Patent Publication Number: US-2005137703-A1

Title: Accommodative intraocular lens

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
      This application is a continuation-in-part of U.S. patent application Ser. No. 10/474,988, filed Oct. 16, 2003, entitled “INTRAOCULAR LENS SYSTEM,” by Jin Hui Shen, the disclosure of which is hereby incorporated herein by reference in its entirety, which status is pending and itself claims the benefit, pursuant to 35 U.S.C. §119(e), of provisional U.S. patent application Ser. No. 60/284,359, filed Apr. 17, 2001, entitled “INTRAOCULAR LENS SYSTEM,” by Jin Hui Shen, which is incorporated herein by reference in its entirety. This application also claims the benefit, pursuant to 35 U.S.C. § 119(e), of provisional U.S. patent application Ser. No. 60/527,399, filed Dec. 5, 2003, entitled “ACCOMMODATIVE INTRAOCULAR LENS,” by Jin Hui Shen, which is incorporated herein by reference in its entirety. 
    
    
      Some references, which may include patents, patent applications and various publications, are cited and discussed in the description of this invention. The citation and/or discussion of such references is provided merely to clarify the description of the present invention and is not an admission that any such reference is “prior art” to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference. In terms of notation, hereinafter, “[n]” represents the nth reference cited in the reference list. For example, [22] represents the 22nd reference cited in the reference list, namely, Shen J H, O&#39;Day D M: Designing of an Accommodative Intraocular Lens. Invest Ophthalmol Vis Sci 43(Suppl):402. 2002.  
     FIELD OF THE INVENTION  
      The present invention generally relates to an intraocular lens, and in particular to an accommodative intraocular lens.  
     BACKGROUND OF THE INVENTION  
      Accommodation, or a change in the focus of the human lens, is a consequence of the ability of the lens to change its shape by contracting the capsule. This contraction function is what normally changes the shape of lens capsule in response to the need to accommodate.  
      The crystalline lens is one of the main optical elements in human vision. It provides the focus adjustment function in the eye. As shown in  FIGS. 1A and 1B  from reference [1], the lens  100  has a capsule  102  and lens substance  104 . The lens  100  is suspended by zonules  106  from the ciliary processes  108 . Normally, when the lens  100  is at a non-accommodating condition as shown in  FIG. 1A , which means the eye is focused at a distance, the ciliary muscle  108  is at a relaxed condition. The shape of the lens  100  is relatively flat, which is determined by its own natural elasticity, and the lens  100  now has a lower focal power. When the eye looks at objects a short distance away as shown in  FIG. 1B , however, the ciliary muscle  108  contracts, and the lens  100  tends to accommodate. For this to happen, the lens  100  has to increase its thickness. Correspondingly, there are a decrease in the diameter of the lens  100  and a decrease in the anterior and posterior surface radii, which are determined by the natural shape of capsule  102 . As shown in  FIG. 1B , in the act of accommodation, the anterior surface of the lens  100  becomes more convex axially, and the posterior surface of the lens  100  also becomes more convex. Consequently, a higher focal power for the lens  100  is created. The parameter changes during lens accommodation are listed in Table 1 [2].  
               TABLE 1                          Lens parameter changes with accommodation.                                 Unaccommodated   Accommodated               condition   condition   Reference                                                 Refracting power   +19.11   D   +33.06   D   [1]       Focal length   43.707   mm   33.785   mm   [2]           69.908   mm   40.416   mm       Radius of lens surface   11.62   mm   6.90   mm   [3]           12   mm   5.0   mm       Thickness of the lens   3.66   mm   4.24   mm   [3]           3.84   mm   4.20   mm                                         Lens equatorial   15 yr.   9   mm   8   mm   [4]       diameter   43 yr.   10.4   mm   9.4   mm       (lens from   63 yr.   10.8   mm   9.8   mm       different age)                  
 
      As people age, the amplitude of accommodation is gradually reduced due to changes in the lenticular factors such as a decrease in the elasticity modulus of the capsule, an increase in the elasticity modulus of the lens substance, a flattening of the lens, or a combination of them.  FIG. 2 , by Fincham [3], shows presbyopic changes in the amplitude of accommodation due to changes with age in the lens.  
      When a person ages, the substance of the person&#39;s natural lens gradually hardens, and may lose its accommodation function. Additionally, the person&#39;s vision is also reduced by cataract formation. Cataract surgery is then necessary to restore vision.  
      In modern cataract surgery, the cataractous substance of the lens is removed through an opening in the lens capsule. The now empty capsule of the lens is retained. The surgeon then replaces the lens contents with an artificial lens, which is positioned in the empty capsule. A typical procedure for a cataract surgery includes providing an opening at limbus, removal of the front portion of the lens capsule, ultrasonic fragmentation of the hard lens substance (nucleus), and implantation of an artificial intraocular lens.  
      Intraocular lenses (hereinafter “IOL”) are high optical quality lenses made of synthetic material such as Polymethylmethacrylate (Acrylic) (hereinafter “PMMA”), silicone, hydrogel or the like. The diameter of an IOL is normally 5 to 7 mm, and the lens dioptric power is matched to the need of the patient. Each IOL has two spring-like haptics, or loops, attached to the optic. When the IOL is inserted inside the lens capsule, the haptics help to position the optic lens in the center. Haptics material are PMMA, polypropylene, or polyamide. There are varieties of haptics designs among different IOLs. Some of the configurations are shown in  FIG. 3 . For examples, IOL  301  has optic  302  and haptics  304 , where haptics  304  are J-shaped loops. Moreover, IOL  311  has haptics that are C-shaped loops, IOL  321  has haptics that are lone J-shaped loops, and IOL  331  has haptics that are closed loops.  
      Visual function following cataract and IOL implant surgery generally is good. However, among other things, a major disadvantage is the loss of accommodative capability that a natural lens can offer because the artificial intraocular lens has a fixed focusing power.  
      Previous research by R. F. Fisher [4] has showed that after extraction of the cataractous lens contents, the lens capsule still retains a certain level of the accommodative capability.  
