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History, economics, business, politics…and Sussex

Eyeglasses (aka ‘glasses’ or ‘spectacles’) have a long and interesting history. It is said[2] that almost 2,000 years ago, the Roman philosopher Seneca[3] peered at his book through a glass of water. Suddenly, the text below was transformed; the words magically became clear. But it wasn’t until much later that that same principle would be used to create the earliest eyeglasses.

The earliest known examples of eyeglasses were created in the 13th century in Italy. These early eyeglasses were made of lenses held in place by a frame that rested on the bridge of the nose and extended to the temples. They were made to correct vision problems such as hyperopia (farsightedness) and presbyopia (age-related difficulty focusing on close objects). The concept of eyeglasses as we know them today, with a frame holding lenses in place and worn on the face, did not develop until that time.

However, it is possible that the use of lenses to correct vision dates back to ancient civilisations in Mesopotamia, Egypt, and Greece. There is some evidence that the ancient Greeks and Romans used lenses made of crystal or quartz to magnify objects and improve vision. These lenses may have been used as reading stones[4] or to help people with vision problems see more clearly. It is also possible that the use of eyeglasses was developed independently in different parts of the world at other times. There is evidence that glasses were used in ancient China and that the Inuit people of the Arctic region used lenses made of ice to help them see better in the snow. Overall, it is likely that people have been using lenses to improve their vision for thousands of years, but the development of eyeglasses as we know them today is generally credited to the Italians in the 13th century.

A picture containing text, indoor, old

Description automatically generated
The Glasses Apostle by Conrad von Soest (1403)
Attribution: Conrad von Soest

Page URL:,_%27Brillenapostel%27_(1403).jpg

The use of eyeglasses spread throughout Europe in the 14th and 15th centuries, and they became an important tool for scholars and intellectuals who relied on reading and writing as part of their work. In the 16th and 17th centuries, eyeglasses became more widely available and began to be worn by people of all social classes.

During the 18th and 19th centuries, eyeglasses underwent significant changes in design and construction. Lenses were made of more advanced materials such as glass and plastic, and frames were made of materials like metal, tortoiseshell, and celluloid. The first eyeglass frames with hinged temples, which could be folded for storage, were also invented during this time.

Today, eyeglasses are an important tool for correcting vision problems and are worn by people worldwide. They have also become a popular fashion accessory and are available in various styles and colours.

Before 1200 AD, ancient people defined eyesight as “the most wonderful of the five senses“ and devoted detailed studies of the human eye and vision. Although knowing how to enlarge objects with glass spheres filled with water through which they could observe magnified things, ancient Romans, who were familiar with the mechanisms of enlargement and could make glass, did not know how to produce lenses for visual aid.[5]

Here is a timeline of key events in the history of eyeglasses[6]:

  • The 1200s: The earliest known mention of eyeglasses appears in the writings of Italian monk and scholar Giordano da Pisa. He describes the use of glass spheres filled with water as a means of correcting vision.
  • The 1300s: Eyeglasses began to be manufactured in Italy. These early glasses were made of a series of thin, flat plates of glass that were held in place by a ribbon tied around the head.
  • The 1400s: The first eyeglasses with frames made of wood or bone appeared.
  • The 1500s: The first eyeglasses with frames made of metal were developed. These frames were made of a single piece of wire or a thin strip of metal that was bent to fit around the ears.
  • The 1600s: Eyeglasses with frames made of tortoiseshell or other materials became popular. The first eyeglasses with adjustable nose pads are also developed.
  • The 1700s: The first eyeglasses with hinged frames were developed. These frames allow the glasses to be folded when not in use.
  • The 1800s: The first eyeglasses with frames made of celluloid, a type of plastic, were developed.
  • The 1900s: Eyeglasses with frames made of metal and plastic became popular. The first contact lenses were also developed.
  • The 2000s: Eyeglasses with frames made of various materials, including metal, plastic, and composite materials, became widely available. The development of laser eye surgery and other vision correction procedures also became more common.

Image Credit:William Wordsworth’s eyeglasses” by betsythedevine is licensed under CC BY-NC-SA 2.0.

