Abstract:
An intraocular lens having an optic and a plurality of fixation members coupled to the optic. The fixation members are adapted to be evenly circumferentially distributed about the anterior chamber to reduce the phenomenon of malshaping the iris, for example, pupil ovalling.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to intraocular lenses (IOLs). More particularly, the invention relates to IOLs placed in the anterior chambers of eyes, and to methods for inserting IOLs in such anterior chambers, which reduce the risk of malshaping the iris of the eye, for example, ovalling the pupil formed by the iris. 
     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 of the eye, that is, the region of the eye posterior of the cornea and anterior of the iris. 
     Referring now to FIG. 1, an anterior IOL (AIOL)  10  of the prior art is shown implanted in an eye  12 . The eye  12  comprises a cornea  14  shown to the left and an iris  16  shown in the middle of the eye. It is to be understood that the cornea  14  is at the front of the eye  12 . The iris  16  divides the eye  12  into an anterior chamber  18  at the front of the eye and a posterior chamber  20  in back of the iris. The iris  16  also defines the pupil  22 , which is an opening in the middle of the iris. In front of the iris  16  is the scleral spur  24 . The scleral spur  24  and the iris  18  delimit the ciliary band  26 . Behind the iris  16  is the ciliary process  28 , from which extends the ciliary muscle  30 . The ciliary muscle supports the natural crystalline lens  32  of the eye  12 . The iris  16  and the ciliary process  28  define the sulcus  34 . 
     FIG. 1 shows the AIOL  10  implanted in the anterior chamber  18  of the eye  12 . The AIOL  10  is comprised of an optic  40  that is supported in front of the pupil  22  by fixation members  42 , sometimes known as loops or haptics. The optic  40 , for the AIOL  10  and other IOL&#39;s described herein, may be considered as including an optical portion for focusing light at or near the retina (not shown) of the eye  12 . The fixation members  42  extend from the optic  40  to rest in the ciliary band  26 , and are designed to minimize compression stress on the optic  40  and inhibit forward vaulting of the optic. If the optic  40  vaults and contacts the cornea  14 , an undesirable condition known as endothelium tough may occur. However, this condition may occur from the fixation members  42  merely residing in the ciliary band  26 . 
     Current anterior chamber IOLs have fixation systems that are shorter in one dimension to facilitate passage through a minimum incision size. For example, one AIOL of the prior art includes a rectangular arrangement of footplate haptics. Such AIOLs have a tendency to malshape, e.g., oval, the iris of the eye, which is not acceptable from a cosmetic point of view. In addition, malshaping is an indication of a possible misfit of the IOL, which can result in impaired vision and/or additional surgery to replace the IOL. 
     It would be advantageous to provide anterior chamber IOLs which reduce the risk of malshaping the iris of the eye. 
     SUMMARY OF THE INVENTION 
     New IOLs for implantation in eyes, in particular in anterior chambers of the eyes, have been discovered. The present IOLs effectively reduce the risk of malshaping the iris of the eye, are adapted to be effectively fixated in the anterior chamber of the eye, and provide desired vision correction. In general, the present IOLs include fixation systems which facilitate effectively fixating the IOLs in the anterior chamber of the eye and, in addition, reduce or even substantially eliminate the risk of malshaping the iris. The present IOLs are straightforward in construction and can be produced using conventional and well known techniques. Thus, the present IOLs provide substantial benefits without dramatic changes in IOL design and insertion procedures. 
     In one broad aspect of the present invention, IOLs for implantation in an eye, in particular an anterior chamber of the eye, are provided. Such IOLs comprise optics and fixation systems. The optic has an optical axis and is effective to direct light toward the retina of the eye. The present IOLs can be employed with or without the natural lens being present. One advantage of having the present IOLs in the anterior chamber of the eye is that the optic of the present IOL is spaced apart from the natural lens, if present. Such separation advantageously protects the natural lens from cataract formation or other detrimental conditions which may be caused by contact between the optic and the natural lens. 
     The present fixation system is coupled to the optic and includes at least three distal ends extending radially outwardly of the optic. These distal ends are adapted to be in contact with a peripheral region of the anterior chamber of the eye, for example, to facilitate fixating the IOL in the anterior chamber. Each of the distal ends of the fixation system is substantially equidistantly spaced apart from the closest circumferentially adjacent distal ends. This structure is very effective in spreading or equalizing the stress on the peripheral region of the anterior chamber and the iris caused by the presence of the IOL. Such substantial stress uniformity is believed to be one important factor in reducing the risk of malshaping the iris as a result of the presence of the IOL in the anterior chamber. In one embodiment, the IOL of the present invention is made of a material that is resilient enough to be folded for insertion through narrow access passages or incisions into the anterior chamber of the eye. 