      Efforts have been made to restore accommodation after cataract and implant surgery, which can be divided into the following categories:  
      1) Refill the lens with a synthetic material. This technique was first introduced by Kessler [7]. Efforts have been continued to improve the technology around the world, for examples, by a research group at Bascom Palmer Eye Institute, University of Miami, Fla. [8], and a research group in Japan [9, 10]. The normal procedure for this technique includes the steps of removing the crystalline lens through a small anterior capsular hole, and refilling the capsular bag with either precured silicone gel, or an inflatable endocapsular balloon. All of these studies showed that the refilled lens recovered accommodation to some extent, but the amount was not sufficient to be clinically useful. 2) Bifocal or multifocal intraocular lens. Bifocal or multifocal IOLs were first introduced clinically in 1987 by Keates et al. [11] . Currently, several different types of multifocal IOL have been developed, including the multizone bifocal lens [12, 13], the aspherical multifocal IOL [14], and the diffractive multifocal IOL [15-18]. Nevetheless, these IOLs can only give a patient two focus points and/or a limited focus range, and at each focus point, the patient can only get half of the incoming light energy. Consequently, at each focus distance, the images the patient has are blurry.  
      3) Accommodative intraocular lens. Several groups have been working along this line of research. For examples, one is in Japan [6, 19], and the other in the Netherlands [20]. In both studies, a movable optical lens is utilized in the direction of the axis of the eye, which is controlled by the ciliary muscle. While there was a limited amount of accommodative function shown, again no full accommodation was restored.  
      Recently, an accommodative IOL was proposed by Oliver Findl, M.D., of Vienna, Austria and published in Eye World in July 2000 [21]. As shown in  FIG. 4 , in Dr. Findl&#39;s IOL design, a fixed focus lens  402  is held by two pieces  404 ,  406  of ridged plastic holder, and the connection  408  between each plastic holder  404  or  406  and the lens  402  is flexible. When the ciliary muscle contracted, the IOL  400  will move forward. By this design, up to 2.5 D of the accommodation has been achieved. Still, no full scale of accommodation is available.  
      Shen and O&#39;Day have designed an accommodative IOL [22]. It consists of six or eight eccentrically overlapped Gaussian lenses that are fixed on an elastic zigzag thin wire frame. The dimension of each Gaussian lens is about 6 mm in diameter and 100 μm in thickness. When ciliary muscle and the lens capsule contracts, it pushes the Gaussian lenses move toward concentric direction, thus create accommodation effect. In vitro test of this IOL in a simulated ocular environment has demonstrated that 0.8 mm change of the outer diameter could induce 1.1 mm focus distance change at the simulated retina position. However, the design of this IOL seems complicated.  
      Therefore, a heretofore unaddressed need still exists in the art to address the aforementioned deficiencies and inadequacies.  
     SUMMARY OF THE INVENTION  
      In one aspect, the present invention relates to an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the accommodative intraocular lens includes a lens structure having a center of geometry, an inner surface defining a volume, an outer surface, a thickness defined therebetween the inner surface and the outer surface, and an edge, and a frame having a center of geometry, a plurality of inner ends and a plurality of outer ends. The plurality of inner ends of the frame are attached to the edge of the lens structure at a plurality of positions, respectively, such that the center of geometry of the frame overlaps substantially with the center of geometry of the lens structure. The plurality of outer ends of the frame are attached to an equator portion of the lens capsule at a plurality of positions, respectively. The volume of the lens structure is filled with an optically transparent liquid. The optically transparent liquid, in one embodiment, has a liquid gel.  
      The lens structure and the frame are adapted such that the lens structure has a contraction force directing inwardly to the center of geometry of the lens structure and the frame has an expansion force directing outwardly from the center of geometry of the frame, and when the lens capsule relaxes, the frame pulls the lens structure to be in a first state with an effective focal power, and when the lens capsule contracts and presses the fame inwardly to the center of geometry of the frame, the motion of the frame causes the lens structure to move inwardly to the center of geometry of the lens structure from the first state to a second state with an effective focal power that is different from the effective power of the lens structure at the first state. In one embodiment, the effective power of the lens structure at the second state is greater than the effective power of the lens structure at the first state.  
      The lens structure of the accommodative intraocular lens, in one embodiment, is convex. The edge of the lens structure is substantially circular. Each of the inner surface and the outer surface of the lens structure has a variable curvature and a projected geometric configuration of a circle. In one embodiment, the thickness of the lens structure is uniform. In another embodiment, the thickness of the lens structure is non-uniform. In one embodiment, the lens structure is made of an elastic silicone rubber. The elastic silicone rubber includes one of an elastomeric polydimethylsiloxane and a hydrogel.  
      The frame of the accommodative intraocular lens includes a structure that is symmetrical to the center of geometry of the frame. In one embodiment, the frame has a closed-loop structure. The closed-loop frame includes an elastic thin wire ring in a shape adapted for fitting to the equator portion of the lens capsule. In another embodiment, the frame has an open-loop structure.  
      In another aspect, the present invention relates to an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the accommodative intraocular lens includes a lens structure. The lens structure has a center of geometry, an inner surface defining a volume, an outer surface, a thickness defined therebetween the inner surface and the outer surface, and an edge. In one embodiment, the lens structure is convex. Each of the inner surface and the outer surface of the lens structure has a variable curvature and a projected geometric configuration of a circle. The thickness of the lens structure is either uniform or variable. The edge of the lens structure is substantially circular. In one embodiment, the lens structure is made of an elastic silicone rubber. The elastic silicone rubber includes one of an elastomeric polydimethylsiloxane and a hydrogel.  
      The accommodative intraocular lens further includes a ball lens. The ball lens has a center of geometry and a predetermined diameter, r, and is positioned in the volume of the lens structure with its center of geometry substantially overlapping with the center of geometry of the lens structure, where the rest of the volume of the lens structure is filled with a first gel. The ball lens includes a solid lens. In one embodiment, the ball lens is formed with a second gel that is harder than the first gel, where the first gel comprises an optically transparent liquid gel.  
