Patent Publication Number: US-2005125001-A1

Title: Corneal transplant trimming and suturing device

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to surgical devices. More particularly, the present invention is in the field of corneal transplantation.  
     BACKGROUND OF THE INVENTION  
      Corneal transplantation is performed using corneal tissue extracted from a donor eye, and inserted into a recipient eye after the faulty tissue has been removed from the recipient&#39;s eye. In such operations, care has to be taken to fit the graft in place without distorting the graft tissue for several reasons. The first reason is to allow for complete contact of the graft with the supporting tissue of the recipient&#39;s eye surrounding the graft. This is better explained in reference to  FIG. 1A-1D . A donor eye is shown in  FIG. 1A , generally designated as  10 . The cut made around the cornea is designated  12 . A dashed circle  14  designates the cornea and is remained untouched by the contours of the cut  12 . In  FIG. 1B  the transplant is shown dislodged from the donor&#39;s eye. The outline of the cornea  14  is shown for the sake of clarity by a dashed circle. By a next operative act, as shown in  FIG. 1C , a circular tissue  16  from within the limits of the cornea, is extracted by a circular blade, the diameter of which matches the dimensions of an incision made in the recipient&#39;s eye. In  FIG. 1D  a recipient&#39;s eye  18  is shown, illustrating a circle  20 , which marks the circumference of the circular piece of corneal tissue taken out and replaced by the graft  16 , the diameter of which is typically slightly larger than the circular incision in the recipient&#39;s eye.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a schematic description of a prior art incision made in a donor&#39;s eye, with the actual cut designated, marking the circumference of the transplant intended for extraction.  
       FIG. 1B  is a schematic description of a dislodged donor transplant as in the prior art;  
       FIG. 1C  is a schematic description of a dislodged donor transplant after having been trimmed as in the prior art;  
       FIG. 1D  is a schematic description of a donor eye with a hole cut in its own cornea as a preparation for a grafting operation as in the prior art;  
       FIG. 2A  is schematic description of a cylinder with radial grooves on its upper face used for trimming a transplant in accordance with the present invention;  
       FIG. 2B  is schematic description of a cylinder composed of segments, with radial grooves on its upper face used for trimming a transplant in accordance with the present invention;  
       FIG. 3A  is a schematic description of a cylinder of the invention on which raw transplant tissue is laid;  
       FIG. 3B  is a schematic description of a cylinder of the invention on which raw transplant tissue is laid and on top of which a circular knife is inserted;  
       FIG. 3C  is a schematic description of a cylinder of the invention on which raw transplant tissue has been trimmed by a circular knife;  
     
       4 
     
       FIG. 4A  is a schematic description of a cylinder of the invention, with a surgical needle being directed at a groove;  
       FIG. 4B  is a schematic description of a cylinder of the invention, with a surgical needle being inserted into a groove;  
       FIG. 5A  is a schematic description of a longitudinal section in a cylinder of the device of the invention containing two opposing surgical needles and a fresh transplant tissue inserted on the cylinder;  
       FIG. 5B  is a schematic description of a longitudinal section in a cylinder of the device of the invention showing two opposing surgical needles and a circular knife pressing against the transplant tissue before cutting commences.  
       FIG. 5C  is a schematic description of a longitudinal section in a cylinder of the device of the invention showing two opposing needles set against the transplant within the circular knife;  
       FIG. 5D  is a schematic description of a longitudinal section in a cylinder of the device of the invention showing two opposing surgical needles piercing the transplant tissue;  
       FIG. 6A  is a schematic description a surgical needle being inserted in the push spring notch;  
       FIG. 6B  is a schematic description of a push-spring and associated needle with suture;  
       FIG. 7A  is a schematic cross sectional view in a cylinder of the invention showing needles subtended by push-springs and trimmed transplant on top;  
       FIG. 7B  is a schematic cross sectional view in a cylinder of the invention showing transplant tissue pierced by needles subtended by push-springs;  
       FIG. 8A  is a general schematic view of a piercing device of the invention with push-springs biased away from the cylinder;  
       FIG. 8B  is a general schematic view of a piercing device of the invention with push-springs closed in on the cylinder;  
       FIG. 9  is a schematic cross sectional view in a cylinder of an embodiment of the invention in which the needles are dislocated by push rods actuated from within the cylinder;  
       FIG. 10  is a schematic overview of the cylinder of the invention, with pierced transplant and sutures attached to a retention ring;  
       FIG. 11  is a schematic overview of the detached transplant with sutures attached to a retention ring;  
       FIG. 12  is a schematic overview of a cylinder of the invention fitted with a needle retaining ring;  
       FIG. 13  is a schematic illustration of a sealed circular knife in accordance with an embodiment of the invention.  
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
      In accordance with the present invention, a corneal transplant is extracted from a donor.  
