The Eyeglasses ( 13th Century )

Eyeglasses are devices consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person’s eyes, typically using a bridge over the nose and arms which rest over the ears. Glasses are typically used for vision correction.

Image result for eyeglasses
eyeglasses

image source: https://www.lenscrafters.com/lc-us/eyeglasses


Who invented eyeglasses?

Image result for eyeglasses middle age
The first known depiction of a person wearing glasses dates from the end of the thirteenth century.

The invention of eyeglasses is believed to be between 1268 and 1289 in Italy. The earliest eyeglasses had lenses made of natural crystal. These were handheld because they were too heavy to wear on the face. Natural crystal could not be made uniform, so vision with these eyeglasses could still be blurry. Lenses that were made of glass were lighter to wear, but had a tendency to bend light at slightly different angles. This causes a viewer to see a blurry rainbow around the edges of things, also known as “chromatic aberration.” The problem was solved in 1730 by Chester More Hall who used two glass lenses together, one made of “old crown glass” and the other of a newer “flint glass,” to correct the problem. The achromatic lens was a huge step forward for eyeglasses, leading to high demand for glasses from the mid-1700s on.


info source:http://www.museumofvision.org/exhibitions/?key=44&subkey=4&relkey=29

image source: http://cdalebrittain.blogspot.it/2016/07/eyeglasses-in-middle-ages.html

How were glasses made during the Middle Ages?

As James B. Tschen-Emmons notes in Artifacts from Medieval Europe¸ “Bone, wood, or metal were used for frames at first, but in time wire and leather might also house the lenses”. Leather glasses sound amazing.
As time passed, glassmakers became so proficient and knowledgeable about their product that it was possible for the Duke of Milan to order 200 pairs in 1466, all of varying strengths. The Duke specified that he wanted the strength of the lenses to increase based on an average person’s ocular degeneration from ages thirty to seventy in five-year intervals, presumably so that he’d have a new, stronger pair to wear every five years. This means that his glassmaker had the information to create such a variety , which in turn suggests enough glasses were being produced that glassmakers could figure out averages such as lens strength based on age. That’s pretty impressive. While it was probably difficult for the lowest classes to buy glasses – our friend the duke was generous enough to buy glasses for young people with vision problems, too – they had to have been somewhat affordable for them to be as ubiquitous as they seem to have been. The variety of materials with which glasses could be made would have helped make them widely affordable. And stylish. Apparently, medieval hipsters were wearing glasses for fashion’s sake before they became cool.

medieval eyeglasses
Image of medieval glasses

info and image source: http://www.medievalists.net/2016/03/medieval-eyeglasses-wearable-technology-of-the-thirteenth-century/

What is the History of Eyeglasses?

The first image magnification technology was developed between the years 1000 and 1250. Inventors noticed that convex shaped glass had the ability to magnify and the first simple magnifiers, or reading stones, were born. These early magnifying glasses served as a precursor to eyeglasses.
Eyeglasses first appeared in Italy, around the year 1286. They consisted of two framed glass or crystal stones, and were held up to the eyes using a handle. It is unclear who invented these primitive eyeglasses, but their use soon spread throughout Europe.
During this time, Venice, was a Mecca for medieval glass production. The guild of crystal workers was established in 1284. In 1300, they adopted regulations for the manufacture of “discs for the eyes.” This served as a major catalyst for the future of eyeglasses. By the end of the 14th century, thousands of eyeglasses were being exported to all of Europe.
By the mid-1400s, Florence, Italy became a leader in production, sale and innovation of eyeglasses. Glass makers in the area began to create eyeglasses in various strengths for hyperopes, presbyopes, and myopes. A complex grading system was also implemented after the realization that vision slowly declines with age. Eyeglasses were graded with strengths progressing for every five years of age.
Image result for eyeglasses timeline During the 15th century, eyeglasses were in popular demand. Peddlers selling eyeglasses were common on the streets of Western Europe. Demand increased significantly after the appearance of the first newspaper, The London Press, in 1665. The possession of eyeglasses became an indication of intelligence, status, and wealth. This view was shared by the people of Europe, China, Italy, and Spain.
Germany became a major player in the history of eyeglasses during the 17th century. The finest frames were produced here, although the Italians still made the highest quality lenses. During this time period, eyeglasses also became more widely used in the United States. The first optical shop was established in Philadelphia in 1799 by John McAllister, Sr.
Before the War of 1812, McAllister imported all the eyeglasses sold in his optical shop. Due to the trade embargo with Great Britain, he began making his own eyeglass frames in 1815. He and his son John McAllister, Jr., distributed the first astigmatic lenses in the United States. In 1828, they began to import cylindrical lenses which were meant to correct astigmatism.
There were over 300 eyeglass retailers in the United States during the 1820s and 1830s. In light of the success of the McAllisters, eyeglass production developed rapidly. Companies diversified their product lines which resulted in products such as telescopes, binoculars, and microscopes.
At the beginning of the 20th century, eyeglass manufacturers began to emphasize style as well as function. Improved plastics used to make frames in the early 1900s presented new frame styling. By the 1950s, eyeglasses had become a popular fashion accessory in Europe and the United States. Wearers demanded comfortable and stylish designs which displayed elegance while remaining functional. Today, eyeglasses are an accessory that not only improve vision, but also display personality.

