WO1992019167A1

WO1992019167A1 - Eye surgery performed with an electrosurgical instrument

Info

Publication number: WO1992019167A1
Application number: PCT/US1992/003197
Authority: WO
Inventors: Harry G. Reimels; Yue-Kong Au
Original assignee: Mentor O&O Inc.
Priority date: 1991-04-26
Filing date: 1992-04-17
Publication date: 1992-11-12
Also published as: AU2024192A

Abstract

A bipolar electrosurgical instrument comprising at least three elelectrodes (12, 20, 24) having distal ends that are disposed at successive, axially spaced regions in a distal region of the instrument so that bipolar energizing potential (received by proximal ends of the electrodes) causes energizing current (70) to flow axially between the electrodes in the distal region. The instrument can be curved, (16) or not. In another aspect the instrument comprises at least two electrodes (72, 74) having distal ends disposed at an oblique angle with respect to the longitudinal axis of the instrument. Either instrument is useful in eye surgery to form a drainage path through the sclera to relieve symptoms of glaucoma. During the surgical procedure, the distal tip of the instrument (18) is inserted into the eye through an incision made remotely to a puncture site (50) where the drainage path (52) will be formed and is directed to the puncture site.

Description

EYE SURGERY PERFORMED WITH AN ELECTROSURGICAL INSTRUMENT Background of the Invention

This invention relates to performing surgery, particularly eye surgery to relieve symptoms of glaucoma, using an electrosurgical instrument.

Glaucoma is a disease which causes an increase in pressure of aqueous fluid within an eye. If left untreated, the increased pressure can cause damage to the affected eye and a loss of vision. As described below, the pressure can be relieved by providing a drainage path through the sclera (i.e., the fibrous coating that encloses the eye in regions other than the cornea) or at the corneal-scleral junction.

In one known technique for forming the scleral drainage path, the sclera is accessed by opening the conjunctiva (a mucous membrane that covers a portion of the sclera near the cornea) using a scalpel or a pair of scissors. A flap-shaped incision is then made through the sclera and the conjunctiva is closed over the sclera. Excess aqueous fluid drains out of the eye through the incision and into the space between the sclera and the conjunctiva, where it is absorbed by the lymphatic system.

The trauma to the conjunctiva induced by the use of the scalpel can cause the conjunctiva to adhere to the sclera, thereby blocking the incision and impeding drainage. As a result, other techniques not requiring manipulation of the conjunctiva have been developed. In one such technique, a small balloon or "bleb" is formed under a region of the conjunctiva by injecting saline solution between the conjunctiva and the sclera. To minimize trauma to the conjunctiva, a very small hypodermic needle is used to inject the saline and form the bleb. Once the bleb is formed, a straight trephine (a surgical instrument having a tapered cutting blade for cutting circular sections of tissue) is inserted into the anterior chamber of the eye diametrically across the cornea from the bleb. The surgeon advances the trephine under the cornea and over the iris until the tip of the instrument meets the sclera beneath the bleb. By rotating the trephine, a circular incision is cut through the sclera to provide the drainage path.

Scar tissue which forms during healing may cause partial or complete closure of the scleral incision, thereby blocking the drainage path. Medication has been used to avoid or delay closure of the scleral incision, but the side effects of the medication are undesirable for some patients. Thus, in order to avoid the closure of the fistula or opening, it has been suggested that the drainage path might be formed by cauterization (i.e., with an electrosurgical instrument) . In one suggested technique, a cauterizing needle is advanced under the cornea from an entrance point in the eye located 80° to 100° circumferentially away from the site of the bleb. The technique of cauterizing the surrounding scleral tissue while making the fistula is in agreement with other techniques such as external thermal sclerostomy where closure of the fistula is delayed by thermal cauterization of the scleral tissue surrounding it.

Summary of the Invention One general aspect of the invention is an electrosurgical instrument that includes at least three electrodes having distal ends that are disposed at successive, axially spaced regions in a distal region of the instrument so that bipolar energizing potential (received by proximal ends of the electrodes) causes energizing current to flow axially between the electrodes in the distal region.