      Additionally, the accommodative intraocular lens includes a frame having a center of geometry, a plurality of inner ends and a plurality of outer ends, where the plurality of inner ends of the frame are attached to the edge of the lens structure at a plurality of positions, respectively, such that the center of geometry of the frame overlaps substantially with the center of geometry of the lens structure, and the plurality of outer ends of the frame are attached to an equator portion of the lens capsule at a plurality of positions, respectively. The frame includes a structure that is symmetrical to the center of geometry of the frame. In one embodiment, the frame has a closed-loop structure. The closed-loop frame includes an elastic thin wire ring in a shape adapted for fitting to the equator portion of the lens capsule. In another embodiment, the frame has an open-loop structure.  
      In one embodiment, the lens structure and the frame are adapted such that the lens structure has a contraction force directing inwardly to the center of geometry of the lens structure and the frame has an expansion force directing outwardly from the center of geometry of the frame, and when the lens capsule relaxes, the frame pulls the lens structure to be in a first state with an effective focal power, and when the lens capsule contracts and presses the fame inwardly to the center of geometry of the frame, the motion of the frame causes the lens structure to move inwardly to the center of geometry of the lens structure from the first state to a second state with an effective focal power that is different from the effective power of the lens structure at the first state. The ball lens is adapted for modifying the geometry of the lens structure so as to adjust the effective focal power of the lens structure at the first state and the second state, respectively. In one embodiment, the effective power of the lens structure at the second state is less than the effective power of the lens structure at the first state.  
      In yet another aspect, the present invention relates to an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the accommodative intraocular lens includes a lens structure having a geometry and a focal power associated with the geometry, the lens geometry being changeable in response to a force applied to the lens structure, and means for engaging the lens structure with the lens capsule of the eye of the living subject such that contraction of the lens capsule pushes the lens structure contracting inwardly and relaxation of the lens capsule pulls the lens structure extending outwardly so as to change the geometry of the lens structure to adjust the focal power of the lens structure accordingly.  
      In one embodiment, the lens structure has an inner surface defining a volume, an outer surface, a thickness defined therebetween the inner surface and the outer surface, and an edge, where the volume of the lens structure is filled with a liquid gel. In one embodiment, the engaging means has an elastic thin wire ring. In another embodiment, the engaging means comprises a silicone rubber flat ring having a plurality of hooks. In an alternative embodiment, the engaging means comprises a plurality of ridge bars.  
      In a further aspect, the present invention relates to an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the accommodative intraocular lens includes a lens structure defining a volume, the volume filled with an optical transparent liquid, and a ring frame engaging the lens structure at an edge with a radius at a plurality of positions and the lens capsule at an equator at a plurality of positions.  
      In yet a further aspect, the present invention relates to a method of constructing an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the method includes the steps of forming a lens structure having a geometry and a focal power associated with the geometry, the lens geometry being changeable in response to a force applied to the lens structure, forming a frame, and engaging the frame with the lens structure and the lens capsule of the eye of the living subject such that contraction of the lens capsule pushes the lens structure contracting inwardly and relaxation of the lens capsule pulls the lens structure extending outwardly so as to change the lens geometry of the lens structure to adjust the focal power of the lens structure accordingly.  
      In one embodiment, the step of forming a lens structure comprises the step of forming a first film and a second film, each of the first film and the second film having an edge, attaching the edge of the first film to the edge of the second film to form a volume therebetween the first film and the second film, and filling a gel into the volume. In one embodiment, the first film and the second film are made of an elastic silicone rubber, where the elastic silicone rubber comprises one of an elastomeric polydimethylsiloxane and a hydrogel. The gel includes a liquid gel.  
      These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a perspective view of (A) an unaccommodated lens, and (B) an accommodated lens, both of them in the prior art.  
       FIG. 2  shows a chart of presbyopic changes in the amplitude of accommodation due to changes with age in the lens.  
       FIG. 3  shows several configurations of the IOL in the prior art.  
       FIG. 4  shows an accommodative IOL in the prior art.  
       FIG. 5  shows an accommodative IOL according to one embodiment of the present invention: (A) a cross-sectional view of a lens structure in a first state, (B) a cross-sectional view of the lens structure in a second state, and (C) a top view of the accommodative IOL.  
       FIG. 6  shows an accommodative IOL according to another embodiment of the present invention: (A) a cross-sectional view of a lens structure in a first state, (B) a cross-sectional view of the lens structure in a second state, and (C) a top view of the accommodative IOL.  
       FIG. 7  shows an accommodative IOL according to an alternative embodiment of the present invention: (A) a cross-sectional view of the accommodative IOL with a lens structure in a first state, (B) a cross-sectional view of the accommodative IOL with the lens structure in a second state, and (C) a top view of the accommodative IOL.  
       FIG. 8  shows a cross-sectional view of the accommodative IOL according to one embodiment of the present invention.  
       FIG. 9  shows an accommodative IOL according to another embodiment of the present invention: (A) a cross-sectional view of the accommodative IOL with a lens structure in a first state, and (B) a cross-sectional view of the accommodative IOL with the lens structure in a second state.  
       FIG. 10  shows an accommodative IOL according to a different embodiment of the present invention: (A) a cross-sectional view of the accommodative IOL with a lens structure in a first state, (B) a cross-sectional view of the accommodative IOL with the lens structure in a second state, and (C) a top view of the accommodative 5  IOL.  
       FIG. 11  shows a top view of an accommodative IOL according to an alternative embodiment of the present invention.  
       FIG. 12  shows schematically a process of fabricating a lens structure according to one embodiment of the present invention: (A) forming a first film and a second film by a lens fabrication station, and (B) attaching the first film to the second film to form a volume and injecting an optically transparent liquid to the volume to form a lens structure.  
       FIG. 13  shows a device for simulating an accommodative effect of an accommodative IOL according to one embodiment of the present invention: (A) a cross-sectional view of the device, (B) a cross-sectional view of an iris diaphragm portion of the device, and (C) a perspective view of a tweezer as shown in  FIG. 13B .  
