Patent Publication Number: US-2004049217-A1

Title: Apparatus and method for performing ophthalmic procedures

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a surgical system for cutting tissue.  
       [0003] 2. Description of Related Art  
       [0004] There are many surgical procedures that require the cutting and aspiration of tissue. For example, in a retina re-attachment procedure the surrounding vitreo tissue must be removed before the retina is repaired. The cutting device must be delicate enough to remove the tissue without further damaging the retina. Prior art ophthalmic cutting devices include an inner sleeve that moves relative to an outer port of an outer sleeve. The sleeves are coupled to a vacuum system which pulls tissue into the outer port when the inner sleeve moves away from the port. The inner sleeve then moves in a reverse direction past the outer port to sever the tissue in a guillotine fashion. The vacuum system draws the severed tissue away from the outer port so that the process can be repeated.  
       [0005] The inner sleeve is driven by a motor located within a hand piece that is held by the surgeon. The inner sleeve is typically coupled to the motor by a rotating lever mechanism. Rotating lever mechanisms of the prior art are relatively large and complex. Additionally, the stroke and duty cycle of the inner sleeve is fixed for each device. It would be desirable to provide a surgical guillotine cutter that is inexpensive to produce, small in size and would allow a surgeon to vary the stroke and duty cycle of the inner cutter.  
       [0006] Guillotine cutters are typically provided with a control system that allows the surgeon to vary the vacuum pressure of the aspiration line. U.S. Pat. Nos. 4,395,258; 4,493,698; 4,706,687 and 4,838,281 issued to Wang et al. and Rogers et al., respectively, disclose systems for controlling the vacuum pressure of a guillotine cutter. The Wang/Rogers systems include a solenoid actuated valve that is coupled to the hand piece and controls the flow of fluid in the aspiration system. The position of the valve and the corresponding vacuum of the system is controlled by an input signal provided to the solenoid by a control circuit. The input signal is typically the summation of a feedback signal and a control signal that is generated by a potentiometer. The feedback signal corresponds to the actual vacuum pressure measured in the system. The potentiometer is typically a foot pedal that is manipulated by the surgeon.  
       [0007] The surgeon controls the vacuum pressure by depressing the foot pedal and varying the amount of air flow through the solenoid control valve. Because of the inertia within the system, there is typically a lag between the input command of the surgeon and the actual variation of vacuum pressure at the tip of the cutter. It would be desirable to provide a vacuum control system that has a more rapid response time than systems of the prior art.  
       [0008] Additionally, prior art guillotine cutters typically do not have many control functions, or safety features to prevent inadvertent damage to the eye. For example, prior art systems do not automatically compensate for variations in the load on the cutter. The surgeon must observe a reduction in cutting rate and then manipulate the cutter and the vacuum pressure to overcome the increased load. Additionally, with a prior art cutter, if the cutter ceases to operate while the vacuum pressure is applied to the system, the tissue may be pulled into the aspiration port of the outer sleeve. Such an event may damage the eye. It would be desirable to provide a guillotine cutter which has a number of control functions and safety features.  
       [0009] Cutting tissue sometimes causes undesirable bleeding which must be coagulated. Coagulation can be performed with an electro-cautery device. To coagulate the tissue the cutter is removed and an electro-cautery device is inserted into the patient. To continue cutting, the electro-cautery device must be removed to allow re-insertion of the cutter. Such a procedure is time consuming and may reduce the safety of the procedure. It would be desirable to provide a cutter that can also cauterize tissue.  
       SUMMARY OF THE INVENTION  
       [0010] The present invention is a surgical cutting system. The cutting system includes a cutter which has an inner sleeve that moves adjacent to an aspiration port of an outer sleeve. The inner sleeve is coupled to a source of vacuum that pulls tissue into the outer port when the inner sleeve is moved away from the port. The inner sleeve then moves across the outer port and severs the tissue in a guillotine fashion. The tip of the inner sleeve may exert a spring force that assist in the cutting action of the cutter.  
       [0011] The cutter includes a motor which creates an oscillating translational movement of the inner sleeve. The motor can be controlled by a controller that is coupled a foot pedal. The foot pedal and controller can be configured so that the motor decreases speed as the pedal is depressed by the operator.  