Preferred embodiments include the following features. The distal end of a first one of the electrodes is axially disposed between the ends of second and third electrodes, and the first electrode is connected to receive energizing potential of opposite polarity than that applied to the second and third electrodes. The electrodes are arranged coaxially with the first electrode disposed radially between the second a third electrodes. Energizing current thus flows axially between the first and second electrodes and between the first and third electrodes. As a result, electrosurgical activity (such as cauterization) is achieved along an increased axial region of the instrument.

The distal tip of the instrument is sharpened to facilitate tissue penetration. Preferably, the electrodes are curved so that the distal tip is positioned at an angle (such as obliquely) with respect to the longitudinal axis of the instrument. In some types of surgical procedures (such as glaucoma surgery) , this greatly facilitates positioning the tip of the instrument at a site to be punctured and cauterized. The first electrode is a tube insulatingly disposed within the second electrode (which is, for example, a slightly larger diameter tube) . The third electrode is a wire insulatingly received within the first electrode tube.

Another aspect of the invention features a bipolar surgical instrument that includes at least two electrodes that have axially spaced distal ends in the distal region of the instrument, and that are constructed to dispose the distal region at an oblique angle with respect to the longitudinal axis of the instrument. In another general aspect, the invention provides a surgical technique in which a bipolar electrosurgical instrument that has at least two electrodes constructed to have distal ends disposed at an oblique angle with respect to the longitudinal axis of the instrument is used to puncture body tissue and cauterize the puncture. The tip is inserted into the body remote from the puncture site, and the instrument is manipulated to bring the tip into contact with the tissue at the puncture site; pressure is placed on the tip of the instrument while applying bipolar energizing potential, thereby causing the instrument to pierce and cauterize the tissue.

Preferred embodiments include the following features.

The procedure is performed on the eye and the puncture is made in the sclera to provide a drainage path for aqueous fluid therethrough to relieve the symptoms of glaucoma. The puncture is made at the junction between the sclera and the cornea under a preformed bleb between the conjunctiva and the sclera. The incision for the instrument is made approximately 6-7 mm from the puncture site. Preferably, the electrodes are curved to provide the oblique orientation. Among other advantages, this allows the surgeon to trace an arcuate path during manipulation of the instrument. The instrument may comprise more than two electrodes.

The oblique relationship of the tip of the instrument with respect to the longitudinal axis allows the distal tip to be manipulated to the puncture site without intruding into the optical path of the eye. As a result, the instrument is kept away from the delicate endothelial cells on the underside of the cornea, thereby substantially reducing the risk of damaging such cells and impairing eyesight. The bipolar energizing potential is sufficient to cauterize the puncture but insufficient to substantially damage the cornea or the iris.

Because the puncture is cauterized, it resists partial or full closure during healing. As a result, the drainage path is maintained, reducing the need for follow-up surgery or medication to help maintain the drainage path open. The surgical procedure is fast and poses little risk of eye damage. Additionally, as the instrument cauterizes the puncture opening, blood vessels at the puncture site are also cauterized, thereby minimizing bleeding.

Other advantages and features will become apparent from the following detailed description and from the claims.

Detailed Description Fig. l is a partial cross-sectional view of one embodiment of electrosurgical instrument according to the invention. Fig. 2 is an enlarged view of the tip of the instrument of Fig. 1.

Figs. 3 and 4 are useful in understanding a surgical procedure performed using the instrument of Fig. 1. Fig. 5 is a partial cross-sectional view of an alternative embodiment of the electrosurgical instrument of the invention.

