Abstract:
A phakic intraocular lens includes a body having a flat anterior-facing surface and a curved posterior-facing surface that defines the optical power of the lens. The lens allows fluid to flow between the phakic lens and the iris and between the phakic lens and the natural lens. An enlarged outer rim helps maintain the position of the lens. Some embodiments are provided with openings, channels, or both at the circumferential edge of the flat anterior-facing surface or the lens body to help prevent the flat surface of the lens from sealing against the iris.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 10/988,157 filed 12 Nov. 2004, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/580,424 filed Jun. 17, 2004, and U.S. Provisional Patent Application Ser. No. 60/519,978 filed Nov. 14, 2003; the disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     This invention generally relates to an intraocular lens and, more particularly, to a posterior chamber, phakic intraocular lens. Specifically, the present invention is directed to a phakic intraocular lens having a flat front surface and a curved rear surface at the optical portion of the lens.  
         [0004]     2. Background Information  
         [0005]     Various posterior chamber, phakic intraocular lenses are known in the art. These lenses are implanted directly behind the iris in front of the eye&#39;s natural lens. One drawback with these lenses is the need for an iridotomy that allows fluid to flow from the posterior chamber to the anterior chamber of the eye. The art desires an implant that may be used without an iridotomy. Another drawback with known lenses is the limitation on the size of the optical portion of the lens. The art desires a lens with a large optical portion. The art also desires a lens having a configuration that does not interfere with the fluid flow patterns in the eye while having a structure that maintains a desired location within the eye. Typical known lenses use haptics that span the eye chamber and engage opposed portions of the ciliary bodies to wedge the lens in place. Other lenses use the iris to create centering forces on the lens. The art desires a phakic lens that does not relay on as much contact with the eye to remain in a desired position as known lenses.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention provides a phakic intraocular lens having a flat front surface and a curved rear optical surface to define the optical power of the lens. The lens may be used with or without an iridotomy. The lens has positioning arms that help maintain the position of the lens within the eye. Different configurations for the positioning arms are disclosed. In one embodiment, the positioning arms are short and cannot wedge into opposed portions of the ciliary bodies. In one embodiment of the invention, the rear surface of the positioning arms has a radius of curvature substantially equal to the radius of curvature of the front surface of the natural lens of the eye. The invention also provides a lens having an optical body and a pair of positioning arms wherein the configuration of the lens provides additional space for aqueous behind the lens to help keep the lens spaced from the natural lens.  
         [0007]     The invention also provides a phakic intraocular lens having a flat front surface and a curved rear optical surface to define the optical power of the lens. The lens has an enlarged rim disposed about the optical portion that maintains the lens within a desired position within the eye.  
         [0008]     The invention also provides a lens having a joint between the optical portion and positioning arms with the joint defining channels that prevent the iris from forming a seal with the lens when the lens engages the iris. In another embodiment of the invention, openings are provided in the optical portion and/or the positioning arms.  
         [0009]     Another aspect of the invention is the method of designing the lens based on the measurements of the eye. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a sectional view of the eye having a phakic intraocular lens implanted next to the natural lens.  
         [0011]      FIG. 2  is a front elevation view of a first embodiment of the lens of the invention.  
         [0012]      FIG. 3  is a section view taken along line  3 - 3  of  FIG. 2 .  
         [0013]      FIG. 4  is a front elevation view of the first embodiment of the lens with opposed channels defined between the flat front surface and the positioning arms.  
         [0014]      FIG. 5  is a section view taken along line  5 - 5  of  FIG. 4 .  
         [0015]      FIG. 5A  is an enlarged view of the encircled portion of  FIG. 5 .  
         [0016]      FIG. 6  is a section view, taken from the side, of the first embodiment of the phakic lens and the natural lens showing the relative radii of the rear surface of the phakic lens, the rear surface of the positioning arms, and the front surface of the natural lens.  
         [0017]      FIG. 7  is a section view, taken from the side, of a second embodiment of the phakic lens and the natural lens showing the relative radii of the rear surface of the phakic lens, the rear surface of the positioning arms, and the front surface of the natural lens.  
         [0018]      FIG. 8  is a section view, taken from the side, of a third embodiment of the phakic lens and the natural lens showing the relative radii of the rear surface of the phakic lens, the rear surface of the positioning arms, and the front surface of the natural lens.  
         [0019]      FIG. 9  is a section view, taken from the side, of a fourth embodiment of the phakic lens and the natural lens showing the relative radii of the rear surface of the phakic lens, the rear surface of the positioning arms, and the front surface of the natural lens.  
         [0020]      FIG. 10  shows a comparison of a prior art lens to the lens of the invention with the same optical power. 
