Patent Publication Number: US-2013231741-A1

Title: Use of accommodating intraocular lens

Description:
BACKGROUND 
     This invention relates generally to manufactured intraocular lenses and more particularly to novel accommodating intraocular lenses for implantation in the eye specifically within the capsular bag, or in the ciliary sulcus, of the eye from which the natural lens matrix has been removed. The invention also relates to a novel method of utilizing the intraocular lenses in the eye to provide the patient with lens accommodation capability, responsive to normal accommodative ciliary muscle action. 
     The human eye has an anterior chamber between the cornea and the iris, and a posterior chamber behind the iris, which contains a natural crystalline lens. A vitreous chamber behind the lens contains vitreous humor. A retina is located to the rear of the vitreous chamber. The crystalline lens of a normal human eye is defined by a crystalline lens matrix, which is enclosed in a lens capsule. The lens capsule is attached about its periphery to the ciliary muscle of the eye by zonules. The lens capsule has elastic, optically clear, anterior and posterior membrane-like walls commonly referred by ophthalmologists as anterior and posterior capsules, respectively. Between the iris and ciliary muscle is an annular crevice-like space called the ciliary sulcus. 
     The human eye possesses natural accommodation capability. Accommodation refers to an optical function in which the lens can focus naturally, from a far distance, to a relatively near distance e.g. within a few centimeters of the eye. Natural accommodation involves relaxation and constriction of the ciliary muscle, as instructed by the brain, to provide the eye with near and distant vision. This ciliary muscle action is automatic, as instructed by the brain, and shapes the natural crystalline lens to the appropriate optical configuration for focusing, on the retina, the light rays entering the eye from the scene being viewed. It is well known that there is a relentless loss of this near focusing ability in middle age. Such condition can be treated with bi-focal or tri-focal glasses or contact lenses. 
     The human eye is also subject to a variety of other physiological disorders, which can degrade, or totally destroy, the ability of the eye to function properly. One of the more common of these disorders involves progressive clouding of the natural crystalline lens matrix resulting in the formation of what is commonly referred to as a cataract. It is now common practice to treat a cataract by surgically removing the cataractous human crystalline lens and, in a second step of the same surgical procedure, implanting an artificial intraocular lens in the eye to replace the natural lens. 
     Thus, if the natural lens becomes cloudy, as with a cataract condition, the natural lens is removed by an extraction procedure which leaves intact, within the eye, the posterior portion of the natural lens capsule, and at least a remnant of the anterior portion of the natural lens capsule. The removed natural lens is replaced with a manufactured intraocular lens. If the replacement lens is a mono-focal lens, the cloudiness may have been effectively treated, but the inability to adjust focal length will not have been treated, whereby glasses or contact lenses are still required for proper vision. 
     Monofocal lenses focus at one set focal length in front of the eye, for example either at far distance such as greater than 6 meters, or at a lesser distance nearer the eye. The human eye with its own natural lens can change shape, thereby to focus naturally at all such distances, but gradually loses this ability, to change shape, as the natural lens hardens with age. The ability of the natural lens, to change shape as so urged by the contraction of the ciliary muscle, thus to change focal length of the eye, whereby the eye can focus at any of a range of distances, is completely lost after cataract surgery when the manufactured replacement lens is a monofocal lens. 
     Newer designs of conventional manufactured intraocular lenses offer differing solutions to this problem of loss of accommodation. One such design is a lens which has a single posteriorly placed optic and hinged haptics, which enables the lens to translate forward with the pressure rise in the vitreous chamber, which pressure rise accompanies accommodation as signaled from the brain. The limitation of this design is that the maximum accommodation enabled by lens translation is typically only about 1.5 diopters for a 1 mm anterior translation of the lens. While a 1 mm translation is typical, modest differences in translation capability attend respective different eyes. Thus, actual diopter achievements depend both on the power of the intraocular lens, and the axial length of the eye. 
     Another relatively newer conventional manufactured intraocular lens design uses two lenses, which are hinged, or otherwise connected, together and implanted inside the natural lens capsular bag. The anterior manufactured lens has e.g. high plus power, while the posterior manufactured lens has a negative power. When the two lenses separate under accommodative tension, the anterior lens moves forward and the posterior lens moves backward, achieving a relatively higher calculated accommodation, which is less dependent on intraocular lens powers and/or axial lengths of the eye. 
     Yet another conventional intraocular lens design provides multiple lens elements or components in side-by-side relationship, in a single lens body, the respective side-by-side lens elements having different, but fixed, refractive powers. 
     Still another conventional intraocular lens design provides an intraocular lens which consists of a flexible transparent lens envelope filled with a transparent fluid. The envelope is attached to the ciliary muscle by means of a fastening fringe, which is in turn anchored to the lens envelope. The ciliary muscle acts as it does on the natural lens. Thus, when the ciliary muscle contracts, the lens becomes more spherical, and thus achieves a greater refractory power. When the ciliary muscle elongates, tension is exerted on the envelope, and flattens the envelope, reducing refracting power, which accommodates far vision. 
     SUMMARY 
     The current invention comprehends an accommodating intraocular lens made from flexible, optionally elastic, bio-compatible lens body material surrounding a closed and sealed lens cavity which is filled with bio-compatible optical liquid, such as a gel, or an oil-based optical composition, which has a refractive index sufficiently greater than the refractive index of the vitreous humor in the eye, that changes in shape of the optical liquid satisfy the optical requirements for achieving accurate and accommodative focus on the retina, while being sufficiently deformable to change the curvature of the anterior and/or the posterior intraocular lens surfaces to allow accommodation—near focus—to occur as in the natural state for the youthful eye, by operation of the optical liquid in the cavity in accord with the change in curvature of the anterior and/or posterior surfaces of the optical liquid. 
     Namely, change in radius of curvature in the lens body automatically changes the corresponding radius of curvature of the effective surface of the contained optical liquid which is at the respective location adjacent the lens body in the lens cavity. The refractive index of the optical liquid in the lens cavity is greater than the refractive index of the vitreous humor, which is approximately equal to the refractive index of water, which is namely about 1.33. A suitable refractive index for the optical liquid in the cavity is about 1.40. An exemplary suitable composition for the optical composition, having such suitable refractive index, is optical grade silicone oil, alternatively hyaluronic acid, or its ester, with suitable additives for providing the desired physical properties such as viscosity. 
