during the dive . Without this pressure equalization, there is a risk of barotrauma when diving .
The human eye is adapted to the optical density of air (1.00). If the surrounding water is in direct contact with the eye, the rays are only slightly refracted here (corresponding to the small difference in optical density) and no longer meet at the focal point on the retina - the diver sees blurred. Only strong accommodation makes distant things clearly visible. The air space within a diving mask enables visual acuity underwater that corresponds to that on land. However, due to the refractive index of 1.33 of water , objects appear at an approximately 4: 3 larger angle, i.e. larger or closer.
A diving mask consists of a soft rubber or silicone body in which a flat lens is inserted at the front. There are models with a single lens and those with a lens in front of each eye. An adjustable elastic band holds the diving mask on the head.
Swimming goggles are sports goggles that prevent water from washing around your eyes. This prevents eye irritation caused by chlorinated swimming pool water , for example . Seeing underwater is also more comfortable. Swimming goggles are only partially suitable for snorkeling because the panes of the two eyes are at an angle to each other. This makes it difficult to fixate an object underwater with both eyes. In contrast to the diving mask, there is no pressure equalization, which is why it is not suitable for diving.
Glasses with temples or straps cannot be worn if a full face mask is to be used, as the holding devices cause leaks in the sealing frame of the mask. For this reason, special mask goggles are used in which the glasses are held by a frame that is inserted directly into the respirator.
Shooting glasses are special correction glasses that are only used in shooting sports with firearms. They have some special features compared to normal glasses and are also permitted as eye protection.
Glasses with special optical properties
There are a number of other types of glasses, the shape and texture of which can vary greatly depending on their functionality. In addition to medical, technical and scientific fields of application, entertainment electronics are also gaining in importance.
A magnifying loupe is a combination of prescription glasses and magnifying glass . It is used in medicine and technology for activities at close range that require an enlarged representation. It also serves as a magnifying visual aid in the case of corresponding diseases of the eye. This also includes cataract glasses , which were previously prescribed as a correction and replacement for the removed lens after the surgical removal of a cloudy eye lens , the cataract . The high weight, as well as the visual and cosmetic side effects, however, were a considerable disadvantage, so that such corrections are now only used in special exceptional cases.
Good magnifying glasses have a large field of vision, which enables a sharp image right into the edge zone, free of color distortions . These features can only be achieved with high quality optical systems . The glasses themselves can already have a corresponding thickness, or magnifying glass attachments are attached to the conventional spectacle lenses.
Prism glasses are usually used for diagnostic or therapeutic purposes in the case of latent or manifest strabismus . In principle, they are not corrective lenses, but are combined with them. The rays of light falling into the eye are deflected in the direction of the eye malposition and thus reduce the occurrence of double images, especially in the case of eye muscle paralysis . Their application usually represents a massive intervention in the motor and sensory functions of the two- eye vision and should therefore only be carried out under the supervision of an ophthalmologist. Corrective lenses without a prismatic effect are also an essential part of the strabismus treatment and can have a considerable influence on the position of the eyes.
Prism lenses are also used in experimental investigations of optical perception in inverted glasses . Deflection prisms are also increasingly being used in the private sector , for example in the form of safety glasses for sport climbing .
A special medical application is the examination of nystagmus , which is carried out with Frenzel glasses , named after the Göttingen otologist Hermann Frenzel (1895–1967). They are luminous glasses with highly refractive lenses of +15.00 dioptres and enable precise observation of eye movements , while lighting shining in from below switches off any possibility of fixation for the subject.
3D glasses are based on the principle of image separation and should make a two-dimensional, flat image appear three-dimensional. Using different methods, the right and left eyes are each presented with their own image, which usually triggers a spatial visual impression . In ophthalmology , it is also used to carry out special binocular vision examinations. The 3D glasses include, for example, polarization , red-green or shutter glasses .
Video glasses are constructions that do not have glasses or other openings for looking through, but instead provide visual information using two very small monitors . Their areas of application are, for example, experimental areas, medicine , the military and, above all, the entertainment industry . Special glasses for creating a virtual reality are also referred to as virtual reality glasses (short: VR glasses). Augmented reality glasses are also known as data glasses or smart glasses . Subforms of this are the EyeTap , the virtual retinal display (also light field display) and special glasses for displaying virtual holograms such as the Microsoft HoloLens . Video glasses, which are used to transmit an image from the first person view , are also called FPV glasses . They are used, for example, in the control of RC vehicles and aircraft (see also: FPV Racing ). Although the shape of video glasses is more like a headset with a display, they are often referred to as glasses in everyday language.
