Abstract:
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 transferred hydraulically to cause the lens to become more or less accommodated. The haptic portion is retained in a fixed unaccommodated state during an initial healing period following implantation to facilitate affixation of the haptic portion to the capsule.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to intraocular lenses (“IOLs”) having optical parameters that are changeable in-situ. More particularly, the invention has applications in IOLs for in-capsule implantation for cataract patients, wherein forces applied by the movement of the zonules induce movement of fluid media within the interior of the IOL, thereby altering an optical power of the lens to provide accommodation.  
       BACKGROUND OF THE INVENTION  
       [0002]     Cataracts are a major cause of blindness in the world and the most prevalent ocular disease. Visual disability from cataracts accounts for more than 8 million physician office visits per year. When the disability from cataracts affects or alters an individual&#39;s activities of daily living, surgical lens removal with intraocular lens (IOL) implantation is the preferred method of treating the functional limitations. In the United States, about 2.5 million cataract surgical procedures are performed annually, making it the most common surgery for Americans over the age of 65. About 97 percent of cataract surgery patients receive intraocular lens implants, with the annual costs for cataract surgery and associated care in the United States being upwards of $4 billion.  
         [0003]     A cataract is any opacity of a patient&#39;s lens, whether it is a localized opacity or a diffuse general loss of transparency. To be clinically significant, however, the cataract must cause a significant reduction in visual acuity or a functional impairment. A cataract occurs as a result of aging or secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, or radiation. Age related cataract conditions are the most common.  
         [0004]     In treating a cataract, the surgeon removes the crystalline lens matrix from the lens capsule and replaces it with an intraocular lens (“IOL”) implant. The typical IOL provides a selected focal length that allows the patient to have fairly good distance vision. Since the lens can no longer accommodate, however, the patient typically needs glasses for reading.  
         [0005]     The imaging properties of the human eye are facilitated by several optical interfaces. A healthy youthful human eye has a total power of approximately 59 diopters, with the anterior surface of the cornea (e.g. the exterior surface, including the tear layer) providing about 48 diopters of power, while the posterior surface provides about −4 diopters. The crystalline lens, which is situated posterior of the pupil in a transparent elastic capsule supported by the ciliary muscles, provides about 15 diopters of power, and also performs the critical function of focusing images upon the retina. This focusing ability, referred to as “accommodation,” enables imaging of objects at various distances.  
         [0006]     The power of the lens in a youthful eye can be adjusted from 15 diopters to about 29 diopters by adjusting the shape of the lens from a moderately convex shape to a highly convex shape. The mechanism generally accepted to cause this adjustment is that ciliary muscles supporting the capsule (and the lens contained therein), move between a relaxed state (corresponding to the moderately convex shape) to a contracted state (corresponding to the highly convex shape). Because the lens itself is composed of viscous, gelatinous transparent fibers, arranged in an “onion-like” layered structure, forces applied to the capsule by the ciliary muscles cause the lens to change shape.  
         [0007]     Isolated from the eye, the relaxed capsule and lens take on a spherical shape. Within the eye, however, the capsule is connected around its circumference by approximately 70 tiny ligament fibers to the ciliary muscles, which in turn are attached to an inner surface of the eyeball. The ciliary muscles that support the lens and capsule therefore are believed to act in a sphincter-muscular mode. Accordingly, when the ciliary muscles are relaxed, the capsule and lens are pulled about the circumference to a larger diameter, thereby flattening the lens, whereas when the ciliary muscles are contracted, the lens and capsule relax somewhat and assume a smaller diameter that approaches a more spherical shape, thereby changing the diopter power of the lens.  
         [0008]     As noted above, the youthful eye has approximately 14 diopters of accommodation. As a person ages, the lens hardens and becomes less elastic, so that by about age 45-50, accommodation is reduced to about 2 diopters. At a later age the lens may be considered to be non-accommodating, a condition known as “presbyopia”. Because the imaging distance is fixed, presbyopia typically entails the need for bi-focals to facilitate near and far vision.  
         [0009]     Apart from age-related loss of accommodation ability, such loss is innate to the placement of IOLs for the treatment of cataracts. IOLs are generally single element lenses made from a suitable polymer material, such as acrylics or silicones. After placement, accommodation is no longer possible, although this ability is typically already lost for persons receiving an IOL. There is significant need to provide for accommodation in IOL products so that IOL recipients will have accommodating ability.  
         [0010]     Although previously known workers in the field of accommodating IOLs have made some progress, the relative complexity of the methods and apparatus developed to date have prevented widespread commercialization of such devices. Previously known devices have proved too complex to be practical to construct or have achieved only limited success, due to the inability to provide accommodation of more than 1-2 diopters.  
