CA2183103A1

CA2183103A1 - An electrosurgical procedure recurving the cornea

Info

Publication number: CA2183103A1
Application number: CA002183103A
Authority: CA
Inventors: Thomas A. Silvestrini
Original assignee: Individual
Current assignee: Keravision Inc
Priority date: 1994-02-09
Filing date: 1995-02-06
Publication date: 1995-08-17
Also published as: US20020049437A1; AU1700395A; IL112576A0; TW274514B; BR9506762A; IL112576A; AU686743B2; US5766171A; MX9603274A; SG52621A1; WO1995021578A1; JPH09511161A; CN1143900A; EP0743838A1; KR970701021A; EP0743838A4

Abstract

This invention is a device and procedure for the correction of optical abnormalities in a human eye. It involves use of an inventive electrosurgical energy probe (200) with specific physical configurations (204). The process preferably utilizes a high frequency R electro-desiccation or ablation device. The procedure involves the initial step of forming at least one access site allowing access to the corneal volume behind the Bowman's layer. It preferably is placed in the anterior surface of the cornea through and ending posterior to the Bowman's layer of the eye. The electrosurgical probe is then introduced into the access site and, depending upon the visual abnormality to be corrected, the probe is activated to adjust the volume of the corneal stromal layers through ablation or desiccation. For instance, if the optical aberration to be alleviated is hyperopia, a circular corneal volume reduction taking place about the outer periphery of the corneal mass may be accomplished. In certain circumstances, Bowman's layer may be cut to allow the curvature of the cornea to change after the corneal volume adjustment. These relief cuts may be radial, circular, semicircular or any other form appropriate for the option adjustment needed.

