Note: Descriptions are shown in the official language in which they were submitted.
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Microsurgical instrument.
The present invention rela-tes -to a microsurgical cutting
ins-trumen-t to be used in surgical -treatmen-t of glaucoma
by means of a novel opera-tional procedure, which
significantly may be called "selec-tive -trabeculectomy".
Glaucoma is an ailment which enhanced inner pressure in
the eyeball. Within the eye aqueou.shumour is produced at
a fairly constant rate. This liquld is drained out
through filterlike tissue (trabecular meshwork) in the
angle be-tween iris and cornea into a collector canal
running sircularly along the transi-tion between cornea
and sclera (Canal of Schlemm), and from this canal through
20-30 drainage outlets in the eye wall into blood vessels
(water veins).
The cause of ylaucoma is believed -to be a type of
"clogging" of the trabecular rneshwork, so that the out-
flow resistance increases. Then, also the pressure ir.-
crease.s to allow the SaMe volurne of liquid to be drained
out per tirne unit. All treatment aims at reducing the
eye pressure. Such treatment is primarily medical, but
when this is intolerable and/or :insufficient, surglcal
treatment is used.
The surgical treatment may be subdivided according to
three principles,.. namely:
1. Operations aiming at reduced production of aqueous
humour.
2. Fistulizing procedures, i.e. surgical provision of
artificial slits in the eye walls, through which the
liquid may sip out of the eye.
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3. Operations on the trabecular meshwork. ~xisting
procedures of this kind are of two types, i.e.:
a) Approach through -the anterior chamber of -the eye
by means of goniotomy or cautery of the trabecular mesh-
work with laser beams.
b) Approach through the Canal of Sc}llemm. Such
approach consi.sts in opening this canal through a radial
incision in the eye wall ahove -the canal and insertio
oE a blunt p~;obe or probe means with a cutting edye
(trabeculotome). This instrument is then manipulated in
such a way that it tears open or cuts through the trabe-
cular meshwork into the anterior chamber of the eye. With
such procedure a narrow slitlike opening is formed through
the trabecular meshwork. Such slits exhibit, however, a
considerable tendency -to close.
In order to inhibit such closure it is an object of the
invention to provide a microsurgical instrumen-t, which
through appropriate use may form a permanent opening
from the anterior chamber of the eye to the Canal of
Schle.rnm by selective removal of the lnner wall of this
canal along a certain sector. Irl this manner the aqueous
humour gains direc-t access to the outer wall of the
Canal o~ Schlemm, which has outlets or drainage canals,
so tha-t normal drainage of aqueous humour may be re-
established.
Thus, the invention concerns a mucrosurgical instrument
for performing selective traveculectomy in surgical treat-
ment of glaucoma, the instrument including flexible probe
means and a cutting member fixed to the same. On this
background the general inventive fea-ture of the instru-
ment is that the cutting member comprises two ]cnife blades
protruding in different directions from -the probe and each
p~oviding at least one sharp cutting edge turned towards
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a Eree end of the prohe means.
ThiS instrumen-t may be called a trabeculectome, clS it
is designed to be pulled -through the Canal of: Schlemm
along a certain peripherlal sector of the eye. By this
the inner wall of t'he cana~ and the correspondin~ por-
tion of the 0.1 mm thic]c trabeular meshwor]c are cu-t away.
As indicated, the trabeculec-tome consists of probe means
and a cutting member. The probe means is preferably
knob-shaped at the extreme end and made of fle~ible
material, but -this still sufficiently rigid to be insert-
ed into and direc-ted through the Canal of Schlemm. The
cutting member has a double-cutting knife, the two
cutting edges of which are angularly separated to such
extent that the issuing V-orm fits into the scleral
yroove in the eye wall, in which -the trabecular meshwork
is embedded. Advantageously, the cuttinc~ rnember is
assyme-trical ln such a manner -that the knife blade that
projects perpendicularly in-to the anterior chamber to-
wards the iris, is short, whereas the blade that pro-
5ects obli~uely into the anterior chamber and forms a
small angle with the back side of -the cornea, is longer.
Th~s feature stabilizes the correct position of the knie.
The probe means of the trabeculectome i.s directed through
an incision in the eye wa].l into and along -the Canal of
Schlemm, and is pulled out through another incision at a
certain distance rom the first one. The cut-ting member
of the trabeculectome is pulled after the probe means
through the Canal of Schlemm w.ith the two ~niEe edges
pro5ecting into the anterior chamber of the eye and
thereby cutting away a strip of the trabecular tissue and
the inner wall of the Canal of Schlemm which are located
between the cutting edges. This tissue strip is prefer-
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ably removed together with the trabeculectome when itis pulled ou-t through the seconcl incision in the eye
wall. Such removal of -the tissue strip rnay be secured
by mountiny one or more hooks :in the angle be-tween the
two knife edges in order to catch -the cut away strip
and carry it out of -the eye.
