MULTI-PART INTRAOCULAR LENS

Abstract: A multi-part intraocular lens that can be surgically implanted within an eye through an incision having a length substantially less than the lens' diameter. The lens includes a plurality of lens segments (39, 41, 43) that are slidable between a retracted orientation, in which they cooperate to form a generally circular lens, and an extended orientation, in which they cooperate to form an elongated assembly having a transverse width substantially less than the lens' diameter. To surgically implant the lens, it is inserted through the eye incision in the extended orientation, whereupon further insertion causes the lens segments to slide to their retracted orientation automatically without the need for a risky assembly of segments using surgical instruments within the eye.

Description: This invention relates generally to intraocular lenses, and, more particularly, to multi-part intraocular lenses that can be surgically implanted in an eye through an incision that is smaller than the diameter of the lens' optic. In the human eye, the crystalline lens is situated behind the pupil and iris and it functions to focus light entrant through the cornea and pupil onto the retina at the rear of the eye. The lens is a biconvex, highly transparent structure made of slender, curved rod-shaped ectodermal cells in concentric lamellae surrounded by a thin capsule. The lens capsule is supported at its periphery by suspensory ligaments, called zonules, that are continuous with the ciliary muscle. A cataract condition results when the material within the lens capsule becomes clouded, thereby obstructing the passage of light. To correct this condition, two forms of surgery are used. In intracapsular cataract extraction, the entire lens is removed intact. To accomplish this, the surgeon severs the zonules or suspensory ligaments about the entire periphery of the capsule, and removes the entire lens with the capsule and its content material intact. In extracapsular cataract extraction, an incision is made through the front wall (i.e., the anterior capsule) of the lens, and the clouded cellular material within the capsule is removed through this opening. Various techniques are used to accomplish this removal. The transparent rear capsule wall (i.e., the posterior capsule), as well as the zonules and peripheral portions of the anterior capsule (i.e., the anterior capsule flaps), all remain in place in the eye. Both intracapsular and extracapsular extraction eliminate the light blockage due to the cataract. However, the light now entrant through the cornea and pupil is unfocused since there is no longer a lens in the eye. Appropriate focusing can be achieved by a lens (i.e., a contact lens) exterior to the eye. This approach, though generally satisfactory, has the disadvantage that when the external contact lens is removed, the patient effectively has no useful sight. A preferred alternative is to implant an artificial, intraocular lens directly within the eye. The lens is implanted through an incision made near the periphery of the cornea. The length of the incision in the eye is an important factor in determining the rate of healing following lens implantation. A longer incision usually means longer post-operative recovery and healing periods for the patient. Other problems associated with lengthy incisions include expulsive hemorrhage, iris prolapse, bleb formation and high astigmatism. Accordingly, it is desirable to reduce the length of the incision as much as possible. There have been several efforts in the past to reduce incision length by specially configuring the intraocular lens. In one such effort, as disclosed in US-A-4451938, which forms the basis for the pre-characterising part of claim 1 herein, the lens includes separable elements that are inserted individually into the eye and then connected together using surgical tools. These separate lens elements may include portions of the lens body itself, as well as position-fixation haptics or loops projecting outwardly from the lens body to center the lens within the eye. Using this technique, it is possible for the incision length to be smaller than the final diameter of the lens body or optic. Although the individual insertion of separable lens elements permits use of a smaller incision, it necessarily requires the use of surgical tools within the eye, to assemble the elements together. This increases the risk of accidentally touching and irreparably injuring the eye's cornea, iris or capsule. In addition, the necessity of separately inserting and connecting together a number of lens elements within the eye complicates an already delicate positioning procedure. Another lens that can be implanted through an incision smaller than the final diameter of the lens body includes a central lens member and two side lens members hinged to opposite sides of the central member see e.g. EP-A-0 099 641. The side members pivot about axes in the plane of the central member. In use, the lens members are folded together for insertion into the eye through a relatively small incision and are then unfolded using a suitable tool, to