WO1994022402A1

WO1994022402A1 - Phacoemulsification method and tip

Info

Publication number: WO1994022402A1
Application number: PCT/CA1993/000200
Authority: WO
Inventors: Peter L. Davis
Original assignee: Davis Peter L
Priority date: 1993-03-31
Filing date: 1993-05-14
Publication date: 1994-10-13
Also published as: AU4055793A

Abstract

Phacoemulsification method and tip (10) concerning the enhance generation of shockwaves and/or focusing of shockwaves. The method can be carried out with a phoco tip in an essentially contactless manner.

Description

Phacoemulsification Method and Tip

BACKGROUND OF THE INVENTION

Field of the Invention: This invention relates an improved method for phacoemulsification of eye tissue, particularly cataracts, and an improved ultrasonic phacoemulsification tip and device for carrying out the method according to the present invention. A preferred embodiment is a substantially contactless phacoemulsification method of deteriorating and removing eye tissue.

Prior Art:

Phacoemulsification ("phaco") surgical instruments are used for the erosion and pulverization of malfunctioning or diseased tissue of the eye, in particular the opaque hardened protein of cataract of the eye. Electrical energy is delivered to an acoustic wave generating hand held transducer that conducts energy into the eye via a thin walled (e.g. 0.050 millimeter) metal tip.

The transducer converts one form of energy into another. A phaco transducer functions by converting alternating electrical current into acoustic waves having a frequency well beyond the range of human hearing (16,000 cycles/second). One method used in phaco transducers of converting electrical energy to acoustic wave energy is to electrically stress a crystal to generate mechanical oscillations in the crystal. This piezoelectric device can be designed to operate efficiently so that little energy is lost as heat. Any heat released is conducted down the hollow titanium tip (i.e. acoustic wave generating horn) and radiates into the anterior chamber of the eye. The lead zirconate titanate man-made crystal now often used by transducer designers can convert electrical to acoustic wave energy with high level of efficiency. A poorly engineered transducer will be less efficient with a greater loss of energy.

A second method of converting electrical energy to acoustic wave energy is to utilize a magnetostrictive design. This requires a wire coil to create a electromagnetic field, which then causes metal wafers within the transducer to constrict and expand creating ultrasonic waves. This design is usually less efficient than the piezoelectric device, and the metal wafers readily conduct heat via the titanium needle.

Both designs lose a portion of the energy converted as heat within the transducer handle, and the heat is conducted into the eye via the titanium tip where it has potential for thermal damage to anterior segment tissues. In research labs, a large cooling bath is used to cool the liquid being experimented on with acoustic horns indicating the large amount of heat released. In phacoemulsification destruction of a cataractous nucleus, a constant flow of balanced salt solution in and out of the anterior segment is needed to transfer heat out of the eye and to remove lens debris (lens milk) to permit a clear view of the operative site. The conventional tips available for phacoemulsification are hollow, and generally have 1.0 millimeter (mm) outside diameter and 0.90 to 0.91 mm internal diameter. These tips are made of titanium metal and have a beveled end. The end faces of these tips were originally set at a 15 degree angle, but are currently available set at 30 to 45 degree angles. In addition, the recent tendency is to make tips with thinner walls and oval cross sections to allow easier entry into the eye.

During cataract surgery, balanced salt solution is delivered by gravity infusion into the eye via an infusion tube leading to a silicone sleeve that surrounds the tip. Another tube connected to a hydraulic pump aspirates the pulverized material, which is carried along by the salt solution out of the eye via the hollow center lumen of the titanium tip.

The conventional surgical apparatus includes a console with aspirating pump for removing balanced salt solution from the operative site carrying with it the eroded tissue. The conventional console also delivers electrical energy to the transducer hand piece that converts electrical energy into acoustic ultrasonic energy. The piezoelectric crystal in the conventional transducer hand piece generates vibrations in the 28,00 to 50,000 cycles per second range, and these vibrations are transmitted to a threaded on titanium hollow metal tip 24 mm in length and 1.0 mm in width.

The silcone sleeve surrounding the tip does not vibrate while it delivers balanced salt solution by gravity to the anterior chamber of the eye into which the phacoemulsification tip with its encasing silicone sleeve have been inserted. As acoustic energy is delivered to the tip nearby tissue is eroded, and the aspirating pump then removes the tissue fragments along with a portion of the salt solution.

It is desirable to erode the hard cataract material within the thin transparent capsule that surrounds the lens of the eye to prevent injury to other tissues in the area such as corneal endothelium and iris. To accomplish this, a precise delivery of energy must be delivered by the vibrating metal tip. Sharp edges on the conventional tip can inadvertently tear the capsule or cornea, and allow vitreous gel located deeper in the eye to move forward. This often impairs effective healing and prevents satisfactory visual recovery.

The procedure of using ultrasonic acoustic wave field erosion of the nucleus of the lens of the human eye is being utilized more frequently by opthalmic surgeons. Typically, a hand held transducer of the type described above is used in these procedures. The hand held transducer converts alternating electrical current into acoustic waves, and is a complex and powerful device. The basic mechanism for this energy conversion is well understood by engineers and scienctists, particularly physicists. However, information concerning the energy conversion mechanism has been rarely presented to clinicians.

