Abstract:
A blade and a blade assembly wherein the blade has a front, beveled, sharpened edge, two side edges meeting at a point spaced from the front edge and at least one attachment structure extending outwardly from each side edge. A blade holder, which extends beyond the side edges and attachment structures of the blade, sits on a top surface of the blade and is attached to the blade by a portion thereof which receives the attachment structures. The holder has an opening in an exposed surface to receive an extension from a drive mechanism such that when the drive mechanism is activated the blade is caused to vibrate or oscillate. The blade is oscillated in a lateral fashion when driven by a rod rotating along a circular path.

Description:
This application is based on Provisional Application 60/231,964 filed Jun. 23, 2000. Applicant claims priority from the filing date of said Provisional Application. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a blade, and a holder for that blade, for use in a manual or automated surgical device used for cutting the cornea of the eye and particularly for forming a corneal flap. Several surgical devices are currently available for cutting corneal tissue or a circular flap in the cornea around the pupil of the eye. These devices, commonly referred to as microkeratomes, are placed on the cornea and held in place by suction applied to the periphery of the cornea. A disposable blade is placed into the device and the sharpened edge of the blade is advanced at a precise angle and a predetermined depth into the corneal tissue. The device then provides for a vibrating or oscillating motion to the blade and allows the blade to be moved in a circular, linear, or curvilinear path around the central axis of the microkeratome. This results in the cornea being cut to raise a thin circular layer of anterior cornea with the incision being from about 100 to 200 micron, in depth and about 10 mm in diameter. In a more recent procedure, referred to as LASIK surgery, the circular corneal incision is combined with laser sculpting of a portion of the cornea. 
     Several microkeratomes are shown in the patent literature. U.S. Pat. No. 5,624,456 covers a device offered by Bausch &amp; Lomb, known as the Hansatome, and U.S. Pat. No. 6,051,009 is directed to blades specifically designed for use in the device shown in the &#39;456 patent. 
     Other patents to microkeratomes of different designs are shown in U.S. Pat. Nos. 5,496,339 and 5,658,303 to Koepnick, U.S. Pat. No. 4,884,570 to Krumeich, U.S. Pat. Nos. 5,501,174 and 5,591,174 to Clark et al, U.S. Pat. No. 5,342,378 to Giraud et al, U.S. Pat. No. 6,022,365 to Aufaure et al, U.S. Pat. No. 5,133,726 to Ruiz et al, and U.S. Pat. No. 4,662,370 to Hoffmann et al. All operate in generally the same manner and all require a disposable blade be inserted therein. However, each device requires a different shaped blade and/or blade with blade holder. Therefore, there is a value in having a disposable blade configuration, which may have varied dimensions, which can be assembled with a suitable blade holder for each different device, using the same assembly techniques, so as to provide ease of manufacturing and uniformity of surgical outcome irrespective of the instrument into which the blade or blade assembly is placed. 
     SUMMARY OF THE INVENTION 
     The invention comprises a blade and a blade assembly wherein the blade has a front, beveled, sharpened edge, and two side edges meeting at a point spaced from the front edge. At least one attachment structure extends from each side edge. A blade holder which extends beyond the side edges, sits on a top surface of the blade and is attached to the blade by a portion thereof which receives the attachment structure. The holder has an opening in an exposed surface to receive an extension from a drive mechanism such that when the drive mechanism is activated the blade is caused to vibrate of oscillate. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 is bottom view of a blade incorporating features of the invention. 
     FIG. 2 is a side view of a first embodiment of a blade assembly including the blade of FIG.  1 . 
     FIG. 3 is a top view of the first embodiment of the blade assembly of FIG.  2 . 
     FIG. 4 is a bottom view of the first embodiment of the blade assembly of FIG.  2 . 
     FIG. 5 is a side view of a second embodiment of a blade assembly including the blade of FIG.  1 . 
     FIG. 6 is a top view of the second embodiment of the blade assembly of FIG.  5 . 
     FIG. 7 is a side view of a third embodiment of a blade assembly including the blade of FIG.  1 . 
