Abstract:
An intraocular lens configured to be implanted in the cornea from the posterior aspect. The lens has an optic and a pair fixation members extending outward therefrom. One of the fixation members includes a single enlarged foot, while the other fixation member has two bifurcated feet. The fixation members are sized and shaped to fix within tunnels formed in the cornea. A method of the invention includes forming tunnels in the stroma layer of the cornea, and positioning the fixation members in the tunnels. The tunnels may be formed from outside or inside the cornea. The method may include inserting the folded intraocular lens into the anterior chamber, permitting the lens to unfold, inserting the fixation member with the enlarged foot in one of the tunnels, and bending the two bifurcated feet of the other fixation member together so as to fit within the other tunnel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to intraocular lenses and, in particular, to an anterior chamber intraocular lens adapted to be fastened to the posterior aspect of the cornea.  
           [0002]    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.  
           [0003]    IOLs may generally be classed by material. Hard or rigid IOLs are distinguished from soft IOLs that may be folded to facilitate implantation through a small incision in the cornea or sclera.  
           [0004]    Although there are substantial advantages to placing the IOL in the anterior chamber of the eye, various complications have been reported as a result of the presence of IOLs in such anterior chambers. For example, anterior chamber IOLs have been reported to cause detrimental endothelial cell loss in the eye; pupil retraction or ovalling, which can be both cosmetically and functionally detrimental; pupillary block, which can cause glaucoma; and decentration or offsetting displacement of the IOL away from a preferred optical axis. Such complications are particularly troublesome when the anterior chamber IOL is structured to be fixated against the iridio/corneal angle, a very delicate region of the eye. One solution to this problem for acrylic lenses, which are foldable but relatively harder than silicone lenses, has been to provide enlarged feet or pods on the end of the fixation members or haptics. In this manner, a larger surface area contact reduces irritation to the iridio/corneal angle. It would be advantageous to provide anterior chamber IOLs which result in reduced incidences of one or more of these complications.  
           [0005]    IOLs advantageously have been foldable for insertion through small incisions in eyes, particularly for insertion in the capsular bags in the posterior chambers of the eyes. Anterior chamber IOLs have a tendency to move in a relatively uncontrolled manner after implantation in the eye. Such uncontrolled movement of an IOL in the anterior chamber can detrimentally affect the iris and/or the cornea. For example, the IOL touching the cornea can result in harmful endothelial cell loss.  
           [0006]    It would be advantageous to provide anterior chamber IOLs which have a reduced tendency to cause or do not cause one or more of: endothelial cell loss in the eye; pupil retraction or ovalling, which can be both cosmetically and functionally detrimental; pupillary block, which can cause glaucoma; and decentration or offsetting displacement of the IOL away from a preferred optical axis. Further, it would be advantageous to eliminate problems associated with IOL fixation against the delicate iridio/corneal angle.  
         SUMMARY OF THE INVENTION  
         [0007]    New IOLs for implantation in eyes, in particular in anterior chambers of the eyes, have been discovered.  
           [0008]    The present invention provides a method of implanting an intraocular lens in an eye having a cornea, an optical axis, and an anterior chamber. The method includes introducing the intraocular lens into the anterior chamber of the eye, and suspending the lens from the cornea. The intraocular lens may have at least one (and desirably two) fixation member(s) extending outward from an optic, where the method includes implanting the fixation member(s) in the cornea from the posterior aspect. Desirably, the fixation member is implanted in the stroma layer of the cornea for better support. An elongate tunnel in the cornea may be formed into which the fixation member inserts, the tunnel preferably being formed from the exterior of the eye. Where the intraocular lens has two fixation members, two incisions in the cornea are formed generally diametrically across the optical axis, and the method includes suspending the intraocular lens by positioning each of the two fixation members in a respective incision. One of the incisions may be used to introduce the intraocular lens, preferably in a deformed, e.g., folded, configuration, to the anterior chamber. A first incision may be formed from the exterior of the eye, and a second incision may be formed from the posterior aspect of the cornea.  