Description

~ WO 95/21578 2 1 8 310 ~ - 1 - r~ s - l6l3 AN ELECTROSURGICAL PROCEDURE RECURVING THE CORNEA

Field of the Invention This invention iB a procedure for the correction of optical abnormalities in a human eye. It involves use of an electrosurgical energy probe which may 5 be of a specific physical configuration as outlined below. This invention also includes suitable electrodes for performing the noted process. The process preferably utilizes a high fre5~uency RF electro-desiccation or ablation device. The procedure involves the initial step 20 of forming at least one access site allowing access to the corneal volume behind the Bowman' 8 layer. It (the access site) preferably is placed in the anterior surface of the cornea through and ending posterior to the Bowman' 8 layer of the eye. The electrosurgical probe is 25 then introduced into the access site and, ~l-oren~l ns upon the visual abnormality to be corrected, the probe is activated to adj ust the volume of the corneal stromal layers through ablation or desiccation. The shape of the volume desiccated or ablated is ~ Q~ upon the 30 aberration to be corrected. For i~stance, if the optical aberration to be alleviated is hyperopia, a circular corneal volume reduction taking place about the outer periphery of the corneal mass may be accomplished. In other instances, such as for the treatment of 35 astigmatism, certain smaller sections of the peripheral wo 95/21578 ~ Q3 ` - PCT/US95/01613 corneal volume may be 9hrunk. In certain circumstance6, Bowman' 9 layer may be cut to allow the curvature of the cornea to change after the corneal volume ad~ustment.
These relief cuts may be radial, circular, semicircular 5 or any other form appropriate for the optical adjustment needed .
Backcrround of the Invention Anomalies in the overall shape of the eye can cause visual disorders. Hyperopia ("farsightedness~) occurs when the front-to-back distance in the eyeball is too short. In such a case, parallel rays originating greater than 20 feet from the eye focus behind the retina. In contrast, when the front-to-back distance of 15 eyeball is too long, myopia ("nearsi~hte~ln~n) occurs and the f ocus of parallel rays entering the eye occurs in front of the retina. Astigmatism is a condition which occurs when the parallel rays of light do not focus to a Eingle point within the eye, but rather have a variable 20 focus due to the fact that the cornea refracts light in a different ~ n at different distances. Some degree of astigmatism is normal, but where it is pronounced, the astigmatism must be corrected.
E~yperopia, myopia, and astigmatism are usually 25 corrected by glasses or contact lenses.
Another method for correcting those disorders is through the impl~nt~t;~n of polymeric ringa (intrastromal corneal rings or "ICR's") in the eye~s corneal stroma to change the curvature of the cornea.
30 Previous work involving the impl:-nt~?,ti-~n Of polymethyl ~h~crylate (PMMA) rings, allograft corneal ti8sue, and hydrogels is well do~_ ~P~. One of the ring devices involves a split ring design which is inserted into a channel previou81y dissected in the 35 stromal layer of the cornea. A min;m~lly invasive WOgS/21578 ~18 3 ~ 0 3 PCTIUS9~101613 incision is used both for producing the channel and ~or ~-inserting the implant. See, for instance, the use of PMMA intrastromal rings in U.S. Patents Nos. 4,452,235 to Reynolds; 4,671,276 to Reynolds; 4,766,895 to Reynolds;
and 4, 961, 744 to Kilmer et al .
Surgical methods for the correction of such disorders are known. Such methods include radial keratotomy (see, e.g., U.S. Patents Nos. 4,815,463 and 4,688,570) and laser corneal ablation (see, e.g., U.S.
Patent No. 4,941,093) .
There are other procedures for reshaping the surface of the cornea. Some involve surgery; others do not. Two patents dealing with the nonsurgical reshaping of the cornea are U.S. Patent Nos. 4,326,529 to Doss, et al. and 4,381,007 to Doss. ~30th of these patents deal with the use of radio frequency energy to reshape the cornea of an eye. These involve the use of RF probes which are introduced non-invasively onto the cornea.
They each involve an RF generating source which is placed on the anterior surface of the cornea and utilize saline solution to cool the corneal surface as the radio frequency current enters the eye. The RF apparently heats various stroma within the cornea and thereby reshapes the cornea as a biological response to the heat produced by the RF.
Other invasive l~phth~lm;c surgical devices include U.S. Patent No. 4,805,616, to Pao, which patent describes a bipolar probe device may be used in orhth~lm;c gurgery. The device is only described in the performance of anterior capsulotomies. In that C~UL~ a limbal ;nC;~;nn is made and the active probe tip is inserted between the anterior capsule of the eye~ s lens and the corneal endothelium. The anterior capsule is sequ~t;~lly coagulated, becomes extremely friable, and then is removed by mechanical penetration with an Wo 95121~78 PCTIUS9~/01613 2~3~3 ~4~
additional mechanical device. No mention of treatment of a cornea is found.
Similarly, two patents to Easley et al ., U. S .
Patent Nos. 5,201,730 and 5,203,353, show devices for 5 penetrating and working in the vitreous humor of an eye using combination stripping tools and aspirators. The disclosed instrument may also have a bipolar diathermy device with an exterior needle surrounding and coaxial to a f iberoptic member . The diathermy device is u6ed only 10 to coagulate bleeding vessels found on the retinal surface or beneath preretinal membranes. No mention of treating the cornea is mentioned.
Two related applications, U.S. Patent No. 5,025,811 to Dobrogowski et al., and 5,174,304, to 15 Latina et al., show noninvasive methods for focal transcleral destruction of living human eye tissue. In general, these devices and their underlying procedures involve the use of electric currents for ablating eye tissue, particularly the ciliary process. Again, no mention of cornea treatment is seen.
This invention involves the introduction of an electrosurgical probe into the layers of the cornea to modify local sections of that corneal mass.
There are a variety of electrosurgical devices known. For instance, Hetzel, U.S. Patent No. 4,033,351, shows a bipolar cutting electrode for high frequency surgery. The electrode shows what is said to be an improved electrotie design having a number of metal tips.
U.S. Patent No. 4,202,337, to Hre~ et al., shows a 8imilar electrosurgical device for cutting or coagulation. It has a n~nt~r~n~ ct;ve handle with a })lade assembly having a number of electrodes and an insulation member separating the various electrodes.
A similar and related patent to Degler Jr.
35 et al , U. S . Patent No . 4, 228, 800, shows an Wo 95121578 2 l 8 3 l 0 ~ - 5 ~ ~ - PCT/US95/01613 electrosurgical knife in which the blade assembly has a center electrode of specified thickness, insulation members secured to the center electrode, and a number of side electrodes secured to the insulation members. None of these devices discuss practice of a surgical procedure upon the posterior regions of a cornea.
U.S. Patent No. 4,799,478, to Fedorov et al.
teaches a device f or the coagulation of biological tissues, preferably corneal tissue. The device disclosed by Fedorov et al. appears to be merely a heating device with a manner of carefully controlling the depth to which the heater or coagulator is introduced. The device is said to be useful for coagulation of biological tissue and the concept of changing " the curvature " of ~ eye tissues, e.g., cornea" is noted. The patent -inn~ the need for high accuracy to reach the goal of "to carry out coagulation of the eye cornea to a specific depth. "
Although it is not clear what result Fedorov et al.
wishes to obtain in this first patent, Fedorov et al. in U.S. Patent No. 4,907,587, -- ~nn~ the use of therm~l coagulation of the cornea along certain corneal surfaces to correct various optical aberrations in the eye. It should be noted that neither of these patents suggests the use of ~hl~t;~n or desiccation from the reverse side of the Bowman~ 8 layer to effect any c~ange in the anterior corneal surf ace .
!}Lma~r of the Invention This invention is a method of altering the shape of the cornea, often, the anterior surface curvature of the cornea. The invention also includes certain electrosurgical probe configurations useful in this process. The procedure, in its preferred variations, does not entail sign;fi~nt surgical modification of the anterior corneai surface or of the Wo 95121578 PCT/US95/01613 2~ 03 -6-Bowman'~ layer of the eye, except, in certain ~ituations, adding surface incisions to act either as a stress relief function or to provide access for the electrosurgical probe .
An electrosurgical probe is a signif icant portion of this invention. It is used, preferably in desiccation or ablation mode, to change the volume of the mass of the cornea posterior to the Bowman' s layer and found in the stromal regions of the cornea. By selectively modiying the volume of these regions, small amounts of the cornea may be controllably removed or shrunk and, upon removal of the electrosurgical probe from the cornea, the curvature of the anterior surface of the cornea will have changed and the refractive path of light entering the eye will be changed. As noted above, surface incisions may later be added to permit the anterior of the cornea, in particular, Bowman' 8 layer, to conform to the underlying corneal tissue removal (volume change), thereby allowing for change in anterior corneal 2 0 curvature .
The inventive procedure may be used for the treatment of hyperopia (farsight.o~ln~o~R) or myopia. In this procedure, a small inA;~ n or access site may be made in the anterior surface of the cornea, which incision extends down through the Bowman' 8 layer or through the sclera and into the intrastromal volume of the cornea. An ele.:l Lo~uLyical probe, may be introduced through the ' n~; ~; on and guided around within the corneal stroma f rom the outer periphery of the cornea .
Activation of the electrosurgical probe in an ablation mode will cause vaporization of the regions of the cornea adj acent to the active areas of the probe . Activating the probe in a desiccation mode will shrink or necrose the region of the cornea adj acent to the active areas of 35 the probe. After an appropriate necrosis, removal or Wo 95121578 ~1~ 3 ~ ~ ~ r~ 613 shrinking of material is accomplished, the probe is removed and the anterior surface then relaxes to conform to the collapse or shrinkage of tissue formed by electrosurgical treatment of the corneal stromal tissue.
In some instances, a modest incision in the anterior of the cornea may be desirable to allow curvature relaxation of the corneal anterior surface.
Another pref erred procedure includes the alleviation of astigmatism by similar procedure. Small partial depth incisions may be made into the anterior surf ace of the cornea through Bowman ' 8 layer or through the sclera adjacent to the cornea to get under Bowman' 8 layer, but not reaching 80 far as the posterior corneal surf ace or the anterior chamber . In a general sense, these initial inr;~;nnC are made in the regions of the cornea or sclera to allow the electrosurgical probe to reach the corneal mass below the anterior surf ace which must be reduced to produce a symmetric corneal surface.
In any event, an electrosurgical probe is then introduced through the lnn;cinnC and a selected amount of material is removed or desiccated to alleviate the nonregularity of the corneal anterior surface.
Also as a part o~ this invention are certain r, bipolar, and se8quipolar electrosurgical probe designs which are especially suitable for producing the specif ic tissue removal patterns desired in this procedure .
Brief Descri~tion o~ the Draw; n~c Figure l is a schematic illustration of a horizontal section of the eye.
Figure 2 is a schematic illustration of the anterior portion of the eye, showing various layers of the cornea.

