Abstract:
A strand of resilient material has multiple tissue-engaging portions for engaging and spreading eyeball tissue segments apart. The strand is formed as a continuous ring with straight sides joined by corner portions. The corner portions constitute the tissue-engaging portions and have top and bottom sections and a connecting arc of the strand to form a gap receiving for receiving the tissue.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Provisional Application No. 61/411870, filed Nov. 9, 2010. 
     
    
     BACKGROUND 
       [0002]    During ophthalmic surgery, it is sometimes desirable to enlarge an opening in eyeball tissue, such as, for example, holding the iris open for access through the pupil. It has been proposed that, at least in some cases, expansion be achieved mechanically by one or more devices that engage against opposing edge portions of the eyeball tissue, such as inner edge portions of the iris. One such device is disclosed in U.S. Patent Publication No. 2008/0269888, of Boris Malyugin, titled “Ring Used in a Small Pupil Phacoemulsification Procedure” which publication is expressly incorporated by reference herein. 
       SUMMARY 
       [0003]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
         [0004]    A strand of resilient material has multiple tissue-engaging portions for engaging and spreading ocular tissue segments apart. The strand is formed as a continuous ring with straight sides joined by corner portions. The corner portions constitute the tissue-engaging portions and have top and bottom sections and a connecting arc of the strand to form a gap for receiving the tissue. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0005]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0006]      FIG. 1  is an enlarged, diagrammatic top perspective of an extension ring of the type shown in Maylugin U.S. Patent Publication No. 2008/0269888; 
           [0007]      FIG. 2  is a further enlarged, fragmentary detail thereof; 
           [0008]      FIG. 3  is a diagrammatic top plan thereof; 
           [0009]      FIG. 4  is a diagrammatic top plan thereof corresponding to  FIG. 3  but with parts in different positions; and 
           [0010]      FIG. 5  is a diagrammatic side elevation thereof; 
           [0011]      FIG. 6  is a diagrammatic top plan of a modified extension ring; 
           [0012]      FIG. 7  is a diagrammatic top perspective thereof during manufacture; 
           [0013]      FIG. 8  is a diagrammatic top perspective of manufacturing equipment therefor; 
           [0014]      FIG. 9  is a diagrammatic section of the manufacturing equipment therefor; 
           [0015]      FIG. 10  is a diagrammatic top perspective of equipment for insertion thereof; 
           [0016]      FIG. 11  is a diagrammatic top perspective of equipment for insertion thereof corresponding to  FIG. 10  but with parts in different positions; 
           [0017]      FIG. 12  is a detail of insertion equipment for the embodiment of  FIG. 1 ; 
           [0018]      FIG. 13  is a detail of insertion equipment for the embodiment of  FIG. 6 ; 
           [0019]      FIG. 14  is a diagrammatic top plan illustrating insertion of the embodiment of  FIG. 6 ; and 
           [0020]      FIG. 15  is a diagrammatic top plan illustrating the embodiment of  FIG. 6  after insertion. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  shows a square configuration of the Malyugin ring  10  which has loops  12 ,  14 ,  16 , and  18  located at the corners of the four sides  20 ,  22 ,  24 , and  26 . Each loop is formed by one full turn. 
         [0022]      FIG. 2  shows one aspect of the Malyugin construction in which the ring is formed from one length of material with two ends  30  and  32  that are “butt attached” by adhesive represented at  34 . Each of the ends  30  and  32  may have an indent  36 ,  38 , respectively, such that the adhesive  34  can flow into the indents to increase the strength of the butt attachment. 
         [0023]    The ring  10  can be drawn into an insertion tube and, after insertion of the tube into the posterior chamber of the eye, such as through a small slit in the cornea, projected from the tube and manipulated to expand the opening of the iris.  FIG. 3  shows the initial stages of the ring  10  being inserted into the pupil P. As stated in paragraph [0019] of the Malyugin patent publication, “A tool such as a forceps (not shown) can be used to pull the iris so that iris tissue is inserted into loop  14  of the ring  10 ” and, with reference to  FIG. 4 , “the ring  10  can be manipulated so that iris tissue is inserted [into] loops  12  and  16 .” With reference to  FIG. 5 , as stated in paragraph [0020], when the ring has been fully deployed:
       As shown in  FIG. 5  each loop  12 ,  16 , etc. has a gap  58  that receives and captures iris tissue. The loop design provides an easy means of inserting and capturing iris tissue.       
