Abstract:
An intraocular lens ( 38 ) having focusing capabilities permitting focusing movement of the lens ( 38 ) in response to normal ciliary muscle movement incident to changes in the distance between the eye and an object under observation is provided. The lens ( 38 ) is designed for surgical implantation within the capsule ( 22 ) of an eye ( 10 ) and includes an optic ( 40 ) and a resilient body ( 46 ) which cooperate to form a discoid shaped lens ( 38 ) that generally conforms to the shape of the natural capsule ( 22 ). When distant objects are viewed, the ciliary body ( 32 ) is retracted and the capsule ( 22 ) flattens, thus causing the lens ( 38 ) to likewise flatten, moving the optic ( 40 ) posteriorly, closer to the fovea ( 26 ). When viewing near objects, the ciliary body ( 32 ) contracts, causing the capsule ( 22 ) and thus the lens ( 38 ) to expand to their original shape, shifting the optic ( 40 ) anteriorly, away from the fovea ( 26 ). The inventive lens ( 38 ) is preferably a unitarily formed, seamless body preferably comprising a flexible material which has elastic memory. Suitable materials comprise acrylates and silicone blends.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/393,514, filed Sep. 10, 1999, incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to accommodating intraocular lenses which can be surgically implanted as a replacement for the natural crystalline lens in the eyes of cataract patients. 
     2. Description of the Prior Art 
     Cataracts occur when the crystalline lens of the eye becomes opaque. The cataracts may be in both eyes and, being a progressive condition, may cause fading vision and eventual blindness. Cataracts were once surgically removed along with the anterior wall of the capsule of the eye. The patient then wore eyeglasses or contact lenses which restored vision but did not permit accommodation and gave only limited depth perception. 
     The first implant of a replacement lens within the eye occurred in 1949 and attempted to locate the replacement lens in the posterior chamber of the eye behind the iris. Problems such as dislocation after implantation forced abandonment of this approach, and for some period thereafter intraocular lenses were implanted in the anterior chamber of the eye. 
     Others returned to the practice of inserting the lens in the area of the eye posterior to the iris, known as the posterior chamber. This is the area where the patient&#39;s natural crystalline lens is located. When the intraocular lens is located in this natural location, substantially normal vision may be restored to the patient and the problems of forward displacement of vitreous humor and retina detachment encountered in anterior chamber intraocular lenses are less likely to occur. Lenses implanted in the posterior chamber are disclosed in U.S. Pat. Nos. 3,718,870, 3,866,249, 3,913,148, 3,925,825, 4,014,049,4,041,552, 4,053,953, and 4,285,072. None of these lenses have focusing capability. 
     Lenses capable of focusing offered the wearer the closest possible substitute to the crystalline lens. U.S. Pat. No. 4,254,509 to Tennant discloses a lens which moves in an anterior direction upon contraction of the ciliary body and which is located anterior to the iris. Though providing focusing capabilities, it presents the same disadvantages as other anterior chamber lenses. U.S. Pat. No. 4,253,199 to Banko approaches the problem of providing a focusable lens differently, by providing a replacement lens of deformable material sutured to the ciliary body. This lens functions much as the original crystalline lens but risks bleeding from the sutures. 
     U.S. Pat. No. 4,409,691 to Levy is asserted to provide a focusable intraocular lens positioned within the capsule. This lens is located in the posterior area of the capsule and is biased toward the fovea or rear of the eye. The &#39;691 lens is deficient because it requires the ciliary muscle to exert force through the zonules on the capsule in order to compress the haptics inward and drive the optic forward for near vision. However, the ciliary muscles do not exert any force during contraction because the zonules, being flexible filaments, exert only tension, not compression on the capsule. The natural elasticity of the lens causes the capsule to become more spherical upon contraction of the ciliary muscle. Thus, there is no inward force exerted on the capsule to compress the haptics of the Levy lens, and therefore accommodate for near vision. Even if such force were somehow available, the Levy lens&#39; haptics are loaded inward when accommodating for near vision. Since accommodation for near vision is the normal status of the capsule, the Levy lens&#39; haptics are loaded, reducing the fatigue life of the springlike haptics. 
     U.S. Pat. No. 5,674,282 to Cumming is directed towards an accommodating intraocular lens for implanting within the capsule of an eye. The Cumming lens comprises a central optic and two plate haptics which extend radially outward from diametrically opposite sides of the optic and are movable anteriorly and posteriorly relative to the optic. However, the Cumming lens suffers from the same shortcomings as the Levy lens in that the haptics are biased anteriorly by pressure from the ciliary bodies. This will eventually lead to pressure necrosis of the ciliary body. 
