Abstract:
Apparatus and method incorporating a trephine for cutting an IOL optic from an IOL blank in a rotational cutting movement.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to the manufacture of intraocular lenses (hereinafter IOLs). More particularly, the invention relates to an apparatus and method incorporating a trephine for cutting an IOL from a blank material.  
           [0002]    A common and desirable method of treating a cataract eye is to remove the clouded, natural lens and replace it with an artificial IOL in a surgical procedure known as cataract extraction. IOLs are available in many different configurations and materials which the surgeon chooses from based on the needs of the patient. Some of the more common IOLs include an optic and one or more but usually two haptics extending from the optic for anchoring the IOL within the eye. The IOL optic may itself be bi-convex, piano-convex, plano-concave, plano-plano, or bi-concave, for example. The optic may also include spheric and/or aspheric optics on one or more surfaces thereof. Materials from which IOLs are made include silicone, silicone acrylates, hard and soft acrylics, for example. The haptics may be of the same or different material from which the optic is formed. Presently popular IOL designs have a flexible optic formed of silicone elastomer or soft acrylic, for example, while the haptics are formed from a more rigid material such as PMMA which is a hard acrylic, for example. A flexible optic portion is desirable so that the optic may be folded and/or compressed for delivery through a relatively small incision made in the eye (e.g., about or less than 3 mm). Once in the eye, the optic resumes its original, unstressed shape. More rigid haptics are desirable so that they may function to locate and stabilize the optic within the eye. The haptics may be formed integrally with the optic or attached to the optic after the optic is formed. An example of co-molding the optic and haptics together where the optic is formed from a flexible material and the haptics are formed from a rigid material may be seen in U.S. Pat. Nos. 5,217,491 and 5,326,506 to Vanderbilt. The resultant rod of composite material is then machined (e.g., milled or lathed) into the final IOL shape including both the optic and haptic portions thereof.  
           [0003]    Various methods for making IOLs have been proposed in the prior art, with molding and milling/lathing being the most popular.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an apparatus and method for making an IOL which incorporates a trephine for cutting the IOL optic from a blank material of silicone, for example. The IOL blank is preferably molded and then polished for a smooth surface. The trephine then cuts and defines the IOL optic peripheral edge which requires no further polishing as is required in many of the prior optic forming methods. The trephine may be mounted within a fixture having a work piece holder upon which the blank material may be positioned for cutting. In a preferred embodiment, the blank material is moved relative to the trephine in a simultaneous rotating and linear translation to make the cut. The blank is preferably supplied in a disc form with the trephine cutting the disc at a location which is radially inward of the outer periphery of the disc. As such, the trephine cuts the desired optic diameter while leaving an outer ring of material which is discarded or recycled. The trephine is preferably removable from the fixture such that it may be quickly and easily replaced when the blade thereof is worn, or when it is desired to change to a trephine having a different optic cutting diameter.  
           [0005]    The resultant optic is formed with a straight peripheral wall that extends substantially parallel to the optical axis of the IOL optic. At least the juncture of the optic posterior surface and peripheral wall form a sharp peripheral edge which has been clinically shown to help reduce the occurrence of posterior capsular opacification (PCO) or secondary cataracts.  
           [0006]    The fixture may also include an optic release mechanism for lifting the cut optic from the fixture for easy retrieval thereof with a pair of tweezers, for example. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0007]    [0007]FIG. 1 a  is a side elevational, cross-sectional view of a preferred embodiment of the invention showing the IOL cutting mechanism in the ready position and the upper punch shown in spaced relation thereto;  
         [0008]    [0008]FIG. 1 b  is a cross-sectional view of the IOL cutting mechanism taken generally through the line  1   b - 1   b  of FIG. 1 a;    
         [0009]    [0009]FIG. 2 is a plan view of a prior art IOL;  
         [0010]    [0010]FIG. 3 a  is the view of FIG. 1 a  with a portion of the IOL cutting mechanism shown in the raised position for retrieval of the cut IOL;  
         [0011]    [0011]FIG. 3 b  is a cross-sectional view of the IOL cutting mechanism taken generally through the line  3 - 3   b  of FIG. 3 a;    
         [0012]    [0012]FIG. 4 a  is a side elevational view of the trephine holder;  
         [0013]    [0013]FIG. 4 b  is a top plan view thereof;  
         [0014]    [0014]FIG. 4 c  is a cross-sectional view taken generally through the line  4   c - 4   c  of FIG. 4 b;    
         [0015]    [0015]FIG. 5 a  is a side elevational view of the trephine blade;  
         [0016]    [0016]FIG. 5 b  is a top plan view thereof;  
         [0017]    [0017]FIG. 6 a  is a side elevational view of the lens pusher,  
         [0018]    [0018]FIG. 6 b  is a detail view of the lens-engaging end thereof;  
         [0019]    [0019]FIG. 6 c  is a top plan view thereof, and  
         [0020]    [0020]FIG. 7 is a scanning electron microscope image at 50× magnification showing an IOL peripheral wall which was cut using the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    Referring now to the drawing, there is seen in FIG. 1 a  an IOL cutting fixture  10  useful for cutting an IOL optic from an IOL blank. A representative IOL  12  is seen in FIG. 2 to include an optic  14  and two haptics  16   a  and  16   b . The optic  14  is provided to provide focusing within the eye while the haptics provide locating means for proper positioning of the IOL within the eye. It is understood that the particular configuration of IOL  12  is provided for discussion purposes only and may vary from that shown herein (e.g., the IOL may include one or more haptics of any configuration and the IOL anterior and posterior optic surfaces may likewise vary). The invention is used for cutting the optic portion  14  of an IOL where the haptic portions are subsequently attached to the optic using any known means (e.g., gluing).  
