Patent Publication Number: US-2005143750-A1

Title: IOL inserter plunger

Description:
RELATED APPLICATION  
      This application claims the benefit under 35 USC §119(e) of prior U.S. Provisional Application Ser. No. 60/533,405 filed Dec. 30, 2003. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates to ophthalmic surgical devices. More particularly, the present invention relates to a device for inserting an intraocular lens (IOL) into an eye.  
      IOLs are artificial lenses used to replace the natural crystalline lens of the eye when the natural lens has cataracts or is otherwise diseased. IOLs are also sometimes implanted into an eye to correct refractive errors of the eye in which case the natural lens may remain in the eye together with the implanted IOL. The IOL may be placed in either the posterior chamber or anterior chamber of the eye. IOLs come in a variety of configurations and materials. Some common IOL styles include the so-called open-looped haptics which include the three-piece type having an optic and two haptics attached to and extending from the optic; the one-piece type wherein the optic and haptics are integrally formed (e.g., by machining the optic and haptics together from a single block of material); and also the closed looped haptic IOLs. Yet a further style of IOL is called the plate haptic type wherein the haptics are configured as a flat plate extending from opposite sides of the optic. The IOL may be made from a variety of materials or combination of materials such as PMMA, silicone, hydrogels and silicone hydrogels, etc.  
      Various instruments and methods for implanting the IOL in the eye are known. In one method, the surgeon simply uses surgical forceps having opposing blades used to grasp the IOL and insert it through the incision into the eye. While this method is still practiced today, more and more surgeons are using more sophisticated IOL inserter devices which offer advantages such as affording the surgeon more control when inserting the IOL into the eye. IOL inserter devices have recently been developed with reduced diameter insertion tips which allow for a much smaller incision to be made in the cornea than is possible using forceps alone. Smaller incision sizes (e.g., less than about  3 mm) are preferred over larger incisions (e.g., about 3.2 to 5+mm) since smaller incisions have been attributed to reduced post-surgical healing time and complications such as induced astigmatism.  
      Since IOLs are very small and delicate articles of manufacture, great care must be taken in their handling. In order for the IOL to fit through the smaller incisions, they need to be folded and/or compressed prior to entering the eye wherein they will assume their original unfolded/uncompressed shape. The IOL inserter device must therefore be designed in such a way as to permit the easy passage of the IOL through the device and into the eye, yet at the same time not damage the delicate IOL in any way. Should the IOL be damaged during delivery into the eye, the surgeon will most likely need to extract the damaged IOL from the eye and replace it with a new IOL, a highly undesirable surgical outcome.  
      Thus, as explained above, the IOL inserter device must be designed to permit easy passage of the IOL therethrough. It is equally important that the IOL be expelled from the tip of the IOL inserter device and into the eye in a predictable orientation and manner. Should the IOL be expelled from the tip too quickly or in the wrong orientation, the surgeon must further manipulate the IOL in the eye possibly resulting in trauma to the surrounding tissues of the eye. It is therefore highly desirable to have an inserter device which allows for precise loading of the IOL into the inserter device and which will pass and expel the IOL from the inserter device tip and into the eye in a controlled, predictable and repeatable manner.  
      To ensure controlled expression of the IOL through the tip of the IOL inserter device, the IOL must first be loaded into the IOL inserter device. The loading of the IOL into the inserter device is therefore a precise and very important step in the process. Incorrect loading of an IOL into the inserter device is oftentimes cited as the reason for a failed IOL delivery sequence. Many IOL inserter devices on the market today require the IOL to be loaded into the inserter at the time of surgery by the attending nurse and/or surgeon. Due to the delicate nature of the IOL, there is a risk that the nurse and/or surgeon will inadvertently damage the IOL and/or incorrectly load the IOL into the inserter device resulting in a failed implantation.  
