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ACCOMMODATING INTRAOCULAR LENS
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. In particular, lenses of the present invention com- 10 prise at least one optic and are capable of being inserted into the natural lens capsule through relatively small incisions in the eye.
2. Description of the Prior Art
Cataracts occur when the crystalline lens of the eye 15 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 20 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. 25 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 30 area of the eye posterior to the iris, known as the posterior chamber. This is the area where the patient'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 displace- 35 ment of vitreous humor and retina detachment encountered in anterior chamber intraocular lenses are less likely to occur. Lenses implanted in the posterior chamber are described in U.S. Pat. Nos. 3,718,870, 3,866,249, 3,913,148, 3,925,825, 4,014,552, 4,053,953, and 4,285,072. None of 40 these lenses have focusing capability.
Lenses capable of focusing offered the wearer the closest possible substitute to the natural crystalline lens. U.S. Pat. No. 4,409,691 to Levy is asserted to provide a focusable intraocular lens positioned within the capsule. This lens is 45 located in the posterior area of the capsule and is biased toward the fovea or rear of the eye. The '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, 50 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 55 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' haptics are loaded inward when accommodating for near vision. Since accommodation for near vision is the normal 60 status of the capsule, the Levy lens' 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 65 optic and two plate haptics which extend radially outward from diametrically opposite sides of the optic and are
moveable 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 body. This will eventually lead to pressure necrosis of the ciliary body.
Finally, International Patent Publication WO 01/60286 by Humanoptics AG discloses a two-piece accommodation lens which comprises an optical section positioned within a ring-shaped envelope which is designed to be lodged in the equatorial zone of the lens capsule. However, the envelope and the optical section are not unitarily constructed. The non-unitary construction of the optical section and the envelope that are responsive to ciliary muscle contraction and retraction, results in increased wear and tear of the lens. Thus, the lens may not operate efficiently for a long period of time as is needed for implantation in humans.
There is a need for an intraocular lens implant capable of focusing in a manner similar to the natural lens. The lens should comprise a structure which inhibits the growth of fibrotic tissue and avoids damage to the ciliary body and other eye components. Furthermore, the optic positioning element should preferably be of unitary construction.
SUMMARY OF THE INVENTION
The present invention fills this need by providing an accommodating intraocular lens for implantation substantially within the confines of the capsule of a human eye intermediate the anterior and posterior capsule walls which is safe for long-term use and readily insertable into the eye capsule.
In more detail, the lens of the invention comprises at least one optic presenting opposed anterior and posterior surfaces, coupled with a resilient optic positioning element to cooperatively present a shape that generally conforms to the shape of the capsule. The optic positioning element comprises an anterior section configured for yieldable engagement with the anterior capsule wall, a posterior section configured for yieldable engagement with the posterior capsule wall, a bight, in cross section, joining said anterior and posterior sections, and a haptic arm extending between said optic and said optic positioning element. Another preferred embodiment of the lens of the invention may further comprise a posterior optic also presenting opposed anterior and posterior surfaces coupled to the optic positioning element. Thus, this embodiment comprises an anterior optic and a posterior optic coupled to the optic positioning element in order to accommodate in response to ciliary body movement.
The haptic arm may extend between an optic, preferably the anterior optic if the lens of the invention includes a second posterior optic, as mentioned above, and any one of the three sections which cooperatively make up the optic positioning element. That is, the haptic arm may extend between an optic and the bight, an optic and the anterior section, or an optic and the posterior section.
Preferably, the optic positioning element comprises a plurality of individually continuous, circumferentially spaced apart segments which include anterior and posterior sections and corresponding bights extending therebetween. In preferred embodiments, the individual anterior and posterior sections may be joined by a continuous section presenting an annular orifice therein. The positioning element further comprises at least one and preferably a plurality of haptic arms extending between an optic and the circumferentially spaced apart segments.
The anterior optic for use with the inventive lens preferably presents a convex anterior surface and optionally presents a plurality of circumferentially spaced apart openings therethrough. One of skill in the art should appreciate, however, that the both the anterior and posterior optics may 5 be constructed as either converging or diverging shapes. The optic positioning element is preferably formed of a yieldable synthetic resin material such as a material selected from the group consisting of silicones, acrylates, including polymethylmethacrylates, and mixtures thereof. Even more pref- 10 erably the optic positioning element is formed of a material having an elastic memory.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view showing placement, within the capsule of an eye, of a lens of the invention having a haptic arm extending between the posterior section of the optic positioning element and the optic, with the eye focused on an object distant from 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 near the viewer.
FIG. 3 is an anterior view of the lens shown in FIG. 1 in its original, non-compressed state.
FIG. 4 is a vertical cross-sectional view of the lens of FIG. 3 taken along line 4—4.
FIG. 5 is an anterior perspective view of the lens of FIG. 1 showing the lens in its original, non-compressed state.
FIG. 6 is a cross-sectional view of the lens of FIG. 5.
FIG. 7 is a vertical sectional view showing placement, within the capsule of an eye, of a lens of the invention having a haptic arm extending between the anterior section of the optic positioning element and the optic, with the eye focused on an object distant from the viewer.
FIG. 8 is a vertical sectional view showing the location of the lens of FIG. 7 within the capsule of the eye, focused on an object near the viewer.
FIG. 9 is an anterior view of the lens shown in FIG. 7 in its original, non-compressed state.
FIG. 10 is a vertical cross-sectional view of a lens similar to the lens of FIG. 9 taken along line 10—10, but illustrating a posterior optic coupled to the posterior section of the optic positioning element.
FIG. 11 is an anterior perspective view of the lens of FIG. 7 showing the lens in its original, non-compressed state.
FIG. 12 is a cross-sectional view of the lens of FIG. 11.
FIG. 13 is a vertical sectional view showing placement, within the capsule of an eye, of a lens of the invention having a haptic arm extending between the bight of the optic positioning element and the optic, with the eye focused on an object distant from the viewer.
FIG. 14 is a vertical sectional view showing the location of the lens of FIG. 13 within the capsule of the eye, focused on a object near the viewer.
FIG. 15 is an anterior view of the lens shown in FIG. 13 in its original, non-compressed state.
FIG. 16 is a vertical cross-sectional view of a lens similar to the lens of FIG. 15 taken along line 16—16, but illustrating a posterior optic coupled to the posterior section of the optic positioning element.
FIG. 17 is an anterior perspective view of the lens of FIG. 13 showing the lens in its original, non-compressed state,
FIG. 18 is a cross-sectional view of the lens of FIG. 17.
DETAILED DESCRIPTION OF THE
FIGS. 1 and 2 show the various components of the human eye pertinent to this invention. Briefly, the eye 20 includes a frontal portion 22 covered by a cornea 24 which encloses and forms an anterior chamber 26. The anterior chamber 26 contains aqueous fluid and is bounded at the rear by an iris 28. The iris 28 opens and closes to admit appropriate quantities of light into the interior portions of the eye 20. The eye 20 includes a capsule 30 which ordinarily contains the natural crystalline lens. When the eye 20 focuses, the capsule 30 changes shape to appropriately distribute the light admitted through the cornea 24 and the iris 28 to a retina (not shown) at the rearward portion of the eye 20.
The retina is composed of rods and cones which act as light receptors. The retina includes a fovea which is a rodless portion that provides for acute vision. The outside of the rearward or posterior portion 32 of the eye 20 is known as the sclera which joins into and forms a portion of the covering for the optic nerve. Images received by the retina are transmitted through the optic nerve to the brain. The area between the retina and the capsule 30 is occupied by vitreous fluid. The eye 20 further includes a ciliary muscle or body 34 having zonular fibers 36 (also referred to as zonules) which support the capsule 30. The zonular fibers 36 include a layer of elastin tissue 38 which is located substantially about the equatorial portion 40 of the capsule 30.
Ocular adjustments for sharp focusing of objects viewed at different distances is accomplished by the action of the ciliary body 34 on the capsule 30 and the natural crystalline lens (not shown) through the zonular fibers 36. Contraction of the ciliary body 34 compresses the capsule 30 about its equatorial portion 40 causing it to take on a more spherical shape (shown in FIG. 2) for viewing objects that are nearer the viewer. Equatorial portion 40 is located on either side of equatorial axis 41. When the ciliary body 34 retracts and pulls on the zonular fibers 36 to cause the capsule 30 to take on a more discoid shape (shown in FIG. 1), objects at a distance can be viewed in proper focus.
Referring now to FIGS. 1-6, a preferred intraocular lens 42 is shown comprising an optic 44 and a flexible, resilient optic positioning element 46 comprising a plurality of individually continuous, circumferentially spaced apart segments 47 which include anterior and posterior sections 48, 50 which are configured for yieldable engagement with the anterior and posterior capsule walls 52, 54, respectively. When lens 42 is viewed in cross-section, bights 56 join sections 48 and 50. (See FIG. 4) Haptic arms 58 extend between posterior sections 50 and the optic 44, and join the optic 44 and element 46 thereby forming a readily implantable lens.
As will be apparent from the discussion of further preferred embodiments of the invention below, the embodiment of FIGS. 1-6 is noticeably different in that the anterior and posterior sections 48, 50 are not continuously connected to each other. The anterior and posterior sections 48, 50 are distinct from each other and are individually joined by a plurality of bights 56, as shown in FIG. 4. In this particular embodiment, it is important that the posterior sections 50 not be fixed in position with respect to the posterior capsule wall 54, and this would not be the case if the posterior sections 50 were continuously connected. While not shown in the figures, the anterior sections 48 may be continuously connected.
It will be appreciated from a study of FIGS. 1-6 that the lens 42 is constructed such that the optic 44 thereof is