INTRAOCULAR LENS WITH MULTIPLE-FULCRUM HAPTIC

Abstract: An intraocular lens (10) for implantation within an eye after cataract surgery. The intraocular lens has a haptic (16) having an elongated gently curving seating portion (16b) having a free end (16c) and a weakened (F2) portion about which such seating portion pivots. The weakened portion (F2,X,Y,Z) is spaced from the fulcrum (F1) formed at the location at which the haptic (16) is anchored to the lens body (12) such that the free end (16c) of the seating portion (16b) moves toward the lens body in response to compression of the seating portion toward the lens body for facilitating seating thereof, while minimizing the risk of injury to the delicate membranes in the eye by outwardly extending distal portions of the haptics. The construction of the lens being such that except for the weakened portion of the haptic, the entire haptic, including the seating portion, would pivot about the point of connection of the haptic to the lens body with the result that the free end portion would move away from, or at least not toward, the lens body, in response to such compression of the seating portion.

Description: BACKGROUND OF THE INVENTION In opthalmic surgery, following removal of the natural lens of the eye, an intraocular lens is implanted to take the place of the lens removed. Lenses designed to be placed in the posterior chamber may be implanted in either the ciliary sulcus or the capsular bag of the eye. Various types of such lenses have been proposed are use in use. For example, U.S. Patent No. 4,159,546 discloses an intraocular lens supported by a plurality of flexible strands secured to the lens body. Another lens design is the so called "Simcoe Posterior Chamber Lens" sold by Cilco Inc. as their "S2" posterior chamber lens. The latter has long strands which gently curve from the point of connection to the free ends thereof. Although great advances have been made over the years in intraocular lenses, the prior art designs are not without their problems. The Simcoe style of prior art lenses (see Fig. 1) have very long, gently curving, loops which exert gentle pressure and are easily compressible, but, because of the length of the loops, the free ends thereof tend to move outwardly, i.e., away from the lens body, in response to compression. This type of lens, therefore, requires substantial intraocular manipulation to move it from the anterior chamber into position in the posterior chamber, so as to avoid injury to the delicate tissue in the eye, by the outwardly extending free ends of the haptics. Each support strand of such prior art structure generally pivots about the point at which such support strand is anchored to the lens body, i.e., typically a point "P" on, or close to, the periphery of the lens body. Thus, generally radial pressure on the elongated seating portion of the support strand, such as is typically applied for manipulating the lens through the pupil and seating it in the posterior chamber, causes the free ends of the strands to move away from, or at least not toward, the lens body. Consequently, increased intraocular manipulation is required to move the lens, having these outwardly extending free ends of the haptics, into the posterior chamber without damaging the delicate membranes within the eye and it is particularly difficult to safely manipulate these outwardly extending free ends into the capsular bag. U.S. Patent 4,624,670, issued to Bechert on November 25, 1986, discloses an intraocular lens having a pair of loops which extend from opposite sides of the lens body. Each of the loops includes a notch disposed generally mid-way along the curved seating portion of the loop in question. The notches are said to divide the seating portions so as to simulate a four-point fixation in the eye and at the same time facilitate insertion by reducing the possibility of slippage of the inserting instrument. The Bechert lens is shown to have haptics which pivot generally about their point of connection to the lens body, in response to compression of the haptic preparatory to seating thereof. The free ends of the haptics of Bechert, therefore, will move outwardly rather than inwardly with respect to the lens body in response to such compression. If an effort is made to move the outwardly extending free ends of the haptics of such the prior art lenses toward the lens body, there is likely a substantial tendency for the lens body to rotate due to the location of the fulcrum, i.e., at the point of