      The corneal transplant is set on an upper face of a cutting and piercing device of the invention, to be further trimmed by a circular blade to fit a substantially circular area matching the circular piece removed from the recipient&#39;s eye as in the prior art methods. A cutting and piercing device of the invention includes an upright cylinder, the upper part of which containing radial grooves. This can be seen in  FIG. 2A  to which reference is now made, an isometric view of the cylinder  24  is shown, in which radial grooves  28  are located on the upper face  26  of cylinder  24 . Grooves  28  are radially symmetrical, such that each groove has an opposite radial counterpart. In a preferred embodiment of the invention there are  8  grooves. In some embodiments of the invention the cylinder is assembled radially from segments, as can be seen in  FIG. 2B  to which reference is now made. Thus, cylinder  30  is comprised of segments, the upper face of which jointly forms a cylinder upper face  32 , with radial grooves  34  disposed between each segment.  
      In  FIGS. 3A-3C  to which reference is now made, the trimming aspect of the invention is described schematically. In  FIG. 3A  the upper face of the cylinder of the invention is shown covered almost completely by a freshly cut corneal tissue  40 . Some of the upper cylinder faces  26  of the cylinder of the invention remains exposed, not covered by the corneal transplant  40 . A circular knife is then slid down guided by guiding bars (not shown). In  FIG. 3B  the circular knife  42  sliding down towards the upper cylinder face is shown just as it meets the transplant  40  on its way down. As the knife is driven down further, it cuts the transplant&#39;s tissue, and the parts external to the circular knife are subsequently discarded. The results of this circular trimming are illustrated in  FIG. 3C , in which the cut tissue is discarded, and the circular knife  42  contains a circular tissue of the transplant internally. At this stage, the circular knife  42  holds the trimmed transplant tightly. The cutting action may not however prove complete at this stage because the circular knife&#39;s drive through the tissue to the bottom is not complete. The circular knife&#39;s blade abuts the cylinder&#39;s upper face at all the circular knife&#39;s circumference except for the grooves. Therefore, it is likely that above the grooves, the transplant&#39;s tissue would not be cut completely. In order to solve this problem, after the circular knife  42  has reached the lowest level, i.e. abutting the cylinder, it is turned slightly to the left or to the right, lifted up and again driven down, thereby exerting a final cutting action on the yet uncut tissue. This final cutting action is made possible because of the tight association that the transplant tissue has with the circular knife. Thus, after the first cutting action, when the circular knife is lifted up and turned sideways, the issue moves with it and the uncut strands which were once in line with the groves are now moved to face the hard surface of the upper face.  
      The Cutting and Piercing Action  
      After the corneal transplant is laid on the upper surface of the cylinder, the grooves are located beneath the transplant. However, before the transplant is placed on the upper surface, a surgical needle is inserted inside each groove, respectively. This preparatory action is typically performed in the factory, so that the operating team receives the device of the invention with needles already inserted in the grooves. FIGS.  4 A-B to which reference is now made, describe schematically how the surgical needle is inserted in grooves  28  in cylinder  24 , in accordance with the device of the present invention. Groove  28  is essentially wide enough and deep enough to accommodate for surgical needle  36 . As can be seen in  FIG. 4B , the needle is inserted in one of the grooves  28  of cylinder  24  with its pointed side towards the groove, such that the curve of the needle points upwards.  
      Schematically Illustrated in  FIG. 5A  to which reference is now made is a cross sectional view in a cutting and piercing device of the invention. In this embodiment of the invention, a transplant, typically freshly cut, is laid on top of the upper cylinder face  26 . Transplant  40  is a concave piece of tissue, wherein the convex side is the external side of the eye of the donor. The concave side of the transplant is a very vulnerable part of the cornea and must not be touched. The convex side of the transplant lying on the upper cylinder face corresponds to the outer part of the eye and is not as vulnerable as the other side. Circular knife  46 , the elevation of which is shown, begins its cutting action after the transplant has been laid on the upper cylinder face  26 , as it moves in the direction of arrow  48 . Surgical needles  36  are held in place with their associated stitches  50 . In the next stage, which is schematically illustrated in  FIG. 5B  to which reference is now made, circular knife  46  is pushed in the direction of arrow  48  until it starts cutting the transplant. In  FIG. 5C  the circular knife is shown pushed to a maximum, such that its blade  52  abuts the upper cylinder face  26 . Thereafter, the transplant tissue is trimmed and the cut tissue is discarded as shown in the figure. The Transplant is now held snugly in the circular knife, it can be turned around, raised and pushed again against the upper cylinder face  26 , to complete the cutting operation, as explained above. The tips of the surgical needles  36  are shown at a very short distance from the transplant tissue  40 . Finally, as described schematically in  FIG. 5D  the surgical needles  36  and  38  are rotated in the direction of arrows  42  and  44  respectively, such that their tips penetrate the transplant tissue  40 . In a preferred embodiment of the invention, the transplant tissue is pierced by the surgical needles, each at its own position in a respective groove. Piercing of the transplant tissue takes place by the forcing action of push-springs. These push-springs are elongated resilient straps having a notch at their upper end for inserting a needle and the attached stitch. The association of a push spring and a surgical needle is better explained with reference to  FIGS. 6A-6B . In  FIG. 6A , push spring  72  is shown with the needle  74  pointing away from the push spring, and the associated stitch  76  threaded through the notch  78 . An isometric side view in  FIG. 6B  shows the push spring  72  supporting the surgical needle  74  pointing upwards, and the associated stitch  76 .  
