the present invention is predicated upon the provision of an iol delivery device that includes a delivery cartridge and a plunger having a multi - part plunger delivery tip . the delivery tip includes a relatively compressible member , a relatively incompressible member and an internal member . the delivery cartridge defines a lumen having a cross - sectional area that becomes progressively smaller as the cross - sectional area is taken closer to a nozzle of the cartridge . during delivery of an iol , the compressible member of the plunger tip member undergoes substantial compression as the plunger tip travels along the progressively smaller cross - sectional area . during such compression , the relatively incompressible member shields the internal member from being substantially compressed by or lodged within the external member . the internal member of the plunger tip is then released from the relatively compressible member , the relatively incompressible member or both and completes the delivery of the iol . with reference to fig1 - 3 , there is illustrated an exemplary iol delivery device 10 according to the present invention . the device 10 includes a delivery cartridge 12 having an internal surface 14 defining a lumen 16 extending along the cartridge 12 . the illustrated lumen 16 extends along a length ( l ) of the cartridge 12 . as can be seen , a cross sectional area 24 of the lumen 16 becomes progressively smaller along at least a portion of the lumen 16 as the cross - sectional area 24 is taken at locations progressively closer to a nozzle ( not shown ) of the cartridge 12 . the device 10 includes a plunger 30 having an elongated member 32 and a plunger tip 32 at a distal end of the elongated member 32 . the plunger tip 32 is defined by an internal member 34 , an external relatively compressible member 36 and an intermediate relatively incompressible member 40 . in the embodiment shown , the internal member 34 is a portion of the elongated member 32 . also as shown , the internal member 34 is integrally formed of the same material and as a singular part with the elongated member 33 . however , it is contemplated that the internal member 34 may be a separate part formed of a separate material and attached to the elongated member 32 directly or through one or more other components . the internal member 34 and hence the elongated member 33 may be formed of variety of materials such as metals or polymeric materials . in a preferred embodiment , the internal member is formed of a relatively rigid polymeric material . exemplary potential polymeric materials include , without limitation , polystyrenes , polypropylenes , polycarbonates , combinations thereof or the like . it is also contemplated that the internal member 34 may itself include its own tip ( not shown ), which would typically be formed of material that is softer or more compressible than the material of the internal member 34 . the intermediate member 40 can also be formed of a variety of materials such as metal or polymeric materials as long as the material is relatively rigid as compared to the material that forms the external member 36 . the material forming the intermediate member 40 is preferably a polymeric material and , like the internal member 34 , suitable materials can include , without limitation , polystyrenes , polypropylenes , polycarbonates , polyetherimides , polyethylether ketones , polyether ether ketones , styrenics ( e . g ., acrylonitrile butadiene styrene ), combinations thereof or the like . preferably , the material forming the intermediate member 40 has a an elongation at break that is no greater than 300 %, more typically no greater than 100 %, still more typically no greater than 50 %. elongation at break , as used herein , can be determined in accordance with astm d412 . as suggested , the material forming the external member 36 is relatively soft and compressible relative to the material forming the intermediate member 40 . the material forming the external member is also preferably a polymeric material and will typically be entirely or substantially entirely an elastomer ( e . g ., a thermoset or thermoplastic elastomer ). examples of suitable materials include , without limitation , polyurethanes , butadiene rubbers , styrenic block copolymers , polyolefin blends such as ethylene propylene diene monomer elastomers , thermoplastic copolyesters , thermoplastic polyamides , polyurethanes , combinations thereof or the like . preferably , the material forming the external member 36 has an elongation at break that is at least 350 %, more typically at least 800 % and still more typically at least 1500 %. it is also preferable that the material of the external member 36 has an elongation at break that is at least 2 ×, more typically at least 4 × and still more typically at least 8 × an elongation at break of the material forming the intermediate member 40 . as used herein , 2 ×, 4 × and 8 × respectively means two times , four times and eight times and as applied to an elongations of 100 % would respectively mean 200 %, 400 % and 800 %. again with reference to fig1 - 3 , the illustrated exemplary external member 36 is annular in shape and extends about and / or substantially or entirely surrounds and encircles the intermediate member 40 , the internal member 34 or both . the illustrated