     A first family of embodiments of lenses of the invention comprehends an accommodating intraocular lens, comprising a bio-compatible optical lens body having an anterior body member and a posterior body member, joined to each other. The optical lens body defines a vision axis, and an optical lens body outer perimeter which extends about the vision axis. At least one of the anterior body member and the posterior body member has a convex radius of curvature, which has an origin on the vision axis. The lens further comprises a closed and sealed cavity in the lens body, extending generally outwardly away from the vision axis. The lens still further comprises a bio-compatible liquid filling the cavity, the liquid having a refractive index greater than the refractive index of water, and connecting structure attached to the optical lens body at or adjacent the outer perimeter of the optical lens body. The connecting structure is effective to interface with a ciliary muscle, and to transmit forces, exerted by the ciliary muscle, related to contraction or relaxation of the ciliary muscle, on the connecting structure, to the optical lens body at or adjacent the outer perimeter of the lens body, thereby to cause the force so received by the lens body to effect change in radius of curvature of at least one of the anterior body member and the posterior body member. 
     In some embodiments, the connecting structure comprises a flange which extends outwardly from the outer perimeter of the lens body, away from the vision axis, the flange having sufficient rigidity to transmit forces, exerted by the ciliary muscle, which urge reduction in length of the outer perimeter of the optical lens body, to the outer perimeter of the optical lens body. 
     In some embodiments, the anterior body member has convex outer and inner surfaces, and the posterior body member has a planar or concave or otherwise recessed inner surface. 
     In some embodiments, the posterior body member is more rigid than the anterior body member, whereby imposition of an inwardly-directed force against an outer edge of the flange results in deflection of the anterior body member in preference to deflection of the posterior body member. 
     In some embodiments, the anterior body member has inner and outer surfaces, the outer surface defines a convex configuration, the inner surface has a corresponding convex configuration which follows the configuration of the outer surface, and the inner and outer surfaces optionally are defined by compound radii of curvature when tracked through the vision axis. 
     In some embodiments, each of the inner and outer surfaces is defined by a single center of rotation located on the vision axis. 
     In some embodiments, at least one of the inner and outer surfaces is defined by multiple centers of rotation. 
     In some embodiments both the anterior body member and the posterior body member have convex inner surfaces. 
     In some embodiments, the compositions of the anterior body member and the posterior body member are selected from the group consisting of optical grade silicone, polymerized collagen, optical elastic acrylic polymer, collamer, and combinations of collamer and hydroxyethyl methacrylate. 
     In some embodiments, the composition of the bio-compatible filling liquid is selected from the group consisting of silicone oil, hyaluronic acid, and salts of hyaluronic acid. 
     In some embodiments, the filing liquid has a refractive index of at least 1.35, and is optionally birefringent. 
     In some embodiments, the filing liquid has a refractive index of at least 1.40. 
     In a second family of embodiments, the invention comprehends a method of providing focal length adjustment in an eye of a patient in need of a replacement intraocular lens. The method comprises installing in the eye an accommodating intraocular lens, which comprises a bio-compatible optical lens body having an anterior body member and a posterior body member, joined to each other, the optical lens body defining a vision axis, and an optical lens body outer perimeter which extends about the vision axis, at least one of the anterior body member and the posterior body member having a radius of curvature having an origin on the vision axis, a closed and sealed cavity in the lens body, extending generally outwardly away from the vision axis, and a bio-compatible liquid, filling the cavity, the liquid having a refractive index greater than the refractive index of water. The method further comprises interfacing connecting structure of the intraocular lens, such as a flange, to a ciliary muscle of the patient such that the connecting structure is effective to receive change in forces accompanying change in muscle contraction or relaxation, and to transmit such change in forces to the optical lens body at or adjacent the outer perimeter of the optical lens body, thereby to cause the force changes so received by the lens body to effect change in radius of curvature of at least one of the anterior body member and the posterior body member. 
     In some embodiments, the eye of the patient has a natural lens capsule, having a circumferential outer edge, the connecting structure of the lens comprises a flange extending from the outer perimeter of the lens body, the flange has sufficient rigidity to transmit, to the lens body, forces exerted by the ciliary muscle, on the natural lens capsule, which urge reduction in length of the outer perimeter of the optical lens body. The corresponding method comprises installing the intraocular lens such that the outer edge of the flange is inside the lens capsule, and adjacent the outer edge of the lens capsule, such that the flange is sensitive to activity of the ciliary muscle, and transmits the change forces to the optical lens body, thereby to provide focal length accommodation. 
     In some embodiments, the posterior body member is rigid relative to the anterior body member, such that changes in the radius of curvature of the anterior body member, by flexure of the anterior body member, causes changes, in focal length of the liquid filling, which are substantially greater than any changes in focal length caused by flexure of the posterior body member. 
     In some embodiments, the eye of the patient comprises a sulcus, and the method further comprises positioning the outer edge of the flange in the sulcus. 
     In some embodiments, both the anterior lens body and the posterior lens body define convex inner and outer surfaces, and respond to flexure of the ciliary muscle with similar changes in radius of curvature. 
     In some embodiments, inner and outer surfaces of the at least one convex body member having substantially the same radii of curvature. 
     In a third family of embodiments, the invention comprehends an accommodating intraocular lens, comprising a bio-compatible optical lens body having an anterior body member and a posterior body member, joined to each other, the optical lens body defining a vision axis, and an optical lens body outer perimeter which extends about the vision axis, at least one of the anterior body member and the posterior body member having a radius of curvature having an origin on the vision axis; the joinder of the anterior lens body member and the posterior lens body member defining a cavity therebetween, in the lens body, the cavity extending generally outwardly away from the vision axis; one or more compressible struts in the cavity, extending between the anterior lens body member and the posterior lens body member, the one or more struts being displaced from the vision axis, and being configured to flex away from the vision axis when compressed; and a bio-compatible liquid filling in the cavity, the liquid having a refractive index greater than the refractive index of water. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a generally front pictorial view of a first embodiment of a lens of the invention. 
         FIG. 2  shows a front view of the lens of  FIG. 1 . 
         FIG. 3  shows a side cross-section view of the lens of  FIGS. 1 and 2 , taken at  3 - 3  of  FIG. 2 . 
         FIG. 4  shows a rear pictorial view of the lens of  FIGS. 1-3 . 
         FIG. 5  is a cross-section view illustrating the lens of  FIGS. 1-4  implanted in an eye. 
         FIG. 6  shows a cross-section view of a second embodiment of lenses of the invention. 
         FIG. 7  shows a cross-section view of a third embodiment of lenses of the invention. 
         FIG. 8  is a cross-section view illustrating the embodiment of  FIG. 7 , implanted in an eye. 
         FIG. 9  shows a cross-section view of a fourth embodiment of lenses of the invention. 
         FIGS. 10-11  show expanded representations of the mathematical matrices discussed in Langenbucher. 
     