       [0012] The inner sleeve is coupled to an aspiration line that pulls the severed tissue out of the cutter. The level of the aspiration vacuum pressure can be controlled by a variable regulator valve. The regulator valve is coupled to the controller and the foot pedal. The foot pedal may have a switch that allows the system to operate in either a variable speed mode or a variable pressure mode. In the variable speed mode the actuation of the foot pedal changes the speed of the motor. In the variable pressure mode the actuation of the foot pedal changes the vacuum level within the aspiration line.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein:  
     [0014]FIG. 1 is a cross-sectional view of surgical guillotine cutter of the present invention;  
     [0015]FIG. 2 is an enlarged cross-sectional view of the tip of the cutter;  
     [0016]FIG. 3 is an enlarged view similar to FIG. 2 showing tissue being drawn into an outer port of the cutter;  
     [0017]FIG. 4 is a an enlarged view similar to FIG. 2 showing an inner sleeve severing the tissue drawn into the outer port;  
     [0018]FIG. 5 is a schematic of a vacuum control system for the cutter;  
     [0019]FIG. 6 is a side cross-sectional view of an alternate cutter;  
     [0020]FIG. 7 is a side cross-sectional view of an alternate cutter;  
     [0021]FIG. 8 is a perspective view of a cutter system of the present invention which has an electrical generator coupled to a cutter;  
     [0022]FIG. 9 is an enlarged view of a cutter tip which functions as an electrode;  
     [0023]FIG. 10 is a schematic of a system for controlling the motor speed of a cutter;  
     [0024]FIG. 11 is a schematic of a system that terminates the vacuum supply when the cutter no longer cuts;  
     [0025]FIG. 12 is a schematic of a system that can terminate a flow of irrigation fluid;  
     [0026]FIG. 13 is a schematic of a system which contains a plurality of vacuum pumps;  
     [0027]FIG. 14 is a schematic of a system that contains a vacuum pressure pump and a positive pressure pump;  
     [0028]FIG. 15 is a schematic of a system that contains a pump which has electronically controlled intake and exhaust valves;  
     [0029]FIG. 16 is a schematic of a rotary valve that controls the flow of aspiration fluid;  
     [0030]FIG. 17 is a schematic showing a solenoid driven guillotine cutter;  
     [0031]FIG. 17 a  is a schematic of a solenoid that is coupled to an inner sleeve of a cutter by a spring;  
     [0032]FIG. 18 is a side view of a bent tip;  
     [0033]FIG. 19 is a side view of a tip that has a plurality of aspiration ports;  
     [0034]FIG. 20 is side view showing a transmitter that tracks the location of a cutter within tissue;  
     [0035]FIG. 21 is a schematic of an alternate embodiment of the system;  
     [0036]FIG. 22 is graph showing input signals to a motor;  
     [0037]FIG. 22 a  is a schematic view of a stop mechanism for a motor of the cutter;  
     [0038]FIG. 23 is a graph showing a feedback signal from the motor;  
     [0039]FIG. 24 is a side view of a slider and an inner sleeve;  
     [0040]FIG. 25 is a bottom view of the slider;  
     [0041]FIG. 26 is a perspective view of an alternate embodiment of the system;  
     [0042]FIG. 27 is a perspective view of an inner sleeve of the cutter;  
     [0043]FIG. 28 is a perspective view of an alternate embodiment of the inner sleeve;  
     [0044]FIG. 29 is a perspective view of an alternate embodiment of the inner sleeve.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0045] Referring to the drawings more particularly by reference numbers, FIGS. 1 and 2 show a surgical guillotine cutter  10  of the present invention. The cutter  10  is used to remove and aspirate tissue. For example, the cutter  10  can be used to remove intraocular tissue during an ophthalmic procedure to re-attach a retina of an eye. Although use in an ophthalmic procedure is described, it is to be understood that the cutter  10  can be used to cut and aspirate other tissue, such as removing polyps, fibroids and other vascularized human tissue.  
     [0046] Referring to FIG. 2, the cutter  10  includes an outer sleeve  12  that has an outer port  14 . The outer port  14  is in fluid communication with an inner channel  16  of the sleeve  12 . Located within the inner channel  16  of the outer sleeve  12  is an inner sleeve  18 . The inner sleeve  18  has an inner channel  20  that is in fluid communication with an aspiration system. The aspiration system creates a vacuum pressure that pulls tissue into the outer port  14  when the inner sleeve  18  is located away from the port  14 . The inner sleeve  18  moves within the inner channel  16  of the outer sleeve  12  to cut tissue that is pulled into the outer port  14  by the aspiration system.  
     [0047]FIGS. 3 and 4 show tissue  22  that is cut by the cutter  10 . The inner sleeve  18  is initially moved away from the outer port  14  and the vacuum pressure pulls tissue  22  into the port  14  and the inner channel  16 . The inner sleeve  18  then moves toward the outer port  14  and severs the tissue  22  within the inner channel  16 . The severed tissue is pulled through the inner channel  20  of the inner sleeve  18  by an aspiration system. The inner sleeve  18  then moves away from the outer port  14  wherein the cutting process is repeated.  
     [0048] The movement of the inner sleeve  18  also controls the flow of fluid through the outer port  14  and into the aspiration system. Increasing the cutting speed decreases the flow rate and vice versa. The flow of fluid through the opening  14  may vary the vacuum pressure within the aspiration system. In addition to varying the cutting speed the surgeon may also vary the vacuum pressure by changing the speed of the motor and the flow of fluid through the opening  14 . The cutting device  10  of the present invention can thus control the vacuum pressure within the aspiration system by controlling the oscillation speed of the inner sleeve  14 .  
     [0049] Referring to FIG. 1, the cutter  10  includes a motor  24  that is located within a hand piece  26 . Extending from an end of the motor  24  is a rotating output shaft  28 . The motor  24  is preferably an electrical device that is coupled to an external power source by wires  30  that are attached to a plug  32  screwed into the hand piece  26 . The rotational speed of the output shaft  28  is a function of the amplitude of an input signal that is provided by wires  30 . Although an electrical motor is described, it is to be understood that the motor may be a pneumatic device.  
