Abstract:
A surgical handpiece having at least two lumens mounted to a body. At least one lumen is used for aspiration and at least one other lumen is used to inject heated surgical fluid for liquefying a cataractous lens. A portion of the second lumen is enlarged to form a pumping chamber. The pumping chamber works by boiling a small volume of the surgical fluid. As the fluid boils, it expands rapidly, thereby propelling the liquid downstream of the pumping chamber out of the second lumen. The pumping chamber may use a pair of electrodes, at least one of the electrodes containing a countersink.

Description:
This application is a continuation-in-part application of U.S. patent application Ser. No. 09/090,433, filed Jun. 4, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of cataract surgery and more particularly to a pumping chamber for a handpiece for practicing the liquefaction technique of cataract removal. 
     The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens. 
     When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL). 
     In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens. 
     A typical ultrasonic surgical device suitable for ophthalmic procedures consists of an ultrasonically driven handpiece, an attached cutting tip, and irrigating sleeve and an electronic control console. The handpiece assembly is attached to the control console by an electric cable and flexible tubings. Through the electric cable, the console varies the power level transmitted by the handpiece to the attached cutting tip and the flexible tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly. 
     The operative part of the handpiece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting tip during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece by flexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body&#39;s distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve. Ultrasonic handpieces and cutting tips are more fully described in U.S. Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583; 4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and 5,359,996, the entire contents of which are incorporated herein by reference. 
     In use, the ends of the cutting tip and irrigating sleeve are inserted into a small incision of predetermined width in the cornea, sclera, or other location. The cutting tip is ultrasonically vibrated along its longitudinal axis within the irrigating sleeve by the crystal-driven ultrasonic horn, thereby emulsifying the selected tissue in situ. The hollow bore of the cutting tip communicates with the bore in the horn that in turn communicates with the aspiration line from the handpiece to the console. A reduced pressure or vacuum source in the console draws or aspirates the emulsified tissue from the eye through the open end of the cutting tip, the cutting tip and horn bores and the aspiration line and into a collection device. The aspiration of emulsified tissue is aided by a saline flushing solution or irrigant that is injected into the surgical site through the small annular gap between the inside surface of the irrigating sleeve and the cutting tip. 
     Recently, a new cataract removal technique has been developed that involves the injection of hot (approximately 45° C. to 105° C.) water or saline to liquefy or gellate the hard lens nucleus, thereby making it possible to aspirate the liquefied lens from the eye. Aspiration is conducted with the injection of the heated solution and the injection of a relatively cool solution, thereby quickly cooling and removing the heated solution. This technique is more fully described in U.S. Pat. No. 5,616,120 (Andrew, et al.), the entire contents of which is incorporated herein by reference. The apparatus disclosed in the publication, however, heats the solution separately from the surgical handpiece. Temperature control of the heated solution can be difficult because the fluid tubings feeding the handpiece typically are up to two meters long, and the heated solution can cool considerably as it travels down the length of the tubing. 
     Therefore, a need continues to exist for a control system for a surgical handpiece that can heat internally the solution used to perform the liquefaction technique. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention improves upon the prior art by providing a surgical handpiece having at least two lumens mounted to a body. At least one lumen is used for aspiration and at least one other lumen is used to inject heated surgical fluid for liquefying a cataractous lens. A portion of the second lumen is enlarged to form a pumping chamber. The pumping chamber works by boiling a small volume of the surgical fluid. As the fluid boils, it expands rapidly, thereby propelling the liquid downstream of the pumping chamber out of the second lumen. The pumping chamber may use a pair of electrodes, at least one of the electrodes containing a countersink. 
     Accordingly, one objective of the present invention is to provide a surgical handpiece having at least two lumens. 
     Another objective of the present invention is to provide a surgical handpiece having a pumping chamber with two electrodes, at least one electrode containing a countersink. 
     Another objective of the present invention is to provide a surgical handpiece having a device for delivering the surgical fluid through the handpiece in pulses. 