In spite of this understanding by engineers and scienctists and the large industrial use of ultrasound in chemical and material processing, clinical medicine, and cleaning procedures, there has been almost a complete lack of review materials on the underlying principles from which ultrasonic effect originates. This observation is especially true concerning how ultrasound works within the human eye. Designed in the 1960's by the Cavitron Corporation in association with Charles Kelman, .D. of New York City, the erosion mechanism is generally believed to be a mechanical "jack hammer" cutting action by the soda straw-like metal tube tip having an oblique end, which is ultrasonically vibrated back-and-forth approximately one (1) to three (3) microns. The sharp titanium tip ultrasonically vibrated is believed to act as a sort of hollow jack hammer that cuts into and mechanically disrupts the cataract nucleus as it oscillates at thousands of times per seconds. An increase in phaco power is believed to create more mechanical activity to better emulsify hard nuclei and is known to increase the amount of to and fro movement of the tip. This increased stroke length is thought to increase the jack hammering effect, and thus better chisel the nucleus.

This approach has lead to the development of tips having sharp edges and thin walls to better "cut" the cataract. Cataract surgeons often suggest a 45 or 60 degree tip be used on hard cataracts to better chisel the nucleus with a more pointed jack hammer. Clearly, the

"jack hammer" concept is the prevailing view on the mechanism of how phaco devices erode or emulsify tissue.

Undoubtly, the sharp cutting edge of prior art tips can cut tissue by actual physical contact therewith as the tips are ultrasonic vibrated increasing the cutting action of the tips. However, the inventors and developers of the prior art tips failed to understand that the generation of Shockwaves by the tips can cut or deteriorate tissue without actual physical contact therewith. Thus, the prior art does teach or suggest the concept of using Shockwaves to enhance physical cutting action with a sharp tip, and clearly does not teach or suggest relying solely on Shockwaves for the entire cutting action without the aid of sharp tips. Further, the prior art does not teach or suggest the focusing of Shockwaves or the increased generation or intensity of shock waves generated for enhancing the cutting effects of tissue, and for providing the possibility of contactless deterioration and removal. In effect, the Shockwaves deteriorate the tissue by the application of shear forces by large pressure gradients within the tissue rupturing lens structure, and in a sense providing the overall impression of a cutting action. Most prior art tips do not include any means or are not configured for focusing Shockwaves. Further, the prior art does not teach or suggest providing means or configuration for the focusing of Shockwaves. Typically, the prior art tips are constructed of thin wall metal needles terminating at small surface area annular end faces or rims of approximately 0.050 to 0.1 mm in thickness, the end faces being set obliquely relative to the longitudinal axis of the tips. The geometry of these tips are defined by annular end faces having flat planar surfaces. The outer perimeter of the annular end faces intersect with the cylindrical outer surface of the tip defining a sharp perimeter edge.

This type of tip geometry does not focus Shockwave energy. Specifically, the shock waves generated by the annular end face having a flat planar surface only generates Shockwaves that propogate normal from the annular end face. The Shockwaves generated from the outer cylindrical surface of the tip propogate divergently. The prior art tip may require to some extent actual physical contact with the tissue to carry out the "jackhammer" effect to deteriorate tissue. Accordingly, the provision of a sharp cutting edge may improve the performance of the prior art tip to more effectively cut tissue by intimate contact therewith. Further, the prior art tips may improve by the present thin walled construction thereof allowing for shaper cutting edges and improved penitration ability into the tissue under a "jackhammer" cutting mechanism, similar in concept to needles for puncturing skin tissue. Acoustic wave energy physics research done since the 1960's reveals possibilities of other mechanisms for tissue erosion with improved tip designs. Upon careful evaluation of the acoustic energy literature, it is now believed that even the prior art tips may not have to actually touch the cataract nucleus during phacoemulsification to cause some tissue removal. Instead, the energy that erodes the nucleus is created by clouds of millions of acoustic wave generated 80 - 150 micron sized bubbles at the surfaces of the tip being ultrasonically vibrated. The micron sized bubbles are generated at the end of the metal rim (acoustic horn) , and expand and implode within a few acoustic cycles creating massive shock waves (500 atmospheres) plus fluid waves at 400 km/hr. These micro bubbles have been photographed by B. Svensson of Sweden in plexiglas test chambers, and these photos have been shown at the meeting of the American Society of Cataract and Refractive Surgery held in Boston, Massachusetts in April 1991. At that meeting, a paper was also presented that documented sonoluminescent (flame) activity at the tip of phaco devices. This phenomenon has also been photographed in the past and is well illustrated in the ultrasound acoustic literature. The imploding microbubbles produce a phenomenon referred to as "transient cavitation" in the physics literature, generating energy that erodes any solid surface in the proximate area of where the acoustic cloud is released into the fluid. These photos lend support to our belief that the tip does not touch the cataractous nucleus during phacoemulsification, but instead the energy that emulsifies the nucleus is created by clouds of acoustic wave generated micron sized bubbles that are unstable and implode within a few acoustic cycles generating massive shock waves that mechanically emulsify the cataract.

Ophthalmic surgeons are advised that the none imploding large size air bubbles released during phaco operations are a result of "cavitation". Physicists refer to this release of dissolved gas from liquid as "rectified diffusion". The degassing of fluids has been an industrial use of ultrasound since the 1950s. This is an optical nuisance within the eye during phacoemulsification and can be lessened by using balanced salt solutions with the lowest possible amount of dissolved air (i.e. use balanced salt bottles with glass walls) . The common usage of the term cavitation when referring to the release of air dissolved in balanced salt solutions during phacoemulsification surgery creates confusion when acoustic scientists use the words "transient cavitation" to describe the creation of millions of imploding microbubbles generated when fluids are sonicated. A second form of cavitation is called "stable" cavitation, implying some micron sized bubbles that last hundreds or thousands of acoustic cycles. Their activity is less well understood by researchers. The massive energy released by cavitation erodes the transducer tip necessitating that they be made of a metal such as titanium.