connection between the haptic and the lens body. Increased manipulation within the eye is therefore likely to be necessary in order to avoid such rotational movement of the lens body. Such added manipulation, of course, in addition to requiring substantial skill and being time consuming, increases also the risk of injury to the eye. US-4568347 discloses an intraocular lens for use as an artificial lens in the posterior chamber of an eye, comprising a light-focusing lens body; first and second position-fixation means individually joined to said lens body at respective first and second locations and each extending outwardly from said lens body for seating in respective interior portions of the posterior chamber of an eye, said juncture at each of said first and second locations forming a first fulcrum about which the corresponding position-fixation means can pivot with respect to said lens body; in which at least one of said position-fixation means comprises a lens support strand having a first portion extending outwardly from the first fulcrum, a second portion forming an elongated outwardly convex seating portion and having a free end portion, and a third portion intermediate said first and second portions and spaced from the first fulcrum to form a second fulcrum about which the second portion may pivot with respect to the first portion. The present invention provides an intraocular lens suitable for use as an artificial lens in the posterior chamber of an eye, which comprises: (a) a light-focusing lens body; (b) first and second position-fixation means individually joined to the lens body at respective first and second locations and each extending outwardly from the lens body for seating in respective interior portions of the posterior chamber of an eye, the juncture at each of the first and second locations forming a first fulcrum (F1) about which the corresponding position-fixation means can pivot with respect to the lens body; at least one of the position-fixation means comprising a lens support strand having a first portion extending outwardly from the first fulcrum, a second portion forming an elongated outwardly convex seating portion and having a free end portion, and a third portion between the first and second portions which is weakened and spaced from the first fulcrum to form a second fulcrum (F2) about which the second portion can pivot with respect to the first portion; in which (i) at least a portion of the lens body falls between two parallel lines each of which is drawn perpendicular to the diameter of the lens body which passes through the first fulcrum, and touches but does not cross the lens support strand unless at the first fulcrum, the distance (d) between the two lines being greater than the diameter of the lens body; (ii) the length and shape of the support strand are such that, in response to compression of the strand to pivot the second portion about its first fulcrum and substantially not around its second fulcrum, the free end portion of the strand does not move significantly towards the lens body; and (iii) the location of the second fulcrum and the relative stiffnesses of the first and second fulcra are such that, in response to compression towards the centre of the lens body of a central region of the second portion, the free end portion moves in a direction toward the lens body by virtue of pivotal movement of the second portion substantially only about the second fulcrum and not substantially about the first fulcrum, at least until substantial movement of the free end portion toward the lens body has occurred. The arrangement is such that the seating portion will, in response to generally radial compression thereof by the surgeon, pivot first about the weakened second fulcrum and only finally (if additional compressive forces are exerted) about the first fulcrum. The pivoting of the haptics about such second fulcrum avoids outward movement of the free ends of the haptics during the initial compression of the haptics. This offers the advantage of allowing the surgeon to more readily position the lens without the lens body rotating about its axis and without the substantial risk of injury to the delicate tissue within the eye by outwardly extending distal portions of the haptics thus making such positioning and seating much simpler and safer. DESCRIPTION OF DRAWINGS For the purpose of illustrating the invention, there are shown in the drawings the forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. Fig. 1 shows a prior art