     These and other advantages and objectives of the present invention will become apparent from the detailed description and claims that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front, upper left perspective view of the handpiece of the present invention. 
     FIG. 2 is a rear, upper right perspective view of the handpiece of the present invention. 
     FIG. 3 is a cross-sectional view of the handpiece of the present invention taken along a plane passing through the irrigation channel. 
     FIG. 4 is a cross-sectional view of the handpiece of the present invention taken along a plane passing through the aspiration channel. 
     FIG. 5 is an enlarged partial cross-sectional view of the handpiece of the present invention taken at circle 5 in FIG. 4. 
     FIG. 6 is an enlarged partial cross-sectional view of the handpiece of the present invention taken at circle 6 in FIG. 3. 
     FIG. 7 is an enlarged cross-sectional view of the handpiece of the present invention taken at circle 7 in FIGS. 3 and 4, and showing a resistive boiler pump. 
     FIG. 8 is an exploded, partial cross-section view of one embodiment of the handpiece of the present invention. 
     FIG. 9 is a block diagram of a control system that can be used with the handpiece of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Handpiece 10 of the present invention generally includes handpiece body 12 and operative tip 16. Body 12 generally includes external irrigation lumen 18 and aspiration fitting 20. Body 12 is similar in construction to well-known in the art phacoemulsification handpieces and may be made from plastic, titanium or stainless steel. As best seen in FIG. 6, operative tip 16 includes tip/cap sleeve 26, needle 28 and lumen 30. Sleeve 26 may be any suitable commercially available phacoemulsification tip/cap sleeve or sleeve 26 may be incorporated into other tubes as a multi-lumen tube. Needle 28 may be any commercially available hollow phacoemulsification cutting tip, such as the TURBOSONICS tip available from Alcon Laboratories, Inc., Fort Worth, Tex. Lumen 30 may be any suitably sized tubing to fit within needle 28, for example 29 gauge hypodermic needle tubing. 
     As best seen in FIG. 5, lumen 30 is free on the distal end and connected to pumping chamber 42 on the proximal end. Lumen 30 and pumping chamber 42 may be sealed fluid tight by any suitable means having a relatively high melting point, such as silver solder. Fitting 44 holds lumen 30 within bore 48 of aspiration horn 46. Bore 48 communicates with fitting 20, which is journaled into horn 46 and sealed with O-ring seal 50 to form an aspiration pathway through horn 46 and out fitting 20. Horn 46 is held within body 12 by O-ring seal 56 to form irrigation lumen 52 which communicates with irrigation lumen 18 at port 54. 
     As best seen in FIG. 7, in a first embodiment of the present invention, pumping chamber 42 contains a relatively small pumping reservoir 43 that is sealed on both ends by electrodes 45 and 47. Electrical power is supplied to electrodes 45 and 47 by insulated wires (not shown). In use, surgical fluid (e.g. saline irrigating solution) enters reservoir 43 through lumen 34 and check valve 53, suitable check valve 53 is well-known in the art. Electrical current (preferably RFAC) is delivered to and across electrodes 45 and 47 because of the conductive nature of the surgical fluid. As the current flows through the surgical fluid, the surgical fluid boils. As the surgical fluid boils, it expands rapidly out of pumping chamber 42 through lumen 30 (check valve 53 prevents the expanding fluid from entering lumen 34). The expanding gas bubble pushes the surgical fluid in lumen 30 downstream of pumping chamber 42 forward. Subsequent pulses of electrical current form sequential gas bubbles that move surgical fluid down lumen 30. The size and pressure of the fluid pulse obtained by pumping chamber 42 can be varied by varying the length, timing and/or power of the electrical pulse sent to electrodes 45 and 47 and by varying the dimensions of reservoir 43. In addition, the surgical fluid may be preheated prior to entering pumping chamber 42. Preheating the surgical fluid will decrease the power required by pumping chamber 42 and/or increase the speed at which pressure pulses can be generated. 