 
         [0025]      FIG. 6  shows a modified iris extension ring in accordance with the present invention. It should be noted that in  FIG. 6 , and all following drawings, sizes are exaggerated for ease of illustration and understanding. Ring  60  is formed from a single long strand of resilient material such as 4-0 or 5-0 polypropylene surgical suture. The ring material has memory characteristics such that when held taut in a desired shape and then heat treated and cooled, such shape will be retained in the relaxed or “at rest” state. Due to the resiliency of the material, from the relaxed state the material can be deformed, in which case it applies a resisting force tending to return to the preformed shape. 
         [0026]    In the case of the embodiment of the present invention shown in  FIG. 6 , ring  60  has four straight sides  62 ,  64 ,  66 , and  68 . Side  62  has the end butt joint  70  where a drop of adhesive  72  secures the ends  74 ,  76 , such ends preferably having the indented portions  78  to increase the holding effectiveness of the adhesive. 
         [0027]    In the plan view of  FIG. 6 , side  64  is perpendicular to side  62 . These sides are joined by a corner portion  63  which has three distinct bends, namely, a first obtuse bend  80  (essentially 135° inward and to the left as viewed in  FIG. 6 ), a second return bend  82  (essentially 180° inward and then down away from the viewer and then toward the right as viewed in  FIG. 6 ), and a third obtuse bend  84  (essentially 135° up and to the left as viewed in  FIG. 6 ). Corner  65  joining sides  64  and  66  is identical to corner  63  with the three distinct portions  80 ,  82 ,  84 , as are the two additional corner portions  67  (joining sides  66  and  68 ) and  69  (joining sides  68  and  62 ). 
         [0028]    The shape of the ring embodiment  60  can be achieved by use of a winding fixture, aspects of which are shown diagrammatically in  FIG. 7 . The fixture includes a composite jig having a thin plate  100  with four generally radially extending arms  102  spaced 90° apart. Vertical pins  104  extend upward through holes in the outer end portions of the arms  102  at locations corresponding to the obtuse bends  80 . The end portions of the arms  102  also have short tabs  106  curved down from the plane of the remainder of the plate  100 , approximately aligned with the pins  104 . 
         [0029]    Aspects of the ring  60  may be better appreciated in conjunction with the manner in which the ring is manufactured. Starting at the left of  FIG. 7 , a length of the suture material S is stretched to the lowermost pin  104  and wound around the outer periphery of the pin to achieve the inward obtuse bend  80  of approximately 135° for the corner portion  63 . From there the suture extends along the top of the plate  100  to the inner edge of the associated tab  106 , then down under the plate and back outward to form the inner bend  82  of approximately 180°. This section of the suture extends along the face of the tab adjacent to the corresponding arm  102  and then along the outer edge of tab and toward the next pin  104  to form the last obtuse bend  84  of corner portion  63 . Thus, there is a short stretch of suture that extends almost radially along the face of the tab and the obtuse bend  84  which leads to the side  64 . The winding procedure is the same at corner portions  65 ,  67 , and  69 , with the opposite (“exiting”) end portion S′ of the length of suture extending to the right as seen in  FIG. 7 , along side the entering portion S. 
         [0030]      FIG. 8  shows the winding fixture on a smaller scale (dimensions still exaggerated due to the extremely small nature of the ring, particularly the suture which may be on the order of 0.006 to 0.008 inch diameter). Plate  100  is mounted on a central hub  110  fixed to an upper elevator block  112 . Block  112  is guided for vertical movement by bolts  114  and the pins  104  that extend somewhat loosely through the elevator block  112  to a base block  115 . An entrance screw  116  is provided to anchor the stretch of suture that leads to the winding pins, and an exit screw  118  is used to anchor the opposite or exiting end portion of the suture after the winding operation is completed (i.e., after the suture is routed as shown in  FIG. 7 ). With the suture thus held in the desired form, it is heated in an oven to close to the softening temperature for a period of time sufficient to achieve the desired memory characteristics. In a representative embodiment, the heat treating can be at a temperature of 165° C. to 170° C. for 6 to 8 minutes, but the temperature and time may be adjusted depending on the particular material used. Thereafter, the fixture and iris extension ring contained thereon are cooled. 
