Abstract:
A supplemental intraocular lens is provided for implantation in the eye to modify the lens system of the eye comprising the cornea and the natural lens or an intraocular lens already implanted in the eye, to create a modified lens system having teledioptic or other diffractive capabilities to correct for macular degeneration. To create the teledioptic lens system, the supplemental intraocular lens has substantially no refractive power except for a high minus lens portion at its center. The supplemental intraocular lens, when implanted on the natural or previously implanted artificial lens in the eye and used without an external lens, allows light rays entering the eye onto the retina of the eye as they would without the supplemental intraocular lens, thus providing unmagnified and peripherally unrestricted vision. When a spectacle lens is placed in front of the cornea, the spectacle lens, cornea, natural or intraocular lens and supplemental intraocular lens provide the eye with magnified and restricted peripheral vision. To create a lens system having other diffractive capabilities, a light diffractive supplemental intraocular lens, such as a prism-shaped intraocular lens, having no refractive power is implanted in the eye. The prism-shaped supplemental intraocular lens, the natural lens or artificial lens already implanted in the eye, and the cornea of the eye create a lens system which redirects the light rays entering the eye onto a portion of the retina away from the macula to create an image unaffected by macula degeneration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to intraocular lenses to be implanted onto a natural or artificial lens in the eye to modify the existing lens system of the eye comprising the cornea and a natural or existing artificial lens. More particularly, the invention relates to an intraocular lens having either a substantially non-refractive configuration with a high minus portion at its center, or a substantially non-refractive prismatic or other diffractive configuration, and which is adaptable for implantation in the eye to modify the natural lens or an existing artificial lens to be adaptable to function as a teledioptic lens or diffractive lens, respectively. 
     2. Description of the Related Art 
     A normal ametropic eye includes a cornea, lens and retina. The cornea and lens of the normal eye cooperatively focus light entering the eye from a far point, i.e., infinity, onto the retina. However, an eye can have a disease known as macular degeneration which can greatly degrade vision. 
     Macular degeneration has become one of the leading causes of blindness in adults. This disease affects the central retinal area known as the macula which receives light focused by the cornea and lens and acute vision. Macular degeneration can lead to a gradual or sudden loss of vision to the level of 20/200 or less. Commonly, loss of vision only affects the central retinal area of about 0.25 to 4 square millimeters, and does not usually progress beyond this area, thereby leaving 95-99% of the retina unaffected. Thus, reading and driving vision can be lost, while peripheral vision remains intact. 
     U.S. Pat. Nos. 4,666,446 and 4,581,031, both to Koziol and Peyman, and both of which are incorporated by reference herein, each disclose intraocular lenses which are implanted in the eye in place of the natural lens to redirect the rays of light to minimize the adverse affect on vision caused by the macular degeneration of the eye. For example, U.S. Pat. No. 4,666,446 discloses an intraocular lens comprising a first portion including a diverging lens and a second portion including a converging lens. The converging lens provides the eye with substantially the same focusing ability of the natural lens prior to implantation of the intraocular lens. Thus, the eye will have decreased visual acuity due to the macular degeneration, but will also have unrestricted peripheral vision. The diverging lens, on the other hand, when combined with a converging lens positioned outside of the eye (e.g., a spectacle lens), provides a magnified image with increased visual acuity but a restricted visual field. Therefore, this type of intraocular lens creates teledioptic lens system, which provides the patient with the choice of unmagnified but peripherally unrestricted vision or magnified but peripherally restricted vision. 
     U.S. Pat. No. 4,581,031, discloses an intraocular lens including a convex portion and a prismatic portion. The combined convex/prismatic lens directs rays of light away from the center of the retina that has been damaged by macular degeneration, and focuses those rays onto an undiseased area of the retina, thus providing greater visual acuity. 
