Abstract:
A phacoemulsification needle comprises a hollow shaft with an interior surface, an exterior surface, and a distal end terminating in a distal edge. The shaft has a central bore extending there through. The central bore is defined by the interior surface of the hollow shaft. A first over mold is located on the exterior surface and distal edge of the hollow shaft. The first over mold covers at least a portion of a periphery of the exterior surface of the hollow shaft, the distal edge, and terminates at the central bore.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to the field of phacoemulsification and more particularly to phacoemulsification cutting needles. 
         [0002]    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. 
         [0003]    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 function by an IOL. 
         [0004]    In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, a thin phacoemulsification cutting needle is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting needle liquefies 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. 
         [0005]    A typical ultrasonic surgical device suitable for ophthalmic procedures consists of an ultrasonically driven hand piece, an attached cutting needle, an irrigating sleeve, and an electronic control console. The hand piece assembly is attached to the control console by an electric cable and flexible tubing. Through the electric cable, the console varies the power level transmitted by the hand piece to the attached cutting needle and the flexible tubing supply irrigation fluid to and draw aspiration fluid from the eye through the hand piece assembly. 
         [0006]    The operative part of the hand piece 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 needle during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the hand piece by flexible mountings. The hand piece 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 needle. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting needle is adjusted so that the needle projects only a predetermined amount past the open end of the irrigating sleeve. 
         [0007]    In use, the ends of the cutting needle and irrigating sleeve are inserted into a small incision of predetermined width in the cornea or sclera. The cutting needle 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 needle communicates with the bore in the horn that in turn communicates with the aspiration line from the hand piece 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 needle, the cutting needle and horn bores and the aspiration line and into a collection device. The aspiration of emulsified tissue is aided by a saline solution or irrigating solution that is injected into the surgical site through the small annular gap between the inside surface of the irrigating sleeve and the cutting needle. 
         [0008]    In some cases, the cutting needle, which is typically made of titanium or stainless steel, may damage eye structures. The distal end of the cutting needle may also sometimes be sharper than is necessary to perform cataract removal. It would be desirable to have a cutting needle that overcomes these shortfalls. 
       SUMMARY OF THE INVENTION 
       [0009]    In one example of the present invention, a phacoemulsification needle comprises a hollow shaft with an interior surface, an exterior surface, and a distal end terminating in a distal edge, the shaft having a central bore extending there through, the central bore defined by the interior surface of the hollow shaft; and a first over mold located on the exterior surface and distal edge of the hollow shaft, the first over mold covering at least a portion of a periphery of the exterior surface of the hollow shaft, the first over mold covering the distal edge and terminating at the central bore. 
         [0010]    In other examples of the present invention, the phacoemulsification needle further comprises a through hole located in the hollow shaft and extending from the exterior surface to the interior surface of the hollow shaft wherein the first over mold substantially fills the through hole. The first over mold may have a rounded front edge located over the distal edge of the hollow shaft and a rounded trailing edge located on the exterior surface of the hollow shaft. The first over mold may extend circumferentially around the entire perimeter of the exterior surface of the hollow shaft. The first over mold may be made of a polymer. 
         [0011]    In other examples of the present invention, the phacoemulsification needle further comprises a second over mold located on the first over mold, the second over mold covering at least a portion of a periphery of an exterior surface of the first over mold, the second over mold covering the rounded front edge of the first over mold and terminating at the central bore. The second over mold may be embedded in the first over mold such that the exterior surface of the first over mold is continuous with an exterior surface of the second over mold. The second over mold may extend circumferentially around the entire perimeter of the exterior surface of the hollow shaft. The second over mold may be made of silicone. 
         [0012]    In another example of the present invention, a method comprises providing a phacoemulsification needle as described in the preceding three paragraphs and causing that needle to be vibrated in the eye, for example, to perform cataract surgery. 
         [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The following description, as well as the practice of the invention, set forth and suggest additional advantages and purposes of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. 
