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What can people with the technology of 9th-10th century use to produce efficient and complex contact lenses with colored symbols on them like enter image description here

the use of machines is obviously excluded, I've seen glass workers that can do some incredibly awesome things by hand like this sculpture but I'm not sure if they could make something like safe and comfortable lenses or how they would color them... Or probably could they use some more comfortable materials at that time instead of glass? cause I imagine glass contact lenses could be bad for health and maybe heavy and painful.

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    $\begingroup$ I am taking a guess here but I think the only good, realistic answer for your question is going to be quite anticlimatic. $\endgroup$ – Renan Aug 25 '16 at 21:54
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    $\begingroup$ Who cares if they're safe? People in medieval times did some pretty unsafe things. $\endgroup$ – DJClayworth Aug 25 '16 at 22:00
  • $\begingroup$ Don't think there were even glasses at that time. (corrective lenses in frames) $\endgroup$ – Seeds Aug 26 '16 at 15:19
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A history lesson!

In 1827, English astronomer Sir John Herschel proposed the idea of making a mold of a person's eyes. Such molds would enable the production of corrective lenses that could conform to the front surface of the eye. But it was more than 50 years later that someone actually produced such lenses, and there is some controversy about who did it first.

Some reports say German glassblower F.A. Muller used Herschel's ideas to create the first known glass contact lens in 1887. Other reports say Swiss physician Adolf E. Fick and Paris optician Edouard Kalt created and fitted the first glass contact lenses to correct vision problems in 1888.

Early glass contact lenses were heavy and covered the entire front surface of the eye, including the "white" of the eye (the sclera). Because these large "scleral" lenses severely reduced the oxygen supply to the cornea, they could be tolerated for only a few hours of wear and failed to gain widespread acceptance.

Source: All About Vision

...So lenses made of actual glass would be made that way. They'd be nasty, and nothing even remotely like the lenses we have today. I would absolutely hate wearing them.

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  • $\begingroup$ could they be made smaller to fit in the pupil and iris only without covering the cornea or it would fall from the eye? $\endgroup$ – Charon Aug 25 '16 at 22:23
  • $\begingroup$ @渡し守シャロン The people of the 1800s couldn't figure out. The first major advancement from what I listed combined glass and plastic. Assuming your medieval society hasn't figured out how to refine crude oil into products yet, they're stuck with at best 1800s technology. Unless you handwave something you can't advance further with actual clear objects you place in your eyes. $\endgroup$ – Nex Terren Aug 25 '16 at 22:25
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There is really no way contacts with designs like this can be reliably made as early as the 9th or 10th century...they would heavily interfere with vision and not be practical for wearing beyond a few minutes.

But no need to be anti-climatic in an answer...lets make this work.

Eyeball Tattoos! http://www.viralnova.com/eyeball-tattoos/ As commented, medieval people were willing to do some pretty unsafe things and this to me ranks right up there. It'd give the intended effect (assuming you intend this to be permanent), along with a level of silly danger that people of the time would likely accept.

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  • $\begingroup$ cool, from what wikipedia says eye tattoos exist by 2000 years already $\endgroup$ – Charon Aug 25 '16 at 22:19
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Seeing as plastics are probably out of the question, I could potentially see an early civilization making something like that out of thinly filleted organic materials such as a semi-solid mucus or gelatinous substance. Using something like thinly sliced fish eggs or a jellyfish carapace could potentially be molded into a corrective lens.

The lenses might come with an elaborate fractal pattern from the organic source or could potentially be dyed before slicing. Forming geometric patterns in that way might be possible, but would be much more difficult.

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  • $\begingroup$ My thoughts exactly. $\endgroup$ – JDługosz Aug 26 '16 at 2:56
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For colouring the lenses, glass workers can join different coloured strands of glass - consider a lot of modern paperweights or coloured wineglass stems. Once you've got your multicoloured lump of glass, you can stretch it out to give you a smaller cross section with finer details - so the initial construction is easier. Then you can cut a couple of slices off and grind/polish to shape. You might also be able to use stained glass painting or pottery style glazing techniques on a plain glass base - I believe both involving applying paint or glaze to the base material and then firing it to fuse it on.

A bigger problem than the technology - which is fairly basic once you have the right glass recipes - is likely to be the science. Measuring what's wrong with someone's eyesight and working out what shape you need to correct it - and developing the tests needed to check what your lens is doing - is likely to be harder. And if you don't have a literate population, then you'll have to find an alternative to reading letters off the test chart.

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  • $\begingroup$ "And if you don't have a literate population, then you'll have to find an alternative to reading letters off the test chart." A Landolt C chart, or an E chart (the former is the letter C in eight orientations, the latter consists of the letter E in four orientations) doesn't require literacy, just knowing left from right. $\endgroup$ – Random832 Aug 27 '16 at 6:27
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What is the purpose / significance of the symbols in the eye? Identification, differentiation?

Where would they get the idea in the first place? Maybe someone born with a genetic mutation? 1. maybe that mutation indicates they're from the ruling family - in this case the poser (person with fake lenses) has the potential of gain.

  1. maybe that mutation is just the most outward indicator of a suite of mutations that includes a superpower - in this case the poser puts himself in potential danger
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