     As discussed above, U.S. Pat. Nos. 4,666,446 and 4,581,031 clearly disclose that it is known to use particular types of intraocular lenses in place of the natural lens to reduce the adverse affect of macular degeneration on vision. However, neither of the patents disclose that it is known to use an intraocular lens to modify an existing lens system in the eye, comprising the cornea and a natural or artificial lens already present in the eye, to create a lens system having the prismatic or teledioptic capabilities discussed above to correct for macular degeneration in the eye. 
     U.S. Pat. Nos. 5,098,444, 5,366,502, 5,358,520, and 4,932,971, as well as world patent application WO 94/07435, each disclose that it is known to attach a supplemental intraocular lens to an existing artificial intraocular lens to correct for ongoing degradation of vision. That is, if the ability of the eye to focus grows worse over time, instead of replacing the entire intraocular lens with a new intraocular lens having a different refractive power, a supplemental intraocular lens can be attached to the existing intraocular lens. This technique is less invasive and hence, less traumatic to the eye. 
     However, like U.S. Pat. Nos. 4,666,446 and 4,581,031, none of these patents discloses a supplemental intraocular lens that can be attached to the natural lens or an existing artificial lens to make the lens adaptable to function as a teledioptic or diffractive prismatic lens of the type described above. Accordingly, a continuing need exists for a supplemental intraocular lens having these capabilities. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a supplemental intraocular lens for modifying the natural lens of an existing artificial lens in an eye to correct for macular degeneration. 
     Another object of the present invention is to provide an intraocular lens for implantation in the eye to modify the lens system of the eye comprising the cornea and the natural or existing artificial lens in the eye, to create a lens system that functions as a teledioptic lens system which, when used without an external lens, provides unmagnified and peripherally unrestricted vision and which, when used with an external lens, provides magnified and peripherally restricted vision to correct for macular degeneration. 
     Another object of the invention is to provide an intraocular lens for implantation in the eye to modify the lens system of the eye comprising the cornea and the natural or an existing artificial lens in the eye to create a lens system which redirects rays of light away from a diseased portion of the retina in the eye and focuses those rays onto an undiseased area of the retina. 
     A further object of the invention is to provide intraocular lenses of the types described above which further include fastening members which enable those intraocular lenses to be secured in the eye. 
     A still further object of the invention is to provide intraocular lenses of the type described above which are capable of being secured directly to the surface of the natural or existing artificial lens in the eye. 
     These and other objects of the invention are achieved by providing a supplemental intraocular lens which is substantially non-refractive except for a high minus portion at its center. The supplemental intraocular lens is adaptable for implantation in the eye in addition to the natural lens or an artificial lens already present in the eye. The intraocular lens modifies the lens system of the eye, comprising the cornea and the natural or existing artificial lens in the eye, to be adaptable to act as a teledioptic lens system. Specifically, the supplemental intraocular lens provides substantially no refractive power when used without an external lens, thus providing unmagnified and unrestricted peripheral vision. On the other hand, when combined with a converging lens positioned outside of the eye, the high minus portion of the supplemental intraocular lens diverges the converging rays of the light and projects the diverging rays onto an area of the retina to provide a magnified image with a peripherally restricted field of view. 
     These and other objects are further achieved by providing an intraocular lens having a prism-shaped or other diffractive portion with substantially no refractive power. The intraocular lens of this type is inserted in the eye to modify the existing lens system of the eye, comprising the cornea and the natural or an existing artificial lens in the eye, to create a modified lens system that directs the rays of light entering the eye onto a portion of the retina different from that onto which the rays are directed without the prism-shaped intraocular lens. In particular, the rays are directed to a portion of the retina not damaged by macular degeneration. 