       FIG. 14  shows in vitro simulation of the accommodation function of an eye: (A) a diaphragm having a plurality of tweezers attached, (B) a posterior view of an animal eye clamped to the diaphragm, and (C) a anterior view of an animal eye clamped to the diaphragm.  
       FIG. 15  shows the in vitro simulation of the accommodation function of an eye shown in  FIG. 14 , by adjusting the diameter of the diaphragm: (A) and (B) the in vitro simulation results for two different diameters of the diaphragm.  
       FIG. 16  shows accommodative IOLs and simulation of the accommodation function of the accommodative IOLs according to one embodiment of the present invention: (A) a single Gaussian lens, (B) an accommodative IOL formed with 8 Gaussian lenses, (C) an accommodative IOL formed with 6 Gaussian lenses, (D) an customized IOL implanted into a lens capsule, (E) the IOL of  FIG. 16C  squeezed into a small diameter, and (F) the IOL of  FIG. 16C  extended into a large diameter.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Various embodiments of the invention are now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.  
      The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings 1-16. In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to an accommodative IOL for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. The living subject can be a human being or an animal. Among other things, one unique feature of the present invention is the utilization of geometrical changes of the lens capsule of the living subject to adjust a focal power of an accommodative IOL implanted in the lens capsule. In one embodiment, the accommodative IOL includes a lens structure having a geometry and a focal power associated with the geometry, where the lens geometry is changeable in response to a force applied to the lens structure, and means for engaging the lens structure with the lens capsule of the eye of the living subject such that contraction of the lens capsule pushes the lens structure contracting inwardly and relaxation of the lens capsule pulls the lens structure extending outwardly so as to change the geometry of the lens structure to adjust the focal power of the lens structure accordingly.  
      Referring in general now to  FIGS. 5-9 , and in particular to  FIG. 5  first, an accommodative IOL  500  for implantation in an eye of a living subject in one embodiment has a lens structure  510 . As shown in  FIGS. 5A and 5B , the lens structure  510  has a center of geometry  512 , an inner surface  514  defining a volume  515 , an outer surface  516 , a thickness  518  defined therebetween the inner surface  514  and the outer surface  516 , and an edge  511 . The lens structure  510 , in one embodiment, is in the form of a lens bag that is convex. Each of the inner surface  514  and the outer surface  516  of the lens structure  510  has a variable curvature and a projected geometric configuration of a circle, and the edge  511  of the lens structure  510  is substantially circular. In the embodiment shown in  FIGS. 5A and 5B , the thickness  518  of the lens structure  510  is non-uniform: the thickness at the edge  511  is thicker than the thickness at the middle  505  of the lens structure  510 . The thickness  518  of the lens structure  510  can be varied or variable when the lens structure  510  is made of an elastic material and subject to an applied force. The thickness can also be uniform (not shown). In one embodiment, the volume  515  of the lens structure  510  is filled with an optically transparent liquid. The optically transparent liquid can be a liquid gel, such as a silicone gel, which has a high viscosity index, a high optical transparency and a high refractive index. Other liquid gels can also be used to practice the current invention. The lens structure  510  has an effective focal power that is associated with its geometry.  
      In one embodiment, the lens structure  510  is made of an elastic silicone rubber, which allows the lens structure  510  to change its geometry in response to a force applied to the lens structure and therefore adjust its effective focal power. Material like elastomeric polydimethylsiloxane (hereinafter “PDMS”), for example, Dow Coming Sylgard 184, (Dow Coming Corp., Midland, Mich.), can be used to fabricate the lens structure  510 . Other material such as hydrogel, can also be employed to form the lens structure  510 .  
      Furthermore, the accommodative IOL  500  has a frame  520 . In one embodiment, as shown in  FIG. 5C , the frame  520  has a center of geometry  522 , a plurality of inner ends  524  and a plurality of outer ends  526 , where the plurality of inner ends  524  of the frame  520  are attached to the edge  511  of the lens structure  510  at a plurality of positions  517 , respectively, such that the center of geometry  522  of the frame  520  overlaps substantially with the center of geometry  512  of the lens structure  510 . The plurality of outer ends  526  of the frame  520  are attached to an equator portion  590  of the lens capsule at a plurality of positions  597 , respectively. The frame  520  is elastic and adapted to be in contact with and responsive to the lens capsule of the eye of the living subject. In one embodiment, the frame  520  includes an elastic thin wire ring in a shape adapted for fitting to the equator portion of the lens capsule. For the embodiment shown in  FIG. 5C , the frame  520  is a closed-loop structure that has a multi inner ends  524  and outer ends  526 . One advantage of the structure of the multi inner ends and outer ends is that it allows less contact between the frame  520  and the lens capsule of the eye, which may be more suitable to people having sensitive eyes, for instance. For this embodiment, the frame  520  may be considered as a closed-loop, zigzag structure.  
      The lens structure  510  and the frame  520  of the accommodative IOL  500  are adapted such that the lens structure  510  has a contraction force  550  directing inwardly to the center of geometry  512  of the lens structure  510  and the frame  520  has an expansion force  560  directing outwardly from the center of geometry  522  of the frame  520 . When the lens capsule relaxes, the frame  520  pulls the lens structure  510  to be in a first state with an effective focal power, where the edge  511  of the lens structure  510  has a radius, R 1 , as shown in  FIG. 5A . When the lens capsule contracts and presses the fame  520  inwardly to the center of geometry  522  of the frame  520 , the motion of the frame  520  causes the lens structure  510  to move inwardly to the center of geometry  512  of the lens structure  510  from the first state to a second state with an effective focal power that is different from the effective power of the lens structure at the first state. In the second state of the lens structure  510 , as shown in  FIG. 5B , the radius of the edge  511  of the lens structure  510  is R 2  that is less than R 1 . As a result, the effective power of the lens structure at the second state is greater than the effective power of the lens structure at the first state, which allows the accommodative IOL  500  to be able to offer accommodation.  
