Abstract:
A control system for a Liquefracture handpiece that uses output from a surgical console to generate a control signal for an RF amplifier. The output from the RF amplifier is used to drive the handpiece heating element. To prevent excessive heated fluid from entering the eye, the vacuum in the handpiece is monitored and excessive or rapid increases in vacuum level (indicating an occlusion or low aspiration flow) causes the power to the heating element to be reduces or eliminated.

Description:
This application is a continuation-in-part application of U.S. patent application Ser. No. 09/130,403 now abandoned, filed Aug. 6, 1998, which is a continuation-in-part application of U.S. patent application Ser. No. 09/090,433, now U.S. Pat. No. 6,080,128 filed Jun. 4, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of cataract surgery and more particularly to a control system for a handpiece for practicing the Liquefracture 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 fiction 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 Liquefracture technique. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention improves upon the prior art by providing a control system for a Liquefracture handpiece. The system uses output from a surgical console to generate a control signal for an RF amplifier. The output from the RF amplifier is used to drive the handpiece heating element. To prevent excessive heated fluid from entering the eye, the vacuum in the aspiration tubing is monitored and excessive or rapid increases in vacuum level (indicating an occlusion) causes the power to the heating element to be reduces or eliminated. 
     Accordingly, one objective of the present invention is to provide a surgical console control system. 
     Another objective of the present invention is to provide a surgical console control system that generates a control signal for an RF amplifier. 
     Another objective of the present invention is to provide a surgical console control system that provided a drive signal for a Liquefracture handpiece. 
     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 a schematic cross-sectional view of a heating element boiler pump that may be used with the present invention. 
     FIG. 9 is an exploded, partial cross-section view of one embodiment of the handpiece of the present invention. 
     FIG. 10 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 tubing  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 tubing  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. Tubing  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, tubing  30  is free on the distal end and connected to pumping chamber  42  on the proximal end. Tubing  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 tubing  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 tubing  18  at port  54 . 
     As best seen in FIG. 7, in a first embodiment of the present invention, pumping chamber  42  contains a relatively large 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  49  and  51 , respectively. In use, surgical fluid (e.g. saline irrigating solution) enters reservoir  43  through port  55 , tubing  34  and check valve  53 , check valves  53  being well-known in the art. Electrical current (preferably Radio Frequency Alternating Current or 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 port  57  and into tubing  30  (check valve  53  prevents the expanding fluid from entering tubing  34 ). The expanding gas bubble pushes the surgical fluid in tubing  30  downstream of pumping chamber  42  forward. Subsequent pulses of electrical current form sequential gas bubbles that move surgical fluid down tubing  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. 
     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 50.0 grams (between 1 gram and 50.0 grams being preferred), with a rise time of between 1 gram/second and 50,000 grams/second (with between 500 grams/second and 50,000 grams/second being preferred) 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 best seen in FIG. 8, the fluid in reservoir  143  in pumping chamber  142  may also be heated by the use of heating element  145  that is internal to reservoir  143 . Heating element  145  may be, for example, a coil of 0.003 inch diameter stainless steel wire which is energized by power source  147 . The size and pressure of the fluid pulse obtained by pumping chamber  142  can be varied by varying the length and timing of the electrical pulse sent to element  145  by control module  147  and by varying the dimensions of reservoir  143 . 
     As seen in FIG. 10, one embodiment of control system  300  for use in operating handpiece  310  includes control module  347 , power gain RF amplifier  312  and fiction generator  314 . Power is supplied to RF amplifier  312  by DC power supply  316 , which preferably is an isolated DC power supply operating at several hundred volts, but typically ±200 volts. Control module  347  may be any suitable microprocessor, micro controller, computer or digital logic controller and may receive input from operator input device  318 . Function generator  314  provides the electric wave form in kilohertz to amplifier  312  and typically operates at around 450 KHz or above 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 THOUSANDS® 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 output 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 tubing  34  or, as seen in FIG. 9, surgical fluid may be supplied to pumping chamber  243  through irrigation fluid tubing  234  which branches off main irrigation tubing  235  supplying cool surgical fluid to the operative site. As seen in FIG. 9, aspiration tubing  237  may be contained internally to handpiece  10 . 
     Referring back to FIG. 10, any of a number of methods can be employed in 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. In addition, any unexpected excessive or sharp increase in vacuum level in line  324  can indicate an occlusion or low flow in line  324 . Reduced aspiration flow in line  324  may allow excessive heat build up within the surgical site. To prevent excessive heated fluid from entering the eye in the event of an occlusion in handpiece  310 , aspiration flow rate information in line  324  is provided to control module  347  by console  320  via interface  328 . Based on a sensed occluded or low flow condition, control module  347  can reduce or cut off the output of amplifier  312 , thereby reducing or eliminating the heated fluid entering the surgical site. 
     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.