Lenses with adjustable focal length
In 2008 Joshua D. Silver developed liquid-filled glasses with adjustable focal length for use in developing countries , the function of which is based on the deformation of transparent plastic membranes.
Manufacturers, retailers and sources of supply
The French company Essilor with its Varilux brand is the world's largest manufacturer of eyeglass lenses, followed by the German Carl Zeiss Vision , a subsidiary of Carl Zeiss . The Rodenstock company is a major manufacturer of spectacle frames and lenses in Germany.
The sale of the prescription glasses is mostly carried out by opticians' specialist workshops with trained staff. The often high prices there are offset by qualified advice and services that are required for optimal adjustment and handling of glasses. There are now ready-made glasses , industrially produced corrections of simple equipment and quality, which are available in bulk goods in department stores or other sales outlets and are only intended to serve as an inexpensive replacement or emergency solution or as simple reading aids. With the spread of the Internet , online shops have recently become established that offer single and multifocal lenses as well as frames from well-known brands and manufacturers, sometimes at significantly lower prices than many specialist shops, and have triggered strong competition in terms of product quality and price-performance ratio . The disadvantage here, too, is the lack of necessary, quality-assured advice and other services, such as measuring the required glass thickness, checking the size of the glasses for correct and comfortable fit, etc. Internet providers are also not allowed to advertise with the term "optician quality".
Nevertheless, in the early 1980s, among other things, new branch chains, by turning away from the previously fixed price structures and through massive competition, ensured a significant cost reduction, which since then has brought the sometimes drastic profit margins of opticians under considerable pressure. Since then, the retail sector has been responding time and again with temporarily cheap offers or special promotions.
Correctionless sports and other special glasses of any kind are usually available from the appropriate specialist retailer or specialist provider.
Glasses care, disposal and recycling
The care of spectacle lenses, frames and other components usually results from their materials, whereby aggressive cleaning solutions or chemical components should be avoided because of the increased sensitivity of the surfaces. Glasses should be cleaned with damp or dry glasses cleaning cloths , in the case of coarse soiling or deposits, if necessary in an ultrasonic cleaning device .
Glasses that are no longer worn can be disposed of with household waste, as the materials used contain hardly any environmentally harmful substances. Alternatively, they can be given to an optician, who forwards them as a donation , for example . Many national and international aid organizations have initiated corresponding projects to enable better care for poor and needy sections of the population around the world. The "Eyewear Worldwide" campaign, sponsored by the German Catholic Association for the Blind, has been offering collection boxes since February 2018, which can be set up in eyewear shops in order to simplify the handing over of old glasses and to encourage the willingness to donate glasses. The Central Association of Opticians (ZVA) supports the setting up of the collection boxes.
Social and cultural significance
The social and economic aspect of glasses as an aid to increasing productivity and performance was discussed early on. The philosopher René Descartes (1596–1650) had already remarked:
"Our entire way of life depends on our senses, and because the sense of sight is the most comprehensive and noble of them, there is no doubt that all the inventions that enhance one's performance are among the most useful ones that can be imagined."
The glasses are one of those key inventions that established Europe's later superiority as early as the Middle Ages. In his book Prosperity and Poverty of Nations , the economic historian David S. Landes points out that the invention of glasses more than doubled the working life in professions where a good eye is important. This was important, for example, for scribes and editors, instrument and tool makers, weavers and metal workers. A doubling of the working life in specialized technical occupations corresponded to a doubling of the skilled workers, whereby the gain was actually even greater because of the greater experience of the older skilled workers. In addition, glasses also enabled the manufacture of more precise tools - the basis for the development of complicated machines and technical progress. According to Landes, Europe had a monopoly on lens manufacturing for almost 400 years.
Early on, people have begun to one aspect of the ornament and the purely functional properties of an optical aid ornamentation add. Since the glasses had to be worn in a very prominent place, they should at least look beautiful and sometimes also valuable. As a fashion accessory, glasses have now become an integral part of the personal appearance of many people. This goes so far that even glasses without any corrective effect are only worn because of their eye-catching and decorative frames. This often applies to sun and light protection glasses.
For many prominent personalities, glasses are not just a means to an end, but they have shaped their appearance and appearance in public to a considerable extent, have become their trademark or at least ensure a certain recognition value . Almost all areas of public life such as politics, society, the music, film and fashion industries have produced well-known glasses wearers. They include Elton John , Buddy Holly , Ray Charles , Heino , Manfred Maurenbrecher , Karl Lagerfeld , Groucho Marx , Woody Allen , the 14th Dalai Lama Tendzin Gyatsho and Gandhi .