produce a generally circular lens. The unfolding of the lens elements within the eye risks accidentally touching and irreparably injuring the eye's cornea, iris and capsule. Still another lens that can be implanted through an incision smaller than the final diameter of the lens body is constructed of a transparent material that is highly flexible, such as silicone. Such lenses are folded for insertion through a small incision, and then unfolded into their final shape within the eye. Again, the unfolding within the eye risks injury to the cornea, iris and capsule. In addition, it is preferred to use harder and less flexible lens materials such as polymethyl methacrylate, which have been used successfully for decades. It should therefore be appreciated that there has existed a definite need for an intraocular lens capable of being inserted into an eye through an incision having a length smaller than the lens' diameter, without increasing the risk of accidental eye injury and without requiring the use of highly flexible materials such as silicone. The present invention fulfils this need. According to the invention, there is provided an intraocular lens comprising a plurality of lens segments which are capable of being placed in predetermined positions relative to one another, in which the segments are fitted together to form an assembled optical lens and which segments are individually of a transverse width substantially less than that of said assembled optical lens, characterised in that said lens segments are interconnected, by lens guiding means, for sliding movement relative to one another, said lens guiding means being provided along the edges of the lens segments which are contiguous in the assembled optical lens, said lens guiding means including an elongate tongue on one of said segments extending along a said edge of said one of said segments and engaging in a mating elongate groove extending along the contiguous edge of the contiguous said segment. A multi-part intraocular lens embodying the invention thus has a plurality of lens segments that are slidably attached to each other in such a way that the lens can be inserted into an eye through an incision that is smaller than the final diameter of the lens body or optic. As the lens is inserted through the incision, its separate segments automatically slide together to form a substantially circular optical lens that can be properly centered within the eye. This lens configuration permits its surgical implantation through an incision of substantially reduced length, which shortens the healing process and obviates certain problems associated with lengthy incisions. In addition, because the separate lens segments slide together automatically during insertion, the lens configuration obviates the need for performing complex and dangerous manipulations of separate lens segments within the eye. To insert the lens, the plurality of lens segments are initially slid to the elongated, extended orientation. One end of the elongated assembly is then inserted through the incision until it engages a predetermined portion of the eye (e.g. the ciliary sulcus, capsule equator or anterior chamber angle), to inhibit further movement of that leading end. Further insertion causes the remaining lens segments to pass through the incision and slide relative to the preceding segments and thus move into the retracted orientation. The lens then may be centered in its final position within the eye using a plurality of position-fixation haptics or loops projecting outwardly from the lens segments. In one preferred form of the invention, the plurality of lens segments include a primary lens segment forming a central portion of the lens and first and second secondary lens segments located on opposite sides of the primary lens segment. A position-fixation loop is preferably attached to each of the secondary lens segments. Thus, the leading end of the lens, which is inserted first through the incision during surgical implantation, is defined by the loop attached to the first secondary lens segment. Movement into the eye of the leading end loop, and the first secondary lens element to which it is attached, is inhibited when the loop engages the predetermined portion of the eye's interior, e.g. the ciliary sulcus or capsular bag equator. Further insertion of the lens through the incision causes the primary lens segment and the second secondary lens segment to slide into the retracted orientation. The loop attached to the second secondary lens segment is the final portion of the lens to pass through the incision. The secondary lens segments may advantageously be of substantially equal size and be shaped substantially like lunar crescents. The primary lens segment thus is widest at its midpoint. This maximum width is preferably about one-half the lens' final diameter. The lens element are thus sized such that, when the lens is properly centered in the eye and when normal lighting conditions are present, the pupil of the eye transmits light through only the primary lens segment. This eliminates the occurrence of any optical distortion that might unexpectedly be caused by light passing through the lens guiding means carried on the contiguous edges of the lens segments. Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the invention. In such drawings: FIG. 1 is a side sectional view of an intraocular lens implanted in an eye; FIG. 2 is a plan view of a first intraocular lens embodiment of the invention, with dotted lines showing the lens in an extended orientation suitable for insertion into an eye and with solid lines showing the lens in a retracted orientation after insertion; FIG. 3 is a plan view of a second intraocular lens embodiment of the invention, with dotted lines showing the lens in its extended orientation and solid lines showing the lens in its retracted orientation; FIGS. 4-6 are plan views of the lens of FIG. 2 showing progressions in orientation of the lens segments as they are surgically inserted through an incision in an eye; and FIG. 7 is a cross-sectional diagram of a tongue and mating groove assembly for attaching together the various lens segments of the embodiments of FIGS. 2 and 3, while permitting the lens segments to slide relative to each other. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to the exemplary drawings, and particularly to FIG. 1, there is shown an intraocular lens 21 surgically implanted in the posterior chamber 23 of a human eye 25, behind the eye's iris 27 and pupil 29. The depicted lens has been implanted as a replacement for the eye's natural lens, which was extracted because of a cataract condition. In such an extraction, a small incision is made through the natural lens' front wall or anterior capsule and the clouded cellular material within the capsule is removed, for example, by suction. Remaining behind are the natural lens' rear wall or posterior capsule 31 as well as the peripheral portions or flaps 33 of the anterior capsule and zonules 35 for attaching the capsule to the eye's ciliary muscle 37. FIG. 2 is a plan view of a first embodiment of the intraocular lens 21 of the invention. The lens includes a primary or central lens segment 39 and two secondary or lateral lens segments 41 and 43 attached to opposite sides of the central segment. The central segment is shaped generally like the longitudinal cross-section of an American football, and the two lateral segments are shaped generally like lunar crescents. The three segments together form a circular lens having any desired optical power. As is conventional, the lens may be plano-convex, biconvex or convexo-concave. Resilient position-fixation haptics or loops project outwardly from the lens segments, for use in centering and retaining the lens in its desired position within the eye 25. In FIG. 2, two such loops 45 and 47 are shown projecting outwardly from the lateral lens segments 41 and 43, respectively. The implanted lens 21 is inserted through an incision (not shown) near the periphery of the eye's cornea 49. The pupil 29 is ordinarily dilated, to facilitate placement of the lens behind it, in the posterior chamber 23. Alternatively, the lens may be implanted in front of the pupil, in the anterior chamber 50. The corneal incision through which the lens 21 is inserted during implantation is preferably made as short as possible, to quicken its healing. Most prior lens configurations, however, prevent a reduction of the incision length to less than the diameter of the lens optic. In accordance with the present invention, the three lens segments 39, 41 and 43 are slidable relative to each other in such a way that the lens can be configured into an elongated orientation having a transverse width substantially less than the diameter of the lens optic (when in its circular orientation). The lens can thereby be surgically implanted through an incision of substantially reduced length. As the lens is inserted through the incision, its separate segments slide together automatically to form the generally circular lens, without ordinarily requiring the insertion into the eye of any surgical instruments for assembling the segments together. The use of such instruments might be required in some limited circumstances. The lens can thereby be implanted with minimal risk of injury to the eye. The three lens segments 39, 41 and 43 are preferably attached to each other by a tongue-and-groove mechanism that permits them to slide along their contiguous edges. In a retracted orientation (solid lines in FIG. 2), the lens segments cooperate to form a generally circular lens, while in an extended orientation (dotted lines in FIG. 2), the lens segments form an elongated shape having a transverse width substantially less than the final diameter of the lens optic. In the extended orientation, the position-fixation loops 45 and 47 project outwardly from the lens' two ends. FIGS. 4-6 are a sequence of views depicting the lens embodiment 21 of FIG. 2 as it is being surgically implanted into an eye through an incision depicted schematically at 51. In FIG. 4 the three lens segments 39, 41 and 43 have been slid to the fully extended orientation and the position-fixation strand 45 and lateral lens segments 41 at one end of the elongated assembly have been inserted through