     [0050] The cutter  10  has a wobble plate  34  that is attached to the output shaft  28  of the motor  24 . The wobble plate  34  is located within a groove  36  of a slider  38 . The slider  38  is attached to the inner sleeve  18 . Rotation of the output shaft  28  spins the wobble plate  34 , which induces an oscillating translational movement of both the slider  38  and the inner sleeve  18 . The motor  24  and wobble plate  34  move the inner sleeve  18  in an oscillating manner to cut tissue as shown in FIGS. 3 and 4.  
     [0051] The slider  38  moves within a bearing sleeve  40  that is captured by an inner cap  42  and an outer cap  44  of the cutter  10 . The outer cap  44  is screwed onto the hand piece  26 . The slider  38  may have an aperture  46  that extends therethrough to allow air to flow out of the area between the slider  38  and the inner cap  42 . The aperture  46  prevents the formation of a back pressure that may impede the movement of the slider  38 . The slider  38  further has a channel  48  that is coupled to an aspiration line  50  by a tube  52 . The channel  48  provides fluid communication between the aspiration line  50  and the inner channel  20  of the inner sleeve  18 .  
     [0052] The stroke and the duty cycle of the inner sleeve  18  are related to the cam angle and profile of the wobble plate  34 . The stroke and/or duty cycle can be varied by removing the cap  44  and replacing the wobble plate  34  with a new part which has a different cam angle and/or profile. The present invention thus allows a surgeon to readily change the duty cycle and stroke of the device  10 .  
     [0053]FIG. 5 shows a system  60  for controlling the vacuum pressure within the cutter  10 . The system includes a positive pressure source  62  which creates a positive pressure. The output of the positive pressure source  62  may be regulated by a regulator  64 . The regulator  64  may be coupled to a shut-off valve  66  that can de-couple the source  62  from the remaining portion of the system  60 . The wobble plate  34 , slider  38  and outer cap  44  are preferably constructed from an electrically insulative material so that an electrical current does not flow from the handpiece to the patient. The wobble plate  34 , slider  38  and outer cap  44  are preferably constructed from a molded plastic material.  
     [0054] The positive pressure created by the pump  62  is converted into a negative vacuum pressure by a converter  68 . The converter  68  may be a venturi pump that is relatively linear in operation. The system  60  may have a reservoir  70  that is coupled to the converter  68  and the aspiration line  50  of the cutter  10 . The converter  68  creates a vacuum pressure within the aspiration line  50  of the cutter  10 , to pull the tissue into the outer port  14  of the outer sleeve  12 , and to aspirate the severed tissue.  
     [0055] The system  60  includes a potentiometer  72  which provides a variable input signal to the motor  24  of the cutter  10 . The potentiometer  72  is typically a foot pedal which can be manipulated by the surgeon to vary the input signal and the speed of the motor  24 . Varying the speed of the motor  24  changes the oscillation frequency of the inner sleeve  18 , the flow of fluid through the outer port  14  and the vacuum pressure within the system. The surgeon can therefore control the flow of fluid through the aspiration system by manipulating the foot pedal  72  and varying the motor speed of the cutter  10 .  
     [0056] The potentiometer  72  may be coupled to the motor by a control circuit  74 . The control circuit  74  is coupled to the output of a differential amplifier  76 . One input of the differential amplifier  76  is coupled to a transducer  78  that senses the vacuum pressure within the system. The transducer  78  provides an output signal that corresponds to the magnitude of the vacuum pressure. The other input of the differential amplifier  76  may be connected to a vacuum limit control  80  which limits the level of the vacuum pressure. The differential amplifier  76  and transducer  78  provide a closed loop feedback signal for the aspiration system.  
     [0057] The control circuit  74  compares the feedback signal provided by the differential amplifier  76  with the control signal provided by the potentiometer  72  and generates the input signal for the aspiration system. The control circuit  74  typically adds, the difference between the feedback signal and the control signal from the foot pedal, to the control signal. The control circuit  74  may include a differential amplifier and adder connected as shown in U.S. Pat. No. 4,838,281, which is hereby incorporated by reference. The system  60  may include a variable cut rate limit control circuit  82  that limits the amplitude of the motor input signal and allows the surgeon to control the minimum and maximum cutting speed of the cutter  10 .  
     [0058] The system  60  may have a first solenoid exhaust valve  84  that bleeds off the vacuum line to decrease the magnitude of the vacuum pressure. The valve  84  may be coupled to the control circuit  74  to lower the magnitude of the vacuum pressure when the actual pressure level exceeds a desired pressure level. The system  60  may also have a second solenoid exhaust valve  86  that quickly returns the system to atmospheric pressure. The shut-off valve  66  and second exhaust valve  86  can be coupled to the potentiometer  72  so that the shut-off valve  66  is closed and the exhaust valve  86  is opened when the surgeon releases the foot pedal  72  and moves the potentiometer to an off position. Returning the system to atmospheric pressure prevents a sudden vacuum surge when the surgeon again utilizes the cutter  10  at a surgical site.  
     [0059] The system  10  may also have an off detect circuit  88  which drives the motor  24  and moves the inner sleeve  18  to close the outer port  14  when the surgeon releases the foot pedal  72 . Closing the outer port  14  prevents the residual vacuum of the system from pulling in tissue when the cutter  10  has been inactivated. The detect circuit  88  may drive one of the motor coils when the foot pedal is released to move the inner sleeve  18  to an extended position that closes the outer port  14 .  