           [0009]    The present invention further includes a method of implanting an intraocular lens in an eye having a cornea defining an anterior aspect and a posterior aspect, an optical axis, and an anterior chamber. The method includes forming a least two incisions in the cornea open to the anterior chamber and suspending the intraocular lens in the anterior chamber from the incisions. The incisions may be disposed generally diametrically across the optical axis, whereby the method includes positioning each of two generally diametrically oppositely-directed fixation members of the intraocular lens in a respective incision. One of the incisions may be formed from the posterior aspect, or both of the incisions may be formed from the anterior aspect. Desirably, at least one of the incisions is sized to permit introduction of the intraocular lens in a deformed insertion configuration therethrough. At least one of the incisions may have a tunnel portion that extends within the stroma layer of the cornea, preferably for about 2 mm. Furthermore, the incision having the portion that extends within the stroma layer may have a stepped configuration, with a portion opening to the posterior aspect, and an optional portion opening to the anterior aspect.  
           [0010]    In a further embodiment, an intraocular lens, for example, an acrylic intraocular lens for corneal implantation in the anterior chamber of an eye is provided. The intraocular lens has an optic with an optical axis and an outer edge. A pair of fixation members extends outward from the optic outer edge. A first fixation member comprises an elongate, curved strut terminating in an enlarged foot, and a second fixation member comprises an elongate, curved strut bifurcated into two outer struts each terminating in a foot that is approximately the same thickness as the associated outer strut. Desirably, each of the feet is angled respect to the associated outer strut so that the feet point away from one another. The fixation members may be angled with respect to the optical axis in an anterior direction, preferably at an angle between about 15 and about 65 degrees.  
           [0011]    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.  
           [0012]    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  
       [0013]    [0013]FIG. 1 is a vertical sectional view through the anterior portion of an eye, illustrating the layers of the cornea;  
         [0014]    [0014]FIG. 1A is an enlarged sectional view through a portion of the cornea of FIG. 1 illustrating the various corneal layers;  
         [0015]    [0015]FIG. 2A is a frontal elevational view of an exemplary intraocular lens of the present invention;  
         [0016]    [0016]FIG. 2B is side elevational view of the intraocular lens of FIG. 2A;  
         [0017]    [0017]FIG. 3 is a schematic front elevational view of an eye showing the location of exemplary incisions in the cornea in a procedure for implanting an intraocular lens of the present invention;  
         [0018]    FIGS.  3 A- 3 B are sectional views of the exemplary cornea incisions taken along respective sectional lines of FIG. 3; and  
         [0019]    FIGS.  4 A- 4 B are front elevational and vertical sectional views of an eye showing the placement of an exemplary intraocular lens of present invention in the posterior aspect of the cornea. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Referring now to FIG. 1, the eye  12  comprises a cornea  14  shown to the left or front of the eye and an annular iris  16  shown in the middle of the eye. The iris  16  divides the eye  12  into an anterior chamber  18  at the front and a posterior chamber (not shown) in back of the iris. For purpose of orientation, the directions “anterior” and “posterior” are as commonly known, i.e., forward and rearward, respectively. The iris  16  also defines the aperture or pupil  22 , which is a variable opening in the middle of the iris. The posterior face of the cornea  14  and the anterior face of the iris  16  meet at the peripheral ciliary band defining an iridio-corneal angle  24 . Behind the iris  16  is the ciliary process  26 , which controls the movements of the natural crystalline lens  30  of the eye  12  via a plurality of fibrous zonules  32 . In the human eye, an optical axis OA is generally aligned along the centers of the cornea  14 , the natural lens  30  and the retina (not shown) of the eye  12 .  
         [0021]    With reference to FIG. 1A, the cornea  14  comprises five layers, including, from the outermost to the innermost, posterior layer, an outer layer  34  of epithelial cells, Bowman&#39;s membrane  36 , the stroma  38 , Descemet&#39;s membrane  40 , and the endothelium  42 .  
         [0022]    FIGS.  2 A- 2 B illustrate an exemplary intraocular lens  60  that can be positioned in the anterior chamber  18  of the eye  12  and implanted in the posterior aspect of the cornea  14 , as described below with respect to FIGS.  4 A- 4 B. The intraocular lens  60  includes a generally circular optic  62  defining an optical axis  63  at its center, a first fixation member  64  projecting generally in one direction from the optic, and a second fixation member  66  projecting generally in the opposite direction relative to the first fixation member. The fixation members  64 ,  66  are sometimes known as haptics or loops. The optical axis  63  is an imaginary line that passes through the optical centers of both faces of the intraocular lens  60 .  