     FIG. 8 is a rear view of the third embodiment of the blade assembly of FIG.  7 . 
     FIG. 9 is a bottom view of a variation of the assembled embodiment of FIG.  4 . 
     FIG. 10 is a bottom view of the blade holder of the variation of FIG.  9 . 
     FIG. 11 is a top view of the blade holder of the variation of FIG.  9 . 
     FIG. 12 is a cutaway side view along line  220 - 220  of FIG.  9 . 
     FIG. 13 is a top view of an alternative blade design having a parabolic shape. 
     FIG. 14 is a bottom view of the blade of FIG. 13 mounted in a blade holder. 
     FIG. 15 is a top view of an alternative blade design with a semicircular shape having circular retention means within the periphery of the blade. 
     FIG. 16 is a top view of a blade holder for receiving the blade of FIG.  15 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a top view of a blade incorporating features of the invention. As shown in FIG. 1, the blade  10 , in a preferred embodiment fabricated of a flat surgical steel about 0.01 inches thick, is in the shape of a triangle with a forward portion  12  beveled to a sharp edge  13 . The various triangular embodiments have a forward portion from about 0.45 to about 0.53 inches in width. The triangular blade has a dimension from the forward portion  12  to the point  18  from about 0.27 to about 0.32 inches. The two side edges  14 ,  16  of the blade meet at a point  18  spaced from the front edge  12 . Extending from each of the side edges  14 ,  16  are extensions  20 ,  22 , generally in the plane of the blade. In the embodiment shown in the figures, the extensions  20 ,  22  are circular in shape, the circular extensions intersecting the first and second side edges  14 ,  16  of the blade. In a preferred construction, the circular extension  20 ,  22  have at least about 180° of the circumference extending from the blade. FIGS. 1 and 9 have about 270° of the circumference in the extension while the remaining 90° constitutes the intersection of the extensions  20 ,  22  with the blade side edges  14 ,  16 . 
     In order to adapt the various blades  10  to operate with the various different microkeratomes the blade is generally attached to a holder to form a blade assembly, the holder being designed to receive a drive mechanism. FIGS. 2,  3  and  4  show a side, top and bottom view of a first embodiment of the blade of FIG. 1 attached to a blade holder  24  to form a blade assembly  26 . The blade holder is typically formed of a machined or molded plastic material. As best shown in FIG.  4  and the variation of FIG. 10, the bottom surface  28  of the blade holder  24  has an indented blade receiving portion  25  with raised areas  27  on either side of the indented area sized and shaped to receive the extensions  20 ,  22  as well as a portion of the blade itself. A circular extension  20 ,  22  extending more than 180° in arc is preferred as this provides a self centering function when the blade is attached to the blade  24  holder by various assembly techniques. The blade  10  is retained in the indented blade receiving portion  25  in the blade holder  24  by an adhesive, cold staking, heat staking, over moldings, or snap (detent) fit means. Snap (dent) fittings utilizes a receiving portion with an angled edges  60  as shown in FIG.  12 . Alternatively, a preformed blade  10  may be molded into the plastic blade holder  24  when it is formed. Also, the bottom surface of the blade holder  24  is at an angle to the plane of the top surface, typically 10° to 45°, so that the blade rests at a desired angle to horizontal when placed in the microkeratome. Alternatively, a separate bottom (not shown) can be applied to the blade holder  24  to sandwich the blade  10  between the holder  24  and the bottom cover. 
     As shown in FIG. 3, the blade holder  24  has a non-circular aperture  30  in the top thereof to receive a drive mechanism  50 . Typically, as shown in several of the patents cited above and incorporated herein by reference, the drive mechanism  50  is a rod offset mounted on a rotating shaft. The rod has a diameter substantially the same as the width of the aperture  30 . Rotation of the shaft causes the rod to rotate in a circular path, which in turn causes lateral oscillation of the blade assembly in the microkeratome. This oscillating motion is intended to improve the quality of the cut made by the sharp edge  13  of the blade  10 . In this instance, the drive mechanism  50  enters the aperture  30  in a substantially vertical manner but at an angle to the plane of the blade. This embodiment is designed for use in a microtome manufactured by Bausch &amp; Lomb and referred to as the HANSATOME™. 