      In a typical IOL inserter device, the IOL inserter utilizes a plunger having a tip which engages the IOL (which has been previously loaded and compressed into the inserter lumen) to pass it through the inserter lumen. The IOL thus interfaces with the plunger tip as well as the lumen of the inserter device. The lumen typically is dimensioned with a narrowing toward the open tip thereof in order to further compress the IOL as it is advanced through the lumen. The tip of the lumen is sized for insertion through the surgical incision which, as stated above, is presently preferred in the sub  3 mm range. Thus, an inserter lumen will typically be dimensioned larger at the load area of the IOL and gradually decrease in diameter to the tip of the lumen where the IOL is expressed into the eye. It will be appreciated that the compressed diameter of the IOL at the lumen tip is the same as the inner diameter of the lumen tip, preferably sub 3 mm as stated above. Each of these component interfaces are dynamic in the sense that the forces acting between the interfacing components (i.e., the IOL, the plunger tip and the inserter lumen) will vary as the IOL is pushed through the lumen. Control of these dynamic forces is therefore of utmost importance or otherwise the IOL may be damaged during delivery due to excessive compressive forces acting thereon. For example, as the IOL is advanced by the plunger through an ever-decreasing diameter lumen, the IOL is being compressed while at the same time the forces necessary to push the IOL through the lumen increase. This may lead to excessive force between the plunger tip and the IOL resulting in possible damage to the IOL and/or uncontrolled release of the IOL from the lumen tip. Also, the force of the plunger tip may cause the IOL to twist and/or turn as it is moved through the inserter whereby the force between the IOL and the plunger tip and/or the inserter lumen may uncontrollably increase to the point of IOL damage.  
      Various inserter devices have been proposed which attempt to address these problems, and particularly the problem of controlling the force between the plunger, lumen and IOL, yet there remains a need for an IOL inserter which itself is simple in design and also simplifies operation of the IOL inserter device and thereby the IOL delivery process.  
     SUMMARY OF THE INVENTION  
      The invention provides an IOL inserter having an improved plunger component for inserting IOLs having one or more curved haptics extending from the optic thereof. In particular, the plunger shaft incorporates a recessed area defined between the distal plunger tip and a curvilinear ramp wherein the trailing haptic of the IOL resides throughout the IOL delivery process. The curvilinear ramp acts as a stop for the trailing haptic whereby any chance of the haptic becoming entangled around the plunger shaft during IOL delivery is minimized or eliminated. In the preferred embodiment, the curve of the ramp closely matches the curve of the trailing haptic. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a prior art inserter device;  
       FIG. 2  is a fragmented, top plan view of the IOL loading area of the device of  FIG. 1 ;  
       FIG. 3  is an enlarged, partial perspective view of the plunger component of  FIGS. 1 and 2 ; and  
       FIG. 4  is an enlarged, partial perspective view of the inventive plunger component. 
    
    
     DETAILED DESCRIPTION  
     II. Prior Art  
      The present invention is directed towards IOL inserters having a tubular body defining a longitudinal passageway or lumen extending from a proximal end to a distal tip of the inserter, and a plunger component which telescopes in the open proximal end of the tubular body. A representative prior art inserter device  10  is seen in  FIGS. 1-3  and is disclosed in commonly owned U.S. Pat. No. 5,944,725, the entirety of which is incorporated herein by reference. Device  10  includes a tubular body  12  having an open proximal end  14  and opposite distal tip  16  which is inserted into an incision in an eye for passing an IOL  15  through the inserter, out tip  16  and into the eye. IOL  15  is loaded into body  12  through any known IOL loading means, e.g., through an opening  18  designed into the inserter body. Body proximal end  14  includes a finger hold  20  and plunger  22  includes a finger press  22   a  at the proximal end thereof for pressing and advancing the plunger through the longitudinal passageway of the tubular body  12  in the manner of a syringe. A plunger tip  22   b  which may be bifurcated as seen best in  FIG. 3 , is provided at the distal end of the plunger for engaging and pushing the IOL optic  15  through and out the distal tip  16  of the inserter body  12 . The IOL includes two curved haptics  15   a  and  15   b as seen in  FIG. 2 . The IOL optic  15  is placed in the inserter body  12  with the proximal, trailing haptic  15   a  positioned within the plunger recess  22   d  and the distal, leading haptic  15   b engaged by a catch  30  of haptic puller  32 . Once the IOL has been initially positioned in body  12 , compressor  40  is closed which compresses the IOL optic  15  within body  12 . Haptic puller  32  is pulled away from inserter tip  16  which draws and straightens the leading haptic  15   b into the inserter tip. This prevents the leading haptic from becoming bunched up within the inserter as the IOL is expressed therefrom and into an eye.  
