Abstract:
An improved foot controller of a microsurgical system, and a method of operating the foot controller, are disclosed. The method involves using a computer to modulate a detent of the foot controller from the beginning of the detent to the end of the detent.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally pertains to foot controllers used in the operation of microsurgical systems. The present invention more particularly pertains to an improved, surgeon definable detent for such foot controllers.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    Various foot controllers are used to control microsurgical systems, and particularly ophthalmic microsurgical systems. During ophthalmic surgery, a surgeon views the patient&#39;s eye through an operating microscope. To control the microsurgical system and its associated handpieces during the various portions of the surgical procedure, the surgeon must either instruct a nurse how to alter the machine settings on the surgical system, or use the foot controller to change such settings. Where possible, many surgeons prefer to use the foot controller to alter the machine settings on the surgical system, eliminating or reducing the need to converse with a nurse during the surgical procedure.  
           [0003]    Many conventional foot controllers have a foot pedal that provides linear control of the functions of the surgical system or an associated handpiece, and a series of switches or buttons that provide binary control of such functions. Exemplary foot controllers for ophthalmic microsurgical systems are disclosed in International Publication Number WO 00/12037; International Publication Number WO 99/14648; International Publication Number WO 98/08442; International Publication No. WO 96/13845; U.S. Pat. No. 5,983,749; U.S. Pat. No. 5,580,347; U.S. Pat. No. 4,837,857; U.S. Pat. No. 4,983,901; U.S. Pat. No. 5,091,056; U.S. Pat. No. 5,268,624; U.S. Pat. No. 5,554,894, all of which are incorporated herein by reference.  
           [0004]    Such foot controllers typically have a foot pedal that is capable of movement by the surgeon in a given range of motion. This range of motion is typically segregated into several areas, each of which controls a different surgical mode. For example, moving a foot pedal into a first area may provide a fixed amount of irrigation flow to a phacoemulsification handpiece. Moving the foot pedal into a second area may provide fixed irrigation flow and linear control of aspiration flow to the handpiece. Moving the foot pedal into a third area may provide fixed irrigation flow, linear control of aspiration flow, and linear control of ultrasound power to the handpiece. Each of these areas is typically separated by a relatively small range of foot pedal travel (and/or a small amount of time) in which the surgeon feels increased resistance against his or her foot as it presses on the pedal. These small ranges of foot pedal travel are typically referred to as detents. The increased resistance felt by a surgeon&#39;s foot as the foot pedal passes through a detent is typically provided by an increase in torque generated by the detent motor of the foot controller that opposes the force of the surgeon&#39;s foot on the foot pedal. Once the surgeon moves the pedal through a detent, the resistance felt by the surgeon&#39;s foot decreases. U.S. Pat. No. 4,983,901; U.S. Pat. No. 4,168,707; U.S. Pat. No. 5,091,656; U.S. Pat. No. 6,179,829; and European Patent No. 0 789 929 B1, all of which are incorporated herein by reference, disclose examples of such detents.  
           [0005]    However, conventional foot controllers suffer from the disadvantage that the force necessary to overcome a detent and move to the next surgical mode results in the foot pedal having a somewhat stiff feeling to the surgeon. If the force required to overcome the detent is decreased in amplitude to reduce such stiffness, the detent becomes difficult for the surgeon to detect. Therefore, a need still exists for an improved detent in foot controllers used in the operation of microsurgical systems.  
         SUMMARY OF THE INVENTION  
         [0006]    In one aspect, the present invention is an improved method of operating a foot controller of a microsurgical system. A microsurgical system having a computer and a foot controller operatively coupled to the computer is provided. The foot controller has a foot pedal with a range of motion. The range of motion has a first area indicative of a first surgical mode of the microsurgical system and a second area indicative of a second surgical mode of the microsurgical system. The first and second areas are separated by a detent. The computer is used to modulate the detent by varying a resistance felt by a user&#39;s foot as it presses on the foot pedal. The varying of the resistance may occur at a given frequency from the beginning of the detent to an end of the detent. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    For a more complete understanding of the present invention, and for further objects and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings in which:  
         [0008]    [0008]FIG. 1 is a perspective view of a microsurgical system according to a preferred embodiment of the present invention;  
         [0009]    [0009]FIG. 2 is a block diagram of certain portions of the microsurgical system of FIG. 1 and its associated foot controller according to a preferred embodiment of the present invention;  
         [0010]    [0010]FIG. 3 is perspective view of a preferred embodiment of the foot controller of FIGS.  1 - 2 ;  
         [0011]    [0011]FIG. 4 is a side, partially cut away view of the foot controller of FIG. 3 in a fully undepressed position;  
         [0012]    [0012]FIG. 5 is a side view of the foot controller of FIG. 3 in a fully depressed position;  
         [0013]    [0013]FIG. 6 schematically illustrates the resistive force felt by a surgeon&#39;s foot as it presses on the foot pedal of the foot controller of FIG. 3 as a function of the rotational displacement of the foot pedal according to a preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 7 schematically illustrates a modulating detent of the foot controller of FIG. 3 according to a preferred embodiment of the present invention; and  
         [0015]    [0015]FIG. 8 shows a preferred embodiment of a touch screen display of the microsurgical system of FIG. 1 used to customize the modulating detent of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    The preferred embodiments of the present invention and their advantages are best understood by referring to FIGS. 1 through 8 of the drawings, like numerals being used for like and corresponding parts of the various drawings.  
