in accordance with the principles of the present invention , an intraocular lens is provided having a haptic portion and a light - transmissive optic portion . the optic portion contains one or more fluid - mediated pistons arranged to apply a deflecting force on an anterior or posterior element of the lens to provide accommodation of the lens . as used herein , the lens is fully “ accommodated ” when it assumes its most highly convex shape , and fully “ unaccommodated ” when it assumes its most flattened , ellipsoidal state . the lens of the present invention is capable of dynamically assuming any desired degree of accommodation between the fully accommodated state and fully unaccommodated state responsive to the ciliary process . forces applied to a transducer disposed in the haptic portion by the ciliary process are communicated to one or more lens pistons that control deflection of an anterior or posterior element of the lens , resulting in a larger dynamic range of accommodation than heretofore is believed to have been available . the lens piston and surrounding fluids all are index - matched to prevent the occurrence of optical aberrations throughout the range of motion of the lens piston . in accordance with another aspect of the present invention , the transducer may include one or more haptic pistons that provide a volumetric mechanical advantage with respect to forces applied by the ciliary process to the lens piston . referring to fig1 and 2 , the structure and operation of a human eye are first described as context for the present invention . eye 10 includes cornea 11 , iris 12 , ciliary muscles 13 , ligament fibers or zonules 14 , capsule 15 , lens 16 and retina 17 . natural lens 16 is composed of viscous , gelatinous transparent fibers , arranged in an “ onion - like ” layered structure , and is disposed in transparent elastic capsule 15 . capsule 15 is joined by zonules 14 around its circumference to ciliary muscles 13 , which are in turn attached to the inner surface of eye 10 . vitreous 18 is a thick , transparent substance that fills the center of eye 10 . isolated from the eye , the relaxed capsule and lens takes on a spherical shape . however , when suspended within the eye by zonules 14 , capsule 15 moves between a moderately convex shape ( when the ciliary muscles are relaxed ) to a highly convex shape ( when the ciliary muscles are contracted ). as depicted in fig2 a , when ciliary muscles 13 relax , capsule 15 and lens 16 are pulled about the circumference , thereby flattening the lens . as depicted in fig2 b , when ciliary muscles 13 contract , capsule 15 and lens 16 relax and become thicker . this allows the lens and capsule to assume a more spherical shape , thus increasing the diopter power of the lens . accommodating lenses currently nearing commercialization , such as the crystalens device under development by eyeonics , inc ., aliso viejo , calif ., typically involve converting diametral movements of the ciliary muscle into forward and backward movement of an optic portion of the iol relative to the retina . this approach is thought to be required because , following extraction of a cataract - effected lens , the capsule is very loose , and the zonules that couple the capsule to the ciliary muscles are no longer in tension . devices such as the crystalens thus do not employ the natural accommodation mechanisms described above , but instead rely directly on radially inward compressive forces applied by the ciliary muscle to the haptics of the iol . by contrast , according to one aspect of the present invention , an intraocular lens is designed to engage capsule 15 and to transition between the accommodated and unaccommodated states responsive to forces applied to capsule 15 by ciliary muscle 13 and zonules 14 , thereby more closely mimicking operation of the natural eye . alternatively , the haptic portion may be disposed directly in contact with the ciliary muscle . referring to fig3 a and 3b , an exemplary embodiment of an intraocular lens constructed in accordance with the principles of the present invention is described . iol 20 comprises optic portion 21 and haptic portion 22 . optic portion 21 is constructed of light transmissive materials , while haptic portion 22 is disposed at the periphery of the optic portion and does not participate in focusing light on the retina of the eye . optic portion 21 comprises anterior lens element 23 , actuator layer 24 including lens piston 25 , substrate 26 and posterior lens element 27 , all made of