         [0023]    As seen in FIG. 2B, the optic  62  includes a typically convex anterior face  68   a , and a typically concave posterior face  68   b . The fixation members  64 ,  66  are coplanar or angled forwardly away from the optic  62 , in the anterior direction. An angle θ is shown to indicate the degree of forward angle of each of the fixation members  64 ,  66 . The angle θ is desirably between about 10 or about 15 and about 65 degrees.  
         [0024]    The intraocular lens  60  may be made from a variety of materials, and the optic  62  may be the same as or a different material than the fixation members  64 ,  66 . For example, the optic  62  and/or fixation members  64 ,  66  may be made from hydrophobic or hydrophilic acrylic polymeric materials, silicone polymeric materials, collagen, collagen-containing composites, polymethyl methacrylate (PMMA) and the like and mixtures thereof. Desirably, the fixation members  64 ,  66  are relatively stiffer with respect to the deformable, e.g., foldable, optic  62 .  
         [0025]    With reference again to FIG. 3A, the first fixation member  64  includes an elongate, curved strut  70  that attaches to the optic  62  and terminates in a single, enlarged foot  72 . Using a clock-face nomenclature, with the optical axis  63  at the center, the curved strut  70  commences at a reinforced region  74  at about the 10:00 position on the outer edge of the optic  62 . The strut  70  extends in a clockwise direction a small distance  76  away from and conforming to the upper edge of the optic  62  until a U-bend  78  at approximately the 2:00 position. The strut  70  then reverses in a counter-clockwise direction to a 90 degree bend  80  at the 12:00 position, the strut extending directly radially outward therefrom to the enlarged foot  72 .  
         [0026]    The second fixation member  66  includes an elongate, curved strut  82  attached the optic  62  that diverges to a pair of outer struts  84   a ,  84   b . The curved strut  82  commences at a reinforced region  86  at about the 4:00 position on the outer edge of the optic  62  and extends in a clockwise direction a small distance  88  away from and conforming to the lower edge of the optic  62  until a three-way junction portion  90  at approximately the 6:00 position. The two outer struts  84   a ,  84   b  diverge outward by an included angle of about 90 degrees and terminate in feet  92   a ,  92   b , each of which is angled with respect to the outer strut so that the feet point away from one another. In a particularly preferred embodiment, the two outer struts  84   a ,  84   b  have a thickness, and the feet  92   a ,  92   b  also have a thickness that is approximately the same as the struts. The advantage of such a configuration will be described below in reference to a method of implantation.  
         [0027]    The combination of the enlarged foot  72  of the first fixation member  64  and the bifurcated feet  92   a ,  92   b  on the second fixation member  66  results in a three-point fixation of the intraocular lens  60  within the eye. More specifically, and with reference again to FIG. 2, the enlarged foot  72 , and bifurcated feet  92   a ,  92   b  are implanted in the cornea  14  from the inside or posterior aspect of the cornea, and support the optic  62  along the optical axis  63 .  
         [0028]    There are a number of ways to implant fixation members of intraocular lenses into the cornea  14 . Perhaps the easiest way is to create incisions from the posterior face of the cornea  14 . Another solution is to create elongated tunnels within the cornea from the outside. Subsequently, the intraocular lens is inserted into the anterior chamber and the fixation members are positioned within the tunnels. In this manner, the fixation members are not directly adjacent to an incision leading to the outer face of the cornea, and thus they remain securely implanted in the eye.  
         [0029]    Another consideration is the particular positioning of the fixation members within the corneal layers. It has been found that the middle stroma layer  38 , as seen in FIGS. 1 and 2, is most suited for receiving the fixation members because of its relative thickness with respect to the other layers, and because it relatively tougher and less susceptible to wear from the inserted fixation members.  
         [0030]    One example of an implantation procedure of the present invention is shown schematically in FIGS.  3 ,  3 A- 3 B, and  4 A- 4 B. With reference to FIG. 3, the outer circle represents the cornea  14 , as viewed from the front. In a first step, a so-called phaco incision  100  is created from the outside or anterior aspect  102  of the cornea  14  through to the inside or posterior aspect  104 .  
