Abstract:
An intraocular lens insertion device having a tubular member for receiving the lens and a plunger for pushing the lens into the eye. The lens is held in a suspended position by its haptics so that the optic portion of the lens does not contact the interior of the tubular member. The plunger tip is provided with a slot for holding the lens after it is expelled from the tubular member into the eye in order to alleviate the risks associated with uncontrolled unfolding of the lens or uncontrolled expulsion of the lens from the inserter into the eye.

Description:
This Appln is a 371 of PCT/US95/09973 filed Aug. 7, 1995 and a C-I-P of Ser. No. 08/286,557 filed Aug. 5, 1994, abn. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to a device for inserting a flexible intraocular lens (IOL) into the eye of a patient. 
     BACKGROUND OF THE INVENTION 
     The natural crystalline lens of the eye plays a primary role in focusing light onto the retina for proper vision. However, the lens can become damaged due to injury or become cloudy because of the aging process or disease and form a cataract. To restore vision to the eye, the natural lens must be surgically removed and an artificial lens implanted as a replacement. 
     Many surgical procedures have been developed for removing the natural lens. As an example, phacoemulsification is one such process which has gained wide popularity. According to this procedure, a slender implement is inserted through an incision made in the eye and into the natural lens. The implement produces ultrasonic vibrations and emulsifies the lens. The emulsified portions of the lens are then aspirated out of the eye through a passage provided in the implement. As opposed to other procedures, this lens extraction method requires the surgeon to make only a narrow incision in the eye. In general, the use of a small incision can lessen the trauma and complications experienced during the surgery and postoperatively. 
     A flexible IOL comprises a central optic portion which focuses light on the retina and at least one outwardly extending haptic. Haptics can have a variety of different configurations, but most commonly are either a plate-like extension of the optic or loop shaped. In any event, the haptics extend outwardly to position the optic of the lens in alignment with the pupil. Flexible IOLs are particularly suited for insertion in the eye following a phacoemulsification lens extraction procedure. Whereas placement of a hard, non-foldable IOL would require widening of the small phacoemulsification incision, a flexible IOL can be compressed or folded for passage through the narrow incision in the eye. Once the lens is passed through the incision and released into the eye, it will expand to its original shape and size. 
     A number of different devices have been developed to implant a flexible IOL into an eye. See, for example, U.S. Pat. No. 4,573,998 to Mazzocco, U.S. Pat. No. 4,681,102 to Bartell, U.S. Pat. No. 4,919,130 to Stoy et al., and U.S. Pat. No. 5,275,604 to Rheinish et al. In general, these devices function to pass a compressed lens through the narrow incision made in the eye. These devices, however, require undue manipulation of the lens, include a multiplicity of parts, and/or fail to provide ample control of the lens as it enters the eye. 
     SUMMARY OF THE INVENTION 
     The present invention is a device which enables flexible IOLs to be easily folded, compressed and inserted through an incision in the eye. In general, the insertion device comprises a tubular member for receiving the lens and a plunger for pushing the lens through the tubular member and into the eye. As the lens is pushed through the passage it is compressed into a smaller configuration. The construction of the present invention ensures an easy, sure and consistent compression of the lens. 
     According to one aspect of the invention, the tubular member includes a staging area for holding the lens in an unstressed condition. The lens is preferably held in a suspended position by its haptics so that the optic remains substantially free of contact with the interior of the tubular member. In this manner, the device can be used as the lens package, and the device can be shipped and stored with the lens already in place and ready for use. As a result, unnecessary manipulation of the lens is avoided. According to another aspect of the invention, the plunger tip is provided with a structure which holds the lens to the plunger when the lens is pushed out of the tubular member. The distal tip of the plunger is preferably bifurcated to define a slot for partially receiving and gripping the lens. With this construction, the plunger is able to hold the lens when the lens exits the tubular member and expands into the eye. Holding the lens in this manner eases placement of the lens in the eye and alleviates the risks associated with uncontrolled unfolding of the lens or uncontrolled expulsion of the lens from the inserter into the eye. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an insertion device in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is a side elevational view of the plunger of the insertion device. 