light - transmissive materials , such as silicone or acrylic polymers or other biocompatible materials as are known in the art of intraocular lenses . haptic portion 22 illustratively comprises arms 28 and 29 extending from substrate 26 , although other haptic configurations may be employed . each of arms 28 and 29 terminates in transducer 30 . transducers 30 preferably each comprise a haptic piston including force - concentrating fin 31 , diaphragm 32 and reservoir 33 . reservoirs 33 are coupled in fluid communication with the interior of lens piston 25 via channels 34 that extend from the reservoirs to well 35 disposed beneath lens piston 25 . in fig3 b , transducers 30 are in an undeformed state in which force - concentrating fins 31 apply a maximum deflection to diaphragms 32 , thereby fully deflecting end wall 41 and driving anterior element 23 to the fully accommodated position . this corresponds to a fully - contracted state of the ciliary muscles , as described herein below . actuator layer 24 is disposed in recess 36 of substrate 26 , and preferably comprises a sturdy elastomeric material . actuator layer 24 isolates the fluid in channels 34 , well 35 and the interior of lens piston 25 from the fluid disposed in the space 37 between anterior lens element 23 and actuator layer 24 . fluids 38 and 39 disposed , respectively , within channels 34 and space 37 , preferably comprise silicone or acrylic oils and are selected to have refractive indices that match the materials of anterior lens element 23 , actuator layer 24 and substrate 26 . in a preferred embodiment , lens piston 25 includes substantially nondeformable cylindrical side wall 40 coupled to expandable end wall 41 . end wall 41 is configured to deflect outward responsive to pressure applied within sidewall 40 by fluid movement from the haptic portion . end wall 41 contacts the interior surface of anterior lens element 23 , so that deflection of end wall 41 of the lens piston causes a corresponding deflection of anterior lens surface 23 . such deflections cause the anterior lens element to assume a spherical shape with a shorter radius of curvature , thereby changing the diopter power of the lens . as will of course be understood , optic portion could instead be arranged so that the lens piston deflects posterior lens element 27 ; the arrangement depicted in fig3 is illustrative only . the inner surface and thickness of anterior element 23 ( relative to the optical axis of the lens ) are selected so that the outer surface of anterior element 23 retains an optically corrective shape , e . g ., spherical , throughout the entire range of motion of lens piston 25 , e . g ., for accommodations 0 - 10 diopters . it should of course be understood that the inner surface and thickness of anterior element 23 may be selected to provide an aspherical outer surface , as required for a desired degree of optical correction . as shown in fig3 , one preferred embodiment of actuator layer 24 includes a single lens piston 25 located at the center of optic portion 21 . alternative embodiments of actuator layer 24 ′ may include an array of lens pistons 25 ′ spaced apart in a predetermined configuration on the anterior surface of the actuator layer , as depicted in fig4 , as may be required to impose a desired pattern of localized deflection on the anterior lens element . as will be apparent to one of skill in the art , an annular structure may be substituted for the individual lens pistons depicted in fig4 , and side walls 40 may be of any desired shape other than cylindrical . referring now to fig5 a and 5b , haptic pistons 42 , constructed in accordance with the principles of the present invention are described in greater detail . haptic pistons comprise flexible and resilient transducers 30 that support force - concentrating fins 31 biased against diaphragms 32 . each diaphragm 32 comprises an elastomeric cover for a corresponding reservoir 33 filled with fluid 38 . as described herein above , fluid 38 communicates through channels 34 into well 35 and the interior of lens piston 25 . transducers 30 are constructed from a resilient , elastomeric material that changes shape responsive to forces applied by capsule 15 from the ciliary muscles 13 and zonules 14 . in fig5 a , haptic piston 42 is shown in an undeformed state ( as in fig3 b ), corresponding to the ciliary muscles being fully contracted . in this state , the apex of fin 31 bears against diaphragm 32 to develop the maximum force resulting from the bias of transducer 30 . inward displacement of diaphragm 32 in turn displaces fluid through channels 34 ( see fig3 ) to well 35 , resulting in expansion of end wall 41 of lens piston 25 . when transducer 30 is in the undeformed state , fin 31 displaces the maximum volume of fluid from the haptic portion to lens piston 25 , resulting in the maximum deflection of anterior element 23 , and thus the maximum degree of accommodation of the lens . this corresponds to the state in which the ciliary muscles are fully contracted , and zonules 14 and capsule 15 apply the least amount of compressive force to the anterior and posterior surfaces of transducer 30 . when the ciliary muscles relax , however , the tension in the zonules increases , causing capsule 15 to assume an ellipsoidal shape ( see fig2 a ) and the lens to transition to its unaccommodated state . when the capsule becomes taut , it applies compressive forces f to the anterior and posterior surfaces of transducer 30 , causing the transducer to deform to the elliptical shape depicted in fig5 b . deformation of transducers 30 moves fins 31 away from diaphragms 32 , thereby unloading the diaphragms and reducing the fluid pressure applied to lens piston 25 . this in turn permits lens piston 25 to move to an undeflected state , reducing deflection of anterior lens element 23 and returning the lens to an unaccommodated state . referring now to fig6 a to 6 c , iol 20 is shown implanted into capsule 15 of human eye 10 . when so implanted , haptic arms 28 and 29 support the iol within the capsule , while transducers 30 engage the interior of the capsule at locations adjacent to ciliary muscles 13 . in fig6 b the ciliary muscles are shown in a contracted state , in which the compressive forces applied by zonules 14 and capsule 15 to transducers 30 is lowest and transducers 30 assume the undeformed position . this also corresponds to transducers 30 applying the least tension to capsule 15 and zonules 14 . as discussed above , in the undeformed position , fins 30 are biased against diaphragms 32 , displacing fluid 38 from reservoirs 33 to the lens piston . in fig6 c , the ciliary muscles are relaxed , and zonules 14 pull capsule 15 taut into an ellipsoidal shape . as noted above , in this state the capsule applies compressive forces to the lateral surfaces of transducers 30 that ensure that lens piston 25 is drawn to its fully retracted position . in accordance with one aspect of the present invention , the volume of fluid in the accommodating lens may be selected so that the forces required to provide a useable range of accommodation are satisfactory for a preselected population of patients . alternatively , the volume of fluid used in iol 20 may be specified during manufacture for a given patient , or may be adjusted prior to implantation of the iol on a patient - by - patient basis . in this manner , the forces developed by lens piston 25 and haptic pistons 42 may be tailored for a specific patient . in addition , the number , shape and placement of lens pistons 25 ′ on actuator layer 24 ′ may be selected , e . g ., prescribed during manufacture , to optimize accommodation of the lens for a specific patient . it may been noted that in the undeformed state , transducers 30 maintain the lens in the accommodated or high power state . accordingly , any failure that allows the transducers to assume the undeformed state without any physiologic influence could result in a residual near - sighted condition . in accordance with another aspect of the present invention it would be advantageous to provide for a mechanism to relieve a small amount of quiescent pressure within the lens so that the lens piston assumes the unaccommodated , low power state . to accomplish this result , a relief valve in the form of a sacrificial plug may de disposed on a channel that leads to an evacuated cavity . the plug may be constructed of material that remodels when activated by a laser to permit a reduction of the pressure in the lens piston , and thereby allowing the anterior lens element to assume the unaccommodated state . the plug preferably comprises a colored material that readily and preferentially absorbs laser light , for example , 1 . 