           [0015]      FIG. 1  is a diagram of a phacoemulsification hand piece system. 
           [0016]      FIG. 2  is a side view of a phacoemulsification needle with a polymer distal end according to an embodiment of the present invention. 
           [0017]      FIG. 3  is a perspective view of the distal end of a phacoemulsification needle according to an embodiment of the present invention. 
           [0018]      FIG. 4  is a side cross section view of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. 
           [0019]      FIG. 5  is a side cross section view of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. 
           [0020]      FIG. 6  is a side cross section view of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. 
           [0021]      FIG. 7  is a side cross section view of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Reference is now made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. 
         [0023]      FIG. 1  depicts an ultrasonic hand piece system. In  FIG. 1 , hand piece  100  is coupled to console  140 . Console  140  is coupled to foot switch  150 . Hand piece  100  has a cutting needle  110 , a horn  120 , and a set of piezoelectric crystals  130 . A needle interface  115  connects cutting needle  110  to a reduced diameter portion  125  of horn  120 . 
         [0024]    Needle  110  is typically a thin needle made of titanium or stainless steel that is designed to emulsify a lens when vibrated ultrasonically. Needle  110  is typically cylindrical in shape, has a small diameter of about 20-30 gauge, and has a length suitable for removal of a lens when inserted into the anterior chamber of the eye. 
         [0025]    Horn  120  is typically made of a rigid material suitable for medical use (such as a titanium alloy). Horn  120  has a reduced diameter section  125  that is connected to a needle interface  115 . Needle interface  115  typically has a threaded connection that accepts needle  110 . In this manner needle  110  is screwed onto horn  120  at needle interface  115 . This provides a rigid connection between needle  110  and horn  120  so that vibration can be transmitted from horn  120  to needle  110 . 
         [0026]    Piezoelectric crystals  130  supply ultrasonic vibrations that drive both the horn  120  and the attached cutting needle  110  during phacoemulsification. Piezoelectric crystals  130  are affixed to horn  120 . Crystals  130  are typically ring shaped, resembling a hollow cylinder and constructed from a plurality of crystal segments. When excited by a signal from console  140 , crystals  130  resonate, producing vibration in horn  120 . 
         [0027]    Console  140  includes a signal generator that produces a signal to drive piezoelectric crystals  130 . Console  140  has a suitable microprocessor, micro-controller, computer, or digital logic controller to control the signal generator. In operation, console  140  produces a signal that drives piezoelectric crystals  130 . Piezoelectric crystals  130 , when excited, cause horn  120  to vibrate. Needle  110 , connected to horn  120 , also vibrates. When needle  110  is inserted into the anterior chamber of the eye and vibrated, it acts to emulsify a cataractous lens. 
         [0028]    In cataract surgery, the needle  110  is typically made only of titanium or stainless steel. Because the needle  110  is vibrated in the eye ultrasonically (typically at frequencies greater than 30 kHz), it is important to have a needle  110  that can withstand such vibrations. It had been thought that polymer needles or needles with a polymer over mold would not withstand such vibrating force. The inventors of the present application have discovered that the phacoemulsification needles described and claimed herein withstand such vibrations and function to remove natural lenses during cataract surgery. 
         [0029]      FIG. 2  is a side view of a phacoemulsification needle  200  with a polymer distal end according to an embodiment of the present invention. Needle  200  has a shaft  210  terminating at a distal end  220 . Opposite the polymer distal end  220  is a hub  230  and threaded connection  240 . Shaft  210  is typically cylindrical with a central bore that forms a part of the aspiration path. Fragmented lens particles and irrigating solution are aspirated through the central bore of shaft  210 . Hub  230  and threaded connection  240  allow the needle  200  to be coupled to a hand piece. Shaft  210 , hub  230 , and threaded connection  240  are typically made from titanium, stainless steel or other similar material. As described in greater detail below, distal end  220  may be made of a polymer, plastic, silicone or other similar material. Such materials are generally softer, smoother, and have more rounded edges than the titanium or stainless steel of traditional phacoemulsification needles. As noted, the distal end  220  of phacoemulsification needle  200  is inserted into the eye to remove a cataract. The distal end  220  of phacoemulsification needle  200  also comes into contact with other delicate eye structures. A distal end made of a polymer, plastic, silicone or other similar material tends to damage these delicate eye structures less than a phacoemulsification needle with a distal end made of titanium or stainless steel. 