    
    
     The invention is not limited in its application to the details of construction or the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in other various ways. Also, it is to be understood that the terminology and phraseology employed herein is for purpose of description and illustration and should not be regarded as limiting. Like reference numerals are used to indicate like components. 
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     A first family of embodiments of accommodating intraocular lenses  10  of the invention is illustrated in  FIGS. 1-4 .  FIG. 5  shows an exemplary such lens implanted in an eye. 
     Lens  10  includes a lens body  12 , and first and second flanges  14 . Lens body  12  includes a convex anterior body member  16  and a generally planar posterior body member  18 . Anterior body member  16  has an inner surface  20  and an outer surface  22 . Posterior body member  18  has an inner surface  24  and an outer surface  26 . Anterior body member  16  and posterior body member  18  are joined to each other at an outer perimeter  27  of the lens body. 
     A vision axis  28  extends through the lens body, generally centered with respect to outer perimeter  27  of the lens body. Vision axis  28  generally passes through the apex of the convex arc which is defined by anterior body member  16 , and also passes through the center of the posterior body member. Thus vision axis  28  is generally centered on the lens body, and passes front-to-rear through the lens body, as through the center of the anterior body member and the center of the posterior body member. 
     As illustrated in  FIGS. 1 ,  2 , and  4 , flanges  14  are connected to the lens body at outer perimeter  27 , at opposing sides of the lens body, and extend from the lens body in opposing directions which are generally perpendicular to the direction of extension of the vision axis or at a small angle to such perpendicular, e.g. no more than 10 degrees. 
     Between the anterior body member and the posterior body member is a closed and sealed cavity  30  which is generally defined by the inner surfaces  20 ,  24  of the anterior body member and the posterior body member. In the illustrated embodiment, cavity  30  has a cross-section which is generally constant, or nearly constant, when turned about the vision axis. Given the shapes of the inner surfaces of the anterior and posterior body members, cavity  30  has a cross-section which generally resembles a hemisphere. 
     As illustrated in  FIG. 3 , a cross-section of the arcuate inner surface of anterior body member  16  generally resembles a circular configuration. However, as is well illustrated in  FIGS. 6 and 7 , an arcuate inner surface of either or both of anterior body member  16  or posterior body member  18  can deviate substantially from a true circular, e.g. hemispherical path. Both  FIGS. 6 and 7  illustrate compound arcuate paths where the radii of curvature change along the progression of the arcuate path of the respective inner surface  20  or  24 . However, in typical embodiments, a cross-section of the lens body reveals symmetry of the arcuate inner surface with respect to the vision axis. 
     Referring to  FIG. 3 , the configuration of the arcuate path of inner surface  20  is the same as the configuration of the arcuate path of outer surface  22 , off-set in that the origins of the arc segments in inner surface  20  are displaced along vision axis  28  from the origins of the arc segments in outer surface  22 . Accordingly, and as illustrated in  FIG. 3 , the thickness of the anterior body member is represented by relatively greater dimensions at locations proximate the vision axis and is represented by relatively lesser dimensions at portions  37  of the anterior body member which are remote from the vision axis. 
     The thickness of the posterior body member is generally constant, and is generally greater than the thickness of the anterior body member, about the majority of the projected area of the posterior body member, namely all of the posterior body member except that portion  36  of the posterior body member which is remote from the vision axis. 
     The lens body can be made from material which comprises, for example and without limitation, a silicone composition such as is known for use in intraocular lenses. Such silicone composition is resiliently elastic and compressible, but retains good restorative dimensional memory. Other shell membrane materials can be used such as, for example and without limitation, polymerized collagen (Collamer, manufactured by Staar Surgical, Inc.), Monrovia, Calif., elastic acrylic polymers, combinations of collamer and hydroxyethyl methacrylate, and other clear, e.g. transparent, flexible bio-compatible materials well known in the art as being suitable for use in optical applications. 
     Cavity  30  is filled with optical liquid  38 . Liquid  38  is a viscous liquid which, in one embodiment of the invention can be silicone oil which has a refractive index of 1.4034, e.g. about 1.40, which material is known for use to fill the vitreous cavity in certain cases of retinal detachment and so is known to be bio-compatible. Optical liquid  38  does not contact the natural bio-intraocular structures of the eye, as the oil is enclosed entirely within the closed and sealed cavity  30  of the flexible lens body. 
     Other bio-compatible viscous materials, which can be used as the optical liquid, include chondroitin sulfate, hyaluronic acid and its hyaluronate salts, optionally mixed with e.g. saline solution, to obtain fairly precise desired refractive indices such as at or above 1.4. A variety of other viscous gels having suitable refractive index, can be used. Any such gel must be visually transparent, must have a refractive index greater than the refractive index of is water, e.g. above about 1.33, and must be bio-compatible with respect to the use environment. Given these rather broad parameters, a substantial range of material compositions are acceptable as the contained interior substance. 
     The viscosity of optical liquid  38  is substantially greater than the viscosity of water, but liquid  38  must be sufficiently pliable to easily conform to any changes in curvature of the adjacent body member which may be urged on the lens body. In general, optical liquid  38  reflects the character of a gel, while being readily deformable when so urged by the anterior body member and/or the posterior body member. Accordingly, liquid  38  typically has a viscosity of about 4000 millipoise to about 7,000,000 millipoise, optionally about 30,000 to about 3,000,000 millipoise. One known acceptable gel has a stated viscosity of 30,000 to 50,000 centistokes (cSt). The viscosity can, of course, be adjusted by incorporation, in the optical liquid, of viscosity change agents known to those skilled in the gel arts. 
     Optical liquid  38  can also have the quality of circular or orthogonal birefringence. Birefringence is the quality of materials wherein light of certain polarities, either orthogonal as in traditional polarizing lenses, or circular polarity, has two refractive indices. Such birefringence can be obtained by mixing two materials having the different, e.g. refringent indices. Example of such mixture is a mixture of dextro-rotary and levo-rotary biologic sugars and/or amino acids. So long as the two refractive indices differ by a significant amount, the lens is birefringent, and thus bifocal. Such lens focuses light of one polarity at a relatively greater distance, and light of a different polarity at lesser distances. Such birefringence increases the bifocal effect of the lens, but is not essential for lens function in this invention. 