Even reputable institutions encourage this development. In Germany, for example, the Good Seeing Board of Trustees has regularly chosen the glasses wearer of the year since 2000 to recognize well-known personalities for their role model function in terms of glasses.
In some cases, glasses are still seen as a sign of intelligence and intellectuality , in both a positive and a negative sense. These prejudices probably originate from a time when only economically better off could afford glasses. They had the financial means for higher education. In the 1970s, for example, in Cambodia, this led to people wearing glasses being persecuted under the rule of the Khmer Rouge as supposedly intellectuals and thus potential enemies of the communist peasant state, and in many cases killed. Glasses (especially horn-rimmed glasses) are also often associated with the stereotype and cliché of a bookworm , computer freak , nerd or geek , which is reinforced, among other things, by their representation in film and television. In a retro wave , similar horn-rimmed glasses were initially called mockingly as nerd glasses, but a short time later they were also offered in stores under this name and received even greater popularity and attention.
Furthermore, glasses appear as a symbol for a certain point of view, which is also reflected in linguistic usage. The rose-colored glasses stand for an idealizing and sometimes unreal assessment, as is typical for dreamers and romantics . A completely different example from literature is the figure Beckmann from Wolfgang Borchert's Outside the Door , whose gas mask goggles are actually an urgently needed aid, but repeatedly cause aversions and are considered to be a symbol for a perception of the world determined by war experiences.
Glasses, like other objects, can have a sexual attraction and become sexual fetishism ( glasses fetishism ). In anime and manga , female characters who gain sexual attractiveness by wearing glasses are also referred to as Meganekko . The compound is made up of the words megane and ko . Megane (メ ガ ネ, also め が ね or 眼鏡) is the Japanese word for glasses and ko (娘) the name for an unmarried woman or a girl. They are often introverted otakus who are very intelligent. The character types are usually divided into the roles of shy and cute as well as strict and self-confident. The male equivalent is known as Megane or Meganedanshi.
Museums and exhibitions in Europe
- In its permanent exhibition, the German Optical Museum in Jena presents not only the variety of optical instruments but also the development of visual aids and glasses. The museum has one of the most extensive collections of glasses in Europe. Numerous exhibits, in conjunction with graphics and other source material, provide a comprehensive insight into the history of visual aids.
- In Hamburg , optician and collector Karl-Heinz Wilke runs an eyewear museum. He is a member of the "Ophthalmic Antiques International Collectors' Club of London" and opened his first glasses museum in 1990 in Pöselsdorf.
- In Villach , Carinthia , in 50 years of collecting activity, master optician Alfred Plessin created the exhibition time travel in 2018 , with visual aids and glasses from 260 years.
- In the French town of Morez , which is known for its optical industry, an extensive glasses museum is operated in a specially built building.
- In the small Italian town of Pieve di Cadore there is an eyewear museum , the basis of which is a collection of 1,600 glasses from Brussels .
- The special exhibition Living with Spare Parts 2005 at the Deutsches Museum in Munich also covered glasses.
- Theodor Axenfeld, Hans Pau: Textbook and Atlas of Ophthalmology. With the collaboration of R. Sachsenweger u. a. Gustav Fischer Verlag, Stuttgart 1980, ISBN 3-437-00255-4 .
- Klaus Bergdolt : The invention and spread of glasses in the late Middle Ages. In: Medical History Journal. Volume 29, 1994, pp. 111-120.
- Franz Daxecker , Annamarie Broucek: A representation of St. Ottilie with reading stones. In: Gesnerus. Volume 52, 1995, pp. 119-122.
- Franz Daxecker : Representations of eyeglasses on Gothic winged altars in Austria. In: Documenta Ophthalmologica. Volume 93, 1997, pp. 169-188.
- Susanne Buck: The sharpened eye. A cultural history of glasses since 1850. Dissertation Philipps-Universität Marburg 2002. Anabas, Frankfurt 2006, ISBN 3-87038-347-X .
- Ulrich Faure (Ed.): The author's glasses. Anthology (28 well-known authors with excerpts from their works). Axel Dielmann, Frankfurt 1997, ISBN 3-929232-30-8 .
- Pamela F. Gallin (Ed.): Pediatric Ophthalmology. Thieme, New York 2000, ISBN 0-86577-768-3 .
