Abstract:
A two optic accommodative lens system. The first lens in the system is fixed in the anterior chamber of an eye. The second lens in the system includes a non-circular ring with radial dimensions that are different in at least two meridians and implanted in the posterior chamber of an eye within the capsular bag. The radial dimension of vertical meridian of the lens approximates the natural diameter of the capsular bag. The optic of the second lens is connected to the ring at the vertical meridian by two or more of haptics. The radial dimension of horizontal meridian of the second lens is slightly larger than the natural diameter of the capsular bag.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of intraocular lenses (IOL) and, more particularly, to accommodative IOLs. 
     The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens. 
     When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL). 
     In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. During this procedure, an opening is made in the anterior capsule and a thin phacoemulsification cutting tip is inserted into the diseased lens and vibrated ultrasonically. The vibrating cutting tip liquifies or emulsifies the lens so that the lens may be aspirated out of the eye. The diseased lens, once removed, is replaced by an artificial lens. 
     In the natural lens, bifocality of distance and near vision is provided by a mechanism known as accommodation. The natural lens, early in life, is soft and contained within the capsular bag. The bag is suspended from the ciliary muscle by the zonules. Relaxation of the ciliary muscle tightens the zonules, and stretches the capsular bag. As a result, the natural lens tends to flatten. Tightening of the ciliary muscle relaxes the tension on the zonules, allowing the capsular bag and the natural lens to assume a more rounded shape. In the way, the natural lens can be focus alternatively on near and far objects. 
     As the lens ages, it becomes harder and is less able to change shape in reaction to the tightening of the ciliary muscle. This makes it harder for the lens to focus on near objects, a medical condition known as presbyopia. Presbyopia affects nearly all adults over the age of 45 or 50. 
     Prior to the present invention, when a cataract or other disease required the removal of the natural lens and replacement with an artificial IOL, the IOL was a monofocal lens, requiring that the patient use a pair of spectacles or contact lenses for near vision. Advanced Medical Optics has been selling an bifocal IOL, the Array lens, for several years, but due to quality of issues, this lens has not been widely accepted. 
     Several designs for accommodative IOLs are being studied. For example, several designs manufactured by C&amp;C Vision are currently undergoing clinical trials. See U.S. Pat. Nos. 6,197,059, 5,674,282, 5,496,366 and 5,476,514 (Cumming), the entire contents of which being incorporated herein by reference. The lens described in these patents is a single optic lens having flexible haptics that allows the optic to move forward and backward in reaction to movement of the ciliary muscle. A similar designs are described in U.S. Pat. No. 6,302,911 B1 (Hanna), U.S. Pat. No. 6,261,321 B1 and U.S. Pat. No. 6,241,777 B1 (both to Kellan), the entire contents of which being incorporated herein by reference. The amount of movement of the optic in these single-lens systems, however, may be insufficient to allow for a useful range of accommodation. In addition, as described in U.S. Pat. Nos. 6,197,059, 5,674,282, 5,496,366 and 5,476,514, the eye must be paralyzed for one to two weeks in order for capsular fibrosis to entrap the lens that thereby provide for a rigid association between the lens and the capsular bag. In addition, the commercial models of these lenses are made from a hydrogel or silicone material. Such materials are not inherently resistive to the formation of posterior capsule opacification (“PCO”). The only treatment for PCO is a capsulotomy using a Nd:YAG laser that vaporizes a portion of the posterior capsule. Such destruction of the posterior capsule may destroy the mechanism of accommodation of these lenses. 
     There have been some attempts to make a two-optic accommodative lens system. For example, U.S. Pat. No. 5,275,623 (Sarfarazi), WIPO Publication No. 00/66037 (Glick, et al.) and WO 01/34067 A1 (Bandhauer, et al), the entire contents of which being incorporated herein by reference, all disclose a two-optic lens system with one optic having a positive power and the other optic having a negative power. The optics are connected by a hinge mechanism that reacts to movement of the ciliary muscle to move the optics closer together or further apart, thereby providing accommodation. In order to provide this “zoom lens” effect, movement of the ciliary muscle must be adequately transmitted to the lens system through the capsular bag, and none of these references disclose a mechanism for ensuring that there is a tight connection between the capsular bag and the lens system. In addition, none of these lenses designs have addressed the problem with PCO noted above. 
