Most eyewear are created as one-size-fits-all. There's nothing wrong with that. We've been wearing them that way for as long as they have existed. If you'd like a more tailored fit for your glasses, though, your best bet is to pony up serious cash and have custom eyewear made. Protos 3D Printed Eyewear wants to change this, offering eyewear frames that are custom 3D-printed according to the wearer's exact size.
Don't worry, Protos isn't going to require you to learn CAD, create your own designs, and submit it for 3D-printing. Instead, they offer 24 existing frame designs, which they can adjust to a perfect fit that enhances your facial structure and dimensions.
Being 3D printed, of course, Protos' frames are made from plastic, which will probably cause some folks to smirk. Fortunately, they don't just use regular plastic, but a proprietary composite that they describe as both "extremely flexible and impact-resistant," all while being lighter than titanium. To get your glasses custom-fit, you take two pictures with a credit card in it for scale using their web-based interface, which will process the images and perform facial analysis. The web app will then show you three potential custom-sized options out of the 24 frames from which you can pick.
As of now, Protos doesn't have their web app online, so you can't quite get a pair of custom-fitted specs yet. They are currently raising funds to bring the system online and you can help by pledging for a pair of glasses (which they will begin fulfilling starting December) with either polarized non-prescription lenses or non-tinted prescription ones. Prices start at $249.