         [0030]      FIG. 3  is a perspective view of the distal end of a phacoemulsification needle according to an embodiment of the present invention.  FIG. 3  depicts the distal end  300  of a phacoemulsification needle with a central bore  320  and a through hole  310  in a side wall of distal end  300 . Distal end  300  is typically made of titanium, stainless steel, or other similar material. The through hole  310  allows an over mold to be secured to distal end  300 . In some cases, a polymer may be over molded onto distal end  300 . Through hole  310  is filled with the polymer and acts to secure it to distal end  300 . While through hole  310  is shown as a continuous oval opening in a side wall of distal end  310 , through hole may be of any suitable shape. In addition, through hole  310  may have a discontinuous periphery (e.g., serrated) that serves to grip a polymer over mold. 
         [0031]      FIG. 4  is a side cross section view of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. Over mold  430  (shown as the shaded portion of  FIG. 4 ) is located on shaft  420 . Shaft  420  has a continuous central bore that extends to an open end at the distal end of over mold  430 . The distal end of over mold  430  has a rounded front edge ( 440 ,  445 ) that extends circumferentially around the perimeter of shaft  420 . When shaft  420  is a hollow cylinder, over mold  430  is located around the periphery of the cylinder and covers the edges of the distal end of the cylinder. Typically, a phacoemulsification needle is essentially a metal tube with a wall thickness. The central bore of the metal tube extends completely and continuously through it. The distal end of such a phacoemulsification needle often has sharp edges (or edges that are not rounded). The depth of these edges is defined by the wall thickness of the needle. Over mold  430  would be located on such a phacoemulsification needle around its periphery. Over mold  430  would extend to cover the edges on the distal end of the needle. In this manner, over mold  430  provides a soft, rounded, pliable, and/or smooth surface that covers the sharp edges of the needle and extends back from the distal end of the needle along the needle shaft  420 . 
         [0032]    Over mold  430  has a rounded or smooth front edge (shown in the cross section drawing as  440  &amp;  445 ) and a rounded or smooth trailing edge (shown in the cross section drawing as  460  and  465 ). These front ( 440 ,  445 ) and trailing ( 460 ,  465 ) edges allow for the phacoemulsification needle to be easily inserted into and removed from a small incision in the eye. Because these front ( 440 ,  445 ) and trailing ( 460 ,  465 ) edges are smooth, soft, rounded and/or pliable, over mold  430  better protects delicate eye structures during cataract surgery. In particular, the front edge ( 440 ,  445 ) or over mold  430  is much less likely to damage eye structures than a traditional phacoemulsification needle. 
         [0033]    Over mold  430  may be made of a polymer, plastic, silicone or the like. Generally, over mold  430  is molded onto shaft  420  by, for example, an injection molding process. As shown in  FIG. 4 , two through holes  450  and  455  secure over mold  430  to shaft  420 . In other examples of the invention, other structures on shaft  420  (such as protrusions, indentations, or the like) are used to secure over mold  430  to shaft  420 . In other examples, no through holes  450 ,  455  are present, and over mold  430  is secured onto shaft  420  by friction or an adhesive. In one example, over mold  430  is premolded and fixed to shaft  420  by friction or an adhesive. When over mold  430  is injection molded onto shaft  420 , a dowel or other similar structure may be placed in central bore  410  to prevent material from entering the central bore  410  through the through holes  450 ,  455 . 