the incision. In particular, the lens has been inserted to the point where the leading loop 45 contacts a predetermined portion of the eye's interior (e.g., the ciliary sulcus, the capsule equator, or the anterior chamber angle), which limits further inward movement of both the loop 45 and the lateral lens segment 41 to which it is attached. Continued insertion of the trailing lens segments 39 and 43 and trailing loop 47 cause the central segment 39 to slide relative to the leading segment 41, whose movement is being resisted. FIG. 5 depicts the lens configuration after the central segment has slid a substantial distance in this fashion. After the central lens segment 39 has slid to its fully retracted position relative to the leading lateral lens segment 41, continued insertion of the trailing lateral lens segment 43 and trailing loop 47 causes the latter segment to slide relative to the center segment. FIG. 6 depicts the lens configuration after this trailing segment 43 has slid a substantial distance in this fashion. Still further insertion causes the trailing segment 43 to slide to its fully retracted position, after which time the lens can be properly centered with the eye 25. This centering is ordinarily accomplished by placing the position-fixation loops 45 and 47 into the cleft or fornix of the lens capsule, the ciliary sulcus, or the anterior chamber angle. The resilience of the loops functions to align the lens with the center of the pupil 29. It will be appreciated that throughout the insertion procedure, the transverse width of the portion of the lens passing through the incision 51 is substantially less than the lens optic's final diameter. This permits use of an incision of substantially reduced length, which correspondingly reduces the time required for the wound to heal. In the embodiment of FIGS. 2 and 4-6, for example, the maximum transverse width of the lens during insertion through the incision is only about one-half the lens optic's final diameter. This permits the incision length to be reduced to about one-half its normal size. It will also be appreciated that the lens segments 39, 41 and 43 slide together into their final circular configuration automatically, usually without the need to insert any surgical tools within the eye 25 and without moving the lens segments out of a generally coplanar relationship. This significantly reduces the risk of accidentally injuring the eye, particularly the cornea 49, iris 27 and posterior capsule 31. As previously mentioned, the lens segments 39, 41 and 43 are slidably attached to each other by a tongue and mating groove mechanism. In particular, the center segment 39 includes elongated tongues 53 and 55 on its opposite edges, and the respective lateral segments 41 and 43 include mating grooves 57 and 59 on their inwardly-facing edges. Small beads 60a and 60b located at the remote ends of the lens segments 41 and 43, respectively, prevent the segments from sliding beyond their desired final positions. FIG. 7 is a cross-sectional view of the lens 21, depicting the conforming shapes of the tongue 53 and groove 57. It will be observed that the groove is undercut, to hold the lens segments 39 and 41 tightly together and prevent their separation. The tongue and mating groove are preferably configured to minimize the existence of any air gaps between them. Any such air gaps could cause undesired refraction of light passing through the lens. In addition, forming the separate lens segments of the same material, for example, polymethyl methacrylate, minimizes undesired refraction and reflection at the interfaces between the tongue and groove caused by differences in refractive indices. Forming the center lens segment 39 in the general shape of the longitudinal cross-section of an American football and the lateral lens segments 41 and 43 in the general shape of a lunar crescent provides the lens 21 with an important advantage. When the lens is properly implanted in its desired position within the eye 25, the pupil 29 is normally sized to transmit light only to the center lens segment 39. Only in very low-light conditions does the pupil size increase sufficiently to permit light to pass through the lateral lens segments 41 and 43 and thus the tongue and groove interfaces between the segments. Even then, only a small proportion of the light passes through the tongue and groove interfaces. This minimizes any undesired optical effects the interfaces might provide. An alternative embodiment of the intraocular lens of the present invention is depicted in FIG. 3. In this embodiment, the lens 21′ includes two half-circular lens segments 61 and 63 that together form a circular lens having any desired optical power. As with the lens embodiment of FIG. 2, the lens segments of this embodiment include a tongue 65 and mating groove 67 that permit the segments to slide between a retracted orientation, in which the lens is circular, and an extended orientation, in which the lens is elongated and has a transverse width substantially less than its circular diameter. Resilient haptics or loops 69 and 71 project outwardly from the respective lens segments 