     Finally, U.S. Pat. No. 4,842,601 to Smith discloses an accommodating intraocular lens having anterior and posterior members which urge against the anterior and posterior walls of the natural lens capsule. The muscular action exerted on the natural capsule will thus cause the lens to flatten, thereby changing the focus thereof. The Smith lens is formed of first and second plastic lens members connected to one another adjacent their peripheral edges so as to provide a cavity therebetween. The connection between the lens members is accomplished by way of a U-shaped flange on the first member which forms an inwardly facing groove for receiving an outwardly extended flange on the second member. The Smith lens is lacking in that the first and second members must be separately inserted into the capsule and assembled within the capsule which is extremely difficult for even highly skilled surgeons to accomplish. 
     There is a need for an intraocular lens implant capable of focusing in a manner similar to the natural lens. This lens implant should be readily insertable into the capsule and should last for a substantial number of years without damaging any of the eye components. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The present invention fills this need by providing an intraocular lens with focusing capabilities which is safe for long-term use in an eye. 
     In more detail, the lens of the invention comprises an optic presenting a convex anterior surface and a resilient optic positioning element or body coupled to the optic to cooperatively present a discoid shaped lens that generally conforms to the shape of the natural eye capsule. The optic positioning element presents a posterior face that engages the posterior wall of the natural capsule, and an anterior face that engages the anterior wall of the natural capsule. The anterior and posterior faces of the optic positioning element are joined together by a bight. 
     As a result of the size and shape of the inventive lens, the focusing action of the natural lens is simulated. That is, the ciliary body of the eye (which remain connected to the capsule) continues to exert a muscular force radially outward from the center of the capsule through the zonular fibers so as to flatten the capsule. Because the posterior and anterior walls of the capsule are engaging the anterior and posterior faces of the optic positioning element, the inventive lens flattens in a manner similar to the natural capsule. This flattening alters the distance between the optic of the inventive lens and the fovea of the eye, thus allowing distant objects to be viewed. 
     The optic and optic positioning element can be formed of any biologically inert material conventionally used in intraocular lens construction, (e.g., yieldable synthetic resin materials). Examples of suitable lens materials include acrylates (such as polymethylmethacrylates), silicons, and mixtures of acrylates and silicons. It is particularly preferred that lenses according to the invention be constructed of a material having an elastic memory (i.e., the material should be capable of substantially recovering its original size and shape after a deforming force has been removed). An example of a preferred material having elastic memory is MEMORYLENS (available from Mentor Ophthalmics in California). 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a vertical sectional view showing placement of the lens of the invention within the capsule of an eye, with the eye focused on an object near the viewer; 
     FIG. 2 is a vertical sectional view showing the location of the lens of FIG. 1 within the capsule of the eye, focused on an object distant from the viewer; 
     FIG. 3 is a front view of an inventive lens shown in its original resting, non-flattened state; 
     FIG. 4 is a side elevational view of the lens of FIG. 3; 
     FIG. 5 is a front view of a prior art accommodating lens having a pair of haptics on the optic; 
     FIG. 6 is a front view of an alternate embodiment of the inventive lens shown in its original resting, non-flattened state; 
     FIG. 7 is a cross-sectional view of the lens of FIG. 6 taken along line  7 — 7 ; 
     FIG. 8 is a front view of an alternate embodiment of the inventive lens shown in its original resting, non-flattened state; 
     FIG. 9 is a cross-sectional view of the lens of FIG. 8 taken along line  9 — 9 ; 
     FIG. 10 is a front view of yet another alternate embodiment of the inventive lens shown in its original resting, non-flattened state; 
     FIG. 11 is a cross-sectional view of the lens of FIG. 10 taken along line  11 — 11 ; 
     FIG. 12 is a front view of an alternate embodiment of the inventive lens shown in its original resting, non-flattened state; and 
     FIG. 13 is a cross-sectional view of the lens of FIG. 12 taken along line  13 — 13 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, the present invention is in the form of an intraocular lens for surgical replacement of the human lens in the treatment of cataracts in the human eye. FIG. 1 shows the various components of the human eye pertinent to this invention. Briefly, the eye  10  includes a frontal portion  12  and a rearward portion  14 . The frontal portion  12  of the eye  10  is covered by a cornea  16  which encloses and forms an anterior chamber  18 . The anterior chamber  18  contains aqueous fluid and is bounded at the rear by an iris  20 . The iris  20  opens and closes to admit appropriate quantities of light into the inner portions of the eye  10 . The eye  10  includes a capsule  22  which ordinarily contains the natural crystalline lens. When the eye  10  focuses, the capsule  22  changes shape to appropriately distribute the light admitted through the cornea  16  and the iris  20  to a retina  24  at the rearward portion  14  of the eye  10 . 