         [0011]     U.S. Pat. No. 5,443,506 to Garabet describes an accommodating fluid-filled lens wherein electrical potentials generated by contraction of the ciliary muscles cause changes in the index of refraction of fluid carried within a central optic portion. U.S. Pat. No. 4,816,031 to Pfoff discloses an IOL with a hard PMMA lens separated by a single chamber from a flexible thin lens layer that uses microfluid pumps to vary a volume of fluid between the PMMA lens portion and the thin layer portion and provide accommodation. U.S. Pat. No. 4,932,966 to Christie et al. discloses an intraocular lens comprising a thin flexible layer sealed along its periphery to a support layer, wherein forces applied to fluid reservoirs in the haptics vary a volume of fluid between the layers to provide accommodation.  
         [0012]     Although fluid-actuated mechanisms such as described in the aforementioned patents have been investigated, commercially available accommodating lenses, such as developed by Eyeonics, Inc. of Aliso Viejo, Calif., rely on ciliary muscle contraction of the IOL haptics to vault the optic towards or away from the retina to adjust the focus of the device.  
         [0013]     U.S. Patent Publication No. US2005/0119740, the application for which is co-pending and commonly assigned, describes an accommodating IOL in which shape changes of the capsular bag impose forces on a haptic portion of the IOL that in turn induce movement of fluid within an optic portion of the IOL. In the IOL described in that application, the lens assumes an accommodated state when unstressed, and moves to an unaccommodated state when subjected to laterally compressive forces by the capsule. While the IOLs described in that application include various mechanisms for retaining the capsule relatively taut throughout the range of accommodation, those IOLs do not provide a mechanism to ensure that the haptic portion does not migrate or become displaced when the ciliary muscles relax.  
         [0014]     In view of the foregoing, it would be desirable to provide apparatus and methods that restore appropriate optical focusing power action to the human eye.  
         [0015]     It further would be desirable to provide methods and apparatus wherein a dynamic lens surface may be effectively manipulated by the ciliary muscular mechanisms within the eye.  
         [0016]     It still further would be desirable to provide methods and apparatus that utilize pressure applied by the accommodating muscular action to obtain a volumetric mechanical advantage in deflecting an optical surface of the IOL. In particular, it would be desirable to provide an IOL in which muscular pressure may be applied through one or more actuators to obtain such volumetric mechanical advantage.  
         [0017]     It also would be desirable to provide an accommodating IOL having a feature that permits the haptic portion to be directly acted upon by movement of the zonules, so that radial movements of the zonules resulting from contraction or relaxation of the ciliary muscles are directly transferred to the haptic portion.  
         [0018]     It further would be desirable to provide an accommodating IOL having a feature that permits the haptic portion to become affixed within the capsule, thereby enhancing resistance to migration or displacement of the lens during normal movements of the components of the eye associated with accommodation.  
       SUMMARY OF THE INVENTION  
       [0019]     In view of the foregoing, it is an object of the present invention to provide apparatus and methods that restore appropriate optical focusing power action to the human eye.  
         [0020]     It is a further object of this invention to provide methods and apparatus wherein a dynamic lens surface may be effectively manipulated by the ciliary muscular mechanisms within the eye.  
         [0021]     It is another object of the present invention to provide methods and apparatus that utilize pressure applied by the accommodating muscular action to obtain volumetric mechanical advantage in deflecting an optical surface of the IOL.  
         [0022]     It is a further object of this invention to provide methods and apparatus for reversibly applying muscular pressure, through one or more actuators, to obtain a volumetric mechanical advantage in altering the optical parameters of one of more surfaces of the IOL.  
         [0023]     It is also an object of the present invention to provide an accommodating IOL having a feature that permits the haptic portion to be directly acted upon by movement of the zonules, so that radial movements of the zonules resulting from contraction or relaxation of the ciliary muscles are directly transferred to the haptic portion.  
         [0024]     It is a further object of the present invention to provide an accommodating IOL having a feature that permits the haptic portion to become affixed within the capsule, thereby enhancing resistance to migration or displacement of the lens during normal movements of the components of the eye associated with accommodation.  
         [0025]     These and other objects of the present invention are accomplished by providing an intraocular lens responsive to variations in capsule shape and/or forces exerted by the ciliary muscle to actuate one or more haptic pistons. The haptic pistons are coupled to a lens piston that deflects a surface of the lens, e.g., from a moderately convex to a highly convex shape.  
         [0026]     Further in accordance with the principles of the present invention, the lens is configured to promote affixation of a haptic portion of the lens to the capsular equator, thereby permitting risk force transfer between the zonules and haptic portion, and reducing the risk of migration or displacement of the IOL associated with operation of the accommodative mechanisms of the eye. Preferably, the lens is implanted into the eye restrained in a fixed unaccommodated state that urges the haptic portion into engagement with the capsular equator to promote the growth of fibrous tissue, thereby affixing the haptic portion to the capsule. Subsequently the restraint is removed to allow a complete range of accommodative motion of the lens.  
         [0027]     In a preferred embodiment, the intraocular lens comprises an optic portion and a haptic (or non-optic) portion. The optic portion comprises a light transmissive substrate defining one or more fluid channels, one or more lens pistons coupled in fluid communication with the fluid channels, and anterior and posterior lens elements. One of the anterior and posterior lens elements includes a deflectable surface that is operatively coupled to the one or more lens pistons so that movement of the lens pistons causes the anterior or posterior lens to deflect. The other of the anterior or posterior lens elements may be coupled to the substrate or integrally formed therewith.  
         [0028]     The haptic portion is disposed at the periphery of the optic portion and may comprise one or more arms that extend outward from the optic portion, each arm operatively coupled to a fluid channel in the optic portion. Each arm of the haptic portion includes a portion that engages the interior of the capsule and/or ciliary muscle, so that movement of the capsule and/or ciliary muscle is communicated via the fluid channels to the one or more lens pistons. In accordance with one aspect of the present invention, the haptic portion is biased to maintain the lens piston in an accommodated state. For such embodiments, relaxation of the ciliary muscle causes the zonules to transition the capsule to a less convex, unaccommodated shape. The capsule thereby applies tensile forces that deform the haptic portion and reduce fluid pressure in the lens piston, thereby causing the lens to transition to the unaccommodated state.  
         [0029]     Alternatively, the lens piston may not be pressurized when the transducer is in the undeformed state. In this latter case, the lens may be configured so that contraction of the ciliary muscle induces thickening near the capsular equator, which in turn compresses the haptic portion to pressurize the lens piston and transition the lens to the accommodated state.  
         [0030]     Methods of making and using the lens of the present invention also are provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:  
         [0032]      FIG. 1  is a sectional side view of a human eye;  
         [0033]      FIGS. 2A and 2B  are, respectively, sectional side views of the lens and supporting structures of  FIG. 1  illustrating relaxed and contracted states of the ciliary muscles;  
         [0034]      FIGS. 3A and 3B  are, respectively, an exploded perspective view and side sectional view, taken along line  3 B- 3 B of  FIG. 3A , of an exemplary accommodation mechanism suitable for use in the intraocular lens of the present invention;  
         [0035]      FIG. 4  is a perspective view of an alternative embodiment of lens pistons suitable for use in the intraocular lens of  FIG. 3 ;  
         [0036]      FIGS. 5A and 5B  are, respectively, side sectional views of the haptic portion of the lens of  FIG. 3  in the accommodated and unaccommodated states;  
         [0037]      FIGS. 6A-6C  are, respectively, a perspective view of the lens of  FIG. 3  disposed in a human eye and side sectional views of the lens in the accommodated and unaccommodated states;  
         [0038]      FIGS. 7A-7C  are, respectively, side sectional, exploded perspective, and plan views of an embodiment of the intraocular lens of the present invention;  
         [0039]      FIGS. 8A-8C  are respectively, side sectional, exploded perspective, and plan views of an alternative embodiment of the intraocular lens of the present invention; and  
         [0040]      FIGS. 9A-9C  are respectively, side sectional, exploded perspective, and plan views of an alternative embodiment of the intraocular lens of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]     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, least convex 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 movement of the ciliary muscles and deformation of the capsule.  
         [0042]     Forces imposed on the haptic portion are applied to a transducer and 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 or reflections throughout the range of motion of the lens piston.  
         [0043]     Referring to  FIGS. 1 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 .  
         [0044]     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  FIG. 2A , when ciliary muscles  13  relax, capsule  15  and lens  16  are pulled about the circumference, thereby flattening the lens. As depicted in  FIG. 2B , 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.  
         [0045]     Currently available accommodating lenses, such as the Crystalens device developed by Eyeonics, Inc., Aliso Viejo, Calif., converts ciliary muscle movements into vaulting movements of an optic portion of the IOL. Devices such as the Crystalens thus do not employ the natural accommodation mechanisms described above.  
         [0046]     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. More preferably, the haptic portion is configured to be affixed to the capsular equator, as described herein below.  