lens having elongated, gently curving strands, with the inferior strand shown in solid line, in uncompressed condition, and in dashed line in partly compressed condition; Fig. 2A is a front elevation of a lens in accordance with one preferred embodiment of the present invention; Fig. 2B is a side elevation of the lens shown in Fig. 2A; Fig. 3 shows the lens of Fig. 2A with the inferior strand shown in uncompressed condition in full line and in partly compressed condition in dashed lines; Fig. 4 shows another embodiment of a lens in accordance with the present invention, showing the superior strand in uncompressed condition, in solid line, and in partly compressed condition in dashed lines (the lens of Fig. 4 is identical to that of Fig. 2A except for the added suture 30); Fig. 5A is a transverse sectional view, according to one preferred embodiment of the present invention, taken along the line A-A of Fig. 4, in the direction of the arrows; and Fig. 5B is a transverse sectional view taken along the line B-B of Fig. 4, in the direction of the arrows. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, there is shown in Fig. 1 a intraocular lens 10′ according to the prior art, having a lens body 12′ and a pair of strands 14′ and 16′, which strands support the lens body when it has been implanted. Once implanted, the lens body is supported and held in place by a plurality of support strands. Two of such strands, 14′ and 16′ are used, each one being attached or secured adjacent to the peripheral lens body edge and on opposite sides thereof. The strands are flexible, that is they yield under pressure, and also have a memory retaining feature whereby the strand will return to its normal, extended, position or will automatically tend to do so once the pressure has been released. Thus, the strands have a spring-like quality. The strands are attached to the lens body by adhesive or other mechanical means adjacent to the periphery of the lens body so as to have minimum interference with the lens body intself. As seen in Fig. 1, each of the strands 14′ and 16′ has a first, or connecting, portion 14a′, 16a′ adjacent to the point of connection P′ of the respective strand with the lens body and a gently curved or arced seating portion 14b′, 16b′, terminating in a free end 14c′, 16c′. The curved seating portions 14b′, 16b′ have a very long gently curving shape, the curvature of which broadly matches the respective arc of contact within the ciliary sulcus or within the capsular bag for distributing pressure evenly over a large surface area to avoid single-point pressure. The arced, i.e., gently curving, portions present a rounded strand surface abutting the ciliary body or capsule when the lens is implanted in the posterior chamber. Further, distal ends 14c′ 16c′ of the strands are located radially outwardly of the lens body 12′ at a radius R1′ from the point of connection P′ of the strand with the lens body. Flexure of the strands, by the surgeon prior to and during implantation, will be a generally radial compression of portions 14b′, 16b′ resulting in pivoting of the entire strand 14′, 16′ about its anchor point, or fulcrum, P′, from the undeformed position shown in solid line to and beyond the partly deformed condition shown in dashed line in Fig. 1. The imaginary arc "C" drawn from P′ as its center, generally represents the path along which distal end 16c′ of the haptic 16′ of the prior art lens in Fig. 1, moves in response to compression of the seating portion 16b′ of such prior art lens. It will be seen that such movement is not toward the lens body 12′. Thus, unsecured end 16c′ of the strand 16′ will move to a position generally indicated at O′, which is laterally substantially spaced from the lens body. Consequently, the free end 16c′ is in a position in which it is readily pointed toward, and thus jabbed against, the delicate tissue within the eye during implantation and in fact makes implantation more difficult since it extends far beyond the periphery of the lens body and thus increases the effective size of the lens which has to be moved through the pupil and into the capsular bag. Figs. 2A and 2B illustrate one preferred form of the lens of the invention, generally indicated by numeral 10, with supporting strand 16 being illustrated in Fig. 3 in solid lines in its natural, undeformed, state and in dashed lines in a position as it might be forced under pressure. It will be observed that, unlike support strands of prior art lenses, the free end 16c of support