06 micron wavelength radiation from a nd : yag laser . when irradiated , the plug experiences a phase change or otherwise deforms to permit a predetermined quantity of fluid in the channel 34 to enter the evacuated cavity . referring now to fig7 a to 7 c , an alternative embodiment of the iol of the present invention is described . iol 50 comprises optic portion 51 and haptic portion 52 . optic portion 51 comprises anterior lens element 53 and substrate 54 formed of light - transmissive materials . substrate 54 includes lens piston 55 having expandable end wall 56 , and fluid channels 57 in fluid communication with the interior of lens piston 55 . expandable end wall 56 contacts the inner surface of anterior lens element 53 , so that deflection of end wall 56 causes anterior lens element 53 to assume a more convex shape . the thickness profile of anterior lens element 53 is tailored to a desired degree of optical correction when deflected , as previously described . channels 57 and space 58 , disposed between anterior lens element 53 and substrate 54 , are filled with fluid 59 having an index of refraction that is matched to the materials of anterior lens element 53 and substrate 54 . substrate 54 may include integrally formed posterior lens element 60 . haptic portion 52 is disposed at the periphery of optic portion 51 , and includes transducers 61 that include force - concentrating fins 62 coupled to diaphragms 63 . fluid channels 57 extend circumferentially along the edges of substrate 54 for an arc - length corresponding to the arc - length of haptic portions 52 to form edge recesses 64 that function as reservoirs . transducer 61 , fin 62 , diaphragm 63 and edge recess 64 together form a haptic piston that adjusts the deflection of end wall 56 of lens piston 55 responsive to contraction and relaxation of the ciliary muscle , zonules and capsule . as in the embodiment of fig3 - 6 , transducers 61 are constructed so that , in the undeformed state , they bias force - concentrating fins 62 to cause the maximum inward displacement of diaphragms 63 . because diaphragms 63 of the haptic pistons are coupled to fins 62 , compressive forces applied to the anterior and posterior faces of transducers 61 by the capsule during relaxation of the ciliary muscles urges the iol to its unaccommodated state by deforming transducers 61 and withdrawing fluid from lens piston 55 . as illustrated in fig7 b , contraction of the ciliary muscles causes the zonules and capsule to relax , thereby reducing the compressive forces applied by the capsule to transducers 61 . this permits transducers 61 to return to an undeformed state in which fins 62 extend radially inward to displace diaphragms 63 into edge recesses 64 . this in turn displaces fluid 59 to the lens piston , causing end wall 56 to deflect anterior lens element 53 to the accommodated state . relaxation of the ciliary muscles causes the zonules and capsule to become taut , thereby compressing transducers 61 to deform to the position shown in fig7 c . more specifically , the compressive forces applied by the zonules and capsule deform transducers 61 to an elongated shape . this in turn causes fins 62 and diaphragms 63 to deflect outward away from edge recesses 64 , and draw fluid from lens piston 55 , returning the lens to its unaccommodated state . referring to fig8 a - 8c , another alternative embodiment of the intraocular lens of the present invention is described . iol 70 includes optic portion 71 and haptic portion 72 . iol 70 differs from the iol 50 primarily in that haptic portion 72 is disposed around the entire optic portion , and in addition haptic portion 72 omits the use of haptic pistons , as in the preceding embodiments . optic portion 71 comprises anterior lens element 73 and substrate 74 formed of light - transmissive materials . substrate 74 includes lens piston 75 having expandable end wall 76 , and fluid channels 77 in fluid communication with the interior of lens piston 75 . expandable end wall 76 contacts the inner surface of anterior lens element 73 , so that deflection of end wall 76 causes anterior lens element 73 to assume a more convex shape , as in the preceding embodiments . the thickness profile of anterior lens element 73 is tailored to produce a desired degree of accommodation when deflected , as previously described . channels 77 and space 78 , disposed between anterior lens element 73 and substrate 74 , are filled with fluid 79 having a matched index of refraction . substrate 74 may define a posterior lens surface 80 , or may include a separate lens element . haptic portion 72 is disposed surrounding the periphery of optic portion 71 , and includes transducer 81 . transducer 81 comprises diaphragm 82 including elastomeric ring 83 disposed along the midline of the diaphragm that biases the ring to the radially compressed state depicted in