         [0047]     Referring to FIGS.  3  to  6 , the intraocular lens of U.S. Patent Publication No. US2005/0119740 is described as providing a suitable accommodation mechanism for use with the intraocular lens of the present invention. That publication describes an accommodating IOL in which shape changes of the capsular bag impose forces on a haptic portion of the IOL that in turn induce movement of fluid within an optic portion of the IOL. The lens assumes an accommodated state when unstressed, and transitions to an unaccommodated state when subjected to laterally compressive forces by the capsule.  
         [0048]     More specifically, referring to  FIGS. 3A and 3B , an exemplary embodiment of an intraocular lens suitable for implementing 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.  
         [0049]     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  includes a transducer  30  and 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  33  to well  35  disposed beneath lens piston  25 .  
         [0050]     In  FIG. 3B , transducers  30  are shown 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.  
         [0051]     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 .  
         [0052]     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  FIG. 3  is illustrative only.  
         [0053]     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.  
         [0054]     As shown in  FIG. 3 , 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  FIG. 4 , 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  FIG. 4 , and side walls  40  may be of any desired shape other than cylindrical.  
         [0055]     Referring now to  FIGS. 5A and 5B , flexible and resilient transducers  30  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 .  
         [0056]     In  FIG. 5A , the haptic piston is shown in an undeformed state (as in  FIG. 3B ), 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  FIG. 3 ) 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 .  
         [0057]     When the ciliary muscles relax, however, the tension in the zonules increases, causing capsule  15  to assume a less convex shape (see  FIG. 2A ) 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  FIG. 5B . 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.  
         [0058]     Referring now to  FIGS. 6A  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  FIG. 6B  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  FIG. 6C , the ciliary muscles are relaxed, and zonules  14  pull capsule  15  taut into a somewhat 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.  
         [0059]     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 the haptic pistons 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.  
         [0060]     The IOL described in  FIGS. 3-6  above contemplates that the capsule will remain relatively taut throughout the range of accommodation. That IOL does not, however, provide direct transfer of forces from the zonules to the IOL, nor a mechanism to ensure that the haptic portion does not migrate or become displaced when the ciliary muscles relax. The improvements described hereinafter are intended to permit the haptic portion to be directly acted upon by movement of the zonules. In this manner, radial movements of the zonules resulting from contraction or relaxation of the ciliary muscles are directly transferred to the haptic portion. In addition, the improvements provided herein address the potential issue of migration of the intraocular lens within the capsular bag by affixing the arms of the haptic portion to the capsular equator.  
         [0061]     Referring now to  FIGS. 7A-7C , an intraocular lens constructed in accordance with the principles of the present invention is described. IOL  50  comprises optic portion  51  and haptic portion  52 . Optic portion  51  is constructed of light transmissive materials, while haptic portion  52  is disposed at the periphery of the optic portion and does not participate in focusing light on the retina of the eye.  
         [0062]     Optic portion  51  comprises anterior lens element  53  with bellows-shaped lens piston  54 , substrate  55  and posterior lens element  56 , 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. As in the preceding embodiment, fluids having indices of refraction matched to the solid components of optic portion  51 , such as silicone or acrylic oils, are disposed within the lens piston, channels and other spaces of the lens. The side wall of lens piston  54  is configured to deflect inward responsive to pressure increases within the lens piston, which in turn deflect anterior lens element  53  to assume more convex shape, thereby changing the diopter power of the lens.  
         [0063]     The inner surface and thickness of anterior lens element  53  (relative to the optical axis of the lens) are selected so that the outer surface of anterior element  53  retains an optically corrective shape, e.g., spherical, throughout the entire range of motion of lens piston  54 , e.g., for accommodations 0-10 diopters. It should of course be understood that the inner surface and thickness of anterior lens element  53  also may be selected to provide an aspherical outer surface, as required for a desired degree of optical correction.  
         [0064]     Haptic portion  52  comprises support ring  57  carrying arms  58  and  59 . Preferably, haptic portion  52  is molded of an elastic polymeric material, such as silicone or polyurethane, that tends to return to its undeformed shape after a deformation occurs. Other embodiments of haptic portion  52  may be machined from a single piece of shape memory material, such as nickel-titanium, or may be formed from other material having elastic properties. Support ring  57  surrounds and is affixed to substrate  55 . Each of arms  58  and  59  comprises a pair of support elements  60  coupled to arched portion  61 . Suture anchors  62  are disposed on support elements  60 , while arched portion  61  carries outwardly-directed barbs  63  and inwardly-directed piston element  64 .  
         [0065]     As used herein, barbs may comprise one or more parallel ridges, hooks, or other attachment devices. These devices may be simple, such as a roughened surface of the haptic or use of a dimpled texture. Likewise, these devices may be more advanced, such as an arrangement of attachment devices in an offset fashion, resembling fish scales, to further enhance attachability and reduce the tendency for the haptic portion to dislodge from the capsular bag.  
