Abstract:
An instrument sheath that can be inserted into an incision formed in tissue. The sheath may protect the tissue from mechanical, thermal and other forms of trauma. The application also includes a blade guide that can be used to form an incision.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a sheath that can be inserted into an incision of tissue and provides mechanical and thermal protection to the tissue from an instrument that passes through the sheath. The present invention also relates to a blade guide that guides a blade to form an incision.  
           [0003]    2. Background Information  
           [0004]    There has been developed a medical procedure commonly referred to as phacoemulsification (“phaco”) that is performed to remove a cataractous lens. A phaco procedure includes the steps of making an incision in the cornea and inserting a tip that is manipulated by a surgeon to break and remove the lens. The tip is typically driven by an ultrasonic device which imparts a vibratory energy to the lens. The tip extends from a handpiece that is coupled to an irrigation line and an aspiration system. The irrigation line provides an irrigation fluid to the anterior chamber of the cornea. The aspiration system pulls the irrigation fluid and emulsified lens from the cornea.  
           [0005]    [0005]FIG. 1 shows a typical surgical instrument  1  used to perform a phaco procedure. The surgical instrument  1  includes an outer irrigation sleeve  2  that is attached to an outer case  3  of the instrument  1 . An ultrasonically driven tip  4  extends from the case  3  and through the sleeve  2 . The vibrating tip  4  is used to emulsify the lens of a cornea  5 .  
           [0006]    The case  3  has an irrigation inlet port  6  that is connected to an irrigation line (not shown). The irrigation line provides an irrigation fluid to the instrument. The outer sleeve  2  is separated from the tip  4  to create a channel  7  that allows irrigation fluid to flow from the inlet port  6 , through an outlet port (not shown) in the sleeve  2  and into the cornea. The tip  4  has an aspiration channel  8  that is connected to an aspiration system. The irrigation fluid and emulsified lens are drawn through the channel  8 .  
           [0007]    The irrigation fluid must be delivered at a sufficient pressure and flowrate to maintain the intraocular pressure of the eye without damaging ocular tissue. It is desirable to provide an incision opening that is large enough to allow the tip  4  and sleeve  2  to be inserted into the cornea without allowing excessive irrigation fluid to leak back out of the anterior chamber.  
           [0008]    The corneal tissue about the incision may exert a pressure that creates frictional contact between the inner surface of the sleeve and the oscillating tip. The frictional contact between the sleeve and the tip creates heat. The heat may burn the tissue of the cornea. Damage to the corneal tissue is irreversible and may result in a permanent impairment of the patient&#39;s vision. It is therefore important to avoid corneal burning during a phaco procedure. In some procedures that incision is larger than the instrument to allow fluid leakage that cools the tissue.  
           [0009]    U.S. Pat. No. 5,354,265 issued to Mackool discloses an ultrasonic handpiece which has a flexible outer sleeve and a hard inner sleeve. The hard inner sleeve may reduce the amount of contact between the outer sleeve and the vibrating tip. The reduction in contact decreases the heat and probability of corneal burning. U.S. Pat. No. 5,282,786 issued to Ureche and U.S. Pat. No. 5,807,310 issued to Hood disclose irrigation sleeves that have bands which are constructed from a material such as TEFLON. The TEFLON sleeves have a stiffness that is greater than the stiffness of the rubber material. The TEFLON outer band may reduce the friction and corresponding heat generated between the cornea and the irrigation sleeve.  
           [0010]    Having to provide a sleeve or band increases the complexity of the handpiece. Additionally, it has been found that even with a sleeve, relative movement between the tip and the cornea may stretch and tear corneal tissue at the incision. It would therefore be desirable to provide an apparatus and technique that can eliminate the disadvantages listed above without significantly increasing the cost or complexity of the instrument, or the procedure.  
         SUMMARY OF THE INVENTION  
         [0011]    The present application includes an instrument sheath that can be inserted into an incision formed in tissue. The sheath may protect the tissue from mechanical, thermal and other forms of trauma. The application also includes a blade guide that can be used to form an incision.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a cross-sectional view of an ultrasonic tip of the prior art;  
         [0013]    [0013]FIG. 2 is a perspective view of an embodiment of a sheath of the present invention;  
         [0014]    [0014]FIG. 3 is side sectional view showing the sheath inserted into an incision of a cornea and an instrument inserted through the sheath;  
         [0015]    [0015]FIG. 4 is a perspective view of an embodiment of a blade guide;  
         [0016]    [0016]FIG. 5 is a perspective view of a blade;  
         [0017]    [0017]FIG. 6 is a top view showing the blade being moved across the blade guide and into a cornea.  
