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I'm brainstorming a character (human) and I was thinking about how they would correct their vision if they were short/long-sighted. I would assume that the poorer people would just deal with their bad vision for the whole of their lives, but what about the rich? My character is a prince so would have access to anything he wanted. Yet it's set in a medieval-like world. What kind of ways were there to correct vision, if anything?

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    $\begingroup$ & glasses aren't' an option because? $\endgroup$ – Pelinore Mar 24 at 20:43
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    $\begingroup$ They had eye glasses in the Middle Ages. Here is a 14th century picture of the 13th century cardinal Hugues of Saint Cher wearing eye glasses. $\endgroup$ – AlexP Mar 24 at 22:44
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    $\begingroup$ Just be careful: myopia or presbyopia are the cases where the lens produces a good image but not at the retina. The posted answers solve this. However, if the retina itself is a mess, such as in nystigmatic patients, we still don't have good ways of correcting such problems. $\endgroup$ – Carl Witthoft Mar 25 at 14:45
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    $\begingroup$ @John I haven't read the manga, is it different than in the anime where they stick lenses in the gourd? One think Dr Stone (and a lot of people) gets wrong is the idea that everyone had to put up with nearsightedness in old times. The truth is, almost no one had it. Recent research in developing nations shows it comes mostly from school, your eyes don't develop properly when the horizon is a wall a few feet away, instead of miles away. The poor prince in the above story would only have it BECAUSE he was a prince, and had the privilege of education. $\endgroup$ – CaptainSkyfish Mar 25 at 21:50
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    $\begingroup$ @CaptainSkyfish Its more common now, that is very different than saying it never happened. It still effects around 4% of even low tech native populations. There is a both genetic and environmental causes, you will still have many people with eye problems. Don't fall for sensationalist media that likes to find bullshit single causes for complex problems. Many will have it regardless of environment, many people will still have to put with it . Also yes it is the same anime, the gourd is the native solution but the scientist of the story makes glass lens, giving her full range of vision. $\endgroup$ – John Mar 25 at 22:12
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Eye glasses, just as we use today

They had eye glasses in the Middle Ages. Here is a 14th century picture of the 13th century cardinal Hugh of Saint Cher wearing eye glasses:

Cardinal Hugh of Saint Cher (1200-1263), wearing eye glasses

Cardinal Hugh of Saint Cher (1200-1263), wearing eye glasses. Portrait from the monastery of Saint Nicholas, Treviso, 1352. One of the oldest depictions of a person wearing eye glasses. Photograph by Risorto Celebrano, available on Wikimedia under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Medieval eye glasses were of the "pince-nez" type; our more common type with temples which hook on the ears became common in the Renaissance.

By the 14th century eye glasses had become sufficiently common so that, for example, Francesco Petrarca could boast in a letter that he had had no need for eye glasses before the age of 60, showing that he expected the readers to be aware that older people needed eye glasses.

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ᐃᓪᒑᒃ

(ilgaak)

He could wear "glasses" that work by using slits or holes through an opaque material.

Quite feasible given your level of technology is a device called ilgaak, which as you can see, is a pair of slit goggles. Having no way of making clear lenses, the Inuit did the next best thing, which was to make use of the pinhole effect. Ilgaak serve as snow goggles, the narrow slit keeping snow and wind out of the eyes, and help clarify vision by darkening the inner surface and only allowing vision through a very thin opening.

enter image description here

A more conventional device would be the stenopeic glasse, which as you can see, also operate on the pinhole effect. Visual acuity is (slightly) improved and is well within the technological capabilities of your culture.

enter image description here

There is also the best of both worlds, the pinhole spectacle. Inuit design meets Spanish cool in the antojos of Daza de Valdés. His spectacles are composed to two opaque "lenses" with horizontal pinholes drilled through the matrix, all set into a standard spectacles frame. This article describes the effect and uses in more detail.

enter image description here

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    $\begingroup$ @nick012000 --- Those aren't "broken characters". That's the name of the thing. $\endgroup$ – elemtilas Mar 25 at 7:11
  • $\begingroup$ They weren't English characters and didn't seem to be displaying properly for me. If you want to edit it to have the name of the device written with English characters, go ahead. $\endgroup$ – nick012000 Mar 25 at 7:13
  • $\begingroup$ Yeah, could be a display issue. The letters, though obviously not English, worked for me. Edited, but I kept your revision. $\endgroup$ – elemtilas Mar 25 at 7:16
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    $\begingroup$ My impression is that ilgaak are not doing any optical correction and are used to prevent snow blindness. Can you give some reference that shows they allow corrections to vision ? $\endgroup$ – StephenG Mar 25 at 8:16
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    $\begingroup$ I'm pretty short sighted. A quick experiment with a piece of paper and a few holes definitely gives an improvement to my vision, though not enough to correct my sight completely $\endgroup$ – Riddles Mar 25 at 10:16
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He can just use glasses.

Ptolemy (c. 100-170 CE) described the use of convex lenses for magnification. Reading stones were in use in Europe around 1000. Eyeglasses were being made in Northern Italy by around 1290: a sermon in 1306 mentioned it hadn't yet been 20 years since eyeglasses were invented.

Given that glass was in widespread production and use in the Roman Empire, and had been produced by humans for a few thousand years at that point, it's simple to imagine some bright spark fooling around with lenses and realizing that if you took a pair of small ones and mounted them in front of the eyes, you could help people with poor vision. Technologically, all you need is the ability to make clear glass and then grind and polish it into a lens, and skill in fine metalwork to make some sort of frame. There's no particular reason why the Romans couldn't have done it, which means there's no reason why they couldn't be available in a medieval world with similar technology.

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  • $\begingroup$ depending on how portable you you want them, single lens magnifiers have been around since the BC's $\endgroup$ – John Mar 25 at 21:32
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Maybe goggles filled with a liquid. If the refractive index of the liquid was carefully chosen it could compensate for the eye's focal length. This could work because the cornea accounts for approximately two-thirds of the eye's total optical power.

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