         [0066]     The radially inward-most ends of each of piston elements  64  is disposed in contact with diaphragm  65  and reservoir  66 . Each of reservoirs  66  is coupled in fluid communication with the interior of lens piston  54  via channels  67  that extend from reservoirs  66  to well  68  disposed beneath lens piston  54 . Together, piston elements  64 , diaphragm  65  and reservoir  66  form a haptic piston that supplies fluid to lens piston  54  responsive to movements of the ciliary muscle and the capsular bag; these fluid movements in turn transition lens  50  between the accommodated and unaccommodated states.  
         [0067]     Haptic portion  52  is configured so that in its unstressed state piston elements  64  extend to radially inward to the maximum extent. This state corresponds to maximum displacement of fluid from the haptic piston to lens piston  54 , maximum displacement of lens piston  54 , and the fully accommodated state of lens  50 . Barbs  63  are configured to engage the capsular equator so that when the ciliary muscles relax, the capsule pulls arched portions  61  and piston elements  64  radially outward, thereby transitioning the lens to the unaccommodated state.  
         [0068]     In accordance with one aspect of the present invention, IOL  50  is configured to be placed in the capsule of a patient&#39;s eye in the unaccommodated state, with the arched portions of arms  58  and  59  extending radially outward to the maximum extent. This may be achieved by placing suture  70  (one shown in dotted line in  FIG. 7C ) across suture anchors  62  to compress the support elements  60  of each arm  58  and  59  towards one another. This in turn causes arched portions  61  to be deflected radially outward and holds piston elements  64  out of contact with diaphragms  65  of the haptic pistons.  
         [0069]     When IOL  50  is implanted into the patient&#39;s native capsule in the unaccommodated state, barbs  63  engage the capsular equator. Sutures  70  remain in place during an initial period of several days to weeks, during which time fibrous tissue adheres to arched portions  61  and barbs  63 , causing arms  58  and  59  to become affixed to the capsular equator. Preferably, sutures  70  comprise a resorbable material that disintegrates after several days to weeks, thereafter releasing arms  58  and  59  to allow IOL  50  to accommodate responsive to movements of the ciliary muscles and capsule.  
         [0070]     More specifically, once sutures  70  are resorbed, support elements  61  no longer retain with arched portions  61  at the maximum radially outward deflection. Accordingly, arms  58  and  59  are free to move inward under the bias of the predetermined shape stored in the shape memory material until constrained by the opposing forces applied by the ciliary muscles, capsule and zonules. For example, if the ciliary muscles contract, the capsular equator moves radially inward and piston elements  64  bear fully against diaphragms  65 . This action displaces fluid from reservoirs  66  to lens piston  54 , causing the anterior lens element to deflect to the accommodated state. When the ciliary muscles contract, the zonules pull the capsular equator to a larger diameter, thereby applying tensile forces to arms  58  and  59  that reduce the inward deflection of piston elements  64 . This action causes fluid in lens piston  54  to move to reservoirs  66 , and reduces the degree of accommodation provided by IOL  50 .  
         [0071]     In a preferred embodiment, the resorbable characteristics of the suture may be selected to correspond to the expected “heal-in” period, that is, the period during which fibrous growth cause barbs  63  to become embedded in the capsular equator. Thus, the sutures will naturally resorb and release arms  58  and  59 , thereby allowing accommodating movement of lens piston  54  and anterior element  53 . In an alternative embodiment the sutures may be released by severing the sutures using a Nd:YAG laser or similar device.  
         [0072]     As for the preceding embodiment, the volume of fluid in IOL  50  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 the IOL 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  54  and the haptic pistons may be tailored for a specific patient.  
         [0073]     As will of course be understood, optic portion  51  could instead be arranged so that the lens piston is integrated with posterior lens element  56  instead of anterior lens element  53 , and causes deflection the posterior lens element  56 ; the arrangement depicted in  FIG. 7  is illustrative only.  
         [0074]     Referring now to  FIGS. 8A-8C , an alternative embodiment of an intraocular lens of the present invention is described. IOL  80  comprises optic portion  81  and haptic portion  82 . Optic portion  81  is constructed of light transmissive materials, while haptic portion  82  is disposed at the periphery of the optic portion and does not participate in focusing light on the retina of the eye.  
         [0075]     Optic portion  81  comprises anterior lens element  83  with bellows-shaped lens piston  84 , a portion of substrate  85  and posterior lens element  86 , 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. As in the preceding embodiment, fluids having indices of refraction matched to the solid components of optic portion  81 , such as silicone or acrylic oils, are disposed within the lens piston, channels and other spaces of the lens. The side wall of lens piston  84  is configured to deflect inward responsive to pressure increases within the lens piston, which in turn deflect anterior lens element  83  to assume more convex shape, thereby changing the diopter power of the lens.  