         [0031]    The plan view of the incision  100  is seen in FIG. 3, with a schematic sectional view shown in FIG. 3A through the cornea  14  (note that the various layers of the cornea are not illustrated for clarity). As viewed from the front view of FIG. 3, the incision  100  has a circumferential width W about the optical axis OA, a generally radial length L, and a depth through the corneal layers. As seen in FIG. 3A, the incision  100  desirably includes three sub-incisions: an entrance sub-incision  106  from the anterior aspect  102  into the stroma (not shown), a tunnel sub-incision  108  extending within the stroma, and an exit sub-incision  110  opening to the posterior aspect  104 . As illustrated, the entrance sub-incision  106  is generally perpendicular with respect to the anterior aspect  102 , the exit sub-incision  110  is generally perpendicular with respect to the posterior aspect  104 , and the tunnel sub-incision  108  extends within the stroma and generally perpendicular to both of the other sub-incisions. In practice, due to the minute distance involved, these sub-incisions will not likely assume such idealized configurations, but will be formed in this stepped configuration nonetheless.  
         [0032]    In an exemplary embodiment, the entrance sub-incision  106  has a circumferential width W of approximately or about 3 mm and extends through the corneal layers a depth of approximately 0.25 mm. The tunnel sub-incision  108  also has a width W of about 3 mm, and a radial length L of about 2 mm. Finally, the exit sub-incision  110  has the same circumferential width as the tunnel sub-incision  108 , and extends through the corneal layers a depth of approximately 0.25 mm. The average depth of the cornea  14  is about 0.5 mm, so the tunnel sub-incision  108  desirably lies in a plane of the cornea  14  that is midway between the anterior and posterior aspects  102 ,  104 , and within the stroma.  
         [0033]    In one embodiment, the tunnel sub-incision  108  is widened at a pair of pockets  112   a ,  112   b . These pockets  112   a ,  112   b  may take a variety of forms, and are illustrated as rounded incisions. The pockets  112   a ,  112   b  extend in the stroma layer in the same plane as the rest of the tunnel sub-incision  108 .  
         [0034]    A secondary incision  120  is formed in the cornea  14  at a location that is approximately diametrically opposite from the phaco incision  100 . The secondary incision  120  has a width w, a length  1 , and a depth, as seen in the section view of FIG. 3B. The incision  120  may be formed from the outside or anterior aspect  102  of the eye, or from the inside or posterior aspect  104  using an instrument passed through the phaco incision  100 . Therefore, an exit sub-incision  122  is shown in dashed line extending generally perpendicular from the anterior aspect  102 . A tunnel sub-incision  124  extends generally perpendicularly through the stroma layer from the exit sub-incision  122 , and leads to an entrance sub-incision  126  opening generally perpendicularly to the posterior aspect  104 . The tunnel sub-incision  124  extends generally radially, such that the exit sub-incision  122  is located radially outward from the entrance sub-incision  126 . As before, these sub-incisions are shown as idealized, and likely will not have such sharp and well-defined intersections.  
         [0035]    In an exemplary embodiment, the width w of the secondary incision  120  is about 1 mm, while the length  1  is about to mm. The depth of the stepped sub-incisions are as described above with respect to the phaco incision  100 , with the tunnel sub-incision  124  being generally located in the stroma and in a plane that is midway between the anterior aspect  102  and posterior aspect  104 .  
         [0036]    The phaco incision  100  is sized to permit introduction of the intraocular lens  60  of the present invention to the anterior chamber. Specifically, the incision  100  is sized to permit the intraocular lens  60  to pass therethrough in a folded configuration.  
         [0037]    A method of implanting the intraocular lens  60  into an eye  12  will now be described with respect to FIGS.  4 A- 4 B. Various techniques instruments are known for incising the cornea  14 , and for a introducing and manipulating intraocular lenses within the anterior chamber  18  (FIG. 1) of the eye. For example, various diamond keratomes or blades may be used to form the incisions  100 ,  120 , and a conventional Bartell type intraocular lens folding system used to introduce the intraocular lens  60  through the phaco incision  100 . Manipulation of the intraocular lens  60 , and in particular the fixation members  64 ,  66  may be accomplished using forceps or other such fine grabbing tools. Description of these various implements will not be included herein, as they are well-known by those of skill in the art.  