exemplary intermediate member 40 is also annular in shape and extends about and / or substantially or entirely surrounds and encircles the internal member 34 . of course , the skilled artisan will be able to contemplate other arrangements of these members within the scope of the present invention . the internal member 34 , the external member 36 , the intermediate member 40 or a combination thereof typically includes one or more retention features 50 for releasably maintaining the intermediate member 40 , the external member 36 or both in the same position relative to the internal member 34 . in the illustrated embodiment the retention features 50 include a protrusion extending from the intermediate member 40 and a cavity disposed in the internal member 34 , the cavity receiving the protrusion for maintaining the aforementioned relative position . of course , the skilled artisan will be able to contemplate multiple other retention feature configurations within the scope of the present invention . during delivery of an iol , an individual or machine pushes the plunger 30 causing the plunger tip 32 to travel along the lumen 16 . at some point , the plunger tip 32 travels along at least the portion of the lumen 16 having the progressively smaller cross - sectional area 24 . in turn , this causes the external member 36 to compress a substantial amount while the intermediate member 40 remains substantially non - compressed . as used herein , a substantial amount of compression includes a movement of an outer surface of the external member to a distance at least 10 %, more typically at least 20 % and even more typically at least 30 % closer to the intermediate member 40 . for exemplary purposes , 10 % closer means 10 % of the original distance or , more particularly , for a surface that is 10 millimeters ( mm ) away , 10 % closer means 9 mm away . upon achieving the substantial amount of compression of the external member 36 , the retention features 50 release the internal member 34 from the intermediate member 40 . the internal member 34 then extends out away from the external member 36 , the intermediate member 40 or both and continues to push the iol to continue the delivery of the iol typically all of the way out through the nozzle of the cartridge 12 . in the embodiment shown , the external member 36 is gradually compressed until enough force is built up against the retention features 50 , causing the retention features 50 to release the internal member 34 from the intermediate and external members 40 , 36 . however , it is to be understood that the cartridge 12 could include a stop ( not shown ) that the external member 36 or intermediate member 40 or both contact thereby causing stoppage of travel of the external member 36 and intermediate member 40 and release of the internal member 34 after substantial compression of the external member 36 . for example , and without limitation , the internal lumen 16 could include a portion of rapidly decreasing cross - sectional area or the cartridge 12 could include a protrusion that would quickly stop travel of the external member 36 and intermediate member 40 . advantageously , the plunger tip of the present invention provides a relatively large surface area for pushing an iol prior to release of the internal member . moreover , that surface area conforms to the lumen through which it travels at least until the internal member releases from the intermediate and external members . upon such release , the iol is sufficiently folded and / or compressed such that the internal member provides sufficient surface area to continue the advancement of the iol . in this manner , the iol can be reliably delivered without frictional and / or compressive forces generated by the tip becoming undesirably high . it is contemplated that multiple different iol delivery systems can be modified to include the lumen and plunger of the present invention . example of such systems are disclosed in , without limitation , u . s . pat . nos . 4 , 615 , 701 ; 6 , 398 , 789 ; 6 , 592 , 591 ; 7 , 033 , 366 ; 7 , 156 , 852 ; and 7 , 156 , 854 , all of which are incorporated herein by reference for all purposes . the entire contents of all cited references in this disclosure are specifically incorporated herein by reference . further , when an amount , concentration , or other value or parameter is given as either a range , preferred range , or a list of upper preferable values and lower preferable values , this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value , regardless of whether ranges are separately disclosed . where a range of numerical values is recited herein , unless otherwise stated , the range is intended to include the endpoints thereof , and all integers and fractions within the range . it is not intended that the scope of the invention be limited to the specific values recited when defining a range . other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein . it is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof .
the present invention is directed to the provision of an intraocular lens delivery device having a plunger with a multi - part plunger tip . the plunger tip includes a first part and a second part wherein the first part releases from the second part during travel of the plunger through the body of a delivery cartridge .