The Discovery of Glass[7]
Early eyeglasses used glass, dating back to ancient civilisations in Mesopotamia, Egypt, and the eastern Mediterranean. The first known use of glass was not for eyeglasses in the form of beads, which were made by the ancient Egyptians around 2500 BC. These beads were made by melting silica (silicon dioxide), a common component of sand, with other materials such as soda and lime. The process of making glass by heating silica with other materials was later developed by the ancient Romans, who used it to make objects such as cups, plates, and vases.

There is evidence that ancient civilisations in Afghanistan, such as the Bactrian civilisation, may have made glass. However, the ancient Egyptians and Romans are generally credited with developing the process of making glass by melting silica with other materials, which was a significant innovation in the history of glass making.

The ancient Egyptians and Romans made various glass objects, such as beads, cups, plates, and vases. Glassmaking technology continued to evolve over the centuries, with the ancient Romans being particularly skilled at producing high-quality glassware. Glassmaking spread to other parts of the world, with evidence of glass production in China, India, and the Islamic world.

It’s possible that other civilisations, such as those in Afghanistan, also made glass using different techniques and other materials. The history of glass is long and varied, and it has been made and used by many different cultures around the world. Some say the Phoenicians were the first to exploit the potential of the hard, transparent material we call glass. Turkey’s Ministry of Culture and Tourism says: ‘The discovery of how to make glass was probably made in the Bronze Age towards the end of the third millennium BC’.[8]

Archaeological excavations have unearthed trinkets made from obsidian, a black volcanic glass used long ago to adorn weapons, ornaments, and even coins. Archaeological evidence suggests that the discovery took place in Mesopotamia and, in all probability, occurred as the result of the use there of vitreous glazes and faience-for beads, tiles, pottery and other articles.[9]

Image Credit: Light being refracted by a spherical glass container full of water. Roger Bacon, 13th century
Attribution: Optics from Roger Bacon’s De multiplicatone specierum.jpg
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Reading Stones
The first vision aid, called a reading stone, was invented around 1000 AD[10] and is an approximately hemispherical lens that can be placed on top of text to magnify the letters so that people with presbyopia can read them more easily. Reading stones were among the earliest common uses of lenses.


Image Credit: Reading stone in Archeon, a historical theme park
Attribution: Ziko van Dijk, CC BY-SA 4.0 <;, via Wikimedia Commons.
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The invention of reading stones is often credited to Abbas ibn Firnas in the 9th century[11], although their regular use only began around 1000 AD.[12]  Early reading stones were made from rock crystal (quartz) or beryl, as well as glass, which could be shaped and polished into stones used for viewing. The Swedish Visby lenses, dating from the 11th or 12th century, may have been reading stones.

Venetian glass blowers in the 13th century are known to have produced reading stones made of solid glass that were put into hand-held, single lens-type frames made of horn or wood. These reading stones were similar to the hand-held magnifying lenses of today.

Eyeglasses and their use today[13]
Eyeglasses are vision eyewear, with lenses (clear or tinted) mounted in a frame to hold them in front of a person’s eyes, typically using a bridge over the nose and hinged arms (known as temples or temple pieces) that rest over the ears. Typically they are used for vision correction, such as with reading glasses and glasses used for nearsightedness; however, without the specialised lenses, sometimes they are used purely for fashion or aesthetic purposes. Other uses include:

  • Safety glasses provide eye protection against flying debris for construction workers or lab technicians; these glasses may have protection for the sides of the eyes as well as in the lenses. Some types of safety glasses are used to protect against visible and near-visible light or radiation.
  • Glasses are worn for eye protection in some sports, such as squash. Wearers may use a strap to prevent the glasses from falling off. Wearers of glasses that are used only part of the time may have the glasses attached to a cord around their neck to prevent the loss of the glasses and breaking. The loss of glasses would be detrimental to those working (or, in the case of sports, playing) in these conditions.
  • Sunglasses allow for better vision in bright daylight and may protect one’s eyes against damage from excessive levels of ultraviolet light. Typical sunglasses lenses are tinted for protection against bright light or polarised to remove glare; photochromic glasses are blacked out or lightly tinted in dark or indoor conditions but turn into sunglasses when they come in contact with ultraviolet light. Most over-the-counter sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be made.
  • People with conditions that have photophobia as a primary symptom (like certain migraine disorders or Irlen syndrome) often wear sunglasses or precision-tinted glasses, even indoors and at night.
  • Eyeglasses that filter out blue light from computers, smartphones and tablets are becoming increasingly popular in response to concerns about problems caused by blue light overexposure. The problems claimed range from dry eyes to eye strain, sleep cycle disruption, to macular degeneration, which can cause partial blindness. However, there is no measurable ultraviolet radiation from computer monitors. Long hours of computer use may cause eye strain, not blue light.[14]
  • Other specialised glasses may be used for viewing specific visual information, for example, 3D glasses for 3D films (stereoscopy)[15]. Even with glasses used for vision correction, many fashions are available, using plastic, metal, wire, and other materials for frames.

A painting of a person writing on a piece of paper

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Image Credit: The first known artistic representation of eyeglasses, painted by Tommaso da Modena in 1352.)
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Early Contributors to the field of Optics
The 13th century Italian monk and scholar Giordano da Pisa (also known as Jordanus de Nemore or Jordanus Nemorarius) wrote about the use of glass spheres filled with water as a means of correcting vision. According to historical accounts, Giordano was a member of the Dominican Order and a professor of mathematics at the University of Paris. One of his most significant contributions to optics was his work on the use of glass spheres filled with water as a means of correcting vision. In his writings, he described how such a device could be used to correct vision by bending the rays of light entering the eye to bring them into focus on the retina. This idea was later developed into the concept of “eyeglasses” – a pair of lenses worn in front of the eyes to correct vision.

A person with a beard

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Image Credit: Salvino D’Armati. Attribution: See page for author, CC BY 4.0 <;, via Wikimedia Commons.
Page URL: History – Information about Spectacles

However, the use of eyeglasses to correct vision is generally attributed to a later Italian scholar, Salvino D’Armate, who has been credited with inventing the first eyeglasses in the late 13th or early 14th century. Giordano’s contributions to the field of optics were important and influential in the development of eyeglasses and other vision-correction devices, but it is likely that he was not the first person to propose using glasses to correct vision.

The Oldest Eyeglasses
The oldest known pair of eyeglasses was found in the ruins of the Daisenin Temple in Kyoto, Japan. The eyeglasses were discovered in the early 20th century and are thought to date back to the late 13th or early 14th century. They consist of two small lenses set in a frame made of wood or bone (or ivory) and were likely used to correct vision problems such as farsightedness (also known as long-sightedness, hypermetropia, or hyperopia) or presbyopia (age-related difficulty focusing on close objects). The eyeglasses are now housed in the Kyoto National Museum. They belonged to Yoshimasa Ashikaga, the eighth shogun of the Muromachi shogunate.

Eyeglasses of the type found in Japan were used throughout the Middle Ages and Renaissance and became more widespread in the 17th and 18th centuries as the technology for making lenses improved.

Eyecare as a Profession
Optometry is a specialised healthcare profession involving examining eyes and related structures for defects or abnormalities. Optometrists provide comprehensive primary eye care:

  • In the United States and Canada, optometrists are those that hold a Doctor of Optometry degree. They are trained and licensed to practice medicine for eye-related conditions, in addition to providing refractive (optical) eye care.
  • In the United Kingdom, optometrists may also practice medicine (and provide refractive care) for eye-related conditions. The Doctor of Optometry title can also be used in the UK for those with a postgraduate O.D. degree.