     
    
     DETAILED DESCRIPTION  
       [0018]    Referring to the drawings more particularly by reference numbers, FIG. 2 shows an embodiment of a corneal sheath  10  of the present invention. The corneal sheath  10  may include a shank  12  which has an inner channel  14  that extends from a proximal end  16  to a distal end  18  of the sheath  10 . The proximal end  16  of the shank  12  may have a first annular rim  20 . The distal end  18  of the shank  12  may have a second annular rim  22 .  
         [0019]    The sheath  10  may include a distal seal  24  that is located at the distal end  18  of the sheath  10  and a proximal seal  25  located at the proximal end  16  of the sheath  10 . Each seal  24  and  25  may include a pair of lips  26  that can be deflected in an outward direction. The shank  12 , rims  20  and  22 , and seals  24  and  25  can all be constructed as an integrally molded piece. By way of example, the sheath  10  may be constructed from a silicon rubber or a molded plastic material.  
         [0020]    As shown in FIG. 3, the sheath  10  can be inserted into an incision in a cornea  28 . The sheath  10  can be pushed through the incision until the first annular rim  20  engages an outer surface  30  of the cornea  28 . The first rim  20  provides a stop function which limits the penetration of the sheath  10 . The second rim  22  may be flush with an inner surface  32  of the cornea  28 . The first  20  and second  22  rims may be pressed against the inner  32  and outer  30  corneal surfaces to provide a double seal which prevents intraocular fluid from escaping the anterior chamber of the cornea  22 . The second rim  22  may have a diameter that is smaller than the first rim  20  so that the sheath  10  can be removed from the incision of the cornea  28 .  
         [0021]    After the sheath  10  is inserted into the incision of the cornea  28  an instrument  34  can be inserted through the inner channel  14  of the sheath  10 . The instrument  32  may be the tip of an ultrasonic handpiece that is used to emulsify a lens. Insertion of the instrument  34  deflects the lips  26  and opens the seals  24  and  25 . The lips  26  may conform to the outer surface of the instrument to prevent fluid from leaking back through the sheath  10 . The sheath  10  may be flexible enough so that the lips  26  move back to the original position and close the seals  24  and  25  when the instrument  34  is pulled out of the cornea  28 .  
         [0022]    The sheath  10  provides a protective element which prevents heat from being transferred between the ultrasonic instrument  34  and the corneal tissue. The instrument  10  does not require an outer protective sleeve as typically found in the prior art. This reduces the complexity and cost of producing and using the ultrasonic handpiece. Additionally, the sheath  10  structurally reinforces the cornea so that movement of the instrument does not stretch and tear the corneal tissue. The sheath  10  also allows the incision to be placed more posteriorly without fluid causing ballooning of conjunctiva of Tenon&#39;s capsule. Furthermore, the incision does not have to allow leakage to cool the tissue during surgery. The smaller incision and lack of leakage maintains the depth of the anterior chamber.  
         [0023]    [0023]FIG. 4 shows an embodiment of a blade guide  50  that can be used to form an incision in a cornea. The blade guide  50  may include a groove  52  that extends across a width of a base plate  53 . The groove  52  may have a T-shaped cross-section which has a pair of opposing channels  54 .  
         [0024]    The groove  52  may receive a blade  56  shown in FIG. 5. The blade  56  may have a sharpened tip  58  and edges  60  that can cut tissue. The blade  56  may extend from a handle  62  that can be held by a surgeon. The blade width and thickness may be such that the blade  56  can slide along the groove  52  of the blade guide  50  while being captured by the channels  54 . The channels  54  allow lateral movement across the blade guide  50  without vertical movement out of the groove  52 .  
         [0025]    [0025]FIG. 6 shows the blade  56  moving across the blade guide  50  and into a cornea  28 . The blade guide  50  may have an edge surface  64  that conforms to the outer surface of the cornea  28 . The longitudinal axis  66  of the groove  52  may be at an oblique angle relative to the longitudinal axis  68  of the blade guide  50 . This configuration allows the groove  52  to guide the blade  56  into the cornea at an oblique angle. The angular (tangential) incision increases the surface area of the corneal tissue incision permitting better self sealing. The blade guide  50  also insures a consistent cutting angle for each incision in every surgical procedure.  
         [0026]    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. For example, although the blade guide  50  as described as being used in conjunction with the sheath  10 , it is to be understood that the blade guide  50  can be used independent of the sheath  10  and vice versa. For example, the blade guide  50  can be used to form a second tangential incision that would be self sealing, through which an irrigation maintaining device could be placed during surgery.