Vision Aids prior to the invention of Eyeglasses
There is a wealth of physical and documentary evidence supporting the availability of lenses for magnification in ancient times: The earliest documentary proof comes from Aristophanes (c 450-c. 385 B.C.) who mentions the use of plano-convex lenses and globes filled with water for magnification in his comedy play “The Clouds”. Among the earliest of examples, the ancient Egyptians had lenses: the Louvre and the Cairo museums contain statues of pharaohs dating back 4600 years whose eyes are made from convex and concave lenses made from very high quality rock crystal.
Some of the manifold examples from early Roman culture may be viewed at first hand in the British Museum or the Louvre: These artefacts clearly demonstrate that artisan glass makers working in Rome in the first century AD produced both convex and concave lenses and mirrors. Moreover, they even developed a type of glass so clear as to resemble rock crystal – a feat the Venetians only emulated in 1300. Documentary evidence from the period supports the hypothesis that such glass must have been widespread in early Roman times. Pliny the Elder (23 – 79 A.D.) described the widespread use of glass and crystal in Roman society as a crazy addiction:
“there was one woman, who was by no means rich, who paid 150,000 sesterces for a single (rock crystal) dipper” [Pliny, Natural History, Vol X].
In 1868 Heinrich Schliemann excavated lenses from the site of the ancient Greek City of Troy which may date from between the 12 – 14th century B.C.
Recent excavations at a Viking site at Gotland Island yielded ten aspherical rock crystal lenses now known as the Visby Lenses. These appear to have been fashioned on a lathe in the eleventh or twelfth centuries and most probably originated in the Byzantine Empire. A treasure trove veritable wonder from the ancient world: while approaching the optical quality of modern lenses, they were made to the exact optimal shape for magnifying lenses a full 500 years before Descartes would calculate the exact specification for this shape – a fact which becomes all the more impressive when one considers that Descartes calculations were made at a time when the available technology could not produce such lenses. It must be therefore reasonable to presume that and some of the lenses made in antiquity must certainly have found application as visual aids for suffers of presbyopia.
Is it possible that glasses have been the most important invention of the last millennium? They might well be because they have effectively doubled the working life of all who need their eyesight to do fine work. It is an irrefutable point that many great achievements in art, academia, literature, science and technology were only made possible by the introduction of corrective spectacles to the world. It has been said that glasses have prevented the world from being ruled by people under forty. Yet, for all that, the true inventor of eyeglasses still remains obscure despite voluminous research and scholarly debate on the issue. Even after years of exhaustive research, the late academic and optical pioneer, Professor Vasco Ronchi summed the situation up well when he said “the world has found lenses on its nose without knowing who to thank”.
Dr. Edward Rosen, fellow researcher of Ronchi, points to circumstantial evidence that the first pair of spectacles was invented around 1286 near Pisa in Italy. These early examples consisted of two glass convex discs enclosed in metal or bone rims with handles centrally connected by a tight rivet. In use they would either have clamped the nostrils or been held before the eyes. The evidence for this claim comes in the form of a scriptured Lenten sermon delivered and recorded at the Dominican Monastery of Santa Maria Novella in Florence in 1306 by the venerable Friar Giordano da Pisa:
“it is not yet twenty years since there was found the art of making eyeglasses, which make for good vision, one of the best arts and the most necessary the world has, And it is so short a time since this new art, never before extant, was discovered… and I saw the one who first discovered and practiced it and I talked to him”
In Friar Giordano’s day, technological innovations were usually made by craftsmen that would endeavour to keep their methods secret so as to exploit the maximum commercial advantage that their invention could yield. This strategy was not without good reason: the first commercial patent would only be issued 165 years later in Venice. The manufacturing process of making glasses did not stay secret for long however as Friar Allessandro della Spina, contemporary colleague of Giordano’s at the same monastery, also knew the inventor, learned to make them and divulged the process for public benefit. This turn of events is recorded in the Ancient Chronicle of the Dominican Monastery of St. Catherine in Pisa shortly after Spina’s death in 1313:
“Friar Alessandro della Spina, a modest and good man, whatever he saw that had been made, he knew how to make it. Eyeglasses having first been made by someone else, who was unwilling to share them, he [Spina] made them and shared them with everyone with a cheerful and willing heart”
It is probably reasonable to surmise that by the time Giordano preached in 1306 a small group of artisans was probably under the instruction of Della Spina who was eager to spread the craft for the good of humanity. By the early fourteenth century the number of mirror and drinking glass makers in Pisa had become so numerous as to require appropriate designation by the Order of Merchants in the city. It is therefore reasonable to assume that these craftsmen were capable of grinding and polishing lenses in Della Spina’s day.