Even though surgical procedures involving the use of phacoemulsification surgical instruments having proven effective, there is some risk of phaco thermal injury to the anterior segment of the eye during the procedure. The implosion of microbubbles during the process generate massive fluid and shock waves that erode the solid material cataractous nuclei, and can release excess thermal energy into the eye. Further, residual heat from the phaco transducer is conducted down the hollow titanium needle (acoustic focusing horn) as mentioned above, and radiates in the anterior chamber potentially causing thermal damage within the anterior segment. Piezoelectric transducers are more efficient and conduct less heat along the needle compared to older magnetostrictive type transducers.

To prevent heat damage, a constant flow of balanced salt solution in and out of the anterior segment is needed to transfer heat out of the eye and to remove lens debris (lens milk) so that the surgeon can visualize the area. However, any problem with proper balanced salt solution circulation can quickly result in heat damage to eye tissue. To insure proper circulation, it is recommended that the surgeon should personally:

1. Visually be certain that balanced salt solution (bss) is being aspirated from the transparent test chamber into the catchment device, that the test chamber remains filled or only slightly dimpled when the device is in phaco mode and held at eye level, and that bss exits from the silicone infusion ports before the device is placed in the anterior chamber;

2. Kink the infusion line while in phaco mode and watch for the test chamber to collapse. Follow this by kinking the aspiration line and listen for the sound of vacuum build up; 3. Ascertain the incision is large enough for the phaco transducer tip being used, thus avoiding pinching the silicone infusion sleeve, and that some bss leaks from the incision;

4. Aspirate some viscoelastic, if present, from the anterior chamber before entering phaco mode to guarantee that balanced salt circulation not be impaired;

5. Avoid overtorquing the incision (greater tendency if made in the cornea) such that the silicone sleeve is compressed against the edges of the incision;

6. Be aware prolonged time in phaco mode delivers more heat via the titanium tip (use short bursts of phaco power during carving of the nucleus and consider use of pulse mode if available;

7. Become aware of venting sounds that many machines emit if aspiration is impaired; and

8. Watch for persistence of "lens milk", a whitish material of lens fragments in the area of the phaco tip, suggesting movement of bss is restricted. Rigid titanium infusion sleeves have been promoted to guarantee bss is infusing readily and that bss can leak from the incision. However, if these are malaligned they may be frayed by the phaco tip oscillations releasing metal fragments into the eye. The best prevention of thermal injury is to be aware that all transducers lose some energy as heat that is conducted via the titanium tip and that circulation of bss is essential to prevent thermal injury. Other means for reducing the risk of heat damage can be provided by designing transducers with thermal sensors that stop the device if overheating occurs. Balanced salt solution is currently being chilled prior to its use during the phacό procedure. It could be circulated through larger channels in the transducer handle to create more cooling. It has been traditional for the acoustic horn titanium tip to have a thin wall with the tip bevelled between 15 - 45 degrees with a 0.91 mm lumen. This design has been used since the 1960^,s, and could be redesigned to create more efficient acoustic wave fields at the tip, thus eroding the nucleus with less energy, thereby reducing the risk of thermal and or chemical injury. The motivation for conceiving and developing the present invention resulted from a patient that suffered a thermal injury during a phaco procedure in 1989. The following is a case history of that patient, and an outline of the principles of acoustic wave cloud action by transient microbubble formation and implosion (transient cavitation) , which generates massive localized shock and fluid waves near the nucleus. An understanding of such principles will aid clinicians in patient protection from excessive thermal shock wave energy release during surgery. In addition, the following proposed design changes for transducers can lessen the risk of damage caused by the escape of energy as heat and or excessive mechanical energy release within the anterior segment of the eye. CASE HISTORY

A cataract removal by phaco technic was attempted on a 55 year old diabetic male's right eye in April 1989. Assembly of the apparatus was flawed by installing the silicone tubing around the peristaltic pump in reverse. In this situation, infusion of balanced salt solution functioned correctly but no aspiration was occurring. Therefore, the anterior chamber remained filled providing little indication balanced salt solution was not circulating within the anterior chamber. The phaco tip was inserted through a 3.2 mm incision into the eye where viscoelastic agent had been previously instilled. Overheating occurred within a few seconds with the creation of a total thickness 3 X 3 mm opacity of the superior cornea with vapor rising from this area. The procedure was completed by manual ECCE and a 6.5 mm biconvex single piece implant was dialled into the capsular bag. Following incision closure with interrupted 10-0 nylon sutures, a conjunctival flap was pulled down and fixated to clear cornea inferior to the area of damage cornea. Healing occurred with relaxation of the original 9 dioptres with the rule astigmatism to 5 dioptres at an oblique axis, fibrotic closure of 90 degrees of the upper angle, retraction of the iris behind the implant superonasally and a best corrected vision of 20/80. This visual reduction was secondary to diabetic maculopathy later treated by argon laser therapy.