Comparing optometrists, ophthalmic opticians and other eye specialists [16]

  • Optometrists are eye doctors trained to examine the eyes for vision problems and diagnose and treat various eye conditions. They typically have a Doctor of Optometry (OD) degree and are licensed to practice optometry, which includes prescribing glasses, contact lenses, and medications to treat eye diseases.
  • Ophthalmic opticians are eye care professionals who are trained to dispense and fit eyeglasses, contact lenses, and other vision aids. They may also be involved in providing basic eye care services, such as measuring patients’ visual acuity and testing their eyes for visual defects. Ophthalmic opticians may work in optometry or ophthalmology practices, or in a retail setting.
  • Other eye specialists include:
  • Ophthalmologists are medical doctors specialising in the diagnosis and treatment of eye diseases and conditions. They are trained to perform eye surgery and may also prescribe eyeglasses, contact lenses, and medications to treat eye problems, including glaucoma, cataracts, and retinal disorders.
  • Opticians are eye care professionals trained to dispense and fit eyeglasses and contact lenses, but they do not have the medical training or license to diagnose or treat eye diseases. They may also dispense eyewear and provide basic eye care services.
  • Orthoptists are professionals who specialise in diagnosing and treating disorders of the eye muscles and visual system, including amblyopia (lazy eye) and strabismus (crossed eyes). They work closely with ophthalmologists and optometrists to manage these conditions.
  • Paediatric ophthalmologists are ophthalmologists who specialise in the diagnosis and treatment of eye conditions in children. They are trained to recognise and manage conditions that are specific to children, such as strabismus and amblyopia.
  • Ocularists are professionals who specialise in the design, fitting, and maintenance of artificial eyes (also known as prosthetic eyes). They work closely with ophthalmologists and other eye care professionals to provide the best possible care for patients who have lost an eye due to injury or disease.

Text, letter Description automatically generated
Image Credit: Page 423 from “A treatise on the eye, the manner and phaenomena of vision” by William Porterfield, Published 1759 in Edinburgh. In this book, the word “optometer” appears for the first time.
Attribution: William Porterfield(Lifetime: ca. 1696–1771), Public domain, via Wikimedia Commons
Page URL:,_A_treatise_on_the_eye_(1759).jpg

It’s important to remember that these different types of eye care professionals have different levels of training and expertise and may have different roles and responsibilities in the treatment of eye conditions. Anyone with an eye problem or concern must see the appropriate eye care professional for a proper diagnosis and treatment plan.

The ‘Father of Modern Optometry’
Irvin M. Borish
Irving M. Borish (1913 – 2012) was an American optometrist considered “The Father of Modern Optometry“,[17] although others may justly lay claim to that title. Certainly, he is widely respected as one of the leading figures in the history of optometry. He was a pioneer in the field of vision science and is known for his:

  • contribution to the development of optometric education, research, and clinical practice;
  • development of the Borish Balance Chart, which is used to assess visual acuity.

Even though he entered the field of optometry because his family could only afford to pay for two years of college, he left a lasting impression in the eyecare field. Borish received his Doctor of Optometry degree from the Illinois College of Optometry in 1938. He went on to have a long and distinguished career in optometry, serving as the Dean of the College of Optometry at the University of California, Berkeley, and later as the President of the American Optometric Association. His contribution to optometry has been recognised through prestigious awards and recognition from his peers.

Borish was a prolific writer and researcher, publishing numerous articles and books on various aspects of optometry and vision science. He wrote one of the most renowned textbooks of optometry, Clinical Refraction. Borish is known for his contributions to the development of new diagnostic and treatment techniques in optometry and for his efforts to promote the importance of vision care and eye health, lobbying tirelessly to establish optometry as a mainstream medical practice.

William Horatio Bates
Another claimant to the title, The “Father of Modern Optometry”, is William Horatio Bates, an American ophthalmologist who developed a method of improving vision without using eyeglasses or other optical aids.

Bates (1860 – 1931) received his medical degree from the New York Homeopathic Medical College in 1885. He practised as an ophthalmologist in New York City for many years and became interested in the idea of improving vision through eye exercises and other techniques. His treatment method, which he called the “Bates Method (or System)”, involved a series of exercises designed to improve visual acuity, eye coordination, and other aspects of vision. These exercises included palming (covering the eyes with the palms of the hands), sunning (looking at the sun or other bright light sources), and swinging (moving the eyes back and forth).

Bates’s ideas about eye care and vision improvement were controversial and were largely dismissed by the mainstream medical community. However, his methods continue to be influential today, and many people continue to use the Bates Method to improve their vision.