     The prism-shaped intraocular lens, as well as the teledioptic intraocular lens, each can be attached directly to the natural or artificial lens already in the eye and secured by an adhesive, or can each include fastening members, such as haptics, which secure the intraocular lenses to the eye. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will be more readily appreciated from the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of a normal ametropic eye illustrating, among other things, the cornea, iris and lens of the eye; 
     FIG. 2 is a front view of an example of a bi-concave supplemental intraocular lens according to an embodiment of the present invention, which is substantially non-refractive except for a high minus portion at its center, and is used to convert the natural lens or an existing artificial lens in the eye into a lens having teledioptic capabilities; 
     FIG. 3 is a cross-sectional view of a bi-concave supplemental intraocular lens as shown in FIG. 2; 
     FIG. 4 is a cross-sectional view of an eye having a bi-concave supplemental intraocular lens as shown in FIG. 2 positioned on the natural lens of the eye; 
     FIG. 5 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the supplemental intraocular lens positioned on the natural lens of the eye as shown in FIG. 4; 
     FIG. 6 is a cross-sectional view of an eye into which has been implanted a bi-concave supplemental intraocular lens as shown in FIG. 4, and with which a spectacle lens is being used; 
     FIG. 7 is a front view of a plano-concave supplemental intraocular lens according to an embodiment of the present invention, which is substantially non-refractive except for a high minus portion at its center, and which is used to convert the natural lens or an existing artificial lens in the eye into a lens having teledioptic capabilities; 
     FIG. 8 is a cross-sectional view of the plano-concave supplemental intraocular lens as shown in FIG. 7; 
     FIG. 9 is a front view of a bi-concave supplemental intraocular lens as shown in FIG. 2, having a pair of haptics for securing the supplemental bi-concave intraocular lens into the eye; 
     FIG. 10 is a cross-sectional view of a bi-concave intraocular lens as shown in FIG. 9; 
     FIG. 11 is a cross-sectional view of an eye showing the relationship between the natural lens of the eye and a bi-concave supplemental intraocular lens having haptics as shown in FIGS. 9 and 10, which has been implanted in the eye; 
     FIG. 12 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the supplemental intraocular lens having haptics as mounted to the natural lens of the eye as shown in FIG. 11; 
     FIG. 13 is a front view of an intraocular lens configured for implantation into an eye in place of the natural lens of the eye; 
     FIG. 14 is a cross-sectional view of the intraocular lens shown in FIG. 13 which is configured as a bi-convex lens; 
     FIG. 15 is a cross-sectional view of an alternate configuration of an intraocular lens of the type shown in FIG. 13, which has been configured as a plano-convex lens; 
     FIG. 16 is a cross-sectional view of another alternate configuration of the intraocular lens shown in FIG. 13, with the intraocular lens being configured as a concave-convex intraocular lens; 
     FIG. 17 is a cross-sectional view of an eye into which has been inserted a bi-convex intraocular lens; 
     FIG. 18 is a cross-sectional view of an eye into which is implanted a bi-convex intraocular lens, and which further includes a supplemental bi-concave intraocular lens, as shown in FIG. 2 which has been attached to the existing intraocular lens; 
     FIG. 19 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the bi-concave supplemental intraocular lens as positioned on an existing bi-convex intraocular lens in the eye as shown in FIG. 18; 
     FIG. 20 is a cross-sectional view of the eye as shown in FIG. 18, further illustrating a cross-section of a spectacle lens placed in front of the cornea of the eye; 
     FIG. 21 is a cross-sectional view of the supplemental intraocular lens having haptics as shown in FIGS. 9 and 10, implanted on an existing bi-convex intraocular lens; 
     FIG. 22 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the supplemental intraocular lens as positioned on an existing bi-convex intraocular lens as shown in FIG. 21; 
     FIG. 23 is a front view of an example of a substantially non-refractive prism-shaped supplemental intraocular lens according to an embodiment of the present invention; 
     FIG. 24 is a cross-sectional view of the prism-shaped supplemental intraocular lens as shown in FIG. 23; 