     Therefore, a need continues to exist for a safe and stable accommodative intraocular lens that provides accommodation over a broad and useful range. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention improves upon the prior art by providing a two optic accommodative lens system. The first lens in the system is fixed in the anterior chamber of an eye. The second lens in the system includes a non-circular ring with radial dimensions that are different in at least two meridians and implanted in the posterior chamber of an eye within the capsular bag. The radial dimension of vertical meridian of the lens approximates the natural diameter of the capsular bag. The optic of the second lens is connected to the ring at the vertical meridian by two or more of haptics. The radial dimension of horizontal meridian of the second lens is slightly larger than the natural diameter of the capsular bag. 
     Accordingly, one objective of the present invention is to provide a safe and biocompatible intraocular lens system. 
     Another objective of the present invention is to provide a safe and biocompatible intraocular lens system that is easily implanted in the posterior chamber. 
     Still another objective of the present invention is to provide a safe and biocompatible intraocular lens system that is stable in the posterior chamber. 
     Still another objective of the present invention is to provide a safe and biocompatible accommodative lens system. 
     These and other advantages and objectives of the present invention will become apparent from the detailed description and claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is an enlarged cross-sectional view showing the lens system of the present invention implanted in an eye and with the second lens of the system in the far focused position. 
         FIG. 2  is an enlarged plan view of the first lens of the lens system of the present invention. 
         FIG. 3  is an enlarged cross-sectional view showing the lens system of the present invention implanted in an eye and with the second lens of the system in the near focused position. 
         FIG. 4  is an enlarged perspective view of the perimeter ring of the second lens of the lens system of the present invention with the optic removed and in the near focused position. 
         FIG. 5  is an enlarged perspective view of the perimeter ring and additional parts of the second lens of the lens system of the present invention similar to  FIG. 4 . 
         FIG. 6  is an enlarged perspective view of the perimeter ring and additional parts of the second lens of the lens system of the present invention with the optic removed and in the far focused position. 
         FIG. 7  is an enlarged perspective view of the perimeter ring of the optic of the lens system of the present invention in the far focused position. 
         FIG. 8  is an enlarged perspective view of the lens system of the present invention in the near focused position. 
         FIG. 9  is an enlarged perspective view of the lens system of the present invention in the far focused position. 
         FIG. 10  is an enlarged cross-sectional view similar to  FIG. 1  showing the lens system of the present invention implanted in an eye and with the second lens of the system in the far focused position. 
         FIG. 11  is an enlarged cross-sectional view showing the lens system of the present invention implanted in an eye and with the second lens of the system in the near focused position. 
         FIG. 12  is an enlarged perspective view of the optic and perimeter ring of the second lens of a second embodiment of the lens system of the present invention. 
         FIG. 13  is an enlarged perspective view of the optic and perimeter ring of the first lens of a second embodiment of the lens system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As best seen in  FIG. 1 , the present invention comprises two lens assemblies, fixed lens assembly  1  positioned in the anterior chamber of an eye and moving lens assembly  2 , which is positioned in an evacuated capsule C of the eye. Fixed lens assembly  1  comprises fixed lens  3  secured by two or more haptics  4 .  FIG. 2  shows a top view of fixed lens assembly  1 . Lens assemblies  1  and  2  and lenses  3  and  70  may be made from any suitable material such as a thermoplastic, a silicone, a hydrogel or a soft acrylic and contain any desired additives, such as ultraviolet or blue light blocking chromophores. Lenses  3  and  70  may have any suitable design, such aspheric, toric, pseudoaccommodative or multifocal. Those skilled in the art will recognize that lens assemblies  1  and  2  need not be implanted at the same time. For example, lens assembly  2  may be implanted in an eye and the eye allowed to recover from the surgical trauma. After waiting such a healing period, bioptric and other physiological measurements may be made sufficient to calculate an accurate prescription for lens assembly  1 , at which time lens assembly  1  may be implanted. 
       FIG. 1  shows moving lens assembly  2  in a far focusing position, where moving lens  70  is at a posterior location, which is the farthest from fixed lens  3 . Now referring to  FIG. 3 , moving lens assembly  2  is shown in a near focusing position, where moving lens  70  is at an anterior location, which is nearest fixed lens  3 . 
     Taken together, fixed lens  3 , and moving lens  70 , form an optical system, whose focus changes with a corresponding change in the distance between the lenses  3  and  70 . The actuation of moving lens assembly  2  will be disclosed as comprising a compound action, powered by the ciliary muscle M of the eye. 