      The mechanism which accomplishes the piercing in accordance with the present invention is explained with reference to  FIGS. 7A-7B . A cross sectional view of a device of the invention is shown in  FIG. 7A , in which a push spring  84  is attached to surgical needles  86  and  87 . On the upper face  88  of cylinder  90 , circular knife  92  is disposed, containing the trimmed transplant  94 . A spring contracting ring (SCR)  96  is disposed at the bottom of push-springs  84  and  98 . In  FIG. 7B  the SCR  96  is shown pushed up in the direction of arrow  100 , simultaneously, the push-springs  84  and  98  contract inwards towards the cylinder  90 , in the direction of arrows  102  and  104 , respectively. This contraction pushes the needles inwards, and in the direction dictated by groove profile  106 , a rotational movement is induced which causes the piercing of trimmed transplant  94  by needles  86  and  87  respectively. In  FIGS. 8A and 8B  to which reference is now made, the movement of the push-springs in association with the movement of the SCR is described. In  FIG. 8A  is a schematic isometric view of a cylinder of the invention with the push-springs biased away from the cylinder. SCR  108  is shown disposed below the push-springs, and each of the push-springs, such as push spring  108  biased away from the cylinder  112 . In  FIG. 8B  the push-springs are shown contracted, as compelled by the SCR  108  which has moved upwards, abutting cylinder  112 .  
      In another embodiment of the present invention, the surgical needles are forced into the transplant tissue each by a push-rod. Accordingly, push-rods  114 ,  116  are dislocated by a cone  118  as shown in  FIG. 9 , to which reference is now made. In this embodiment of the invention, the needles are pushed by the push-rods from within the cylinder.  
      Supporting and Guiding Structures  
      Once the transplant has been pierced using a device in accordance with the present invention, the transplant can be handed to the surgeon for suturing to the recipient&#39;s eye. In accordance with an embodiment of the invention, the transplant is handled with the sutures held by a suture retaining ring (SRR) that keeps the sutures tidy and handy. This is described in  FIG. 10  to which reference is now made. SRR  120  retains the sutures, such as suture  122 , for example by attaching to a sticky material applied to the SRR or by pressing into grooves carved radially in the ring (not shown). The surgical needles  124  are attached to the transplant  126  underneath. When handled by the medical team, the transplant can be carried about by holding to the SRR. However, since the transplant is held snugly by the circular knife after it has been trimmed, in order to release the transplant from the circular knife, gas pressure is applied to the upper orifice of the circular knife. The internal pressure produced inside the void volume delimited by the circular knife and the transplant increases. Eventually, the transplant is ejected from the circular knife, as illustrated in  FIG. 11  to which reference is now made, and is thereafter held by SRR  120 , stitches  122  the needles  124 .  
      In a preferred embodiment of the invention, the needles are retained in the grooves in the proper direction by a retaining ring as shown in  FIG. 12  to which reference is now made. In this embodiment, the envelope of cylinder  112  contains a recess  128  in which a needle retaining ring  130  is disposed. In order to release the pierced transplant, it may be necessary to tear the needle retaining ring.  
      Handling of the Transplant  
      As explained above, the concave side of the transplant is most vulnerable and is not to be touched or otherwise disturbed. In accordance with an embodiment of the invention, the upper opening of the circular knife is sealed off except for an opening as described in  FIG. 13  to which reference is now made. A valve, designated  140  is disposed in the upper seal  142  for letting gas in as described by arrow  144 , to pressurize the void volume within the closed chamber formed inside the circular knife. Typically, gas used for such a task is air, but other gases can be used such as CO 2  or nitrogen. Subsequently, the transplant tissue  146  is subjected to the pressure formed inside the circular knife. The purpose of this pressurizing is twofold. First, a counter force is provided against the force of the piercing needles. Second, the gas pressure can be used to assist in detaching the tissue from the circular knife. The externally oriented surface of the tissue, facing the inner volume of the circular knife, which is extremely vulnerable, can be kept untouched. When the transplant has been ejected from the circular knife, it can be handed to the medical team. Before grafting, it is turned upside-down, to be further placed over the cut-hole in the recipient&#39;s eye. Suturing can commence immediately, using the ready-inserted needles. In practice, in addition to the initial number of needles and sutures supplied, extra suturing is carried out, to enhance the fixation of the transplant to the recipient eye.