History of lenses

Turning to my physics book to clarify in my head some stuff about vertex distance and compounded lenses… Found this in reference to plus lenses:
“The use of these lenses in spectacles became common after the invention of printing.”

So did early readers realize there was a problem with close work and protect themselves with plus lens therapy where modern folk just push through reading close and ruin their eyes? Perhaps when print became available font sizes suddenly got smaller and people started holding the paper closer and got eye strain?

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Most likely it started as a reactionary thing to blurred vision (due to such things as presbyopia, accommodative lag, and astigmatism at near). Somehow I doubt it began as a protective thing. If it had, you’d think we would be in a very different place today. Then again, I wasn’t around then, so I don’t know.

The protective thing is complicated, too. It does work, but usually the amount of plus (or add) has to be relatively low for it to work well. The same concept applies to a differential correction. If you add too much plus, you can actually increase strain due to having to get even closer to the material (not to mention lens distortion).

I wonder if plus eyeglass lenses came before minus.

Yes, this is specificaly saying plus lenses came first, and implies that most people were farsighted or found print to be too small if they needed plus lenses to read.

Was print smaller then? Paper was still rather expensive for a long time. Schoolchildren used reusable slates rather than paper for school work even into pioneer days.

Maybe only older people read, or close focusing was hard for everyone. The plus lens moved the image to a more comfortable range, perhaps. Or its also possible there was some vanity. And convex lenses were the only kind? All sorts of possibilities.

How could I forget hyperopia? Duh!

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Ah right, so they started treating hyperopia before nearsightedness.