strands according to the present invention will move toward the lens body, in response to compression of the seating portion radially toward the center of the lens body. A preferred shape of the lens body 12 is illustrated in Fig. 2B in which the anterior lens body surface 30 is convex while the posterior surface 28 is flat or planar. The lens body peripheral edge 26 is shown to be circular, which is the preferred shape although any other desirable lens body surface and edge shape may be used and those shown are by way of illustration only. According to one preferred embodiment of the invention, seen in Fig. 2A, the strands 14 and 16 are each formed with an inwardly crimped portion, for example, forming a generally V-shaped notch X, Y, Z in the strand. Such notch, preferably faces inwardly with respect to the convex outer contour of the strand and forms a weakened portion exhibiting a fulcrum F2 at the apex "Y" thereof. The notch is preferably formed in the strand at a location intermediate the connecting portion 16a (P-X) and the gently curving seating portion 16b (Z-O). Consequently, seating portion Z-O of the strand, including the free end "O" thereof, will, in response to generally radial compressive pressure applied thereto near the mid-point of the seating portion, pivot about the fulcrum F2, of weakened portion X,Y,Z, well before any pivoting action takes place about the fulcrum F1 defined by connecting point P. Such pivoting action will result in the free end O traversing a path generally shown by an arc "q" drawn with a radius R2 having its center at fulcrum F2 defined by point "Y". Preferably, the strand portion forming the notch X,Y,Z will be of a different cross-sectional shape than the remaining portions of the strand for providing a relatively weakened portion for facilitating flexure of the seating portion Z-O about the fulcrum F2 well before any flexure about fulcrum F-1 takes place. Preferably such cross-sectional shape of the weakened portion at Y will be ribbon-like, or at least elliptical (Fig. 5A) as compared to a preferably round cross-sectional shape (Fig. 5B) for the remaining portions of the strand. A preferred strand material to achieve the desired results and used in a preferred lens according to the present invention, comprises polypropylene. One preferred strand composition is a proprietary polypropylene known by the trade mark "Prolene". The lens body 12 may be of any suitable material, preferably a plastic such as a composition which comprises polymethyl methacrylate. As seen in Fig. 3, the free ends 14c, 16c of the strands 14 and 16 of a lens according to a preferred embodiment of the present invention, move closer to the lens body under compression. This enables the lens according to the invention to be more readily and safely inserted through the pupil of an eye and positioned in the capsular bag. Upon strand 16 moving to its compressed state (dashed line in Fig. 3) ists lateral dimension, it will be seen, does not extend beyond the diameter of the lens body 12 by as substantial a distance as the prior art lens. As noted above, this feature allows the surgeon much greater flexibility in positioning and in seating the lens. According to another preferred embodiment of the invention illustrated in Fig. 4, the haptics 14, 16 having a weakened region in the form of a V-shaped notch X, Y, Z, of the type described above, have a loose, string-like flexible connecting member 30 bridging the gap formed by the V-shaped notch. The member 30 may be a thread of material such as the material typically used for suturing the eye and may be tied, or otherwise connected to the haptic at points X and Z respectively. The material of the suture 30 is preferably generally inextensible and of such length that the thread 30 will be fully extended (as shown by dashed lines in Fig. 4) upon such compression of the superior haptic as results in pivoting seating portion 14b about fulcrum "Y" to move distal end 14c substantially toward the lens body 12 (to a position such as seen in dashed lines in Fig. 4). Once the suture 30 is fully extended, as seen in dashed lines in Fig. 4, the haptic portions 14a and 14b acts as a cohesive unit and any further radial compression of the haptic results in the haptic pivoting about point P as a fulcrum. At such time, the distal end 14c is, however, sufficiently close to the lens body (see distance "D" in Fig. 4) so as not to exhibit the disadvantageous results exhibited by the prior art lenses (see distance D′ in Fig. 1).