     The retina  24  is composed of rods and cones which act as light receptors. The retina  24  includes a fovea  26  which is a rodless portion that provides for acute vision. The outside of the rearward or posterior portion  14  of the eye  10  is known as the sclera  28  which joins into and forms a portion of the covering for the optic nerve (designated by numeral  30 ). Images received by the retina  24  are transmitted through the optic nerve  30  to the brain. The area between the retina  24  and the capsule  22  is occupied by vitreous fluid. Finally, the eye  10  includes a ciliary muscle or body  32  having zonular fibers  34  (also referred to as zonules) which are attached to the capsule  22 . 
     Ocular adjustments for sharp focusing of objects viewed at different distances is accomplished by the action of the ciliary body  32  on the capsule  22  and crystalline lens (which would be located at numeral  36  in the natural, unmodified eye) through the zonular fibers  34 . The ciliary body  32  contracts, allowing the capsule  22  to return to a more spherical shape for viewing objects that are nearer the viewer. When the ciliary body  32  retracts and pulls on the zonular fibers  34  to make the capsule  22  more discoid, objects at a distance can be viewed in proper focus. 
     Referring to FIGS. 1-4, the inventive lens is an accommodating lens  38  which includes a central optic  40 . The optic  40  comprises an anterior surface  42  and a posterior surface  44 . The anterior surface  42  and the posterior surface  44  are usually convex, although the shape of these surfaces and size of the optic  40  can be varied depending upon the user&#39;s eyesight. The lens  38  further includes a resilient body  46 . Resilient body  46  comprises an outer wall  48  which extends radially from optic  40 . Resilient body  46  is preferably integral and essentially flush with optic  40  at optic perimeter  50  where wall  48  joins optic  40 . Wall  48  then curves to form a bight  51 , and converges on the posterior side  53  of lens  38 . Wall  48  forms a chamber  52  and terminates at location  54  to form an opening  56  which communicates with the chamber  52  allowing fluids to enter and fill the chamber  52 . 
     The overall shape of lens  38  in its original resting, non-deformed shape generally conforms to the shape of capsule  22  when capsule  22  is focused to view an object near the viewer (FIG.  1 ). Outer wall  48  of the resilient body  46  cooperates with optic  40  to form a lens having an overall discoid or saucer-like shape as best shown in FIGS. 3-4. The lens  38  is of sufficient size so that optic  40  mildly urges against the anterior wall  58  of the capsule  22 , while the posterior side  53  of lens  38  urges against the posterior wall  60  of the capsule  22 . 
     Intraocular lens  38  substitutes both locationally and functionally for the original, natural, crystalline lens (which would normally be at location  36 ). To insert the lens  38  into the capsule  22 , an ophthalmic surgeon would remove the natural lens (and thus the cataracts) by conventional methods, leaving an opening  62  in the anterior wall  58  of the capsule  22 . Lens  38  is then folded into a compact size for insertion into the capsule  22  through the opening  62 . Once inserted, the capsule  22  is filled with fluids (e.g., saline solution) which enter the chamber  52  of the lens  38 , causing the lens  38  to return to its original, non-deformed state as shown in FIG.  1 . There is no need to suture the lens to the capsule  22  because, due to the size and shape of the lens  38  as described above, the lens  38  will not rotate or shift within the capsule  22 . 
     Implantation of the inventive lens  38  restores normal vision because, not only does the lens  38  replace the patients occluded natural lens, but the normal responses of the ciliary body  32  cooperate with the lens  38  during focusing. In FIG. 1, the focal length between the posterior surface  44  of optic  40  and the fovea  26  is greater to permit viewing of nearby objects. The focal length is greater because the ciliary muscle or body  32  has contracted, making the capsule  22  more spheroid, permitting the lens  38  to be maintained in its resting state and positioning the optic  40  towards the anterior wall  58 . The lens  38  of the present construction thus follows the eye&#39;s natural physiology for focusing to provide a substitute means of optical accommodation. When the object of observation becomes more distant, the sensory cells within the retina  24  signal the ciliary body  32  to relax, thus pulling on the zonular fibers  34  to make the capsule more discoid as shown in FIG.  2 . In so doing, the horizontal depth of the capsule  22  is narrowed, which in turn causes the horizontal depth of the lens  38  to narrow in a similar manner. This narrowing causes the optic  40  to move posteriorly as the capsule  22  and the lens  38  become more discoid. The focal length between the posterior surface  44  of optic  40  and the fovea  26  is thus shortened, and the object remains in focus. If the object under observation reapproaches the eye, the ciliary body  32  again contracts, lessening the tension on the zonular fibers  34 . When this occurs, the lens  38  returns to its resting, non-deformed shape (as shown in FIGS.  1  and  4 ), thus moving the optic  40  anteriorly. The focal length between the posterior surface  44  of the optic  40  and the fovea  26  is thus increased (see FIG.  1 ), and the object remains in focus. 
