Abstract:
A surgical handpiece having an active flow restrictor responsive to a feedback loop that can vary the fluid flow resistance through the handpiece.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to the field of eye surgery and more particularly to the field of cataract surgery.  
         [0002]     Phacoemulsification is a well-known process that refers to the use of a phacoemulsification machine that generates ultrasonic sound waves at the tip of a handpiece phacoemulsification machines are particularly useful in cataract surgery, for example, where it is necessary to remove a cataract lens from an eye. The tip is placed into the eye and specifically against the lens or cataract of the eye where the ultrasonic energy emulsifies the lens. The tip is hollow and emulsified pieces of the cataract are aspirated into an aspiration port formed at an end of the tip for removal from the eye. The aspirated cataract material flows through the tip, through channels within the handpiece and into an aspiration line connected to the phacoemulsification machine while fluid flows into the eye through an infusion line and an infusion sleeve formed around the tip to maintain the eye&#39;s pressure and shape.  
         [0003]     Aspiration is driven by pumps housed within the phacoemulsification machine and infusion is typically generated by gravity. The fluid infused into the eye through the infusion sleeve also serves to suspend particles of lenticular debris within the infused fluid and the suspension is then aspirated through the aspiration line back to the phacoemulsification machine where it is collected in a receptacle. The flow created in the aspiration line generates a vacuum or negative pressure in the aspiration line and at the handpiece tip. The vacuum holds the lens material against the aspiration port of the tip where the material is emulsified.  
         [0004]     The stronger the vacuum force is that holds the material against the aspiration port, i.e., “holdability”, the more efficient emulsification becomes. Additionally, increasing holdability allows the surgeon to manipulate lens material within the handpiece tip more easily. Holdability increases with vacuum level and aspiration port size. Therefore, higher vacuum levels and larger aspiration ports lead to more efficient phacoemulsification. However, these parameters also risk sudden collapse of the anterior chamber of the eye as fluid rapidly rushes into the aspiration port due to the large aspiration port area and the high vacuum.  
         [0005]     For example, during aspiration of the lenticular debris, the handpiece tip often becomes occluded with this debris. When it does, the vacuum level within the aspiration line builds to a high level. Eventually, the ultrasonic sound waves at the tip emulsify the debris, freeing the occlusion at the tip and resulting in an “occlusion break”. Fluid then rapidly rushes into the aspiration port and aspiration line to satisfy the high vacuum built up in the tip and the aspiration line. This can create negative pressure in the anterior chamber relative to the posterior segment of the eye. When this occurs, the anterior chamber can collapse or the posterior capsule can shift anteriorly, both being undesirable during intraocular surgery, perhaps resulting in complications such as posterior capsule rupture.  
         [0006]     To reduce the potential surge inflow of fluid in the aspiration line resulting from an occlusion break at the tip, emulsification tips have been manufactured in the past with a narrow lumen within the shaft of the tip that allows the surgeon to increase vacuum levels while limiting the sudden inflow of fluid in the aspiration line following an occlusion break. However, in these tip designs, the narrow portion of the lumen often becomes occluded with debris resulting in a complete loss of negative pressure or holdability at the aspiration port of the tip. The occlusion can be broken by refluxing fluid, prolonged application of ultrasonic energy or sometimes by increasing the vacuum level in the aspiration line. However, these techniques either increase the risk of complications, such as thermal injury to ocular tissues, or decrease efficiency of the emulsification surgical procedure. Additionally, these tip designs tend to have thinner walls than standard tips and are relatively fragile and more prone to breakage.  
         [0007]     Thus, there is a need for a phacoemulsification system and/or handpiece that reduces the danger of sudden post occlusion surge inflow of fluid within the aspiration line following an occlusion break. There is still also a need for a phacoemulsification system that minimizes the risk of injury to the human eye during a phacoemulsification surgical procedure.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention addresses the deficiencies in the prior art by providing a surgical handpiece having an active flow restrictor responsive to a feedback loop that can vary the fluid flow resistance through the handpiece.  
         [0009]     Accordingly, one objective of the present invention is to provide a surgical handpiece having an active flow restrictor.  
         [0010]     Another objective of the present invention is to provide a surgical handpiece that reduces the danger of sudden post occlusion surge inflow of fluid within the aspiration line following an occlusion break.  
         [0011]     Another objective of the present invention is to provide a phacoemulsification system that minimizes the risk of injury to the human eye during a phacoemulsification surgical procedure.  
