[rimless glasses frames]

Originally Posted by progressive glasses

I need bifocals, glass not plastic, that go dark in sunlight, in preferably a frame that has a strap around the back of the head, doesn't fall easily from my nose, but can be removed easily. As a surveyor I need to remove my glasses to look through telescopes and as a sailor I need something that doesn't easily fall off.

Haven't heard of bifocal glasses lenses,but i do have a pair of photochromic lenses which could change color indoor and outdoor,they are made of plastic.
Maybe you can contact your doctor to enquiry.