Structure

Referring to Figs, l and 2, electrosurgical instrument 10 includes three coaxial electrodes which receive bipolar electrical potential during operation. The construction and operation of instrument 10 are described in detail below, but briefly, instrument 10 applies voltage of a given polarity to the center electrode (an inner tube 20, Fig. 2) while at the same time applying voltage of the opposite polarity to both the outer electrode (an outer tube 12) and inner electrode (a steel wire 24) . The distal ends of the electrodes are disposed at successive, axially spaced regions at the distal tip 18 of instrument 10. The center electrode is disposed radially between the inner and outer electrodes, and the tip of the center electrode is disposed axially between the tips of the inner and outer electrodes. As a result, at tip 18 electric current flows between tubes 12, 20 and between tube 20 and wire 24, thereby axially elongating the region of cauterizing activity of instrument 10 (i.e., relative to that which would be produced if only two electrodes were used) . Outer tube 12 is made from thin-walled (0.0025 inches thick) , 20 gauge 304 stainless steel and is secured within the distal end of a plastic housing 14. Tube 20 is formed of 23 gauge 304 stainless steel, has walls 0.0025 inches thick, and extends coaxially within outer tube 12. Tube 20 protrudes slightly from the proximal and distal ends of tube 12. Tubes 12, 20 are electrically insulated from each other with a non- conductive polymeric sleeve 22 shrunk-fit over tube 20. Sleeve 22 is and has a thickness of between 0.002 and 0.003 inches. Wire 24 is formed of 0.013 inch diameter 304 stainless steel, extends coaxially within tube 20, and protrudes from the proximal and distal ends of tube 20. Wire 24 is insulated from tube 20 by PTFE sleeve 26, which extends along substantially the entire length of wire 24. During assembly, PTFE-coated wire 24 is inserted through tube 20 (either before or after applying sleeve 22) and PTFE-coated tube 20 is inserted through tube 12.

The electrode assembly (i.e., tubes 12, 20 and wire 24) is then inserted into and secured within housing 14. Housing 14 can have any suitable construction (e.g., it can be injection molded or formed from discrete plastic members adhered together). Likewise, tubes 12, 20 and wire 24 can be mounted within housing 14 in any suitable manner. Examples of housings and mounting techniques are described in a copending application entitled "Bipolar Instrument for Lipolytic Diathermy" (Serial No. 07/600,609, filed on October 19, 1990), which is assigned to the same assignee as this application and is incorporated herein by reference. Tubes 12, 20 and wire 24 extend distally from housing 14 for a total of one inch.

When first assembled together, the tips of tubes 12, 20 and wire 24 are co-extensive. The dimensions of tubes 12, 20, wire 24, and sleeves 22, 26 are such that a tight fit is obtained between wire 24 and tube 20, and between tube 20 and tube 12. But to ensure that the tip 18 of instrument 10 will, when sharpened by grinding as described below, have a precise, sharp point, the distal region C (Fig. 1) of the electrodes are first compressed together (i.e., swaged). Swaging is performed by driving the electrode assembly into a tapered opening in a block that is slightly smaller than the initial outer diameter of tube 12. For example, the nominal outer diameter of tube 12 (e.g. , in non-swaged region D) is approximately 0.036 inches, and swaging reduces the outer diameter of tube 12 to approximately 0.033 inches in region C. Regions C and D are each about one-half inch long. After swaging, sleeves 22, 26 are tightly compressed between the metal tubes 12, 20 and wire 24, and as a result sleeves 22, 26 resist splitting or tearing during grinding.

The distal ends of tubes 12, 20 and wire 24 are then ground to a sharp conical point in the region of tip 18. The point has an included angle B of approximately 30°, which is suitable for puncturing body tissue such as skin and membranes of the eye. To grind tip 18, instrument 10 is mounted in a collet (not shown) so that the distal ends of tubes 12, 20 and wire 24 protrude. The collet is then rotated (e.g., at 550 rpm) and a grinding wheel (not shown) rotating at, e.g., 3600 rpm is advanced against the distal ends of tubes 12, 20 and wire 24 at an angle equal to the included angle B and held against the ends to remove the excess material. Grinding proceeds in this fashion for approximately 10 seconds, after which the grinding wheel is advanced only slightly further against tip 18 and held for another 5 seconds to polish the surface of tip 18 to a smooth finish.

After grinding, tubes 12, 20 and wire 24 are bent as a unit to form a curved region 16 approximately 0.25 inches proximally of tip 18. The radius of curvature of curved region 16 is approximately 0.12 inches, and curved region 16 produces an oblique angle A of approximately 45° between the longitudinal axis L of instrument 10 and the axis of tip 18. To prevent plastic deformation or creasing in curved region 16, tubes 12, 20 are sufficiently soft and thin to allow bending, thereby ensuring that instrument 10 will pass smoothly through tissue. In addition, wire 24 is annealed prior to assembly to avoid its cracking or breaking when curved region 16 is formed.

