I'm very mildly nearsighted, prescription -1.25. This is good enough that I don't need glasses most of the time, and bad enough that having glasses is sometimes pretty important: driving, rushing through an airport, out at a show, etc. I have a few pairs of normal-sized glasses with bulky cases. I've tried contact lenses (they don't agree with me). None of these options gave me the versatility I really wanted: glasses that I can keep in my pocket - off my face most of the time - and quickly take out whenever I need them. I've wanted glasses like this for years, but getting into backpacking finally prompted me to get some made. After seeing how expensive it is to build an ultralight kit, I realized this project was low-hanging fruit.
There seems to be a huge market for reading glasses just like this, but nothing for nearsighted people - so I figured I'd get them custom made. I bought a few different off-the-shelf pairs of reading glasses, and then I asked around at 5-6 different optometrists around town, to find someone who could replace the lenses with my prescription. I had very little luck. Eventually, I found an easy solution in https://lensesrx.com/. They did a great job, quickly and cheaply. Really, that's all there is to it, but I wanted to post this just to let others know that this is a really easy job, as long as you find the right company to do it.
I've had some strange responses when showing these off, so I understand it may not make sense for everyone, but they're perfect for me. They're also cheaper than any glasses you'll buy full-price in a shop.
Step 1: Buy the Tiniest Over-the-counter Reading Glasses You Can Find
I tried frames similar to both of these:
Just make sure they have glass lenses that aren't fused to the frame. For example, thinoptics makes some pretty neat compact glasses (https://www.thinoptics.com/), but the frame and lenses are a single piece of plastic, so the lenses aren't replaceable.
Step 2: Send Them in to Your Choice of Lens Replacement Service
I spoke with several local optometrists about getting this work done. All but one told me they couldn't do it. The last one said he was willing to try, but couldn't guarantee success, and it would cost $100+ just to try. Maybe professionals in your area are more flexible, but in my case I had no option but to try a mail-order service. The service I mentioned above did the job for $25 per frame. I sent them two frames to save on the shipping cost (and in case one of them didn't work out). After receiving the frames, they finished the work in two days and sent them back.
That's it! I know it's not exactly a DIY project, but I thought it was worth sharing.
Here's a comparison of the sizes:
weight: 14.7 (glasses) + 118.8 (case) = 133.5g
case dimensions: 15x7.5x3.5
weight: 13.6g (glasses) + 18.1g (case) = 31.7g (4x lighter)
case dimensions: 7.5x3.5x2cm (7x less bulky)