     
    
       [0021]     Similar numbers refer to similar elements throughout the specification.  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     A phakic intraocular lens made in accordance with the concepts of the present invention is indicated generally by the numeral  10  in the drawing figures. Lens  10  is positioned in the posterior chamber of the eye in  FIG. 1 . Eye  12  includes a cornea  14 , an iris  16  and a natural lens  18 . Phakic intraocular lens  10  is positioned behind iris  16  and in front of lens  18  so that it influences the light entering natural lens  18  of eye  12 .  
         [0023]     At least a pair of positioning arms  20  extends from opposite sides of lens  10  to help maintain the position of lens  10  with respect to eye  12 . The edges of positioning arms  20  may be rounded to provide a round surface for contact with the zonules. Arms  20  are not designed to be wedged into opposed portions of the ciliary body but may contact the ciliary body or the zonules in different lens sizes and configurations. Numerous types and shapes for positioning arms  20  are known in the art and any of the variety will function with the lens of the present invention. Positioning arms  20  may be rectangular when viewed in elevation as shown in  FIG. 2 . In other embodiments of the invention, three or four positioning arms  20  are equally-spaced about the optical portion of lens  10 . In another embodiment, positioning arms  20  extend entirely about the optical portion of the lens.  
         [0024]     In each of the lens embodiments described in this application, the lens body has a flat front optical surface  30  and a curved rear optical surface  32 . Front surface  30  provides a large flat surface disposed directly behind iris  16  so that lens  10  will smoothly slide against the rear of iris  16  in the event that lens  10  is moved into contact with iris  16 . In most embodiments, the diameter  34  of flat front surface  30  is 6 mm to 9 mm. In some embodiments, diameter  34  may be reduced to 4 mm. The radius of curvature  36  of curved rear optical surface  32  is 14 mm to 21 mm. The specific dimensions may be determined by measuring the optical correction for the patient and then measuring the eye of the patient. This measurement may be performed with ultrasound. Lens  10  is designed after the physical dimensions of the natural lens and iris are known. For example, the overall diameter of the space between the natural lens and iris may be measured and dimension  44  may then be design to prevent lens  10  from wedging itself in place. The curvature of the anterior surface of lens  18  may also be measured to determine curvature  42  that properly vaults lens  18 . In the context of this application the term “flat surface” includes lens structures that have an anterior surface that is slightly curved to prevent undesirable reflections through the pupil. This curvature is insignificant to the optical properties of the lens and thus falls with the definition of “flat surface” as used in this specification.  
         [0025]     Positioning arms  20  are connected to the optical portion of lens  10  at the outer circumference or portions of the outer circumference of the optical portion. Positioning arms  20  may be provided in a wide variety of shapes when view from the front elevation as shown in  FIG. 2 . One rectangular embodiment is shown in  FIG. 2  wherein the width of the rectangle is smaller than the diameter of the optical portion of lens  10 . In another embodiment, the width of the rectangle is equal to the diameter of the optical portion. The connection between the positioning arm  20  and the optical portion of the lens is referred to as the joint  40  of lens  10  even though the optical portion and positioning arms  20  are integrally formed.  
         [0026]     Another feature of lens  10  is that the outer diameter of the optical portion of the lens is the thickest area (in cross section) of lens  10  and forms a bulbous rim  41  about the circumference of the optical portion. Rim  41  does not, however, protrude from the flat front surface of lens  10 . This area is referred to as the outer rim  41 . Rim  41  corresponds to the joints  40  at the locations of the positioning arms  20 . The thick rim  41  is positioned in the gap  43  defined between natural lens  18 , iris  16 , the ciliary body, and the zonules that support lens  18 . The thick, bulbous rim  41  maintains the general position of lens  10  with surface  30  behind the pupil. Rim  41  also functions to prevent lens  10  from slipping through the zonules into the vitreous. Rim  41  also allows the eye to create centering forces on lens  10  when the eye interacts with rim  41 .  
         [0027]     The radius of curvature  42  of the positioning arms  20  is smaller than the radius  36  of curved rear optical surface  32 . This arrangement vaults the rear surface of lens  10  away from natural lens  18  thus allowing space for the aqueous to flow between lens  10  and natural lens  18 . The extra space provided may be seen in the exemplary comparison of  FIG. 10  wherein like-powered lens are overlaid to illustrate the extra aqueous space behind lens  10 . The additional space is hatched in  FIG. 10 . The exemplary lens illustrated I FIG. 10 is one of the type disclosed in U.S. Pat. No. 6,015,435. Lens  10  provides significantly more room between lens  18  and the rear surface of lens  10 . This room allows the aqueous of the eye to flow freely between lens  10  and lens  18  to help keep lens  10  from contacting lens  18 . In one embodiment of the invention, radius  42  is equal to the radius of curvature  43  of natural lens  18 . The tip-to-tip length  44  of positioning arms  20  is greater than the outer diameter of natural lens  18  in the embodiments of  FIGS. 6, 7 , and  8 . In  FIG. 9 , positioning arms  20  are short and have a tip-to-tip length that is shorter than the outer diameter of lens  18 . In the  FIG. 9  embodiment, rim  41  may be larger and more prominent to provide the centering forces. Further, the  FIG. 9  embodiment will not constantly engage the zonules disposed about lens  18 .  
