Accommodating intraocular lens implant

An improved intraocular lens (42) is provided which more closely mimics the accommodation and focusing of the eye's natural lens. The lens (42) comprises an optic (44) and a flexible, resilient optic positioning element (46) which includes an anterior section (48), a posterior section (50), a bight (56), in cross-section, joining the anterior and posterior sections, and a haptic arm (58) extending between the optic (44) and the optic positioning element (46). The lens (42) may optionally include a posterior optic (44a) coupled to the optic positioning element (46). The optic positioning element (46) is formed of unitary construction. The anterior (48) and posterior (50) sections are configured for yieldable engagement with the anterior (52) and posterior (54) walls of the eye capsule (30), respectively.

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 comprise 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 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'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 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 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 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, 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' haptics are loaded inward when accommodating for near vision. Since accommodation for near vision is the normal 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 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 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 preferably the optic positioning element is formed of a material having an elastic memory.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2show the various components of the human eye pertinent to this invention. Briefly, the eye20includes a frontal portion22covered by a cornea24which encloses and forms an anterior chamber26. The anterior chamber26contains aqueous fluid and is bounded at the rear by an iris28. The iris28opens and closes to admit appropriate quantities of light into the interior portions of the eye20. The eye20includes a capsule30which ordinarily contains the natural crystalline lens. When the eye20focuses, the capsule30changes shape to appropriately distribute the light admitted through the cornea24and the iris28to a retina (not shown) at the rearward portion of the eye20.

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 portion32of the eye20is 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 capsule30is occupied by vitreous fluid. The eye20further includes a ciliary muscle or body34having zonular fibers36(also referred to as zonules) which support the capsule30. The zonular fibers36include a layer of elastin tissue38which is located substantially about the equatorial portion40of the capsule30.

Ocular adjustments for sharp focusing of objects viewed at different distances is accomplished by the action of the ciliary body34on the capsule30and the natural crystalline lens (not shown) through the zonular fibers36. Contraction of the ciliary body34compresses the capsule30about its equatorial portion40causing it to take on a more spherical shape (shown inFIG. 2) for viewing objects that are nearer the viewer. Equatorial portion40is located on either side of equatorial axis41. When the ciliary body34retracts and pulls on the zonular fibers36to cause the capsule30to take on a more discoid shape (shown inFIG. 1), objects at a distance can be viewed in proper focus.

Referring now toFIGS. 1–6, a preferred intraocular lens42is shown comprising an optic44and a flexible, resilient optic positioning element46comprising a plurality of individually continuous, circumferentially spaced apart segments47which include anterior and posterior sections48,50which are configured for yieldable engagement with the anterior and posterior capsule walls52,54, respectively. When lens42is viewed in cross-section, bights56join sections48and50. (SeeFIG. 4) Haptic arms58extend between posterior sections50and the optic44, and join the optic44and element46thereby forming a readily implantable lens.

As will be apparent from the discussion of further preferred embodiments of the invention below, the embodiment ofFIGS. 1–6is noticeably different in that the anterior and posterior sections48,50are not continuously connected to each other. The anterior and posterior sections48,50are distinct from each other and are individually joined by a plurality of bights56, as shown inFIG. 4. In this particular embodiment, it is important that the posterior sections50not be fixed in position with respect to the posterior capsule wall54, and this would not be the case if the posterior sections50were continuously connected. While not shown in the figures, the anterior sections48may be continuously connected.

It will be appreciated from a study ofFIGS. 1–6that the lens42is constructed such that the optic44thereof is disposed posteriorly relative to at least a portion of the anterior sections48of element46, and within the confines of the positioning element46. Moreover, the anterior sections48present edges or free ends48a, and the haptic arms58orient the entire optic44in a posterior, offset relationship relative to at least a portion of the free ends48a. The edges or free ends48aalso define a central opening oriented about the optical axis of the optic44, the latter having anterior and posterior directions.

FIGS. 1 and 2demonstrate accommodation of lens42by the eye20. As shown inFIG. 1, the ciliary body34is in a retracted state, thereby stretching the zonular fibers36causing the capsule30to take on a more discoid configuration. The anterior section, posterior section, and bights48,50, and56, respectively, conform to the shape of the capsule30thereby causing the optic44to move posteriorly away from the cornea24and allowing the eye20to focus on objects distant from the viewer. Even more specifically, bights56closely conform to the equatorial portion40of capsule30.

