​A brief history of glasses: What did the ancients do if they were nearsighted?

Zhao Xigu of the Southern Song Dynasty wrote in his Dongtian Qinglu: "The old man cannot read finely, so he can see clearly by covering his eyes with a pair of glasses." This means that wearing glasses can improve vision and assist in reading. Zhang Zilie of the Ming Dynasty wrote in Zhengzitong: "The glasses are also glasses."

In the ancients’ concept, “the essence of the five internal organs and six bowels are all poured into the eyes as the essence”. The eyes are the place where the essence of the internal organs is poured, and they are particularly important. There are words such as “eyes do not lose sight” and “blindness” in oracle bone inscriptions. Mencius and others in the pre-Qin period also talked about vision problems, which shows that the ancients had been troubled by vision for a long time.

The earliest record of lenses can be found in the "Kaogongji" of Qi State during the Spring and Autumn Period. The book records the method of using gold and tin as a mirror with the concave side facing the sun to make fire. It can be seen that lenses were not used for "seeing things" at that time. However, in the "Fifteen Volumes of Mozi" during the Warring States Period, it was recorded that Mozi conducted systematic research on plane mirrors, concave mirrors, convex mirrors, etc., and derived a series of basic principles of geometric optics. Zhang Heng discovered the waxing and waning of the moon and the preliminary causes of lunar and solar eclipses in the early Eastern Han Dynasty, also with the help of lenses.

In 1980, a crystal convex mirror was unearthed from the tomb of Liu Jing in Zengquan Mountain, Yangzhou. It is 1.3 cm in diameter, round, and embedded in a ring-shaped gold ring. This small and exquisite gold ring is embedded with a crystal lens, which can magnify objects 5 times. The tomb owner Liu Jing was the son of Emperor Guangwu of the Eastern Han Dynasty, Liu Xiu, and lived in the early Eastern Han Dynasty.

In the scroll of "Nandu Bustling Scenery" painted by Qiu Ying in the Ming Dynasty, an old man in front of a gold shop can be seen wearing glasses on his nose. In the Wanli period of the Ming Dynasty, Tian Yiheng wrote in "Liuqing Daily Notes": "Every time I read an article, my eyesight becomes dull and I cannot distinguish the details. I cover my eyes with this, so that my spirit is not scattered and my strokes are clear. I tie it with silk and tie it behind my head. No one knows it, so they show it to me. I say: This is 叆叇." 叆叇 originally means "clouds covering the sun", which describes a layer of fog covering the eyes. It is very vivid, and the pronunciation "爱戴" makes it even more vivid. Obviously, at this time, 叆叇 already had silk tied behind the head to replace the "mirror feet". In addition to 叆叇, the ancients also called glasses "僾眼眼", "書石", "单照", "眼环", etc. The price of glasses in the Ming Dynasty was "only the mirror is expensive, the price is as high as a horse". In the Qing Dynasty, the price dropped. "The most expensive pair was worth no more than 7 or 8 cents of silver, and even 4 or 5 cents, or 2 or 3 cents per pair."

At the end of the 13th century, "The Travels of Marco Polo" recorded: "Old Chinese people wear glasses to read small print." After Marco Polo returned home, glasses appeared in Italy. However, Zhao Yi of the Qing Dynasty said in "Yu Yu Cong Kao": "There were no glasses in ancient times. They only appeared in the Ming Dynasty and originally came from the West." Qianlong also wrote in a poem: "Glasses are not ancient, but come from foreign ships." Where glasses came from is not to be explored in detail.
With the advancement of science and technology and the development of the glass industry, the lens material has gradually replaced the original natural crystal with glass. In 1954, French engineers invented resin lenses, which are light and thin, provide clearer vision, and make the lens material safer and healthier.

The development of glasses is also reflected in the improvement and clinical application of lens surface coating technology. The coating has evolved from the initial wear-resistant film (also known as hard film) to the single-layer anti-reflection film, and gradually developed into a composite film composed of wear-resistant film, multi-layer anti-reflection film, and hydrophobic film (also known as anti-fouling film). It can visually reduce reflection and glare, block ultraviolet rays, etc., and also improve the durability of the lens and make the appearance of the glasses more beautiful. Now, glasses are no longer just a tool for correcting vision. Certain glasses also have decorative and protective functions.

Bai Juyi: "Thousands of snowflakes are scattered in the sky, and a layer of gauze covers the hazy objects. Even if it is sunny, you can still see things, and you can see flowers even if it is not spring." Han Yu: "I am not yet forty years old, but my vision is vague." Ouyang Xiu: "Myopia makes it very difficult to read books, so I just let people read and listen." The three great writers were all myopic. This has a lot to do with the progress of the imperial examination system, papermaking, printing technology, etc. during the Tang and Song dynasties, and the increasing number of printed books. It is reported that Su Dongpo, Wang Yangming, Ji Xiaolan, Kangxi, etc. were all myopic.

I have been nearsighted since junior high school. In recent years, I have been wearing myopia glasses, but I cannot see things clearly within 15 cm. I have also developed hyperopia. I am both nearsighted and farsighted. I have always believed that people with myopia will not suffer from hyperopia. Who would have thought that I share the same problem with the famous Benjamin Franklin? In 1784, because he suffered from myopia and hyperopia, he combined two pairs of lenses into dual-focus lenses and invented glasses for both nearsightedness and farsightedness. Such glasses are also available today, and wearing a pair kills two birds with one stone.