(1) _Division_ of the thickened iris-membrane by an incision made either through the sclerotica or through the cornea. This is true _iridotomy_. (2) _Excision_ of a portion of the iris through a previously made corneal opening. This is now known as _iridectomy_. (3) _Separation_ of the iris from its ciliary attachment. This was generally known as _iridodialysis_, but sometimes called _iridorrhexis_. (4) Simple _incision_ of the pupillary margin, and of the free iris tissue. This has been designated _sphincterotomy_ by some, and _coretomy_ or _iritomy_ by others. Either one of the latter terms is to be preferred, because it is more clearly descriptive. (5) _Detachment_ of the synechiæ at the pupillary margin, either anterior or posterior, thus allowing the pupil to retract. This was known as _corelysis_. (6) _Strangulation_ of the prolapsed iris in the corneal incision was called _iridencleisis_. The prolapse was sometimes tied with a ligature. (7) _Trephining_ of the iris-membrane, by passing a small trephine or punch through a corneal incision. (8) _Section_ and removal of a portion of the sclerotica and chorioid by knife or trephine, with replacement of the conjunctiva over this opening, the conjunctiva thus acting as a substitute for the cornea in transmitting light. This was called _sclerectomy_. (9) _Transplantation_ of the cornea for total leucoma. This was usually preceded by partial or complete trephining of this membrane. In addition to these nine distinct methods certain combinations of these have been described and successfully practiced: (10) _Division_ and _excision_ have frequently been performed together. (11) _Separation_ and _excision_ have likewise had some vogue. (12) _Separation_ and _strangulation_ have occasionally been practiced. (13) _Detachment_ of the synechiæ and _excision_ have also been performed. HISTORICAL REVIEW OF IRIDOTOMY. In this brief review of iridotomy,[2] we shall confine our attention to the methods that have been advanced for the formation of an artificial pupil in cases of membranous occlusion of the pupil following removal of the lens, either by couching, extraction or discission, the iris-membrane in these cases being chiefly composed of inflamed iris tissue glued down by retro-iridian exudate to the thickened lens capsule. [2] Wagner, Karl Wilhelm Ulrich: Inaugural Thesis, Göttingen, 1818. He invented the designation iridotomia, which he formed from the original Greek, ἶρις, ἶριδος (the iris) and τομή (cut). The early history of iridotomy shows that the advocates of this operation were divided into two schools, (1) those recommending the use of the _knife-needle_ for incising the iris-membrane, and (2) those adopting the method of introducing _scissors_ through a previously made corneal section and freely incising the iris-membrane, or excising a portion of the same. We will first consider the school which advocated incision by the knife-needle.