In reviewing the questions at issue between these two schools of
iridotomy, one can not help noticing the constant oscillation from one
method to the other as certain advances were made. The method by the
knife-needle seemed to possess the advantage of easy accomplishment
and less postoperative disturbance, but with the disadvantage that
often the pupillary opening was inadequate and promptly reclosed
by plastic exudate. On the other hand, the method by the scissors
was more difficult of accomplishment, caused more traumatism to the
eye, was often complicated by great loss of fluid vitreous, and was
frequently followed by severe inflammatory reaction. If, however, it
proved successful, the resulting pupil was permanent and sufficiently
large for visual purposes. The inclination of all operators seemed
to be toward the use of the knife-needle, and it was only necessity
that forced them to adopt the more complicated procedure of the open
operation with scissors. Von Graefe seemed to recognize this when he
referred to the knife-needle incision as “a sub-corneal act which
enjoys the immunity of subcutaneous operations.”
The chief advantages of iridotomy by the knife-needle are the ease
of incision, the lack of traction on the ciliary body, the freedom
from postoperative inflammatory reaction, the avoidance of opening
an eyeball which may contain fluid vitreous, the lessening of the
tendency to iris hemorrhage from lowered tension, and the avoidance
of the nebulous scar which often follows a large corneal incision in
old inflammatory eyes. The disadvantages revealed in the method of
the knife-needle lay partly in the method and partly in the faulty
instruments constructed in that day. Cheselden, Morand, Sharpe
and Adams all made the mistake of entering the eye back of the
corneoscleral junction, which is so near to the danger zone of the eye.
Adams, however, made a two-fold improvement in adding to his operation
a sawing movement and in advocating the “most delicate pressure of the
instrument” in order to make a free incision. Heuermann was apparently
the first to make the puncture through the cornea instead of through
the sclera.
The advocates of the knife-needle method long labored under the
disadvantage of making a single iris incision, while those who
employed the scissors early discovered that a double incision was
necessary to success. Although Janin was the originator of the scissors
method, Maunoir was the first to deliberately try a triangular flap,
which DeWecker later elaborated and made a permanent success. The
many disastrous results of the open operation, however, compelled
conservative surgeons, like von Graefe, to revert to a study of
Cheselden’s method, and to seriously consider the great advantages
which a successful iridotomy by the knife-needle method would confer on
surgeon and patient alike.