I've had glasses for years and now have old people glasses. The progressive lenses ( lineless bifocals) that I have now are often tricky to focus because you have to get the glasses in the right place through a viewfinder to not be seeing through the reading glasses part or the middle part. (Perhaps with a ground glass you need the reading glasses part.)

Anyway I've decided to get an extra set of glasses with the focussing eye having only the distance lens and not the progressive lens. So you don't have to focus your camera and your glasses at the same time.