     FIG. 3 is a top plan view of the plunger. 
     FIG. 4 is a cross sectional view taken along line  4 — 4  in FIG.  3 . 
     FIG. 5 is a partial top plan view of the tubular unit of the insertion device, including the staging area, with the cover removed and overturned, and the cannula omitted. 
     FIG. 6 is a cross sectional view taken along line  6 — 6  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 7 is a cross sectional view taken along line  7 — 7  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 8 is a cross sectional view taken along line  8 — 8  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 9 is a cross sectional view taken along line  9 — 9  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 10 is a cross sectional view taken along line  10 — 10  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 11 is a cross sectional view taken along line  11 — 11  in FIG. 5 with the cover placed onto the shelf segment. 
     FIG. 12 is a cross sectional view taken along line  12 — 12  in FIG.  13 . 
     FIG. 13 is a partial cross sectional view taken along line  13 — 13  in FIG. 1, with an IOL in the staging area. 
     FIG. 14 is an exploded view of FIG.  13 . 
     FIG. 15 is a partial top plan view of the tubular unit of the insertion device with an IOL in the staging area and with the cover and cannula omitted. 
     FIG. 16 is side elevational view of the distal tip of the plunger. 
     FIG. 17 is a front view of the distal end of the plunger. 
     FIG. 18 is a top plan view of the distal end of the plunger. 
     FIGS. 19-23 are each a schematic, partial cross sectional views taken along line  19 — 19  in FIG. 1, illustrating the movement of the plunger during insertion of the IOL into an eye. 
     FIG. 24 is an enlarged top plan view of the distal tip of the plunger holding an IOL. 
     FIG. 25 is a front end view of the insertion device with the plunger extended to the distal end of the cannula. 
     FIG. 26 is a cross sectional view of an eye illustrating the insertion and placement of an IOL. 
     FIG. 27 is a perspective view of an alternative construction of the distal end of the cannula. 
     FIG. 28 is a perspective view of a second alternative construction of the distal end of the cannula. 
     FIG. 29 is a perspective view of a third alternative construction of the distal end of the cannula. 
     FIG. 30 is a side elevational view of a fourth alternative construction of the distal end of the cannula. 
     FIG. 31 is a front elevational view of the fourth alternative construction of the distal end of the cannula. 
     FIG. 32 is a perspective view of an alternative embodiment of the cannula. 
     FIG. 33 is a perspective view of another alternative embodiment of the cannula. 
     FIG. 34 is a partial, longitudinal cross sectional view of an alternative embodiment of the tubular unit with the cover open and the cannula removed. 
     FIG. 35 is a cross sectional view taken along line  35 — 35  in FIG. 34, without the cover. 
     FIG. 36 is a plan view of the inside of the cover of the alternative tubular unit embodiment of FIG.  34 . 
     FIG. 37 is a plan view of the inside of the shelf segment of the alternative tubular unit embodiment of FIG.  34 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention pertains to a device  10  (FIG. 1) for inserting a flexible IOL  12  into an eye  14  of a patient (FIG.  26 ). The device comprises an outer tubular unit  16  and an inner plunger  18 . In one embodiment, tubular unit  16  is formed by a base member  20 , a cover  21  and a cannula  22  which are coupled together (FIGS. 1,  13  and  14 ). The components of device  10  may be composed of a plastic or metal material. For example, the components can be formed of polycarbonate or polypropylene. The plunger  18  and cannula  22  are preferably made of polypropylene. Nevertheless, a wide array of materials could be used. 