         [0031]    With reference to  FIG. 7 , after cooling, the entering and exiting stretches of suture can be severed in one snip, preferable approximately midway between the adjacent corners, such as at the location indicated by the broken line L in  FIG. 7 . Then, as represented in  FIG. 9 , the upper elevator block  112  is raised such that the winding plate  100  is lifted to a position above the tops of the pins  104 , which simplifies removal of the ring  60  from the fixture, prior to completion of the ring by joining the cut ends as previously described. 
         [0032]    With reference to  FIG. 10 , a single completed ring  60  can be fitted in a recess of a conventional holder having a bottom section  120  and lid section  122 . Such holder has a channel leading to the recess in which the ring  60  is positioned, for reception of the insertion tube  124  of an implanting instrument  126 .  FIG. 11  illustrates the parts connected with the insertion tube received in the channel. 
         [0033]      FIG. 12  is an enlarged fragmentary side elevation of the distal end portion of the insertion instrument, which includes the distal end section of an insertion tube  124  and a reciprocating hook member  128 . In the case of the Malyugin ring, the insertion instrument has a round hooked end  130  which is moved distally and down by manipulation of an operating button ( 132  in  FIG. 10  and  FIG. 11 ) to capture an end loop of the Malyugin ring. For use with the present invention, the hook member  128 ′ is a flat strip twisted so that the distal end portion extends vertically, with a downward-opening notch  132  in such end portion. Manipulation of the operating button moves the distal end portion  128 ′ distally and downward to capture a corner portion of the improved ring in the notch. More specifically, the part captured will be one of the obtuse bends  80 ,  84  of the corner portion. The strip  128 ′ and notch  132  are used to withdraw the ring into the insertion tube, resulting in collapsing the ring as the corners at the sides are forced together. By pulling on one of the obtuse corner sections, a natural result is that the side-opposed corner portions will not be directly opposite each other, but rather will be slightly offset lengthwise, so that they may overlap for a compact nesting inside the insertion tube. 
         [0034]      FIG. 14  illustrates ejecting of the ring  60  in the eye, with the inner bend  82  of corner portion  65  engaged against an edge portion of the iris. Such edge portion rides into the gradual arc of bend  82  with little or no friction that could cause abrasion.  FIG. 15  illustrates the position after the ring  60  has been fully deployed. The innermost bend  82  of each of the corner portions receives a portion of the inner edge of the iris. The ring is sized such that it is in a slightly compressed state when deployed, so that an expansion force is applied against the iris to increase the opening. Also, it can be seen in  FIG. 15  that the bends  82  do not apply the only edge-contacting portions of the ring. A top obtuse bend  80  at each corner leads to the corresponding return bend  82 . Such return bend  82 , in turn, leads to a bottom obtuse bend  84  (shown in broken lines). The side to which a bottom obtuse bend  84  leads is inclined upward (outward) slightly due to the positioning of the suture on the winding fixture, and that side emerges from the pupil approximately midway between adjacent bends, or at least somewhat centrally between the bends. Thus, there are eight spaced points of contact of the iris edge portion by the contracted ring  60  for a more even application of an expanding force. 
         [0035]    As seen in  FIG. 15  ring  60  can be formed with no parts of any corner that directly overlie one another. The dimensions of the ring and the various bends are chosen so that minimal abrasive force is applied to the iris, and no or essentially no pinching or clamping force. Dimensions are selected such that the opening formed by each return bend  82  is at least as great as the marginal thickness of the iris, with no coils or loops located one above the other. 
         [0036]    More specifically, it can be seen in  FIG. 7  that each obtuse bend  80  (best seen for the bend  80  at the top of the view) is angled outward slightly from its pin  104  to the corner between the plate arm  102  and the corresponding tab  106  where the central portion of the return bend  82  is formed. The bottom part of such return bend is canted slightly away from the top part of the bend to the outer edge of the tab. The radius of curvature of the return bend is determined primarily by the thickness of the plate  100 . In a representative embodiment, the plate can be 0.015″ thick. It has been found, however, that the total depth of the channel or notch formed by the return bend will be somewhat greater than the plate thickness, such as 0.019″ to 0.020″ in a representative embodiment. 
         [0037]    While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.