By the early 1970s, trabeculectomy had brought a more predictable outcomethan the established full-thickness filtration, but some compromise in thehypotensive response dampened widespread enthusiasm. About a decade later,Zimmerman et a1 modified trabeculectomy bydissecting away the inner wall of the Schlemm canal while preserving the low-resistancecorneoscleral component of the trabecular meshwork. Despite initial interest,the nearly simultaneous introduction of antimetabolite adjunctive therapyto conventional trabeculectomy deluged Zimmerman’s technically dauntingprocedure with the widely held expectation that antifibrotics would forgivea clumsy technical effort. It became apparent, however, that antimetabolitesmerely traded lower pressure for more complications, notably hypotony andleaking blebs, which were reminiscent of the full-thickness filtrations fromprevious decades.