     Lens body  12  can be fabricated with cavity  30  being empty. A sealable valve is assembled to the lens body, out of the line of sight of the eye, thus away from vision axis  28 . The gel is filled into cavity  30  through the resealable valve. 
     The function of the lens, as an accommodating lens in this invention, depends primarily on the change in the arcuate shape of the lens body, which change occurs as an act of accommodation. The change in shape is provided by the combination of flexing of the shell material e.g. anterior body member  16 , and fluidity of optical liquid  38  in response to an action of the ciliary muscle. 
       FIG. 5  illustrates the lens of  FIGS. 1-4  installed in a human eye  40 , it being understood that lenses of the invention can also be installed in the eyes of various animal species. As illustrated in  FIG. 5 , the natural lens has been removed, such as in a cataract surgery. 
     The natural capsular bag  42 , which previously enclosed the natural lens is largely in place, though part of the anterior portion of the natural bag has been removed in the embodiment illustrated in  FIG. 5 . 
     Lens  10  is positioned such that distal edges  44  of flanges  14  are disposed against the inner surface  46  of the outer perimeter  48  of the capsule bag. The capsule bag remains attached to the ciliary muscle  50  through zonules  52 . However, flanges  14 , in the embodiment illustrated, are of sufficient length that the flanges expand the outer perimeter of the capsule bag such that the outer perimeter of the bag is proximate the ciliary muscle. Accordingly, even modest contraction of the ciliary muscle is effective to push against the distal edges of flanges  14 . 
     Lens  10  generally works as follows. When the eye tries to focus on a near object, the ciliary muscle  50 , illustrated in  FIGS. 5 and 8 , contracts inward, pushing inward on the lens zonules, and on the outer perimeter  48  of the capsule bag, while also raising pressure in the vitreous gel behind the lens. The centripetal force of the contracting ciliary muscle is transmitted inwardly, through the capsule bag to the distal edges of flanges  14 , and through flanges  14  toward the vision axis, thus to reduce the e.g. diameter of outer perimeter  27  of the lens body. As the size of the outer perimeter of the lens body decreases, the maximum diameter of the anterior body member correspondingly decreases. The anterior body member is fabricated, in the embodiment illustrated in  FIGS. 1-5 , to be more readily flexed than the posterior body member. Accordingly, a disproportionate share of the flexing, which is imposed by the ciliary muscle on flanges  14 , is absorbed by the anterior body member. The physical response of the anterior body member is expressed as an inward flexing of the remote portions  37  of the anterior body member, e.g. adjacent the outer perimeter of the lens body. 
     The inward flexing of the anterior body member at the outer perimeter is accompanied by generally reduced radius of curvature of anterior body member  16  as the anterior body member flexes to accommodate the reduction in diameter of the lens body at outer perimeter  27 . Such reduction in radius of curvature of the anterior body member urges a corresponding change in the curvature of the surface of optical liquid  38  which is disposed at the inner surface of the anterior body member. Such resulting change in the configuration of optical liquid  38  generates a change in the focal length of the lens. Such change in optical radius of curvature of the working optics, in this case optical liquid  38 , changes the focal point of the lens in a multiplicative fashion, via Snell&#39;s law, wherein 
       Power=(Difference in Indices)/(Radius of Curvature). 
     Lens assemblies which rely on linear e.g. translational, movement of a first lens body with respect to a second lens body, or simply movement of a lens body along the vision axis, to provide for change in focal length, rely on a linear relationship between the distance of movement of the lens body and the change in focal length. 
     By contrast, substantially greater multiplicative changes in focal length can be achieved by using the ciliary muscle to change primarily curvature of the lens rather than to cause primarily translation movement of the lens surfaces as in the conventional art. Thus, where change in focal length according to translational movement of the lens surfaces by action of the ciliary muscle is limited to about 1.5 diopters for a 1 mm translation of a lens, change in curvature of lenses of the invention, responsive to the same action of the ciliary muscle, can provide up to about 3.5 diopters change, optionally up to about 3 diopters change, further optionally up to about 2.5 diopters change, depending on the starting arcuate profile of the lens. The lens can, of course, be designed to deliver lesser degrees of change, such as up to about 2.0 diopters, or less, as desired. 
       FIG. 6  illustrates a second embodiment of accommodating intraocular lenses of the invention. In the lens of  FIG. 6 , anterior body member  16  is convex as in the embodiment of  FIGS. 1-5 , thus to provide basis for efficient change in focal length with change in activity of the ciliary muscle. Posterior body member  18  is, contrary to the embodiment of  FIGS. 1-5 , mildly concave, or recessed planar as shown, so as to accommodate e.g. a bulging profile on the vitreous humor, or where the depth of the lens cavity, between the vitreous cavity and the natural iris  54  is insufficient to properly receive a lens which is configured as in  FIGS. 1-5  where the posterior body member is planar, and not recessed. As in the embodiments of  FIGS. 1-5 , both anterior body member  16  and posterior body member  18  are shown to be symmetrical with respect to the vision axis. 
       FIGS. 7 and 8  show another modified version of the lenses of  FIGS. 1-6 . The lens of  FIGS. 7 and 8  have flanges  14  which are designed to fit directly into the ciliary sulcus  54 , e.g. directly against the ciliary muscle. In the assembly shown in  FIG. 8 , flanges  14  are outside, e.g. in front of, the capsular bag, and in direct contact with the contracting ciliary muscle  50 . Contraction of muscle  50  applies force directly onto flanges  14 . Flanges  14  transmit the forces to lens body  12 , thus directly compressing the lens body at outer perimeter  27  of the lens body. 
     Such compressing of the lens body at outer perimeter  27  shortens the radii of curvature of both the anterior body member and the posterior body member, and achieves a high degree of accommodation, potentially higher than any accommodation which would accompany a corresponding muscle contraction in connection with a lens of  FIGS. 1-5 , or  FIG. 6 . 
     Such increase in degree of accommodation results from the fact that both of body members  16  and  18  are convex. Namely, the convex nature of liquid  38  is established at the inner surface of the anterior body member as well as at the inner surface of the posterior body member. With convex curvature at both the anterior surface of liquid  38  and at the posterior surface of liquid  38 , light rays incident on the lens are treated to both a first anterior focal length adjustment, and to a second posterior focal length adjustment. 
     In general, placing flanges  14  in the sulcus is less preferred than placing the flanges in the capsule bag. However, in some instances, the lenses of  FIGS. 1-6 , wherein only the anterior body member is convex, are deficient in terms of the diopter adjustment which can be achieved. 
