I’ve used jeweler’s eye loupes for extensive periods. They’re not terrible to hold in place unless you’re sweaty. If it’s too small it can become hard, but it generally rests in your eye well and is held in with friction rather than muscles. I do have a set that clip to my glasses now, which I need as I’ve gotten older. Those are easy.

People who only need correction in one eye get glasses with a prescription in one eye, and a plano lens in the other, which is just a clear lens with no correction or adjustments.

Just googling… If you had money, no.

If you didn’t have money, yes.

https://en.m.wikipedia.org/wiki/Monocle

“Monocles with galleries were often the most expensive. The wealthy would have the frames custom-made to fit their eye sockets. A sub-category of the galleried monocle was the “sprung gallery”, where the gallery was replaced by an incomplete circle of flattened, ridged wire supported by three posts. The ends were pulled together, the monocle was placed in the eye orbit, and the ends were released, causing the gallery to spring out and keep the monocle in place.”