To allow tubes 12, 20 and wire 24 to be coupled to a power source within housing 14, the proximal end of wire 24 protrudes somewhat from that of tube 20 and the proximal end of tube 24 terminates distally from that of tube 20. Sleeves 22, 26 are truncated near the proximal ends of tubes 12, 20, respectively, so that they do not interfere with the electrical connections, which are shown somewhat schematically in Fig. 1. A jumper 34 connects wire 24 (i.e., the inner electrode) to the outer surface of tube 12 (i.e., the outer electrode). Leads 27, 28 respectively connect tube 20 (i.e., the center electrode) and wire 24 and tube 12 (i.e., the inner and outer electrodes) to a pair of connector pins 30, 32. The details of these connections are not shown but are fully described in the above-identified copending application.

Instrument 10 is coupled to a suitable, low voltage RF electrosurgical power source (not shown) via a cable (also not shown) that mates with pins 30, 32. One such source is a Wet-Field® II Coagulator available from Mentor O&O, Inc. of Norwell, Massachusetts, which is battery powered and produces a relatively low bipolar output voltage (such as 90 volts RMS under no-load conditions) . A low voltage output is preferred to avoid producing sparks across electrodes tubes 12, 20 and wire 24 at tip 18. Operation and Use

Referring to Figs. 3 and 4, electrosurgical instrument 10 is particularly useful in eye surgery procedures, such as surgery to relieve symptoms of glaucoma. Generally, instrument 10 is used to form a drainage path through the sclera with minimal trauma to the conjunctiva, a procedure described in detail below. Eye surgery begins with preparing the patient (e.g., cleaning the eye, applying a suitable local or general anesthesia) , and exposing the cornea and sclera with a lid retractor. The surgeon next inserts a very small, e.g., 30 gauge, hypodermic needle through the conjunctiva into the space between the conjunctiva and the sclera (shown in Fig. 4) , injects saline solution into the space to form a bleb and removes the needle from the eye. The small size of the needle minimizes trauma to the conjunctiva and reduces the risk that the conjunctiva will adhere to the sclera and block the drainage path.

Next, the surgeon prepares to insert instrument 10 into the eye. Using an appropriately shaped and sized scalpel, the surgeon makes a stab incision 50 at the junction of the cornea and sclera, approximately 6-7 mm from the bleb, through which tip 18 of instrument 10 will be able to pass. To avoid having to pass instrument 10 across the optical path (shown in Fig. 4) and risking contact with the delicate endothelial cells 62, the angle X between incision 50 and point 52 at which the sclera is to be pierced is relatively small, i.e., less than 90°, and preferably less than 60°. Also, to ensure that adequate space exists between the iris and the cornea for free passage of instrument 10, a clear, viscus elastomer, e.g., Healon™, is injected into the eye. Such an elastomer, which contains hyaluronic acid, is compatible with eye fluids and is routinely used in eye surgery as it not only enlarges the space between the iris and cornea, but also protects the cornea by coating it.

The surgeon next inserts tip 18 of instrument 10 through incision 50 and carefully directs tip 18 to the region of the sclera beneath the bleb. Instrument 10 is visible through the translucent conjunctiva, which facilitates the task of guiding instrument 10 through the eye. It is important to note that curved region 16 of instrument 10 allows the surgeon to guide tip 18 to the bleb by moving instrument 10 along an arc 60, rather than moving instrument 10 in a more linear path (such as would be required if a straight trephine or cautery needle were used and inserted at a more remote location, e.g., at position 50*) .