Three months after the first eye had been operated upon, a manual ECCE procedure was performed on the patient's left eye. He achieved vision of 20/50 with a 7 mm biconvex PMMA single piece lens implant and a - 1.50 spectacle correction. The presence of diabetic maculophy also reduced the vision in this eye. Thirteen months post surgery, the residual astigamatism of his thermally damaged RE was surgically managed with paired 3 mm arcuate corneal incisions in the steep axis, performed with a 35 degree triangular ultrathin diamond blade at a 8 mm optical zone. This reduced his oblique astigamatism to 2 dioptres by keratometric measurement. Thermal injury of this magnitude occurred once in 2000 phaco procedures performed by the attending surgeon to date, nonetheless its severity led to the review of the present phaco transducers concerning their design, mechanism of action, and biological effects.

Researchers are studying the effects the enormous heat generated within liquids can have in forming new chemicals (sonochemistry) , and the phenomenon of the flame generated within the bubble known as sonoluminence. This heat is rapidly dissipated and does not significantly contribute to raising the temperature of the liquid being sonicated. Sonochemists are aware that water is broken down to H₂0₂ and free OH radicals in ultrasonic acoustic fields generated by transducers with designs similar to those used in ophthalmic surgery. This release of free radicals near the end of a surgical phaco tip has also been demonstrated by B. Svennson during phacoemulsification (See Svensson, Eur. Soc. Cataract and Retract. Surg. , September 1991). Research is needed to determine if these free radicals cause tissue damage.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved phacoemulsification method. Another object of the present invention is to provide an improved phacoemulsification method for focusing Shockwaves for enhancing tissue deterioration and removal. A further object of the present invention is to provide an improved phacoemulsification method for increasing the generation of Shockwaves for enhancing tissue deterioration and removal.

An even further object of the present invention is to provide improved phacoemulsification method for substantially contactless tissue deterioration and removal.

An object of the present invention is to provide an improved phacoemulsification tip and device for carrying out the method according to the present invention.

Another object of the present invention is to provide an improved phacoemulsification tip and device for focusing shock waves.

A further object of the present invention is to provide an improved phacoemulsification tip and device having a geometry and surface configuration for focusing shock waves.

A still further object of the present invention is to provide an improved phacoemulsificatoin tip and device for increasing the generation of shock waves.

An even further object of the present invention is to provide an improved phacoemulsification tip and device having an increased surface area at the distal end thereof to increase the generation of micro-bubbles formed by the tip during operation.

An even still further object of the present invention is to provide an improved phacoemulsification tip and device having a rounded peripheral edge to prevent inadvertant damage or injury to eye tissue. A further object of the present invention is to provide an improved phacoemulsification tip resistant to wear and damage.

The phacoemulsification method and device according to the present invention will provide for safer and more effective surgical procedures for the removal of eye tissue.

The phacoemulsifcation method according to the present invention involves deteriorating eye tissue by the use of Shockwaves. The Shockwaves are preferably generated by a phaco tip having means for generating Shockwaves.

To effectively carry out the phacoemulsification of eye tissue, the Shockwaves should be focused for the purposes of increasing the intensity of the Shockwaves and for improving the accurracy of removing tissue. Further, the increased generation of Shockwaves can increase the intensity of the Shockwaves for more effective tissue removal. The phacoemulsification method can be conducted without the continuous contact of the phaco tip with the eye tissue being removed, unlike the prior art methods that rely on the intermittent contact "jack hammer" approach to tissue removal. Further, the phacoemulsification of eye tissue can be achieved according to the present invention in a substantially contactless manner except for possible inadvertant contact during positioning of the tip in the eye.

The contactless or substantially contactless method of phacoemulsification of eye tissue according to the present invention takes place by Shockwaves eminating from the end face of the phaco tip. The focusing of Shockwaves in front of the tip eliminates the need for any intimate contact of the tissue undergoing phacoemulsification with the phaco tip. Further, increasing the generation of Shockwaves at the tip, for example by increasing the surface area of the end face of the tip, tends to prevent tissue touching the end face prior to being substantially deteriorated. Thus, only particulate remains of tissue cells and debris, as opposed to relatively harder cell walls, make physical contact with the end face of the phaco tip during steady state operation. In a sense, the phaco tip operates as a contactless drilling tool emulsifying tissue as it is physically advanced through the tissue destroying tissue in its path and only actually contacting tissue debris, which is readily removed through the tip by aspiration.

The focusing of Shockwave increases the accuracy of the phacoemulsification of tissue. Instead of having a cutting rim undergoing jack hammering action as in the prior art devices, a single shock wave focal point can be utilized. In theory, the generation of shock waves can be focused so that the threshold intensity required to readily emulsify tissue would occur only in close proximity to the focal point. Thus, a phyician using such method and device would be able to more accurately remove tissue during the surgical procedure by simplying guiding the tip having a small emulsification zone.

The phacoemulsification tip according to the present invention was developed to more efficiently erode eye tissue at lower energy levels than the conventional tip. The lower energy level operation will reduce the risk of thermal damage to the eye. Further, the tip according to the present invention more effectively removes tissue without disrupting surrounding tissues and fluids with increased speed of removal. Thus, the tips greatly improve the safety and reduce the time with respect to current surgical procedures. The phacoemulsification tip according to the present invention takes advantage of a new approach to applying ultrasonic techniques. Instead of mechanically attempting to cut away eye tissue, the tip was developed to 1) increase the generation of micro bubbles, and/or 2) focus ultrasonically generated shock waves, which effectively erode structures in situ. This approach allows for the incorporation of rounded edges that prevent damage to eye tissue during insertion into the eye and during operation. This approach contrasts significantly with the present practice of using sharp tips and thin walls to cut away tissue by a "jack hammer" ultrasonic vibration of the tip.