     [0060] In operation, a surgeon may insert the outer sleeve  12  into an eye to perform an ophthalmic procedure. The surgeon may remove intraocular tissue by depressing the foot pedal  72  and initiating the cutting action of the cutter  10 . The cutting speed and fluid flow can be varied by manipulating the foot pedal  72  and varying the motor speed of the cutter. Valving the vacuum pressure at the outer port  14  of the cutter provides an almost instantaneous response time for varying the fluid flow at the surgical site. Releasing the foot pedal  72  closes the shut-off valve  66  and opens the exhaust valve  88  to return the system  60  to atmospheric pressure.  
     [0061] By way of example, the aspiration line  50  and/or reservoir  70  may be directly coupled to the intake port of a linear pump. The potentiometer  72  and/or control circuit  74  may provide an input signal to control the output of the linear pump and the vacuum pressure within system. The linear pump may be a device sold by Medo of Woodale, Ill. under the part designation VP0660. In this embodiment, the vacuum pressure may also be further regulated by controlling the motor speed of the cutter  10 .  
     [0062] Although a control circuit  74  is shown and described, it is to be understood that the foot pedal  72  can be connected directly to the motor  24  without a feedback input. Additionally, although a foot pedal  72  is shown and described, it is to be understood that the motor  24  could be controlled by a handpiece or other input device.  
     [0063]FIG. 6 shows an alternate embodiment of a cutter  100 . The cutter  100  includes an outer sleeve  102  and an inner sleeve  104 . The outer sleeve  104  has an aspiration port  106  that is in fluid communication with an inner channel  108 . The inner sleeve  104  is driven in a reciprocating manner by a motor (not shown). Movement of the inner sleeve  104  cuts tissue  110  that is pulled into the aspiration port  106 .  
     [0064] The inner sleeve  104  has a circumferential slit  112  that allows the distal end of the sleeve  104  to bend toward the aspiration port  106  when engaging and cutting the tissue  110 . The bending of the inner sleeve  104  assist in cutting the tissue  110 .  
     [0065]FIG. 7 shows another embodiment of a flexible cutter  120  which has a flexible outer sleeve  122  and a flexible inner sleeve  124 . The outer sleeve  122  has an aspiration port  126  that is in fluid communication with an inner channel  128 . The outer sleeve  122  is preferably constructed from a flexible plastic or curved metal material that can bend and conform to the shape of a body passage or cavity. The inner sleeve  124  is preferably constructed from a metal material that can cut tissue pulled into the aspiration port  126 .  
     [0066] The inner sleeve  124  has a plurality of circumferential slits  130  that reduce the stiffness of the sleeve  124 . The slits  130  allow the inner sleeve  124  to follow the shape of the outer sleeve  122 . The most distal slit  130  allows the distal end of the inner sleeve  124  to bend into the aspiration port  126  to assist in the cutting of the tissue  110 . The flexible cutter  120  can function as a cutting catheter that is inserted into cavities and passages of a body. For example, the flexible cutter  120  can be used to cut polyps, fibroids and other vascularized human tissue.  
     [0067]FIG. 8 shows a cutter  130  coupled to a radio frequency (RF) electrical generator  132 . The cutter  130  includes a tip  134  that is connected to a motor (not shown) located within a handpiece  136 . The handpiece  136  has an aspiration line  138  that is coupled to a vacuum source (not shown). The handpiece  136  is coupled to the generator  132  by a pair of connectors  140  and  142 . One of the connectors  140  provides power to the motor. The other connector  142  supplies electrical energy to the tip  134  so that the surgeon can cauterize tissue with the cutter  130 . The electrical energy may be controlled by a foot pedal (not shown) that can be manipulated by the surgeon.  
     [0068] A surgeon can thus both cut and cauterize tissue with the same device. By way of example, the cutter  130  may be used to cut polyps or fibroids in a laparoscopic procedure. The generator  132  may have a plurality of control functions that allow the surgeon to vary the frequency, pulse rate or time duration of electrical energy provided to the cutter  130 .  
     [0069]FIG. 9 shows the cutter tip  134  constructed as an electrode. The tip  134  has an inner sleeve  144  that reciprocates across an aspiration port  146  within an inner channel  148  of an outer sleeve  150 . The tip  134  also has an outer conductive layer  152  that is separated from the outer sleeve  150  by a layer of insulation  154 . The outer conductive layer  152  is covered with an layer of insulation  156 . The outer sleeve  150  and outer conductive layer  152  are connected to electrical terminals of the generator  132 . Electrical current flows through tissue between the outer sleeve  150  and the outer conductive layer  152 .  
     [0070] As an alternate embodiment, the inner sleeve  144  can be connected to the generator  132  instead of the outer sleeve  150 . The cutter  130  may then provide pulses of current to the tissue as the inner sleeve  144  reciprocates across the aspiration port  146 . The system may also have a voice system which provide input on the present mode of the system. By way of example, the system may provide an audio indication that the electro-cautery function is active, or provide an audio indication that the some component was not set-up or assembled correctly.  
     [0071]FIG. 10 is a schematic of a system  160  which controls the motor speed of a motor  162  and a tip  164 . In general the system  160  provides more power to the motor  162  with an increase in the load on the tip  164 . For example, when the tip  164  engages a more fibrous tissue, the resistance of the tissue will slow down the tip  164  and the motor  162 . The system  160  senses the reduction in speed and automatically increases the power to the motor  162 .  
