If there is a flaw in the basic design of eyeglasses, it is in the hinge and stems. Because the stems of every pair of eyeglasses protrude from the hinges in the way they do, that means that when folding them shut, like this...
...the overall closed shape is a lot bulkier than the constituent parts. Which in turn makes eyeglass cases bulkier. As someone who doesn't like carrying things and did not require eyeglasses until later in life, I hate having to carry this extra blocky thing around, and I'll never get used to it.
Japanese manufacturer Nishimura Precision Co. has designed a brilliant solution with their Paperglass product. By designing the stems to curve upwards from the hinges, it enables them to clear the lenses while folded in.
This renders the glasses incredibly flat—so flat that if you're using them as reading glasses, the specs themselves (even inside the case) can be used as a bookmark.
The following video gives you a better sense of what the glasses look like from all angles. It's narrated completely in Japanese, but all you really need to see is the hand model manipulating the glasses in space:
And with the stems made from such thin wire, they do not appear visually odd (at least to me) when worn:
This is no mere concept, by the way; the glasses are in production and on the market (though currently it appears to be Japan-only), and they've even scooped up a Good Design Award.