61 and 63, for use in centering the lens within the eye 25. The lens 21′ of FIG. 3 is surgically implanted in the eye in substantially the same fashion as the lens 21 of FIG. 2, as described above. Here, however, there is sliding between merely two lens segments rather than three. More particularly, the lens is first slid to its extended orientation (dotted lines in FIG. 3) and one end is then inserted through the eye incision. Insertion continues until the leading strand 69 contacts a predetermined portion of the eye's interior (e.g., the ciliary sulcus, capsule equator, or anterior chamber angle), which limits further inward movement. Continued inserted causes the trailing lens segment 63 to slide relative to the leading lens segment 61, until the lens has slid to its retracted orientation (solid lines in FIG. 3). The lens can then be properly centered within the eye by means of the resilient loops 69 and 71. Using this implantation procedure, the lens 21′ can be inserted through an incision substantially smaller than its final diameter and can be properly placed in its final circular orientation without ordinarily requiring the insertion of any special surgical instruments within the eye. It should be appreciated from the foregoing description that the present invention provides a multi-part intraocular lens that can be surgically implanted within an eye through an incision having a length substantially less than the lens' final diameter, without the need for a risky assembly of individual lens components within the eye. The lens includes a plurality of segments that are slidably attached to each other such that the lens can be slid to an elongated orientation for insertion into the eye. As the lens in inserted through a small incision into the eye, its separate segments slide together automatically to form the lens optic's final circular shape. Although the invention has been described in detail with reference to the presently preferred embodiments, those of ordinary skill in the art will appreciate that the various modifications can be made without departing from the invention. Accordingly, the invention is limited only by the following claims.

Claims: An intraocular lens comprising a plurality of lens segments (39, 41, 43) which are capable of being placed in predetermined positions relative to one another, in which the segments are fitted together to form an assembled optical lens and which segments are individually of a transverse width substantially less than that of said assembled optical lens, characterised in that said lens segments (39, 41, 43) are interconnected, by lens guiding means, (53, 57) for sliding movement relative to one another, said lens guiding means being provided along the edges of the lens segments which are contiguous in the assembled optical lens, said lens guiding means including an elongate tongue (53) on one of said segments extending along a said edge of said one of said segments and engaging in a mating elongate groove (57) extending along the contiguous edge of the contiguous said segment. An intraocular lens as recited in claim 1, wherein said lens guiding means includes means for preventing said plurality of lens segments from detaching from each other during normal use. An intraocular lens as recited in claim 1, wherein said groove (57) is undercut and said tongue (53) has a cross-sectional shape conforming to that of the groove, whereby the contiguous segments providing said groove and said tongue are held tightly together and prevented from separating. An intraocular lens as recited in claim 1, wherein said transverse width of said lens segments is about one-half the transverse width of said assembled lens. An intraocular lens as recited in claim 1, wherein said plurality of lens segments (39, 41, 43) include a primary lens segment (39) forming the central portion of said lens and first and second secondary lens segments (41, 43) located on opposite sides of said primary lens segment (39). An intraocular lens as recited in claim 5, wherein said first and second secondary lens segments (41, 43) are of substantially equal size and are shaped substantially like lunar crescents. An intraocular lens as recited in claim 6, wherein said plurality of lens segments (39, 41, 43) are sized and configured such that, when said plurality of lens segments are in the retracted orientation and said lens is properly centered within the eye and when normal lighting conditions are present, the pupil of the eye transmits light passing only through said primary lens segment (39). An intraocular lens as recited in claim 5 and further including first and second position-fixation haptics (45, 47) connected to said respective first and second secondary lens segments (41, 43) and adapted to center said lens within the eye. An intraocular lens as recited in claim 1, wherein said plurality of lens segments includes first and second lens segments (61, 63) of substantially equal size, each lens segment having a substantially semi-circular shape.

Inventors: HOFFER, KENNETH J.
Applicants: HOFFER, KENNETH J.
Application year: 1986
Main classification: A61F2
IPC codes: A61F2