         [0034]      FIG. 5  is a side cross section view another example of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. In  FIG. 5 , the needled is beveled. Over mold  530  (shown as the shaded portion of  FIG. 5 ) is located on shaft  520 . Shaft  520  has a continuous central bore that extends to an open end at the distal end of over mold  530 . The distal end of over mold  530  has a rounded front edge ( 540 ,  545 ) that extends circumferentially around the perimeter of shaft  520 . When shaft  520  is a hollow cylinder, over mold  530  is located around the periphery of the cylinder and covers the edges of the distal end of the cylinder. Typically, a phacoemulsification needle is essentially a metal tube with a wall thickness. The central bore of the metal tube extends completely and continuously through it. The distal end of such a phacoemulsification needle often has sharp edges (or edges that are not rounded) especially when the end of the needle is beveled. The depth of these edges is defined by the wall thickness of the needle. Over mold  530  would be located on such a phacoemulsification needle around its periphery. Over mold  530  would extend to cover the edges on the distal end of the needle. In this manner, over mold  530  provides a soft, rounded, pliable, and/or smooth surface that covers the sharp edges of the needle and extends back from the distal end of the needle along the needle shaft  520 . 
         [0035]    Over mold  530  has a rounded or smooth front edge (shown in the cross section drawing as  540  &amp;  545 ) and a rounded or smooth trailing edge (shown in the cross section drawing as  560  and  565 ). These front ( 540 ,  545 ) and trailing ( 560 ,  565 ) edges allow for the phacoemulsification needle to be easily inserted into and removed from a small incision in the eye. Because these front ( 540 ,  545 ) and trailing ( 560 ,  565 ) edges are smooth, soft, rounded and/or pliable, over mold  530  better protects delicate eye structures during cataract surgery. In particular, the front edge ( 540 ,  545 ) or over mold  530  is much less likely to damage eye structures than a traditional phacoemulsification needle. 
         [0036]    Over mold  530  may be made of a polymer, plastic, silicone or the like. Generally, over mold  530  is molded onto shaft  520  by, for example, an injection molding process. As shown in  FIG. 5 , two through holes  550  and  555  secure over mold  530  to shaft  520 . In other examples of the invention, other structures on shaft  520  (such as protrusions, indentations, or the like) are used to secure over mold  530  to shaft  520 . In other examples, no through holes  550 ,  555  are present, and over mold  530  is secured onto shaft  520  by friction or an adhesive. In one example, over mold  530  is premolded and fixed to shaft  520  by friction or an adhesive. When over mold  530  is injection molded onto shaft  520 , a dowel or other similar structure may be placed in central bore  510  to prevent material from entering the central bore  510  through the through holes  550 ,  555 . 
         [0037]      FIGS. 6 and 7  are side cross section views of the distal end of a phacoemulsification needle with an over molded distal end according to an embodiment of the present invention. In  FIGS. 6 and 7 , a first over mold  630  and a second over mold ( 570 ,  575 ) are present on the distal end of shaft  620 . First over mold  630  (shown as the shaded portion of  FIG. 6 ) is located on shaft  620 . Shaft  620  has a continuous central bore that extends to an open end at the distal end of first over mold  630 . The distal end of first over mold  630  has a rounded front edge ( 640 ,  645 ) that extends circumferentially around the perimeter of shaft  620 . When shaft  620  is a hollow cylinder, first over mold  630  is located around the periphery of the cylinder and covers the edges of the distal end of the cylinder. Typically, a phacoemulsification needle is essentially a metal tube with a wall thickness. The central bore of the metal tube extends completely and continuously through it. The distal end of such a phacoemulsification needle often has sharp edges (or edges that are not rounded) especially when the end of the needle is beveled. The depth of these edges is defined by the wall thickness of the needle. First over mold  630  would be located on such a phacoemulsification needle around its periphery. First over mold  630  would extend to cover the edges on the distal end of the needle. In this manner, first over mold  630  provides a soft, rounded, pliable, and/or smooth surface that covers the sharp edges of the needle and extends back from the distal end of the needle along the needle shaft  620 . 