fig8 a and 8b . this state corresponds to the maximum deflection of lens piston 75 , and thus the state of maximum accommodation of lens 70 . ring 83 also ensures that diaphragm 82 engages and applies tension to the capsule . transducer 81 adjusts the deflection of end wall 76 of lens piston 75 responsive to contraction and relaxation of the ciliary muscle , zonules and capsule . more specifically , contraction of the ciliary muscles causes the zonules and capsule to relax , thereby reducing the compressive forces applied by the capsule to transducer 81 . this permits the transducer to return to an undeformed state , in which ring 83 biases diaphragm 82 to displace fluid to lens piston 75 . this in turn causes end wall 76 to deflect anterior lens element 73 to the accommodated state . relaxation of the ciliary muscles causes the zonules and capsule to become taut , thereby applying compression to the anterior and posterior surfaces of transducer 81 to deform to the diaphragm to the position shown in fig8 c . in particular , the compressive forces applied by the zonules and capsule deform transducer 81 to an elongated shape that reduces the pressure on fluid 59 and permits end wall 76 of lens piston 75 to transition to the undeflected state shown in fig8 c . this in turn reduces deflection of anterior lens element 73 and returns the lens to its unaccommodated state . referring now to fig9 a - 9c , a second family of embodiments of intraocular lenses is described . unlike the preceding embodiments , in which action of the ciliary muscle is transmitted to the iol via the zonules and capsule , in this embodiment action of the ciliary muscle directly against the transducer is communicated to the lens piston . as depicted in fig9 a , iol 90 may be implanted anterior to the capsule , and includes optic portion 91 and haptic portion 92 . optic portion 91 comprises anterior lens element 93 and substrate 94 formed of light - transmissive materials . substrate 94 includes lens piston 95 having expandable end wall 96 , and fluid channels 97 in fluid communication with the interior of lens piston 95 . expandable end wall 96 contacts the inner surface of anterior lens element 93 , so that deflection of end wall 96 causes anterior lens element 93 to assume a more convex shape . as in the preceding embodiments , the thickness profile of anterior lens element 93 may be tailored to produce a desired degree of accommodation when deflected . channels 97 and space 98 , disposed between anterior lens element 93 and substrate 94 , are filled with fluid 99 having a matched index of refraction . substrate 94 may define a posterior lens surface 100 , or may include a separate lens element . the optical power provided by posterior lens surface 100 may be used to provide the base power of the device , and may be tailored for specific patient population . the profile of posterior lens surface 100 also may be chosen to provide optimal performance of the optical system in concert with the optical correction provided by anterior lens element 93 throughout its range of motion . in addition or alternatively , any error of the refractive surface of anterior lens element 93 , for example 1 or 2 microns or less of wave error that the surface experiences throughout its range of motion , may be further reduced by adding a small compensating thickness to anterior lens element 93 , in exactly the reverse sense of the error , e . g ., corresponding to the average error incurred at each point on anterior lens element 93 through its range of motion . haptic portion 92 includes a plurality of transducers 101 , each transducer comprising diaphragm 102 . transducers 101 are designed to directly engage the ciliary muscle in the area of the sulcus , and comprise resilient , flexible diaphragms 102 that have an undeformed shape depicted in fig9 c . the interiors of diaphragms 102 form reservoirs 103 communicate with channels 97 , and are filled with index - matched fluid 99 . contraction of the ciliary muscles applies a radially compressive force to the transducers that transitions the diaphragms to the shape depicted in fig9 b . this causes fluid to be displaced from reservoirs 103 of transducers 101 , pressurizing the fluid in channels 99 and lens piston 95 . responsive to this pressure increase , end wall 96 of the lens piston expands anteriorly , deflecting anterior lens element 93 and transitioning the lens to the accommodated state , as shown in fig9 b . when the ciliary muscle subsequently relaxes , the radially compressive forces applied by the muscles diminish , transducer 101 returns to an undeformed state of fig9 c , and lens piston resumes its unexpandable position . this in turn reduces deflection of anterior lens element 93 and returns the lens to its unaccommodated state . while the design of the haptic portion of the embodiment of fig9 is similar to those of previously - known fluid - mediated accommodating intraocular lenses , such as those described in the aforementioned patent to christie , the presence of lens piston 95 is expected to provide significantly greater volumetric mechanical advantage and greater dynamic range than could be achieved with prior art designs . whereas previously - known designs distribute a pressure increase resulting from action of the ciliary muscle over the entire surface of the lens , the lens piston of the present invention amplifies motion of the ciliary muscle , e . g ., 100 microns , by the ratio of the transducer area to the area of the lens piston . it is expected that ratios of 2 or more may be readily achieved , however , a ratio of one may be sufficient for many patient populations . accordingly , the amount of fluid that must be displaced to optically correct axial displacement of the refractive surface of anterior lens element 23 is relatively small . with respect to fig1 a - 10c , a third family of embodiments of the intraocular lens of the present invention is described . like the embodiments of fig3 - 8 , iol 110 is implanted within the capsule , includes haptic pistons , and is actuated by action of the ciliary muscles , zonules and capsule . however , as in the embodiment of fig9 , the lens is unaccommodated in its unstressed condition , and transitions to the accommodated state upon application of radially compressive forces . in particular , whereas the embodiments of fig3 - 6 transition from the accommodated state to the unaccommodated state by virtue of lateral ( anterior and posterior ) compressive forces applied during the capsule during relaxation , the embodiment of fig1 transitions to the accommodated state upon thickening of the capsular equator during contraction of the ciliary muscles . the structure of iol 110 is similar to that of iol 90 of fig9 , with like parts identified by like - primed numbers , except that transducers 101 ′ are surrounded by force concentrating elements 111 , and haptic portions 92 ′ further comprise flanges 112 that orient iol 110 within the capsule and maintain tension on the zonules . more specifically , iol 110 includes optic portion 91 ′ and haptic portion 92 ′. optic portion 91 ′ comprises anterior lens element 93 ′ and substrate 94 ′ formed of light - transmissive materials . substrate 94 ′ includes lens piston 95 ′ having expandable end wall 96 ′, and fluid channels 97 ′ in fluid communication with the interior of lens piston 95 ′. expandable end wall 96 ′ contacts the inner surface of anterior lens element 93 ′, so that deflection of end wall 96 ′ causes anterior lens element 93 ′ to assume a more convex shape . as in the preceding embodiments , the thickness profile of anterior lens element 93 ′ may be tailored to produce a desired degree of accommodation when deflected . channels 97 ′ and space 98 ′, disposed between anterior lens element 93 ′ and substrate 94 ′, are filled with fluid 99 ′ having a matched index of refraction . substrate 94 ′ defines posterior lens surface 100 ′. haptic portion 92 ′ includes transducers 101 ′, with each transducer having diaphragm 102 ′. arcuate force - concentrating elements 111 are disposed radially outward of transducers 101 ′ and illustratively have fixed end 113 connected to haptic portion 92 and free end 114 . elements 111 contact the equator of capsule 15 and flex radially inward or outward to follow thickening or thinning of the capsular equator responsive to contraction of the ciliary muscles . elements 111 , diaphragms 102 ′, and reservoirs 103 ′ together form haptic pistons . elements 111 and diaphragms 102 ′ have an undeformed shape depicted in fig1 c . as in the preceding embodiments reservoirs 103 ′ communicate with channels 97 ′, and are filled with index - matched fluid 99 ′. as noted above , laterally - extending flanges 112 apply tension to the capsule to orient the iol within the capsule and maintain tension on the zonules when the capsule changes shape responsive to action of the ciliary muscles . as described herein above with respect to fig2 , contraction of the ciliary muscles causes the capsule to become more spherical and