      Both the lens structure  510  and the frame  520  of the accommodative IOL  500  can have various configurations. For examples, the lens structure can have different profiles and geometries. In one embodiment, the frame can be an annular or ring structure. In another embodiment, the frame can be a multi-round-cornered structure. Alternatively, the frame can be an open-loop structure. Several configurations available to the lens structure  510  and the frame  520  of accommodative IOL  500  will be discussed in more detail below in connection with embodiments of the present invention as shown in  FIGS. 6-9 .  
      Referring now to  FIG. 6 , an accommodative IOL  600  for implantation in the lens capsule of an eye of a living subject in one embodiment has a lens structure  610  having a center of geometry  612 , an inner surface  614  defining a volume  615 , an outer surface  616 , a thickness  618  defined therebetween the inner surface  614  and the outer surface  616 , and an edge  611 . The lens structure  610  has an effective focal power that is associated with geometry of the lens structure  610 . In one embodiment, the lens structure  610  is in the form of a convex lens bag, where each of the inner surface  614  and the outer surface  616  of the lens structure  610  has a variable curvature and a projected geometric configuration of a circle, and the edge  611  of the lens structure  610  is substantially circular. In the embodiment shown in  FIGS. 6A and 6B , the thickness  618  of the lens structure  610  is non-uniform: the thickness  618  at the edge  611  is thicker than the thickness at the middle  605  of the lens structure  610 . The thickness can also be uniform (not shown). The lens structure  610  is geometrically changeable in response to a force applied to the lens structure  610 . The thickness can be variable in response to a force applied to the lens structure  610  as well.  
      The accommodative IOL  600  further has a ball lens  630 . The ball lens  630  has a center of geometry  632  and a predetermined diameter, r, and is positioned in the volume  615  of the lens structure  610  with its center of geometry  632  substantially overlapping with the center of geometry  612  of the lens structure  610 , as shown in  FIGS. 6A and 6B . The ball lens  630  is a solid lens and formed with a gel. The rest of the volume  615  of the lens structure  610  is filled with an optically transparent liquid gel that is softer than the gel forming the ball lens  630 . The ball lens  630  is adapted for modifying the geometry of the lens structure  610  so as to adjust the effective focal power of the lens structure  610 .  
      Moreover, the accommodative IOL  600  has a frame  620  having a center of geometry  622 , a plurality of inner ends  624  and a plurality of outer ends  626 , wherein the plurality of inner ends  624  of the frame  620  are attached to the edge  611  of the lens structure  610  at a plurality of positions  617 , respectively, such that the center of geometry  622  of the frame  620  overlaps substantially with the center of geometry  612  of the lens structure  610 , and the plurality of outer ends  626  of the frame  620  are attached to an equator portion  690  of the lens capsule at a plurality of positions  697 , respectively.  
      The lens structure  610  and the frame  620  of the accommodative IOL  600  are adapted such that the lens structure  610  has a contraction force  650  directing inwardly to the center of geometry  612  of the lens structure  610  and the frame  620  has an expansion force  660  directing outwardly from the center of geometry  622  of the frame  620 , respectively. When the lens capsule relaxes, the frame  620  pulls the lens structure  610  to be in a first state, as shown in  FIG. 6A , where the edge  611  of the lens structure  610  is sized with a radius, R 1 , and the len shape of the accommodative IOL  600  is determined by the ball lens  630 . When the lens capsule contracts and presses the fame  620  inwardly to the center of geometry  622  of the frame  620 , the motion of the frame  620  causes the lens structure  610  to move inwardly to the center of geometry  612  of the lens structure  610  from the first state to a second state, where the radius of the edge  611  of the lens structure  610  decreases to R 2 , and the lens shape of the accommodative IOL  600 , which is determined by the lens structure  610 , changes accordingly to the configuration as shown in  FIG. 6B . Accordingly, the effective power of the lens structure at the second state is less than the effective power of the lens structure at the first state.  
      Referring to  FIG. 7 , an accommodative IOL  700  for implantation in an eye of a living subject having a lens capsule  795  and a lens substance contained in the lens capsule  795  is shown according to another embodiment of the present invention. In the embodiment shown in  FIG. 7 , the accommodative IOL  700  includes a lens structure that is in the form of a convex lens bag  710 . The convex lens bag  710  defines a volume  715  that is filled with an optically transparent liquid or gel of high optical index. The convex lens bag  710  has a circular edge  711 . A flat ring frame  720  extending outwardly from the circular edge  711  of the convex lens bag  710  at a predetermined shape is adapted for fitting to the lens capsule  795  and being responsive to the lens capsule  795  of the eye of the living subject, as shown in  FIG. 7A . The flat ring  720  has a plurality of hooks  728  at predetermined positions. The plurality of hooks  728  of the flat ring  720  are stuck into the lens capsule  795  at the equator area  790  such that the stretching of the ciliary muscle surrounding the lens capsule  795  pulls the accommodative IOL  700  extending outwardly through the lens capsule  795  and the contraction of the ciliary muscle surrounding the lens capsule  795  pushes the accommodative IOL  700  contracting inwardly through the lens capsule  795  and therefore the radius of the edge  711  of the convex lens bag  710  is changed. Accordingly, the focal power of the convex lens bag  710  is adjusted. The flat ring frame  720  can be made of a silicone rubber, and the plurality of hooks  728  of the flat ring frame  720  can be made of relative ridged material.  
      The ring frame  720  extending outwardly from the circular edge  711  of the convex lens bag  710  of the accommodative IOL  700  can be formed in a different shape. For example, in an embodiment shown in  FIG. 8 , a ring frame  820  of an accommodative IOL  800  is formed in a cone shape. The accommodative IOL  800  is implanted in a lens capsule of an eye of a living subject by attaching the ring frame  820  to the lens capsule. In practice, when the lens capsule  890  of an eye of a living subject is stretched outwardly in direction  860  into a bigger diameter, the lens bag  810  will be pulled forward in direction  880 . As a result, a distance between the accommodative IOL  800  and an object (not shown here) to be focused is changed, and therefore the effective focal power of the accommodative IOL  800  is adjusted accordingly.  
