Abstract:
An intraocular lens (IOL) system includes an optic, a pair of haptics located on sides of the optic, and hinge portions at each of the optic haptic junctions. The hinge portions have stressed and non-stressed configurations. One or more restraining elements are provided to maintain the stressed state configuration of the hinge portion during implantation and during a post-operative period during which the capsular bag of the eye heals about the lens. The restraining elements are thereafter removable, preferably via a non-surgically invasive manner, e.g., via dissolution or laser light. Removal of the restraining elements allows anteriorization of the optic as the lens assumes a non-stressed configuration during accommodation. The ciliary body and lens may then interact in a manner substantially similar to the physiological interaction between the ciliary body and a healthy natural crystalline lens.

Description:
This application is a continuation of U.S. Ser. No. 10/886,847, now U.S. Pat. No. 7,503,938 filed Jul. 8, 2004, which is a continuation-in-part of U.S. Ser. No. 10/189,992, filed Jul. 5, 2002, now abandoned which is a continuation-in-part of U.S. Ser. No. 10/090,675, filed Mar. 5, 2002, now abandoned which are both incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates broadly to ophthalmic implants. More particularly, this invention relates to intraocular lenses which are focusable and allow for accommodation for near vision. 
     2. State of the Art 
     Referring to  FIG. 1 , the human eye  10  generally comprises a cornea  12 , an iris  14 , a ciliary body (muscle)  16 , a capsular bag  18  having an anterior wall  20  and a posterior wall  22 , and a natural crystalline lens  24  contained with the walls of the capsular bag. The capsular bag  18  is connected to the ciliary body  16  by means of a plurality of zonules  26  which are strands or fibers. The ciliary body  16  surrounds the capsular bag  18  and lens  24 , defining an open space, the diameter of which depends upon the state (relaxed or contracted) of the ciliary body  16 . 
     When the ciliary body  16  relaxes, the diameter of the opening increases, and the zonules  26  are pulled taut and exert a tensile force on the anterior and posterior walls  20 ,  22  of the capsular bag  18 , tending to flatten it. As a consequence, the lens  24  is also flattened, thereby undergoing a decrease in focusing power. This is the condition for normal distance viewing. Thus, the emmetropic human eye is naturally focused on distant objects. 
     Through a process termed accommodation, the human eye can increase its focusing power and bring into focus objects at near. Accommodation is enabled by a change in shape of the lens  24 . More particularly, when the ciliary body  16  contracts, the diameter of the opening is decreased thereby causing a compensatory relaxation of the zonules  26 . This in turn removes or decreases the tension on the capsular bag  18 , and allows the lens  24  to assume a more rounded or spherical shape. This rounded shape increases the focal power of the lens such that the lens focuses on objects at near. 
     As such, the process of accommodation is made more efficient by the interplay between stresses in the ciliary body and the lens. When the ciliary body relaxes and reduces its internal stress, there is a compensatory transfer of this stress into the body of the lens, which is then stretched away from its globular relaxed state into a more stressed elongated conformation for distance viewing. The opposite happens as accommodation occurs for near vision, where the stress is transferred from the elongated lens into the contracted ciliary body. 
     In this sense, referring to  FIG. 2 , there is conservation of potential energy (as measured by the stress or level of excitation) between the ciliary body and the crystalline lens from the point of complete ciliary body relaxation for distance vision through a continuum of states leading to full accommodation of the lens. 
     As humans age, there is a general loss of ability to accommodate, termed “presbyopia”, which eventually leaves the eye unable to focus on near objects. In addition, when cataract surgery is performed and the natural crystalline lens is replaced by an artificial intraocular lens, there is generally a complete loss of the ability to accommodate. This occurs because the active muscular process of accommodation involving the ciliary body is not translated into a change in focusing power of the implanted artificial intraocular lens. 
     There have been numerous attempts to achieve at least some useful degree of accommodation with an implanted intraocular lens which, for various reasons, fall short of being satisfactory. In U.S. Pat. No. 4,666,446 to Koziol et al., there is shown an intraocular lens having a complex shape for achieving a bi-focal result. The lens is held in place within the eye by haptics which are attached to the ciliary body. However, the implant requires the patient to wear spectacles for proper functioning. Another device shown in U.S. Pat. No. 4,944,082 to Richards et al., also utilizes a lens having regions of different focus, or a pair of compound lenses, which are held in place by haptics attached to the ciliary body. In this arrangement, contraction and relaxation of the ciliary muscle causes the haptics to move the lens or lenses, thereby altering the effective focal length. There are numerous other patented arrangements which utilize haptics connected to the ciliary body, or are otherwise coupled thereto, such as are shown in U.S. Pat. No. 4,932,966 to Christie et al., U.S. Pat. No. 4,888,012 to Home et al. and U.S. Pat. No. 4,892,543 to Turley, and rely upon the ciliary muscle to achieve the desired alteration in lens focus. 