     FIG. 25 is a cross-sectional view of an eye illustrating the supplemental prism-shaped intraocular lens as shown in FIGS. 23 and 24 being positioned on a natural lens in the eye; 
     FIG. 26 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the prism-shaped supplemental intraocular lens as positioned on the natural lens of the eye as shown in FIG. 25; 
     FIG. 27 is a cross-sectional view of an eye having a bi-convex intraocular lens implanted therein, and further having a prism-shaped supplemental intraocular lens as shown in FIGS. 23 and 24 mounted on the bi-convex intraocular lens; 
     FIG. 28 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the prism-shaped supplemental intraocular lens positioned on the bi-convex intraocular lens in the eye as shown in FIG. 27; 
     FIG. 29 is a front view showing a prism-shaped supplemental intraocular lens having a plurality of haptics; 
     FIG. 30 is a cross-sectional view of the prism-shaped supplemental intraocular lens as shown in FIG. 29; 
     FIG. 31 is a cross-sectional view of an eye having a supplemental prism-shaped intraocular lens with haptics as shown in FIGS. 29 and 30 mounted to the natural lens of the eye; 
     FIG. 32 is a cross-sectional view taken through the eye directly behind the iris to further illustrate the supplemental prism-shaped intraocular lens having haptics which has been inserted onto the natural lens of the eye as shown in FIG. 31; 
     FIG. 33 is a cross-sectional view of an eye having a supplemental intraocular lens with haptics shown in FIGS. 29 and 30 mounted on a bi-convex intraocular lens already positioned in the eye; and 
     FIG. 34 is a cross-sectional view of the eye taken directly behind the iris to further illustrate the supplemental prism-shaped intraocular lens with haptics mounted on the bi-convex intraocular lens as shown in FIG.  33 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a cross-sectional view of a normal ametropic eye  100 . The eye  100  includes a cornea  102 , an iris  104 , a lens  106 , a ciliary sulcus  108  adjacent the lens  106 , a zonular ligament  109 , a retina  110  and a macula  112 . As illustrated, the macula  112  is located at the center of the retina  110  and is responsible for providing acute vision, such as that necessary for driving or reading. 
     As shown in FIG. 1, light rays  114  are focused directly on the macula  112  by the cornea  102  and lens  106 . The cornea  102  has, on the average, 40 diopters of plus power, and the lens has 20 diopters of plus power. The combination of the cornea  102  and lens  106  therefore is equivalent to a very strong lens of 60 diopters. The light rays  114  which enter the eye in a direction perpendicular or substantially perpendicular to the front surface of the cornea  102  are focused on the macula  112  and provide acute vision. The light rays  114  striking the cornea  102  obliquely are unfocused and provide peripheral, less acute vision. 
     When macula degeneration exists, visual acuity is decreased, which results in a blurred spot in the center of vision. However, the less acute peripheral vision remains substantially the same as in an eye not suffering from macula degeneration. 
     As discussed in the background section above, in an eye suffering from macula degeneration, a portion of the retina is damaged. The damaged portion of the retina does not sufficiently detect the light rays being focused on that portion by the cornea  102  and lens  106 . Therefore, the person perceives an image with low visual acuity. 
     As further discussed above, the adverse affect of the macula degeneration can be minimized by using a teledioptic lens having a convex lens portion and a concave lens portion as described in U.S. Pat. No. 4,666,446. However, instead of replacing the natural lens  106  with that type of teledioptic lens, the existing lens system of the eye comprising the cornea  102  and natural lens  106  can be converted into a modified lens system having the teledioptic described above, through the use of a supplemental intraocular lens according to the present invention as shown, for example, in FIGS. 2 and 3. 
     FIGS. 2 and 3 are front and side views, respectively, of a bi-concave supplemental intraocular lens  116  according to an embodiment of the present invention. The supplemental intraocular lens  116  is made of a flexible synthetic transparent material, organic transparent material, or a combination of both. Suitable materials are collagen, copolymer collagen, polyethylene oxide or hydrogel, hyaluric acid, mucopolysaacharide or glycoprotein, to name a few. 