     In addition, the distal ends preferably include a structure enlarged relative to a portion of the fixation system proximal of the distal ends. Such enlarged structure at the distal end is advantageous, for example, in guarding against the harmful effects of excessive contact stresses between the fixation system and the tissue at the peripheral region of the anterior chamber, which is susceptible to being damaged. The present IOLs are effectively fixated in the anterior chamber of the eye and effectively reduce one or more of the detrimental effects often caused by having anterior chamber IOLs fixated in the anterior chamber. 
     The present IOLs can be produced in any suitable manner. A number of conventional IOL manufacturing techniques, which are well known in the art, are effective. Such techniques include, but are not limited to, polymerization techniques, and/or polymeric material molding, casting and/or machining. The fixation members can be provided, together with the optic, as part of a single piece lens, or can be coupled to the optic during formation of the optic, for example, during polymerization to produce the optic, or after the optic is formed. The specific methodology or methodologies by which the present IOLs are produced is not a critical aspect of the present invention. 
     Any and all features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such 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 an eye and an exemplary anterior intraocular lens of the prior art implanted therein; 
     FIG. 2 is a vertical sectional view of an eye and an exemplary anterior intraocular lens of the present invention implanted therein; 
     FIG. 3 is a front elevational view of a first embodiment of an intraocular lens of the present invention having four radially directed fixation members; 
     FIG. 4 is a front elevational view of a second embodiment of an intraocular lens of the present invention having three spirally directed fixation members; 
     FIG. 5 is a front elevational view of a third embodiment of an intraocular lens of the present invention having two pairs of connected fixation members; 
     FIG. 6 is a front elevational view of a fourth embodiment of an intraocular lens of the present invention also having two fixation members, each defining two points of contact with the eye. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 2 and 3, a first embodiment of an IOL in accordance with the present invention, shown generally at  50 , is seen in elevational view mounted within a peripheral region of the anterior chamber  18 . The IOL  50  comprises a central optic  52  having an optical axis  54 , and a plurality of fixation members  56   a-d . In this embodiment, there are four such fixation members  56  distributed equally about the circumference or periphery of optic  52 . Each fixation member  56  is coupled or attached to the optic  52  and extends outwardly substantially the same distance therefrom into contact with the peripheral “angle” or ciliary band  26 . The four distal ends  58  preferably are located in substantially the same plane. In this manner, the fixation members  56  support the optic  52  and maintain the optical axis  54  properly positioned within the anterior chamber  18 . 
     The fixation members  56  may be constructed of a different material than optic  52 , or alternatively may be formed integrally or unitarily as a single piece with the optic. Desirably, the optic  52  and fixation members  56  are polymeric and resiliently deformable. For example, the optic  52  and fixation members  56  may be formed from polymethylmethacrylate, silicone polymeric materials, acrylic polymeric materials, hydrogel-forming polymeric materials and mixtures thereof. The optic  52  and/or fixation members  56  may be substantially rigid. Desirably, the optic  52  is disk-shaped, preferably having a substantially lenticular cross-section, as seen in FIG.  2 . Although the optic  52  preferably is substantially circular in a plane perpendicular to the optical axis  54 , the optic may have any suitable configuration. Also, the optic  52  has an anterior face and a posterior face which may independently have any configuration, e.g., convex, concave, plano and the like, suitable to meet the vision needs of the patient wearing IOL  50 . In addition, FIG. 2 illustrates the fixation members  56  extending in a posterior direction from the optic  52 , and each may be planar or curvilinear. 
     In one embodiment, the IOL of the present invention is made of a material that is resilient enough to be folded for insertion through narrow or small incisions, for example, on the order of about 3.5 mm or smaller, in the sclera or cornea, into the anterior chamber of the eye. is more symmetric than that of the prior art, and is generally too wide to be inserted through small incisions without being first folded or otherwise deformed for insertion. 
     The four fixation members  56  of the IOL  50  seen in FIG. 3 are identical and extend directly radially outwardly from the optic  52 . More specifically, each fixation member  56  terminates at a radially outward distal end  58  designed to safely contact the ciliary band or angle  26 . The distal end  58  preferably includes an enlargement  60  relative to a proximal neck portion  62  that is located between the enlargement and the optic  52 . In the embodiment shown in FIG. 3, the cross-section of each fixation member  56  narrows to a minimum at the neck portion  62 . From the neck portion  62 , each fixation member  56  gradually increases in a proximal direction through a shoulder portion  64  to smoothly join on both sides substantially along tangent lines of a circle  66 , the circle generally defining the operating portion of the optic  52 . 