Thus, the surgeon inserts tip 18 through incision 50 with housing 14 oriented approximately vertically as shown in Fig. 4 and rotates instrument 10 along arc 60 to cause tip 18 to hook back and be positioned beneath the sclera under the bleb. The surgeon is thus able to avoid the optical path at the center of the cornea. As a result, the risk of instrument 10 contacting and possibly damaging the delicate endothelial cells 62 located on the underside of the cornea is significantly reduced. Endothelial cells 62 do not regenerate, and thus sight can be permanently affected if these cells are damaged by even slight contact. Once the surgeon has positioned tip 18 beneath the bleb, he or she brings tip 18 into contact with the tissue at the junction of the cornea and the sclera and orients tip 18 so that it will emerge into the bleb as it passes through the sclera. The surgeon then actuates the RF power source (such as with a foot-switch) while simultaneously placing slight pressure on instrument 10 to cause tip 18 to puncture the sclera and emerge into the bleb at puncture site 52. Care is taken to prevent tip 18 from contacting or piercing the conjunctiva. Referring also to Fig. 2, the application of bipolar energizing power to instrument establishes an electrical potential on tube 20 (i.e., the center electrode) that is opposite in polarity to the potential applied to tube 12 and wire 24 (i.e., the outer and inner electrodes, respectively) . Because the tips of the electrodes are axially spaced but relatively close together in the region of tip 18, electrical current 70 flows between tube 20 and wire 24, and between tube 20 and tube 12. It is important to note that the axial extent of the current flow (and thus the axial range of the cauterization effect produced by instrument 10) is larger than it would be if a pair of electrodes only (such as tube 20 and wire 24) were used.

As current 70 flows between tubes 12, 20 and wire 24, it cauterizes puncture 52 formed in the sclera, thereby significantly reducing the possibility that puncture 52 will close with scar tissue after surgery. Furthermore, the axial elongation of the cauterizing current ensures that the entire length of puncture 52 is cauterized quickly, and the surgeon need not partially withdraw tip 18 through puncture 52 to repeat the cauterization step. The cauterization also stops bleeding from blood vessels in the puncture area.

The power level of the RF source (which dictates the magnitude of current 70) is selected to be sufficient for cauterization but insufficient to damage surrounding tissue, such as the tissue of the cornea or iris. For example, with the aforementioned Wet-Field II power source, the selected power level is approximately 0.45 watts. To further minimize tissue damage, the surgeon relieves pressure on the tip 18 and deactivates the power source as soon as tip 18 is visible through the translucent conjunctiva as it emerges from the sclera. As a final step in the surgical procedure described above, which takes approximately 30 seconds or less, the surgeon removes instrument 10 from the eye. Aqueous fluid inside the eye is then free to drain through the path provided by puncture 52 into the bleb. Both the aqueous fluid in the eye and the saline used to form the bleb are then absorbed by the body's lymphatic system. Very little follow-up to the surgery is necessary. Incision 50 is sufficiently small as to be self-healing and it need not be sutured. Moreover, because puncture 52 is much smaller than a scalpel- created incision, the surgeon can puncture the sclera, for example, 6-8 times if necessary to effectively drain fluid from the eye.

Other embodiments of the instrument and surgical procedure are within the following claims. For example, referring to Fig. 5, bipolar electrosurgical instrument 70 includes only two electrodes, which are formed by a wire 72 coaxially disposed within a metal tube 74 and separated therefrom by an insulating sleeve 73. Wire 72 and tube 74 are respectively connected to pins 76 and 78. Instrument is otherwise constructed in the same manner as described above for instrument 10. Thus, instrument 70 can be used in the above-described surgical procedure. A curved region 75 helps ensure that instrument 70 is maintained out of the optical path of the eye during the procedure. When instrument 10 is energized with bipolar RF power, cauterization occurs between the tips of wire 72 and tube 74 at the tip 77 of instrument 70. Either of the instruments described herein may be used in retinal surgery to make punctures in the retinal wall to relieve pressure during surgery. The instruments may also be used to cauterize bleeding blood vessels during other types of glaucoma surgery, as well as for non-opthamological surgeries. The dimensions of such instruments would, of course, vary appropriately from those of the instruments described herein.

Claims

Claims 1. An electrosurgical instrument comprising at least three electrodes having proximal ends adapted to receive bipolar energizing potential, said electrodes having distal ends that are disposed at successive, axially spaced regions in a distal region of said instrument so that energizing current flows axially between said electrodes in said distal region.