thicken along its equator . this thickening applies a radially compressive force to elements 111 of transducers 101 ′ that compresses diaphragms 102 ′ to the deformed shapes depicted in fig1 a and 10b . this causes fluid to be displaced from reservoirs 103 ′ of transducers 101 ′, pressurizing the fluid in channels 97 ′ and lens piston 95 ′. responsive to this pressure increase , end wall 96 ′ of the lens piston expands anteriorly , deflecting anterior lens element 93 ′ and transitioning the lens to the accommodated state , as shown in fig1 b . frames 112 retain iol 110 centered on the capsular equator as the capsule transitions to a more spherical shape . when the ciliary muscle subsequently relaxes , the radially compressive forces applied by the muscles diminish , the capsule becomes more ellipsoidal , and the capsular equator thins . frames 112 become compressed by the lateral forces applied by the capsule and zonules , and transducers 101 ′ follow the elongation of the capsule , with free ends 114 of elements 111 deflecting outward to the undeformed state depicted in fig1 c . this in turn relieves compression of diaphragms 102 ′, so that fluid moves from channels 97 ′ back to reservoirs 103 ′, and lens piston 95 ′ resumes its unexpanded position . consequently , anterior lens element 93 ′ returns to its undeflected state and lens 110 transitions to the unaccommodated state shown in fig1 c . referring to fig1 a - 11c , a further alternative embodiment of the intraocular lens of the present invention is described . iol 120 is similar in construction to iol 110 , and like components are designated by like double prime numbers . thus , for example , while the anterior lens element of fig1 a is designated 93 ′, the anterior lens element of fig1 a is designated 93 ″. iol 120 differs from iol 110 of fig1 in that diaphragm 102 ′ is omitted , and reservoir 103 ″ is defined by an internal lumen of element 111 ″ that communicates with channel 97 ″ via opening 121 . in iol 120 , element 111 ″ therefore defines transducer 101 ″. as in iol 110 of fig1 , iol 120 is disposed within the capsule and transitions to the accommodated state upon thickening of the capsular equator during contraction of the ciliary muscles . flanges 112 ″ that orient the iol within the capsule and maintain tension on the zonules . iol 120 includes optic portion 91 ″ and haptic portion 92 ″. optic portion 91 ″ comprises anterior lens element 93 ″ and substrate 94 ″ formed of light - transmissive materials . substrate 94 ″ includes lens piston 95 ″ having expandable end wall 96 ″, and fluid channels 97 ″ in fluid communication with the interior of lens piston 95 ″. expandable end wall 96 ″ contacts the inner surface of anterior lens element 93 ″, so that deflection of end wall 96 ″ causes anterior lens element 93 ″ to assume a more convex shape . as in the preceding embodiments , the thickness profile of anterior lens element 93 ″ may be tailored to produce a desired degree of accommodation when deflected . channels 97 ″ and space 98 ″, disposed between anterior lens element 93 ″ and substrate 94 ″, are filled with index - matched fluid 99 ″. substrate 94 ″ defines posterior lens surface 100 ″. haptic portion 92 ″ includes transducers 101 ″ in the form of arcuate elements 111 ″ having fixed end 113 ″ connected to haptic portion 92 ″ and free end 114 ″. elements 111 ″ include internal lumens defining reservoirs 103 ″ that are in fluid communication with channels 97 ″ via openings 121 . elements 111 ″ contact the equator of capsule 15 and flex radially inward or outward to follow thickening or thinning of the capsular equator responsive to contraction of the ciliary muscles . elements 111 ″ have the undeformed shape depicted in fig1 c . reservoirs 103 ″ m , channels 97 ″ and lens piston 95 ″ are filled with index - matched fluid 99 ″. as noted above , laterally - extending flanges 112 ″ apply tension to the capsule to orient the iol within the capsule and maintain tension on the zonules when the capsule changes shape responsive to action of the ciliary muscles . as for iol 110 , contraction of the ciliary muscles causes the capsule to become more spherical and thicken along its equator , thereby applying a radially compressive force to transducers 101 ″ that compresses elements 111 ″ to the deformed shapes depicted in fig1 a and 11b . this causes fluid to be displaced from reservoirs 103 ″ of transducers 101 ″, pressurizing the fluid in channels 97 ″ and lens piston 95 ″. responsive to this pressure increase , end