     [0072] The motor  162  is preferably a brushless DC motor device which contains three coils that drive an internal rotor (not shown). The system  160  includes a motor controller  166  that provides power to the motor  162 . The motor controller  166  preferably provides three sinusoidal drive signals to the coils of the motor  162 . The sinusoidal signals provide a relatively smooth control of the motor.  
     [0073] The system  160  has a differential amplifier  168  that senses the input voltage of the motor  162  on line  170  and the output current of the motor  162  on line  172 . The output of the differential amplifier provides a feedback control signal to the motor controller  166  on line  174 . The system  160  monitors the speed of the motor  162  by sensing the output current. It being understood that the current may increase or decrease with a change in motor speed. The system  160  varies the input voltage to the motor  162  to maintain a constant voltage to current ratio and compensate for different loads on the motor. Although a differential amplifier is shown and described, it is to be understood that the system may control the power provided to the motor as a function of speed in a variety of ways. For example, the motor may contain a Hall sensor that directly measures the speed of the motor and provides a feedback signal that is processed by the motor controller  166  to increase power with a reduction in motor speed.  
     [0074]FIG. 11 shows an alternate embodiment of a system  180  which automatically disconnects the cutter  182  from a vacuum source  184  when the cutter  182  is no longer cutting. The system  180  prevents the vacuum source  184  from pulling tissue into the aspiration port of the cutter  182  when the inner sleeve is no longer reciprocating relative to the port. Continued aspiration while the cutter  182  is no longer properly functioning may result in tissue damage.  
     [0075] The system  180  includes a speed (RPM) sensor  186  which senses the speed of the cutter motor. The sensor  186  provide a feedback signal to a controller  188 . The controller  188  controls a solenoid actuated on/off valve  190  located between the vacuum source  184  and a vacuum reservoir  192 . When the motor speed falls below a threshold level the controller  188  drives the valve  190  to an off position to terminate the flow of aspiration fluid from the cutter. When the cutting speed increases above the threshold value the controller  188  opens the valve  190  to resume normal operation.  
     [0076]FIG. 12 shows a fluid irrigation system  200  that provides irrigation fluid to the patient. In an ophthalmologic procedure the irrigation fluid is typically introduced to the cornea through a secondary incision.  
     [0077] The system  200  includes a fluid reservoir  202  that typically provides fluid through the force of gravity to a tip  204  located within the patient. The flow of irrigation fluid from the fluid reservoir  202  to the patient is controlled by a valve  206 . The valve  206  may be a solenoid actuated on/off device that is controlled by a foot pedal  208 . The foot pedal  208  can be manipulated by the surgeon to control the flow of irrigation fluid to the patient. As an alternate embodiment, the valve  206  may be a proportional device that allows the surgeon to control the amount of irrigation fluid that flows to the patient.  
     [0078]FIG. 13 shows a vacuum control system  210  that contains a plurality of vacuum sources  212 ,  214 ,  216  and  218  connected in parallel with a vacuum reservoir  220  and a cutter  222 . The multiple vacuum sources are actuated sequentially to provide greater flowrate and sensitivity than a single unit system.  
     [0079] The system  210  includes a vacuum transducer  224  that senses the vacuum pressure provided to the cutter  222 , and a foot pedal  226  that allows the surgeon to control the vacuum pressure. The output of the transducer  224  and the foot pedal  226  are provided to a differential amplifier  228 . The amplifier  228  provides an error signal that is processed by a controller  230 . The controller  230  provides control signals to actuate and control the vacuum sources  212 ,  214 ,  216  and  218 . In the preferred embodiment, the vacuum sources are variable speed diaphragm vacuum pumps.  
     [0080] In operation, the controller  230  may actuate and drive one of the pumps  212 ,  214 ,  216  or  218 . The surgeon may request a lower vacuum pressure by depressing the foot pedal  226 . Depressing the foot pedal  226  varies the error signal provided by the differential amplifier  228 . The controller  230  processes the error signal and actuates, or changes the speed, one or more of the inactive vacuum pumps to decrease the vacuum pressure provided to the cutter  222 . Further depressing the foot pedal may induce the actuation of the other pumps and so forth and so on. The controller  230  may also vary the speeds of the pumps  212 ,  214 ,  216  and  218  to further obtain a desired vacuum level. As an alternate embodiment, the system may have a plurality of orifices that each have a different diameter. The different orifices can be coupled to one or more pumps.  
     [0081]FIG. 14 shows an alternate embodiment of the system shown in FIG. 13. The intake and exhaust lines of pump  214  are switched so that the pump provides a positive pressure to the vacuum reservoir  220 . The positive pressure source  214  allows the controller  230  to rapidly increase the pressure within the system when the surgeon releases the foot pedal  226 . The push-pull dual pump configuration provides a vacuum system with a quick response to commands for increasing or decreasing the vacuum pressure.  
     [0082]FIG. 15 is another alternate embodiment of a vacuum system with an electronically controlled pump assembly  240 . The pump assembly  240  includes an intake valve  242  and an exhaust valve  244  that control the flow of fluid from a pumping assembly  246 . The pump assembly  246  may contain a flexible diaphragm or piston that pumps fluid within an internal pumping chamber of the assembly. The intake valve  242  is open during an intake stroke of the pumping assembly  246  and closed during an exhaust stroke of the assembly  246 . Conversely, the exhaust valve  244  is closed during the intake stroke and open during the exhaust stroke.  