     Where greater diopter power is required, the double-convex lens of  FIG. 7  is available to provide such optical power. However, where the double-convex lens of  FIG. 7  is selected, it is quite possible that the front-to-back distance, between the vitreous chamber and generally up to the iris of the eye, may be too small to receive the front-to-back dimension of the lens of  FIG. 7 . In such instance, flanges  14  are positioned relatively frontwardly in the lens cavity, and are positioned in the sulcus, in order that the back of the lens body be in front of, e.g. displaced from, the vitreous chamber, as illustrated in  FIG. 8 . As illustrated in  FIG. 8 , in such instance, the front of the lens may extend frontwardly of the natural iris  56 . 
     Still referring to the embodiments of  FIGS. 7 and 8 , compressing one or both of the body members  16 ,  18 , at outer perimeter  27 , shortens the radius of curvature of the anterior body member and the posterior body member, both generally about vision axis  28 , whereby the shape of the lens is reconfigured more toward a spherical shape. 
     The forces of ciliary contraction during accommodation may not transmit directly through zonules  52  to the capsular bag. The zonules are a loose network of fibers, and so the zonules might slacken when the ciliary body contracts. The exact mechanism of operation of zonules is still not fully settled among ophthalmologists and physiologists. 
       FIG. 9  shows, as a further embodiment, a relatively larger lens, which fits snugly within the capsular bag. This lens has anterior  16  and posterior  18  body members enclosing viscous optical liquid  38 , but is devoid of flanges  14 . Inside the lens body are first and second struts  58 . Struts  58  can optionally extend 360 degrees around vision axis  28 , either intermittently, or as a single continuous strut body, on the interior of the shell. Struts  58  are resiliently compressed front-to-rear when the ciliary muscle is relaxed, and in the non-accommodating state. As the ciliary muscle contracts, the restorative forces in struts  58  push the anterior and posterior body members away from each other, front-to-rear, thus to accommodate near vision. The design of the strut allows the strut to bend only outward, away from vision axis  28 . This action, of pushing the anterior and posterior body members away from each other, shortens the radius of curvature of e.g. the anterior body member in a fashion similar to natural shortening of the radius of curvature, accommodation, in a natural lens. 
     Calculations of the needed curvatures of the anterior and posterior optical surfaces of the anterior  16  and posterior  18  body members, to enable focusing of light at distance when the eye is in a relaxed state can be realized using the matrix system of optical calculations which are described, for example, by Langenbucher et al in Ophthal. Phyisol. Opt. 2004 24:450-457, herein incorporated by reference in its entirety. 
     In all of the lens embodiments of  FIGS. 1-9 , the outer body members  16  and  18  are thinnest at or adjacent outer perimeter  27  of lens body  12 , optionally proximate flange  14  in the embodiments of  FIGS. 1-8 . Forces from the ciliary muscle are transferred through flanges  14  to body members  16 ,  18 . Given the relatively thinner portions of the body members proximate flanges  14 , the body members flex to a greater extent proximate flanges  14  than farther away from the flanges, and thereby shorten the radius of curvature of the optical surfaces of body members  16 ,  18 , thereby to effect diopter change in the lens body primarily through corresponding curvature changes in the contained optical liquid  38 . 
     In the embodiments of  FIGS. 1-5 , posterior body member  18  is substantially flat, planar, and thus lacks any optical power. The posterior body member is also thicker than the anterior body member in such embodiments, whereby the degree of change in curvature of the anterior body member, expressed as distance of translation of the anterior body member perpendicular to the profile of the anterior body member, is substantially greater than the degree of change, if any, in the curvature in the posterior body member. The embodiments of  FIGS. 3 and 6  may enable transmission of the pressure rise in the posterior vitreous chamber to assist in changing the anterior radius of curvature, thereby increasing near focusing, namely accommodating, power. 
     The function of lens  10  as an accommodating lens depends primarily on the change in shape of the lens as the act of accommodation. When the e.g. human eye tries to focus on a near object, the ciliary muscle contracts inward, pushing inward on the lens zonules, and also raising pressure in the vitreous chamber which is behind the lens. The centripetal force of the contracting ciliary muscle is transmitted through the lens flange  14 , compressing the lens body at outer perimeter  27 . Compressing the lens body at outer perimeter  27  shortens the radius of curvature of the anterior body member in the embodiments of  FIGS. 1-6 , and shortens the radius of curvature of both the anterior and posterior body members in the embodiment of  FIGS. 7 and 8 . In all of the lens embodiments of  FIGS. 1 through 8 , the lens body is relatively thinner at the juncture of the anterior and posterior shells with flange  14 , e.g. at outer perimeter  27 . In this scenario, the forces received from flanges  14  are absorbed largely in shortening the radius of curvature of the optical surfaces, rather than largely being absorbed in translation of the anterior body member further away from the posterior body member. 
     This is in contrast to translation of the body members where the power changes depend on position in the eye and axial length of the eye. For this reason, the lenses of the invention offer greater diopter ranges than lenses which operate according to translation of one or more of the lens elements. 
     As indicated above, with the exception of the embodiments of  FIG. 9 , the force of the ciliary muscle is received at distal edges  44  of flanges  14 . The muscle force is transmitted through flanges  14  toward lens body  12 , and is received at lens body  12  at or adjacent outer perimeter  27 . Such force acts, through outer perimeter  27 , on the lens body to re-shape the curvature of the anterior and/or posterior body members, thus to effect change in focal length of the lens body. 
     Thus it is critical that the flanges, where used, have sufficient rigidity that the contraction forces of the ciliary muscle are transmitted to the lens body in sufficient intensity to effect accommodation of the lens body in accord with the accommodative vision needs being expressed by the ciliary muscle. 
     To that end, flanges  14  can be specified in terms of thickness “T” sufficient to provide the required level of rigidity which is effective to transmit the ciliary muscle forces. The particular dimension of thickness “T” depends on the rigidity of the material composition selected for flange  14 , and can be well selected by those skilled in the art. 
     In the alternative, the composition of the material used to make flanges  14  can be different from the material used to make lens body  12 . Thus, the material used to make flanges  14  can be more rigid than the material used in making body members  16 ,  18 , thus to achieve rigidity by material selection. 
     As used herein “optical liquid ” includes gels, which might not otherwise be considered liquids, to the extent the shape of the gel mass can be readily changed by action of the ciliary muscle. Thus, “optical liquid” does include gel compositions which have viscosity similar to the viscosity of the lens matrix in a youthful natural eye. 
     The following matrix calculations are performed using the model eye and its parameters as developed by Gullstrand. The measurements are taken from the average distances and radii of curvature of the Gullstrand Model Eye. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               Radius 
                                