Other academics have argued that the art of making eyeglasses began in Venice but documentary evidence can only prove that manufacturing in Venice as contemporaneous with Pisa. Certainly the city-state of Venice produced the first guild regulations regarding manufacture and sale of spectacles: the Capitolare dell’arte dei cristalleri (Regulations of the art of crystal workers) in the year 1300. This document repeats a provision previously recorded in 1284 which prohibits the manufacturer of objects from clear glass falsified to resemble rock crystal or quartz crystal. The provision extends even further to the prohibition of both the sale of / making commission from the sale of such falsified objects. A list of frequently falsified objects follows and interestingly within that list were:
• roidi de botacelis et da ogli (disks for vials and for eyes) that could be used to correct presbyopia when held before the eyes and
• lapides ad legendum (stones for reading and for magnifying lenses)
This record provides the earliest written distinction between magnifying lenses which had already been in use for centuries by that time and the new invention of eyeglasses. Had the record been dated before 1286 it would have provided irrefutable evidence pointing to Venice as the birthplace of eyeglasses. The following year, in 1301, an additional provision allowed the manufacture and sale of of vitreos ab oculis ad legendum (glasses for eyes and for reading) by anyone subject to an oath binding the seller to label them as spectacles with glass lenses.
While the above regulations give information regarding the manufacture and sale of glasses, they reveal nothing about the shape of the lenses, convex or concave. Since no other evidence exists for concave lenses for correction of myopia until the fifteenth century, we assume that the lenses must have been convex.
The First Appearances of Eyeglasses in Art:
In the Dominican Monastery of San Nicolo in Treviso, the first examples of eyeglasses in Art appear in a series of frescoes by Tomasso da Modena adorning the ceiling of the chapter house of the begun in 1351 and finished the following year. Many luminaries of the Dominican order were depicted. Three personages of note include:
• Cardinal Hugh of St. Cher, the first person ever to be depicted (albeit anachronistically) wearing the earliest type of eyeglasses of the kind described earlier: convex discs enclosed in metal or bone rims with handles centrally connected by a tight rivet.
• Nicolas de Freauville, Cardinal of Rouen, depicted with a magnifying lens.
• Pietri Isnardoda Chiampo of Vicenza, prominent Italian preacher, whose shelf above his desk is depicted holding a concave reading mirror.
It is fascinating to see that these frescoes display the concomitant use of convex lenses and concave mirrors as magnifiers as part of the scholars equipment. It is obvious that Tomaso and the Dominicans were familiar with the use of these tools and would not have wished to convey the impression of novelty in the artistic depictions.
Medieval Optical Theory:
The curious might well ask what (if any) optical theory underpinned the invention of glasses? The answer to that prescient question is that most scholars agree that the discovery was probably made more through accident than design, most probably by a glass maker, since medieval optical theory could not have led to the invention of glasses. This is because medieval optical theory was based upon the invalid premise that the laws of refraction applied only to a single lens or refracting surface and that the seat of vision lay not at the retina, but at the front side of the lenticular crystalline lens of the eye. Rays of light (“vision”) would according to theory be refracted on its posterior side. By such theory, placing a lens before the eye should have caused a double refraction. While corrective lenses seemed to work in practice, they did not make sense in theory. Three centuries would pass before the momentous discovery of the true fundamentals by Johannes Kepler. In this intervening period the evidence shows that eyeglasses were used at first to correct presbyopia and later myopia without any recourse whatsoever to optical theory.
In conclusion, while the use of lenses for magnification is well documented in the ancient world, the existence of spectacles cannot be attested with the same degree of certitude. It has been speculated that glasses were not invented in the great cultures of antiquity (Rome, Greece or Egypt) because few lived into their forties and this in turn meant that few would have suffered from presbyopia. Thus the demand for spectacles to correct this condition was probably small. By contrast, longer life expectancy and the intensely commercial society of late medieval Italy with its developed crystal and glass industry, where merchants and artisans wrote detailed accounts and correspondence known as the mercantesa, combined with the vigorous intellectual life of monasteries and universities ensured the enormous demand for visual aids of all kinds.