fig1 illustrates an iol insertion apparatus , shown generally as 10 , in accordance with the present invention . the apparatus 10 comprises a distal housing 12 , a proximal housing 14 and a folding cartridge 16 . distal housing 12 is operatively coupled to proximal housing 14 . distal housing 12 includes a through opening 20 through which the folding cartridge 16 can be placed . distal housing 12 includes a forward opening 22 through which the injection tube 24 of folding cartridge 16 extends distally . proximal housing 14 includes two oppositely disposed finger supports 26 which extend outwardly from the outer peripheral surface 28 of the proximal housing . apparatus 10 also includes a plunger rod 30 which includes an enlarged proximal end 32 effective to push plunger rod 30 through proximal housing 14 , as will be discussed hereinafter . before proceeding to describe the operation of insertion apparatus 10 , a brief description of the operation of folding cartridge 16 is provided . with reference to fig2 the iol is to be placed in the eye 40 into an area formerly occupied by the natural lens of the eye . with the iol in its folded position within apparatus 10 , as described below , injection tube 24 is ready for insertion through an incision 42 in the sclera 44 of eye 40 . capsular bag 46 protects the posterior segment of the eye 40 and as one of the eye &# 39 ; s constituent parts which is not injured by the insertion of the iol with the injection tube 24 inserted within the eye 40 and the distal end properly positioned , the surgeon advances plunger rod 30 by manually pushing the plunger rod 30 relative to proximal housing 14 . this action moves iol distally into injection tube 24 . if needed , iol can be repositioned in the eye by a small , bent needle or similar tool inserted into the same position . fig2 shows the sclera 44 having an incision through which the distal end portion of the injection tube 24 is passed . alternately , the incision may be made through the cornea . injection tube 24 preferably has a sufficiently small cross - section to pass into the eye 40 through an incision of about 3 . 5 mm or about 3 . 0 mm in the sclera 44 . once iol is properly positioned in eye 40 , and apparatus 10 is withdrawn from the eye , the incision in the sclera may be closed , for example , using conventional techniques . after use , folding cartridge 16 , which is made of a polymeric material , such as polypropylene , preferably is disposed of . remaining portions of apparatus 10 , which preferably are made of metal , such as surgical grade stainless steel , may be reused after sterilization and disinfection . any suitable material or materials of construction may be employed in the various components of the apparatus in accordance with the present invention . fig3 and 4 illustrate an exemplary cartridge 50 of the present invention to be used as explained above with reference to the cartridge 16 of fig1 . that is , the combination of the cartridge 50 and intraocular lens ( iol ) is coupled with an insertion apparatus 10 and positioned such that a distal tip of the cartridge is within the eye for delivery of the lens . it will be understood that the insertion apparatus 10 as described above is exemplary only , and the cartridge of the present invention may be utilized with other such apparatus that include a plunger rod for displacing the iol from within the cartridge . a common problem with such devices is obtaining reliable engagement between the plunger rod and iol , and the present invention provides an improved cartridge 50 for this purpose . the cartridge 50 includes a distal injection tube 52 , and a proximal loading end 54 defining a load chamber 56 therewithin . the injection tube 52 defines an elongate injection lumen 58 that is open to the load chamber 56 and provides a narrowing channel through which an iol 60 passes . that is , the iol 60 passes in the distal direction from its illustrated position within the load chamber 56 through the narrowing injection lumen 58 and out of a distal mouth 62 of the injection tube 52 . as will be more fully explained below , a plunger rod extends entirely through the elongated lumen of the cartridge 50 and pushes the iol 60 therethrough . the cartridge 50 is desirably of the type that has relatively hinged portions for folding the iol 60 therewithin . specifically , the loading end 54 of the iol 60 is defined by a pair of arcuate walls 70 a , 70 b pivotally connected at a living hinge 72 . with reference to fig3 and for orientation purposes only , the living hinge 72 is disposed axially along a lower generatrix of the loading end 54 , with the arcuate walls 70 a , 70 b defining a stepped tubular inner surface and a generally cylindrical load chamber 56 therewithin . the upper ends of the arcuate walls 70 a contact each other in a closed condition of the loading end 54 , each continuing radially upward in a respective folding wing 74 a , 74 b . in a preferred embodiment , one of arcuate walls 70 a , 70 b is fixed with respect to the injection tube 52 , while the other wall pivots with respect to the first wall and injection tube . in the illustrated embodiment , for example , the arcuate wall 70 a shown on the left in fig3 pivots about the hinge 72 away from the right - hand arcuate wall 70 b in the direction of arrow 75 . although not shown , the arcuate wall 70 a pivots about 180 degrees to open up the loading end 54 and permit placement of the iol 60 therewithin . subsequently , the arcuate wall 70 a is folded in the opposite direction into the configuration shown in fig3 which action also folds the iol 60 substantially into a tube ; the tube defining an inner lens face 76 a and an outer lens face 76 b . a rib 77 formed by a radially inward extension of one of the folding wings 74 a , 74 b may be provided to help retain the iol 60 in a predetermined position during the folding operation . the cartridge 50 of the present invention has a stepped tubular configuration as shown wherein one of the arcuate walls 70 a , 70 b has a larger radius of curvature than the other . in a preferred embodiment , the upper end of both of the walls 70 a , 70 b meet at approximately the same location , but the lower ends are misaligned . therefore , the left side arcuate wall 70 a may have a larger radius of curvature than the right side wall 70 b such that the lower end of the left wall is offset below the lower end of the right wall , with a radial step 78 formed therebetween . the curvature of the left side wall 70 a is centered about an axis 80 a , while the right side wall 70 b is centered about a different axis 80 b , with both of the axes generally being positioned along a vertical midplane of the loading end 54 , as oriented in fig3 . the step 78 is desirably radially disposed with respect to both arcuate walls 70 a , 70 b , with the hinge 72 being located at a lower end thereof . in this regard , the hinge 72 is desirably created via removal of material from a step 78 , and from the lower end of the left side arcuate wall 70 a , to form a notch 82 . in a preferred embodiment , the cartridge 50 is molded from a suitable polymer . with respect to the contour of the load chamber 56 , the step 78 creates a shoulder 84 between the inner surfaces of the arcuate walls 70 a , 70 b . the shoulder 84 is desirably rounded to prevent damage to the iol 60 , and projects into the load chamber 56 so as to deform the iol into a multi - curvate ( i . e ., complex curve ) configuration that facilitates engagement thereof by a plunger rod . with reference still to fig3 the iol 60 includes a pair of edges 90 a , 90 b located at the upper end of the load chamber 56 on either side of the rib 77 , and a midsection 92 located at the lower end of the load chamber . most iols 60 are somewhat thicker in the midsection 92 than the edges 90 a , 90 b . furthermore , the iol 60 is flexible to enable folding , and thus conforms to the contour of the load chamber 56 . therefore , the iol 60 closely conforms to the inner arcuate surfaces of the walls 70 a , 70 b , and has a first majority curvature centered within the load chamber 56 . at the lower end , the shoulder 84 causes the midsection 92 of the iol 60 to form a second curvature in the opposite direction , creating a point of inflection such that the midsection bows toward the axis of the load chamber 56 . stated another way , the second curvature at the midsection 92 is centered outward of the outer lens face 76 a ( fig3 ). a separation space 94 may be created between the midsection 92 and the arcuate wall 70 b because of this change in curvature and the resiliency of the material . importantly , the midsection 92 follows the left side arcuate wall 70 a below the level of the shoulder 84 before curving upward and over the shoulder . of course , the particular contour of the iol 60 depends on the material , with silicone - based iols more closely conforming to the shape of the inner wall of the load chamber 56 than acrylic - based iols . the section line 4 — 4 in fig3 extends between the folding wings 74 a , 74 b and is offset in the middle of the load chamber 56 to avoid passing through the step 78 so that the elevation of the iol 60 below the shoulder 84 is seen in cross - section in fig4 . additionally , the section line 4 — 4 angles through the notch 82 so as to better illustrate the living hinge 72 . now with reference to fig5 - 7 , interaction of the cartridge 50 with a plunger rod 100 of an insertion apparatus ( such as the apparatus 10 in fig1 ) is shown . the plunger rod 100 may take a variety of forms , but is desirably of a type that has an iol engaging end 102 defined by a pair of lips 104 a , 104 b spaced apart to define a recess 106 therebetween . although not shown , the plunger rod 100 has a thickness and a length that permits it to extend entirely through the load chamber 56 and injection lumen 58 of the cartridge 50 . in use , the plunger rod 100 engages the iol 60 and pushes it through the cartridge 50 and from the mouth 62 into the eye of a patient . the plunger rod 100 is rotationally oriented with respect to the cartridge 50 as shown in the figures . that is , at least until engagement with the iol 60 , lips 104 a , 104 b are vertically spaced apart with respect to the aforementioned orientation of the cartridge 50 . fig5 illustrates the direction 108 of advancement of the plunger rod 100 into the load chamber 56 , which is only partially shown . additionally , the plunger rod 100 is desirably centered with respect to the load chamber 56 , and thus passes directly over the shoulder 84 . as seen in fig6 a , the lower lip 104 b is aligned to pass closely over the arcuate wall 70 b and shoulder 84 . as the plunger rod 100 continues distally , as seen in fig6 b , the engaging head 102 eventually contacts the iol 60 as shown . fig7 illustrates the positioning of the lips 104 a , 104 b with respect to the midsection 92 of the iol 60 . the projection of lower lip 104 b extends across the midsection 92 from the outer lens face 76 a to the inner lens face 76 b ( see fig3 ). because of the curvature of the midsection 92 caused by its conformance with the shoulder 84 , the lower lip 104 b crosses substantially transversely to the thickness of the midsection to insure engagement therewith . in contrast , if the load chamber 56 was defined by a purely cylindrical inner surface , the lower lip 104 b would be generally aligned parallel to the midsection 92 , and would potentially ride over the midsection and fail to engage it . the present invention insures that the lower lip 104 b extends completely across the thickness of the midsection 92 which prevents such engagement failure . although not shown , as the plunger rod 100 continues in the distal direction from its position shown in fig6 b , the iol 60 will deform somewhat and be pushed along through the load chamber 56 . depending on the material of the iol , the midsection 92 may eventually be captured within the recess 106 between the lips 104 a , 104 b . even without such capture , the lower lip 104 b is positioned so that it cannot ride over the midsection 92 by virtue of the stepped contour of the iol 60 . while this invention has been described with respect of various specific examples and embodiments , it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims .
an intraocular lens insertion apparatus including a cartridge with an iol - receiving chamber , a handpiece into which the cartridge is loaded , and a plunger rod that extends through a lumen in the cartridge to reliably engage the iol therein . the chamber is stepped in one section to cause the iol positioned therein to assume a complex curve . a lip or projection on the plunger rod is aligned with the complex curve and intersects the iol to reliably engage the iol across its thickness . the cartridge may be a folding type with a pair of arcuate walls and extension wings joined at a living hinge . the stepped section of the chamber may coincide with the location of the hinge .