Abstract:
An iris-supported intraocular lens having an optic portion and a plurality of fixation members coupled thereto. Each fixation member has a pair of pincer arms that separate outward of the optic and converge toward one another at aligned end tips. One or both of the end tips are covered with a soft sleeve or cap. The IOL is fixed in the anterior chamber of the eye by pinching the iris tissue between the end tips of each pair of pincer arms. The soft sleeves eliminate damage to the iris tissue.

Description:
This application is a continuation of application Ser. No. 09/943,558, filed Aug. 30, 2001 now U.S. Pat. No. 6,409,763. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of ophthalmics, more particularly to ophthalmic devices, and still more particularly to ophthalmic devices known as intraocular lenses (IOLs). 
     Intraocular lenses (IOLs) are commonly used to modify or enhance vision. IOLs can be placed at various positions or locations within the eye. For example, IOLs can be placed in the anterior chamber (AC) of the eye, that is, the region of the eye posterior of the cornea and anterior of the iris. The most common form of such an IOL includes a central lens and outer fixation members or haptics that resiliently contact the annular angle between the cornea and iris. 
     Although there are substantial advantages to placing the IOL in the anterior chamber of the eye, various complications with angle-supported lenses have been reported. Among other problems, angle-supported anterior chamber IOLs have been reported to cause irritation of the tissue in the angle, and decentration or offsetting displacement away from a preferred optical axis. 
     Consequently, there has been renewed interest in IOLs constructed for fixation to the iris (some of the earliest IOLs were iris fixated, anterior chamber IOLs), so-called “iris-supported” lenses. By fixing the optic supporting structure to the iris itself, contact with the sensitive filtration angle of the eye is avoided. 
     Iris fixated IOLs are disclosed in Worst, U.S. Pat. Nos. 4,215,440 and 5,192,319, and in Portney, U.S. Pat. No. 6,152,959. These patents disclose IOLs employing one or more optic fixation members formed having a pair of pincer arms which, acting together, pinch an anterior surface region of the iris. This pinching action detachably attaches the IOL to the iris so that the IOL optic is ideally fixated in the region of the iris opening (i.e., the pupil of the eye). In early designs, the tips of the pincer arms contacted each other, which potentially damaged or even necrosed the iris tissue. In later designs, such as in, Worst, U.S. Pat. No. 5,192,319, the tips of the pincer arms define a gap therebetween which reduces somewhat the tissue damage. However, there is a potential risk that tissue can be damaged by the sharp pincher arms which can puncture the iris tissue. 
     It would be advantageous to provide iris-supported anterior chamber IOLs which improve on the designs of the prior art. 
     SUMMARY OF THE INVENTION 
     New IOLs for implantation in eyes, in particular in anterior chambers of the eyes, have been discovered. The present IOLs are sized and structured to reduce the incidence of one or more known complications in the eye caused by prior iris-supported anterior chamber IOLs. 
     In one embodiment, the present invention provides an iris-supported intraocular lens for implantation in the anterior chamber of an eye, comprising an optic centered on an optical axis and at least two fixation members extending outward from the optic. Each fixation member defines a pair of separated pincer arms that converge toward one another and terminate at aligned end tips to form a gap therebetween. At least one compliant sleeve covers one of the pincer arm tips and fills the gap. There are desirably two sleeves provided for each fixation member, one sleeve covering each pincer arm end tip. Alternatively, there is only one sleeve provided covering one of the pincer arm end tips. 
     In a preferred embodiment, each fixation member defines a D-shape with a base region forming the upright of the D and the pincer arms forming the curved portion. Alternatively, each fixation member defines an O-shape with a base region adjacent the optic that is narrower than a separation distance between the pair of pincer arms. 
     The gap desirably has a dimension G of between about 0.004-0.020 inches (0.102-0.508 mm). The pincer arms are typically made of PMMA, and the sleeve is made of a material that has a durometer of less than about 80, desirably less than about 50 at normal eye temperatures (about 35° C., just under normal body temperature). For example, the sleeve is made of a material selected from the group consisting of silicone, hydrophobic acrylic, and hydrophylic acrylic. The sleeve desirably has abrupt corners at its distal tip to facilitate grasping of tissue. 