-Wo 95121578 PCTIU595/01613 2~ 83~3 -8-Figures 3A to 3E show a schematic proces~ for treatment of hyperopia using the procedure of this invention .
Figures 4A to 4D show schematic diagrams Qf 5 astigmatic and normal eyes.
Figures 5-ll A and B show top and side views o~
inventive circular RF electrosurgical probe8.
Figures 12-l9 A and B show top and side views of inventive straight RF electrosurgical probes.
Figures 20 A and B and 21 A, B and C show top (A and C) and side (B) views of inventive disc and washer RF electrosurgical probes.
Figure 22 shows a desired return electrode for the sesquipolar Frobes of the other Figures.
Figures 23 A-G are 8~ t; C diagrams showing top views of eyes wherein various processes for electrosurgically altering corneal curvature have been carried out.
20 Description of the Invention Prior to PYI'l~in;n~ the details of the inventive procedures and device8, a short explanation of the physiology of the eye is needed.
Figure l shows a horizontal cross - section of 25 the eye with the globe (lO) of the eye resembling a sphere with an anterior bulged spherical portion representing the cornea (21).
The globe (lO) of the eye consists of three cnnrPntriC coverings Pnf~1 ns; n5 the various transparent 3 0 media through which the light must pass bef ore reaching the light-sensitive retina (82). The outermost covering is a fibrous protective portion the po8terior five-sixth8 of which is white and opacaue and called the ~clera (13), and sometimes ref erred to as the white of the eye where ~ WO95/21578 1~3~ 9 PcrluS9S/01613 ~ r visible to the front. The anterior one-sixth of this outer layer is the transparent cornea (12) .
A middle covering is mainly vascular and nutritive in function and is made up of the choroid, ciliary body (15), and iris (17). The choroid generally functions to r-;n~ n the reti~a (18). The ciliary body (16) is involved in suspending the lens (21) and acc - ~tion of the lens . The iris (17) is the most anterior portion of the middle covering of the eye and is arranged in a frontal plane. It is a thin circular disc similar in function to the diaphragm of a camera, and is perforate near its center by a circular aperture called the pupil (19). The size of the pupil varies to regulate the amount of light which reaches the retina (18). It contracts also to acc ~-tion, which serves to sharpen the focus by ~;m;n;~h;n~ spherical aberration. The iris divides the space between the cornea ( 12 ) and the lens (21) into an anterior chamber (22) and the posterior chamber (23). The innermost portion of covering is the retina (18), consisting of nerve elements which form the true receptive portion for visual impressions.
The retina (18) is a part of the brain arising aa an outgrowth from the fore-brain, with the optic nerve (24) serving as a fiber tract connecting the retina part of the brain with the fore-brain. A layer of rods and cones, lying just beneath a pigmented epithelium on the anterior wall of the retina serve as visual cells or photoreceptors which transform physical energy (light) into nerve impulses.
The vitreous body (26) is a transparent g~ tinr~ mass which fills the posterior four-fi~ths o~
the globe (11). At its sides it supports the ciliary body (16) and the retirla (18). A frontal saucer-shaped depression houses the lens.