info source: http://glassescrafter.com/information/history-of-eyeglasses.html

image source: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj23JuD973VAhUGxxQKHa8KDrYQjRwIBw&url=http%3A%2F%2Fdiscoveryeye.org%2Feyeglasses-timeline%2F&psig=AFQjCNGWVYug45bBtRzib3I_nZvqdnxq_A&ust=1501948152674707

What was the evolution of lens materials over the centuries?

Back when glasses were first invented, all the lenses were made of glass. Fast forward to today, and you’ll find lenses are offered in a variety of materials, with a variety of coatings available.

Knowing the basic differences can aid you when you’re looking around to buy glasses.

  • Glass

    Image result for glass lens
    glass lens

With the advances that have been made in optical technology, few retailers offer glass as a standard any longer. While it served it’s purpose in years past, most other materials tend to be more than ideal. Here are a few notes about glass lenses:

+ Cheap
+ Scratch resistant
+ Resistant to discoloration
+ Resistant to chemicals
– Heavy
– Easy to chip or shatter
– Dangerous when shattered

The real downsides to glass are that it’s heavy, and that it shatters easily and can be dangerous. Dropping a pair of glasses with glass lenses on a solid surface often results in it breaking. Particularly in the case of children playing, glass is the least preferable option – a baseball to the eye can result in a trip to the emergency room followed by surgery to remove shards of glass from the eye. It’s also quite heavy – for those with high prescriptions, glass lenses tend to cause glasses to slide down the nose, or leave stronger impressions from the nosepads.

The only real advantage is it’s scratch-resistance and durability. Anything that doesn’t cause the glass to break usually leaves the glass itself relatively clear and unscathed. It’s when something happens to break the glass that serious problems arise…

  • Plastic (CR39)

    Related image
    plastic lens

CR-39 is the most common material used in glasses today. It’s lighter and less shatter-prone than glass. Here are a few notes about CR-39 (plastic) lenses:

+ Cheap
+ Light
+ Shatter resistant
– Scratches more easily
– Subject to discoloration (chemical or otherwise)

The real up-sides to CR-39 is that are that it’s both light and shatter-resistant. This makes them both easier to wear, and much safer than glass. The largest down-side is that it’s easier to wear – dropping a pair of glasses with CR-39 lenses on the ground probably won’t break them, but it may leave them with a deep gouge or scratch. Anything that tends to cloud plastic can cloud CR-39 lenses over time as well. A well-kept pair of CR-39 glasses will usually last many years, but the lenses typically won’t be in as good of shape as well-kept glass lenses after a long period of time. Since most people tend to replace their glasses every few years, this tends not to be a big deal.

  • Polycarbonate

    Image result for polycarbonate lens
    polycarbonate lens

Polycarbonate’s a space-grade material, and has been used in space shuttles. The characteristics that made it great for space travel tend to make it great for eyewear:

+ Very Light
+ Virtually shatter-proof
+ More scratch-resistant than CR-39
+ Built-in UV protection
– Scratches more easily than glass
– Expensive

Polycarbonate lenses are the best choice for children’s glasses. There have been videos across the internet showing a bullet effectively bouncing off polycarbonate – it’s very very difficult to break and almost impossible to shatter. It has the added benefit of being the lightest material available. It’s less susceptible to scratching than plastic/CR-39 lenses, but it’s not quite as hard as glass and therefore can be scratched. It’s used in most high-quality safety glasses in industrial workplaces. With many pros and very few cons, it’s commonly known as the “best” lens material for any glasses.

info source:https://free-info-pages.com/buying-glasses-difference-between-lens-materials.htm

image source: https://www.fasttech.com/product/1203403-ar-coated-optical-glass-lens

http://budgetlightforum.com/node/24822

https://www.visionease.com/product-solutions/lens-materials/polycarbonate-lenses/

Who invented sunglasses?

The Italians may lay claim to the invention of eyeglasses, but the Inuits and ancient Chinese can take credit for inventing sunglasses. In the 12th century Chinese sunglasses were made from panes of smoky quartz used to dim light streaming in. While Inuits used walrus ivory to to create goggles with small slits to peer through. Sunglasses similar to what we use today can be traced to 18th century English optician James Ayscough, who originally created spectacles with tinted lenses, which he thought could improve vision.

Image result for sunglasses invention
the first sunglasses

info source: https://www.framesdirect.com/landing/a/who-invented-glasses.html?affiliate=73

image source: https://www.lenspick.com/blog/origins-and-history-of-sunglasses/

Leave a Reply