         [0022]    The IOL blank (not shown) from which the optic  14  is to be cut using the present invention is in the shape of a circular disc having anterior and posterior optical surfaces of the desired configuration (e.g., convex, concave or plano and may incorporate spherical and/or aspherical optics). The IOL blank itself may be molded using a metal mold, for example, and have the holes formed into the periphery for the subsequent staking of the haptics to the optic. Fixture  10  is therefore used for cutting a finished, square edge of the optic from the blank. Square edges at the periphery of an IOL optic have been clinically shown to help reduce the occurrence of posterior capsular opacification (PCO) or secondary cataracts as noted above.  
         [0023]    Fixture  10  includes a base  20  to which a trephine  22  is mounted having a circular cutting edge  24  at one end thereof and a longitudinally extending bore  26  extending entirely therethrough from cutting edge  24  to the opposite, base end  28  thereof (see also FIGS. 5 a,b ). The diameter of the cutting edge  24  is selected to correspond to the desired resultant optic diameter (e.g., about 5-7 mm, and more preferably about 6 mm). The IOL blank diameter from which the finished optic is to be cut using fixture  10  is of course larger than the resultant cut diameter of the optic and may be in the range of about 7-9 mm and more preferably is about 8 mm in diameter.  
         [0024]    Trephine  22  is removably mounted within a trephine holder  28  having a longitudinal bore  30  extending entirely therethrough from top end  28   a  to bottom end  28   b  thereof (see also FIGS. 4 a - c ). Bore  30  is sized and configured so that the trephine  22  may be inserted therein from bottom end  30  and come to rest at a position therein with the trephine cutting edge  24  located slightly above the counter-sunk top surface  28   c . Trephine  22  and trephine holder  28  are removably mounted to base  20  via mating threads  34  formed adjacent the bottom end  28   b  of holder  28  and along the inner wall of a counter-sunk bore  36  formed in the top of base  20 . Since the component parts are removably mounted to each other, the trephine  22  may be quickly exchanged for a new trephine when the cutting edge  24  thereof becomes dull or it is desired to switch to a different diameter cutting edge.  
         [0025]    A lens pusher  40  is provided which extends through bore  36   b  and continues through the trephine central bore  26 . The bottom end  40   b  of pusher  40  rests upon a rocker component  42  which itself is pivotally mounted between the spaced, parallel legs  20   a  and  20   b  of base  20 . Lens pusher  40  is thus mounted for reciprocal longitudinal movement within trephine  22  and trephine holder  28 . Accordingly, lens pusher  40  may be moved between the lowered position seen in FIGS. 1  a,b  where the top end  40   a  thereof is located below the counter-sunk top surface  28   c  of trephine holder  28 , to the raised position seen in FIGS. 3 a , 3   b  where the top end  40   a  thereof is located above the counter-sunk top surface  28   c  of trephine holder  28 . Reciprocal movement may be imparted by way of a pusher rod  44  which extends through another bore  46  formed in base  20  which extends parallel to bores  36   a,b . The bottom end  44   b  of pusher rod  44  rests upon the end of rocker component  42  opposite lens pusher end  40   b.    
         [0026]    It is noted that lens pusher  40  is biased in the lowered position seen in FIGS. 1 a , 1   b  by a spring  48  which surrounds the lens pusher shaft. The spring top end bears against the bottom surface  41  of bushing  43  (see FIG. 1 a ) and the spring bottom end bears against the ledge of the bottom end  40   b  of lens pusher  40 . Thus, lens pusher  40  may be moved from the biased, lowered position to the raised position seen in FIGS. 3 a,b  by simply pressing downwardly on pusher rod top end  44 . Further explanation of this movement will be explained below.  
