Abstract:
A lens implant serves to replace the lens body of an eye and possesses substantially the same size and shape. It is elastic such that the eye gets back its capability for accommodation. The lens implant has two parts with differing refractive indices and/or differing shapes, which allows to adapt the focal length and shape to specific requirements in simple manner. A distal part is prefabricated as pre-made lens part, while a proximal part can preferably be brought into the lens capsule in a flowable state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Swiss patent application No. 0212/00, which has been filed on 3 Feb. 2000 and of which the entire enclosure is included herein by reference. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not Applicable 
     REFERENCE TO A “MICROFICHE APPENDIX” 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The invention relates to a lens implant and a kit and a method for producing a lens implant. 
     A lens implant of this kind is known e.g. from U.S. Pat. No. 4,608,050 or WO 89/00029. It consists of a flexible body which replaces the lens body of the eye. Its shape and size correspond substantially to the one of the typical lens body. Due to its flexibility it allows an good accommodation of the eye. 
     In order to adjust this lens implant to the individual requirements of an eye, a plurality of implant bodies with various different refractive indices must be may available. This necessitates large expenditures. It has been found, furthermore, that the implant bodies meet the requirements regarding stability and simultaneous accommodation properties in a limited manner only. 
     FR 2.698.264 describes a lens consisting of two partial lenses between which a filler mass is arranged. The part lenses form the outer shape of the lens and replace the lens capsule. Because to this connecting the lens to the ocular accommodation mechanism becomes difficult. Furthermore, the mechanical properties of the lens are quite different from the ones of a natural lens which renders the accommodation more difficult. 
     In U.S. Pat. No. 5,275,623 a lens implant is disclosed which consists of a bag with two lenses. The bag is filled by a gas or a liquid. Due its symmetry, however, this lens features properties that basically deviate from the ones of a natural lens so that it hardly can be satisfactory in practice. 
     BRIEF SUMMARY OF THE INVENTION 
     Thus, there is the object to provide a lens implant and a kit and a method, respectively of the kind mentioned above which avoid these drawbacks. 
     This object is met by the lens and the kit and the method, described herein. 
     The lens implant according to the invention consists thus of a first deformable part and a second part, wherein the two parts have different refractive index and/or different elastic deformability. The first part forms the proximal portion and the second part a distal portion of the lens implant. 
     Accordingly, the implant can be set together of two differing parts which allows to adjust the focal distance and/or the mechanical properties to suit the respective requirements in a simple way. Thus, the first part can e.g. basically define the size and the volume, respectively, of the lens and ensure the accommodation while by choosing the second part the focal distance and/or the distal shape can be set. 
     The implant has essentially the shape of the lens body to be replaced so that it fits into the lens capsule and fills same properly. To this end the distal surface of the implant should have a stronger curvature than the proximal surface. 
     The first part consists preferably of a material which is cureable intraoccularly from a flowable to an elastically deformable state so that it can be made to adapt to the shape of the lens body replaced in a simple way. 
     For a good accommodating capability the first part should be better elastically deformable than the second part, specifically if latter defines the distal surface of the lens implant. 
     The second part can be designed elastically deformable, suitable for introduction into the lens capsule in a rolled up or folded state. This is specifically advantageous in combination with a cureable first part, because the first part can be used in this case for filling the lens capsule and guarantees accommodation capability, while the focal distance of the lens implant is given by the second part. 
     Preferably, the second part forms the distal portion of the lens implant so that it forms a wall which separates the first part from the distal part of the lens capsule. This allows to remove, if necessary, the distal part of the lens capsule if such should become opaque. 
     The kit for the production of such lenses includes preferably at least one flowable filling material and a plurality of pre-shaped lens parts for the forming the second part. The lens parts feature various different shapes and/or refractive indices. Thus, it is possible to produce with only one single filling material a plurality of lens implants of various differing focal distances and shapes. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further embodiments, advantages and applications of the invention follow from the following description with reference to the following drawings. 
         FIG. 1  is a section through a normal eye, 
         FIG. 2  is a section through an eye with a lens implant, 
         FIG. 3  is a possible production method for the lens implant and 
         FIG. 4  is a section through an eye with an alternative embodiment of the lens implant. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The parts of the eye that are the most important ones in the present context are illustrated in  FIG. 1  and include a lens  1 , consisting of a lens capsule  2  and a lens body  3 , an iris  4  and a cornea  5 . 
     The lens  1  is an elastic body of which the curvature changes upon a contraction of Müller&#39;s muscle  6 , so that an accommodation of the eye to various focal distances becomes possible. With increasing age, however, the lens body  3  becomes harder, which leads to a partial or complete loss of the accommodation property. 
     The present invention relates to a lens implant which replaces the lens body  3  of the eye. Such a lens is illustrated in  FIG. 2 . It consists of two transparent parts  10 ,  11  which abut against each other and which together have about the same size and shape as the replaced lens body  3  accommodated to infinity. Thus a distal or convex surface  12   a  of the lens implant is curved stronger than a proximal surface  12   b  as is the case at the lens body. The term proximal denotes, in this context, the lens side facing the cornea  5 , the term distal the lens side facing the retina (not shown). 
     The lens implant has the same size and shape as a natural lens body when it has a convex proximal surface with a radius of curvature between 8.4 and 13.8 mm, a convex distal surface with a radius of curvature between 4.6 and 7.5 mm and a thickness between 2.8 and 5.5 mm. The typical equator amounts for eyes of grownups to about 9 to 11 mm. Typical proximal and distal radii of curvature are 10 and 6 mm, respectively. 