         [0038]    A second over mold  670 ,  675  is located on first over mold  630 . Second over mold  670 ,  675  may cover all or a portion of first over mold  630 . In one example, second over mold  670 ,  675  is silicone which provides a smooth and pliable surface that does not cause unwanted damage to eye structures. In this case, the second over mold  670 ,  675  may be applied to first over mold  630  in a two shot molding process, by an adhesive, or by other similar means. In the example shown in  FIGS. 6 and 7 , second over mold  670 ,  675  extends along shaft  620  and covers the distal edge of first over mold  630 . In such a case, the sharp edges of the distal end of shaft  620  are covered by the material of first over mold  630  and the material of second over mold  670 ,  675 . In the example of  FIG. 6 , the second over mold  670 ,  675  is applied on top of first over mold  630 . In the example of  FIG. 7 , second over mold  670 ,  675  is embedded in first over mold  630  such that the outer surface of first over mold  630  and second over mold  670 ,  675  form a smooth, continuous surface. 
         [0039]    First over mold  630  and second over mold  670 ,  675  have rounded or smooth front edges  640 ,  645 . First over mold has a rounded or smooth trailing edge (shown in the cross section drawing as  660  and  665 ). These front ( 640 ,  645 ) and trailing ( 660 ,  665 ) edges allow for the phacoemulsification needle to be easily inserted into and removed from a small incision in the eye. Because these front ( 640 ,  645 ) and trailing ( 660 ,  665 ) edges are smooth, soft, rounded and/or pliable, first over mold  630  and second over mold  670 ,  675  better protect delicate eye structures during cataract surgery. In particular, the front edge ( 640 ,  645 ) or first over mold  630  and second over mold  640 ,  645  are much less likely to damage eye structures than a traditional phacoemulsification needle. 
         [0040]    First over mold  630  may be made of a polymer, plastic, silicone or the like. Generally, first over mold  630  is molded onto shaft  620  by, for example, an injection molding process. As shown in  FIG. 6 , two through holes  650  and  655  secure first over mold  630  to shaft  620 . In other examples of the invention, other structures on shaft  620  (such as protrusions, indentations, or the like) are used to secure first over mold  630  to shaft  620 . In other examples, no through holes  650 ,  655  are present, and first over mold  630  is secured onto shaft  620  by friction or an adhesive. In one example, first over mold  630  is premolded and fixed to shaft  620  by friction or an adhesive. When first over mold  630  is injection molded onto shaft  620 , a dowel or other similar structure may be placed in central bore  610  to prevent material from entering the central bore  610  through the through holes  650 ,  655 . 
         [0041]    In operation, any of the needles  430 ,  530 , or  630  can be secured to a phacoemulsification hand piece via a threaded connection  240 . The needle  430 ,  530 , or  630  is then inserted into the anterior chamber of the eye through a small incision and vibrated ultrasonically. Lens material and fluid are aspirated through the central bore  410 ,  510 , or  610  of the respective needle  430 ,  530 , or  630 . Over mold  430 ,  530 , or  630  is secured to the needle such that the ultrasonic vibrations do not cause it to move. In other words, the over mold is subjected to the stresses of vibration and surgery without being dislocated from the needle. In addition, the front edge of the over mold protects delicate eye structures from the unintended stresses of surgery. For example, the over mold is rigid enough to fracture a natural lens but smooth enough not to damage the posterior lens capsule. When a second over mold is present, the first and second over molds operate cooperatively. 
         [0042]    From the above, it may be appreciated that the present invention provides an improved phacoemulsification needle for cataract surgery. The present invention provides a phacoemulsification needle with a polymer distal end. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
         [0043]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.