     Preferably, electrode 45 contains small depression or countersink 100 having any suitable depth but approximately 0.003 inches being preferred. Pumping reservoir 43 is narrowest at periphery 101 (on the order of 0.1 mm) and as a result, fluid in pumping reservoir 43 boils first at periphery 101 and the steam wave front travels down countersink 100 toward the central axis of lumen 30. The surgical fluid conducts electricity much better in the liquid state than in the vapor state. Consequently, current flow diminishes greatly at periphery 101 where boiling occurs first. 
     While several embodiments of the handpiece of the present invention are disclosed, any handpiece producing adequate pressure pulse force, rise time and frequency may also be used. For example, any suitable handpiece producing a pressure pulse force of between 0.03 grams and 3.0 grams, with a rise time of between 1 gram/sec and 3,000 grams/sec and a frequency of between 1 Hz and 200 Hz may be used, with between 10 Hz and 100 Hz being most preferred. The pressure pulse force and frequency may be varied with the hardness of the material being removed. For example, the inventors have found that a lower frequency with a higher pulse force is more efficient at debulking and removing the relatively hard nuclear material, with a higher frequency and lower pulse force being useful in removing softer epinuclear and cortical material. Infusion pressure, aspiration flow rate and vacuum limit are similar to current phacoemulsification techniques. 
     As seen in FIG. 9, one embodiment of control system 300 for use in operating handpiece 310 includes control module 347, RF amplifier 312 and function generator 314. Power is supplied to RF amplifier 312 by DC power supply 316, which preferably is an isolated DC power supply operating at ±200 volts. Control module 347 may be any suitable microprocessor, and may receive input from operator input device 318. Function generator 314 provides the electric wave form to amplifier 312 and preferably operates at 450 KHz to help minimize corrosion. 
     In use, control module 347 receives input from surgical console 320. Console 320 may be any commercially available surgical control console such as the LEGACY® SERIES TWENTY THOUSAND® surgical system available from Alcon Laboratories, Inc., Fort Worth, Tex. Console 320 is connected to handpiece 310 through irrigation line 322 and aspiration line 324, and the flow through lines 322 and 324 is controlled by the user via footswitch 326. Irrigation and aspiration flow rate information in handpiece 310 is provided to control module 347 by console 320 via interface 328, which may be connected to the ultrasound handpiece control port on console 320 or to any other output port. Control module 347 uses footswitch 326 information provided by console 320 and operator input from input device 318 to generate two control signals 330 and 332. Signal 332 is used to operate pinch valve 334, which controls the surgical fluid flowing from fluid source 336 to handpiece 310. Fluid from fluid source 336 is heated in the manner described herein. Signal 330 is used to control function generator 314. Based on signal 330, function generator 314 provides a wave form at the operator selected frequency and amplitude determined by the position of footswitch 326 to RF amplifier 312 which is amplified to advance the powered wave form to handpiece 310 to create heated, pressurized pulses of surgical fluid. 
     As best seen in FIGS. 3, 4 and 7, surgical fluid may be supplied to pumping chamber 43 through lumen 34 or, as seen in FIG. 8, surgical fluid may be supplied to pumping chamber 243 through irrigation fluid lumen 234 which branches off main irrigation lumen 235 supplying cool surgical fluid to the operative site. As seen in FIG. 8, aspiration lumen 237 may be contained internally to handpiece 10. 
     Any of a number of methods can be employed to order limit the amount of heat introduced into the eye. For example, the pulse train duty cycle of the heated solution can be varied so that the total amount of heated solution introduced into the eye does not vary with the pulse frequency. Alternatively, the aspiration flow rate can be varied as a function of pulse frequency so that as pulse frequency increases aspiration flow rate increases proportionally. 
     This description is given for purposes of illustration and explanation. It will be apparent to those skilled in the relevant art that changes and modifications may be made to the invention described above without departing from its scope or spirit. For example, it will be recognized by those skilled in the art that the present invention may be combined with ultrasonic and/or rotating cutting tips to enhance performance.