Wo 9~/21578 ' PCrlllS95/01613 ?,~S3~3 -lo- --The lens (21) of the eye i8 a transparent bi-convex body of crystalline appearance placed between the iris (17) and vitreous body (26). Its axial diameter varies markedly with accommodation. A ciliary zonule 5 (27), consisting of transparent fibers passing between the ciliary body (16) and lens (21) serves to hold the lens (21) in position and enables the ciliary muscle to act on it.
Referring again to the cornea (12), this 0 outermost fibrous transparent coating resembles a watch glass. Its curvature is somewhat greater than the rest of the globe and is ideally spherical in nature.
However, often it is more curved in one meridian than another giYing rise to astigmatism. Most of the 15 refraction of the eye takes place through the cornea.
Figure 2 is a more detailed drawing of the anterior portion of the globe showing the various layers of the cornea ~12) making up the epithelium (31).
An anterior limiting lamella (33), referred to 20 as Bowman' s membrane or layer, is positioned between the epithelium (31) and the stroma (32) of the cornea. When I refer to the "corneal mass, " I mean the various stroma (32) between the Bowman's layer (33) and the Descemet's membrane (34). The corneal stroma (32) are made up of 25 l~ P having bands of f ibrils parallel to each other and crossing the whole of the cornea. While most of the fibrous bands are parallel to the surface, some are obliqùe, ~per;~lly anteriorly. A posterior limiting lamella (34) is referred to as Descemet's membrane. It 30 is a strong membrane sharply defined from the stroma (32) and resistant to pathological processes of the cornea.
The endothelium (36) is the most posterior iayer of the cornea and consists of a single layer of cells and function to ~-in~;n transparency of the cornea 35 (12). These epithelial cells are rich in glycogen, W095/21578 1~3~ - PCT/US9S/01613 enzymes and acetylcholine and their actlvity regulates the transport of water and electrolytes through the of the cornea ~12). The limbus (37) i8 the transition zone between the coniunctiva (38) and sclera 5 on the one hand and the cornea ( 12 ) on the other .
There are a variety of different electrical surgical delivery probes which would be suitable in this invention. In general, there are two distinct electrosurgical delivery probe types: the monopolar lO probe and the bipolar probe. An in-between electrosurgical configuration applicable to this invention also exists and is known as sesquipolar. In each instance, some section of the human body i9 used to complete a circuit between one pole and the other. In 15 the monopolar probe device, there is a single active contact which is inserted or otherwise contacted with the human body and it is the site at which some body activity, e.g., desiccation, ablation, necrosis, fulguration, or the like, takes place. To complete the 20 circuit in a monopolar device, there must be another contact which is inactive and placed against the body in a location from the active contact. By ~inactive~ is meant that only an insignif icant temperature rise occurs at that contact point. One such method of insuring that 25 the inactive electrode is in fact "inactive~ is to make it quite large in area. This causes the current to spread over a large area for completion of the circuit.
A bipolar electrode typically has two equal area active electrodes c~nt~;nPd in the same electrode 30 probe-handle structure. This symmetric bipolar electrode design produces a significant temperature rise at both electrodes .
- In a monopolar or sesquipolar configuration, only one electrode has an area of tissue contact 35 producing significant temperature rise. Unlike the WO 95/21578 PCr/US95101613 ~
~3~ ~3 - 12-monopolar conf ir,uration, however, the sesriuipolar return electrode is not 80 remote, and thereby limits current f low through the body to the nearby return electrode .
The return electrode area in the 6es~uipolar configuration electrode is usually at least three times the area of the active electrode and produces little or no tissue effect. In some designs, the ses~uipolar return electrode may be found on the electrode probe-handle structure while on other designs it may be lO separately located in a non-remote region of the body.
There are a variety of ef f ects that may occur depending upon the electrosurgical mode desired. For instance, there are both high temperature and low temperature des;rrati~n effects when the active 15 electrosurgical probe contact (8) are used to promote tissue desiccation. The resistance of the tissue in contact with the active probe electrode obviously varies with the tissue temperature and water content o~ the tissue. A low temperature desiccation effect involves 20 heating such that the temperature-time product causes tissue necrosis with little; 'liAt~ denaturation or discoloration of the tissue. A high temperature desiccation includes heating tissue near the conducting probe contact to approach or slightly exceed 100C. In 25 the low temperature variation o~ this procedure, there is a transient decrease in local tissue; - l~nre with little drying of tisaue. But in the high temperature variation, there are signi~icant increases in local tissue; - ~nre and also sign; f iC~n~ in local tissue 3 0 desiccation .
In the ablation mode, the electrosurgical energy density delivered largely causes the tissue near the probe contact to vaporize. The temperature at the electrode/tissue interface is increased significantly 35 past the point of steam ~ormation. The effect of WO95/21578 2183 ~ ~ PCT/US95/01613 1 3-- ~ -electrical resistance Yaries during a Epecific radio frequency (RF) cycle and although there is sparking, carbonization is not usually significant and the effects of the device are relatively rapid.
~lectrosurgical ablation and cutting produce an effect where a thin layer of tissue is vaporized ~cutting) or where a larger section of tissue is vaporized (ablation). The line between "cutting~ and "ablation" is not always clear.
In the procedure specified below as the invention, a preferable procedure for this invention is via the operation of electrosurgical probes operated in cutting, ablation, or desiccation mode. Herein, when I
refer to the term ~'volume change" or ~'volume modification" when referring to the material in the corneal mass, I mean the corneal mass is either necrosed, desiccated, or ablated.
It is quite rare that the current flow through the device is DC. The current is typically a very high frequency alternating current, typically in the range of -500 Hertz or more. Additionally, the RF energy is often delivered in a pulsed or in a more cnrlt;n1lous, non-pulsed operation ~l~pF.n~in~ on the exact effects desired. Some residual heating will take place no matter which course i8 taken.
With this lengthy background in place, please refer to Figures 3A through 3D. This series of figures shows, in 8r~ t;c fashion, one pIuceduLe for treating hyperopia (fars;~htP~in~s), myopia, or astigmatism. This schernatic p~ocedu-e shows features which may be common to all of the processes of this invention. Generically, the procedure includes the step of producing one or more ;n~-;q;~nc, often towards the periphery of the cornea.
These ;n~ ;R;on~ penetrate Bowman's layer in the anterior surface of the cornea and extend down into, as defined Wo 95121578 PCrlUS95/01613 2~ ~.83~3~ -14-above, ~ the corneal mass or corneal volume r I also contemplate that the electrosurgical probe may be inserted into the corneal volume without penetration of the anterior surface cornea, e.g., by access through a 5 partial depth incision made in the sclera next to the cornea. In any event, if an anterior access partial depth incision is contemplated, an optional step at this point may be the insertion of a non-electrosurgical lamellar separator to separate the various stroma 0 1. -1 l AP within the cornea at the depth of the entry i n~ n . This allows the subsequent step of inserting the electrosurgical probe to take place with greater ease. The probe itself may serve the function of intrAli -llAr separator, if so desired. The 15 electrosurgical probe is introduced into the stromal lamellar cavity 80 produced. Depending upon the design of the inserted electrosurgical probe and on the refractive effect desired, the probe is moved inside the intralamellar space previously formed and activated to 20 desiccate or ablate specific geometric regions of the cornea. Desirably, after the completion of the corneal volume ablation or desiccation step, the curvature of the corneal surface is then measured. The procedure may be repeated if insuf f icient correction has occurred . If 25 needed, Bowman' 8 layer and a small amount of underlying stromal tissue may be lightly cut on the anterior surface adjacent to or above the site of the volume reduction to allow the Antprir~r corneal surface to change.
R~tl~rninS to the specifics of Figures 3A to 3D, 30 Figure 3A shows an eye (lO0) having a pupil ~lO2) and a cornea (104). In the outer radius of cornea (104) is found two small partial depth incisions (106) which have been cut through 30wman~ s layer into the corneal mass as shown in Figures 1 and 2. These incisions may be cut WO95/21578 2~ 3 PCTrl~S9S/01613 radially or circumferentially and are shown for discussion purposes to be radial.
It should be understood, however, that although two access partial depth incisions (106) have been portrayed in Figure 3A, the number of such acces6 sites (106) is not important. If a semi-circular lamellar separator (108) as shown in Figure 3B is used, then the number of access sites (106) may be desirably two in number. If ] l l ;~r separators of shorter arc segments o are used, more numerous slits may be desired. If a nearly circular lamellar separator or electrosurgical probe is used, a single access site (106) may be suf f icient .
Figure 3B shows the introduction of the optional dissector blade or l; ll~lr separator (108) to separate the lamella f ound in the cornea . The separator (108) is rotated until a circular channel is made in the corneal periphery, and is rotated back out of the eye. A
similar procedure takes place on the other access site as shown in Figures 3A and 3B. Figure 3C shows the insertion of an electrosurgical probe into the route formed in the intrastromal region shown in Figure 3B.
The probe may be energized following complete insertion or may be energized in a stop, move and activate mode.
The step of removing and/or shrinking tissue is ~ n~ i nllPd until sufficient tissue has been ablated or desiccated to achieve the desired refractive effects.
Figure 3D shows the eye (lO0) after completion of the ablation procedure. It may be desirable to place a small stitch (112) in any access site (106) in the cornea to ensure healing of the access site and minimize the potential for infection. Figure 3E shows the eye (100) following relief cuts (114) that may be necessary in some instances to allow the anterior corneal surface to more closely conform to the underlying corneal tissue WO 95121578 ~ 3~ 16 - PCTIUS9~1û1613 removal ~volume change) thereby allowing for greater change in anterior corneal curYature. These relief cuts may be circumferential as shown or they may be radial depending on the desired refractive effect. Further, the 5 relief cuts may be rnnt; n11r11~ or may be interrupted as shown. In any case, these cuts will be shallow cuts such that they penetrate Bowman' 8 layer and possibly a portion of the underlying corneal stroma.
The above-description generally indicates the lO method of the present invention. Specific probe configurations and method of treatment will be described in the Examples below.
It should be apparent from the description above, that the step of desirr~t;n~, necrosing or 15 ablating the tissue from within the corneal mass lessens the volume of that mass in specific regions of the cornea. Conser~uently~ the anterior sections of the cornea will become flatter or steeper and will alleviate the improper previous refraction of light. Some of the 20 possible changes in corneal th; r~n~s and their relationship to the radius of curvature of the central corneal surface are described in Jose R~rraruer: Father of Modern Refractive ~erato21astY, in Refractive and Corneal Surgery, Vol. 5, May/June 1989, pages 177-193, 25 which is hereby incorporated by reference in its entirety. This paper de8cribes the so-called "Law of Thickness" which indicates that when corneal volume is reduced in the periphery, central corneal ste~p~n; nr occurs and when a volume of tissue is removed in the 30 center, central corneal flattening occurs. The inventive electrosurgical method and devices aim to reduce corneal volume in controlled geometric areas o~ the corneal stroma to achieve refractive correction.
The method and devices of the present invention 35 may also be useful in the treatment of astigmatism.

