Abstract:
In accordance with the present invention, a multifocal intraocular lens provides greater or lesser refraction in relation to the position of the head and eyes of a user. A multifocal intraocular lens body for insertion into a fluid-filled enucleated natural lens capsule of an eye is provided wherein the lens body encompasses the optical axis of the eye and provides different greater or lesser refraction depending upon the position of the eye.

Description:
[0001]     This application is a continuation of U.S. patent application Ser. No. 10/706,630, filed Nov. 12, 2003, by Marguerite B. McDonald, and is entitled to that filing date for priority. The specification and drawings of U.S. patent application Ser. No. 10/706,630 are incorporated herein in their entirety by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0002]     This invention relates to intraocular lenses (IOLs), specifically, to IOLs that may have a plurality of refractive indices.  
       BACKGROUND OF THE INVENTION  
       [0003]     The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens enclosed by a clear capsule, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The constriction or contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina. The removal of the natural lens leaves the eye with no means to focus at different distances and necessitates the use of bifocal lenses for near and far work.  
         [0004]     Many different IOL designs have been developed over the years and proven successful in phakic and aphakic eyes. IOL implants have been used for years in aphakic eyes as replacements for diseased natural crystalline lenses that have been surgically removed from the eyes. IOLs for aphakic eyes are now implanted after cataract surgery in over 98% of the cases. Visual acuity deficiencies remaining after cataract surgery such as myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (age-related farsightedness) are typically corrected with eyeglasses or contact lenses, though the accuracy of IOL power calcaulation has decreased the need for full-time postoperative spectacle use. The use of surgically implanted phakic IOLs as a permanent form of refractive correction has been gaining in popularity as well, though they are still considered investigational.  
         [0005]     IOLs are generally of a fixed focal length. Fused bifocal and aspheric lenses have two or more optical focal planes that are engaged by changing the relationship of the light path or the observer to the lens. All such lenses require movement of either the lens (not possible with a standard IOL), light path, or observer to engage a different focal plane and can therefore be difficult to use. They also have an adverse effect on contrast sensitivity and can cause glare, halos, double vision (polyopia), and other optical aberration all of which compromises visual quality.  
         [0006]     Accordingly, there is a need for a multifocal intraocular lens having a variable power of refraction that does not require deliberate engagement of different focal planes for near and far vision.  
       SUMMARY OF THE INVENTION  
       [0007]     In accordance with the present invention, a multifocal intraocular lens provides greater or lesser refraction in relation to the position of the head and eyes of a user. A multifocal intraocular lens body for insertion into a fluid- or gel-filled enucleated natural lens capsule of an eye is provided wherein the lens body encompasses the optical axis of the eye and provides different greater or lesser refraction depending upon the position of the eye. In another embodiment, the lens body can be used with an artificial lens capsule implanted within an eye.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     For a more complete understanding of the present invention and for further advantages thereof, reference is now made to the following Description of the Preferred Embodiments taken in conjunction with the accompanying Drawings.  
         [0009]      FIG. 1  is a sectional view of a human eye illustrating the basic components of the eye.  
         [0010]      FIG. 2  is a sectional view of a human eye illustrating the present intraocular lens body inserted within the artificial capsule situated within an eye.  
         [0011]      FIG. 3  is a side-elevated view of the present intraocular lens body and artificial capsule shown in  FIG. 2 .  
         [0012]      FIG. 4  is a plan view of the present intraocular lens body shown in  FIG. 2 .  
         [0013]      FIG. 5  is a sectional view of a human eye illustrating the present intraocular lens body inserted within the natural lens capsule of an eye.  
         [0014]      FIG. 6  is a sectional view of the present intraocular lens body through the line  6 - 6  of  FIG. 3 .  
         [0015]      FIG. 7  is a sectional view of the present intraocular lens body through the line  7 - 7  of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     Turning now to the drawings and first to  FIG. 1  for reference in the following description, the human eye comprises from front to rear an outer transparent cornea  10 , an anterior chamber  12 , an iris  14  containing a pupil  16 , a posterior chamber  18 , and a vitreous cavity  20 . A natural lens  22  comprises a crystalline lens structure  24  contained within an optically clear bag called a lens capsule  26  having a posterior capsule  28  and an anterior capsule  30 . The lens is peripherally joined by zonules  32  to the surrounding ciliary muscles  34 . The vitreous cavity  22  contains vitreous  36 .  