Something odd happened to Bates around August 1902. He disappeared, claiming he was on a business trip of some importance, leaving his bereft wife (Aida Seaman) at their marital home in New York City. Mysteriously, he reappeared some while later but claimed no knowledge or recognition of his wife.[18]

In 1952, optometry professor Elwin Marg wrote of Bates, “Most of his claims and almost all of his theories have been considered false by practically all visual scientists.”[19] Despite the controversy surrounding his ideas and life, Bates is recognised as an important figure in the history of optometry and vision science.

Several other individuals have made significant contributions to the optometry field and are considered important figures in the profession’s history. Some who might be regarded as “fathers” of modern optometry include:

  • Hermann von Helmholtz was a German scientist and physician who made important contributions to the understanding of the eye and vision. He is known for his work on the physiology of the eye and for developing the first scientific theory of colour vision.
  • Leonard J. Press was an American optometrist known for his contributions to the field of vision therapy and his work on developing the press-on bifocal lens.
  • Benjamin Franklin is best known as a statesman and inventor, but he also made significant contributions to understanding the eye and vision. He is credited with the invention of bifocal glasses and is also known for his work on the principles of refraction.

The theoretical basis for the invention of eyeglasses had existed well before their invention. For instance, in 1268, Roger Bacon penned how the appropriate use of different kinds of lenses could be used to enlarge letters.

British Eye Specialists in History
There have been many British eye specialists who have made significant contributions to the field of ophthalmology. Some notable figures include:

  • John Jonston (or Johnston) (1603 – 1675) was a Scottish physician and naturalist who made important contributions to the understanding of the eye and vision. He wrote several influential books on the subject and is considered one of the founders of modern ophthalmology.
  • Sir William MacKenzie (1887 – 1963) was a Scottish ophthalmologist who made significant contributions to the understanding of the anatomy and physiology of the eye. He is best known for his work on glaucoma, a condition in which the pressure within the eye increases and can lead to vision loss. In addition to his work on glaucoma, MacKenzie also made important contributions to the understanding of other eye conditions, including cataracts and retinal detachment. He was a pioneer in the use of intracapsular cataract extraction, a surgical technique for removing cataracts, and developed new methods for the treatment of retinal detachment.
  • Sir Stewart Duke-Elder (1894 – 1978) was a British ophthalmologist considered one of the pioneers of modern ophthalmology. He made significant contributions to understanding the anatomy and physiology of the eye and authored numerous books on the subject, including the widely-respected System of Ophthalmology, which covers virtually every aspect of ophthalmology and is considered an essential reference for eye care professionals.
  • Sir Harold Ridley (1906- 2001) was a British ophthalmologist credited with developing the first successful intraocular lens (IOL) for cataract surgery. The IOL is a small, artificial lens that is implanted in the eye to replace the cloudy natural lens that is removed during cataract surgery. Before the development of the IOL, cataract surgery involved removing the natural lens and leaving the eye without a lens, which often resulted in significant vision loss. Using the IOL revolutionised the treatment of cataracts and has helped millions of people regain their vision.
  • Sir Peng Tee Khaw (1954 -), a Chinese-Malaysian British Consultant Ophthalmic Surgeon at Moorfields Eye Hospital in London, is a world-renowned expert on glaucoma and has made significant contributions to the understanding of the disease and its treatment. He has also made important contributions to the development of new treatments for other eye conditions, including age-related macular degeneration and retinopathy. He originally studied medicine at the University of Cambridge, where he later became a professor of ophthalmology. He has received numerous awards and honours for his contributions to ophthalmology and has served as President of the Royal College of Ophthalmologists.