         [0076]     The inner surface and thickness of anterior lens element  83  (relative to the optical axis of the lens) are selected so that the outer surface of anterior element  83  retains an optically corrective shape, e.g., spherical, throughout the entire range of motion of lens piston  84 , e.g., for accommodations 0-10 diopters. It should of course be understood that the inner surface and thickness of anterior lens element  83  also may be selected to provide an aspherical outer surface, as required for a desired degree of optical correction.  
         [0077]     Haptic portion  82  comprises peripheral portion  87  of substrate  85  including arms  88  and  89  and retainer supports  90 . Preferably, haptic portion  82  is molded or machined from a single piece of a resilient elastomeric material. Each of arms  88  and  89  comprises flexible bellows  91  having ribbed distal portion  92  configured to engage the capsular equator. Bellows  91  are coupled to reservoirs  93  in substrate  85  so that fluid disposed in bellows  91  may be displaced through channels  94  to and from lens piston  84  responsive to movement of distal portions  92 . Distal portions  92  in addition include recesses  95  that accept the ends of retainer rods  96  disposed in retainer supports  90 , for the purposes described below.  
         [0078]     More particularly, each of reservoirs  93  is coupled in fluid communication with the interior of lens piston  84  via channels  94  that extend from reservoirs  93  to well  97  disposed beneath lens piston  84 . Together, bellows  91  and reservoirs  93  form haptic pistons that supply fluid to lens piston  84  responsive to movements of the ciliary muscle and the capsular bag; these fluid movements in turn transition lens  80  between the accommodated and unaccommodated states.  
         [0079]     Haptic portion  82  is configured so that in its unstressed state bellows  91  extend to radially inward to the maximum extent. This state corresponds to maximum displacement of fluid from the haptic pistons to lens piston  84 , maximum displacement of lens piston  84 , and the fully accommodated state of lens  80 . Ribs  98  on distal portions  91  are configured to engage the capsular equator so that when the ciliary muscles relax, the capsule pulls distal portions  92  and bellows  91  radially outward, thereby transitioning the lens to the unaccommodated state.  
         [0080]     In accordance with one aspect of the present invention, IOL  80  is configured to be placed in the capsule of a patient&#39;s eye in the unaccommodated state, with arms  88  and  89  extending radially outward to the maximum extent. This is achieved by extending retainer rods  96  from retainer supports  90  so that the distal ends of the retainer rods  96  are captured in recesses  95  in distal portions  92  (as depicted in  FIG. 8C ). Retainer rods  96  preferably comprise a shape memory alloy having a low temperature elongated martensitic state and transform to a reduced length when heated into the austenitic phase. Retainer rods  96  therefore are installed in retainer supports  90  in the elongated state so that they are slidingly captured in recesses  95  to retain distal portions  92  at the maximum extension. When heated into the austenitic phase, retainer rods  96  undergo a phase transformation that results in retainer rods shortening and disengaging from recesses  95 . In some preferred embodiments, retainer rods  96  shorten to the extent that the rods become fully retracted within the retainer supports  90 .  
         [0081]     When IOL  80  is implanted into the patient&#39;s native capsule in the unaccommodated state, ribs  98  engage the capsular equator. Retainer rods  96  are allowed to remain in the elongated state during an initial period of several days to weeks, during which time fibrous tissue adheres to distal portions  92  and ribs  98 , causing arms  88  and  89  to become affixed to the capsular equator. Once distal portions  92  become adhered to the capsular equator, retainer rods  96  may be heated into the austenitic phase, for example, using a laser, RF or ultrasound energy, and shorten to release arms  88  and  89 , thereby allowing IOL  80  to accommodate responsive to movements of the ciliary muscles and capsule.  
         [0082]     Once retainer rods  96  are transformed to the reduced length state, bellows  91  are no longer held at the maximum outward extension. Accordingly, arms  88  and  89  are free to move inward under the bias of bellows  91  until constrained by the opposing forces applied by the ciliary muscles, capsule and zonules. For example, if the ciliary muscles contract, the capsular equator moves radially inward and distal portions  92  bear fully against bellows  91 . This action displaces fluid from reservoirs  93  to lens piston  84 , causing the anterior lens element to deflect to the accommodated state. When the ciliary muscles contract, the zonules pull the capsular equator to a larger diameter, thereby applying tensile forces to arms  88  and  89  that reduce the inward deflection of distal portions  92  and bellows  91 . This action causes fluid in lens piston  84  to move to reservoirs  93 , and reduces the degree of accommodation provided by IOL  80 .  