                               
                                   
                               
                                
                               of 
                                
                               
                                   
                               
                                
                               Curvature 
                             
                           
                         
                         
                           
                             
                               
                                 
                                   ( 
                                   meters 
                                   ) 
                                 
                                  
                                 
                                     
                                 
                                  
                                 of 
                                  
                                 
                                     
                                 
                                  
                                 Eye 
                               
                                
                               
                                   
                               
                             
                           
                         
                       
                     
                   
                   
                     
                       Surfaces 
                     
                   
                 
               
               
                 
                   
                     
                       
                         
                           
                             
                                 
                             
                           
                         
                         
                           
                             
                               Indices 
                                
                               
                                   
                               
                                
                               of 
                                
                               
                                   
                               
                                
                               Refraction 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                   
                 
               
               
                 
                   
                     
                       
                         
                           
                             
                               Translation 
                                
                               
                                   
                               
                                
                               Distances 
                             
                           
                         
                         
                           
                             
                               ( 
                               Meters 
                               ) 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                           
                       
                     
                   
                 
               
             
             
               
                 
                   
                     R 
                     
                       ^ 
                       
                         ^ 
                         
                           ^ 
                           ^ 
                         
                       
                     
                   
                   := 
                   
                     
                       ( 
                       
                         
                           
                             0.0078 
                           
                         
                         
                           
                             0.0065 
                           
                         
                         
                           
                             0.009 
                           
                         
                         
                           
                             0100 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             00 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                       
                       ) 
                     
                      
                     
                       
                         
                           CorneaExterior 
                         
                       
                       
                         
                           
                             Cornea 
                              
                             
                                 
                             
                              
                             Interior 
                           
                         
                       
                       
                         
                           
                             I 
                              
                             
                                 
                             
                              
                             O 
                              
                             
                                 
                             
                              
                             L 
                              
                             
                                 
                             
                              
                             Anterior 
                           
                         
                       
                       
                         
                           
                             I 
                              
                             
                                 
                             
                              
                             O 
                              
                             
                                 
                             
                              
                             L 
                              
                             
                                 
                             
                              
                             Posterior 
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                     
                   
                 
               
