MICROSURGICAL INSTRUMENT

Abstract: A microsurgical instrument for performing selective trabeculectomy in surgical treatment of glaucoma includes flexible probe means (A) and a cutting member (C) fixed to the same. The cutting member comprises two knife blades (C1, C2) protruding in different directions from the probe means and each providing at least one sharp edge (E1, E2) turned towards a free end of the probe means. The instrument is designed to be pulled between two incisions in the eye wall with the probe means foremost through the Canal of Schlemm at the transition between cornea and sclera, thereby cutting away the inner wall of the canal and the corresponding part of the trabecular meshwork located in the canal. The aqueous humour of the eye then gains access to the outer wall of the Canal of Schlemm with its drainage outlets leading out of the eye.

Description: Microsurgical instrument The present invention relates to a microsurgical cutting instrument to be used in surgical treatment of glaucoma by means of a novel operational procedure, which significantly may be called "selective trabeculectomy". Glaucoma is an ailment which enhanced inner pressure in the eyeball. Within the eye aqueous humour is produced at a fairly constant rate. This liquid is drained out through filterlike tissue (trabecular meshwork) in the angle between iris and cornea into a collector canal running sircularly along the transition between cornea and sciera (Canal of Schiemm) , and from this canal through 20-30 drainage outlets in the eye wall into blood vessels (water veins) . The cause of glaucoma is believed to be a type of "clogging" of the trabecular meshwork, so that the out¬ flow resistance increases. Then, also the pressure in¬ creases to allow the same volume of liquid to be drained out per time unit. All treatment aims at reducing the eye pressure. Such treatment is primarily medical, but when this is intolerable and/or insufficient, surgical treatment is used. The surgical treatment may be subdivided according to three principles.,., namely: 1. Operations aiming at reduced production of aqueous humour. 2. Fistulizinσ procedures, i.e. surgical provision of artificial slits in the eye walls, through which the liquid may sip out of the eye. B 3. Operations on the trabecular meshwork. Existing * 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 Schiemm. Such approach consists in opening this canal through a radial incision in the eye wall above the canal and insertion of a blunt pr.obe or probe means with a cutting edge (trabeculoto e) . 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 instrument, which through appropriate use may ■ form a permanent opening from the anterior chamber of the. eye to the Canal of Schiemm by selective removal of the inner wall of this canal along a certain sector. In this manner the aqueous humour gains direct access to the outer wall of the Canal of Schiemm, which has outlets or drainage canals, so that normal drainage of aqueous humour may be re¬ established. Thus, the invention concerns a ucrosurgical 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 feature of the instru¬ ment is that the cutting member comprises two knife blades protruding in different directions from the probe and each providing at least one sharp cutting edge turned towards a free end of the probe means. This instrument may be called a trabeculectome, as it is designed to be pulled through the Canal of Schiemm along a certain peripherial sector of the eye. By this the inner wall of the canal and the corresponding por¬ tion of the 0.1 mm thick trabeular meshwork are cut away. As indicated, the trabeculectome consists of probe means and a cutting member. The probe means is preferably knob-shaped at the extreme end and made of flexible material, but this still sufficiently rigid to be insert¬ ed into and directed through the Canal of Schiemm. The cutting member has a double-cutting knife, the two cutting edges of which are angularly separated to such extent that the issuing V-form fits into the scleral groove in the eye wall, in which the trabecular meshwork is embedded. Advantageously, the cutting member is assymetrical in such a manner that the knife blade that projects perpendicularly into the anterior chamber to¬ wards the iris, is short, whereas the blade that pro¬ jects obliquely into the anterior chamber and forms a small angle with the back side of the cornea, is longer. This feature stabilizes the correct position of the knife. The probe means of the trabeculectome is directed through an incision in the eye wall into and along the Canal of Schiemm, and is pulled out through another incision at a certain distance from the first one. The cutting member of the trabeculectome is pulled after the probe means through the Canal of Schiemm with the two knife edges projecting 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 Schiemm which are located between the cutting edges. This tissue strip is prefer- ably removed together with the trabeculectome when it is pulled out through the second incision in the eye wall. Such removal of the tissue strip may be secured by mounting one or more hooks in the angle between the two knife edges in order to catch the cut away strip and carry it out of the eye. The microsurgical instrument according to the invention allows a surgical procedure which secures a permanent broad opening between the anterior chamber of the eye and the outlets from the Canal of Schiemm by removing the trabecular meshwork and the inner wall of the canal. Tissue removal together with maintained cell casing on the outer wall of the Canal of Schiemm 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. This means that -the patients may be operated, at an earlier stage and -thus expensive and troublesome medical treatment is avoided. The invention will now be explained in more detail with reference to exemplified embodiments as shown in the accompanying drawings, in which Figure 1 shows a first embodiment of the instrument in a cross-section through the cutting member at right angle to the longitudinal axis of the probe means. Figure 2 is a side elevation of the instrument shown in Figure 1. Figure 3 shows the instrument in Figures 1 and 2 in perspective view. Figure 4 is a side elevation of another embodiment of the instrument, and Figure 5 shows a cross-section through the cutting member at right angle to the longitudinal axis of 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 form a rounded knob. The other end of the probe is inserted into a hole in steel 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 features of the eye at the Canal of Schiemm 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 a y also be used, if the probe means is mounted on the member B after the welding step. 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 probe A to provide a completely smooth surface. Teflon 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 ' OΛΪPI 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 finely rounded knob. The knife blades Cl, C2 need not : ecessarily 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 forme .. 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 the order, of magni¬ tude 4-8 cm 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 - 1.0 ιr_m, while the longer, preferably curved knife may have a leng-th of 1.5 - 1.8 mm. The width of the knives may be of the order of magnitude 0.3 - 0.5 mm. In the embodiments shown in the drawings and described above the cutting member is fixed at one end of the probe means. However, at 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 -ay 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 furhter be provided with a cutting edge on both sices, so that the instrument may be effectively pulled in both directions through the Canal of Schiemm. 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 also 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 radial force is then exercised against the tissue strip during the movement of the cutting member through the Canal of Schiemm.