         [0012]     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  
       [0013]      FIG. 1  is a perspective view of a surgical system that may be used with the present invention.  
         [0014]      FIG. 2  is a partial longitudinal cross-section of a first embodiment of the handpiece of the present invention illustrating the active flow restrictor in a first, less restricted position.  
         [0015]      FIG. 3  is a partial longitudinal cross-section of a first embodiment of the handpiece of the present invention illustrating the active flow restrictor in a second, more restricted position.  
         [0016]      FIG. 4  is a transverse cross-section of a first embodiment of the handpiece of the present invention taken at line  4 - 4  in  FIG. 2 .  
         [0017]      FIG. 5  is a transverse cross-section of a first embodiment of the handpiece of the present invention taken at line  5 - 5  in  FIG. 3 .  
         [0018]      FIG. 6  is a partial longitudinal cross-section of a second embodiment of the handpiece of the present invention illustrating the active flow restrictor in a first, less restricted position.  
         [0019]      FIG. 7  is a partial longitudinal cross-section of a second embodiment of the handpiece of the present invention illustrating the active flow restrictor in a second, more restricted position.  
         [0020]      FIG. 8  is a partial longitudinal cross-section of a third embodiment of the handpiece of the present invention illustrating the active flow restrictor in a first, less restricted position.  
         [0021]      FIG. 9  is a partial longitudinal cross-section of a third embodiment of the handpiece of the present invention illustrating the active flow restrictor in a second, more restricted position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     As best seen in  FIG. 1 , commercially available surgical systems generally include surgical console  110  having attached, adjustable mayo tray  10  and handpiece  20  attached to console  110  by aspiration tubing  22 , irrigation tubing  24  and power cable  26 . Power to handpiece  20  as well as the flows of irrigation and aspiration fluid is controlled by console  110 , which contains appropriate hardware and software, such as power supplies, pumps, pressure sensors, valves, all of which are well-known in the art.  
         [0023]     As best seen in  FIGS. 2 and 3 , handpiece  30  of the present invention may be of construction similar to that of conventional handpiece  20 , except handpiece  30  contains enlarged portion  32  and movable restrictor  34  that is moved within enlarged portion  32  by linear actuator  39 , pins  36  and slots  37 . As best seen in  FIGS. 4 and 5 , the shape of restrictor  34  and main flow channel  38  within handpiece  30  is such that regardless of the position of restrictor  34 , flow channel  38  remains rounded or oval. This is because a round or rounded geometry provides maximum flow per unit area with the least amount or parasitic fluidic losses.  
         [0024]     As best seen in  FIG. 2 , is a relaxed, or least restricted state, restrictor  34  is located near the bottom or enlarged portion  32  so that flow channel  38  has its widest cross-section area, thereby providing the least resistance to fluid flow. As best seen in  FIG. 3 , under circumstances directed by the user or pre-programmed into the software in console  110 , restrictor  34  can be elevated up into flow channel  38  by being moved linearly in both directions by linear actuator  39 , forcing slots  37  to ride up or down pins  36 , thereby restricting the cross-sectional area of flow channel  38 , as seen in  FIG. 5 , and increase the flow resistance in flow channel  38 . The movement of linear actuator  39  and the respective movement of restrictor  34  can be controlled in either direction via a feedback loop tied to pressure (vacuum) in flow channel  38  in an automated, pre-programmed manner, or to some other parameter under the control of the user of console  110 .  
         [0025]     Alternatively, as seen in  FIGS. 6 and 7 , linear movement of restrictor  34  by linear actuator  39  causes restrictor  34  it rotate eccentrically about pin  36 , thereby restricting the cross-sectional area of flow channel  38 .  
         [0026]     As best seen in  FIGS. 8 and 9 , in a second embodiment of the present invention, handpiece  130  may contain flow channel  138  having enlarged portion  132  and flow restrictor  134  more in the shape of a paddle that rotates on shaft  136 . Rotation of shaft  136  cause rotation of restrictor  134  from a first, position introducing little or no flow restriction in flow channel  138 , as seen in  FIG. 6 , to a position that introduces a varying amount of restriction within flow channel  138 , as seen in  FIG. 8 . The rotation of shaft  136  and the respective movement of restrictor  134  can be controlled via a feedback loop tied to pressure (vacuum) in flow channel  138  in an automated, pre-programmed manner, or to some other parameter under the control of the user of console  110 .  
         [0027]     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 restrictor of the present invention may be placed anywhere along the aspiration fluid pathway, such as in the cassette formed as part of the console.