     In another embodiment, an iris-supported intraocular lens for implantation in the anterior chamber of an eye comprises an optic centered on an optical axis, and at least two fixation members extending outward from the optic. In the alternative embodiment each fixation member defines a pair of separated pincer arms of a first material having a first hardness that converge toward one another and terminate at aligned end tips form a gap therebetween, and an interface of a second material positioned within the gap that is more compliant than the first material of the pincer arms. In a preferred embodiment, the interface comprises a sleeve covering one of the pincer arm end tips and filling the gap, and there are desirably two sleeves provided for each fixation member, one sleeve covering each pincer arm end tip. The at least one of the sleeves desirably has an abrupt edge at its distal tip to facilitate grasping of tissue between the sleeves. 
     Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent. 
     These and other aspects and advantages of the present invention will become apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view of a first embodiment of an iris-supported intraocular lens of the present invention; 
     FIG. 2 is a plan view of the iris-supported intraocular lens of FIG. 1; 
     FIG. 2A is a detailed view taken within the circle  2 A in FIG. 2; 
     FIG. 2B is a detailed view as in FIG. 2A of an alternative sleeve structure; and 
     FIG. 3 is a plan view of an alternative iris-supported intraocular lens of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     There is shown in FIG. 1, in vertical cross section, a forward region  10  of a representative human eye having an optical axis  11  (Axis of symmetry), a cornea  12 , an iris  14  and an intact, natural crystalline lens  16 . A (posterior) corneal endothelium surface  18  is identified on cornea  12 . 
     An iris-supported or iris-fixated intraocular lens (IOL)  20 , according to a preferred embodiment of the present invention, is shown implanted in an anterior chamber  22  of eye region  10  (posterior to corneal endothelium surface  18 ) and fixated, in a manner described below, to an anterior surface  24  of iris  14 . 
     An annular pupiliary spincter region  28  of iris  14  surrounds and controls a pupil or pupiliary opening  30  having a diameter, D 1 , typically no greater than about 8 mm for normal vision. 
     Further identified are an annular iris collarette region  32  and an annular pupiliary dilator muscle region  34  of iris  14 . An annular chamber angle  36  is identified at a peripheral edge region of iris  14 , as is an annular trabecular meshwork  38 . An annular ciliary process  40  is indicated at the peripheral attachment of natural lens  16 . 
     As seen in FIG. 1, iris fixated IOL  20  is fixated to iris anterior surface  24  in the general region of iris collarette  32  (the thickest region of iris  14 ), radially outwardly from pupillary sphincter  28 . 
     With reference to FIGS. 2 and 2A in conjunction with FIG. 1, the IOL  20  includes an optic  50  which has respective anterior and posterior surfaces, and may be constructed as convex-convex (as depicted in FIG.  1 ), convex-concave, convex-planar, or concave-planar or concave-concave, all such and other configurations being within the scope of the present invention. Optic  50  may advantageously be provided in the diopter range between about −25 and about +30. It is preferred that optic  50  be constructed from an elastically deformable material, such as a silicone or acrylic material, enabling the optic to be folded, rolled or otherwise deformed so that IOL  20  can be implanted through an ocular incision no larger than about 4.0 mm or about 3.5 mm or about 3.0 mm. 
     The IOL  20  further includes at least two fixation members  52   a ,  52   b  that extend radially outward from the outer edge  54  of the optic  50 . Each of the fixation members  52   a ,  52   b  includes a base region  56  attached to the optic  50  and a pair of pincer arms  58   a ,  58   b  extending outward from the base region. As seen to the right side of FIG. 2, each pincer arm  58   a ,  58   b  includes a proximal segment  60  that projects generally radially outward from the base region  56 , and a distal segment  62  that extends from the outer end of the proximal segment in a generally circumferential direction with respect to the optical axis  11 . Each of the segments  60 ,  62  has a length that is substantially larger than its width or depth (into the page). 
     The fixation members  52   a ,  52   b  may be made of various materials typically used for such structures. For instance, a polymethylmethacrylate (PMMA), acrylic, or other such material is suitable. The fixation members  52   a ,  52   b  must have a minimum of stiffness to locate the optic  50  along the natural optical axis. 
     The distal segments  62  of the two pincer arms  58   a ,  58   b  converge toward one another and terminate at aligned end tips  64 , as seen best in the enlarged view of FIG.  2 A. The pair of pincer arms  58   a ,  58   b  on each fixation member  52   a ,  52   b  thus forms a “C” shape, with the distal segments  62  defining the upright of the “C.” The base region  56  is about as wide as the widest separation distance between the pincer arms  58   a ,  58   b  such that the entire fixation member  52  resembles a “D.” 
