The method of V-shaped iridotomy, performed by me with my modified Hays
knife-needle, may be described as follows:
_First Stage._--With the blade turned on the flat, the knife-needle is
entered at the corneo-scleral junction, or through the upper part of
the cornea (Fig. 38), and passed completely across the anterior chamber
to within 3 millimeters[33] of the apparent iris periphery. The knife
is then turned edge downward, and carried 3 millimeters to the left of
the vertical plane (Fig. 39).
[33] Compare with millimeter scale beneath each diagram.
_Second Stage._--The point is now allowed to rest on the iris-membrane,
and with a dart-like thrust the membrane is pierced. Then without
making pressure on the tissue to be cut, the knife is drawn gently up
and down with a saw-like motion, until the incision has been carried
through the iris tissue from the point of the membrane puncture to
just beneath the point of the corneal puncture. This movement is made
wholly in a line with the axis of the knife, the shank passing to and
fro through the corneal puncture, and the loss of any aqueous being
carefully avoided in the manipulation.
[Illustration: Fig. 38.--Author’s V-shaped iridotomy. Knife-needle
entered through cornea.]
[Illustration: Fig. 39.--Author’s method. Plan of first incision.]
[Illustration: Fig. 40.--First incision completed. Plan of second
incision.]
[Illustration: Fig. 41.--Pupil resulting from V-shaped iridotomy.]
_Third Stage._--The pressure of the vitreous will now cause the edges
of the incision to immediately bulge open into a long oval (Fig.
40) through which the knife-blade is raised upward, until above
the iris-membrane, and then swung across the anterior chamber to a
corresponding point on the right of the vertical plane, which, owing to
the disturbance in the relation of the parts made by the first cut, is
now somewhat displaced and the second puncture must be made at least
1 millimeter farther over, i. e., 4 millimeters to the right of the
vertical plane (Fig. 40).
_Fourth Stage._--With the knife point again resting on the membrane,
a second puncture is made by the same quick thrust, and the incision
rapidly carried forward by the sawing movement to meet the extremity
of the first incision, at the apex of the triangle, thus making a
_converging_ V-shaped cut (Fig. 41). Care must be taken at this point
that the pressure of the knife-edge on the tissue shall be most gentle,
and that the second incision shall terminate a trifle inside the
extremity of the first, in order that the last fiber may be severed and
thus allow the apex of the flap to fall down behind the lower part of
the iris-membrane. If the flap does not roll back of its own accord it
may be pushed downward with the point of the knife. When the operation
is completed the knife is again turned on the flat and quickly
withdrawn.