     The bi-concave supplemental intraocular lens  116  has, for example, planar or substantially planar surfaces having recessed portions  118  and  120  therein, which are each circular or substantially circular in shape and have a central axis equal to or substantially equal to the central axis of the supplemental intraocular lens  116 . These recessed portions  118  are typically about 1 millimeter to about 3 millimeters in diameter, and the overall diameter of the supplemental intraocular lens  116  can range between about 3 millimeters and about 10 millimeters. The recessed portions  118  and  120  act as a minus lens having a power ranging between −30 diopters to about −120 diopters depending on the diameter of the recessed portion, the thickness of the supplemental intraocular lens  116 , and the shape and depth of the recessed portions  118  and  120 . However, the remainder of the supplemental intraocular lens  116  has no or substantially no refractive power. 
     To implant the supplemental intraocular lens in the eye, an incision is made in the eye through the use of a microkeratome, laser or other suitable surgical device. One side of the supplemental intraocular lens  116  can be coated with glue or any other suitable adhesive. As shown in FIGS. 4 and 5, the supplemental intraocular lens  116  is attached directly to the natural lens  106  and is positioned centrally or substantially centrally on the lens  106 . Accordingly, this modified lens system comprising the cornea  102 , the natural lens  106  and the supplemental intraocular lens  116  functions as a teledioptic lens as described in U.S. Pat. No. 4,666,446. 
     That is, as shown in FIG. 4, the light rays  114  entering the eye are focused by the cornea  102 , the natural lens  106  and the supplemental intraocular lens  116  onto an area of the retina  110 . However, since the supplemental intraocular lens  116  has no refractive power (except for recessed portions  118  and  120 ), the light rays  114  are focused on the same or substantially the same area of the retina that the lens  103  and cornea  102  focus the rays without the supplemental intraocular lens  116 . Hence, this modified lens system will provide the person with virtually the same unmagnified vision and unrestricted peripheral vision that is provided without the supplemental intraocular lens  116 . 
     However, as shown in FIG. 6, a spectacle lens  122 , which is, for example, mounted in a spectacle frame  124 , can be placed in front of the eye  100  in which a supplemental intraocular lens  116  has been implanted. In this example, the spectacle lens  122  is a converging lens which causes the light rays  114  to converge as converging light rays  126  which strike the cornea  102  of the eye at a certain angle of convergence relative to the optical axis of the eye  100 . These converging light rays  126  pass through the cornea  102  and then through the lens  106  and the supplemental intraocular lens  116 . 
     The high minus portion (i.e., recessed portions  118  and  120 ) of the supplemental intraocular lens  116  acts as a diverging lens system which causes the converging light rays  126  to diverge to produce a magnified retinal image  128  on the retina  110 . This combination of a converging spectacle lens  122  and diverging lens system comprising natural lens  106  and supplemental intraocular lens  116  is known as a Galilean telescope. 
     As stated above, recessed portions  118  and  120  of the supplemental intraocular lens  116  provide a high minus lens having a refractive power from about −40 diopter to about −120 diopter, but can have any power suitable for this application. The converging spectacle lens will normally have a power from about +25 diopter to about +35 diopter, but can have any power suitable for this application. The magnification provided by this combination of a spectacle lens  122  and supplemental intraocular lens  116  can range from about 2× to about 4×, depending on the power and vertex distance of the spectacle lens  122 . The field of vision will also range from about 35° to about 45°, depending upon the selected magnification. 
     The supplemental intraocular lens also can have shapes other than bi-concave. For example, as shown in FIGS. 7 and 8, the supplemental intraocular lens  130  according to another embodiment of the invention is plano-concave, and has a planar side  132  and a recessed side  134  having a recessed portion  136  therein. Like supplemental intraocular lens  116 , supplemental intraocular lens  130  has substantially no refractive power except for at the recessed portion  136  which provides a high minus lens as described above. Accordingly, supplemental intraocular lens  130  can be used in a manner similar to that described above with regard to supplemental intraocular lens  116 . 