         [0038]    The first step in implantation comprises the formation of the phaco incision  100  from the outside or anterior aspect of the eye. As described above, the incision  100  is desirably stepped as indicated in FIG. 3A, with a relatively large tunnel sub-incision  108  being formed parallel to the corneal layers, and within the stroma. Subsequently, the secondary incision  120  is formed, either from the outside or anterior aspect of the eye, or from the inside or posterior aspect. In the latter instance, a suitable keratome may be inserted through the phaco incision  100  to form just the entrance sub-incision  126  and tunnel sub-incision  124 , as indicated in FIG. 3B. Alternatively, the secondary incision  120  may be formed from the outside, with the three sub-incisions  122 ,  124 , and  126  being formed in sequence.  
         [0039]    The intraocular lens  60  can then be introduced to the anterior chamber  18  through the phaco incision  100 . After unfolding, the intraocular lens  60  is desirably in an orientation as seen in FIG. 4A, or is manipulated into that orientation, with the first fixation members  64  extending generally toward the secondary incision  120 , and the second fixation members  66  extending generally toward the phaco incision  100 .  
         [0040]    The first fixation members  64  is then inserted into the secondary incision  120  by passage of the enlarged foot  72  through the entrance sub-incision  126  and into the tunnel sub-incision  124  (see FIG. 3B). This relative arrangement seen in FIG. 4A. The radial length  1  of the tunnel sub-incision  126  is approximately the same as the length of the radial portion of the strut  70  between the 90° bend  80  and the enlarged foot  72 . In this manner, the 90° bend  80  is positioned within the anterior chamber  18 , closely adjacent to the entrance sub-incision  126 .  
         [0041]    Because of the flexibility of the fixation members  64 ,  66 , the intraocular lens  60  can be manipulated to implant the second fixation member  66  into the phaco incision  100 . In a preferred embodiment, the spacing between the feet  92   a ,  92   b  is slightly larger than the width W of the incision  100 . Therefore, the diverging outer struts  84   a ,  84   b  are first bent inward toward one another so that the feet  92   a ,  92   b  can pass through the exit sub-incision  110 . After proper positioning of the second fixation member  66 , with the three-way junction portion  90  remaining within the anterior chamber  18  just adjacent the exit sub-incision  110 , the diverging outer struts  84   a ,  84   b  are released such that the feet  92   a ,  92   b  spring outward to the sides of the tunnel sub-incision  108 .  
         [0042]    As mentioned above, the optional pockets  112   a ,  112   b  may be provided to receive the feet  92   a ,  92   b . Alternatively, the feet  92   a ,  92   b  may contact the sides of the tunnel sub-incision  108 , such that the resilient bias of the struts  84   a ,  84   b  holds the fixation member  66  in place. Furthermore, because the feet  92   a ,  92   b  are not enlarged as are prior art acrylic lens fixation members for use in the iridio/corneal angle, they may become embedded in the stroma layer on the sides of the tunnel-incision  108 . This anchoring effect helps prevent movement of the intraocular lens  60  within the cornea  14 . In any event, the intraocular lens  60  is positioned as seen in FIG. 4A, with the optic  62  in the desirable centered position.  
         [0043]    [0043]FIG. 4B shows the exemplary intraocular lens  60  of the present invention positioned in the anterior chamber  18  of the eye  12 , and desirably centered along the optical axis OA for focusing light at or near the retina (not shown). Desirably, the optical axis  63  of the intraocular lens  60  coincides with the optical axis OA of the natural eye. As mentioned above, the fixation members  64 ,  66  extend directly radially outward or outward and forward from the typically circular optic  62  and are implanted in the cornea  14  from the inside, or posterior aspect of the cornea. The ends of the fixation members  64 ,  66  reside within the stroma  38 , and in particular within the tunnel sub-incisions as described above. The optic  62  is thus positioned and suspended by the fixation members  64 ,  66  so as not to touch the cornea, which might result in harmful endothelial cell loss.  
         [0044]    In one embodiment, as shown, the struts  84   a ,  84   b  are divergent to an extent that they provide good balance for the intraocular lens  60  when implanted in the cornea. That is, the struts  84   a ,  84   b  and feet  92   a ,  92   b  are desirably centered about a vertical plane intersecting the optical axis OA, and thus support approximately the same amount of weight of the lens. Therefore, in combination with the implantation of the first fixation member  64 , the second fixation member  66  helps prevent movement of the lens in the anterior chamber.  
         [0045]    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. For example, although only two fixation members are shown, there may be three or more. Alternatively, only one of the disclosed fixation members may be used in combination with one or more other types of fixation member.