         [0028]      FIGS. 2, 3 , and  6  depict an embodiment of the invention wherein the positioning arms  20  are tapered from the joint to the tip with the joint defines a substantially sharp corner.  FIG. 6  shows one embodiment wherein radius  36  is 20 mm, radius  42  is 10 mm, and radius  43  is 10 mm. The diameter  34  of the optical portion is 7 mm. The tip-to-tip dimension  44  is 12 mm.  
         [0029]      FIGS. 4 and 5  depict an embodiment similar to  FIGS. 2 and 3  except that the joint of  FIGS. 4 and 5  defines channels  46  that prevent joint  40  of lens  10  from forming a seal with iris  16 . Channels  46  do not pass entirely through the body of lens  10  as shown in  FIG. 5A . In other embodiments of the invention, through openings may be provided at joints  40  or in positioning arms  20 . In another embodiment, a small opening is provided in the center of the optical portion. This central opening may have a diameter of 0.8 mm. These channels and openings allow aqueous to flow freely.  
         [0030]      FIG. 7  depicts an alternative embodiment wherein joint  40  defines radiused corners.  FIG. 7  shows one embodiment wherein radius  36  is 14.9 mm, radius  42  is 10 mm, and radius  43  is 10 mm. The diameter  34  of the optical portion (inside the radiused corners) is 7.17 mm with the diameter  48  of the optical portion (outside the radiused corners) being 8.03 mm. The tip-to-tip dimension  44  is 11.88 mm.  
         [0031]      FIG. 8  depicts an alternative embodiment wherein the joint defines radiused corners.  FIG. 8  shows one embodiment wherein radius  36  is 18 mm, radius  42  is 10 mm, and radius  43  is 10 mm. The diameter  34  of the optical portion (inside the radiused corners) is 6.98 mm with the diameter  48  of the optical portion (outside the radiused corners) being 7.18 mm. The tip-to-tip dimension  44  is 12 mm. In  FIG. 8 , the positioning arms have a substantially constant thickness adjacent their outer ends and flat outer ends.  
         [0032]      FIG. 9  depicts an alternative embodiment wherein the joint defines radiused or smoothly-rounded corners.  FIG. 9  shows one embodiment wherein radius  36  is 14.9 mm, radius  42  is 10 mm, and radius  43  is 10 mm. The diameter  34  of the optical portion (inside the radiused corners) is 6.02 mm. The tip-to-tip dimension  44  is 8 mm.  
         [0033]     The lens embodiments of the invention are preferably fabricated from an acrylic. However, various lens materials are known in the art. For instance, it is know that the optical portions of intraocular lenses may be fabricated from polymethyl methacrylate, poly-2-hydroxyethyl methacrylate, methyl methacrylate copolymers, siloxanylalkyl, fluoroalkyl and aryl methacrylate, silicone, silicone elastomers, polysulfones, polyvinyl alcohols, polyethylene oxides, copolymers of fluoroacrylates and methacrylate, and polymers and copolymers of hydroxyalkyl methacrylate, such as 2-hydroxyethyl methacrylate, as well as methacrylic acid, acrylic acid, acrylamide methacrylamide, N,N-dimethylacrylamide, and N-vinylpryrrolidone. Additionally, compounds that absorb ultraviolet or other short wavelength (e.g. below about 400 nm) radiation, such compounds derived from benzotriazole groups, benzophenone groups, or mixtures thereof may be added to the monomers and/or polymers that constitute the implant. Other compounds well known in the art may also be used in fabricated optical portion of lens  10  of the present invention.  
         [0034]     The advantages of the invention are that the flat front surface of the lens can have a larger diameter than lenses with curved front surfaces. The large diameter and large radius of the posterior optical surface allow the lens to be formed in a wide range of optical powers such as those that are needed by patients who are inilligeble for corneal laser surgery. The large diameter optical portion also minimizes halos. The large flat surface minimizes pressure on the iris so that fluid may flow from the posterior chamber to the anterior chamber of the eye. Further, the channels of the invention allow fluid flow even when the joint of the lens contacts the iris. The lens may thus be implanted without an iridotomy. The thick rim disposed about the optical portion of the lens maintains the lens in the desired location.  
         [0035]     The lens may be implanted be folding the lens and slipping the folded lens through the pupil of the eye.  
         [0036]     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0037]     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.