The most fruitful sources of failure are, first, a poorly sharpened
knife-needle; second, a badly planned incision; third, inability to
sever the apex of the triangle; fourth, the early loss of aqueous;
fifth, too heavy pressure with the knife-edge, and sixth, rocking or
rotating the knife backward instead of making the sawing movement. All
of these can easily be avoided, if the surgeon will only exercise care
and good judgment.
In an occasional case, the iris-membrane may be so stiff that the apex
of the flap will not retract. If the apex can not be pushed down by the
tip of the knife turn the blade on the flat, puncture the base of the
flap by a quick thrust, and with a sawing motion cut across its fibers
so that it will fall back as though hinged; or, if positive that the
vitreous is not fluid, introduce a keratome in the cornea below, draw
out the triangular tongue, cut it off with the iris scissors, and dress
back the base with a silver spatula.
It is possible that the capsule, or iris tissue, may lose its
anchorage. In that event we must either reverse the procedure by
entering the knife-needle below, and cut from above downward, or else
pass a second knife-needle through the loosened edge of the membrane to
fix it, and then proceed with the usual method.
Occasionally, the apex of the triangular flap will hold fast, because
the last fiber of tissue has not been severed. If the leverage is
too short to incise it from above, withdraw the knife-needle and
reintroduce it far enough from the apex to secure the proper leverage,
and again incise it gently, until it falls back.
Traction on the ciliary processes, accidental puncture of the ciliary
body, or the tearing of the membrane from its ciliary attachment may
all set up iridocyclitis or glaucoma, and should therefore be avoided.
As tense capsular bands are liable to engender a similar condition they
should be incised. If any of these traction bands should remain in the
edge of the coloboma, we may enter the knife behind them and gently saw
through into the already cleared pupil, before withdrawing the knife.
[Illustration: Fig. 42, (Case 1).--Iridotomy in a stiff iris-membrane
(author’s original case).]