       FIG. 9  shows an another embodiment of an accommodative IOL  900 , where a silicone lens bag  910  has an anterior wall  918   a  and a posterior wall  918   b  defining a volume  915 , and the anterior wall  918   a  and the posterior wall  918   b  are formed in different profiles, in which the posterior wall  918   b  of the silicone lens bag  910  is curved, the anterior wall  918   a  of the silicone lens bag  910  is flat, and the posterior wall  918   b  of the silicone lens bag  910  is thicker than the anterior wall  918   a  of the silicone lens bag  910 . The lens bag  910  has a thickness  940 , d 1 , defined therebetween a center of the anterior wall  918   a  and a center of the posterior wall  918   b.  As shown in  FIG. 9A , when the silicone lens bag  910  is at its smaller diameter, both the anterior wall  918   a  and the posterior wall  918   b  of the silicone lens bag  910  tend toward posterior in direction  980   b.  The silicone lens bag  910  is thicker and has an effective focus power. When the ciliary muscle surrounding the lens capsule  995  of the eye pulls the lens capsule  995 , the movement of the lens capsule  995  in direction  960  causes the accommodative IOL  900  implanted into the lens capsule  995  to extend into a bigger diameter. Accordingly, both the anterior wall  918   a  and the posterior wall  918   b  of the silicone lens bag  910  move forward in direction  980   a.  The posterior wall  918   b  of the silicone lens bag  910  becomes flatter, while the anterior wall  918   a  of the silicone lens bag  910  becomes convex. The thickness  940  of the silicone lens bag  910  for this state d 2 , is less than d 1 , as shown in  FIG. 9B . The silicone lens bag  910  has a lower focal power in this state shown in  FIG. 9B  than that of the state shown in  FIG. 9A .  
       FIG. 10  shows an alternative embodiment of an accommodative IOL  1000  for implantation in an eye of a living subject having a lens capsule. The accommodative IOL  1000  is in the form of a lens bag  1010  with an effective focal power associated with geometry of the lens bag  1010  and a frame  1020  for engaging the lens beg  1010  with the lens capsule of the eye of the living subject. As shown in  FIGS. 10A  and  10 B, the lens bag  1010  has an anterior wall  1018   a  and a posterior wall  1018   b  defining a volume  1015  and an edge  1011 . The lens bag  1010  has a thickness  1040  defined therebetween a center of the anterior wall  1018   a  and a center of the posterior wall  1018   b.  Each of the anterior wall  1018   a  and the posterior wall  1018   b  has a variable curvature. The variable curvature of the anterior wall  1018   a  is substantially different from that of the posterior wall  1018   b.  The edge  1011  of the lens bag is substantially circular. The volume  1015  of the lens bag is filled with an optically transparent liquid such as a liquid gel. In operation, the geometry of the lens bag  1010  can be changed from one state to another state in response to a force applied to the lens bag  1010 . When the lens bag  1010  is in a condition-free state, as shown in  FIG. 10A , the curvature of the anterior wall  1018   a  is in its maximum value, and the lens bag  1010  has a maximum thickness, d 1 . Consequently, the lens bag  1010  in the condition-free state has the highest effective focal power. The frame  1020  includes a plurality of ridge bars  1025 . As shown in  FIG. 10C , the frame  1020  has 10 ridge bars and is formed with a structure that is symmetrical to a center of geometry of the lens bag  1010 . Other numbers of the ridge bars can also be used to practice the current invention. Each ridge bar  1025  has a first end  1024  and an opposite, second end  1026 . The first end  1024  of each ridge bar  1025  is attached to the edge  1011  of the lens bag at a predetermined position by an elbow  1017 . Each ridge bar  1025  is also coupled to the anterior wall  1018   a  of the lens bag by a string  1028  to connect the ridge bar at a point  1023  between the first end  1024  and the second end  1026  of the ridge bar  1025  to the anterior wall  1018   a  at a predetermined position  1019 . The accommodative IOL  1000  is implanted in an eye of a living subject by associating the plurality of ridge bars  1025  of the frame  1020  to the lens capsule of the eye of the living subject. When the ciliary muscle surrounding the lens capsule of the eye of the living subject contracts, the lens capsule will push the frame  1020  of the accommodative IOL  1000  inwardly to keep the lens bag  1010  of the accommodative IOL  1000  in a first state that is the condition-free state, as shown in  FIG. 10A . When the ciliary muscle surrounding the lens capsule of the eye of the living subject relaxes, the lens capsule will stretch the anterior wall  1018   a  of the lens bag  1010  of the accommodative IOL  1000  extending outwardly through the frame  1020  of the accommodative IOL  1000  to change the geometry of the lens bag  1010  from the first state in a second state, where the curvature of the anterior wall  1018   a  decreases, and the thickness  1040  of the lens bag  1010  decreases to d 2 , as shown in  FIG. 10B . Accordingly, the effective focal power of the lens bag  1010  in the second state and therefore the focal power of the accommodative IOL  1000  decreases.  