         [0083]     In a preferred embodiment, retainer rods  96  are left in the elongated state for a period selected to correspond to the expected “heal-in” period, that is, the period during which fibrous growth cause ribs  98  to become embedded in the capsular equator. Thereafter, the retainer rods are heated to release arms  88  and  89 , thereby allowing accommodating movement of lens piston  84  and anterior element  83 .  
         [0084]     As for the preceding embodiments, the volume of fluid in IOL  80  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 the IOL 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  84  and the haptic pistons may be tailored for a specific patient.  
         [0085]     As will of course be understood, optic portion  81  could instead be arranged so that the lens piston is integrated with posterior lens element  86  instead of anterior lens element  83 , and causes deflection the posterior lens element  86 ; the arrangement depicted in  FIG. 8  is illustrative only.  
         [0086]     Referring now to  FIGS. 9A-9C , a further alternative embodiment of an intraocular lens constructed in accordance with the principles of the present invention is described. IOL  100  comprises optic portion  101  and haptic portion  102 . Optic portion  101  is constructed of light transmissive materials, while haptic portion  102  is disposed at the periphery of the optic portion and does not participate in focusing light on the retina of the eye.  
         [0087]     Optic portion  101  comprises anterior lens element  103  with bellows-shaped lens piston  104 , substrate  105  and intermediate layer  106 , 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. As in the preceding embodiments, fluids having indices of refraction matched to the solid components of optic portion  101 , such as silicone or acrylic oils, are disposed within the lens piston, channels and other spaces of the lens. The side wall of lens piston  104  is configured to deflect inward responsive to pressure increases within the lens piston, which in turn deflect anterior lens element  103  to assume more convex shape, thereby changing the diopter power of the lens.  
         [0088]     The inner surface and thickness of anterior lens element  103  (relative to the optical axis of the lens) are selected so that the outer surface of anterior element  103  retains an optically corrective shape, e.g., spherical, throughout the entire range of motion of lens piston  104 , e.g., for accommodations 0-10 diopters. It should of course be understood that the inner surface and thickness of anterior lens element  103  also may be selected to provide an aspherical outer surface, as required for a desired degree of optical correction.  
         [0089]     Haptic portion  102  comprises bellows  107  and arms  108  and  109 . Preferably, arms  108  and  109  are molded of a relatively rigid polymeric material, such as polyimide, that tends to return to its undeformed shape after a deformation occurs. Other embodiments of arms  108  and  109  may comprise shape memory material, such as nickel-titanium, or may be formed from other material having elastic properties. Bellows  107  preferably are an extension of substrate  105 , and therefore preferably comprise light-transmissive materials, such as silicone or acrylic polymers or other biocompatible materials as are known in the art of intraocular lenses.  
         [0090]     Each of arms  108  and  109  comprises a groove  110  that preferably extends from outer end  111  to bellows end  112 . Arm mounting surface  113  of each of arms  108  and  109  is attached to bellows mounting surface  114  on bellows  107 , preferably by bonding. Each of arms  108  and  109  further comprises notch  115  and cleat  116 . Arms  108  and  109  extend outward some distance from optic portion  101 , such that at least some portion of arms  108  and  109  contact the equator of capsule  15 . Preferably, a portion of arms  108  and  109  near outer ends  111  remain in contact with inside wall of capsule  15  throughout the IOL&#39;s  100  full range of accommodation.  
         [0091]     As discussed in detail below, as arms  108  and  109  move toward optic portion  101 , bellows  107  contract and cause IOL  100  to accommodate. As arms  108  and  109  move away from optic portion  101 , bellows  107  expand and cause IOL  100  to transition to an unaccommodated state. In the embodiment shown in  FIG. 9 , bellows  107  assume a contracted configuration when not acted upon by outside forces, such as forces on arms  108  and  109 , thereby causing IOL  100  to be in a fully accommodated configuration. It should be recognized by one of skill in the art of intraocular lenses that IOL  100  could instead be configured to be in an unaccommodated configuration in its resting state by configuring bellows  107  to be fully expanded in the absence of outside forces.  
         [0092]     Still referring to  FIG. 9 , bellows  107  are filled with a fluid such that movement of that fluid into and out of optic portion  101  changes the degree of accommodation of IOL  100  in a similar fashion as the above embodiments. In this regard, interiors of bellows  107  are in fluid communication with the interior of lens piston  104  via channels  117  that extend from bellows  107  to well  118  disposed beneath lens piston  104 . Together, bellows  107 , channel  117 , well  118 , lens piston  104 , and fluid therein form a hydraulic system that deforms lens piston  104  responsive to movements of the ciliary muscle and the capsular bag that are transmitted through arms  108  and  109 ; these deformations of lens piston  104  in turn transition lens  100  between the accommodated and unaccommodated states.  