As shown inFIG. 2, when the ciliary body34contracts, the zonular fibers36compress capsule30causing it to take on a more spherical configuration. The anterior section and bights48,56remain engaged with the capsule30, however, the posterior sections50shift position relative to the capsule30and may disengage the capsule posterior wall54. The compression of capsule30, and consequently lens42, causes the optic44to vault anteriorly toward the cornea24thus enabling the eye20to focus on objects near the viewer.

Another preferred intraocular lens according to the invention is depicted inFIGS. 7–12. Similar to the lens42described above, this lens42acomprises an optic44and an optic positioning element46including a plurality of circumferentially spaced apart segments47which include anterior and posterior sections48a,50a. When viewed in cross-section, bights56join sections48aand50a. A haptic arm58aextends between optic44and anterior section48a. The haptic arm58aextends posteriorly from the anterior section48ato the optic44. In a further preferred embodiment of the lens42a, as shown inFIGS. 7–12, the optic44may be operably joined to the optic positioning element46via a plurality of haptic arms (not shown). The plurality of haptic arms are disposed at various locations about anterior section48aand extend posteriorly towards the optic44. Lens42ais noticeably different from lens42, illustrated inFIGS. 1–6, in that the plurality of anterior and posterior sections48a,50aare continuously attached to each other through continuous sections51presenting annular orifices53therethrough.

As previously noted, lens42amay further comprise a posterior optic44a.FIG. 10illustrates the lens ofFIGS. 7–9but with a posterior optic44acoupled to the posterior section50aof the optic positioning element46. The posterior optic44ais illustrated as presenting a concave anterior surface and an opposing planar posterior surface (hereinafter plano-convave). Although the posterior optic44ais illustrated as plano-concave, any optic shape may be utilized in the manufacture of the intraocular lens of this invention, whether diverging or converging. Examples of converging optic shapes include plano-convex, biconvex, and convex meniscus. Examples of diverging optic shapes include plano-concave, biconcave, and concave meniscus. A concave meniscus optic is a diverging optic having a concave anterior surface wherein the concave surface has a lesser radius of curvature than the opposing convex posterior surface.

FIGS. 7 and 8demonstrate accommodation of lens42aby the eye20. As shown inFIG. 7, when the ciliary body34is in the retracted state, the zonular fibers36are stretched thereby causing the capsule30to take on a more discoid shape. The anterior section, posterior section, and bights48a,50a, and56, respectively, closely conform to the contours of the capsule30. When in the retracted state, the optic44moves posteriorly away from the cornea24thereby allowing the eye20to focus on objects distant from the viewer.

As shown inFIG. 8, when the ciliary body34contracts, the zonular fibers36compress capsule30causing the capsule30to take on a more spherical configuration. The capsule30simultaneously compresses element46causing lens42ato acquire a more spherical shape. The anterior section, posterior section, and bights48a,50a, and56, respectively, remain engaged with capsule30. The compression of element46causes the anterior section48ato move anteriorly toward the cornea24thereby causing the optic44to shift anteriorly allowing the eye20to focus on objects near the viewer.

FIGS. 13–18depict yet another preferred lens42b according to the invention. As with the lens42a, shown inFIGS. 7–12, this lens42balso comprises an optic44and an optic positioning element46including a plurality of circumferentially spaced apart segments47having continuous anterior and posterior sections48b,50b, and a bight56, when viewed in cross-section, joining together the anterior and posterior sections48b,50b. In essence, the lens42bis configured in much the same fashion as the lens42aofFIGS. 7–12with the exception that a plurality of haptic arms58bextend from the bight56toward the optic44. As shown inFIG. 16, when the lens42bis in its original, non-compressed state, the haptic arms58bare vaulted slightly toward anterior section48b.

As with lens42a, lens42bis also illustrated as further comprising a posterior optic44acoupled to the posterior section50bof the optic positioning element46. As noted in connection with the discussion ofFIG. 10above, the posterior optic44amay be constructed as either a diverging or converging optic shape.

FIGS. 13 and 14demonstrate accommodation of lens42bby the eye20. As shown inFIG. 13, when the ciliary body34is in the retracted state, the zonular fibers36are stretched thereby causing the capsule30to take on a more discoid shape. The anterior section, posterior section, and bight48b,50band56, respectively, conform to the contours of the capsule30. When in the retracted state, the optic44moves posteriorly away from the cornea24thereby allowing the eye20to focus on objects distant from the viewer.

As shown inFIG. 14, when the ciliary body34contracts, the zonular fibers36compress the capsule30causing it and lens42bto take on a more spherical configuration. The anterior section, posterior section, and bight48b,50b, and56, respectively, remain engaged with the capsule30. The compression of element46causes the optic44to vault anteriorly toward the cornea24allowing the eye20to focus on objects near the viewer.

Preferred optics44according to the invention may present convex anterior surfaces60and may be configured with a plurality of circumferentially spaced openings62to allow passage of fluid within the capsule30through the optic44. Preferably, the optic44is formed of an acrylic, silicone, similar synthetic resin material, or mixtures thereof.

The optic positioning element46is preferably formed of any appropriate biologically inert material conventionally used in intraocular lens construction (e.g., elastic, synthetic resin materials). Examples of suitable lens materials include acrylates (such as polymethylmethacrylates), silicones, and mixtures thereof. It is contemplated that mixtures of silicones and acrylates comprise both chemical mixtures, such as silicone-acrylate blends, and various combinations of silicones and acrylates employed to construct the lens. 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).

Preferably the inventive lens42will have an outer equatorial diameter (distance taken along equatorial axis41, between outer surfaces of opposing bights56) of from about 8.5–11 mm, and more preferably about 9.5 mm. Preferably the lens42will have a distance between outer surfaces of opposing anterior and posterior sections48,50(taken along optical axis43) of from about 2–4 mm, and more preferably about 3 mm.

The intraocular lens42,42a,42bof the invention substitutes both locationally and functionally for the original, natural, crystalline lens. Using the lens ofFIG. 1as an example, in order to insert the lens42into the capsule30, an ophthalmic surgeon would remove the natural lens (and thus the cataracts) by conventional methods, leaving an opening64in the anterior wall of the capsule30. Lens42is then folded into a compact size for insertion in the capsule30through opening64. Once inserted, the capsule30is filled with fluids (e.g., saline solution) which enter the lens42, causing the lens42to return to its original, non-deformed state as shown inFIG. 1. There is no need to suture the lens42to the capsule30because, due to the size and shape of the lens42and conformance of the lens to the capsule walls22,32,40, the lens42will not rotate or shift within the capsule30.

Implantation of the intraocular lens42,42a,42brestores normal vision because, not only does the lens42replace the patient's occluded natural lens, but the normal responses of the ciliary body34cooperate with the zonular fibers36and elastin tissue38during focusing of the lens42. The lens42thus follows the eye's natural physiology for focusing to provide a substitute means of optical accommodation. Furthermore, while the foregoing description discloses that the lens42could be utilized in cataract patients, the lens42may 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).

Optionally, the lens42,42a,42bmay be provided with a very thin membrane (not shown) in covering relationship as disclosed in U.S. patent application Ser. No. 09/940,018, filed Aug. 27, 2001, which is incorporated by reference herein. It is contemplated that the membrane would be formed of the same synthetic resin as the optic positioning element46, but would be much thinner (on the order of a few thousandths of an inch) than the remainder of the element46. The purpose of the membrane is to prevent or at least impede the passage of migratory cells through openings within the lens42and into the inner chamber of the lens42.

One of ordinary skill in the art will appreciate that the lens42,42a,42bof the present invention may either be formed entirely of unitary construction, or have an optic44and an optic positioning element46that are constructed separately and interconnected. In either case, the optic positioning element46is preferably formed of unitary, integral construction. In any event, each of the embodiments of the lens of the invention comprise an optic60which is offset posteriorly in relation to the anterior capsule wall when connected to the optic positioning element56. One of skill in the art will readily appreciate the optic60may be posteriorly offset through various haptic arms58,58a,58b. Thus, in each of these embodiments, the various haptic arms58,58a,58band optic44,60are preferably disposed entirely within the confines of the optic positioning element46. Offsetting the optic60in this manner eliminates the risk of damaging the iris28thereby causing cataracts by preventing contact between the optic60and the iris28during accommodation. The optic60will cause damage to the iris28when the optic60is not offset posteriorly as described herein. One skilled in the art will readily appreciate the lens42,42a,42bmay be positioned within the eye10, such that the anterior optic44faces the retina and the posterior optic44afaces the cornea24. When the lens is positioned in this manner, the posterior optic44ashould also be offset to eliminate damage to the iris28.