     As mentioned, each of the four fixation members  56  extends directly radially outwardly from the optic  52  and is substantially evenly circumferentially distributed, along with the other fixation members, about the optical axis  54 . Therefore, FIG. 3 illustrates two orthogonal axes  68  and  70  passing through the optical axis  54 , and along which the four fixation members  56  extend. Because the fixation members  56  have the same radial dimension, imaginary lines drawn connecting the distal ends  58  define a square. As a result of the equidistant circumferential spacing, the IOL  50  exerts substantially uniform reaction forces against the ciliary band or angle  26  through the fixation members  56 . More to the point, the optic  52  is positioned in the anterior chamber  18  by the fixation members  56  with a reduced risk of causing ovalling of the pupil. 
     The enlargement  60  can be a variety of shapes, as long as the edge contacting the ciliary band or angle  26  is rounded or otherwise shaped to reduce the risk of injury to the ciliary band  26  relative to a substantially identical IOL with fixation members including no such enlargements. For example, the enlargement  60  can be substantially disk-shaped, semi-circular, spherical, bulbous or other such shape. As will be apparent to one of skill in the art, the relatively large contact surface at the distal end  58  of each fixation member  56  helps to reduce contact stresses imparted to the ciliary band  26 . This in turn reduces irritation of the ciliary band  26 . In addition, the enlargement  60  on the distal ends  58  may be solid, but may also be rings or have other suitable non-solid configurations (not shown). 
     The neck portion  62  provides flexibility to the fixation members  56  in both the plane common to the axes  68  and  70 , and in the Z-axis perpendicular to said plane. Because of the flexibility of the fixation members  56 , the IOL  50  is able to respond to dynamic fluid forces within the anterior chamber  18 , and to muscular movements of the ciliary band  26 . At the same time, the gradually widening neck portion  62  reduces the stress level in each fixation member  56  adjacent the optic  52 . 
     FIG. 4 illustrates an alternative IOL  80  in accordance with the present invention. Except as expressly described herein, IOL  80  is constructed and functions similarly to IOL  50 . 
     IOL  80  includes a centrally located optic  82  supported by three fixation members  84   a-c.  As with the embodiment shown in FIG. 3, the optic  82  has an operating or optical portion generally defined within a circle indicated by the dashed line  86 . The optic  82  has a central optical axis  88 . In addition, the fixation members  84  are coupled or attached to the optic  82  and extend radially outward therefrom into contact with the ciliary band or angle  26 . 
     Each of the fixation members  84   a-c  comprises a distal end  90  having an enlargement  92  relative to an adjacent neck portion  94 . The neck portion  94  becomes gradually wider in a proximal direction and terminates in a shoulder portion  96  adjacent the optic  82 . As before, each of the enlargements  92  can be a variety of shapes, but are desirably rounded or otherwise shaped to reduce the contact stress and attendant irritation imparted on the ciliary band  26 . 
     FIG. 4 illustrates three rays  100   a-c  extending radially outward from the optical axis  88  and distributed 120 degrees with respect to each other. The distal end  90  of each of the fixation members  84  contacts the ciliary band  26  along one of the rays  100   a-c . The fixation members  84  are thus distributed circumferentially evenly about the optical axis  88 , and support the optic  82  within the anterior chamber  18  in a manner that reduces or even substantially eliminates the risk of ovalling the pupil. Stated another way, lines joining the three distal ends  90  define an equilateral triangle. 
     Rather than extending directly radially outward from the optic  82 , the fixation members  84   a-c  extend outwardly in a spiral fashion (clockwise in accordance with the drawing). That is, the distal end  90  of each fixation member  84  lies along a radial line that is rotated with respect to a radial line passing through the associated shoulder portion  96 . To illustrate, FIG. 4 shows a ray  102  passing approximately through the midpoint of the shoulder portion  96  of the fixation member  84   a . The ray  100   a  passing through the distal end  90  of the same fixation member  84   a  is rotated in a clockwise direction by an angle  104  with respect to the ray  102 . 
     Because the fixation members  84  extend in a spiral fashion from the optic  82 , the wide shoulder portion  96  joins the optic on an outer side at an approximate tangent line with respect to the circle  86 , and forms a tight curve on the inner side. This arrangement provides more radial flexibility for the fixation members  84  with respect to the fixation members  56  shown in FIG.  3 . At the same time, the wide shoulder portion  96  helps to reduce stress adjacent the optic  82 . 
     FIG. 5 illustrates a further IOL  110  in accordance with the present invention. Except as expressly described herein, IOL  110  is constructed and functions similarly to IOL  50 . 
     IOL  110  has two pairs of connected fixation members. Again, the IOL  110  comprises a central optic  112  supported by a plurality of outer fixation members  114   a-d , in this case four, in contact with the ciliary band or angle  26 . The optic  112  is supported by the fixation members  114  in the anterior chamber. 