     [0083] The valves  242  and  244  are preferably solenoid actuated devices that are driven by the controller  230 . The controller  230  can vary the timing on the opening and closing of the valves  242  and  244  to control the flowrate through the pump assembly  246  and the vacuum pressure provided to the cutter  222 . As an alternate embodiment, the valves  242  and  244  may be proportional devices that allow the controller  230  to control the flowrate and vacuum pressure of the system.  
     [0084]FIG. 16 is a valve  250  that can control the vacuum pressure provided to a cutter  252  from a vacuum source  254  and reservoir  255 . The valve  250  includes a core  256  that rotates within a valve housing  258 . The core  256  has an inner channel  260  that periodically becomes aligned with an inlet port  262  and an outlet port  264  of the valve housing  258 . Fluid flows through the valve  250  when the inner channel  260  is aligned with the ports  262  and  264 . The core  256  can be rotated by a motor  266  that is controlled by a controller  268 . The motor  266  can vary the rotational speed of the core  256 . Varying the core speed changes the flowrate through the valve  250  and the vacuum pressure provided to the cutter  252 . The valve  250  can be utilized in a system that does not control the vacuum pressure by varying the speed of the cutter.  
     [0085]FIG. 17 is an alternate embodiment of a variable port cutter  270 . The cutter  270  includes an outer sleeve  272  that has an aspiration port  274  in fluid communication with an inner channel  276 . An inner sleeve  278  is located within the inner channel  276  of the outer sleeve  272 . Mounted to the outer sleeve  272  is a first solenoid  280  and a second solenoid  282 . The solenoids  280  and  282  are connected to a controller  284  and coupled to the outer sleeve  272  by a magnetic core  286 .  
     [0086] The controller  284  provides a current to one of the solenoids  280  and  282  which creates a electromagnetic force on the inner sleeve  272 . The first solenoid  280  is wound to move the inner sleeve  278  toward the aspiration port  274 . The second solenoid  282  moves the sleeve  278  away from the port  274 . The controller  284  sequentially drives the solenoids  280  and  282  to reciprocate the inner sleeve  278  across the aspiration port  274 . The controller  284  can provide control signals to the solenoids  280  and  282  to control how far the inner sleeve  278  moves across the port  274  and the size of the aspiration opening. For example, the controller  284  may control the solenoids so that the inner sleeve  278  moves only half-way across the aspiration port  274 . The variation in sleeve movement will change the flowrate within the inner channel  276 .  
     [0087]FIG. 17 a  shows another embodiment of a surgical cutter which has a single solenoid. The solenoid includes an armature  287  that moves relative to a coil  288 . The armature  287  is coupled to an inner sleeve  289  by a cantilevered spring  290 . The movement of the spring  290  is limited by a stop  291 . The stop  291  also limits the movement of the inner sleeve  289  relative to the outer sleeve  292 . The stop  291  prevents the inner sleeve  289  from striking the end of the outer sleeve  292 .  
     [0088] In operation, the coil  288  is energized to move the armature  287 . The armature  287  moves the spring  290  and the inner sleeve  289 . When the coil  288  is de-energized the spring  290  moves the inner sleeve  289  back to the original position. As an alternate embodiment the coil  288  may move relative to a stationary magnet.  
     [0089]FIG. 18 shows a tip  295  which has a bend at the proximal end. When inserted through an incision to perform an ophthalmic procedure, the bent tip  295  may provide more transverse energy to the eye without damaging the incision. The bent tip  295  may utilize the flexible inner sleeve shown in FIG. 7.  
     [0090]FIG. 19 shows an alternate embodiment of a cutter  300  which has an outer sleeve  302  that has a plurality of aspiration ports  304  that are in fluid communication with an inner channel  306 . The cutter  300  further has an inner sleeve  308  that is reciprocated by a motor (not shown) to cut tissue pulled into the aspiration ports. The multiple aspiration ports  304  are desirable when removing large amounts of tissue. By way of example, such a cutter  300  would be preferable when performing a liposuction procedure.  
     [0091]FIG. 20 shows a transmitter  310  that monitors the location of a cutter  312  placed within tissue  314 . The transmitter  310  may provide audio frequency (sonar) waves that are received by the cutter  312 . The transmitter  310  and cutter/receiver  312  can be coupled to a computer  316  which processes the transmitted signals to determine the location of the cutter  312  within the tissue  314 .  
     [0092]FIG. 21 shows an alternate embodiment of a surgical system  400 . The system  400  may include a handpiece  402  which contains a variable electric motor  404  that moves an inner sleeve  406  relative to an outer sleeve  408 . The outer sleeve  408  has an aspiration port  409 . The inner sleeve  406  can be coupled to the motor  404  by a wobble plate and slider assembly that is the same or similar to the configuration depicted in FIG. 1.  
     [0093] The motor  404  is coupled to a controller  410 . The controller  410  can be a microprocessor that is coupled to a memory device(s)  411 . The controller  410  performs software routines and computations in accordance with instructions retrieved from memory  411 . The instructions may be embedded in ROM, stored on a mass storage device and/or retrieved from an external source such as a floppy disk, and/or downloaded from a network.  