     Base member  20  is an elongate tubular member defining an inner passage  24  which is provided with a relatively large opening at proximal end  26  and an opening  27  of reduced size near, but spaced from, distal end  28  (FIGS. 1,  5 ,  13  and  14 ). A forwardly extending shelf segment  29  projects beyond opening  27  (FIGS. 5,  13  and  14 ). Base member  20  preferably has a generally oval cross sectional configuration, although other shapes could be used. 
     The inner passage  24  of base member  20  is adapted to movably receive therein plunger  18 . A longitudinal groove  34  is preferentially positioned along one of the side walls  32  defining inner passage  24  (FIG.  13 ). Groove  34  cooperates with an extending flange  35  projecting laterally from plunger  18  to ensure that the plunger is properly oriented when fed into base member  20 . Nevertheless, the groove construction could be replaced with a different structure for ensuring proper placement, such as forming at least a portion of inner passage  24  and plunger  18  with a D-shaped configuration. Near distal end  28 , base member  20  forms a narrowed neck  39 . Neck  39  defines distal opening  27  through which a portion of the plunger is passed to engage lens  12 . Converging guideways  41  are positioned along opposite interior sides of passage  24  leading up to neck  39  (FIGS. 5,  13  and  14 ). Guideways  41  function to ease the passage of the plunger through neck  39  and over the shelf segment  29  for engagement with lens  12 . 
     Shelf segment  29  is formed as an extension of roughly one half of the tubular base member  20 . Shelf segment  29  cooperates with cover  21  to define a staging area compartment  45  for holding lens  12  (FIGS. 5-11 and  13 - 14 ). Lens  12  preferably has a central optic and a pair of adjacent web or plate haptics  49   a ,  49   b  (FIGS.  14  and  24 ). Nevertheless, other lens constructions, such as a lens with loop haptics, could also be used. The interior side of shelf segment  29  is formed in part by a pair of ledges  51   a ,  51   b  adjacent neck  39 , a pair of recessed central flats  52   a ,  52   b , and a pair of ramps  53   a ,  53   b  spaced forwardly of flats  52   a ,  52   b  (FIGS. 5-11 and  13 - 14 ). Ledges  51   a ,  51   b  and ramps  53   a ,  53   b  are each formed with top surfaces  54   a ,  54   b ,  55   a ,  55   b  to engage and support the haptics  49   a , 49 b  of lens  12  in an initial unstressed position. Ramps  53   a ,  53   b  further include sloped surfaces  59   a ,  59   b  inclined to flats  52   a ,  52   b . Flats  52   a ,  52   b  are recessed relative to top surfaces  54   a ,  54   b ,  55   a ,  55   b  to define a pocket  60  into which is received optic  48 . 
     Cover  21  lies against shelf segment  29  to form staging area compartment  45  and enclose lens  12  in its initial unstressed position (FIG.  13 ). Cover  21  includes on its interior side recessed sections  61   a ,  61   b , the central portions of which lie opposed to the proximal half of flats  52   a ,  52   b . A pair of adjacent plateau segments  63   a ,  63   b  lie opposed to ledges  51   a ,  51   b  to define a gap  65  adapted to matingly receive and hold the proximal haptic  49   a . Haptic  49   a  is loosely received in gap  65  so that it can be easily pushed out of staging area  45  during the insertion process. Ledges  51   a ,  51   b , plateau segments  63   a ,  63   b , and ramps  53   a ,  53   b  collectively support lens  12  by haptics  49   a ,  49   b . In this initial position, optic  48  is held in suspension in pocket  60  so that the optic avoids contact with the interior walls of the staging area compartment  45 . 
     The lens  12  can be installed in compartment  45  at a manufacturing plant and shipped to the user in device  10  with or without cannula  22  assembled in place. In this manner, device  10  can conveniently serve also as a lens package. Since lens  12  is supported in a generally suspended and unstressed state, the lens can be stored for a substantial length of time, perhaps as long as 10 years. Although the cover could be fixed to base member  20 , it is designed for removal to enable inspection of the lens prior to its implantation in the eye. As shown in FIG. 14, cover  21  can be separable from base member  20 , and secured in place by a snap fit, tape or other securing means. Nevertheless, the cover may be hinged to cannula  22 , shelf segment  29 , or neck  39 . 