In one embodiment, the wall thickness is significantly increased compared with prior art tips resulting in a greater end face or rim surface area. The rim acts as an acoustic horn, thus, increasing the surface area of the rim will directly proportionally increase the generation of micro bubbles. Instead of increasing the outer dimension of the tip (compared to existing tips) which would increase the overall size of the tip and make it more difficult to insert in the eye and maneuver during operation, it is preferred to reduce the inner diameter of the lumen of the tip to increase the surface area of the rim.

In another embodiment, the end face of the tip is provided with a concave recess designed to focus the ultrasonic acoustic waves. The surface of the concave recess can be smooth or faceted, or portions can be smooth and/or faceted. In this embodiment, the concave recess can be provided in only a portion of the end face leaving a planar rim, or almost the entire end face can be recessed leaving only the outer rounded rim. In a further embodiment, the end face is substantially curved, preferably by a Gaussian curve. More specifically, the curved surface extends from the entrance to the lumen to the outer cylindrical surface of the distal end of the tip. Viewing a longitudinal cross section of the tip, the wall terminates at a convex surface. The convex surface ends of the tip focus the ultrasonic acoustic waves at a focal point anterior to the tip.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a top view of an embodiment of the distal end of a phacoemulsification tip according to the present invention;

Figure 2 is a side view of the phacoemulsification tip as shown in Figure 1;

Figure 3 is a partially broken away longitudinal cross-sectional view showing the details of another embodiment of a phacoemulsification tip according to the present invention; Figure 4 is an end view of the tip shown in Figure

3;

Figure 5 is a partially broken away longitudinal cross-sectional view showing the details of a further embodiment of a phacoemulsification tip according to the present invention; and

Figure 6 is an end view of the tip shown in Figure 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The method according to the present invention provides the phacoemulsification of eye tissue in a safe and effective manner. The method according to the present invention includes focusing Shockwaves with a phaco tip at tissue to be removed without substantial contact with the tissue. The Shockwaves tear apart the tissue by providing high shear forces due to the large tranisent pressure variations created as the shock waves propogate through the tissue to be removed.

The effectiveness of the method according to the present invention can be improved by:

1) increasing the intensity of the Shockwaves; and/or

2) increasing the generation of Shockwaves.

The concept of focusing Shockwaves increases the intensity of the Shockwaves at one or more focal points. A single focal point is desireable in order to achieve a maximum intensity, and to increase the accuracy of removing tissue. It is possible to tailor the intensity and focusing of the shock waves by primarily controlling the configuration phaco tip and power of the phaco transducer to a sufficient level of intensity to destroy tissue only at or near the focal point, greatly increasing the accuracy of operation.

The generation of Shockwaves can be increased by increasing the surface area of the end face of the phaco tip. The increased generation of Shockwaves in itself can greaterly improve the effectiveness of the method without the focusing of Shockwaves. However, the combination of both focusing Shockwaves and increasing the generation of Shockwaves provides for the best results.

The present invention also concerns the details of the structure and design of the distal ends of phacoemulsificatoin tips. Various designs of phacoemulsification tips according to the present invention are shown in Figures 1 - 6. These tips are preferably made of titanium metal to resist wear and withstand operational stresses. A general embodiment of the present invention is shown in Figures 1 and 2. In these figures, details of the distal end 10 of a phacoemulsification needle tip are illustrated. The distal end 10 is defined by a cylindrical end portion of the needle tip having an inner diameter 12 and an outer diameter 14. A lumen 16 extends through and is defined by the inner surface diameter of the tip 10. The lumen is shown as having a uniform diameter, however, it is possible to have a lumen of a different shape, and/or varying diameter. The inner diameter 12 has a dimension in the range of approximately 0.25 to 0.75 mm, preferably 0.30 to 0.70 mm, and most preferably 0.40 to 0.05 mm. These diameters generate better acoustic wave clouds with more transient microbubbles as shown by a prototype that totally erodes the cataract rather than creating an erosion only anterior to the thin rim of prior art tips with 0.91 mm lumens.

The outer diameter 14 has a dimension in the range of approximately 0.95 to 1.05 mm, preferably 0.97 to 1.03 mm, and most preferably 1.00 mm. These dimensions allow easy access to the eye interior via small incisions, and is the size surgeons have developed phaco techniques around. A change in outer diameter would require different incisions and increase risk of thermal damage if the tip were to be torqued in the incision.

The thickness 15 of the wall of the distal end 10 of the needle tip defined between the inner surface of the lumen 16 and outer surface of the distal end 10, and is in the range of approximately 0.15 to 0.35 mm, preferably 0.20 to 0.32 mm, most preferably 0.25 to 0.30 mm, and optimally 0.30 mm.

In this embodiment, an end face or rim 17 is defined at the very end of the distal end 10. Specifically, the end face surface or rim 17 extends from the entrance of the lumen 16 to the outer surface of the distal end 10.

The distal end 10 of the phacoemulsification tip is beveled at an angle 18. This angle 18 is set in the range of preferably 15 to 60°, most preferably 15 to 45°, and optimally 30°. The surgeon must be able to see the site of tip action, and be able to fixate loose pieces of cataract to the tip end before a burst of phaco energy is delivered. This is best done if the tip angle is 30°' Further, the leading edge 20 is slightly rounded, as shown in Figure 2, to prevent burring with potential tissue tearing. The radius of curvature of this edge is preferably 0.060 to 0.070 mm. In addition, the remaining portions of the outer edge 22 of the distal end 10 are also rounded for the same purpose.

