Keyhole bridge
A frame bridge shaped like an old keyhole, resting on the sides of the nose and arching over the top.
Also: keyhole
A keyhole bridge curves up in the middle and splays at the bottom, so the frame rests on the sides of the nose rather than across its top. It was common on twentieth-century acetate frames and returned with vintage styles. Opticians suggest it for narrow or high nose bridges, and it can make a short nose look a little longer because more of the bridge shows.