     Orthogonal axes  118  and  120  passing through the optical axis  116  are shown, and the distal ends  122  of the four fixation members  114  each lie at the intersection of one of these axes  118  and  120  and the ciliary band  26 . Because of the size and configuration of the fixation members  114 , lines connecting the distal ends  122  define a square. In other words, the distal ends  122  of the fixation members  114  are circumferentially distributed evenly about the optical axis  116  and serve to support the optic  112  while reducing the risk of ovalling of the pupil. 
     The IOL  110  defines something of an H-shape, with the optic  112  positioned along the bridge of the H. Each of the legs of the H defines two of the fixation members  114 . That is, the fixation members  114   a  and  114   b  are generally co-linear and project in opposite directions, as are the fixation members  114   c  and  114   d.  Each pair of coupled fixation members  114  associated with each leg of the H is attached to the optic  112  at a common bridge portion  124  that is relatively narrow and widens at a shoulder portion  126  providing a smooth transition to the optic. Again, an imaginary circle  128  is shown to represent the boundary of the operating portion of the optic  112 , and thus the boundary of the shoulder portion  126 . 
     Each leg of the H-shaped IOL  110  comprises a central junction region  130  radially outward from the bridge portion  124 . The two associated fixation members  114  project directly away from the junction region  130 , and each other, generally along a chordal line of the ciliary band  26 . 
     Each fixation member  114  terminates at the distal end  122  in an enlargement  132 , which is wider than an adjacent primary neck  134 . Continuing from the primary neck  134  away from the distal end  122 , a reinforced portion  136  is provided, and then a secondary neck  138  joins to the junction region  130 . In the illustrated embodiment, the IOL  110  is symmetric about both a vertical line, and about a horizontal line. 
     As was explained above, the narrowed bridge portion  124 , and primary and secondary necks  134 ,  138  provides suitable flexibility for the IOL  110  to respond to dynamic forces within the eye. In addition, the shoulder portion  126 , junction region  130 , and reinforced portion  136  provide suitable structural strength to enable the fixation members  114  to center the optic  112 , and reduce the level of stress at any one point. Finally, the relatively large radius of curvature of the enlargement  132  helps reduce irritation to the ciliary band  26 . 
     FIG. 6 illustrates a still further embodiment of an IOL  140  in accordance with the present invention. Except as expressly described herein, IOL  140  is constructed and functions similarly to IOL  50 . 
     The IOL  140  comprises an optic  142  centered about an optical axis  144 , and a pair of members  146   a-b.    
     Each member  146  extends outward from the optic  142  and contacts the ciliary band  26  at two points. More specifically, the upper and lower members  146   a,b  are shaped somewhat like a foot with a toe portion  150 , a foot portion  152 , a heel portion  154 , and an ankle portion  156 . The ankle portion  156  narrows to a bridge portion  158  that attaches or is coupled to the optic  142 . The toe portions  150  of each member  146  point in a counter clockwise direction with respect to the optical axis  144 . That is, each fixation member  146  first extends generally directly radially outward from the optic  142  along the bridge portion and ankle portion  156  to contact the ciliary band  26  at the heel portion  154 . The foot portion  152  extends generally along a chordal line with respect to ciliary band  26  and terminates at the toe portion  150 . Again, the optical zone of optic  142  is defined generally within a circle  160 . 
     Both the toe portion  150  and heel portion  154  of the two members  146  contact the ciliary band  26  and are distributed circumferentially evenly about the optical axis  144 . Therefore, while the IOL  140  is defined as having two members  146 , the IOL  140  has four fixation members with each of the toe portions  150  and heel portions  154  considered the distal end of separate, connected fixation members. Consequently, then there are two pairs of connected fixation members, each connected pair being joined to the optic  142  at a common point. 
     Two orthogonal axes  162  and  164  are shown intersecting at the optical axis  144 . Both toe portions  150  contact the ciliary band  26  along the first axis  162 , while both heel portions  154  contact the ciliary band  26  along the second axis  164 . In other words, imaginary lines drawn connecting the toe portions  150  and heel portions  154  define a square. Because of the particular shape of the IOL  140 , half of the lens is a mirror image of the other half as viewed across either axis  162  or  164 . As in the earlier embodiments, therefore, the IOL  140  prevents ovalling of the pupil. 
     As can be appreciated from the foregoing, the present IOL may have three, four, or even more fixation members circumferentially distributed in an even fashion about the optical axis. The fixation members may extend directly radially outward from the optic, or may be formed in a variety of shapes. More particularly, the fixation members may all be identically formed, or subsets of the fixation members may be identical with some being different. The IOL may be symmetric about one or more axes, or a portion may be formed as a mirror image of another portion. 
     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.