Image Credit: A Normal Range of Vision
Attribution: National Eye Institute, National Institutes of Health, Public domain, via Wikimedia Commons
Page URL:,_normal_vision.jpg

Image Credit: The same view with Advanced Vision Loss from Glaucoma
Attribution: National Eye Institute, National Institutes of Health, Public domain, via Wikimedia Commons
Page URL:,_glaucoma.jpg

Concluding Words
According to experts, eyeglasses are the fifth most important invention since humans discovered fire and invented the wheel. The reason: when eyeglasses were created, for the first time, millions of people could enjoy good vision despite problems with their sight. Today we take this for granted, but for centuries there was simply no solution for those with a visual impairment – glasses still had to be invented. It took a long time to develop the modern eyeglasses or spectacles we know today[20]:

“The first wearable glasses known to history appeared in Italy during the 13th century. Perhaps the most famous of these more modern glasses include “Martin’s Margins” – spectacles developed by the inventor Benjamin Martin (1704-1782), [a former Chichester-based schoolteacher]. Today, glasses [from that and earlier eras] are sold as collector’s items, but they pioneered the pursuit for more accurate lens development and thinner lenses supported by durable frames.”
Source: and

“Eyeglasses had a huge impact on society and the economy as the printing press and books became popular, the demand for eyeglasses grew, therefore, increasing the amount of money paid for the glasses. Glasses became common amongst people, especially those who could read, usually the upper class, scholars, and monks. Because eyeglasses were invented with the basis of magnification, the telescope and microscopes were invented in a similar way.”

“There is no evidence of women using early pairs of glasses. [In the beginning] Because lenses at the time were used to magnify rather than to clarify, most of the glasses produced were for farsighted individuals so they could read. Since women were not permitted to be literate during this time, they had no societal need for glasses. Even after women became more literate, glasses were so expensive that only religious scholars, political leaders, or other wealthy individuals used them.”

“In Venice, they knew that rock crystal, when shaped into strongly convex shapes, helped vision while reading, and these “Lapides ad Legendum“ i.e. “stones for reading“, are acknowledged in the Capitulary which governed the Guild of “Crystal Craftsmen“: these were used as magnifying lenses and were simply placed over the object itself. Furthermore, these craftsmen also made crystal discs which were called “Roidi da Boticelis“, i.e. glass plugs that were used to close jars containing precious ointments. The scholar Luigi Zecchin deduced that by putting the eyes near one of the discs, all objects became clearly visible. In any case, in 1284, the “roidi da ogli“, “round glass for the eyes“, are present in the list of routine production items. It is at this stage and right here in Venice that we can say that the invention of eyeglasses takes place, i.e. when lenses are properly mounted and placed before the eyes: the history of making glass lenses leads to the history of eyeglasses.”

“Nicholas of Cusa (also known as Nicholas of Kues or Nicholas of Cues, was a 15th century German philosopher, theologian, and cardinal of the Catholic Church) is credited with discovering how to correct myopia (nearsightedness) with concave lenses. This meant that by the 1400s, Italy was making lenses in different strengths for myopia, hyperopia and presbyopia. By the 15th century, there were peddlers throughout Europe selling eyeglasses which had become a sign of wealth and intelligence. By the 1600s, glasses were being made with ribbons attached or strings so they could go over the ears. The notion of wearing glasses for extended periods led to the invention of weights being added by the Chinese instead of a loop used – leading to Edward Scarlett (an 18th century British clergyman and classics scholar) making rigid temples to go over the ears in 1730. Finally, by 1752, James Ayscough created a doubled hinged earpiece and added a green and blue tint to the lenses to reduce glare.”

“Louis de Wecker (1832-1906) was a famous French ophthalmologist [although born in Germany] and was considered one of the greatest ophthalmologists of his time with a worldwide reputation. He introduced many innovative surgical techniques such as his method for iridotomy, “anterior sclerotomy,” and the so-called “de Wecker’s capsular advancement” for the treatment of strabismus[21]. He also invented surgical instruments such as “de Wecker’s pince-ciseaux” and “de Wecker’s double advancement hook”.”

“The term optician has existed for centuries. It was first mentioned in the so-called ‘Banner Ordinance’ in June 1467.”

Sources and Further Reading


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Boy testing eye site
Image Credit: “Boy testing eye site” by sfloptometry is licensed under CC BY-SA 2.0.