               
                 
                   
                     N 
                     
                       ^ 
                       
                         ^ 
                         
                           ^ 
                           
                             ^ 
                             ^ 
                           
                         
                       
                     
                   
                   := 
                   
                     
                       ( 
                       
                         
                           
                             1.000 
                           
                         
                         
                           
                             1.3771 
                           
                         
                         
                           
                             1.3374 
                           
                         
                         
                           
                             1.4034 
                           
                         
                         
                           
                             1.336 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                         
                       
                       ) 
                     
                      
                     
                       
                         
                           Air 
                         
                       
                       
                         
                           Cornea 
                         
                       
                       
                         
                           Aqueous 
                         
                       
                       
                         
                           
                             Silicone 
                              
                             
                                 
                             
                              
                             Oil 
                           
                         
                       
                       
                         
                           Vitreous 
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                     
                   
                 
               
               
                 
                   
                     
                       
                         
                           
                             
                                 
                             
                              
                             Cornea 
                           
                         
                       
                       
                         
                           
                             Ant 
                             . 
                             
                                 
                             
                              
                             Chamber 
                           
                         
                       
                       
                         
                           
                             Lens 
                              
                             
                                 
                             
                              
                             Thickness 
                           
                         
                       
                       
                         
                           Vitreous 
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                       
                         
                           
                               
                           
                         
                       
                     
                      
                     t 
                   
                   := 
                   
                     ( 
                     
                       
                         
                           0.00055 
                         
                       
                       
                         
                           0.003 
                         
                       
                       
                         
                           0.003 
                         
                       
                       
                         
                           0.01821 
                         
                       
                       
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                       
                       
                         
                           0 
                         
                       
                     
                     ) 
                   
                 
               
             
           
         
       
     
     The above “R”, “N”, and “t” vectors are referenced by their respective indices as follows 
     
       
         
           
             
               
                 
                   
                     Pc 
                      
                     
                         
                     
                      
                     1 
                   
                   := 
                   
                     
                       
                         N 
                         1 
                       
                       - 
                       
                         N 
                         0 
                       
                     
                     
                       R 
                       0 
                     
                   
                 
               
               
                 
                   Dc 
                   := 
                   
                     
                       t 
                       0 
                     
                     
                       N 
                       1 
                     
                   
                 
               
               
                 
                   Vit 
                   := 
                   
                     t 
                     3 
                   
                 
               
             
             
               
                 
                   
                     Pc 
                      
                     
                         
                     
                      
                     2 
                   
                   := 
                   
                     
                       
                         N 
                         2 
                       
                       - 
                       
                         N 
                         1 
                       
                     
                     
                       R 
                       1 
                     
                   
                 
               
               
                 
                   Da 
                   := 
                   
                     
                       t 
                       1 
                     
                     
                       N 
                       2 
                     
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     Pi 
                      
                     
                         
                     
                      
                     2 
                   
                   := 
                   
                     
                       
                         N 
                         4 
                       
                       - 
                       
                         N 
                         3 
                       
                     
                     
                       R 
                       3 
                     
                   
                 
               
               
                 
                   Di 
                   := 
                   
                     
                       t 
                       2 
                     
                     
                       N 
                       3 
                     
                   
                 
               
               
                 
                     
                 
               
             
           
         
       
     
     Any lens system, including the eye, can be calculated using a series of multiplied matrices, with the first refracting surface, in the case of the invention the exterior of the cornea on the far right, followed by a translation matrix with reduced distance Dc, then the next surface, namely the posterior cornea, right to left 
     
       
         
           
             Sys 
             := 
             
               
                 
                   ( 
                   
                     
                       
                         1 
                       
                       
                         
                           Pi 
                            
                           
                               
                           
                            
                           2 
                         
                       
                     
                     
                       
                         0 
                       
                       
                         1 
                       
                     
                   
                   ) 
                 
                 · 
                 
                   ( 
                   
                     
                       
                         1 
                       
                       
                         0 
                       
                     
                     
                       
                         Di 
                       
                       
                         1 
                       
                     
                   
                   ) 
                 
                 · 
                 
                   [ 
                   
                     
                       ( 
                       
                         
                           
                             1 
                           
                           
                             
                               
                                 - 
                                 Pi 
                               
                                
                               
                                   
                               
                                
                               1 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             1 
                           
                         
                       
                       ) 
                     
                     · 
                     
                       ( 
                       
                         
                           
                             1 
                           
                           
                             0 
                           
                         
                         
                           
                             Da 
                           
                           
                             1 
                           
                         
                       
                       ) 
                     
                     · 
                     
                       ( 
                       
                         
                           
                             1 
                           
                           
                             
                               
                                 - 
                                 Pc 
                               
                                
                               
                                   
                               
                                
                               2 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             1 
                           
                         
                       
                       ) 
                     
                     · 
                     
                       ( 
                       
                         
                           
                             1 
                           
                           
                             0 
                           
                         
                         
                           
                             Dc 
                           
                           
                             1 
                           
                         
                       
                       ) 
                     
                     · 
                     
                       ( 
                       
                         
                           
                             1 
                           
                           
                             
                               
                                 - 
                                 Pc 
                               
                                
                               
                                   
                               
                                
                               1 
                             
                           
                         
                         
                           
                             0 
                           
                           
                             1 
                           
                         
                       
                       ) 
                     
                   
                   ] 
                 
               
                
               
                 
                   
                     
                       The 
                        
                       
                           
                       
                        
                       basic 
                     
                   
                 
                 
                   
                     System 
                   
                 
               
             
           
         
       
     
     Expanding this matrix into a single product matrix can provide the equation illustrated as  FIG. 10 . 
     Solving that equation for Pi1:=1,
         and given the second focal point as Vit (t3), provides the equation illustrated in  FIG. 11         

     
       
         
           