~ Wo 95/21578 ~2 ~I 83 ~ ~3 -17- PCr/US9Sl01613 Astigmatism occurs, generally, when the curvature of the anterior surface of the cornea i8 not regular as one passes about the meridians on the anterior surface of the cornea resulting in a steep and flat axis (the astigmatic 5 axis). Figure 4A and 4B are schematic perspective views that show an astigmatic and normal eye, respectively. In an astigmatic eye, two axes are generally identified, corresponding to the steepest (120~ and flattest (122) axis of curvature. The steepest axis is also known as the axis of astigmatism (120). To correct astigmatism using this invention, one must flatten the curvature of the astigmatic axis such that the cornea becomes reasonably symmetrical and more spherical. Figure 4B
shows a normal eye, that is, one in which the curvature of all axes are the same. Figures 4C and 4D show schematic topographical curvature maps of an astigmatic and of a non-astigmatic eye, respectively. In Figure 4C, region 130 is the steep region where as region 132 is f latter .
Other configurations of access sites and controlled removal of corneal tissue are apparent. These will be discussed for particular applications in the Examples below. Further, It should be apparent to one appre~;At;n~ the design of such electrosurgical RF
25 probes, that the shape need not be nearly circular. It may be, much in the same way as were the ~ qr separators (108) in Figure 3B, that the probes have lesser arc length or are straight for alleviating hyperopia. In fact, for treating hyperopia or other ~l A~ , the probe may be of any convenient shape designed to ablate the tissue at hand. Such shapes will be discussed in more detail below. Further it may be noted that the handles of the probes may be straight or bent. A bent handle may allow greater facility of use within the small confines found behind an access site as WO95/21578 ~,~83~ -18- ; PCTrUS95/01613 shown in the above drawings. Additionally, the procedures and devices of the present invention may be useful in the treatment of more than one indication, for example myopia and astigmatism or hyperopia and 5 astigmatism.
Figures 5-11 A and B show top (A) and side (B) views of circular electrosurgical probes suitable for use in the 8eh t ~ procedure described above . Figures 5A
and B show a circular RF electrosurgical probe with two 10 active sites that operate in monopolar or sesquipolar modes. The probe (200) includes a shaft (202) and two active siteE3 (204), each active site having an arc of less than about 180, preferably less than about 90.
The single source of RF energy (206) is fed in through the ;n~ tt~r (208) making up the probe (200). Figures 6A and B show a circular RF ele~ u, yical probe (210) with a single active site (212) at the tip. Again, the single source of RF energy (214) is fed in through the insulator making up the probe. Figure 7A and 7B show a circular RF electrosurgical probe (220) with a single active site (222) ~Ytl~ntl;n~ the length of the circular portion of the probe. Once more, the single source of RF
energy (224) is fed in through the insulator (226) making up the probe. Figures 8A and B show a circular RF
electrosurgical probe (230) with two active sites (232) near the tip of the probe that operate in bipolar fashion. Two sources of RF energy (234 and 236) are fed in through the insulator (238) making up the probe.
Figures 9A and B show a circular RF electrosurgical probe (240) with a single active site (242) near the tip, the active site shown in Figure 9A to be on the top part of the probe. A single source of RF energy (244) is fed in through the insulator (246). Figures 10A and B and llA
and show other circular RF electrosurgical probes (250 35 and 260 respectively) with 8ingle active 8ites (252 and wos~/tls78 2t83~tO3 -19- = PCT/US9S/01613 262 respectively) near the tips of the probes. A single source of RF energy (254 and 264) is fed in through each probe. Figure lOB shows the active site (252) to be located at the tip but exposed on one side and Figure llB
shows the active site (262) to be located at the tip but insulated on the top and thus exposed on one side only.
Both probes depicted in Figures lO A and B and 11 A and B
are designed to contact tissue in either the f orward or retracting direction to the active site on the probe, the retracting direction.
Figure 12-l9 A and B show top (A) and side ~B) views of straight ele~-,u~u,yical probes suitable for use in the schematic procedure described above. Figures 12A
and B shows a straight RF surgical probe (300) with a single active site (302~ PYt~n~lin~ along the length of the probe. A single source of RF energy (304) is fed through the probe. Figures 13A and B show a straight RF
electrosurgical probe (310) with two active sites (312) ~Yt~on~i~nS along the length of the probe that operate in bipolar fashion. Two sources of RF energy (314 and 316) are fed in through the insulator (318) making up the probe. Figures 13-19 A and B show other straight RF
electrosurgical probes with single active sites near the tips of the probes. A single source of RF energy is fed in through each probe. Figures 14 A and s show the active site (322) to be located near the tip of the probe (320) and on top of the probe such that the active site is raised and pointed in the retracting direction of the probe. Figures 15A and B show the active site (332) similarly located near the tip of the probe. The end of the probe is raised and the active site (332) is located on the raised part of the tip pointing backwards, the active site being exposed on two sides. Figures 16A and ~3 similarly show the active site (342) raised at the end of the probe pointing backwards (340), but the active wo gs/2ls78 ~3~ 3 ' PCT/US95/01613 site is imbedded in the insulatin~ curve of the probe, thereby exposing the active site on one side only.
Figures 17A and B show the active site (352) at the tip of a straight probe ~350), the active site being exposed 5 on one side on the tip portion alone. Figures 18A and B
show the active site (362) near the end of a straight probe (360). The probe is hrn~ n~d at the active site.
Figures l9A and B again show a straight Æ
electrosurgical probe (370) with a curved tip, with the 10 active site (372) again raised and pnintin~ backwards and slightly upwards the active site being exposed on one side on the tip portion alone. However, in this pmhor~;- t active site is angled such that a portion (374) of the active site (372) extends beyond the curved 15 tip. In this design, the ablation or desiccation takes place either as the device is pushed forward or as it is pulled backwards, or retracted from the lamellar separation channel. Upon e~O:iuLe tQ tissue and electrode activation, the active site will vaporize or 20 desiccate the tissue. It may be desirable to provide a second l; 11 ;lr channel to allow for the for the relief of gases produced by the probe when used in the ablation mode or to incorporate grooves in the probe portions that insert into the tissue to allow the escape of gases so 25 produced.