     FIGS. 5 and 6 are to a second embodiment of the blade assembly which incorporates the blade  10  of FIG. 1 with a different designed blade holder  40  for use in the C-B™ microkeratome manufactured by Moria. This blade assembly also receives a substantially vertical drive mechanism  50 . However, because the aperture  30  can be a slot or oval, the blade assembly can receive a drive mechanism  50  mounted in other than a vertical manner and still function in substantially the same manner. 
     FIGS. 7 and 8 show a third embodiment designed to receive a drive from other than the vertical. The drive  50  may in fact be parallel to the plane of the blade, as shown in some of the above referenced patents. In such an instance, the blade may be held in the keratome at an angle to the vertical, or horizontal. Like components are numbered the same as in the prior figures. 
     A variation of the blade of FIG.  1  and the holder of FIGS. 2-4 is shown in FIGS. 9-11. In this variation the holder  24  has holes  44  therethrough. While the hole  44  has been shown as round, any shape hole can be used. The purpose of the hole  44  in the holder  24  is to assure proper alignment of the holder  24  on a machining fixture (not shown) when the holder  24  is positioned or refixtured for the machining of the indented blade receiving portion  25 . This assures proper location or registration of the blade with the slot  30  in the assembled product. 
     As shown in FIGS. 2 and 10, the blade holder  24  can also have a groove  46  therein so that one blade of a forceps or tweezer can be inserted therein to grasp the blade  10  for placement of the blade  10  with attached blade holder  24  in to the microkeratome. 
     While FIG. 1 shows the extensions  20 ,  22  as circular pieces extending from the sides, the extensions can be of various different shapes designed to mate with a like shape in the holder. 
     While shown to be in the plane of the blade  10 , the extensions  20 ,  22  can also be at an angle to the plane or be perpendicular to the plane for insertion in matching holes extending into the holder. It is also contemplated that the blade may be fabricated from a material other than stainless steel, such as ceramics, zirconium, sapphire or similar material, or may have coatings on the beveled front edge to aid in creating a smooth cut in the corneal tissue. It is also possible for the blade and blade holder to be fabricated as a single piece with front edge treated to produce a suitable cutting surface or to receive a cutting component, such as a sapphire, or diamond, ceramic or zirconium, cutting edge, such as typically used in other ophthalmic tissue cutting tools. A typical material for construction of the blade holder is acetal (Delrin®), nylon or other engineering plastics which can be formed or machined into structures with dimensions having controlled tolerances. It is also possible that the holder and blade could be formed of a single engineering plastic, capable of forming or being formed into a sharp forward blade edge. Still further, the whole assembly could be of a hard material, such as a ceramic material, which can be honed to a sharp edge. 
     FIGS. 13-16 show additional embodiments of the blade. The overall shape of the blade  100  is parabolic with a front portion thereof removed to form a sharp front edge  13 . The blade  100  is placed in a holder  124  fabricated with an indented portion for receiving the blade  100  with extensions  20 ,  22  in the manner as described in the regard to the embodiments described above. 
     As set forth above, the extensions  20 ,  22  can be of any shape. Also, if they are circular extensions, they preferably include at least about 180° of arc to provide a secure registration of the blade in the holder. The dimensions of the parabolic shape of the blade can be varied. 
     Still further, the blade shape does not have to be parabolic or circular but can be oval (elliptical) in shape or have a compound curved surface. It can also have more than two extensions. 
     FIG. 14 shows the blade of FIG. 13 in the blade holder  24 . 
     A still further variant, shown in FIG. 15, is a circular blade  130  with cut off front portion and, rather than circular extensions, circular incursions  120 ,  122  in the circumferential walls. FIG. 16 is a holder designed to receive the blade of FIG.  15 . Instead of including a indented receiving portion as in the prior described embodiments, this blade shows an alternative holding mechanism which incorporates circular extensions  226  which are inserted in the blade incursions  120 ,  122  to secure the blade  130  to the blade holder  224 . The attachment techniques discussed above can also be used.