     In any arrangement that is connected to the ciliary body, by haptic connection or otherwise, extensive erosion, scarring, and distortion of the ciliary body usually results. Such scarring and distortion leads to a disruption of the local architecture of the ciliary body and thus causes failure of the small forces to be transmitted to the intraocular lens. Thus, for a successful long-term implant, connection and fixation to the ciliary body is to be avoided if at all possible. 
     In U.S. Pat. No. 4,842,601 to Smith, there is shown an accommodating intraocular lens that is implanted into and floats within the capsular bag. The lens comprises front and rear flexible walls joined at their edges, which bear against the anterior and posterior inner surfaces of the capsular bag. Thus, when the zonules exert a tensional pull on the circumference of the capsular bag, the bag, and hence the intraocular lens, is flattened, thereby changing the effective power of refraction of the lens. The implantation procedure requires that the capsular bag be intact and undamaged and that the lens itself be dimensioned to remain in place within the bag without attachment thereto. Additionally, the lens must be assembled within the capsular bag and biasing means for imparting an initial shape to the lens must be activated within the capsular bag. Such an implantation is technically quite difficult and risks damaging the capsular bag, inasmuch as most of the operations involved take place with tools which invade the bag. In addition, the Smith arrangement relies upon pressure from the anterior and posterior walls of the capsular bag to deform the lens, which requires that the lens be extremely resilient and deformable. However, the more resilient and soft the lens elements, the more difficult assembly within the capsular bag becomes. Furthermore, fibrosis and stiffening of the capsular remnants following cataract surgery may make this approach problematic. 
     U.S. Pat. No. 6,197,059 to Cumming and U.S. Pat. No. 6,231,603 to Lang each disclose an intraocular lens design where the configuration of a hinged lens support ostensibly allows the intraocular lens to change axial position in response to accommodation and thus change effective optical power. U.S. Pat. No. 6,299,641 to Woods describes another intraocular lens that also increases effective focusing power as a result of a change in axial position during accommodation. In each of these intraocular lenses, a shift in axial position and an increase in distance from the retina results in a relative increase in focusing power. All lenses that depend upon a shift in the axial position of the lens to achieve some degree of accommodation are limited by the amount of excursion possible during accommodation. 
     U.S. Pat. No. 5,607,472 to Thompson describes a dual-lens design. Prior to implantation, the lens is stressed into a non-accommodative state with a gel forced into a circumferential expansion channel about the lens. At implantation, the surgeon must create a substantially perfectly round capsulorrhexis, and insert the lens therethrough. A ledge adjacent to the anterior flexible lens is then bonded 360° around (at the opening of the capsulorrhexis) by the surgeon to the anterior capsule to secure the lens in place. This approach has numerous drawbacks, a few of which follow. First, several aspects of the procedure are substantially difficult and not within the technical skill level of many eye surgeons. For example, creation of the desired round capsulorrhexis within the stated tolerance required is particularly difficult. Second, the bonding “ledge” may disrupt the optical image produced by the adjacent optic. Third, intraocular bonding requires a high degree of skill, and may fail if the capsulorrhexis is not 360° round. Fourth, the proposed method invites cautionary speculation as to the result should the glue fail to hold the lens in position in entirety or over a sectional region. Fifth, it is well known that after lens implantation surgery the capsular bag, upon healing, shrinks. Such shrinking can distort a lens glued to the bag in a pre-shrunk state, especially since the lens is permanently affixed to a structure which is not yet in equilibrium. Sixth, Thompson fails to provide a teaching as to how or when to release the gel from the expansion channel; i.e., remove the stress from the lens. If the gel is not removed, the lens will not accommodate. If the gel is removed during the procedure, the lens is only in a flattened non-accommodating shape during adhesion to the capsule, but not post-operatively, and it is believed that the lens therefore will fail to interact with the ciliary body as required to provide the desired accommodation as the capsular bag may change shape in the post-operative period. If the gel is otherwise removed thereafter, Thompson ostensibly requires an additional surgical procedure therefor. In view of these problems, it is doubtful that the lens system disclosed by Thompson can be successfully employed. 
     Thus, the prior art discloses numerous concepts for accommodating intraocular lenses. However, none are capable of providing an accommodating implant which does not, in one way or another, risk damage to the ciliary body or the capsular bag, present technical barriers, or present potential serious consequences upon failure of the device. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an intraocular lens that functions similarly to the natural crystalline lens. 
     It is another object of the invention to provide an intraocular lens that changes shape and increases power during accommodation. 
     It is also an object of the invention to provide an intraocular lens that produces a sufficient increase in focusing power such that it is clinically useful. 
     It is an additional object of the invention to provide an intraocular lens that permits uncomplicated implantation of the lens in a manner compatible with modern-day cataract surgery techniques. 
     In accord with these objects, which will be discussed in detail below, an intraocular lens (IOL) system that permits accommodation and a method of implanting such an intraocular lens system are provided. Generally, the invention includes an intraocular lens that is maintained in a stressed non-accommodating configuration during implantation into the capsular bag of the eye and maintained in the stressed configuration during a post-operative healing period during which the capsular bag heals about the lens. After the post-operative healing period, the intraocular lens is preferably atraumatically released from the stressed state and permitted to move between accommodative and non-accommodative configurations in accord with stresses placed thereon by the ciliary body and other physiological forces. 
     According to one embodiment of the invention, the intraocular lens system includes a flexible optic having a skirt (periphery or haptic), and a restraining element about the skirt and adapted to temporarily maintain the flexible optic in a stressed, non-accommodating configuration during a post-operative period. The retraining element may comprise a dissolvable bioabsorbable material such that the element automatically releases the optic after a post-operative period, or may be released under the control of a eye surgeon, preferably via a non-surgically invasive means such as via a laser or a chemical agent added to the eye. 
     According to another embodiment of the invention, the intraocular lens system includes an optic, a pair of haptics located on sides of the optic, and hinge portions at each of the optic haptic junctions. The hinge portions have stressed and non-stressed state configurations. In accord with the invention, one or more restraining elements are provided to maintain the stressed state configuration of the hinge portion during implantation and during a post-operative period. 
     Generally, the method includes (a) inducing cycloplegia; (b) providing an intraocular lens having an optic portion and haptics and having an as manufactured bias induced between the optic portion and haptics, the intraocular lens being held in a non-accommodating stressed state by a restraining means such that the intraocular lens has a lower optical power relative to an accommodating non-stressed state of the lens; (c) inserting the stressed state intraocular lens into a capsular bag of the eye; (d) maintaining cycloplegia until the capsular bag physiologically affixes to the intraocular lens; and (e) non-surgically invasively releasing the restraining means to permit the intraocular lens to move from the stressed state into the non-stressed state in which the intraocular lens has an increased optical power, and wherein the optical power of the intraocular lens is reversibly adjustable in response to stresses induced by the eye such that the lens can accommodate. 
     More particularly, according to a preferred method of implantation, the ciliary body muscle is pharmacologically induced into a relaxed stated (cycloplegia), a capsulorrhexis is performed on the lens capsule, and the natural lens is removed from the capsule. The prosthetic lens is then placed within the lens capsule. According to a preferred aspect of the invention, the ciliary body is maintained in the relaxed state for the duration of the time required for the capsule to naturally heal and shrink about the lens; i.e., possibly for several weeks. After healing has occurred, the restraining element automatically or under surgeon control releases the lens from the stressed state. The ciliary body and lens may then interact in a manner substantially similar to the physiological interaction between the ciliary body and a healthy natural crystalline lens. 
     Alternatively, a fully relaxed lens (i.e., without restraining element) can be coupled to a fully stressed and contracted ciliary body. 
     The intraocular lens system of the invention is compatible with modern cataract surgery techniques and allows for large increases in optical power of the implanted lens. Unlike other proposed accommodating intraocular lens systems, the lens described herein is capable of higher levels of accommodation and better mimics the function of the lens of the human eye. Further, unlike other lens systems previously described, the lens take into account certain reciprocal aspects of the relationship between the natural crystalline lens and the ciliary body. Moreover, the implantation is relatively easy and rapid. 
     Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a cross-section of a normal eye; 
         FIG. 2  is a graph of the stresses on the ciliary body-crystalline lens system of the eye in a continuum of states between distance vision and full accommodation; 
         FIG. 3  is a schematic front view of an intraocular lens according to the invention configured into a stressed state with a restraining element; 
         FIG. 4  is a schematic transverse section view of the intraocular lens of  FIG. 3  in a stressed state; 
         FIG. 5  is a schematic transverse section view of the intraocular lens of  FIG. 3  in a non-stressed accommodating state; 
         FIGS. 6 and 7  are other schematic transverse section views of intraocular lenses according to the invention; 
         FIG. 8  is a schematic front view of an intraocular lens according to the invention with the restraining element removed, and thus, configured in a non-stressed accommodating state; 
         FIG. 9  is a transparent front view of an intraocular lens according to the invention shown with a second embodiment of a restraining element; 
         FIG. 10  is a schematic transverse view of the intraocular lens of  FIG. 9 ; 
         FIG. 11  is a transparent front view of an intraocular lens according to the invention shown with a third embodiment of a restraining element; 
         FIG. 12  is a schematic transverse view of the intraocular lens of  FIG. 11 ; 
         FIG. 13  is a transparent front view of an intraocular lens according to the invention shown with a fourth embodiment of a restraining element; 
         FIG. 14  is a schematic transverse view of the intraocular lens of  FIG. 13 ; 
         FIG. 15  is a schematic front view of an intraocular lens according to the invention having a particular skirt configuration which include haptics and another alternate embodiment restraining element; 
         FIG. 16  is a schematic front view of another intraocular lens according to the invention having a particular skirt configuration which include haptics and yet another alternate embodiment restraining element; 
         FIG. 17  is a schematic side view of the intraocular lens of  FIG. 16 ; 
         FIG. 18  is an intraocular lens according to the invention having a particular skirt configuration which include haptics and yet a further alternate embodiment restraining element; 
         FIG. 19  is a block diagram of a first embodiment of a method of implanting an intraocular lens according to the invention; 
         FIG. 20  is a block diagram of a second embodiment of a method of implanting an intraocular lens according to the invention; 
         FIG. 21  is a block diagram of a third embodiment of a method of implanting an intraocular lens according to the invention; 
         FIG. 22  is a schematic front view of a second embodiment of an intraocular lens according to the invention, shown in a stressed configuration; 
         FIG. 23  is a schematic side view of the intraocular lens of  FIG. 22 , shown in a stressed configuration; 
         FIG. 24  is a schematic side view of the intraocular lens of  FIG. 22 , shown in a non-stressed configuration; 
         FIG. 25  is a schematic side view of the intraocular lens according to the second embodiment of the invention held in a stressed configuration with a bridge-type restraining element; 
         FIG. 26  is a schematic side view of the intraocular lens of  FIG. 25  shown in a non-stressed configuration; 
         FIG. 27  is a schematic front view of an intraocular lens according to the invention having four haptics; 
         FIG. 28  is a diagrammatic view of a cross-section of an eye having an intraocular lens according to the second embodiment of the invention implanted therein, the lens being in a stressed configuration; and 
         FIG. 29  is a diagrammatic view of a cross-section of an eye having an intraocular lens according to the second embodiment of the invention implanted therein, the lens being in a non-stressed configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to  FIG. 3 , a first preferred embodiment of an intraocular lens  100  according to the invention is shown. The lens includes a pliable optic portion  102  having an elastic memory, and is peripherally surrounded by a skirt portion  104 . A restraining element  106  is provided on the skirt portion  104  and operates to hold the skirt portion and optic portion  102  in a stressed (i.e., stretched) configuration. Comparing  FIG. 3 , showing the optic portion in a stressed configuration, with  FIG. 8 , showing the optic portion in a non-stressed configuration, it is seen that the optic portion has a smaller diameter in the non-stressed configuration. 
     More particularly, the optic portion  102  is typically approximately 5 to 6 mm in diameter and made from a silicone polymer or other suitable flexible polymer. The optic portion defines an anterior surface  110  and a posterior surface  112 . The optic portion may have a biconvex shape in which each of the anterior surface  110  and posterior surface  112  have similar rounded shapes.  FIG. 4  illustrates such a lens in a stressed non-accommodating configuration, while  FIG. 5  illustrates such a lens in the non-stressed accommodating configuration. Alternatively, referring to  FIG. 6 , the anterior surface  110   a  may be provided with a substantially greater curvature than the posterior surface  112   a . In addition, referring to  FIG. 7 , the anterior and posterior surfaces  110 ,  112  of the optic portion can be evenly pliable throughout, or, referring back to  FIG. 6 , greater flexibility and pliability can be fashioned into the central portion  114  of the anterior  110  surface of the lens to enhance the accommodating effect. This may be done by using materials of differing modulus of elasticity or by altering the thickness of the central portion and/or anterior surface  110  of the optic portion  102 . 
     Referring back to  FIG. 3 , the skirt portion  104  has substantially less pliability than the optic portion  102 . The periphery  116  of the skirt portion  104  is preferably provided with a plurality of circumferentially displaced fenestration holes  118 . The fenestration holes  118  operate to promote firm attachment of the capsular bag to the lens skirt  104  during the healing period. That is, during the healing process, the capsular bag shrinks by a substantial amount and portions of the anterior and posterior capsular bag enter into the fenestration holes  118  and join together to lock the lens  100  within the capsule without necessitating any bonding agent, sutures, or the like. Alternatively, the peripheral portion  104  could be fashioned with a textured surface, ridges or any surface modification that promotes strong adhesion of the capsule to the lens skirt  104 . 
     Referring to  FIGS. 3 and 4 , according to a preferred, though not essential, aspect of the invention, a preferably thin and pliable collar  120  is positioned around the anterior surface of lens near the junction  122  ( FIG. 8 ) of the optic portion  102  and the skirt portion  104  to keep the more central portions of the anterior capsular remnant from adhering to the optic portion. The collar is preferably made from silicone or another smooth polymer. 
     As discussed above, the skirt portion  104  is maintained in a stressed configuration by the restraining element until the restraining element is removed. According to a preferred embodiment of the restraining element, the restraining element is a band provided on the outside of the skirt portion. The band  106  is preferably comprised of a dissolvable, preferably bioabsorbable material that is adapted to preferably naturally dissolve in the fluid of the eye within a predetermined period of time after implantation. Alternatively, the dissolvable material may be selected so that it dissolves only upon the addition of a dissolving-promoting agent into the eye. Preferred dissolvable materials for the restraining band  106  include collagen, natural gut materials, glycan, polyglactin, poliglecaprone, polydioxanone, or other carbohydrate-based or protein-based absorbable material. 
     Referring now to  FIGS. 9 and 10 , according to a second embodiment of the restraining element  106   a , the restraining element comprises a circumferential channel  130   a  in the skirt  104  that is filled with a fluid or gel  132   a . Preferably an isotonic solution such as a balanced salt solution is used. Alternatively, other suitable fluids, solution, or gels, including viscoelastics can be used. The channel  130   a  has an outlet  134   a  that is blocked by a dissolvable, preferably bioabsorbable seal  136   a . The filled channel  130   a  operates to stress the optic portion  102  into a non-accommodating configuration until the seal  136   a  is dissolved and the outlet  134   a  is thereby opened. Then, the material  132   a  within the channel  130   a  is forced out of the channel by the natural elasticity of the lens and permits the lens to move in accord with the excitation state of the ciliary body; i.e., between non-accommodative and accommodative states. Alternatively, the seal material  136   a  may not be naturally dissolvable within the environment of the eye, but rather is dissolvable within the presence of a chemical agent, such as an enzyme, which can be added to the eye. In such case, the eye surgeon can non-surgically control the release of the seal. 
     Turning now to  FIGS. 11 and 12 , according to a third embodiment of the restraining element, the restraining element  106   b  comprises a circumferential channel  130   b  in the skirt portion  104  that is filled with a balanced salt solution or other suitable material  132   b  that maintains the optic portion into a non-accommodating stressed configuration. The channel  130   b  has an outlet tube  134   b  that is biased outward from the optic portion  108  but which is preferably anchored with an anchor  135   b  toward the optic portion  102  but which preferably does not overlie a central area of the optic portion which would interrupt the vision of the patient when the lens is implanted. The outlet tube  134   b  is provided with a seal  136   b  made from a material, e.g., hard silicone, polymethylmethacrylate (PMMA) or plastic, that is ablatable or otherwise able to be unsealed by laser light from a YAG laser or other laser suitable for eye surgery. Likewise, the anchor  135   b  is also made from such a material. When the lens is implanted, as discussed in detail below, the anchor  135   b  and the outlet tube  134   b , by being directed toward the optic portion  102 , is visible to the eye surgeon through a dilated iris and is positioned to receive laser light. In this embodiment, the seal  136   b  can be removed and the outlet tube  134   b  opened under the full control of the eye surgeon (at his or her discretion upon post-operative evaluation of the lens recipient) by use of a laser to remove the pressure in the channel  130   b  to equilibrate with the anterior chamber pressure of the eye. Moreover, removal of the anchor  135   b  enables the outlet tube to move away from the optic portion in accord with its bias and toward the periphery to minimize any potential interference with the patient&#39;s vision. 
     According to a fourth embodiment of the restraining element, any mechanical means for maintaining the lens in a stressed configuration can be used. For example, referring to  FIGS. 13 and 14 , a relatively stiff restraining element  132   c  having a circular form can be inserted or otherwise provided within a circumferential channel  130   c . The restraining element is made from a material designed to be ablated or broken upon receiving laser energy, e.g., hard silicone, polymethylmethacrylate (PMMA) or plastic. Alternatively, the end of the element  132   c  can be provided with a length of flexible material  134   c , e.g., suture, which can be extended to outside the eye. When it is desired to remove the restraining element, the surgeon grasps the suture with a forceps and pulls the suture. This either removes the restraining element from the lens or breaks the restraining element. In either case, the stress is released from the optic. As yet another less preferred alternative, stiff restraining element is removable or broken only upon an invasive (requiring an incision) surgical procedure. 
     Other embodiments for the restraining elements and removal thereof are possible. For example, and not by way of limitation, the seal for an inflated channel can be attached to a suture or other length of flexible material which extends outside the eye. The suture can be pulled by the surgeon to remove the seal. In yet another example, shallow shells, adapted to be dissolvable naturally or in conjunction with an additive agent, may be provided to the front and back of the optic portion to force the optic portion to adopt a flatter (i.e., stressed) configuration. By way of another example, dissolvable or laser-removable arced struts may be provided across the lens which force the optic portion into a stressed state. 
     Moreover, embodiments of the restraining element which maintain the stressed state of the optic via external flattening of the optic or by arced struts are suitable for use with a non-circumferential skirt portion; i.e., where the skirt portion is defined by a plurality of haptics extending outward from the optic portion. For example,  FIGS. 15-18 , illustrate the “skirt portion” defined by a plurality of haptics, rather than a complete ring about the optic.  FIG. 15  discloses a skirt portion  104   a  defined by three haptics  140   a , each of which preferably includes fenestration holes  118   a . Dissolvable or laser-ablatable arced struts  142   a  are situated to maintain a radial stress on the optic portion  102   a ; i.e., the struts  142   a  function together as a restraining member.  FIGS. 16 and 17  discloses a skirt defined by four haptics  140   b , each of which preferably includes fenestration holes  118   b . Shells  144   b  are coupled to the haptics anterior and posterior of the optic to flatten the optic.  FIG. 18  discloses a skirt defined by two haptics  140   c , each of which preferably includes fenestration holes  118   c . Multiple struts  142   c  are coupled to each haptic  140   c.    
     In addition, it is recognized that the optic portion may be provided in an optically transparent bag, and the bag may be pulled or otherwise forced taught to stress the optic. The bag may be pulled taught by using one of the restraining element described above, e.g., retaining rings, channels, shells, or struts, or any other suitable means, provided either directly to the bag or provided to an element coupled about a periphery of the bag. 
     Moreover, it is recognized that the lens of the invention may comprise two optic elements: one stationary and the other adapted to change shape and thereby alter the optic power of the dual optic system. In such an embodiment, the optic element adapted to change shape would be provided in a stressed-configuration, according to any embodiment described above. 
     In each embodiment of the restraining element, the restraining element is preferably configured on or in the lens during manufacture, such that the lens is manufactured, shipped, and ready for implant in a fully stressed configuration. 
     The lens is implanted according to a first method of implantation, as follows. Referring to  FIG. 19 , the patient is prepared for cataract surgery in the usual way, including full cycloplegia (paralysis of the ciliary body) at  200 . Cycloplegia is preferably pharmacologically induced, e.g., through the use of short-acting anticholinergics such as tropicamide or longer-lasting anticholinergics such as atropine. 
     An anterior capsulorrhexis is then performed at  202  and the lens material removed. A stressed lens according to the invention is selected that preferably has an optic portion that in a stressed-state has a lens power selected to leave the patient approximately emmetropic after surgery. The lens is inserted into the empty capsular bag at  204 . 
     Cycloplegia is maintained for several weeks (preferably two to four weeks) or long enough to allow the capsular bag to heal and “shrink-wrap” around the stressed and elongated lens at  206 . This can be accomplished post-operatively through the use of one percent atropine drops twice daily. As the lens shrinks, the anterior and posterior capsular bag walls enter into the fenestration holes and join together to lock the lens in position. 
     If the lens includes a restraining element having a dissolvable component, eventually the dissolvable material is lost from the lens, and the lens is unrestrained. If the lens includes a restraining element having a laser-removable component, a surgeon may at a desired time remove the component to place the lens in a unrestrained configuration. If the lens includes a retraining element which must be surgical removed or altered, the surgeon may at a desired time perform a second eye procedure to remove the component and place the lens in an unrestrained configuration. 
     Regardless of the method used, when the lens is unrestrained (i.e., released from the stressed state) at  208  and the post-operative cycloplegic medicines are stopped at  210  the lens is initially still maintained in a stressed state ( FIG. 4 ) due to the inherent zonular stress of the non-accommodating eye. When the patient begins accommodating, the zonular stress is reduced and the implanted lens is permitted to reach a more relaxed globular conformation, as shown in  FIGS. 5 and 8 . This change in shape provides the optic with more focusing power and thus accommodation for the patient is enabled. As with the natural crystalline lens, the relaxation of the implanted lens to a more globular shape is coupled with a development of strain or stress in the ciliary body during accommodation. Further, when the patient relaxes accommodation, the stress in the ciliary body is reduced, and there is a compensatory gain in stress as the lens is stretched into its non-accommodative shape (See again  FIG. 2 ). 
