Abstract:
A cannula having a body, a sealing disc, and a cap. The sealing disc is located within the body and is compressed by the cap. An angled cut in the sealing disc allows microsurgical instruments to be inserted through the cannula into the eye. Upon removal, the cut in the sealing disc closes, preventing the loss of intraocular pressure.

Description:
[0001]    This invention relates to ophthalmic surgical equipment and more particularly to posterior segment ophthalmic surgical equipment. 
       BACKGROUND OF THE INVENTION 
       [0002]    Microsurgical instruments typically are used by surgeons for removal of tissue from delicate and restricted spaces in the human body, particularly in surgery on the eye, and more particularly in procedures for removal of the vitreous body, blood, scar tissue, or the crystalline lens. Such instruments include a control console and a surgical handpiece with which the surgeon dissects and removes the tissue. With respect to posterior segment surgery, the handpiece may be a vitreous cutter probe, a laser probe, or an ultrasonic fragmenter for cutting or fragmenting the tissue and is connected to the control console by a long air-pressure (pneumatic) line and/or power cable, optical cable, or flexible tubes for supplying an infusion fluid to the surgical site and for withdrawing or aspirating fluid and cut/fragmented tissue from the site. The cutting, infusion, and aspiration functions of the handpiece are controlled by the remote control console that not only provides power for the surgical handpiece(s) (e.g., a reciprocating or rotating cutting blade or an ultrasonically vibrated needle), but also controls the flow of infusion fluid and provides a source of vacuum (relative to atmosphere) for the aspiration of fluid and cut/fragmented tissue. The functions of the console are controlled manually by the surgeon, usually by means of a foot-operated switch or proportional control. 
         [0003]    During posterior segment surgery, the surgeon typically uses several handpieces or instruments during the procedure. This procedure requires that these instruments be inserted into, and removed out of the incision. This repeated removal and insertion can cause trauma to the eye at the incision site. To address this concern, hubbed cannulae were developed at least by the mid-1980s. These devices consist of a narrow tube with an attached hub. The tube is inserted into an incision in the eye up to the hub, which acts as a stop, preventing the tube from entering the eye completely. Often the hub is stitched to the eye to prevent inadvertent removal. Surgical instruments can be inserted into the eye through the tube, and the tube protects the incision sidewall from repeated contact by the instruments. In addition, the surgeon can use the instrument, by manipulating the instrument when the instrument is inserted into the eye through the tube, to help position the eye during surgery. Disadvantages of prior art cannulae include the height of the projection on the surface of the eye, as well as the lack of any means to control loss of intraocular pressure during instrument exchange or removal. The eye, being a pressurized globe, will expel aqueous or vitreous out of the open cannula when a surgical device is not present. With prior art cannulae, loss of intraocular pressure was prevented by the insertion of a plug or cap into the tube to seal the cannula and prevent the expression of fluid and tissue. This is a time-consuming process that often requires additional instrumentation as well as the assistance of other OR personnel and increases the risk of post-operative infection. 
         [0004]    Accordingly, a need continues to exist for a cannula that self seals upon instrument removal, thus eliminating the need for plugs, caps, and the instrumentation required to install and remove these devices. Such a device would reduce the amount of time required for surgical procedures and reduce dependency on other OR personnel. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention improves upon prior art by providing a cannula that self seals upon instrument removal. The cannula generally consists of a tube and an attached hub. Disposed within the hub is a sealing disc having a cut or slit that allows access to the incision, and closes upon instrument removal to seal the cannula. 
         [0006]    Accordingly, an objective of the present invention is to provide a cannula. 
         [0007]    Another objective of the present invention is to provide a cannula having a sealing disc that self seals upon instrument exchange or removal. 
         [0008]    A further objective of the present invention is to provide a cannula that eliminates the need for plugs, caps, and other sealing instrumentation. 
         [0009]    A further objective of the present invention is to provide a cannula having a low profile projection on the surface of the eye. 
         [0010]    Other objectives, features and advantages of the present invention will become apparent with reference to the drawings, and the following description of the drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an exploded top perspective view of a first embodiment of the cannula of the present invention. 
           [0012]      FIG. 2  is a top perspective view of a first embodiment of the cannula of the present invention. 
           [0013]      FIG. 3  is an enlarged cross sectional view of a first embodiment of the cannula of the present invention. 
           [0014]      FIG. 4  is an exploded cross sectional view of a first embodiment of the cannula of the present invention. 
           [0015]      FIG. 5  is an enlarged cross sectional view of a first embodiment of the cannula of the present invention similar to  FIG. 4 , but with a surgical instrument inserted into the cannula. 