     Cover  21  includes projections  67   a ,  67   b  which mate with depressions  68   a ,  68   b  formed in shelf segment  29 . In addition, shelf segment  29  includes proximal outer walls  70   a ,  70   b  and distal outer walls  72   a ,  72   b . Proximal walls  70   a ,  70   b  abut the outer portions of recessed sections  61   a ,  61   b . Distal walls  72   a ,  72   b  likewise abut walls  73   a ,  73   b  of cover  21 . Distal walls  72   a ,  72   b  are preferably recessed relative to proximal walls  70   a ,  70   b  to enhance the mating fit of cover  21 . During shipping of the device, the cover may be held closed by cannula  22 , tape and/or other means to avoid inadvertent release of the lens. 
     Troughs  75   a ,  75   b  are formed in shelf segment  29  by extending the inner side wall surface  78  of compartment  45  downwardly between the outer distal sides of flats  52   a ,  52   b  and distal walls  72   a ,  72   b . Troughs  75   a ,  75   b  are provided to receive the opposite sides of lens  12  as they are folded or curled along inner side wall surface  78 . In the preferred embodiment, the troughs are deeper than flats  52   a ,  52   b.    
     Cover  21  further includes a central, generally planar surface  88  inclined to extend away from shelf segment  29 . A conically shaped portion  91  generally surrounding inclined surface  88  lies opposed to ramps  53   a ,  53   b . These surfaces  88 ,  91  in cooperation with ramps  53   a ,  53   b  initiate the desired folding of the lens to its compressed state. 
     Cannula  22  is an elongate tubular member with an open proximal end  93  and an opposite open distal end  95  (FIGS.  1  and  12 - 14 ). Cannula  22  is preferably subdivided into three graduated sections  97 - 99 . The proximal section  97  has a generally rectangular configuration and defines an inner cavity  101  sized to matingly receive the assembled shelf segment  29  and cover  21 . Section  97  extends from distal end  28  to neck  39  of base member  20  and functions to hold cover  21  against shelf segment  29 . An axial channel  102  is defined along one wall of cavity  101  to matingly receive ridge  103  extending up from cover  21 . A hole  104  defined at the proximal end  93  of cannula  22  cooperates with a biased lock  106  on base member  20  to secure the cannula in place. 
     The medial section  98  of cannula  22  is significantly smaller than proximal section  97  so that a rim  110  is defined therebetween. Rim  110  acts as a shoulder in abutment with the aligned distal ends  28 ,  111  of base member  20  and cover  21 . The inner wall of medial section  98  converges to define a funnel shaped passage  112 . The funnel portion  112  preferably has an oval cross section, although other shapes could be used. This funnel section causes the lens to become substantially curled and compressed for entry into the eye. 
     The final, distal section  99  of cannula  22  is a long, narrow tube which defines an inner lumen  114 . Distal section  99  is to be inserted through the narrow incision made in the eye. As with medial section  98 , distal section  99  and lumen  114  preferably have an oval cross sectional shape. Of course, other shapes could be utilized if desired. To facilitate manufacturing and further compression of lens  12 , lumen  114  is formed to taper slightly as it extends forward. Distal end  95  of cannula  22  is beveled to ease the insertion of the cannula into the incision and to assist in facilitating a gradual expansion of the lens as it exits from lumen  114 . 
     The distal section of the cannula may be provided with a wide variety of cross section configurations. As examples only, the cannula may be shaped with a clover-type tip  22 A, a collapsible bag type tip  22 B, or a wave-type tip  22 C (FIGS.  27 - 29 ). These configured tips enhance the strength of the tip and thus permit a narrower construction to be used. The cannula tip may also be formed with a collet-like construction  22 D. In this embodiment, the tip includes four separable leaves  23  which are expanded as the lens is pushed into the eye. The leaves  23  are biased to naturally close after the lens is placed into the eye and the plunger retracted. 