     That is, supplemental intraocular lens  130  can be placed directly on the surface of a natural lens  106  of the eye  100  in a manner similar to that shown in FIGS. 4 and 5 which pertain to supplemental intraocular lens  116 . Furthermore, a spectacle lens  122 , as shown in FIG. 6, can be used in conjunction with the supplemental intraocular lens  130  to provide a magnified retinal image similar to magnified retinal image  128  as provided by supplemental intraocular lens  116 . Like supplemental intraocular lens  116 , supplemental intraocular lens  130  can be made of flexible synthetic transparent material, organic transparent material or both as described above. The minus lens formed by recessed portion  136  of supplemental intraocular lens  130  can be within the range of about −30 diopters to about −120 diopters. 
     Although the supplemental intraocular lens is shown as being either a bi-concave supplemental intraocular lens  116  or a plano-concave supplemental intraocular lens  130 , the supplemental intraocular lens according to the present invention can any suitable shape, as long as that shape functions to achieve the teledioptic effect discussed above without providing refractive power (except for the high minus portions). Also, the high minus portions need not be at the center of the supplemental intraocular lens, but can be at any suitable location on the lens. Furthermore, as shown in FIGS. 9 and 10, the supplemental intraocular lens according to the present invention can include pair of haptics for securing the supplemental intraocular lens into the eye. In the example shown in FIGS. 9 and 10, the supplemental intraocular lens is a bi-concave supplemental intraocular lens  116  having a pair of haptics  138  and  140 , which are made of a suitable material such as surgical steel or the like. However, a supplemental intraocular lens having any of the shapes described above can include haptics for mounting into the eye  100 . 
     As shown in FIGS. 11 and 12, the supplemental intraocular lens  116  is placed over or proximate to the natural lens  106  of the eye, and the haptics  138  and  140  are attached, for example, to the zonular ligament  109  of the eye. The haptics  138  and  140  therefore secure the supplemental intraocular lens  116  at the front of the natural lens  106  without the need for an adhesive. The supplemental intraocular lens  116  can then be used in the manner described above with or without a spectacle lens  122  to provide unmagnified, unrestricted vision or magnified and peripherally restricted vision. 
     The supplemental intraocular lenses are described above as being used with the natural lens of the eye. However, all of the supplemental intraocular lenses described above can be used with an intraocular lens that has already been implanted in the eye to create a modified lens system having the teledioptic features described above. 
     FIGS. 13 and 14 are front and side schematic views, respectively, of an intraocular lens  142  that is implantable in the eye in place of the natural lens of the eye. In this example, intraocular lens  142  has a bi-convex lens  144  to which are attached haptics  146  and  148  which secure the intraocular lens  142  inside the eye. 
     As is commonly known in the art, the intraocular lens  142  can include a lens having any desirable shape. For example, as shown in FIG. 15, intraocular lens  150  includes a plano-convex lens  152 , and haptics  154  and  156  which are attached to the plano-convex lens  152 . Alternatively, as shown in FIG. 16, the intraocular lens  158  includes a concave-convex lens  160  to which are attached haptics  162  and  164 . Although not specifically shown, the intraocular lens can be bi-concave, or have any other suitable shapes as known in the art. 
     FIG. 17 is a cross-sectional view of an eye  100  into which has been mounted an intraocular lens. As known in the art, the natural lens  106  (see FIG. 1) can be removed by making an incision in the eye  100  with a microkeratome, scalpel, laser or any other suitable instrument. The natural lens  106  can then be removed through the incision, and the intraocular lens inserted through the incision and mounted in the eye. In this example, the intraocular lens is shown as intraocular lens  142  which includes a bi-convex lens  142 . However, the intraocular lens can have any of the shapes described above. 
     As illustrated, the eye  100  includes a cornea  102 , ciliary sulcus  108 , retina  110  and macula  112 . The lens  106  has been removed, along with all or substantially all of the zonular ligament  109  (see FIG.  1 ), and has been replaced with intraocular lens  142 . The haptics  146  and  148  are secured to the ciliary sulcus  108  of the eye to secure the bi-convex lens  144  at the appropriate location with respect to the iris  104  and cornea  102 . Accordingly, the intraocular lens  142  and cornea  102  function as a lens system which focuses light rays  114  onto the macula  112 . 