     The lens implant, i.e. specifically its first part  10 , features optical and elastic properties which are similar to those of a lens body with a good accommodation capability. It is usually enclosed tightly by the lens capsule  2  and generates, just as a natural lens body, an intracapsulate pressure. Upon contraction of the Müller&#39;s muscle  6  the curvature of the surfaces of the lens implant, and accordingly its focal width, changes. Thus, the lens implant gives a natural accommodation capability to the eye. To this end the volume of the first or proximal part  10  should be larger than the one of the second or distal part  11 . Preferably also the total diameter perpendicular to the axis should be larger at the first part  10  than at the second part  11 . 
     The two parts  10 ,  11  of the lens implant preferably feature refractive indices that differ from each other. During the production of the lens the first, proximal part  10  is made to suit the size and shape of the lens body  3  to be replaced whereas the second, distal part  11  is a prefabricated, elastic, shaped body. 
     When producing the lens the two parts  10 ,  11  fulfil different objects. The proximal part  10  defines the volume of the lens. The distal part  11  renders stability to the rear lens portion and allows to adjust the focal distance to the respective eye individually. To this end a kit is available for the person skilled in the art for producing the lens which includes the flowable filling material and a plurality of pre-fabricated lens parts. The lens parts differ from each other in their refractive index and/or their shape. 
     The lens implant is produced by bringing together the flowable filling material and one of the lens parts  10 ,  11  and the filling material is cured to the desired rigidity. This can proceed outside of the eye or intraoccularly. Hereto, the eye is initially measured in order to determine the focal distance and the shape of the lens body  3  and, respectively, in order to determine from the properties of the eye the desired refractive index of the implant. From this it can be calculated which of the available lens parts  10 ,  11  shall be used so that the lens implant imitates the desired focal distance as close as possible. 
     In a preferred production method the lens implant is produced intraoccularly. Hereto, in the first step a small opening is cut into the lens capsule  2  and the lens body  3  is removed. This proceeds preferably by ultrasonics, laser technique, phacoemulsification or laserfakoemulsification. Corresponding methods are known to the person skilled in the art. 
     The distal part  11  of the lens is introduced thereafter into the lens capsule  2  which has been hollowed accordingly. In order to allow the lens part  11  to be inserted even through such a small opening, it is elastically deformable so that it can be rolled up or folded and be inserted by means of an injection instrument. An instrument of this kind is disclosed e.g. in U.S. Pat. No. 5,620,450. 
     The distal part  11  which has been inserted extends and roughly attains the desired position in the lens capsule  2 . In a relaxed state it has a concave-concave curvature such as is disclosed in  FIGS. 2 and 3 . It forms the distal side of the lens implant and the shape of its convex surface  12   a  corresponds to the one of the distal surface of the lens body  3  to be replaced. Depending on what is required from the optical and mechanical properties, the distal part  11  can also be biconvex, i.e. its proximal surface can be bent towards the front or towards the back or be planar. 
     After the distal lens part  11  has been positioned, the proximal lens part  10  is injected into the lens capsule  2  though an injection apparatus  13  in the form of a filling material in a flowable state and the lens capsule is filled in its state accommodated to infinity. In this step, such an amount of filling material is injected that the volume of the lens implant corresponds substantially to the one of the previously removed lens body. 
     The lens capsule  2  is, thereafter, closed and the proximal lens part  10  is cured to the desired rigidity, which can be achieved e.g. by a chemically, electrically or optically induced cross-linking. Suitable filling materials and techniques are known to the person skilled in the art e.g. from U.S. Pat. No. 4,608,050 or WO 89/00029. 
     A cross-linked polysiloxane, a hydrogel or a collagen-preparation can, e.g. be used because regarding it has a consistency similar to the lens body. 
     Arranging of the pre-fabricated lens part  11  at the distal side of the lens has the advantage that it forms a relatively stable rear wall for the lens. If a clouding occurs after the implanting at the distal area of the lens capsule  2 , the lens capsule  2  can be removed in such this area by means of laser rays. The lens part  11  shields also without lens capsule  2  the possibly still flowable, physiologically less compatible first lens part  10  from the vitreous body of the eye and all other structures of the interior of the eye. Because opening of the rear capsule by a laser is never uniform, the softer material of the first lens part would otherwise leak out at the back because the capsule is subjected to pressure. This would destroy the optical function of the lens. Lens part  11  prevents such a leakage. 
     However, in particular if a more stable, physiologically well compatible material is used for the first lens part  10 , the second lens part  11  can e.g. also be located in the center or in a proximal portion of the lens implant. 
     A second embodiment of the invention is illustrated in  FIG. 4 . Here the distal part  11  consists of a bag  11   a  which is filled by a transparent filling material  11   b . This structure has the advantage of producing a relatively large distal part  11   a ,  11   b  without making a large hole in the lens capsule  2 . After removing the lens body  3 , the bag  11   a  is first inserted in an empty, rolled state into the lens capsule  2 . Thereafter an injection needle is inserted through the same opening. By means of the needle the filling material  11   b  is fed into the bag  11   a . Finally, the proximal part  10  is filled in. 
     The bag  11   a  is cut and pre-shaped in such a manner that it attains the desired shape in the filled state. In the kit mentioned above at least a part of the pre-shaped lens parts, in particular the larger ones thereof, may be provided as bags  11   a.    
     Subject of the present invention is a lens implant and a kit for the production of such lens implants. The invention relates, however, also to the above described, intraoccular method of production, in which the filling material for the first part  10  of the lens is introduced in a flowable state and a suitable lens part  11  is introduced in a solid state into the lens capsule  2 . Preferably, the rigidity of the first lens part  10  is thereafter increased by a curing. During this, the capsule  2  should be accommodated to infinity. 
     Whereas in the present application preferred embodiments of the invention are described, it shall be clearly understood that the invention is not limited thereto but can be also embodied otherwise within the scope of the following claims.