     Referring to  FIG. 20 , according to another embodiment of the method of the invention, a lens of similar design as described above is used, except that there is no restraining element on the lens. Temporary cycloplegia is induced, and a capsulorrhexis is performed  300 . The lens is implanted while the ciliary body is in a fully relaxed state at  302 . The patient is then fully accommodated (i.e., the ciliary body is placed in a contracted state) at  304 , preferably through pharmacological agents such as pilocarpine. 
     Once the capsular bag is fully annealed (affixed) to the lens periphery at  306 , the pharmacological agent promoting accommodation is stopped at  308 . Then, as the ciliary body relaxes, the lens is stretched into an elongated shape having less focusing power. Conversely, as accommodation recurs, the lens returns to it resting shape having greater focusing power. 
     Referring to  FIG. 21 , in yet another embodiment of the method of the invention, the patient is cyclopleged during cataract surgery at  400 , a capsulorrhexis is performed at  402 , and a flexible lens in an unstressed state is implanted in the capsular bag at  404 . After a few weeks of complete cycloplegia and during which capsular fixation of the lens periphery is accomplished at  406 , light (e.g., ultraviolet or infrared), a chemical agent, or another suitable means is used to shrink or otherwise alter the optic or the adjacent skirt of the lens while the patient is still fully cyclopleged at  408 . In this manner, the optic is again placed into a stressed configuration while the ciliary body is fully relaxed. As with previous embodiments, when cycloplegia is stopped and accommodation occurs at  410 , the lens is able to return to a more relaxed globular configuration. 
     The intraocular lens systems described with respect to  FIGS. 1 through 18  operate to provide accommodation through a change in shape in the optic resulting from an equilibrium of the anatomical forces and the forces in the lens. As now described, it is also possible to provide accommodation through axial movement of a lens within the eye, all while maintaining equilibrium between the anatomical forces and the structural stress designed into the lens. 
     Turning now to  FIG. 22 through 24 , an embodiment of another intraocular lens system according to the invention is shown. The lens  500  includes a central optic  502 , two peripheral haptics  504 , and a junction  506  between the optic  502  and the haptics  504 . The junction  506  preferably has an elastic memory such that, in a relaxed configuration of the lens  500 , free ends  505  of the haptics  504  are oriented at a posterior angle a relative to the optic  502  ( FIG. 24 ); i.e., there is a bias induced between the optic and haptics along an anterior-posterior axis A. A preferred range for angle a includes 1 to 60 degrees, with a more preferred angle a being 25 to 35 degrees. The junction  506  can be a skirt portion attached about the periphery of the optic, or can be integrated into the periphery of the optic, particularly where the optic and junction are unitarily formed as one piece from a flexible polymeric material. In addition, the junction  506  can vary in size allowing elastic bias over part or all of the haptic. For instance, the unstressed conformation of the haptic can describe an arc over all or part of its length. A restraining element  508  is preferably provided either at the junction  506  to restrain flexing at the junction ( FIGS. 22 ) or extends as a bridge from the optic  502  to the haptics  504  ( FIG. 25 ) to maintain the lens  500  in a stressed preferably substantially planar configuration during implantation and for a post-operative period. Alternatively, the stressed configuration can be any configuration of the lens in which the optic is oriented in a more posterior orientation relative to the haptic than in the non-stressed configuration. When the restraining element  508  is removed, the haptics  504  are biased toward an angled configuration relative to the optic  502 , with the optic moved anteriorly relative to the haptics ( FIG. 26 ). In accord with the above, when the lens  500  is restrained in the stressed configuration, the lens  500  has a total diameter (maximum peripheral extension from the peripheralmost end of one haptic  504  to the peripheralmost end of another haptic)( FIG. 23 ) that is larger than the total diameter of the lens when the lens is in the unrestrained unstressed configuration in which the haptics  504  bend relative to the optic  502  in accord with the bias induced along the anterior-posterior axis A ( FIG. 24 ). 
     More particularly, the optic  502  can be a flexible construction, as in the previous embodiments, or may be substantially rigid. The optic is preferably fixed in power, but may contain zones of different optic power. As such, the optic is either constructed of a suitable flexible polymer such as a silicone polymer, or a suitable stiff plastic such as polymethylmethacrylate (PMMA). The optic preferably has a diameter of approximately 4 mm to 7 mm, and most preferably approximately 5 mm. 