- Herbert Kaufmann (Ed.): Strabismus. With the collaboration of W. de Decker u. a., 3rd revised edition. Georg Thieme, 2003, ISBN 3-13-129723-9 .
- Kerstin Kruschinski, Petra Waldminghaus: attitude towards life glasses. DOZ-Verlag, Heidelberg 2014, ISBN 978-3-942873-27-7 .
- Bernhard Lachenmayr, Dieter Friedburg, Erwin Hartmann, Annemarie Buser: Eye - glasses - refraction: Schober course: understand - learn - apply. 4th edition. Georg Thieme, Stuttgart 2006, ISBN 3-13-139554-0 .
- Heinz Herbert Mann: Eye glasses and perspective. Studies on the iconography of two image motifs (= studies on profane iconography. Volume 1). Gebr. Mann, Berlin 1992, ISBN 3-7861-1570-2 .
- Sabine Walter, Henry Hagenfall: The glasses in the film. Epubli.de, Berlin 2014, ISBN 978-3-7375-2229-8 . Book about the symbolism of glasses in film.
- Stefana Sabin: Moments. A cultural history of glasses. Göttingen 2019.
- antiquespectacles.com: Antique Spectacles & Other Vision Aids
- monumente-online.de: The cultural history of glasses
- brillenmuseum.eu: glasses history with sample photos
- nafuo.din.de: NA 027 Precision Mechanics and Optics Standards Committee (NAFuO)
- augeninfo.de: guidelines, correction of refraction errors ( memento from October 19, 2010 in the Internet Archive ), Federal Association of Ophthalmologists in Germany (BVA), German Ophthalmological Society (DOG)
- See.de , Board of Trustees for Good Vision (KGS)
- g-ba.de: Press release on improving the supply services for glasses , Federal Joint Committee, October 16, 2008
- Kindergesundheit-info.de: Recognize visual disturbances and risks at an early stage , Federal Center for Health Education (BZgA)
- For the history of glasses and visual and reading aids, Spektrum.de: How did glasses get on your nose?
- current list of GKV aids
- Direct health insurance companies - Statutory catalog of benefits
- Klaus Bergdolt : Glasses. In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 210.
- Karl-Heinz Ludwig, Volker Schmidtchen: Propylaea history of technology. Metals and Power 1000–1600 . Unchanged new edition. Berlin 1997, ISBN 3-549-05633-8 , p. 23.
- Origin of the word glasses . In: etymologie.info
- Friedrich Kluge , Alfred Götze : Etymological dictionary of the German language . 20th edition, ed. by Walther Mitzka , De Gruyter, Berlin / New York 1967; Reprint (“21st unchanged edition”) ibid 1975, ISBN 3-11-005709-3 , p. 101.
- HE Schmitz: Handbook on the history of optics I: From antiquity to Newton. Bonn 1981, pp. 69-71
- Heinz Herbert Mann: Eye glasses and perspective. Studies on the iconography of two motifs. (= Studies on Profane Iconography. Volume 1). Gebr. Mann, Berlin 1992, p. 26 f.
- Alfred Wiedemann: The ancient Egypt . In: W. Foy (Ed.): Kulturgeschichtliche Bibliothek (= 1st row: Ethnological library ). tape 2 . C. Winters, Heidelberg 1920, p. 412 ( Internet Archive ).
- Pliny the Elder: Natural History. Retrieved April 27, 2008 .
- Wilhelm Grimm (ed.): Konrads von Würzburg Goldene Schmiede . Berlin 1840, p. 54, lines 1800-1805.
- Art. Glasses. In: Lexikon des Mittelalters, Volume 2, Col. 692, here: Col. 690.
- Klaus Bergdolt: The visual curtain as a theological analogue: Eye anatomy and physiology with Roger Bacon. In: Sudhoff's archive. Volume 75, 1991, pp. 1-20.
- Wolfgang Münchow: History of ophthalmology. Stuttgart 1984, pp. 175-177.
- Klaus Bergdolt: Medical in the Mainfränkisches Museum zu Würzburg. In: Würzburg medical history reports. Volume 8, 1990, pp. 41-52; here: p. 41 f.
- Klaus Bergdolt: Glasses. 2005, p. 210.
- Willem F. Daems, Mientje Daems, Gundolf Keil: Euphrasia. Contributions to the medieval pharmacology of eyebright and strawberry. In: Würzburg medical history reports. Volume 14, Würzburg 1996, , p. 253.
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