         [0093]     In constructing the embodiment shown in  FIG. 9  and described herein, intermediate layer  106  provides a barrier between channel  117  and anterior lens  103 . Moreover, intermediate layer  106  has opening  119  in its center to permit fluid communication between lens piston  104  and well  118 . Also, in addition to comprising bellows  107 , substrate  105  further comprises posterior lens  120 . It should be appreciated that the contacting surfaces between substrate  105  and intermediate layer  106  need not be planar, and may be curved convexly such that a failure of IOL  100  due to in a loss of fluid results in IOL  100  assuming a partially or fully accommodated state.  
         [0094]     In accordance with one aspect of the present invention, IOL  100  is configured to be placed in the capsule of a patient&#39;s eye in the unaccommodated state, with the arms  108  and  109  in an undeflected position extending outward from optic portion  101 . This configuration may be achieved by attaching suture  121  (one shown in dotted line attached to arm  109  in  FIG. 9C ) between notch  115  and cleat  116  along each of arms  108  and  109 . When attached in this manner, suture  121  resides in grooves  110 . Due to the tension placed on arms  108  and  109 , relative movement of outer ends  111  is restricted, and arms  108  and  109  may be disposed against the interior wall of capsule  15 . Optionally, barbs  122  may be disposed on arms  108  and  109  to facilitate affixation of arms  108  and  109  to the equator of capsule  15 .  
         [0095]     As shown in the enlarged portion of  FIG. 9C , one embodiment of barbs in accordance with the present invention comprises two series of barbs  122  offset from each other. Barbs  122  are protrusions that are angled such that the outward edge protrudes at an acute angle, whereas the inward edge protrudes at a steeper angle, and may exceed ninety degrees. With this configuration, barbs  122  would not inhibit proper positioning into the capsular equator, but resists inward motion away from the interior surface of the capsular wall.  
         [0096]     Sutures  121  preferably are attached prior to inserting IOL  100  into the patient&#39;s eye and may be released naturally due to a matching of resorbable characteristics to the healing period. Alternatively, the sutures could be released, for example, using a Nd:YAG laser or other known device.  
         [0097]     When IOL  100  is implanted into the patient&#39;s native capsule  15  in the unaccommodated state, barbs  122  engage the capsular equator. Sutures  121  preferably remain in place during an initial period of several days to weeks, during which time fibrous tissue adheres to barbs  122 , causing arms  108  and  109  to become affixed to the capsular equator. Preferably, sutures  121  comprise a resorbable material that disintegrates after several days to weeks, thereafter releasing arms  108  and  109  to allow IOL  100  to accommodate responsive to movements of the ciliary muscles and capsule.  
         [0098]     More specifically, once sutures  122  are released or resorbed, arms  108  and  109  are free to flex and move inward under the bias of the predetermined shape of bellows  107  until constrained by the opposing forces applied by the ciliary muscles, capsule and zonules. For example, if the ciliary muscles contract, the capsular equator moves radially inward and arms  108  and  109  move inward, thereby permitting bellows  107  to collapse. This action displaces fluid from the interior of bellows  107  to lens piston  104 , causing the anterior lens element to deflect to an accommodated state. When the ciliary muscles relax, the zonules pull the capsular equator to a larger diameter, thereby applying tensile forces to arms  108  and  109  that expand bellows  107 . This action causes fluid in lens piston  104  to move to the interior of bellows  107 , and reduces the degree of accommodation provided by IOL  100 .  
         [0099]     In a preferred embodiment, the resorbable characteristics of sutures  121  may be selected to correspond to the expected “heal-in” period, that is, the period during which fibrous growth cause barbs  122  to become embedded in the capsular equator. Thus, the sutures will naturally resorb and release arms  108  and  109 , thereby allowing accommodating movement of lens piston  104  and anterior element  103 .  
         [0100]     As for the preceding embodiment, the volume of fluid in IOL  100  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  100  may be specified during manufacture for a given patient, or may be adjusted prior to implantation of IOL  100  on a patient-by-patient basis. In this manner, the forces developed by lens piston  104  and the arms  108  and  109  may be tailored for a specific patient.  
         [0101]     As will of course be understood, optic portion  101  could instead be arranged so that the lens piston is integrated with posterior lens element  120  instead of anterior lens element  103 , and causes deflection the posterior lens element  120 ; the arrangement depicted in  FIG. 9  is illustrative only.  
         [0102]     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.