Figures 20 and 21 A and B show top (A) and side (B) view of RF electrosurgical disc and washer probes (400 and 410 respectively) . A single Æ energy source is fed through each probe. The disc probe (400) is a 30 circular probe with a circular active site (410). The washer probe (410 ) i8 a circular probe with a circular active site (412) with a hollow middle (~14). Each of these probes may have a flat surface as shown in Figures 20A and 21A or may be curved to conform to the curvature w095l2l578 21831Q3 ~ . s i6~3 .
of the cornea. The disc probe may have a wire loop surface (415) as shown in Figure 21C.
The above described probes are usef ul in the particular examples discussed below. The Examples are 5 illustrative only and are not intended to limit the scope of the invention. For the probes that have only one conducting lead to deliver RF energy ( i . e . monopolar or sesquipolar) a return electrode is necessary. In some instances this may be placed remotely on the body. In 10 other cases, the use of a sesauipolar return electrode may be desired using a return electrode that is placed onto the sclera or tr~n~ 1 area of the cornea.
Figure 22 shows a desirable manner for placing a sp~]irol~r return electrode on the exterior of the 15 cornea, or onto the sclera (344). This return electrode may simply rest on the cornea or sclera as shown or may be held in place by a vacuum att~cl t cavity built into the electrode. As noted above, the area of this return electrode (342) where it contacts the eye is without much 20 exception constant. Because of its significantly higher area as compared to the active tissue contacting electrodes described above, the tendency for the return electrode (342) to heat to a significant degree is minimized. The s~ u;rol~r electrosurgical system 25 described above is an embodiment of this invention that can enhance the safety of this oph~h~ 1 o~ic operation.
The following Examples are; nt.on~iPd to describe particular ~ho~; ~ of the invention but are in no way ; nt-.n~d to limit the invention in any manner.
F ~es Exam~le 1 - The Correction of Astiamatism In order to correct the astigmatic eye shown in Figures 4A and 4C such that it becomes more similar to 35 that shown in Figures 4B and 4D, a process similar to Wo 95/~1578 PCT/US95/01613 ~ 3i~.~3 -22-that de~cribed i~bove with regard to Figures 3A-3D i5 carried out. As shown in Figures 23A and 23C, radial or circumferential partial depth incisions (500) are made in the periphery of ~ the cornea . A l i - l l iqr separator i9 inserted to create a zone of separated lamellae (502) and (504) for the insertion of the electrical probe.
Two different approaches are possible to correct the astigmatic eye . In the f irst approach shown in Figure 23C the radial partial depth incisions and radial zone of separated l i ~ P will be formed beneath the astigmatic axis (506~. Following separation of the lamellar tissue, one of the straight RF probes shown in Figures 14-19 A and B is inserted through the partial depth incision (500~. The probe i5 then activated to change the paracentral corneal volume ~508~, that is the volume near the center of the cornea, by ablation of the tissue under the figure-8-shaped astigmatism shown in Figure 23A and 23C. The choice of RF probe design is ~ r~n,i~nt on the amount of tissue to be ablated. Once ablation is completed, the probe is withdrawn. Relief cuts on the iqnt~ri or cornea may be n~c~Ary as described above to allow the surface of the cornea to conform to the underlying tissue removal. In this way, the steep astigmatic axis is flattened such that the cornea becomes r~iq~niqhle symmetrical and spherical.
A second approach to the treatment of an astigmatic eye is to steepen the f lat astigmatic axis as shown in Figure 23A. In this approach, the l i l l iqr separation zone will be formed in the periphery of the cornea (502). The partial depth incision (500) is placed in the corneal periphery, beneath the astigmatic axis.
Following separation of the l: ~lliqr tissue, one of the circular RF probes shown in Figures 5, 6, 8, 9, 10, and 11 A and B, probes (200), (210), (220), (230), (240), 35 (250) and (260) respectively, is inserted through the WO95121578 183~ fl3 PCT/USs~/0lGI3 --23~--partial depth incision (500) The probe i3 then activated to change the volume by desiccation (probes (200), (210), (230), (240), (250) or (260) ) or by ablation (probes (210), (240), (250), or (260) ) of the 5 tissue (501) under the flat axis of astigmatism axis (507) as shown in Figure 23A. Thus some probe configurations can be used either in the ablate or in the desiccation mode. Probe (200) is operated by inserting it into the lamellar tissue, activating it, deactivating it, and then removing it. Probes (210), (230), (240), (250), and (260) are operated by inserting into the qr tigsue, activating, deactivating, rotating to a second position to be desiccated or ablated, activating, and then removing. Again, the choice of RF probe design is dependent on the amount of tissue to be ablated or desiccated. Once ablation or desiccation is completed, the probe is withdrawn. Relief cutæ to the anterior cornea may be necessary as described above to allow the surface o~ the cornea to conform to the underlying tissue modification. In this way, the flat, astigmatic axis (507) is steepened such that the cornea becomes reasonable symmetrical and spherical.
r le 2 - The Correction of ~erol~ia In order to correct hyperopia a proces~ 6imilar to that described above with regard to Figures 3A-3D is carried out. As shown in Figures 23B, 23D and 23E, radial or circumferential partial depth incisions (510) are made in the periphery of the cornea . A l i 1 l i?r separator is inserted to create a li -11i9r pathway (512) for the insertion of the electrical probe.
Two different approaches are possible to correct the hyperopic eye . In the f irst approach, shown in Figure 23B partial depth incisions (510) are made in 35 the peripheral cornea and a circumferential ] i 1 1 iqr wo gsnls78 PCTIUS95/01613 ~3~ Q3 - 24 - --~eparation zone t512) will be formed keneath the corneal surface. Following separation of the l~r^ll~r tissue, one of the circular RF probes shown in Figures 6-11 A and B is inserted through the partial depth incision (512).