The wide end face of this embodiments permits the generation of huge numbers (millions) of micron sized unstable bubbles that implode within a few acoustic cycles. These shock waves generate shock waves in a range of 300 - 500 atmospheres, and fluid waves in a range of 20 to 30 meters per second. This energy front erodes tissue in fluid anterior to the tip. The pulverized tissue is then removed along with fluid by irrigation, or by means of an aspirating pump that pulls the fluid up the lumen 16 and away form the operative area. This improved tip focuses erosion energy in front of its distal end making it more efficient.

The rounded outer edges 20, 22 prevent tissue injury and the 0.40 lumen allows this tip to be used to remove softer material by aspiration, thus obviating the need for other aspirating tips. This improved tip resists damage allowing the tip to be used many times before it needs to be replaced.

Another embodiment of a distal end 50 of a phacoemulsification tip according to the present invention is shown in Figures 3 and 4. The distal end 50 is provided with a focusing surface 52 to focus the ultrasonic acoustic shock waves to more efficiently produce microbubbles. In this embodiment, the focusing surface is define by a curved surface. Further, the curved surface in this embodiment is a round surface, or has a constant radius of curvature, as shown in Figure 3. The round focusing surface extends from the inner surface 54 of the lumen 56 to the end face 58 of the distal end 10. More specifically, the focusing surface is defined by a concave recess provided and centered in the end face 58 of the distal end 10. The apex of the concave surface opens into the lumen 56. Alternatively, the focusing surface 52 in this embodiment can be defined by a plurality of curve segments or flat facets, or combinations, which provide the same focusing effect as the curved surface illustrated in Figure 3. For example, the focusing surface 52 can be a curved faceted concave surface instead of smoothed curved surface as illustrated.

The distal end 50 in this embodiment can be provided with a rounded leading edge 60. The remaining portions of the outer edge can also be rounded. Further, the distal end 50 is preferably beveled, however, theoretically the end face could made to be perpendicular to the tip axis, and the concave recess set off angle into the perpendicular end face. For example, the focusing surface 52 can be made off angle by drilling into the end face at an angle incident to the end face. The size of the end face 52 can be reduced by increasing the diameter of the focusing surface. However, a sufficient rim thickness should be provided to prevent metal fatigue. Further, the curved focusing surface 52 can be Gaussian curved instead of rounded (concave) leaving a rim defined by end face 58.

The distal end is further characterized by an inner diameter 62, an outer diameter 64, a wall thickness 66, and a rim thickness 67, as shown in Figure 4. The rim thickness 67 is preferably 0.03 to 0.10 mm, and optimally 0.03 mm. The rim thickness need not be the same throughout the circumference of the tip.

The focusing surface 52 of this embodiment provides a larger surface area for generating a greater number of transient microbubbles. This distal end can be manufactured by providing a flat beveled end to the tip by cutting, grinding and/or other known metal working techniques. The flat end face is recessed, for example, by using a ball drill. A further embodiment of the distal end 100 of a phacoemulsification needle tip is shown in Figures 5 and 6. This embodiment illustrates the most advanced phase of development of distal ends according to the present invention. In this embodiment, a focusing surface 102 is provided at the end of the distal end 100. The focusing surface 102 can be a continuous curved surface or a faceted curve surface, or combination of these surfaces. Optimally, the focusing surface 102 is defined by a Gaussian curved (normal curved) surface to maximize the focusing of the ultrasonic acoustic waves in theory. This particular embodiment can also be provided with rounded edges 104 to prevent metal burr formation and injury to eye tissue during insertion and operation. The curved surface of the focusing surface 102 extends from the inner surface 106 of the lumen 108 to the rounded edges 104. Unlike the other embodiments illustrated, there exists no flat end face due to the continuous curved nature of the focusing surface 102. This type of curved surface is designed to generate a focal point F_l of acoustic wave energy. The shock and fluid energy front generated by this tip is expected to extend a few millimeters to theoretical focus point F2. The distal end 100 can be furthered defined as a cylinder having an inner diameter 110, an outer diameter 112, and a rim thickness 114. The rim thickness 114 is preferably in the range of 0.030 to 0.10 mm depending upon the manufacturing technique. The distal ends of the phacoemulsification tips according to the present invention can be manufactured by known metallurgy techniques. However, new methods of manufacture may include utilizing more stress resistant titanium alloys plus diamond honing of the interior and exterior surfaces of the tip. This honing will reduce harmonic restitution and lesser metal fatigue. Such honing will also improve dimensional tolerances thus providing better acoustic functioning, and corresponding shock wave generation.

EXAMPLE

A phaco tip was prepared with polished and rounded edges, and a 0.40 mm lumen. The end face of the tip was faceted with a smooth circular surface by application of an approximately 1.08 mm diameter round ball drill leaving a smooth edged rim of approximately 0.50 mm width. SETTINGS FOR STORZ PREMIER PHACO

A. Initial grooves and crater made with 20% linear phaco and 50 mm Hg fixed vacuum.

B. Deep grooves made with the same settings, division of nucleus done by cross instrument cracking.

C. Loose pieces eroded with tip in center of the bag.

D. Soft peripheral cataract eroded with 5% fixed phaco power and 200 mm Hg linear vacuum. E. Irrigation aspiration done with the same tip with 200 mm Hg vacuum and completed with split irrigation aspiration manual method using side ports at 3 and 9 to maintain optical quality of the cornea.