     In the preferred embodiment, cover  221  is hinged to base member  220  of tubular unit  216  (FIGS.  34 - 37 ). The inside configuration of cover  221  is essentially the same as the inside configuration of cover  21 , except that projections  267  are interconnected with plateau segments  263  by segments  264 . Similarly, the inside configuration of shelf segment  229  is essentially the same as the inside configuration of shelf segment  29 . As can be seen in FIG. 37, shelf segment  229  includes a corresponding interconnection of depressions  268  with ledges  251 . Also, the central channel  224  of shelf segment  229 , which accommodates passage of the plunger, is enlarged across its middle section. These modifications do not affect the operation of compressing and inserting the lens into an eye. 
     Also, as an optional feature, a hole  246  may be provided through shelf segment  229 . The hole can be used to insert a viscoelastic material in embodiments wherein the cover is fixed to the shelf segment or otherwise not opened by the surgeon. 
     Cover  221  further includes a pair of rearwardly extending arms  265 , which are provided with knobs  266  on their free ends. Arms  265  are provided to pivotally connect the cover to neck portion  239 . Specifically, neck portion  239  includes a pair of sockets  242 . Sockets  242  are formed to include substantially square shaped openings  243  (although other shapes could also be used) for receiving knobs  266 , and channel portions  244  for receiving arms  265  when cover  221  is moved to its closed position (not shown). Recesses  245  are formed on the outside walls of openings  243  (FIG. 35) to receive the outward projection of knobs  266 . Receipt of knobs  266  in recesses  245  functions to retain the cover  221  to base member  220 . 
     In an alternative embodiment, cannula  160  includes a cover  162  hinged for movement between an open position and a closed position (FIG.  32 ). Cannula  160  has essentially the same construction as cannula  22 , except for the incorporation of cover  162  in proximal section  164 . Cover  162  has substantially the same construction as cover  21 , including the same internal configuration for supporting and compressing the lens. 
     Proximal section  164  of cannula  160  comprises a base  166  and a cover  162 . The base includes a bottom wall  168  and a pair of side walls  170  which extend upward only as high as shelf segment  29 . The internal surfaces of bottom wall  168  and side walls  170  are shaped to matingly receive the external surface of shelf segment  29 . A pair of upstanding flanges  172  are provided at proximal end  174  of base  166  to engage neck  39  and provide ample support for the cannula. A hole  176  is provided to cooperate with a protrusion (not shown) on shelf segment  29  in locking the cannula to the base member  20 . 
     Cover  162  is movably connected to base  166  by a living hinge  178 , although other hinge constructions could also be used. The cover is pivotally movable to an open position to permit inspection of the lens, and to a closed position for inserting the lens into a patient&#39;s eye. The lower edges of side walls  180  of the cover are formed to snap into a locking engagement with base  166  by any conventional construction (not shown); nevertheless, other fastening arrangements could be used. The internal configuration of cover  162  aligns with the internal configuration of shelf segment  29  in the same way as cover  21 . Cover  162  further includes a proximal tab  182  which projects between flanges  172  to engage locking protrusion  106  in hole  184 . 
     As an alternative construction, side walls  170   a  of cannula  160   a  extend the entire depth of proximal section  164   a , and cover  162   a  is provided with a flattened construction (FIG.  33 ). The internal side of cover  162   a  has the same configuration and relative positioning to shelf segment  29  as does the above-described cover  21 . The edges  180   a  of cover  162   a  are preferably constructed to snap into locking engagement with edges  181   b  of side walls  170   a . Nonetheless, other fastening arrangements could be used. 