       FIG. 4  shows moving lens assembly  2  in the near focusing position, with some parts removed for clarity. End walls  11  and  12  are rigidly connected to one another by struts  13  and  14 , so that end walls  11  and  12  cannot move relative to one another. 
     Pad  21  is flexibly connected by flex wall  23  to end wall  12  at one end, and flexibly connected by flex wall  26  to end wall  11  at the other end. Thus pad  21  is relatively free to move inward and outward in the directions indicated by reference numeral  27 . 
     Similarly, pad  22  is flexibly connected by flex wall  24  to end wall  12  at one end, and flexibly connected by flex wall  25  to end wall  11  at the other end. Thus pad  22  is relatively free to move inward and outward in the directions indicated by reference numeral  28 . Taken together, end walls  11  and  12  and pads  21  and  22  are arranged generally in the shape of an ellipse, where end walls  11  and  12  are at the ends of a long axis and pads  21  and  22  are at the ends of a short axis. 
     As seen in  FIG. 5 , moving lens assembly  2  in the near focusing position (some portions have been removed for clarity). Attached to pad  21  is bracket  31  having a curved shape passing around, without contacting, flex wall  23 . Bracket  31  is raised so as to pass over, without contacting, strut  13 . Link  33  is pivotably connected to bracket  31  by mean of live hinge  32 . Link  33  is pivotably connected to end block  35  by means of live hinge  34 . The various parts are symmetrically arranged about the long axis, so attached to pad  22  is bracket  39 , having a curved shape passing around, without contacting, flex wall  24 . Bracket  39  is raised so as to pass over, without contacting, strut  14 . Link  37  is pivotably connected to bracket  39  by mean of a live hinge  38 . Link  37  is pivotably connected to end block  35  by means of a live hinge  36 . Similarly, attached to pad  22  is bracket  41 , having a curved shape passing around, without contacting, flex wall  25 . Bracket  41  is raised so as to pass over, without contacting, strut  14 . Link  43  is pivotably connected to bracket  41  by mean of live hinge  42 . Link  43  is pivotably connected to an end block  45  by means of live hinge  44 . The various parts are symmetrically arranged about the long axis, so attached to pad  21  is bracket  49 , having a curved shape passing around, without contacting, flex wall  26 . Bracket  49  is raised so as to pass over, without contacting, strut  13 . Link  47  is pivotably connected to bracket  49  by mean of live hinge  48 . Link  47  is pivotably connected to end block  45  by means of live hinge  46 . The term “live hinge” is known in the field of plastics as a thin belt of material, which provides a pivoting action. Each live hinge noted by reference numerals  32 ,  34 ,  36 ,  38 ,  42 ,  44 ,  46 , and  48  allows rotation about an axis perpendicular to the plane of the ellipse. 
     Links  33 ,  37 ,  43 , and  47  are positioned at a certain angle, one that amplifies movement. For example, if pads  21  and  22  are each moved outward “one unit of distance,” then the links power end blocks  35  and  45  to each move inward “more than one unit of distance.” 
     Now referring to  FIG. 6 , moving lens assembly  2  is shown in the far focusing position where pads  21  and  22  each have been moved outward as shown by vectors noted by reference numerals  91  and  92 , while end blocks  35  and  45  each have been powered inward as shown by vectors noted by reference numerals  93  and  94 . For the particular geometry of the embodiment shown, vectors  93  and  94  each have a magnitude more than twice that of vectors  91  and  92 . 
       FIG. 7  further discloses the construction of moving lens assembly  2  in the far focusing position, where some parts previously shown in  FIG. 6  have been removed for clarity. Yoke  51  is pivotably connected to end block  35  by live hinge  52 . One arm of yoke  51  is pivotably connected to lens block  71  by live hinge  53 . The other arm of yoke  51  is pivotably connected to lens block  72  by live hinge  54 . Yoke  61  is pivotably connected to end block  45  by live hinge  62 . One arm of yoke  61  is pivotably connected to lens block  71  by live hinge  63 . The other arm of yoke  61  is pivotably connected to lens block  72  by live hinge  64 . Lens blocks  71  and  72  are each fixed on opposing edges of moving lens  70 . Vectors noted by reference numerals  93  and  94  show the end block movements previously described. Vectors noted by reference numerals  95  and  96  show the corresponding movements of lens blocks  71  and  72 , having been powered by yokes  51  and  61 . Each live hinge noted by reference numerals  52 ,  53 ,  54 ,  62 ,  63 , and  64  allows rotation about an axis parallel to the short axis of the ellipse. 