SETTINGS FOR ALCON 10,000 PHACO

A. Initial grooves made with 50% phaco power, softer material at near end of surgery removed with 20 to 40% power and vacuum 120 mm Hg with pump at 20cσ/min.

CLINICAL OBSERVATIONS

1. Focused phaco tip erodes hard cataract nuclei with a groove the width of the tip because energy wave is focused anterior to it with little shock energy wave directed laterally. This concentrated energy front permits erosion with only 20% maximum phaco power with the Storz Premier, and 50% with the Alcon 10,000. These are very low levels that protect the eye tissue from excess energy. The smoothed polished surface of the tip generates a better focus of acoustic waves. 2. Few air bubbles are released form bss solution presumably because the energy wave is concentrated more by the faceted face and smooth polished surfaces of the tip.

3. Use of 5% fixed phaco power with maximum 200 mm Hg vacuum allows nuclear fragments to be held by the faceted face before small amount of phaco energy is given to erode the fragment. Also, little movement of nuclear fragments (i.e. chatter) was observed with Storz Premier.

4. Focused phaco tip works well for 1A of cortex and is safer because edges are not sharp. The extra smooth polish of the tip allows greater safety when working on or near the capsule or Descemefs.

5. The smooth rounded edges reduces the risk of stripping Descemet's as the tip enters the edge via small incisions.

6. The tip shows no sign of metal damage with sharp burr formation after 150 procedures.

7. The same tip is used to aspirate soft cataract protein and even softer material in the cataract periphery (cortex) . This shortens the time needed for surgery.

8. It has been noted that the tip creates a narrower groove in a hard nucleus as compared to a prior art 0.91 lumen tip, and fewer macrobubbles of air are released from the salt solution when this tip is used. 9. The amount of energy that needs to be delivered to the tip by the phaco console is less than that required if a prior art tip is used on the same device.

SUMMARY

The tested phaco tip performed as theorized. It reduces the amount of phaco energy needed to accomplish nucleus erosion, thus reducing the risk to eye tissue. It's smooth surface and edges and the faceted face deliver a better acoustic focus and protects Descemet's membrane and capsule from injury. It is believed that the recessed faceted face and absence of sharp edges protects the tip from damage during use.

OBSERVATION ON ACTION OF FOCUSED TIP COMPARED TO 0.90 mm STANDARD TIP DURING CATARACT REMOVAL

A standard 0.90 mm lumen phaco tip creates a rim of erosion of a very hard cataract directly contiguous to the narrow rim of the distal end of the tip. The result is that such a tip erodes its way into the cataract creating a "lollipop" effect. Many surgeons use this situation to impale portions of hard cataract nucleus on the phaco needle and pull the fragments to the center of the operative zone where it is safer to emulsify them.

The wide surface and rounded edges of an embodiment of the tip according to the present invention has been observed within the eye of the same patient to create a large amount of cataract particulate matter (i.e. lens milk) . Further, the tip does not erode into the hard cataract nucleus. At surgery, the surgeon waits for the cataract to pulverize without pushing the nuclear material toward the inferior part of the capsular bag risking its rupture. This distinct difference in how the two different tips erode hard nuclei supports the concept that the narrow rim version cuts or jack hammers into the cataract in front of the sharp narrow rim, whereas the wide faced, recessed and free of sharp edges tip generates a massive shock wave front that emulsifies the cataract without the so-called "lollipop" effect.

Claims

I CLAIM:

1. A phacoemulsification device, comprising: a needle having a distal end with a lumen, said distal end beveled, and including curvature means, extending around a perimeter of said lumen at said distal end, for increasing the generation of microbubbles and focusing Shockwaves to erode tissue.

2. A device according to Claim 1, wherein said lumen diameter is preferably in the range of 0.30 to 0.70 millimeters and the outer diameter of sai distal end is preferably in the range of 0.97 to 1.03 millimeters.

3. A device according to Claim 2, wherein said lumen diameter is most preferably in the range of 0.40 to 0.50 millimeters and said outer diameter is preferably in the range of 0.97 to 1.03 millimeters.

4. A device according to Claim 3, wherein said lumen diameter is approximately 0.40 millimeters and said outer diameter is approximately 1.00 millimeters.

5. A device according to Claim 1, wherein said distal end is provided with said beveled end set at an angle in the range of 15 to 60 degrees.

6. A device according to Claim 5, wherein said distal end is provided with said beveled end set at an angle preferably in the range of approximately 15 to 45 degrees.

7. A device according to Claim 6, wherein said beveled end is set at 30 degrees.

8. A device according to Claim 5, wherein said beveled end is flat.

9. A device according to Claim 5, wherein a portion of said beveled end is flat.

10. A device according to Claim 9, wherein said distal end is provided with an outer edge that is at least partially rounded.

11. A device according to Claim 9, wherein said beveled end is provided with a recess.

12. A device according to Claim 11, wherein said recess is defined by a curved surface.

13. A device according to Claim 12, wherein said curved surface is a continuous curved surface.

14. A device according to Claim 12, wherein said curved surface is a faceted curved surface.

15. A device according to Claim 12, wherein said recess surface is a concave surface.

16. A device according to Claim 1, wherein an end of said distal end is provided with a recess defining said curvature means.