     The distal segments  62  do not meet in the middle, but instead are spaced apart by a gap G (FIG.  2 A). The gap G is desirable between about 0.004-0.020 inches (0.102-0.508 mm). 
     In contrast to the prior art iris-supported IOLs, the gap G is not empty but is instead filled with the material from one or more compliant caps or sleeves, such as the sleeves  70   a ,  70   b  seen in FIG. 2, over the tips  64  of the pincer arms  58   a ,  58   b . When there are two such sleeves  70   a ,  70   b  over both tips  64 , and they are identical, they meet along a mid-plane  72 . In a preferred embodiment, the wall thickness t of each sleeve  70   a ,  70   b  (at least between the tips  64 ) is about one-half of the gap G. As a consequence, the material of the sleeves  70   a ,  70   b  remains substantially uncompressed when the IOL is not in use. Alternatively, the wall thickness t of each sleeve  70   a ,  70   b  may be such that some compression of the material of the sleeves  70   a ,  70   b  occurs when the IOL is not in use. 
     FIG. 2B illustrates alternative sleeves  70   a′ ,  70   b′  over the tips  64  of the pincer arms  58   a ,  58   b . Instead of being rounded at their ends, the sleeves  70   a′ ,  70   b′  have right-angled or otherwise abrupt or sharp corners  74  at their ends, thus enhancing their ability to grasp iris tissue therebetween. The sharp corners are desirably continuous around the tip of each sleeve  70   a′ ,  70   b′ , although intermittent points or teeth may be used. 
     In use, the pincer arms  58   a ,  58   b  are used to clamp and grasp iris tissue on opposed sides of the IOL  20  to fixate the IOL within the anterior chamber, as seen schematically in FIG.  1 . The material of the sleeves  70   a ,  70   b  is desirably highly compliant so that tissue damage or necrosis is eliminated. For example, the sleeves  70   a ,  70   b  may be made of a silicone, a hydrophobic acrylic, a hydrophylic acrylic, or other such biocompatible material suitable for long-term implantation in the ocular environment. The softness or compliance of the material is typically measured by a durometer value at normal eye temperatures (about 35° C., just under normal body temperature), and is desirably between about 0 to about 80 and, more preferably between about 5 to about 50. Desirably, the shape of the facing tips of at least one of the sleeves  70   a ,  70   b  is such that the sleeves cooperate to grasp the iris tissue therebetween. 
     It will be understood by those of skill in the art that the material properties of the sleeves  70   a ,  70   b  and the gap G between the tips  64  factor into the amount of compression applied to the iris tissue, although the implant technique also plays a role. The IOL  20  is thus designed so that the surgeon can reliably implant it using the pincer arms  58   a ,  58   b  without undue compression and attendant tissue damage. 
     It should also be mentioned that the soft covering of the sleeves  70   a ,  70   b  over the tips  64  further reduces the instance of tissue damage because it covers over any sharp corners of the harder tips. Because of the ability of the soft material to deflect, the surgical technique to entrap tissue between the pincer arms is simplified and made more reliable. Furthermore, alternatives to the sleeve structure are contemplated, as long as the end tips of the pincer arms compress a material therebetween (other than the iris tissue) that is more compliant than the material of the end tips. For example, end plugs that are adhered or otherwise fastened to the tips of the pincer arms are contemplated. 
     FIG. 3 illustrates an alternative embodiment of an iris-supported IOL  80  having an optic  82  and a pair of oppositely-directed fixation members  84 . Each fixation member  84  differs from the fixation members  52  in FIG. 2 in that a base region  86  is narrower than the separation distance between a pair of pincer arms  88   a ,  88   b  extending outwardly therefrom. Each fixation member  84  thus forms an “O” shape. This shape facilitates folding of the IOL  80  (about a horizontal line through the center thereof). 
     As before, the tips of the pincer arms  88   a ,  88   b  are separated by a gap, with a compliant material filling the gap. Instead of a sleeve covering the tips of both pincer arms  88   a ,  88   b , only one such sleeve  90  is provided. In this manner, the pincer arms  88   a ,  88   b  compress tissue therebetween with the benefit of the compliance of the material of the sleeve  90 , though one of the pincer arms comes into direct contact with the tissue. 
     While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.