5 The probe is then activated to change the volume by ablation or desiccation of the tissue (514) in the channel. The choice of RF probe design is dependent on the amount of ti3sue to be ablated or desiccated. Probes (210), (220), (230), (240), (250) and (260) will allow 10 for desiccation of the channel. Probe (220) is operated by inserting it into the lamellar tissue, activating it, deactivating it, and then removing it. The other probes are operated by inserting them into the l l l ~r tissue, activating, deactivating, rotating to a second position 15 to be ablated, activating, deactivating and repeating this process until the entire channel is desiccated, and then removing it. Pro4es (210), (240), (250) and (260) will allow for a41ation of the channel. The probes are operated by insertion into the lamellar tissue, 20 activation, deactivation, rotation to a second position to be ablated, activation, and ror~t; n~ until the entire channel is ablated, followed by removal of the probe.
Probes (250) and (260) can also be operated by complete insertion into the lamellar tissue, activation, 25 deactivation, pulling partially back out of the tissue to a second position to be ablated, activation, deactivation and repetition of this process until the entire channel is ablated, followed by removal of the probe. Again, relief cuts in the anterior of the cornea may be 30 npc~clsilry as de6cribed above to allow the surface of the cornea to conform to the underlying tissue removal. In this way, the central corneal surface is steepened such that the cornea curvature is improved.
A second approach to the treatment of a 35 hyperopic eye is to use a straight RF probe. In this wog5nl578 21 83l 03 PCTNS95/01613 second approach 2 or more partia depth incisions ~510) are made in the periphery and 2 or more radial l; l1Ar separation zones are formed as shown in Figures 23D and 23E. Following separation of the 1 ;3rAl 1 ~r tissue, one of 5 the straight RF probes shown in Figures 12-19 A and B is inserted through each partial depth incision (510) in the lamellar separation zones (512) and (514). The probe is then activated to change the volume by ablation or desiccation of the tis6ue in the channel. The choice of 10 RF probe de8ign is tl~r~n~Pnt on the amount of tissue to be ablated or desiccated. Probes (300), (310), (320), (330), (340), (350), (360) and (370) will allow for desiccation of the channel. Probes (300) and (310) are operated by insertion into the 1 -11Ar tissue, 15 activation, deactivation, and then removal. Probes (320), (330), (340), (350), (360) and (370) are operated by inserting into the l -llA-r tissue, activating, deactivating, moving to a second position to be ablated, activating, deactivating and repeating this process until 20 enough of the channel is desiccated, and then removing the probe. In this way the tissue desiccated can either form a continuous path (516) or can be interrupted points along the radial l -lli~r separation channel (518).
Probes 1320) - (370) will allow for ablation of corneal -- --25 volume inside the radial l~ r separation channel.
Probes (320), (340), (350), (360) and (370) are operated by insertion into the l: -l~;lr tissue, activation, deactivation, moving it further into the tissue to a second po8ition to be ablated, activation, and reP''A'tinS
30 until the entire channel is ablated, and then removal.
The 8ame probes can also be operated by complete insertion into the l ;~m~ r separation channel, activation, deactivation, pulling back out of the tisAAue channel to a second position to be ablated, activation, 35 deactivation and repetition of the process until the Woss/2ls78 2~.83~03 - 26- PCrN595/01613 ~
enough of the channel is ablated, followed by removal of the probe. Again, relief cuts may be necessary in the anterior cornea as described above to allow the surf ace of the cornea to conform to the underlying tissue 5 removal. In this way, the corneal surface is steepened centrally such that the corneal curvature is improved.
Exam~le 3 - The Correction of Mvo~ia In order to correct myopia the process similar 10 to that described above with regard to Figures 3A-3D is carried out. As shown in Figures 23F and 23G, radial or circumferential partial depth incisions (520) are made in the periphery of the cornea. A l~ r separator is inserted to create a radial l; 11 ;Ir separation channel 15 (522) toward the center of the pupil for the insertion of the electrical probe.
For correction of myopia, the l ~ r path (522) will be formed under or near the central or paracentral portion of the cornea. Following separation 20 of the l ~ r tissue, one of the straight RF probes shown in Figures 14-19 A and B or the disc or washer probes shown in Figures 20-21 A and B is inserted through the peripheral partial depth incision (520) into the l~r^llAr separation channel (522). The probe is then 25 activated to change the volume by ablation of the tissue in the channel, the volume change (524) resulting from the use of the disc-shaped probe (400) is shown in Figure 23F and volume change (526) resulting from the use of the washer-shaped probe (410) is shown in Figure 23G. The 30 choice of RF probe design is ~1~.pF.n~lF.nt on the amount of tissue to be ablated. Probes (320) - (370) will allow for ;3hl ~ti~n of the channel . The probes are operated by insertion into the l ~ r tissue, activation, deactivation, advancing the probe into the channel to a 35 second position to be ablated, activation, deactivation, Wo sS/215~8 21 8 3 ~ o ~ - 2 7 - PCT/US95/01613 repeating the process until.the entire channel is ablated, and then the probe is removed. The probes can also be operated by complete insertion into the 1; ~ r separation channel, activation, deactivation, pulling out 5 of the channel to a second position to be ablated, activation, deactivation and repeating the process until the entire channel is ablated, and then the process is removed. Probes (400) and (410) are operated by insertion into the lamellar separation channel ( 522 ), l0 activation, deactivation and removal from the channel.
Again, relief cuts in the anterior cornea may be n~ qS~ry as described above to allow the surface of the cornea to conform to the underlying tissue removal. In this way, the corneal surface in the central corneal area 15 is flattened such that the corneal curvature is improved.
The f oregoing examples of procedures and devices according to the present invention are only 2 0 representative and are not meant to be in any manner limiting. Other '-~;r ' C~ areas of application, methods of use of the present invention, within the scope of the claims appended hereto, will be evident to those skilled in this art. Other embodiments of the procedures 25 without the scope of the claims but within the spirit of invention described herein are considered to be equivalent to those procedures and devices claimed.