     Preferably, cannula  162 ,  162   a  is composed of a polypropylene or other thermoplastic material. A disposable cover (not shown), can be used to ship and store the IOL in device  10 . The disposable cover preferably has the same general size and shape as cover  162 ,  162   a  to enable it to snap into engagement with base  166 ,  166   a . The disposable cover can have a wide variety of internal constructions so long as the IOL is adequately supported (as described above with respect to the other covers) and protected. 
     Plunger  18  is an elongate member which is adapted to move through the inner passage  115  defined by tubular unit  16  (FIGS.  1  and  13 ). The plunger comprises a main body  116  preferably shaped with a cross shaped cross section (FIGS.  2 - 3 ). As discussed above, one flange  35  of the body is received into groove  34  to ensure proper placement of the plunger. A flat thumb pad  119  is provided on the proximal end of body  116  for manual operation of the device. Other constructions, however, may be provided to effect advancement of plunger  18  through tubular unit  16 . The forward end of body  116  includes a pair of spaced apart O-rings  120   a ,  120   b . The O-rings provide a level of resistance to enable a more controlled manual operation of the plunger. The O-rings further help to prevent the plunger from inadvertent movement when the surgeon manipulates device  10  during the surgical procedure. Other constructions, such as friction fit flanges, could be used in place of the O-ring. 
     A slender rod  122  projects forwardly beyond the main body  116  of plunger  18 . The rod is intended to pass through staging area  45 , funnel  112  and lumen  114 . In order to provide sufficient clearance for rod  122 , shelf segment  29  defines a channel  124  and cover  21  includes a relief  125  (FIGS. 5-11 and  13 - 14 ). Relief  125  only extends partway across cover  21  because surface  88  diverges away from the interior side of shelf segment  29  and thus provides sufficient clearance for rod  122 . While rod  122  could have a wide range of shapes, it preferably has a circular or a slight ellipsoid shape adapted to pass through the distal end  95  of cannula  22  (FIG.  25 ). 
     The distal tip  128  of rod  122  is preferably bifurcated to define a pair of prongs  131   a ,  131   b  separated by a slot  132  (FIGS. 2-3,  16 - 18 ,  24  and  25 ). The slot is shaped to receive and hold proximal haptic  49   a  and optic  48  of lens  12 . The ends  135   a ,  135   b  of prongs  131   a ,  131   b  are chamfered to form a pair of walls  137   a ,  137   b  which collectively form a generally V-shaped configuration. Depending on the sturdiness of the proximal haptic, walls  137   a ,  137   b  may or may not engage the proximal end of the optic  48 . Prongs  131   a ,  131   b  are preferably identical to one another. Nevertheless, one prong  131   a  can be made narrower than the other prong  131   b  to allow extra space for the lens  12  to curl and compress during its passage through lumen  114  and into the patient&#39;s eye. Under ordinary circumstances, however, the extra space is not needed. 
     The distal tip of plunger  18  may alternatively be formed with other structural configurations which would hold the lens when the lens is pushed out of the cannula. For example, when implanting an IOL with loop shaped haptics, the plunger may be formed with a closed vertical slot (not shown) along the top of rod  122  in lieu of the open horizontal slot  132 . In this arrangement, the lens would be positioned in staging area  45  with the haptics extending from points along the sides of the tubular unit. The haptic, which curls rearwardly would be inserted into the vertical slot when the lens is mounted in the staging area. To avoid inadvertent release of the haptic during shipping and storage, the plunger could be secured in a fixed position through the use of a latch, tape, or other securing means. In any event, the plunger would engage the optic portion of the lens with its distal tip, formed for example with only inclined surfaces like  137   a ,  137   b . When the lens is initially extended beyond cannula  22 , the noted haptic would remain entrapped in the slot which would not yet be exposed outside of cannula  22 . When release of the lens is desired, the plunger can be pushed slightly farther to expose the vertical slot and free the trapped haptic. The plunger can then be retracted into the tubular unit  16  while the lens remains in the eye. 