             
                 
             
              
             
               
                 Find 
                  
                 
                     
                 
                  
                 
                   ( 
                   
                     Pi 
                      
                     
                         
                     
                      
                     1 
                   
                   ) 
                 
               
               = 
               18.34277 
             
           
         
       
       
         
           
             
                 
             
              
             
               
                 
                   Ri 
                    
                   
                       
                   
                    
                   1 
                 
                 := 
                 
                   
                     
                       
                         N 
                         3 
                       
                       - 
                       
                         N 
                         2 
                       
                     
                     18.343 
                   
                    
                   
                       
                   
                    
                   By 
                    
                   
                       
                   
                    
                   
                     Snell 
                     ′ 
                   
                    
                   s 
                    
                   
                       
                   
                    
                   Law 
                 
               
                
               
                 
 
               
                
               This 
                
               
                   
               
                
               is 
                
               
                   
               
                
               the 
                
               
                   
               
                
               refracting 
                
               
                   
               
                
               power 
                
               
                   
               
                
               of 
                
               
                   
               
                
               the 
                
               
                   
               
                
               anterior 
                
               
                   
               
                
               surface 
                
               
                   
               
                
               of 
                
               
                   
               
                
               the 
                
               
                   
               
                
               intraocular 
                
               
                   
               
                
               
                 lens 
                 . 
               
             
           
         
       
     
     Ri1=0.0036 Radius of anterior lens surface at rest (in meters)
 
If the optic is 0.006 m in diameter, then the angle of arc is: α:=0 rad
 
     Given 
     
       
         
           
             
               sin 
                
               
                 ( 
                 α 
                 ) 
               
             
             = 
             
               ( 
               
                 0.003 
                 
                   Ri 
                    
                   
                       
                   
                    
                   1 
                 
               
               ) 
             
           
         
       
       
         
           
             
               Find 
                
               
                   
               
                
               
                 ( 
                 a 
                 ) 
               
             
             = 
             
               0.98591 
                
               
                   
               
                
               Radians 
             
           
         
       
       
         
           
             
               0.003 
               0.0036 
             
             = 
             
               0.83333 
                
               
                   
               
                
               rad 
             
           
         
       
       
         
           
             
               0.986 
                
               
                   
               
                
               
                 180 
                 
                   2 
                   · 
                   π 
                 
               
             
             = 
             
               28.24682 
                
               
                   
               
                
               degrees 
                
               
                   
               
                
               in 
                
               
                   
               
                
               the 
                
               
                   
               
                
               relaxed 
                
               
                   
               
                
               state 
             
           
         
       
     
     The half length on the arc 12:=Ri1·0.986
         12=0.00355 (meters,▪) or 12×1000=3.54773 mm
 
Suppose the lens pinches with accommodation 0.0005 meters, or 0.5 mm total—since the arc length has to be constant, the new angle of the half arc is
       

     
       
         
           
             θ 
             := 
             0 
           
         
       
       
         
           
             Given 
              
             
                 
             
              
             that 
           
         
       
       
         
           
             
               
                 12 
                 · 
                 
                   sin 
                    
                   
                     ( 
                     θ 
                     ) 
                   
                 
               
               θ 
             
             = 
             0.00275 
           
         
       
       
         
           
             
               Find 
                
               
                 ( 
                 θ 
                 ) 
               
             
             = 
             1.2045 
           
         
       
     
     The new radius is 
     
       
         
           
             
                 
             
              
             
               
                 R 
                  
                 
                     
                 
                  
                 6 
               
               := 
               
                 0.00275 
                 
                   Sin 
                    
                   
                     ( 
                     
                       1.2045 
                       · 
                       rad 
                     
                     ) 
                   
                 
               
             
           
         
       
       
         
           
             
                 
             
              
             
               
                 R 
                  
                 
                     
                 
                  
                 6 
               
               = 
               0.00295 
             
           
         
       
       
         
           
             
                 
             
              
             
               
                 Power 
                 2 
               
               := 
               
                 
                   
                     N 
                     3 
                   
                   - 
                   
                     N 
                     2 
                   
                 
                 
                   R 
                    
                   
                       
                   
                    
                   6 
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     Power 
                     2 
                   
                   = 
                   22.40785 
                 
               
               
                 
                   This 
                    
                   
                       
                   
                    
                   is 
                    
                   
                       
                   
                    
                   the 
                    
                   
                       
                   
                    
                   power 
                    
                   
                       
                   
                    
                   attainable 
                    
                   
                       
                   
                    
                   in 
                    
                   
                       
                   
                    
                   accomodation 
                 
               
             
             
               
                 
                   
                     
                       Power 
                       2 
                     
                     - 
                     18.3472 
                   
                   = 
                   4.06065 
                 
               
               
                 
                   This 
                    
                   
                       
                   
                    
                   small 
                    
                   
                       
                   
                    
                   change 
                    
                   
                       
                   
                    
                   in 
                    
                   
                       
                   
                    
                   curvature 
                    
                   
                       
                   
                    
                   yields 
                    
                   
                       
                   
                    
                   4 
                 
               
             
             
               
                 
                     
                 
               
               
                 
                   diopters 
                    
                   
                       
                   
                    
                   of 
                    
                   
                       
                   
                    
                   accomodation 
                 
               
             
           
         
       
     
     Those skilled in the art will now see that certain modifications can be made to the apparatus and methods herein disclosed with respect to the illustrated embodiments, without departing from the spirit of the instant invention. And while the invention has been described above with respect to the preferred embodiments, it will be understood that the invention is adapted to numerous rearrangements, modifications, and alterations, and all such arrangements, modifications, and alterations are intended to be within the scope of the appended claims. 
     To the extent the following claims use means plus function language, it is not meant to include there, or in the instant specification, anything not structurally equivalent to what is shown in the embodiments disclosed in the specification.