17. A device according to Claim 16, wherein said distal end is provided with said recess.

18. A device according to Claim 16, wherein said recess is defined by a curved surface.

19. A device according to Claim 18, wherein said curved surface is a Gaussian curved surface.

20. A device according to Claim 19, wherein said distal end is provided with said recess in said beveled end.

21. A device according to Claim 18, wherein said curved surface is a continuous curved surface.

22. A device according to Claim 21, wherein said curved surface is a Gaussian curved surface.

23. A device according to Claim 18, wherein said curved surface is a faceted curved surface.

24. A device according to Claim 16, wherein said recess is defined by a concave surface.

25. A device according to Claim 1, wherein said lumen is centered in the distal end.

26. A phacoemulsification device, comprising: a needle having a distal end with a lumen, said distal end beveled, and including microbubble generation means for increasing the generation of microbubbles and curvature means, extending around a perimeter of said lumen at said distal end, for focusing Shockwaves generated for said distal end to enhance the erosion of tissue.

27. A device according to Claim 26, wherein said microbubble generation means is defined by a substantially wide end face.

28. A device according to Claim 26, wherein said microbubble generation means is at least partially defined by a focusing surface that focuses ultrasonic acoustic waves generated by microbubbles generated from said distal end during operation.

29. A device according to Claim 28, wherein said focusing surface is provided substantially as an end face of said distal end.

30. A device according to Claim 29, wherein said focusing surface is defined between said lumen and an outer surface of said distal end.

31. A device according to Claim 30, wherein at least a portion of said focusing surface is a continuous curved surface.

32. A device according to Claim 30, wherein at least a portion of said focusing surface is a faceted curved surface.

33. A device according to Claim 31, wherein at least a portion of said focusing surface is a faceted curved surface.

34. A device according to Claim 30, wherein said curved surface is a rounded surface.

35. A device according to Claim 30, wherein said curved surface is a Gaussian curved surface.

36. A device according to Claim 28, wherein said focusing surface is defined by a flat end face having rounded edges.

37. A device according to Claim 28, wherein said focusing surface is defined by said beveled end, said beveled end further including a flat face having rounded edges and a recess in the beveled flat end face.

38. A device according to Claim 28, wherein said focusing surface is defined by the beveled end, said bevel end further having rounded edges, and a continuous curve extending from said lumen to said rounded edges.

39. A device according to Claim 38, wherein said continuous curved surface is a Gaussian curved surface.

40. A device according to Claim 1, wherein said distal end is configured to focus shock waves generated by microbubbles formed at said distal end substantially towards one or more specific focal points.

41. A device according to Claim 1, wherein said lumen has a diameter in the range of approximately 0.25 to 0.75 millimeters, and said distal end having an outer diameter in the range of approximately 0.95 to 1.05 millimeters.

42. A phacoemulsification device, comprising: a needle having a distal end with a lumen, said distal end defined by an outer perimeter rounded edge and including curvature means for focusing Shockwaves to erode eye tissue.

43. A device according to Claim 42, wherein said curvature means extends around said lumen.

44. A device according to Claim 43, wherein said curvature means is continuous around said lumen.

45. A device according to Claim 44, wherein said curvature means is defined by an annular curved surface extending from said lumen to said outer perimeter rounded edge.

46. A device according to Claim 42, wherein said distal end is provided with a wide end face for increasing a surface area thereof to increase the generation of microbubbles.

47. A device according to Claim 46, wherein said curvature means extends around the lumen.

48. A device according to Claim 47, wherein said wide end face is defined by said curvature means, and said curvature means is continuous and defined by an annular curved surface extending from said lumen to said outer perimeter rounded edge.

49. A device according to Claim 42, wherein said inner lumen diameter is preferably in the range of 0.30 to 0.70 millimeters and said outer diameter is preferably in the range of 0.97 to 1.03 millimeters.

50. A device according to Claim 46, wherein said inner lumen diameter is preferably in the range of 0.30 to 0.70 millimeters and said outer diameter is preferably in the range of 0.97 to 1.03 millimeters.

51. A device according to Claim 42, wherein said distal end is provided with a beveled end set at an angle preferably in the range of approximately 15 to 45 degrees.

52. A device according to Claim 51, wherein said beveled end is flat.

53. A device according to Claim 42, wherein said distal end is provided with an outer edge that is at least partially rounded.

54. A device according to Claim 42, wherein said curvature means is defined by a recess in an end face of said distal end.

55. A device according to Claim 46, wherein said recess is defined by a curved shock wave focusing surface.

56. A method of performing phacoemulsification of eye tissue, comprising the steps of: focusing Shockwaves with a phaco tip at eye tissue to be removed without continuous contact therewith.

57. A method according to Claim 56, wherein the phaco tip does not substantially contact the eye tissue providing an essentially contactless mechanism for deteriorating tissue.

58. A method according to Claim 56, including the step of increasing the generation of microbubbles to enhance the generation of Shockwaves and the effectiveness of the method.

59. A method according to Claim 58, wherein the generation of microbubbles is increased by increasing the surface area of an end face of the phaco tip.

60. A method according to Claim 56, wherein the shock waves are focused by providing a focusing surface on the phaco tip.

61. A method according to Claim 59, wherein the shock waves are focused by providing a focusing surface on the phaco tip that converges the Shockwave to a single focus point.