     [0094] The controller  410  is coupled to a foot pedal  412 . The foot pedal  412  can be depressed from an upward position to a downward position. The foot pedal  412  may contain a microprocessor (not shown) which generates digital signals that are transmitted to an RS-232 interface (not shown) coupled to the controller  410 . The controller  410  interprets the input signal(s) from the foot pedal  412  and provides output signals to drive the motor  404 , typically in accordance with a software routine. Alternatively, the foot pedal  412  may have a potentiometer or other sensor (not shown) that provides an output signal which varies with the position of the pedal.  
     [0095] In one embodiment, the software routine of the controller  410  provides output signals so that the motor  404  and inner sleeve  406  are moving at a maximum speed when the pedal  412  is in the upward position. By way of example, the maximum speed may be 2500 cuts per minute (cpm). The software routine may be such that the controller  410  reduces the speed of the motor  404  when the foot pedal  412  is depressed by an operator. The foot pedal  412  can be depressed to a point where the motor  404  operates at a minimum speed. By way of example, the minimum speed may be 1000 cpms. The upper and lower speed limits may be adjustable through a control button(s) (not shown) on a console (not shown) that houses the electronics of the system. Providing the maximum cutting speed at the released position of the foot pedal  412  insures that the inner sleeve  406  is operating at a safe condition when the operator releases the pedal. At slower speeds the cutter tends to pull and tear tissue. The motor  404  may be turned off when the operator releases the foot pedal  412 . A slight depression of the pedal  412  energizes the motor  404  to the maximum speed. A further depression of the pedal reduces the speed of the motor  404 .  
     [0096] The controller  410  may be coupled to the motor  404  by a source sink driver circuit  418  and a low pass filter  420 . Although one controller  410  is shown and described, it is to be understood that there may be an additional controller (not shown) that is dedicated to the motor  404  and coupled to the driver circuit  418  and a main controller. The source sink driver  418  provides output signals that correspond to the different phases Ø1, Ø2 and Ø3 of the motor  404 . The low pass filter  420  filters the output of the driver circuit  418 . The controller  410  provides output signals to the driver  418  which define the shape of the waveform generated by the circuit  418 .  
     [0097]FIG. 22 shows an output waveform for one phase of the driver circuit  418 . The processor controlled driver circuit  418  may initially provide a short pulse separated from a longer pulse by a relatively long interval. The driver circuit  410  provides a series of gradually increasing pulses separated by gradually decreasing time intervals until a maximum pulse is provided to the motor  404 . The driver circuit  410  then provides a series of gradually increasing pulses separated by gradually increasing time intervals. The low pass filter  420  filters the output of the driver circuit  418  to create the sine-wave (shown in dashed lines) which is provided to the motor  404 . The controller  410  can thus control the motor  404  without a digital to analog (D/A) converter.  
     [0098] As shown in FIG. 21, the motor  404  may have a sensor  416  that provides a motor position feedback signal to the controller  410 . The controller  410  may utilize the feedback information in computing the output signals for the motor  404 . The software routine may be such that the controller  410  drives the motor  404  so that the inner sleeve  406  is at a predetermined start and/or stop position relative to the outer sleeve  408 . By way of example, the inner sleeve  406  may be stopped in a position to close the port  409  of the outer sleeve, or stopped in a position that opens the outer sleeve port, or any other intermediate position. The start position may be the same as the stop position.  
     [0099] As shown in FIG. 22 a , the motor  404  may contain three coils  421  and a four pole magnetic rotor  422  that is coupled to the inner sleeve of the cutter. The rotor  422  may have two adjacent N magnetized poles and two adjacent S magnetized poles. The motor  404  may have a stop magnet  423  which is magnetized to attract the N poles and repel the S poles. Thus when the motor  404  is stopped the stop magnet  423  will always orient the rotor  422  in the position shown in FIG. 22 a . The attached inner sleeve of the cutter will therefore always stop in the same position. By way of example, the inner sleeve may always stop in an open port position. The motor  404  may have an additional stop magnet  424  that is magnetized to attract the S poles of the rotor  422 .  
     [0100] The conventional Hall Effect sensors that are typically located in a quadrant of the motor may be removed. An external two pole magnet (not shown) may be connected to the rotor and coupled to the sensor  416 . The sensor may be a single Hall Effect sensor. The two pole magnet rotates with the motor rotor relative to the Hall Effect sensor  416 .  
     [0101]FIG. 23 shows a digital feedback signal of the motor sensor  416 . The sensor  416  provides a “high” output signal when the motor  404  is in the first  180   of  rotation and a “low” output when the motor rotates through the next  1800 . The controller  410  utilizes the feedback signal to determine the position of the motor  404  and the timing of the commutation signals.  
     [0102] When the motor  404  is stopped the controller  410  may enter a routine to initially determine the motor position from the feedback signal. If the motor  404  is not in the desired start/stop position the controller  410  can provide the appropriate output signals to move the motor  404  into the desired start/stop position.  
     [0103] The controller  410  can also provide load compensation for the motor  404 . The controller  410  can compare a desired motor movement with the actual movement of the motor  404  from the feedback signal of the sensor  416 , and then vary the output signals of the driver  418  to compensate for any discrepancy between the desired and actual values. For example, the controller  404  can provide signals to adjust the current to the motor by comprising a lead or lag between the feedback signal from the sensor  416  with a desired value. Referring to FIG. 22, the controller  410  may change the frequency and/or width(s) of the pulses to vary the amount of energy provided to the motor  404  to compensate for varying motor loads.  
