I do not advise that to build your own glasses for every-day wearing. Especially if you are not an adult, choosing the wrong glasses parameters (like a wrong pupil distance or glasses that are to strong) can permanently damage your vision.
But if you entertain a curious mind and got the "maker spirit", you might give it a spin and build your own reserve / emergency glasses.
please note: textwriting is in progress.
For now, just the pictures:
To make thing rather easy, i got myself some affordable spectacle frames with a circular shape for the glasses. The reason was that i wanted to be able to fine-tune the cylinder-axis orientation. Luckily, my inter-pupillary distance (IPD) exactly matches the distance between the midpoints of the inserted glasses.
As a first step, i marked the center if the demo-glas that came with the spectacle frame:
Next, i determined the optical axis / midpoint of the lens using a cross-laser. You can also use a simple laserpointer for that task. (TODO - description of optical axis - measurement)
Now, i could place the demoglas on top of the lens and mark the outline with a water-resistant marker pen:
Next, i milled the circular shape of the glas using a multitool and a drill-stand. It is important to carefully supply a thin jet of water to cool the milling process and to bind the plastic dust. Please note: you must use a battery powered version of a multitool (for example, the Proxxon IBS/A) to avoid the risk of electric shock in case water enters the multitool.
Finally, i shaped the lens-border with a smaller multitool to provide enough taper such that it fits into the spectacle frame:
I think the result is quite ok for my first ever DIY Glasses (yes, i happened to put a little dent into one edge):
TODO: