Abstract:
An accommodative intraocular lens is provided to replace a natural lens. The intraocular lens structure includes an optical portion and a haptic portion. The optical portion includes a replacement lens while the haptic portion includes the structure that holds the lens in position while keeping the anterior capsular sac taunt and annular in shape. The haptic in the present invention stabilizes the annular structure of the peripheral zone at the capsular sac&#39;s largest diameter and also stabilizes the conical structure of the capsular sac as well. The haptic structure includes a helical coil of increasing radius from the lens to the terminating annular ring that thus forms a conical coil spring. Compression and relaxation of the coiled (spring) haptics between the anterior and posterior capsule, during tightening and relaxation of lens zonule and ciliary body, move the lens to anteriorly and posteriorly and induces accommodation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   REFERENCE TO A MICROFICHE APPENDIX 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of medical technology in general. In particular, the present invention relates specifically to an improved intraocular lens designed specifically such that the focal length between the lens and the retina can be varied in a manner similar to the manner the focal length of a natural lens varies. Known art may be found in U.S. Class 623, subclasses 5 and 6 as well as in other classes and subclasses. 
   2. Description of the Known Art 
   As will be appreciated by those skilled in the art, a replacement intraocular lens may be implanted to replace a natural lens for patients requiring such treatment as for example in cataract removal. These replacement surgeries have become more common recently as a preferential method for addressing certain ocular ailments. Details of a typical procedure are contained in U.S. Pat. No. 6,364,906 to Baikoff, the teachings of which are hereby expressly incorporated by reference. 
   A replacement intraocular lens consists of biocompatible material that may be characterized as having two sections. The first section is termed an optical part, which is the lens. The second section is termed a haptic part, which is the structure that holds the lens in position while keeping the anterior capsular bag taunt and annular in shape. Both these functions are important for proper vision to result from the replacement surgery. 
   The optical requirements for replacement lens have been well established. Most lens materials currently used also allow the surgeon to fold the lens during insertion so that it can be made to pass through a very small slit, 2 to 4 mm in length, in the eye to gain access into the capsular bag. 
   The haptic part is still evolving however. The haptic structure needs to contact the interior of the anterior capsular sac essentially for 300 to 360 degrees to properly stretch the sac to anchor the replacement lens properly while minimizing rupturing or tearing of the bag. Some early haptic structures had two connections to the lens and formed two loops. An example of this structure is shown in U.S. Pat. No. 4,494,254 to Lopez. 
   Later haptic structures used only one connection to the lens. Examples of such structures may be seen in U.S. Pat. No. 4,842,600 to Feaster; U.S. Pat. No. 4,950,290 to Kamerling; U.S. Pat. No. 5,133,751 to Bayer; and U.S. Pat. No. 6,364,906 to Baikoff. These haptic structures have one end secured in the lens structure. The other haptic end has a single spiral that leads into an annular section that forms a ring. The known haptic structures, whether with one or two connections to the lens, are essentially coplanar with the lens. That is, when the intraocular lens was implanted correctly, the annular coil or ring portion of the embedded haptic touched the inside of the capsular sac through a 300 to 360 degree arc and the lens portion was substantially in the same horizontal plane as the haptic portion. 
   Some haptic structures, for example, U.S. Pat. No. 4,842,600 to Feaster, had an adjustment for the diameter of the annular part, which was accomplished by affixing the diameter with slide holes on the ends of the haptic structure. Some others used horizontal tensioning of the annular part to obtain the correct diameter for maintaining contact with the capsular bag. For example, U.S. Pat. No. 4,950,290 to Kamerling; U.S. Pat. No. 5,133,751 to Bayer; and U.S. Pat. No. 6,364,906 to Baikoff. 
   U.S. Pat. No. 5,653,752 describes a method for adjusting the curvature of the corneal using intrastromal corneal rings. This work is only marginally relevant to the present invention which uses the natural focusing mechanism of the eye to adjust the lens position relative to the retina and also influences the shape of the capsular sac. 
   The intraocular replacement lens discussed heretofore attempted to simultaneously place the lens and hold it in correct position while also giving horizontal geometric stabilization to the capsular bag. The known art however fails to provide a suitable replacement structure that retains the ability of the implant recipient to be able to focus on both close and far objects as a natural lens does or that stabilizes both the horizontal and vertical geometries of the capsular bag. Thus, most implant recipients require corrective devices to achieve normal vision. 
   Thus, a need exists for an improved intraocular lens implant structure that can be moved to accommodate focal length adjustments in a fashion similar to that of a natural lens to retain the ability to focus on objects at different distances from the observer. It is also desirable to provide an interocular lens that stabilizes the capsular bag in both the vertical and horizontal axes. It is still further desirable to provide such stabilization conically to mimic the natural shape of the capsular bag. An improved replacement lens would permit the recipient to use their eyes as before and more particularly would enable the recipient to flex the lens to properly focus images upon their retina. 
   SUMMARY OF THE INVENTION 
   In accordance with one exemplary embodiment of the present invention, an accommodative intraocular lens is provided that may be implanted to replace the eye&#39;s natural lens following a conventional surgery to remove the natural lens. The intraocular lens structure includes an optical portion and a haptic portion. The optical portion includes a replacement lens while the haptic portion includes the structure that holds the lens in position while keeping the anterior capsular sac or bag taunt and annular in shape. 
   A requirement for the haptic portion is that it must contact the interior of the capsular bag sufficiently to provide proper stretching to minimize the chances of rupturing the bag. The capsular bag is an ovate shaped body and as such has a three dimensional shape. The haptic in the present invention stabilizes not only the annular structure of the peripheral zone at the capsular sac&#39;s largest diameter but also stabilizes the conical structure of the capsular sac as well. Thus, stabilization is provided in both the horizontal and vertical axes. The structure of the haptic in the current invention is such to accomplish this. The structure may also provide peripheral support if formed with a parabolic cross-section. 
   In one exemplary embodiment, the haptic structure of the present invention aids in maintaining the exterior of the posterior portion of the capsular sac, i.e. that portion of the capsular sac anterior to the plane of its maximum diameter, in a parabolic cone. The haptic structure includes a helical coil of increasing radius from the lens to the terminating annular ring that thus forms a conical coil spring. This spring shape has characteristics that are responsive to the focusing muscles of the eye. The terminal end of the spring includes a bulbous enlargement that prevents the tip from injuring the capsular sac during insertion. 
   Thus, a principal object of the present invention to provide an intraocular replacement lens that is accommodative in that it can be focused in a manner similar to a natural eye lens. 
   Another object of the present invention is to provide a structure that prevents damage to the capsular sac during the implantation process. 
   Yet another object of the present invention to provide stabilization to the anterior portion of the capsular sac so that it maintains a natural shape. 
   Yet another object of the present invention is to provide a replacement lens that stabilizes the capsular bag in both the horizontal and vertical axes. 
   A related object of the present invention is to provide a replacement lens that stabilizes the capsular bag in both the horizontal and vertical axes while also providing peripheral support for the capsular bag. 
   Another object of the present invention is to provide a replacement lens that may be flexed like a natural lens. 
   An object of the present invention is to provide a replacement lens that has a biasing mechanism to permit lens relocation relative to the retina. 
   These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the descriptive sections. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views: 
       FIG. 1  is a perspective view of an exemplary embodiment in accordance with the present invention; 
       FIG. 2  is an elevational view taken generally from the side thereof; 
       FIG. 3  is a top plan view thereof; 
       FIG. 4  is an environmental view taken generally from the side with portions removed or shown in section for clarity; 
       FIG. 5  is an enlarged view of the area designated by circle  5 — 5  in  FIG. 4  thereof and we present eye and lens in accommodative state with the lens moved forward; 
       FIG. 6  is an enlarged view of the area designated by circle  5 — 5  in  FIG. 4  but showing its position and appearance in the nonaccomodative state; 
       FIG. 7  is a top plan view with portions removed or shown in section for clarity and illustrating the partial insertion of the intraocular lens into an eye; and, 
       FIG. 8  is a top plan view with portions removed or shown in section for clarity and illustrating the complete insertion of the intraocular lens into an eye. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An exemplary embodiment in accordance with the present invention is generally referred to as replacement accommodative intraocular lens. The lens is generally designated by reference numeral  20  in  FIGS. 1–8 . The accommodative intraocular lens consists of two primary parts, the lens or optical portion  25  and the haptic portion  30  that holds the optical lens  25  in the correct position relative to the eye, both the radial and the elongated symmetry of the eye. The replacement lens  20  is normally inserted into the capsular bag  22  as will be discussed hereinafter. 
   The lens structure  25  can be made of polymethylmethacrylate (PMMA), silicone, or acrylic, all of which are biocompatible with human physiology and known to those skilled in the art. The optical requirements for the lens are also established common knowledge to those skilled in the art. That is, the lens will meet certain dimensional requirements as well as sanitary requirements and the like. 
   The haptic structure  30  can also be made from PMMA, proline, or acrylic strands. All these materials are biocompatible as discussed hereinbefore. Other materials may also be utilized and are deemed within the scope of the invention. The thickness of the strand and its spring constant are as needed to simulate the compressibility of a natural lens. It has been found for example that a compressibility in the range of approximately one to ten pounds per square inch is acceptable. 
   The haptic structure  30  includes a proximate end  35 . The proximate end  35  is secured to the side of the lens structure  25  at a slight angle to the plane of the lens  25  and may even be inserted therein. The angle is selected so that after implantation into the eye, the lens  25  will be positioned in a plane parallel to the plane of the haptic&#39;s terminal annular ring. In this position, the lens pushes against the inside of the capsular sac  22  with equal or nearly equal forces at all points of contact in a manner similar to the natural lens. 
   The haptic&#39;s anterior end  40  may have a bulbous shape or other shape to avoid rupture during insertion into the capsular bag  22 . 
   The haptic structure  30  extending between the proximate point of attachment  35  and the terminal end  40  forms a thin cylindrical strand arranged in a substantially helical shape, i.e. a non-plane curve whose tangents are all equally inclined to a given plane. In this instance, the helical shape includes a plurality of coils  50  that get diametrically larger as one transverses from the point of embedment  35  to the terminal annular ring  45 . Thus, each revolution made by the haptic may be referred to as a coil  50 . 
   In one preferred embodiment, at least two coils are present although more may be utilized. The coil spacing  55  coupled with the haptic&#39;s natural resistance to deformation gives rise to a spring action between the anterior and the posterior of the device  20  when properly positioned in the capsular bag  22 . 
   The spacing between individual coils  55  is best seen in  FIG. 2 . The parabolic outline  58  formed by (shown by the dashed line in  FIG. 2 ) the exterior from the proximate end  35  to the anterior portion  40  of the accommodative intraocular lens  20  is shown as well. Thus, the entire lens structure  20  forms a conic support for the capsular bag  22 . It is also readily apparent from  FIG. 2  that the terminal portion of the annular ring  45  of the un-implanted accommodative intraocular lens  20 ) does lie in a separate plane that is parallel to the optical lens  25 . This feature facilitates operation of the accommodative intraocular lens and will be discussed in detail in subsequent sections herein. 
   In one exemplary embodiment, the coil spacing extends vertically approximately 9 mm. While the lens may be of varying diameters, a diameter of 7 mm has been suitable in many instances. Of course, other dimensions are possible for both and are within the scope of the present invention. 
   In  FIG. 3  the nature of the lateral spacing of the helix coils is readily apparent. The terminal coil  55  of the helix forms at least five sixths of an annular ring that lies in a plane parallel to the plane of the lens  25 . The terminal annular ring as used herein denotes a circular structure that completes an arc of circa of approximately 300 degrees and has a gap of circa 60 degrees so that it may contract or expand horizontally after it is implanted. 
   An exemplary general environmental embodiment of the accommodative intraocular lens is shown in  FIG. 4 . Of particular note is the location of the optics in the anterior portion of the eye. The focal length is the distance from the lens  25  and the retina  70 . It should be understood that the eye is naturally focused by changing the focal length and/or the curvature of the natural lens. The portion of the eye where the accommodative intraocular lens will be located is shown in greater detail in  FIGS. 5 and 6 . 
   When the accommodative intraocular lens  20  is implanted in the eye as seen in  FIG. 5 , the terminal ring  60  will fit into the portion of the capsular sac  22  with the largest diameter, and will be stabilized there as to move in the posterior direction will cause the terminal ring  60  to contract. This contraction is resisted by the spring action of the haptic&#39;s terminal annular ring  60  to being compressed into a ring of smaller diameter. Movement in the anterior direction is resisted by this same force as well as that arising from the spring action of the spring formed by the helix  30 , which also keeps the lens  25  firmly positioned correctly in the center of the anterior portion of the capsular sac  22 . This spring action of the helix is selected such that it is responsive to the magnitude of force produced by the natural focusing muscles of the eye, which are the lens zonules  75  in combination with the ciliary bodies  80 . The different spring actions are obtained by using increasing diameters of the strands that compose the haptic  30 . 
   The accommodative intraocular lens adjusts focal length by moving from a non-accommodative state to an accommodative state. The non-accommodative state occurs when the ciliary bodies  80  are relaxed which maximally tightens the zonules  75  and applies tension to the capsular sac  65  as is shown in  FIG. 6 . While in non-accommodative state, the capsular sac  65  is stretched thin and the coil spring of the haptic  30  is compressed. 
   In the accommodative state as shown in  FIG. 5 , the ciliary bodies  80  are contracted, thereby loosening the zonules  75  which lessen the tension on the capsular sac  65 . As the tension is removed, the haptic&#39;s spring properties cause it to distend and push the lens more anterior. This anterior lens motion effectively increases the power of the lens allowing the implantee to focus on near objects. The spring qualities will thus effectively emulate the natural lens&#39;s characteristics in regard to compression and distention and move the lens posteriorly and anteriorly. 
   To implant the accommodative intraocular lens, an incision  85  shown in  FIG. 7  is made and the cataract removed in the usual manner. If capsulorrhexis is done during the cataract removal, the diameter of the circular tear to the anterior portion of the capsular sac should be slightly smaller than the lens diameter that is to be subsequently implanted. Note that the capsular sac  65  is behind the iris  90  and the dashed line depicts its largest diameter. The bulbous end  40  is inserted through the incision  85  and directed into the capsular sac  65 . The accommodative intraocular lens  25  is then rotated as indicated by arrow  95  until the entire haptic  30  is within the capsular sac  65 . The lens  25  should follow last. The lens  25  is inserted by folding it or by enlarging the incision  85  either action is done immediately prior to its insertion through the incision  85 . 
   After the accommodative intraocular lens is inserted as shown in  FIG. 8 , its proper placement and alignment should be checked and adjusted as needed. The haptic&#39;s terminal ring  60  terminal ring should be at the largest diameter of the capsular sac  65 . The lens  25  should be placed in the center of the pupil  95 . If capsulorrhexis was done during the cataract removal, the circular tear to the anterior portion of the capsular sac should be positioned so that it is just over the edge of the implanted lens  25 . The completion of the operation is in the normal and usual manner. 
   In one exemplary embodiment, the intraocular accommodative lens replaces at least a portion of a natural lens in the capsular bag of the eye. The lens is supported in the eye by a haptic structure that maintains a desirable shape in the capsular bag to subsequently facilitate focusing of the eye as would naturally occur when focusing and to thus maintain the accommodavite functionality of a fully functional normal eye. The haptic structure thus permits the eye to focus accommodatively to preserve or enhance the patient&#39;s sight. 
   The lens structure uses a biocompatible material such as polymethylmethacrylate, silicone and acrylic or the like. 
   The haptic structure extends, preferentially integrally, from the lens. The haptic structure includes a plurality of coils. The plurality of coils provide a biasing force. The biasing force moves the lens structure accommodatively both anteriorly and posteriorly in the eye. 
   The plurality of coils ideally form a conic structure. The conic structure maintains a desirable shape for the capsular bag. The haptic includes a plurality of substantially horizontally disposed peripheral surfaces  105  adapted to maintain outward pressure against the internal wall of the capsular bag to maintain its diametric and horizontal extent in a fashion to mimic a fully function and normal human bag. The haptic also includes a plurality of substantially vertically disposed peripheral surfaces  100  adapted to maintain outward pressure against the internal wall of the capsular bag to maintain its vertical extent in a fashion to mimic a fully function and normal human bag. 
   One type of advantageous conic the plurality of coils may assume is that of a parabilic helix. In a parabolic helix, the helix may be described as having a vertical parabolic cross-section. Thus, one axis of a cross-section may be said to lie in a vertical plane while another may be said to lie in a horizontal plane. 
   It is desirable for the base of the helix to be seated against an anterior portion of the bag adjacent the largest diameter of the anterior portion. In this fashion, the helix is seated rearwardly in the bag and adapted to bias the lens against the posterior portion of the eye in a desirable configuration. 
   In all described configurations of the present invention, the haptic moves the lens in response to natural eye movements to focus an object to be seen upon the retina of the eye while maintaining the desirable shape of the capsular bag. 
   It is interesting to also note that the lens may be placed in the capsular bag upside down and will still have its accommodative properties as previously described, though the lens power calculation constant will differ. 
   From the foregoing, it will be seen that this invention is one well adapted to obtain all the ends and objects herein set forth, together with other advantages which are inherent to the structure. 
   It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
   As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.