     The haptics  504  can be substantially planar, curved or loop-like in structure; i.e., they may generally conform to any well-known haptic structure. Moreover, as shown in  FIG. 27 , there may be more than two haptics, e.g., four haptics  504   a . Furthermore, as described with respect to the previous embodiments, the haptics  504  may be provided with any number of surface modifications, including knobs, protuberances, textures, fenestration holes, ridge, etc., that promote strong adhesion with the shrink-wrapped capsular remnant. For example, referring back to  FIGS. 25 and 26 , a peripheral ridge  510  may be provided to the haptics  504 . The ridge  510  promotes adhesion as well as forces the lens into a more posterior portion of the capsular bag upon implantation, which may be desirable. In addition, the haptics may contain portions of varying flexibility, such as a more flexible peripheral extent to promote flexion of the peripheral haptic against the capsular rim. 
     The restraining elements  508 , as described with respect to the earlier embodiments, are preferably bio-resorbable, chemically resorbable, laser-removable, or surgically removable. Any restraining element that is removable in the one of the above listed manners or in any other relatively atraumatic manner and which provides the necessary function of maintaining the lens in a relatively planar stressed configuration during implantation and during a post-operative period can be similarly used. 
     The lens  500  is implanted as described above. That is, cycloplegia is induced, an anterior capsulorrhexis is performed and the lens material removed. Referring to  FIG. 28 , the lens, in a stressed, substantially planar configuration is inserted into the empty capsular bag. Cycloplegia is maintained long enough to allow the capsular bag to heal, “shrink-wrap”, and fibrose around the stressed lens. After the bag has healed, cycloplegia is terminated and the restraining element (not shown in  FIG. 28 ) is removed. 
     Referring to  FIG. 29 , with the lens unrestrained, the optic  502  of the lens  500  is able to move anteriorly forward during accommodation and increase the focusing power of the eye. The optic  502  moves forward for at least two reasons. First, with accommodation, the stress in the ciliary body  16  is increased causing constriction of the ciliary body, and resultant reduced tension on the zonules  26 . This allows bending of the haptic-optic junction  506  back to its relaxed non-planar configuration. Second, during accommodation there is anterior movement of the ciliary body  16 . 
     Then, when the patient relaxes accommodation, the stress in the ciliary body  16  is reduced and the ciliary body dilates and moves posteriorly. There is a compensatory gain in stress across the optic-haptic junction  506  as the junction is bent against its memory into a more planar configuration and the optic  502  moves posteriorly (See again  FIG. 28 ). 
     In addition, as discussed above with respect to the first embodiment, a photoreactive intraocular lens may be implanted in an unstressed state. After capsular fixation of the lens, light (e.g., ultraviolet or infrared), a chemical agent, or another suitable means is used to alter the optic into a stressed configuration while the ciliary body is fully relaxed. Then, when cycloplegia is stopped and accommodation occurs, the lens is able to return to non-stressed configuration in which the lens is located anteriorly relative to the haptic portion. 
     Moreover, as also discussed above with respect to the first embodiment, the lens can be implanted in the eye in a non-stressed configuration, and the ciliary can be pharmacologically induced to contract during the healing period. After healing, pharmacological inducement of ciliary contraction is stopped, and the lens operates in the same manner as described above. 
     There have been described and illustrated herein several embodiments of an intraocular lens and methods of implanting the same into an eye. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while two particular states of intraocular lenses (fully stressed and fully accommodating) have been disclosed, it will be appreciated that there is a continuum of states of stress that can be fashioned in the inserted lens that would be appropriate for any given state of the ciliary body. In addition, while particular types of materials have been disclosed for the lens, the dissolving material, and a viscoelastic material (where used), it will be understood that other suitable materials can be used. Also, while exemplar pharmacological agents are disclosed for maintaining a state of the ciliary body, it is understood that other agents can be used. Furthermore, while the skirt has been shown comprised of two to four haptics, it is recognized that a single haptic or five or more haptics may be utilized. Moreover, while the restraining struts and shells have been described with respect to skirts comprising haptics, it will be appreciated that the restraining struts and shells can be used with a circular skirt, as described with respect to the preferred embodiments. In addition, while in the second embodiment the optic-haptic junction is stated to preferably have a memory, it is appreciated that other means may be employed to cause the haptics to assume a non-stressed angle configuration relative to optic. For example, an elastic membrane or struts may connect the free ends of the haptics to urge the free ends toward each other and consequently the optic forward. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.