The earliest historical reference to magnification dates back to ancient Egyptian hieroglyphs in the 5th century BC, which depict "simple glass meniscal lenses". The earliest written record of magnification dates back to the 1st century AD, when Seneca the Younger, a tutor of Emperor Nero of Rome, wrote: "Letters, however small and indistinct, are seen enlarged and more clearly through a globe or glass filled with water". Nero (reigned 54–68 AD) is also said to have watched the gladiatorial games using an emerald as a corrective lens. Corrective lenses were said to be used by Abbas Ibn Firnas in the 9th century, who had devised a way to produce very clear glass. These glasses could be shaped and polished into round rocks used for viewing and were known as reading stones. The earliest evidence of "a magnifying device, a convex lens forming a magnified image," dates back to the Book of Optics published by Alhazen in 1021. Its translation into Latin from Arabic in the 12th century was instrumental to the invention of eyeglasses in 13th century Italy. Englishman Robert Grosseteste's treatise De iride ("On the Rainbow"), written between 1220 and 1235, mentions using optics to "read the smallest letters at incredible distances". A few years later, Roger Bacon is also known to have written on the magnifying properties of lenses in 1262. Reportedly, spectacles were in use in China by the rich and elderly at the time of Marco Polo's arrival in 1270 or 1271, although the Chinese credit their invention to Arabia in the 11th century. Sunglasses, in the form of flat panes of smoky quartz, protected the eyes from glare and were used in China in the 12th century or possibly earlier. However, they did not offer any corrective benefits and the use by historians of the term "sunglasses" is anachronistic before the twentieth century. Many theories abound for who should be credited for the invention of traditional eyeglasses. Despite evidence of spectacles in China in 1270, and Chinese claims of themselves importing spectacle technology from the Middle East in the 11th century, some people theorise that spectacles were first invented between 1280 and 1300 in Italy. Some also theorise that the first European inventor of spectacles was Salvino D'Armate. In 1676, Francesco Redi, a professor of medicine at the University of Pisa, wrote that he possessed a 1289 manuscript whose author complains that he would be unable to read or write were it not for the recent invention of glasses. He also produced a record of a sermon given in 1305, in which the speaker, a Dominican friar named Fra Giordano da Rivalto, remarked that glasses had been invented less than twenty years previously, and that he had met the inventor. Based on this evidence, Redi credited another Dominican friar, Fra Alessandro da Spina of Pisa, with the re-invention of glasses after their original inventor kept them a secret, a claim contained in da Spina's obituary record. However, Spina most likely learned to make spectacles after seeing them made by another individual, a talent for which he was known at the time. Another potential inventor is Salvino D'Armate, who is credited with inventing the first wearable eye glasses on 16 September 1284 in Italy. In a 1684 history of Florence, Leopoldo del Migliore wrote that the church of Santa Maria Maggiore contained a memorial honoring D'Armati with the inscription: Here lies Salvino degl' Armati, son of Armato of Florence, inventor of eyeglasses. The church has been rebuilt several times since the 13th century, however, and this tomb no longer exists, so the claim cannot be verified. Seated apostle holding lenses in position for reading. Detail from Death of the Virgin, by the Master of Heiligenkreuz, ca. 1400–30 (Getty Center). The earliest pictorial evidence for the use of eyeglasses is Tommaso da Modena's 1352 portrait of the cardinal Hugh de Provence reading in a scriptorium. Another early example would be a depiction of eyeglasses found north of the Alps in an altarpiece of the church of Bad Wildungen, Germany, in 1403. These early spectacles had convex lenses that could correct both hyperopia (farsightedness), and the presbyopia that commonly develops as a symptom of aging. Nicholas of Cusa is believed to have discovered the benefits of concave lens in the treatment of myopia (nearsightedness). However, it was not until 1604 that Johannes Kepler published in his treatise on optics and astronomy, the first correct explanation as to why convex and concave lenses could correct presbyopia and myopia. The American scientist Benjamin Franklin, who suffered from both myopia and presbyopia, adopted bifocals in 1784 to avoid having to regularly switch between two pairs of glasses although the claim that he actually invented them is disputed. The first lenses for correcting astigmatism were constructed by the British astronomer George Airy in 1825. Over time, the construction of spectacle frames also evolved. Early eyepieces were designed to be either held in place by hand or by exerting pressure on the nose (pince-nez). Girolamo Savonarola suggested that eyepieces could be held in place by a ribbon passed over the wearer's head, this in turn secured by the weight of a hat. The modern style of glasses, held by temples passing over the ears, was developed some time before 1727, possibly by the British optician Edward Scarlett. These designs were not immediately successful, however, and various styles with attached handles such as "scissors-glasses" and lorgnettes were also fashionable from the second half of the 18th century and into the early 19th century. In the early 20th century, Moritz von Rohr at Zeiss (with the assistance of H. Boegehold and A. Sonnefeld), developed the Zeiss Punktal spherical point-focus lenses that dominated the eyeglass lens field for many years. Despite the increasing popularity of contact lenses and laser corrective eye surgery, glasses remain very common, as their technology has improved. For instance, it is now possible to purchase frames made of special memory metal alloys that return to their correct shape after being bent. Other frames have spring-loaded hinges. Either of these designs offers dramatically better ability to withstand the stresses of daily wear and the occasional accident. Modern frames are also often made from strong, light-weight materials such as titanium alloys, which were not available in the earlier times.
