Ophthalmology, General
A trephine is a surgical instrument with a cylindrical blade. It can be of one of several dimensions and designs depending on what it is going to be used for. They may be specially designed for obtaining a cylindrically shaped core of bone that can be used for tests and bone studies, cutting holes in bones or for cutting out a round piece of the cornea for eye surgery (e.g. when doing a DSAEK procudure).