End Notes and Explanations

  1. Source: The machine-generated answer given to questions to the request– ‘Tell me about Eye-Glasses since Ancient Times’, and supplementary questions at
  2. Source:
  3. Explanation: Seneca was a Roman tragedian who lived between 4 BC and 65 AD. Reportedly, he used a glass globe full of water to magnify the text in his books. Decades later, there is evidence that Roman glassblowers were commissioned to make different types of glass spheres that could be used on text to make it larger and clearer to read. Monks traditionally used these glass spheres in the Middle Ages to read religious texts more easily. Source:
  4. Explanation (as provided in a machine-generated answer by Reading Stones were small, mainly flat stones that were used in the medieval period to help people read manuscripts more easily. They were usually made of a smooth, polished material such as marble, and were used as a makeshift bookmark or a page holder. The person reading the manuscript would place the reading stone on the page they were reading, and then use their finger to trace the lines of text, making it easier to follow the words and keep their place in the text. Reading stones were popular because they were portable and could be easily carried in a pocket or bag, making them useful tools for scholars and readers on the go. It’s not clear exactly when reading stones came into use, but they were likely used as early as the 13th century and may have remained in use until the advent of printed books in the 15th century.
  5. Source:
  6. Source: Information provided, in response to a question about the timeline of eyeglasses, by Artificial Intelligence at:
  7. Source: Information provided, in response to a question about the discovery and manufacture of glass, by Artificial Intelligence at:
  8. Source:
  9. Source:
  10. Source:
  11. Source:
  12. Sources: (1) Rubin, Melvin L. (1986). “Spectacles: Past, present, and future”. Survey of Ophthalmology. 30 (5): 321–327, and (2) Quercioli, Franco (2011). Alberto Diaspro (ed.). Optical Fluorescence Microscopy: From the Spectral to the Nano Dimension. Springer. p. 2ISBN 978-3-642-42281-2. Cited at:
  13. Source:
  14. Cited at: from sources including: (1) Are Computer Glasses Worth It? by Celia Vimont (27 April 2017), Reviewed by Rahul Khurana, MD, American Academy of Ophthalmology, (2) Blue Light Glasses – Helpful or Just Hype?, WebMD Health News, 16 December 2019, (3) Ultraviolet radiation emitted by lamps, TVs, tablets and computers: are there risks for the population?, vol. 90, no. 4, pp. 595–7, (4) Blue Light and Digital Eye Strain, by Daniel Porter (16 January 2020), Reviewed by Ninel Z Gregori, MD, American Academy of Ophthalmology, (5) Do blue light glasses work?, by Marisa Iallonardo (24 May 2020), Reviewed by Benjamin Bert, MD, Business Insider, and (6) Should You Use Night Mode to Reduce Blue Light?, by Vered Hazanchuk (7 May 2019), Reviewed by Raj K Maturi, MD, American Academy of Ophthalmology.
  15. Explanation: 3D glasses create the illusion of three dimensions on a two-dimensional surface.
  16. Source: The machine-generated answer given to questions to the request– ‘What’s the difference between optometrists, ophthalmic opticians and other eye specialists?’, and supplementary questions at
  17. Source: Crabb, Carolyn. “The Father of Modern Optometry: Dr Irvin Borish”. MSTech. M&S Technologies. Cited at:
  18. You can read about the bizarre disappearance and reappearance of William Horatio Bates at:
  19. Sources: (1) Chou, Brian (15 September 2004). “Exposing the Secrets of Fringe Eye Care”. Review of Optometry. 141 (9), and (2) Marg, Elwin (April 1952).

    “Flashes of clear vision and negative accommodation with reference to the Bates Method of visual training” (PDF). American Journal of Optometry & Archives of American Academy of Optometry. 29 (4): 167–84. Cited at:

  20. Based on text at:
  21. Explanation: Strabismus (commonly called squint) is a condition in which the eyes are not aligned properly and point in different directions. This can cause double vision and can affect depth perception. Strabismus can be present from birth or can develop later in life. It can be caused by problems with the muscles that control the movement of the eyes or by problems with the nerve pathways that control the muscles. Strabismus can be treated with eyeglasses, eye patches, eye exercises, or surgery. Source and acknowledgement:

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