Claims: S Claims. 1. Microsurgical instrument for performing selective trabeculectomy in surgical treatment of glaucoma, the instrument including flexible probe means and a cutting member fixed to the same, c h a r a c t e r i z e d i n that the cutting member comprises two knife blades protruding in different direc¬ tions from the probe and each providing at least one sharp cutting edge turned towards a free end of the probe means. 2. Instrument as claimed in claim 1, c h a r a c t e r i z e d i n that at. least one catch¬ ing device for cut-away tissue is mounted on the cutting member behind the sharp cutting edges. 3. Instrument as claimed in claim 1 or 2, c h a r a c t e r i z e d i n that the two knife edges protrude in different length from the probe means, the shorter blade being straight and the longer having a certain curvature, preferably adapted to the boundary surface of he tissue to be cut away. 4. Instrument as claimed in claim 1 or 2, c h a r a c t e r i z e d i n that the extreme ends of the two knife blades are interconnected to form a closed knife blade ring. 5. Instrument as claimed in claims 2-4, c h a r a c t e r i z e d i n that the catching device is constituted by one or more hooks with the hook opening turned towards a free end of the probe means. 6. Instrument as claimed in claims 2-4, c h a r a c t e r i z e d i n that the catching device is constituted by a plate member connected with an edgεfree rim of the knife blades and preferably formed as a trapping hook, partly or completely covering the inter¬ space between the knife blades. 7. Instrument as claimed in claims 1-6, c h a r a c t e r i z e d i n that the cutting edges of the knife blades form an angle of 45-90 with the longitudinal axis of the probe means. 8. Instrument as claimed in claims 1-7, c h a c t e r i z e d i n that the probe means is constituted by a synthetic fibre stuture with a metallic holder clamped to the suture, e.g. at an extreme end of the same, the cutting member being glued or welded to the holder. 9. .Instrument as -claimed in claims 1-7, c h a r a c t e r i z e d i n that the probe means is made from flexible metallic material which is welded to the cutting member, e.g. at an extreme end, and possibly covered with plastics material, preferably silicone. 10. Instrument as claimed in claims 1-7, c h a r a c t e r i z e d i n that the cutting member is moulded in hard plastics material integrated with or assembledwith the probe means. "BURE4 _0. PI

Inventors: SKJAERPE FINN
Applicants: SKJAERPE FINN
Application year: 1982
Main classification: A61B17
IPC codes: A61B17, A61F9