Claims: An intraocular lens suitable for use as an artificial lens in the posterior chamber of an eye, which comprises: (a) a light-focusing lens body (12); (b) first and second position-fixation means (14, 16) individually joined to the lens body at respective first and second locations and each extending outwardly from the lens body for seating in respective interior portions of the posterior chamber of an eye, the juncture at each of the first and second locations forming a first fulcrum (F1) about which the corresponding position-fixation means can pivot with respect to the lens body; at least one of the position-fixation means comprising a lens support strand (16) having a first portion (16a) extending outwardly from the first fulcrum, a second portion (16b) forming an elongated outwardly convex seating portion and having a free end portion (16c), and a third portion (XYZ) between the first and second portions which is weakened and spaced from the first fulcrum to form a second fulcrum (F2) about which the second portion can pivot with respect to the first portion; in which (i) at least a portion of the lens body falls between two parallel lines each of which is drawn perpendicular to the diameter of the lens body which passes through the first fulcrum (F1), and touches but does not cross the lens support strand unless at the first fulcrum, the distance (d) between the two lines being greater than the diameter of the lens body; (ii) the length and shape of the support strand are such that, in response to compression of the strand to pivot the second portion about its first fulcrum and substantially not around its second fulcrum, the free end portion of the strand does not move significantly towards the lens body; and (iii) the location of the second fulcrum and the relative stiffnesses of the first and second fulcra are such that, in response to compression towards the centre of the lens body of a central region of the second portion, the free end portion moves in a direction toward the lens body by virtue of pivotal movement of the second portion substantially only about the second fulcrum and not substantially about the first fulcrum, at least until substantial movement of the free end portion toward the lens body has occurred. An intraocular lens as claimed in claim 1, in which said lens body (12) has a generally circular periphery and said second portion (16b) of said support strand is outwardly spaced from and generally parallel in shape to the adjacent portion of said periphery. An intraocular lens as claimed in claim 1 or claim 2, in which said second portion (16b) of said support strand has a gentle elongated curvature and the straight line distance (R1) between said first fuclrum (F1) of said support strand and said free end portion exceeds, in uncompressed condition of said position fixation means, the diameter of said lens body. An intraocular lens as claimed in any one of claims 1 to 3, in which the arcuate length of said second portion (16b) exceeds substantially the arcuate length of the portion of the periphery of said lens body which is parallel and adjacent thereto. An intraocular lens as claimed in any one of claims 1 to 4 in which a pair of radii drawn from the optical axis of said lens body to said first fulcrum (F1 ) and said free end portion (16c), respectively, subtend an angle of at least 90 degrees. An intraocular lens as claimed in any one of claims 1 to 5, in which said third portion comprises a pair of strand sections (X-Y, Y-Z) forming a notch extending generally transverse to the adjacent respective first and second portions of the strand. An intraocular lens as claimed in claim 6 which includes string means (30) connecting said first and second portions (16a, 16b) of said position fixation means at opposite sides of said third portion (XYZ) for bridging said third portion, said string means being of such a length as to be loose when said position fixation means is in uncompressed condition and to become taut in response to substantial pivoting of said second portion about said second fulcrum (F2). An intraocular lens as claimed in claim 7, in which said pair of strand sections (X-Y, Y-Z) are joined to each other at first ends thereof to form said second fulcrum (F2) and are joined at second ends thereof to said first and second portions (16a, 16b) of said one position fixation means respectively, and in which the string means (30) connects said second ends of said first and section portions. An intraocular lens as claimed in any one of claims 1 to 8, in which the first and second portions (16a, 16b) of the lens support strand have a generally circular cross-sectional shape, and the third portion (16c) has a flattened transverse cross-sectional shape, the direction of elongation of which is substantially parallel to the optical axis of the lens body so as to weaken the second fulcrum (F2) relative to the first fulcrum (F1). An intraocular lens as claimed in any one of claims 1 to 9, in which the other of said position fixation means is substantially the same shape and construction as said one position fixation means. An intraocular lens according to any one of claims 1 to 10, in which said position fixation means are strands of polypropylene. An intraocular lens as claimed in any one of claims 1 to 11, preceding claims in which the length and shape of said support strand is such that, in uncompressed condition thereof said free end portion (16c) is located on an arc of an imaginary first circle having its centre at the corresponding said first fulcrum (F1) and having a radius (R1) of such length that no part of said first circle intersects said lens body, and said free end portion (16c) is located also on an arc of an imaginary second circle having its centre at said second fulcrum (F2) and having a radius (R2) such that said imaginary second circle intersects said lens body along a path generally defined by an arc of said second circle when said second portion pivots about said second fulcrum.

Inventors: kELMAN, CHARLES D.
Applicants: kELMAN, CHARLES D.
Application year: 1988
Main classification: A61F2
IPC codes: A61F2