         [0017]    FIGS.  1 - 2  show a microsurgical system  10  according to a preferred embodiment of the present invention. As shown in FIG. 1, microsurgical system  10  is an ophthalmic microsurgical system. However, microsurgical system  10  may be any microsurgical system, including a system for performing otic, nasal, throat, or other surgeries. System  10  is capable of providing ultrasound power, irrigation fluid, and aspiration vacuum to a ultrasonic handpiece in an anterior segment ophthalmic surgical procedure. System  10  may also be capable of providing pneumatic drive pressure and aspiration vacuum to a vitrectomy probe and irrigation fluid to an infusion cannula in a posterior segment ophthalmic surgical procedure. System  10  preferably includes a graphic user interface  12  having a liquid crystal display (“LCD”)  16  with touch screen capability, a footswitch interface controller  18  disposed within a body  19  of system  10 , a force feedback driver  20  disposed within body  19 , and a foot controller  26 . Controller  18  is a computer and is preferably a microcontroller. Driver  20  is preferably a variable current source driver. A surgical cassette is operatively coupled to system  10  via cassette receiving area  27  to manage the fluidics of system  10  in the conventional manner. As mentioned above, a series of handpieces are operatively coupled to system  10 , and/or its surgical cassette, during ophthalmic surgery, typically via conventional flexible plastic tubing fluidly coupled with the surgical cassette and/or electronic cabling operatively coupled to one or more of ports  29 . Exemplary handpieces utilized in anterior segment ophthalmic surgery include an irrigation handpiece, an irrigation/aspiration handpiece, an ultrasonic handpiece, and/or a diathermy handpiece. A preferred ultrasonic handpiece is a phacoemulsification handpiece. Exemplary handpieces utilized in posterior segment ophthalmic surgery include an extrusion handpiece, an infusion cannula, a victrectomy probe, microsurgical scissors, and/or a diathermy handpiece.  
         [0018]    As shown best FIGS.  3 - 5 , foot controller  26  has a body  48  with a base  50  that supports foot controller  26  on the operating room floor. Body  48  preferably includes a foot pedal or treadle  52 , a heel cup  54 , and side or wing switches  56 , all of which can be made from any suitable material, such as stainless steel, titanium, or plastic. Base  50  may also contain a protective bumper  58  made from a relatively soft elastomeric material. The structure of foot controller  26  is more completely described in co-pending U.S. appplication Ser. No. 10/271,505 filed Oct. 16, 2002, which is incorporated herein by reference.  
         [0019]    Foot pedal  52  and heel cup  54  are rotationally coupled to body  48  at a shaft  66  of foot controller  26 . Foot pedal  52  may be depressed using the upper portion of a surgeon&#39;s foot to move from a fully undepressed position as shown in FIGS.  3 - 4 , to a fully depressed position as shown in FIG. 5. Ankle axis of rotation  60  of foot  62  is preferably located behind shaft  66 . Although not shown in FIGS.  3 - 5 , foot controller  26  may be designed so that only foot pedal  52 , and not heel cup  54 , rotates about shaft  66 , if desired. Foot pedal  52  is used by the surgeon to provide proportional control to certain functions of microsurgical system  10 . By way of example, depending on the operating mode of system  10 , foot pedal  52  may be used to provide proportional control of vitrectomy probe cut rate, vitrectomy probe aspiration vacuum, ultrasound handpiece power, or ultrasound handpiece aspiration flow rate.  
         [0020]    As shown in best in FIG. 2, foot controller  26  preferably also includes a force feedback motor  30  and an encoder  32 . Motor  30  is mechanically coupled to shaft  66  via a conventional gear assembly (not shown). Motor  30  is driven by a signal generated by force feedback driver  20  and controlled by footswitch interface controller  18 . Encoder  32  is preferably an optical encoder. Encoder  32  monitors the number of rotations of the shaft of motor  30 . Encoder  32  includes position detect logic  33  capable of transforming the number of rotations of the shaft of motor  30  into the rotational displacement of foot pedal  52 . One or more foot pedal return springs  34  are also coupled to shaft  66 . Springs  34  and motor  30  combine to provide a torque or force that resists actuation of foot pedal  52  by a surgeon&#39;s foot. Switches  36 ,  38 , and  40  detect and signal controller  18  upon the failure of spring  34 , upon the tilting of foot controller  26  off its base  50 , and when foot pedal  52  is in a fully undepressed position, respectively. Foot controller  26  may be made using conventional technology. Foot controller  26  is electrically coupled to microsurgical system  10  via electronic cable  28 .  