     As illustrated in FIGS. 18 and 19, the supplemental intraocular lens  116 , for example, can be attached to the front surface of the intraocular lens  142  by glue or any other suitable adhesive. Hence, in a manner similar to that described above with regard to the cornea  102 , natural lens  106  and supplemental intraocular lens  116 , the cornea  102 , supplemental intraocular lens  116  and the intraocular lens  142  function as a lens system which focuses light rays  114  onto the retina  110 . Also, as shown in FIG. 20, spectacle lens  122  can be placed in front of the eye  100  so that the spectacle lens  122 , cornea  102 , supplemental intraocular lens  116  and intraocular lens  142  act as a lens system which creates a magnified image on the retina  110 . Furthermore, as shown in FIGS. 21 and 22, the supplemental intraocular lens  116  having haptics  138  and  140  as shown in FIG. 9 can be implanted in front of the intraocular lens  142  to eliminate the use of adhesive for securing the supplemental intraocular lens  116  onto or proximate to the intraocular lens  142 . 
     The supplemental intraocular lens also can be shaped as a prism as shown in FIGS. 23 and 24. That is, supplemental intraocular lens  166  has front and rear surfaces  168  and  170 , respectively, which are circular or substantially circular in shape having a diameter ranging between about 3 mm and about 10 mm. However, the surfaces  168  and  170  can be oval or any other suitable shape, and the diameters can be any suitable size. The supplemental intraocular lens  166  has no or substantially no refractive power. As shown explicitly in FIG. 24, front and rear surfaces  168  and  170  do not extend parallel or substantially parallel to each other. Rather, front surface  168  extends at an angle “a” with respect to rear surface  170 . The angle “a” can be any practical angle. Hence, as shown in FIG. 24, supplemental intraocular lens  166  has a prism-like cross-sectional shape. 
     However, the supplemental intraocular lens  166  need not have a prism-shaped cross section, but rather, could have any suitable shape which does not provide any refractive power but diffracts the light rays in the manner described below. That is, the lens  166  can have multiple grooves similar to a fresnel lens, or have steps or lines across its surface which diffract the light rays. 
     Supplemental intraocular lens  166  can be implanted onto natural lens  106  as shown in FIGS. 25 and 26. That is, supplemental intraocular lens  166  can be attached to the front of natural lens  106  by glue or any other suitable adhesive in a manner similar to that in which supplemental intraocular lens  116  described above is attached to natural lens  106 . As shown in FIG. 25 specifically, supplemental intraocular lens  166  acts in conjunction with cornea  102  and natural lens  106  to create a prismatic lens system which focuses light rays  114  onto a portion of the retina  110  away from the macula  112 . Because the light rays are focused on to a healthy portion of the retina  110 , the image seen by the person is not adversely affected by the macula  112  that has been damaged due to macula degeneration. Accordingly, vision is greatly improved. 
     Supplemental intraocular lens  166  can also include the modifications discussed above with regard to supplemental intraocular lens  116 . As shown in FIGS. 27 and 28, the supplemental intraocular lens  166  can be attached to an intraocular lens  142  that has been mounted in the eye in place of the natural lens  106 . Supplemental intraocular lens  166  also can include haptics  172  and  174  as shown in FIGS. 29 and 30. As shown in FIGS. 31 and 32, the haptics  172  and  174  can be secured, for example, to the zonular ligament  109  or the ciliary sulcus  108  to secure the supplemental intraocular lens  166  onto or proximate to the front of the natural lens  106  without the use of glue or adhesive. Also, as shown in FIGS. 33 and 34, the supplemental intraocular lens  166  with haptics  172  and  174  can be mounted in front of an intraocular lens  142  already implanted in the eye  100 . 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.