The microsurgical instrumen-t accordiny to the in~ention
allows a surgical procedure which secures a permanent
broad opening be-tween the an-terior chamher o the eye
and the ou-tlets from the Canal of Schlemm by removing
-the trabecular meshwor~< and the inner wall of the canal.
Tissue removal together with maintained cell casing on
the outer wall of the Canal of Schlemm make a closure of
this opening improbable, even in -the long run. `
Experiences with this method up to now suggest a low
rate of complications, so that the operational indica-
tions probably may be extended. I'his means that the
patients may be operated a-t an earlier stage and thus
expensive and troublesome medical treatrnent is avoided.
The invention will now be explained in more de-tail with
reference to exemplified embodiments as shown in the
accompanying drawings, in which
~igure 1 shows a first embodiment of -the instrument in a
cross-section throuyh the cutting member at righ-t
angle to the longitudinal axis of the probe means.
Figure 2 is a side elevation oE the instrument shown in
Figure 1.
Fiyure 3 shows the instrument in Figures 1 and 2 in
perspective view.
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Figure 4 is a side elevation of another embodirnent of
the instrument, and
Figure 5 shows a cross-section through the cutting member
at right angle to the longitudinal axis o~ the probe means
in the embodiment of Figure 4.
The probe means A is in the embodiment shown in Fig. 1-3
a monofilament of nylon, which is fused at one end to Eorm
a rounded knob. The other end of the probe is inserted
into a hole in s-teel member B and rigidly clamped to this
member. The knife member C is formed from a 1/100 - 5/100
mm thick stainless steel foil, which is finely sharpened
at the front side and bent into an approximate V-form
adapted to the local anatomical featuresof the eye at the
Canal of Schlemm and the trabecular meshwork. The member
C is fixed to the member B and thereby also the probe A by
means of a two-component epoxy glue. Point welding
technique ma~ also be used, if the probe means is mounted
on the member B after the welding s-tep. An arrow above
the probe in Fig. 2 shows the pulling direction in use.
Between the knife blades a barbed hook is fixed to the
steel member B in order to catch the tissue strip which is
cut free between the knives. This hook is also fastened
by means of epoxy resin. Finally, a layer of epoxy resin
is applied to the joints and transitions between the steel
member B and the ~robe ~ to provide a completely smooth
surface. Tefl~ and similar polymers may also be used as
covering layer and silicone is considered particularly
advantageous for this purpose.
Another embodiment is illustrated in the Figures 4 and 5.
In this case the probe is made of flexible metal and welded
to the knife member. The extreme rear end of the probe is
bent forward between the knife blades to form a small sharp
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hook. All joints are provided with a cover of epoxy resin
and the probe is furnished with a layer of resin at the
end to form a ~inely rounded knob.
The knife blades C1, C2 need not necessarily have a free
end. Thus, the extreme ends of the knife blades may well
be interconnected to form a closed knife blade ring, e.g.
of approximate triangular shape. The cut-away tissue strip
may then be captured by closing the rear opening of the
knife ring, thereby catching the strip in the "container"
thus formed.
The instrument must necessarily be quite small to allow the
intended surgical treatment of the eye. Thus, in the
illustrated embodiments the probe has a diameter of
approximately 0.25 mm and a length of t,-he order of magni-
tude 4-8 crn and rather freely adaptable to the requirements
of the eye surgeon. The shorter knife of the cutting member
may suitably have a length of about 0.7 - 1.~ mm, while the
longer, preferably curved knife may have a length of 1.5 -
1.8 mm. I'he width of the knives may be of the order of
magnitude 0.3 - 0.5 rnm.
In the embodiments shown in the drawings and described above
the cutting member is fixed at one end of the probe means.
However, as indicated in the following patent claims, the
cutting member may well be fixed to the probe at another
location, e~g. on the central part of the same. The portion
of the probe projecting from the rear side of the cutting
member may then be used for improved steering of the
instrument, when it is guided between the two incisions in
the eye wall. If the cutting member is located approximate-
ly centrally on the probe, the protruding knife blades may
further be provided with a cutting edge on both sides, so
that the ins-trument may be effectively pulled in both
directions through the Canal oE Schlernm.
Although the cutting edges are shown in -the drawing to
form essentially right angles with the longitudinal axes
of the probe means, the edges may a:Lso according -to the
invention advantageously be inclined at an angle of 45 -
90 in the pulling direction with respect -to the probe
axis. An inwards directed radlal force is tllell exercised
against the tissue strip during -the movernen-t of the
cutting member through the Canal of Schlemrn.