           [0016]      FIG. 6  is an enlarged cross sectional view of a second embodiment of the cannula of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    As best seen in  FIGS. 1 through 4 , cannula  10  generally consists of body  12 , sealing disc  14 , and cap  16 . Body  12  and cap  16  may be made from any suitable material, such as stainless steel, titanium, or thermoplastic. Body  12  is comprised of tube  18  and hub  20  which may be formed integrally or in separate pieces. Tube  18  is of sufficient length to extend through sclera  130  and enter posterior chamber  140 . Hub  20  is generally cylindrical with internal cavity  24  having distal floor  22  sloped or tapered at an angle of between about 18-24 degrees (most preferably about 22 degrees) so as to have a funnel shape directed toward bore  19  in tube  18 . Cavity  24  may have a diameter of between about 0.040-0.050 inches (most preferably about 0.046 inches) or any other suitable diameter. Cavity  24  generally extends from proximal face  28  to distal floor  22  a depth of between about 0.025-0.035 inches (most preferably about 0.029 inches). Proximal face  28  of hub  20  is generally flat with circumferential rabbet  32  recessed into face  28  to a depth of between about 0.005-0.015 inches (most preferably about 0.008 inches). Rabbet  32  may have a diameter of between about 0.060-0.070 inches (most preferably about 0.062 inches). As best seen in  FIG. 4 , cap  16 , contains sealing surface  42  defined by tubular sidewall  44 . Sidewall  44  also defines hollow bore  45  that is sized and shaped to be received over hub  20  so that sealing surface  42  contacts proximal face  28 . Sealing surface  42  has a depth of between about 0.016-0.020 inches (most preferably about 0.018 inches). Cap  16  contains opening  49  opposite bore  45  that communicates with bore  45 . Opening  49  is defined by proximal surface  17  that is roughly funnel shaped and sloped toward opening  49  and cavity  24 . 
         [0018]    Sealing disc  14  is roughly circular, contains cut  40 , and is sized and shaped to fit within rabbet  32  of hub  20 . Sealing disc  14  preferably has a thickness of between about 0.005-0.015 inches (most preferably about 0.010 inches). Sealing disc  14  may be made from any appropriate material, such as rubber or any suitable elastomer, but is most preferably made from a silicone rubber, such as Silastice silicone rubber sold by Dow Corning Corporation, Midland, Mich. Cut  40  is located in the approximate center of sealing disc  14  entirely or partially across sealing disc  14  and extends entirely through the thickness of sealing disc  14 . Cut  40  preferably is made at an angle of between about 40-50 degrees (most preferably 45 degrees) but any suitable angle may be used. Sealing disc  14  is seated within rabbet  32  of hub  20 . Cavity  45  of cap  16  fits over hub  20  and slightly compresses sealing disc  14  such as between approximately 0.001-0.003 inches (most preferably about 0.002 inches). Cap  16  may be held in place by any appropriate mechanism, such as crimping or adhesive, but is most preferably held in place by interference or frictional fit between tubular sidewall  44  of cap  16  and hub  20 . 
         [0019]    During operation, as best shown in  FIG. 5 , tube  18  is inserted through sclera  130 . Microsurgical instrument  50  is inserted through opening  49 , cut  40 , cavity  24 , tube  18 , and into posterior chamber  140 . The funnel shape of surface  17  of cap  16 , and distal floor  22  of cavity  24 , helps direct surgical instrument  50  into bore  19 . Cavity  24  allows room for sealing disc  14  to deform inwardly without impeding the motion of, or increasing the friction on, surgical instrument  50 . When the surgeon wishes to withdraw or exchange instruments, surgical instrument  50  is withdrawn from cannula  10 . Cut  40  returns to its original closed position, thereby sealing tube  18 , as seen in  FIG. 3 . The angle of cut  40  helps to seal sealing disc  14  and prevent loss of fluid and tissue. 
         [0020]    In a second embodiment, shown in  FIG. 6 , hub  20 ′ is of construction similar to hub  20  and is generally cylindrical and contains rabbet  32 ′, which is deeper than rabbet  32  and of sufficient depth to receive both sealing disc  14  and cap  16 ′. Edge  62  extends proximally from hub  20 ′ and may comprise a continuous flange around the circumference of hub  20 ′, or may comprise a plurality of flanges disposed at regular or irregular intervals around the circumference of hub  20 ′. Edge  62  may be of any appropriate geometry, but is most preferably an angled or curved cut made in the proximal portion of sidewall  65  of hub  20 ′. Cap  16 ′ is generally cylindrical, and has groove  60  in the circumference of outer wall  64 . Cap  16 ′ is received within rabbet  32 ′ of hub  20 ′, proximal sealing disc  14 , thereby holding sealing disc  14  in place. Cap  16 ′ slightly compresses sealing disc  14 , and cap  16 ′ is held in place by folding, crimping, or bending edge  62  into groove  60 . 
         [0021]    While certain embodiments of the present invention have been described above, these descriptions are given for purposes of illustration and explanation. Variations, changes, modifications and departures from the systems and methods disclosed above may be adopted without departure from the scope or spirit of the present invention.