      Referring now to  FIG. 11 , an accommodative IOL  1100  for implantation in an eye of a living subject having a lens capsule  1190  is shown according to another embodiment of the present invention. As shown in  FIG. 11 , the accommodative IOL includes a silicone lens bag  1110  and an elastic wire frame  1120  that is adapted for engaging the silicone lens bag  1110  with the lens capsule. The silicone lens bag  1110  includes a circular edge portion  1111  having an inner diameter  1114  and an outer diameter  1116 . The elastic wire frame  1120  has a solid circle ring  1121  located inside the silicone lens bag  1110  at a position close to the inner diameter  1114  of the circular edge portion  1111 . The elastic wire frame  1120  also has two half-circle rings  1122  and two haptics  1124 . Each half-circle rings  1122  has a first end  1122   a  and a second end  1122   b,  respectively, and is embedded into a position between the inner diameter  1114  and the outer diameter  1116  of the edge portion  1111  with the first end  1122   a  welded to the solid circle ring  1121  at position  1121   a.  The two half-circle rings  1122  are configured in a nearly closed circle, as shown in  FIG. 11 . Each haptics has a first end  1124  and a second end  1124 , respectively. The second end  1122   b  of a half-circle ring  1122  is connected to the first end  1124   a  of a haptics  1124 . The haptics  1124  is adapted for contacting with and responding to the lens capsule  1190 . In operation, when the haptics  1124  are pushed inwardly, the half circle rings  1122  will be squeezed into a smaller diameter. The half circle rings  1122  are embedded into the edge portion  1111  of the silicone lens bag  1110  under this squeezed condition. After the pressure is released, the half circle rings  1122  will tend to expend into a bigger diameter, and force the silicone lens bag  1110  to be in a state having a lower focal power. After the accommodative IOL is implanted into the lens capsule of the eye of the living subject, the contraction of the lens capsule  1190 , caused by constriction of the ciliary muscle, will be able to squeeze the two half-circle rings  1122  into a smaller diameter according to the constriction force. The smaller diameter of the silicone lens has a higher focal power.  
      In another aspect, the present invention relates to a method of constructing an accommodative intraocular lens for implantation in an eye of a living subject having a lens capsule and a lens substance contained in the lens capsule. In one embodiment, the method includes the following steps: at first, a lens structure is formed to have a geometry and a focal power associated with the geometry. The lens geometry is changeable in response to a force applied to the lens structure. Second, a frame is formed. And then the frame is engaged with the lens structure and the lens capsule of the eye of the living subject such that contraction of the lens capsule pushes the lens structure contracting inwardly and relaxation of the lens capsule pulls the lens structure extending outwardly so as to change the lens geometry of the lens structure to adjust the focal power of the lens structure accordingly.  
      In operation, the lens structure can be fabricated as a convex lens bag. Material like PDMS can be used. The PDMS is preferably chosen because of its optical transparency, strength, and ability to be easily molded into various shapes and peeled from a surface. Referring to  FIG. 12 , in one embodiment, the convex lens bag can be constructed by a lens fabrication station  1250  having a micrometer adjustable stage  1240 , a convex lens mold  1255  and a concave lens mold  1265  complementarily placed below the convex lens mold  1255 , as shown in  FIG. 12A . To form a lens film  1209 , the PDMS and cure agent are poured onto a surface of the concave lens mold  1265  and, as the polymer cures, a constant pressure is applied by a convex lens mold  1255  that is controlled with a micrometer-adjustable stage  1240 . After peeling the PDMS lens film  1209  from the mold, biocompatibility is imparted to the surface of the lens film  1209  with a protein-resistant molecular film prepared from an oligo(ethylene glycol)-terminated alkyltrichlorosilane (HO(CH 2 CH 2 O) 3 SiCl 3 ) [23].  
      In one embodiment, a first and second PDMS lens films  1209  prepared in this manner are combined to form the lens bag. The zigzag elastic ring frame  1220  is squeezed into a smaller diameter, as shown in  FIG. 12B . Under this condition, the first PDMS lens film  1209  and the second PDMS lens film  1209  are glued in the edge portion  1211  to form a volume  1215  therebetween the first PDMS lens film  1209  and the second PDMS lens film  1209 , and embed the inner side of the ring frame in the equator of the silicone rubber bag. Silicone gel  1280  selected for its viscosity, optical clarity, and high refractive index then is injected into the lens bag.  
      Polypropylene, or polyamide or steel can be utilized as the elastic frame material. Medical grade epoxy can be used to glue the lenses to the elastic frame. Heat compressing can also be utilized to couple the lenses to the frame. Moreover, different or alternate frame configurations can be designed and utilized to couple the lenses to the frame.  
      Now referring to  FIGS. 13 , a device for simulating an accommodative effect of an IOL is shown. In one embodiment of the present invention, the device  1300  includes an iris diaphragm  1310  having a plurality of leaves  1315 . A diameter of the iris diaphragm  1310  is adjustable. The device  1300  further includes a holder  1340 . The holder  1340  is mounted on the iris diaphragm  1310  for holding the accommodative IOL  1350 . Moreover, the device  1300  includes a plurality of connectors  1320  that is adapted for engaging the plurality of leaves  1315  of the iris diaphragm  1310  with the accommodative IOL  1350  through the ciliary muscle  1355 . Additionally, the device  1300  includes a ring  1330  that is slipped on outside of the holder  1340  and mounted in the iris diaphragm  1310  for adjusting the diameter of the iris diaphragm  1310 . By adjusting the diameter of the iris diaphragm  1310 , the accommodative IOL  1350  expands or contracts through pulling or pushing the connector  1320 . Accordingly, the focal power of the accommodative IOL  1350  is changed. The device  1300  effectively simulates the movement of a ciliary muscle of the lens capsule.  
      The ring  1330  can be made of a metal or plastic. The holder  1340  can be made of a metal or plastic. The connector  1320  may includes at least one metal wire or tweezers  1320 , or like.  FIGS. 13A and 13B  show a device having tweezers connectors. Each tweezers  1320  has a base piece  1321  being welded to one of the plurality of leaves  1315  of the iris diaphragm  1310  and a top piece  1325  with a first end  1325   a  mounted on the base piece  1321  and an opposite second end  1325   b  having a plurality of teeth  1326  for engaging with the accommodative IOL. The tweezers  1320  also includes a knob  1327  on the top piece  1325  for adjusting the engagement of the plurality of teeth  1326  with the accommodative IOL.  
       FIG. 14  shows a device for simulating an accommodative effect of an intraocular lens according to another embodiment of the present invention. The device has a plurality of tweezers  1410  attached to the leaves of an adjustable iris diaphragm  1430 . A diameter of the iris diaphragm  1430  can be adjusted by an adjust member  1450 . In this embodiment shown in  FIG. 14A , eight tweezers are used. Other number of tweezers can also be used to practice the current invention. In vitro simulation of the accommodation function of an accommodative IOL was conducted by using a fresh animal cadaver eye. The fresh animal cadaver eye  1440  was dissected so as to obtain the lens with iris and ciliary muscle together. The ciliary muscle was clamped to the eight tweezers  1450  symmetrically, as shown in  FIGS. 14B and 14C . Adjusting the diameter of the iris diaphragm  1430  causes the diameter change of the ciliary muscle and the diameter change of the lens capsule as well. This would simulate the in vivo accommodative function of the eye in an ex vivo model.  