     In one embodiment, a pair of resilient spring elements  140   a ,  140   b  extends laterally from rod  122  near the rod&#39;s proximal end (FIGS.  2 - 3 ). The spring elements function to press against guideways  41  when the free end  128  of rod  122  extends beyond cannula  22 . This engagement with guideways  41  forces spring elements  140   a ,  140   b  to be pushed backward, and thereby create a biasing force to pull the plunger rearward into tubular unit  16 . In the preferred construction, the spring elements (not shown) would extend forwardly, generally parallel with rod  122 , from the front end of the main body. In this arrangement, the spring elements would be designed to curl inward upon engagement with guideways  141 . Additionally, a coil spring (not shown) may be secured around the plunger/rod to provide the desired biasing force. Of course, other spring arrangements could also be used. The spring may also be omitted and the plunger retracted manually by the surgeon. 
     Once the lens has been inspected, device  10  can be assembled. A viscoelastic material, typically used for such surgical procedures, is placed in the cannula  22 , typically prior to attachment of the cannula  22  to the assembly, as a lubricant for the insertion process. Once device  10  is assembled, the surgeon inserts the distal end of cannula  22  into the incision  142  in the eye  14 . The surgeon then grasps lateral flanges  141  and pushes on pad  119  to move plunger  18  in a continuous forward motion. (FIG.  1 ). The continuous movement of rod  122  through tubular unit  16  engages lens  12  through its distal end  128  (FIG.  24 ). The proximal haptic  49   a  and possibly a portion of optic  48  are received into and held by slot  132 , between walls  137   a ,  137   b . The lens is then pushed forwardly by plunger  18  so that the distal side of optic  48  is shifted transversely toward cover  21  by sloped surfaces  59   a ,  59   b  of ramps  53   a ,  53   b ; that is, sloped surfaces  59   a ,  59   b  guide the central portion of optic  48  away from flats  52   a ,  52   b  (FIGS.  19  and  20 ). Inclined surface  88  and conical surface  91  provide ample clearance for this motion of the lens. As the center of the lens is shifted to move over ramps  53   a ,  53   b , the sides of the lens are forced generally in the direction opposite to the ramps, by the inner wall surface  78  of cover  21 . Specifically, the conical surface  91  in cover  21  causes lens  12  to curl into troughs  75   a ,  75   b . Continued advancement of lens  12  through the tapering passage of tubular unit  16  causes continued curling and compression of the lens. 
     The lens continues its forward motion until plunger  18  pushes lens  12  beyond cannula  22 . In the preferred construction, plunger  18  is pushed manually forward in a controlled manner, although other means, such as an electric motor or pneumatic drive, may be used. 
     The leading haptic  49   b  is fed into the distal cul-de-sac  152  of the capsular bag  154 . When lens  12  exits from cannula  22 , it expands to its full unstressed state (FIGS. 22,  24  and  26 ). The lens, however, remains held in the slot  132  of plunger  18 . Retention of the lens by the plunger reduces the risk of the lens expelling in an uncontrolled manner from the cannula and damaging the interior of the eye. Retaining the lens with the plunger also provides increased control in placing the lens in the eye. To release the lens, the plunger is retracted into tubular unit  16  so that the lens is pushed from slot  132  by distal end  95  of cannula  22  (FIG.  23 ). The retraction of plunger  18  is preferably performed automatically by biased spring elements  140   a ,  140   b  when pressure is released from thumb pad  119 . A further implement, or perhaps device  10  itself, will typically be required to properly position the proximal haptic  49   a  into capsular bag  154 . 
     The above-discussion concerns the preferred embodiments of the present invention. Various other embodiments as well as many changes and alterations may be made without departing from the spirit and broader aspects of the invention as described in the claims. For example, although the preferred embodiments concern the insertion of a flexible IOL into the eye, the invention is not so limited. The teachings of the present invention are applicable to the insertion of flexible membranes generally, including synthetic membranes, biopolymer membranes, and natural body tissues.