wall 96 ″ of the lens piston expands anteriorly , deflecting anterior lens element 93 ″ and transitioning the lens to the accommodated state , as shown in fig1 b . frames 112 ″ retain iol 120 centered on the capsular equator as the capsule transitions to a more spherical shape . when the ciliary muscle subsequently relaxes , the radially compressive forces applied by the muscles diminish , the capsule becomes more ellipsoidal , and the capsular equator thins . frames 112 ″ become compressed by the lateral forces applied by the capsule and zonules , and transducers 101 ″ follow the elongation of the capsule , with free ends 114 ″ of elements 111 ″ deflecting outward to the undeformed state depicted in fig1 c . this in turn relieves compression of transducers 101 ″, so that fluid moves from channels 97 ″ back to reservoirs 103 ″, and lens piston 95 ″ resumes its unexpanded position . consequently , anterior lens element 93 ″ returns to its undeflected state and lens 120 transitions to the unaccommodated state shown in fig1 c . in fig1 a - 12c , still another embodiment of an intraocular lens constructed in accordance with the principles of the present invention is described . iol 130 comprises optic portion 131 and haptic portion 132 . optic portion 131 comprises anterior lens element 133 and substrate 134 formed of light - transmissive materials . substrate 134 includes lens piston 135 having expandable end wall 136 , and fluid channels 137 in fluid communication with the interior of lens piston 135 . expandable end wall 136 contacts the inner surface of anterior lens element 133 , so that deflection of end wall 136 causes anterior lens element 133 to assume a more convex shape . the thickness profile of anterior lens element 133 is tailored to provide a desired degree of optical correction throughout its range of deflection . channels 137 and space 138 , disposed between anterior lens element 133 and substrate 134 , are filled with fluid 139 having an index of refraction that is matched to the materials of anterior lens element 133 and substrate 134 . substrate 134 includes posterior lens surface 140 . haptic portion 132 is disposed at the periphery of optic portion 131 , and includes transducers 141 having segments 142 slidably disposed in edge recesses 143 . edge recesses 143 are defined by extensions 144 of fluid channels 137 that extend circumferentially along the edges of substrate 134 for an arc - length corresponding to the arc - length of haptic portions 132 and function as reservoirs . segments 142 are coupled to diaphragms 145 so that force applied to the outer edges of segments 142 by the capsular equator causes the segments to be displaced radially inward . laterally - extending flanges 146 apply tension to the capsule to orient iol 130 within the capsule and maintain tension on the zonules . segment 142 , substrate extensions 144 , diaphragm 145 and edge recess 143 together form a haptic piston that transfers fluid to lens piston 135 responsive to contraction and relaxation of the ciliary muscle , zonules and capsule . specifically , inward movement of segments 142 causes diaphragms 145 to displace inwardly into edge recesses 143 , thereby transferring fluid to lens piston 135 . as in the preceding embodiment , fluid entering lens piston 135 expands end wall 136 , thereby deflecting anterior lens element 133 to its accommodated shape , as shown in fig1 a and 12b . in fig1 c , when the ciliary muscles relax , the capsule elongates and applies laterally compressive forces to flanges 146 . as the capsule elongates , the forces applied to segments 142 decrease , allowing end wall 136 to return to its unexpanded state and permitting anterior lens element 133 to return to the unaccommodated state . while preferred illustrative embodiments of the invention are described above , it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention . the appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention .
an accommodating intraocular lens is provided having optical parameters that are altered in - situ , wherein an optic portion of the lens includes a lens piston that alters the shape of a lens element of the lens to alter the optical power of the lens , responsive to forces applied to a haptic portion to the lens by contraction of the ciliary muscles . forces applied to the haptic portion are concentrated by the lens piston to provide a greater dynamic range , and may be further augmented by the use of haptic pistons disposed in the haptic portion of the lens .