2. The instrument of claim 1 wherein the distal end of a first one of said electrodes is axially disposed between the distal ends of second and third ones of said electrodes, said first electrode being connected to receive a polarity of said bipolar energizing potential opposite to the polarity received by said second and third electrodes.

3. The instrument of claim 1 wherein said at least three electrodes are arranged coaxially, said first electrode being disposed radially between said second and third electrodes.

4. The instrument of claim 3 wherein said distal region includes a sharpened tip.

5. The instrument of claim 2 wherein said electrodes are constructed to dispose said distal region at a predetermined angle with respect to a longitudinal axis of said instrument.

6. The instrument of claim 5 wherein said electrodes are curved to provide said predetermined angle.

7. The instrument of claim 2 wherein a first one of said electrodes comprises a tube insulatingly disposed within a second one of said electrode, and a third one of said electrodes is insulatingly disposed within said tube.

8. The instrument of claim 7 wherein said second electrode comprises a tube and said first electrode comprises a wire.

9. An electrosurgical instrument comprising at least two coaxial electrodes, said electrodes having proximal ends adapted to receive bipolar energizing potential and distal ends that are disposed at successive, axially spaced regions in a distal region of said instrument so that energizing current flows axially between said electrodes in said distal region, said electrodes being constructed to dispose said distal region thereof at an oblique angle with respect to a longitudinal axis of said instrument.

10. The instrument of claim 9 wherein said instrument includes at least three of said electrodes, the distal end of a first one of said electrodes being axially disposed between the distal ends of second and third ones of said electrodes, said first electrode being connected to receive a polarity of said bipolar energizing potential opposite to the polarity received by said second and third electrodes.

11. The instrument of claim 10 wherein said electrodes are curved to provide said oblique angle.

12. A surgical method comprising the steps of providing a bipolar electrosurgical instrument comprising at least two coaxial electrodes that extend generally along a longitudinal axis of said instrument, said electrodes being constructed to have distal ends disposed at an oblique angle with respect to said longitudinal axis near a distal tip of said instrument, inserting said distal tip of said instrument into a region of the body through an incision in a region remote from a desired puncture site; manipulating said instrument to bring said distal tip into contact with body tissue at said puncture site; and placing pressure on said tip of said instrument while applying bipolar energizing potential to said instrument to cause said distal tip to puncture said body tissue and cauterize said puncture.

13. The method of claim 12 wherein said region of the body is the eye.

14. The method of claim 13 wherein said body tissue is the sclera.

15. The method of claim 14 wherein said directing includes causing said distal tip of said instrument to contact the sclera at the junction of the sclera and the cornea.

16. The method of claim 15 further comprising forming a bleb in the conjunctiva over said puncture site by injecting fluid between the conjunctiva and the sclera with a hypodermic needle.

17. The method of claim 13 wherein said incision is at the junction of the cornea and sclera and is in the range of 6-7 mm from the puncture site.

18. The method of claim 13 wherein said energizing potential is at a level sufficient to cauterize said puncture without substantially damaging surrounding tissues in the cornea and iris.

19. The method of claim 13 wherein said electrodes are curved to dispose said distal tip at said oblique angle with respect to said longitudinal axis.

20. The method of claim 12 wherein said manipulating comprises directing said instrument in an arcuate path through the body to bring said distal tip into contact with body tissue at said puncture site.

21. The method of claim 12 wherein said region of the body is the eye, said oblique distal tip of said instrument being constructed to allow said instrument to be manipulated to bring said distal tip into contact with an area of the eye at said puncture site without passing said instrument into an optical path of the eye.

22. The method of claim 12 wherein said distal ends are disposed at successive, axially spaced regions at said distal tip of said instrument so that energizing current flows axially between said electrodes at said distal tip.

23. The method of claim 22 wherein said electrodes are arranged coaxially.

24. The method of claim 12 wherein said instrument includes at least three of said electrodes, the distal end of a first one of said electrodes being axially disposed between the distal ends of second and third ones of said electrodes, said first electrode being connected to receive a polarity of said bipolar energizing potential opposite to the polarity received by said second and third electrodes.

25. The method of claim 24 wherein said electrodes are arranged coaxially.