     In view of the foregoing discussion, it will be appreciated that the inventive lens  38  is designed so as to provide a substantially uniform distribution of pressure along the walls of the capsule  22 . This was often not the case in prior art intraocular lenses. For example, FIG. 5 depicts one prior art lens  64  comprising an optic  66  and haptics  68   a,b . The lens  64  is designed for placement within the natural capsule, with the haptics  68   a,b  providing a means for biasing the optic  66  anteriorly during focusing. However, due to the design of the lens  64 , the haptics  68   a,b  apply pressure along concentrated portions of the capsule, thus causing wear on the capsule. This problem is avoided with the lens of the invention. 
     FIGS. 6-13 depict alternate embodiments of the invention, with like numbering representing like parts. FIGS. 6 and 7 depict a lens  70  having a plurality of small, circular openings  72   a-d  formed at the optic perimeter  50 . Openings  72   a-d  serve a number of purposes. First, openings  72   a-d  provide an avenue by which antibiotics can be injected into the lens chamber  52 . Furthermore, the positioning of these openings  72   a-d  as depicted is such that the openings  72   a-d  overlap with the opening  62  (depicted in FIG. 1) of the capsule so as to allow drainage of fluid from capsule  52  as well as continuous replenishment of fluids in lens chamber  52 . Finally, openings  72   a-d  can be used to assist in positioning the lens  70  within the capsule. 
     Although FIGS. 6 and 7 depict openings  72   a-d  along perimeter  50 , it will be appreciated that the location of these openings  72   a-d  can be altered. For example, one or more of these openings  72   a-d  can be located completely within the optic perimeter  50 , or completely outside the optic perimeter  50 , on the outer wall  48 . 
     FIGS. 8 and 9 depict yet another embodiment of the invention. In this embodiment, the lens  74  comprises longitudinal slots  76   a,b  which are formed within the outer wall  48  of the lens  74 . In the embodiment illustrated, the slots  76   a,b  have respective upper portions  78   a,b  which begin just beyond or outside the optic perimeter  50  (i.e., just beyond small segments  80   a,b  of outer wall  48 ). The slots  76   a,b  progress around bight  51  and across the lens equator or bisecting plane  82 , to lower slot portions  84   a,b . As shown in FIGS. 8 and 9, the slots  76   a,b  do not communicate with opening  56 . That is, segments  86   a,b  of wall  48  separate slots  76   a,b  from opening  56 . Although two slots  76   a,b  have been illustrated, it will be appreciated that, in some applications, three or four of these slots may be desired, depending upon the rigidity needed for the lens  74 . 
     FIGS. 10 and 11 also depict an alternate embodiment of the inventive lens. In this embodiment, lens  88  comprises curved openings  90   a,b  formed in wall  48  anterior to plane  82 . FIGS. 12 and 13 depict a further embodiment wherein lens  92  comprises openings  94   a,b  formed in wall  48  posterior to plane  82 . In each of lenses  88 ,  92 , the respective openings  90   a,b  and  94   a,b  are positioned opposite one another (i.e., their respective centers are about 180° apart) and are approximately the same size. However, it will be appreciated that the size, number of, and location of these openings can be altered as necessary depending upon, among otherthings, the strength or rigidity desired in the lens. 
     Although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, while the foregoing method of inserting the lens  38  into the capsule  22  presumed that a portion of the anterior wall  58  of the capsule  22  would be removed with the natural lens, it will be appreciated that it may be possible to insert the lens  38  through an incision in the anterior wall  58 . Furthermore, while the foregoing description discloses that the lens  38  could be utilized in cataract patients, the lens  38  may be used in any situation where the natural lens needs to be replaced (e.g., in a patient who wishes to eliminate the need for bifocals).