Claims

I CLAIM AS MY INVENTION:

1. A procedure for altering the shape of the anterior corneal surface of an eye having a corneal mass posterior to the anterior corneal surface, wherein the corneal mass has a volume, the procedure comprising the steps of:
initiating at least one access site into the corneal mass posterior to Bowman' s layer, introducing through said at least one access site an electrosurgical probe, and energizing said electrosurgical probe to modify the volume of the corneal mass adjacent to said electrosurgical probe.

2. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass by ablation.

3. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass by desiccation.

4. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass with a bipolar RF electrode.

5. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass with a monopolar RF electrode.

6. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass with an electrosurgical RF electrode in a sesquipolar configuration.

7. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass with an electrosurgical probe in the form of a substantially hook-shaped probe.

8. The procedure of claim 1 where the energizing step comprises the step of modifying the corneal mass with an electrosurgical probe that forms a probe of less than about 350°.

9. The procedure of claim 1 where the energizing step comprises the step of modifying the volume of the corneal mass to correct hyperopia.

10. The procedure of claim 3 where the energizing step comprises the step of modifying the volume of the corneal mass to correct hyperopia or astigmatism.

11. The procedure of claim 6 where the energizing step comprises the step of modifying the volume of the corneal mass to correct hyperopia, myopia or astigmatism.

12. The procedure of claim 1 additionally comprising the step of placing a relief cut in at least a portion of Bowman's layer.

13. The procedure of claim 1 where the energizing step comprises the step of modifying the volume of the corneal mass to alleviate astigmatism.

14. The procedure of claim 1 where the energizing step comprises the step of modifying the volume of the corneal mass to correct myopia.

15. The procedure of claim 14 where the energizing step comprises the step of modifying the volume of the corneal mass at or near the center of the cornea.

16. An electrosurgical probe comprising a support end and a substantially hook-shaped contact end where said contact end comprises at least one active tissue contacting site disposed on a surface of said contact end, the area of the at least one active site is substantially smaller than the area of the contact end surface on which the at least one active site is disposed, the active site is in electrical connection with an insulated conductor residing within said contact end and extending to the support end, the conductor is adapted to be coupled to an electrical signal source, the probe is adapted for introduction through an access site into a corneal mass posterior to Bowman's layer, and the probe modifies the corneal mass when the at least one active site is energized by the signal source to thereby alter the anterior corneal surface and correct refractive error.

17. The electrosurgical probe of claim 16, said probe comprising two active tissue contacting sites, the active sites being in electrical connection with a single insulated conductor residing within said contact end and extending to the support end.

18. The electrosurgical probe of claim 16, said probe comprising a single active tissue contacting site, said active site being located in a tip of the contact end.

19. The electrosurgical probe of claim 16, said probe comprising a single active tissue contacting site wherein the active site comprises an arc of less than about 350°.

20. The electrosurgical probe of claim 16, said probe comprising two active tissue contacting sites that are each in electrical connection with their own separate conductor residing within said contact end and extending to the support end.

21. The electrosurgical probe of claim 16, said probe comprising a single active tissue contacting site located near the tip of the contact end on the top portion of the probe.

22. The electrosurgical probe of claim 16, said probe comprising a single active tissue contacting site located near the tip of the contact end and raised and pointed in the retracting direction of the probe.

23. An electrosurgical probe comprising a support end and a straight, substantially flat contact end where said contact end comprises at least one active tissue contacting site, a substantial portion of the at least one active site is disposed on a major surface of the substantially flat contact end, the at least one active site is in electrical connection with a conductor residing within said contact end and extending to the support end, the conductor is adapted to be coupled to an electrical signal source, the probe is adapted for introduction through an access site into a corneal mass posterior to Bowman's layer, and the probe modifies the corneal mass when the at least one active site is energized by the signal source to thereby alter the anterior corneal surface and correct refractive error.

24. The electrosurgical probe of claim 23, said probe comprising a single active tissue contacting site, said active site extending along the length of the straight contact end and located on the top portion of the probe.

25. The electrosurgical probe of claim 23, said probe comprising a two active tissue contacting sites that are each in electrical connection with their own separate conductor residing within said contact end and extending to the support end.

26. The electrosurgical probe of claim 23, said probe comprising a single active tissue contacting site located near the tip of the contact end located on the top portion of the probe.

27. The electrosurgical probe of claim 23, wherein a single active tissue contacting site is located near the tip of the contact end and raised and pointed in the retracting direction of the probe.

28. The electrosurgical probe of claim 23, wherein said contact end is broadened and wherein a single active tissue contacting site is located within the broadened contact end.

29. The electrosurgical probe of claim 23 wherein said contact end comprises a washer-shaped single active tissue contacting site.

30. The electrosurgical probe of claim 23 wherein said contact end comprises a disc-shaped single active tissue contacting site.

31. The electrosurgical probe of claim 30 wherein a wire loop forms the surface of the disc-shaped active site.

32. A sesquipolar electrosurgical kit for electrosurgically altering the shape of the corneal surface of the eye, said kit comprising in packaged combination:
(a) an electrosurgical probe comprising a support end and a substantially hook-shaped contact end, wherein said contact end comprises at least one active tissue contacting site; and (b) a sesquipolar return electrode that is adapted for positioning on or near the eye.

33. A sesquipolar electrosurgical kit for electrosurgically altering the shape of the corneal surface of the eye, said kit comprising in packaged combination:
(a) an electrosurgical probe comprising a support end and a straight, substantially flat contact end wherein said contact end comprises at least one active tissue contacting site, and a substantial portion of the at least one active site is disposed on a major surface of the substantially flat contact end; and (b) a sesquipolar electrode that is adapted for positioning on or near the eye.

34. The electrosurgical probe of claim 16, wherein said substantially hook-shaped contact end has an open, substantially circular shape.

35. The electrosurgical probe of claim 16, wherein the contact end is substantially flat.

36. The electrosurgical probe of claim 23, wherein the area of the at least one active site is substantially smaller than the area of the major surface on which the at least one active site is disposed.