      When the diameter of the adjustable diaphragm increased, it would pull the ciliary muscle outwardly. The diameter of the animal lens would be increased. In the example shown in  FIG. 15 , the diameter of the lens  1540  was increased from 11 mm, as shown in  FIG. 15A , to 12 mm, as shown in  FIG. 15B , when the diameter of the circle of tweezers changed from 17 mm to 20 mm. At the same time, the curvature of the lens anterior and posterior portions of the animal lens  1540  changed, and the animal lens  1540  was pulled to move backwards axially.  
      In order to measure diopter changes of the animal lens, an artificial ocular structure was assembled (not shown here). A plastic Plano-convex lens was used as cornea surface. A 3 mm diameter hole was used as pupil. The animal lens held by the adjustable device shown in  FIG. 14A  was set at a predetermined position beneath the cornea. A flat white surface with certain blood vessel drawing served as retina and was set at a certain distance beneath the device. Everything was screwed together so that the distance between the cornea and the retina would not change. BSS solution was filled in the artificial ocular structure. The diopter change caused by the animal lens was measured by a vertically setup autorefractor (model MRK-2000, Huvitz Co. Ltd., Gyeonggido, Korea). This artificial ocular structure was not according to human or any animal eye. It was only to set up an ocular structure, so that the refraction change can be measured by the autorefractor. Table 2 shows the diopter changes of a pig eye lens versus the diameter of the adjustable diaphragm. The diopter reading first became smaller, indicating that the focal power of the lens increased, and then became higher, indicating that the focal power of the lens decreased.  
               TABLE 2                          Measurement of the diopter change of a pig eye lens versus the       diameter of the adjustable diaphragm.                         Diameter of the Circle of           the Tweezers (mm)                                     14   15   16   17                                                     Diopter Reading   +2.25   +1.50   +1.25   +3.75                      
 
      Capsulorrhexis was performed on the anterior surface of the clamped pig eye lenses. Lens content was removed. Accommodative IOLs with different ring frames were implanted into the lens capsule. The movement of the accommodative IOL responsive to diameter changes of the ciliary muscle was studied.  
      The different accommodative IOLs according to embodiments of the present invention are shown in  FIGS. 16A-16C . Gaussian lenses  1610 ,  1620  and  1630  were made by an injection mold method from Polymer Optics, LLC, Santa Rosa, Calif. The material formed these accommodative IOLs was cyclic-olefin copolymer (COC). Other material can also be used to practice the present invention. The diameter of the single Gaussian lens  1610  was 5.5 mm, as shown in  FIG. 16A . The thinnest thickness of the lens that the company could produce is 160 μm to 170 μm, versus a designed thickness of 100 μm. The accommodative IOL of 8 Gaussian lenses had a thickness of 1.6 mm, as shown in  FIG. 16B , and the accommodative IOL of 6 Gaussian lenses had a thickness of 1.2 mm, as shown in  FIG. 16C . Different materials with different thicknesses were used to make the zigzag frame, which included: transparency film of 100 μm thickness, PMMA film of 50 μm thickness, COC film of 60 μm and 100 μm, plastic film of 40 μm thickness, plastic film of 20 μn thickness.  
      Measurement of the diopter changes of the accommodative IOL by using artificial ocular setting and the autorefractor was showed in Table 3. The accommodative IOL used to perform the capsulorrhexis was formed with 6 Gaussian lenses and a frame of 20 μm thickness. As shown in  FIG. 16E , when the diaphragm was adjusted to a smaller diameter, the diameter of the accommodative IOL  1660  was squeezed into a smaller diameter. Accordingly, the diopter of the accommodative IOL  1660  decreased and the diopter reading was in small values, as indicated by the second column of Table 3. In this situation, the accommodative IOL  1660  had a higher focal power. When the diaphragm was adjusted to a bigger diameter, the diameter of the accommodative IOL  1660  is extended. Consequently, the diopter of the accommodative IOL  1660  increased and the diopter reading was in large values.  
      The focal power of the accommodative IOL  1660  decreased. As shown in  FIG. 16F , the diameter of the accommodative IOL  1660  was 0.5 mm larger than that of  FIG. 16E . The diopter for the large diameter accommodative IOL  1660  increased, and the corresponding diopter reading was listed in the third column of Table 3. The diopter changes for the accommodative IOL  1660  in the above two different diameters were presented in the fourth column of Table 3.  
               TABLE 3                          Measurement of diopter changes of an accommodative IOL by using an       artificial ocular and an autorefractor.                                 Diopter Reading for   Diopter Reading for           Number of   Small Diameter of the   Bigger Diameter of the   Diopter       Test   Diaphragm   Diaphragm   Changes                                     1   +9.00   +14.75   +5.75       2   +9.75   +10.00   +0.25       3   +10.25   +11.25   +1.00                  
 
      For implantation of the accommodative IOL into the cadaver animal eye in a surgical mode, cadaver sheep eye was used. An opening of 7 mm was made at the limbus. Healon was used to extend the anterior chamber. Capsulorrhexis of about 6 to 6.5 mm was made. Because the zigzag ring frame was very soft, the accommodative IOL was slide easily through the opening and implant into the capsule.  
      In the present invention, among other things, an accommodative IOL for implantation in an eye of a living subject is disclosed, which includes a lens structure having a geometry and a focal power associated with the geometry and a frame for engaging the lens structure with the lens capsule of the eye of the living subject such that contraction of the lens capsule pushes the lens structure contracting inwardly and relaxation of the lens capsule pulls the lens structure extending outwardly so as to change the geometry of the lens structure to adjust the focal power of the lens structure accordingly.  
      The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.  
      The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.  
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