         [0021]    [0021]FIG. 6 schematically illustrates the resistive force felt by a surgeon&#39;s foot as it presses on foot pedal  52  to control various surgical parameters during operation of microsurgical system  10  as a function of the rotational displacement of foot pedal  52 . As shown in the preferred embodiment of FIG. 6, foot controller  26  has a range of motion between a first position where foot pedal  52  is in a fully undepressed position and a second position where foot pedal  52  is in a fully depressed position. This range of motion is preferably separated into multiple sub-ranges or areas, each of which is indicative of a surgical mode of system  10 . For an exemplary phacoemulsification handpiece operatively coupled to system  10 , the preferred areas are: 0 (no active surgical mode); 1 (fixed amount of irrigation flow provided to handpiece); 2 (fixed amount of irrigation flow provided to handpiece+proportional (0-100%) control of aspiration flow provided to handpiece); and 3 (fixed amount of irrigation flow provided to handpiece+proportional (0-100%) control of aspiration flow provided to handpiece+proportional (0-100%) control of ultrasound power provided to handpiece). Of course, different numbers of areas, as well as different surgical modes, may be assigned for different microsurgical systems other than system  10  and/or different handpieces operatively coupled to system  10 . As shown in FIG. 6, foot controller  26  preferably has two detents  100  and  102  as foot pedal  52  is moved in a downward direction, and two detents  104  and  106  as foot pedal  52  is moved in an upward direction. Of course, more or less detents, or different detent locations, may be utilized, if desired.  
         [0022]    As shown in FIGS.  7 - 8 , one or more of detents  100  through  106  may be a modulating detent. More specifically, the resistance, or resistive force or torque, that a surgeon feels against his or her foot as it presses on foot pedal  52  is preferably varied from a first value of amplitude F 0  at the beginning D 0  of the detent to values of amplitude between a second value of amplitude F 1  and a third value of amplitude F 2  at a desired frequency throughout the entire detent. At the end D 1  of the detent, the resistance preferably returns to the first value of amplitude F 0 . This modulating detent is significantly different from a conventional foot switch detent, in which the surgeon feels a constant, increased resistance against his or her foot as he or she continues to move the foot pedal of the foot controller from the beginning to the ending of the detent. The modulating detent of the present invention is preferably accomplished by using force feedback driver  20  to vary the electrical signal to force feedback motor  30  so that the opposing torque provided to shaft  66  varies while foot pedal  52  is between the beginning D 0  of the detent and the end D 1  of the detent. Of course, encoder  32  and position detect logic  33  provide the current rotational displacement of foot pedal  52  to footswitch controller  18 , and controller  18  instructs driver  20  on how to appropriately vary the electrical signal to motor  30 .  
         [0023]    The surgeon or nurse may use touch screen display  16  of system  10  to customize the feel of detents  100  through  106 . For example, the surgeon may touch button  108  to activate modulation on all detents  100  through  106 , and the surgeon may touch button  110  to deactivate modulation on all detents  100  through  106 . As another example, a surgeon may increase the frequency of modulation of all detents  100  through  106  by touching scroll up arrow  112 , and the surgeon may decrease the frequency of modulation of all detents  100  through  106  by touching scroll down arrow  114 . As the frequency of modulation of the detents is changed, the current frequency is qualitatively displayed by the position of scrolling bar  116  within bar display  118 . In addition, the surgeon or nurse may also change the frequency of modulation of detents  100  through  106  by using a mouse connected to user interface  12  to “click and drag” scrolling bar  116  within bar display  118 . The absolute value of the difference in the amplitudes F 1  and F 2  of the resistance felt by a surgeon&#39;s foot, as well as the minimum and maximum values for the frequency of modulation of the detents, is preferably hard coded within footswitch controller  18 . The preferred value of such minimum and maximum values for the frequency of modulation are about 30 Hz to about 150 Hz. Alternatively, these values could be customized by the surgeon or the nurse using touch screen display  16 . In addition, the resistance that a surgeon feels against his or her foot may be modulated between F 0  and F 1 , between F 0  and F 2 , or with some other varying pattern, if desired. Preferably, the pattern of modulation is hard coded within footswitch controller  18 . Alternatively, a surgeon or nurse could select from multiple modulation patterns, or customize a modulation pattern, using touch screen display  16 . The duration of each of detents  100  through  106  is preferably about 100 milliseconds.  
         [0024]    From the above, it may be appreciated that the present invention provides a surgeon with an improved detent in foot controllers used in the operation of microsurgical systems. The present invention eliminates the stiffness felt by the surgeon when the surgeon moves the foot pedal of a foot controller through a conventional detent.  
         [0025]    The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. For example, graphic user interface  12  may be used to set a different frequency of modulation for different detents of foot controller  26 . In addition, although the modulating detents of the present invention have been described above in connection with a foot pedal  52  having a generally vertical range of motion, the modulating detents of the present invention are applicable to a foot pedal having a generally horizontal range of motion or a range of motion with a different orientation other than vertical or horizontal.  
         [0026]    It is believed that the operation and construction of the present invention will be apparent from the foregoing description. While the apparatus and methods shown or described above have been characterized as being preferred, various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.