     Yokes  51  and  61  are positioned at a certain angle, one that amplifies movement. For example, if end blocks  35  and  45  are each moved “one unit of distance,” then the yokes power lens blocks  71  and  72  (along with moving lens  70 ) to each move “more than one unit of distance.” For the particular geometry of the embodiment shown, vectors  95  and  96  each have a magnitude more than twice that of vectors  93  and  94 . 
     Thus, there is a compound action wherein the amplifying movement of links  33 ,  34 ,  43 , and  44  is further multiplied by the amplifying movement of yokes  51  and  61 . For the particular geometry of the embodiment shown, vectors  95  and  96  each have a magnitude about five times that of vectors  91  and  92  (shown in  FIG. 6 .). In other words, if pads  21  and  22  move 0.2 mm inwardly, lens  70  will move about 1.0 mm axially in this embodiment. 
     Referring to  FIG. 8 , which shows all of the parts comprising the moving lens assembly  2  in the near focusing position. Pads  21  and  22  are located inward having powered the moving lens  70  to a high (anterior) location. 
       FIG. 9  shows all of the parts comprising moving lens assembly  2  in the far focusing position. Pads  21  and  22  are located outward having powered the moving lens  70  to a low (posterior) location. Yokes  51  and  61  fit within, without making contact with, struts  13  and  14 . 
     In  FIGS. 1 and 3  moving lens assembly  2  is shown in cross section along the long axis of the ellipse. The long length of moving lens assembly  2  stretches the capsule C in this direction, which secures moving lens assembly  2 , and which tends to slacken or reduce tension on the nearby zonules Z. This slackening of zonules insulates movement of the capsule in this area which would otherwise be caused by movement of the ciliary muscle M. 
       FIG. 10  is a cross sectional side view of the present invention taken along the short axis of the ellipse, showing moving lens assembly  2  at the far focusing position, where moving lens  70  is at a posterior location, which is far from fixed lens  3 . Capsule C is under circumferential tension because it is stretched along the long axis as stated before. Consequently, the sides of capsule C have a tendency to move inward. But the movement is prevented by tense zonules Z. In this view, the ciliary muscle is relaxed, which is consistent with far viewing, and a muscle span diameter D is large. 
     Now referring to  FIG. 11 , the present invention is shown in cross section along the short axis of the ellipse, showing moving lens assembly  2  at the near focusing position. In this view, the ciliary muscle M′ is constricted, consistent with straining for near viewing, causing a muscle span diameter D′ to be smaller (than D of  FIG. 10 .) Therefore, the zonules Z have allowed the sides of capsule C to move closer together, consequently pushing pads  21  and  22  to move closer together, with the result that moving lens assembly  2  has assumed the near focusing position where, by the compound action previously described, moving lens  70  has moved to the anterior position, near fixed lens  3 . 
     Also referring to  FIG. 11 , while the thickness of pads  21  and  22  is designed to enable inward and outward movement, the heights of pads  21  and  22  and end walls  11  and  12  are designed so as to prevent the anterior and posterior capsule membranes from moving closer to each other. This design feature improves the distance vision stability of the user. 
     Alternatively, both lens assemblies of the lens system of the present invention may be placed in the posterior chamber, preferably in the capsular bag. As seen in  FIGS. 12 and 13 , lens  70 ′ may be integrally formed with lens assembly  2 ′ and connected to end walls  203  by haptics  205 . Lens assembly  2 ′ is generally oval in shape with open interior  223 . Lens assembly  1 ′ is formed as a separate piece from lens assembly  2 ′ and sized slightly smaller so as to fit snugly or nest within open interior  223  of lens assembly  2 ′. Lens assembly  1 ′ contains lens  3 ′ that is attached to ring  215  by haptics  217 . Ring  215  is attached to pads  219  through links  221 . Links  219  transmit compressive forces on pads  203  to lens  3 ′ through ring  215  and haptics  217  in a manner similar to that described above, causing lenses  3 ′ and  70 ′ to move axially relative to each other. The construction of lens assemblies  1 ′ and  2 ′ allow the lens system to be implanted entirely within the capsular bag. 
     This description is given for purposes of illustration and explanation. It will be apparent to those skilled in the relevant art that changes and modifications may be made to the invention described above without departing from its scope or spirit.