     [0104] Referring to FIG. 21, the inner sleeve  406  of the handpiece can be coupled to a vacuum source  425  and a vacuum reservoir  426  by a vacuum line  427 . The pressure of the vacuum line  426  and reservoir  425  are controlled by a variable regulator valve  428 . The valve  428  may be a device sold by Coast Pneumatics of Fullerton, Calif. under the product designation V800.  
     [0105] The valve  428  has an electronic interface  430  that is coupled to the controller  410 . The controller  410  provides output signals to the interface  430  to control the position of the valve  428  and the pressure within the vacuum line  427 .  
     [0106] The system may further have a pressure transducer  432  that is coupled to the controller  410 . The pressure transducer  432  provides a feedback signal that corresponds to the actual pressure within the vacuum line  427 . The controller  410  may have a closed loop feedback routine to vary the output signals to the regulator valve  428  to insure that the vacuum pressure is maintained at a desired level or within a desired bandwidth.  
     [0107] The controller  410  may operate to control the effective size of the port  409  and the cutting action of the device. The controller  410  can vary the effective port opening by changing the commutation signals so that the motor  404  does not rotate 360° and the inner sleeve  406  does not move to the full distal position. By way of example, the controller  410  can drive the motor  404  to rotate 90° in a clockwise direction and then drive the motor 90° in a counterclockwise direction so that the inner sleeve  406  moves one-half of the full sleeve stroke.  
     [0108] The foot pedal  412  may have a switch(es)  434  which allows the system to operate in one of two modes. In one mode, referred to as a variable speed mode, the controller  410  varies the speed of the motor  404  through the operator input of the pedal  412 . When the variable speed mode is selected the operator can vary the speed of the motor by depressing the pedal  412 . The vacuum pressure is typically held at a constant level in this mode.  
     [0109] In another mode, referred to as a variable pressure mode, the controller  410  varies the vacuum pressure of the system through the valve  428  in response to input through the foot pedal  412 . In this mode, the operator is allowed to vary the vacuum pressure of the system through the pedal  412 . The speed of the motor  404  is typically held at a constant level in this mode.  
     [0110] The system may further have an exhaust valve  436  that is connected to the vacuum line  424 . The exhaust valve  436  can be opened to rapidly return the system to atmospheric pressure. The software routine may be such that the exhaust valve  436  is opened and the motor  404  is no longer driven when the controller  410  determines that the motor  404  is no longer moving the inner sleeve  406 . Such a mode of operation prevents vacuum pressure within line  426  from pulling tissue into the device if the motor  404  malfunctions or some other event prevents the inner sleeve  406  from the moving.  
     [0111]FIGS. 24 and 25 show an alternate embodiment of a slider  450  that is attached to an inner sleeve  452 . The slider  450  has a groove  454  that receives a wobble plate (not shown) of a handpiece. The wobble plate can be the same or similar to the component shown in FIG. 1. The slider  450  has a pair of flat keying surfaces  456  that cooperate with corresponding surfaces of the handpiece to insure that the inner sleeve  454  is assembled in a correct orientation. To insure that the slider  454  can be readily attached to the wobble plate the controller  410  moves the motor  404  to a start position when the motor  404  is turned off so that the wobble plate is aligned with the groove  454 .  
     [0112]FIG. 26 shows an alternate embodiment of a system which has a console  460  that contains the motor  404  and the electronics to operate the system. The motor  404  is coupled to a wobble plate or other inner sleeve drive mechanism within a handpiece  462  by a cable  464 . The motor  404  rotates the cable  462 . The cable  462  actuates the drive mechanism and induces a cutting action of the surgical device. The cable  464  may be located within a protective sheath  466 . Placing the motor  404  within the console  460  may reduce the size and vibration of the handpiece  462 .  
     [0113]FIG. 27 shows an alternate embodiment of an inner sleeve  470  which has a tip  472  that exerts a spring force on an outer sleeve  474 . The inner sleeve  470  has a lip  476  located adjacent to an aspiration port  478  of the outer sleeve  474 . The lip  476  is bent at the base  480  so that the tip  472  is slightly deflected in a direction toward the outer sleeve  474 . The bend and amount of spring deflection can be varied for different inner sleeves. Different tissues may be severed more effectively with different spring forces. With the present invention, a surgeon may assemble an inner sleeve  470  which has a spring force that is optimal for a particular tissue.  
     [0114]FIG. 28 shows another inner sleeve  490  which has a pair of longitudinal slits  492  in the tip  494  to create two lips  496 . The lips  496  are bent in an outward radial direction to create a spring deflection of the tip  494 . The length and/or width of the slits  492  can be varied to change the spring force of the tip  494 .  
     [0115]FIG. 29 shows an alternate embodiment of an inner sleeve  500  which has two longitudinal slits  502  which create a spring lip  504 . The spring lip  504  is typically located opposite an aspiration port  506  of an outer sleeve  508 . The lip  504  exerts a spring force that pushes the tip  510  of sleeve  500  toward the outer sleeve  508 . The spring force of the lip  504  can be varied for different inner sleeves  500 .  
     [0116] While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.