      It is important that the plunger  22  be properly aligned and rotationally fixed within the tubular body so as to ensure proper engagement of the IOL  15  with plunger tip  22   b.  Plunger alignment and rotational fixing can be achieved by forming the body  12  and proximal end of the plunger in a non-circular (e.g., oval) cross-sectional shape. The proximal end of the plunger may be provided with a plurality of radially extending fins  22   c  which act to align and rotationally fix plunger  22  within the tubular body.  
      It is understood that the invention is directed at the plunger component and particularly the plunger-haptic interface thereof. The other parts of the plunger and inserter (e.g., the cross-sectional shape of the inserter body, the IOL loading area, the inserter distal tip, the plunger tip, etc.) may therefore be of any desired configuration. A prior art plunger  22  has a plunger-haptic interface in the form of a recess  22   d.  As seen best in  FIG. 3 , recess  22   d  is defined on the plunger shaft between distal tip  22   b  and stepped surface  22   e.  The stepped surface  22   e  is rather abrupt and includes sharp edges which could cause damage to the trailing haptic during delivery of the IOL through the inserter. Furthermore, surface  22   e  lies along a plane perpendicular to the longitudinal axis of the plunger shaft  22 . This creates an unwanted stress point along the plunger shaft which could cause plunger failure, particularly when a high axial force is being applied to the plunger which may be necessary to push the IOL through a sub 3 mm inserter tip.  
     II. A Preferred Embodiment of the Invention  
      A preferred embodiment of a plunger  50  is seen in  FIG. 4 . Plunger  50  may take the place of plunger  22  in inserter  10  although it is understood that plunger  50  may be used with other inserter designs as desired. Plunger  50  includes a plunger tip  50   a  which is preferably bifurcated to create slot  50   b  for engaging the periphery of the IOL optic  15  and push the IOL through inserter body  12  and out distal tip  16 . A recess  50   c  is provided along the distal section of the plunger shaft and is defined by angled surface  50   e  adjacent plunger tip  50   a  at the distal end thereof and by a curvilinear ramp  50   d  at the other end thereof. The IOL trailing haptic  15   a  may be positioned within recess  50   c  when the IOL is initially loaded into the device in the manner shown in  FIG. 2 .  
      The curve of ramp  50   d  is preferably matches or at least approximates the curve of the trailing haptic such that the trailing haptic may lie in abutting relationship along the length of the ramp  50   d.  As such, ramp  50   d  acts as a stop against which the trailing haptic abuts during plunger advancement. This stop feature prevents the trailing haptic from becoming entangled around the plunger shaft during plunger advancement. Curvilinear ramp  50   d  traverses as a smooth arc across the plunger shaft and removes the sharp edged perpendicular orientation of the prior art stepped surface  22   e.  A such, the stress point created by the prior art recess configuration is not present in the preferred embodiment of the present invention and the potential for plunger failure caused by such a stress point is therefore minimized or eliminated.  
      In the preferred embodiment, the plunger tip is bifurcated as stated above and includes a slot  50   b  for engaging the periphery of the IOL optic  15 . The plane along which slot  50   b  lies is therefore the same as the plane along which the IOL optic  15  lies. Since the trailing haptic initially extends along the plane of the optic, the plane along which curvilinear ramp  50   d  lies should likewise be parallel to the plane in which slot  50   b  lies. As such, proper orientation of the IOL optic and trailing haptic with respect to the plunger  50  is ensured.