         [0027]    Discussion is now turned to the upper punch mechanism  50  and the process by which an IOL optic is cut from an IOL blank. Referring to FIG. 1 a , upper punch mechanism  50  is seen to include a main body portion  52  having a top surface  52   a  and a bottom end  52   b  with first and second, longitudinally extending bore portions  54   a  and  54   b . Bottom bore portion  54   b  has an inner diameter slightly larger than the outer diameter of trephine holder  28  such that punch body portion  52  may be mounted upon trephine holder  28 . A lens press insert  56  is mounted within upper bore portion  54   a  via an insert holder  58  which is slip-fit within bore  54   a . The bottom edge  56   a  of lens press insert  56  is located at a position below upper bore portion  54   a  and within lower bore portion  54   b . A pair of pins  60   a,b  are inserted via bearings  62   a,b  through the wall of body  52  with the pin ends  60   a ′,  60   b ′ extending radially into lower bore  54   b . Pins  60   a,b  are preferably about 180° offset from each other. A pair of helically extending grooves  64   a ,  64   b  are formed in the outer surface of trephine holder  28  whereby pin ends  60   a ′,  60   b ′ may be inserted into the top end of the grooves adjacent top surface  28   a  (see FIG. 4 a ). The grooves first extend longitudinally toward bottom end  28   b  and then extend in a spiral pattern around the trephine holder body.  
         [0028]    To begin the cutting process, a circular IOL blank is placed upon the trephine cutting edge  24  which is located slightly above the counter-sunk surface  28   c  of trephine holder  28  yet below the trephine holder upper surface  28   a . The upper surface  28   a  defines a circular counter-sunk surface  28   c  as seen best in FIG. 4 b . The outer diameter of the counter-sunk surface  28   c  is sized to approximate the diameter of the IOL blank being placed therein such that the IOL blank becomes centered on the trephine cutting edge  24 . With the IOL blank resting on trephine cutting edge  24 , the upper punch body  52  is lowered onto the trephine holder  28  with pin ends  60   a ′,  60   b ′ aligned with respective grooves  64   a ,  64   b  formed in holder  28 . Since the grooves first extend longitudinally toward holder bottom edge  28   b , the punch body  52  will translate linearly in a telescoping movement onto trephine holder  28 . Upon reaching the end of the longitudinally extending section of the grooves, the lens press insert bottom edge  56   a  rests lightly upon the IOL blank. The operator then rotates punch body  52  with pin ends  60   a ′,  60   b ′ riding along the helical extents of grooves  64   a ,  64   b  whereby the lens press insert  56  pushes against the IOL blank, forcing it into the trephine cutting edge  24  which itself remains stationary. It is understood, however, that variations in operation may be made so that the trephine instead moves into the IOL blank which is held stationary. The trephine and IOL blank may also move together into one another if desired.  
         [0029]    It will be realized that the above-described rotation of the punch body  52  relative to the trephine holder  28  causes the trephine cutting edge  24  to cut through the IOL blank. It is noted that the lens press insert  56  includes a longitudinal bore  56   b  extending therethrough. This is provided so that the central optical surface of the IOL blank is not touched by the lens press insert which could potentially cause harm to the optical surface. The diameter of the lens press insert bottom edge  56   a  is sized to so that the IOL blank is sandwiched between the insert and the trephine cutting blade  24 . Once the IOL blank has been cut, the punch body is rotated in the opposite direction and removed from the trephine holder  28 , leaving the cut IOL optic resting on the trephine cutting blade  24 . The annular flash which has been cut from the optic is located around the cutting edge  24  on counter-sunk surface  28   c . To remove the flash, the operator uses tweezers, extending them within either radial relief  28   d  or  28   e  formed in the top surface of the trephine holder  28  (see FIG. 4 b ). With the flash removed, the operator moves the lens pusher  40  to the raised position by pressing downwardly on pusher rod  44  as explained above. With the cut IOL optic resting on the top end  40   a  of pusher  40 , the IOL optic is readily accessible for retrieval thereof. The operator may thus retrieve the cut IOL optic using a pair of tweezers, for example, by extending the tweezer tips through the relief  40   c  formed in top end  40   a  (see FIGS. 6 a - c ).  
         [0030]    Attention is turned to FIG. 7 which is a scanning electron microscope image of an IOL optic cut using the present invention. The resultant peripheral wall  14   c  is defined between anterior and posterior peripheral edges  14   a ,  14   b  which are located at the junctures of the anterior optic surface  14   d  and opposite posterior optic surface, respectively (not shown). Helical striations  14   e  are seen in peripheral wall  14   c  which are a result of the rotational movement of the trephine cutting edge  24 . These striations  14   e  may contribute to a decrease in unwanted glare caused by reflection of light off the edge of the implanted optic.  
         [0031]    While the invention has been described with reference to a preferred embodiment thereof, it will be appreciated by those skilled in the art that various modifications may be made thereto without departing from the full spirit and scope of the invention as defined by the claims which follow. For example, one or more of the movements of fixture  10  may be automated and incorporated into other IOL processing stations such as haptic attachment and inspection, for example.