         [0017]     The present invention is particularly useful in correcting the eye disorder known as a cataract which is characterized by progressive opacification of the natural lens  22  and resultant progressive attenuation of the light rays reaching the retina. Simply stated, this condition is corrected by removing the cataract, that is the cataractous (i.e. opaque) nucleus and cortex of the natural lens, and implanting an artificial intraocular lens in the eye. Cataract removal may be accomplished by intracapsular extraction (removal of the entire lens  22 ) or by extracapsular extraction (removal of the cataractous nucleus and cortex through the anterior side of the lens capsule  26 ) utilizing either nucleus expression through a relatively large opening in the eye or phacoemulsification through a relatively small opening in the eye.  
         [0018]     The anterior capsule opening required for extracapsular extraction may be provided by (a) removing most of the anterior capsule  30  except small peripheral remnants of the anterior capsule, (b) tearing the anterior capsule to allow the human lens nucleus to be expressed, or (c) continuous tear circular capsulotomy, i.e. capsulorhexis. The essentially empty lens capsule  26  remaining after removal of the cataract is referred to as a capsular bag. Removal of the nucleus and cortex of the natural lens from the bag creates a space immediately behind the iris  14 , between the latter and the posterior capsule  28  of the bag, which is approximately 10 mm in diameter and 5 mm front to back.  
         [0019]     It is possible to implant an intraocular lens in any one or more of the eye chambers, i.e. anterior chamber  12 , posterior chamber  18 , capsular bag  26 , or vitreous cavity  20 . Intraocular implants according to the present invention may be placed in any one of these eye chambers or cavities. However, the invention is particularly concerned with an intraocular lens body for placement in a natural capsular bag having an anterior capsulotomy or in the anterior or posterior chambers, or in an artificial capsular bag and will be described primarily in these contexts.  
         [0020]     Referring now to  FIGS. 2-4 , in accordance with the present invention, there is illustrated multifocal intraocular lens body  38 , positioned within an artificial capsular bag  40  to form a multifocal intraocular lens system  42 , situated within a human eye from which the natural lens  22  has been removed (i.e. an aphakic eye). Multifocal intraocular lens body  38  has an upper portion  44 , a lower portion  46 , anterior surface  48 , and a posterior surface  50 . The following description of the lens body is as viewed from the medial-lateral axis. Anterior surface  48  and posterior surface  50  of lower portion  46  taper upwardly to form upper portion  44  to provide a tapering periphery  52 . Anterior surface  48  and posterior surface  50  of upper portion  44  of lens body  38  each have at least one radius of curvature having its respective center positioned posteriorly the posterior surface  50  of lens body  38 . An aspheric multifocal intraocular lens body is contemplated in one embodiment of the present lens body. At least one radius of curvature of posterior surface  50  of upper portion  44  of the lens body is preferably shorter than the radius of curvature of that along anterior surface  48  so as to form a comma-shaped lens body or any multifocal shape, preferably aspheric. Multiple radii of curvature are also contemplated as well as possibly a lens made of a material that increases in its index of refraction along the lens axes. As seen  FIGS. 4, 6  and  7 , the lens body is approximately elliptical when viewed anteriorly or posteriorly. The multifocal intraocular lens body may comprise any material suitable as a lens body and having a high index of refraction. Such material is preferably translucent and colorless, such as silicone, gel, or acrylic, and specifically may include polymethylmethacrylate (PMMA). However, such material may have a color for aesthetic or physiological purposes, e.g. to filter unwanted wavelengths such as those in the ultraviolet spectrum.  
         [0021]     Multifocal intraocular lens body  38  is positioned within lens capsule  40 . Lens capsule  40  has anterior surface  54 , posterior surface  56 , upper edge  58 , and lower edge  60 . Lens capsule  40  is approximately circular in shape and adapted to fit in the anterior or posterior chambers of an eye. Anterior surface  54  and posterior surface  56  completely encompass the optical axis formed by pupil  16 . The distance between anterior surface  48  and posterior surface  56  of lens capsule  40  defines a thickness that corresponds to a first axis that extends generally perpendicularly between the surfaces. A second axis that is generally perpendicular to said first axis is also formed. The thickness of the lens capsule along the first axis is smaller than its width along its second axis. Lens capsule  40  can be made from a translucent and colorless pliable or substantially pliable material such as silicone or similar material, or other materials as would be known to one of skill in the art.  
         [0022]     The multifocal intraocular lens body  38  is positioned within the lens capsule  40  so that lower portion  46  of lens body  38  lies adjacent to lower edge  60  of the lens capsule and anterior surface  48  of the lens body lies adjacent to anterior surface  54  of lens capsule  40 . Tapering periphery  52  is the feature of lens body  38  that lies nearest to the approximate center of the lens capsule when the short axis of the lens capsule is parallel to the ground or as when the user is looking straight ahead. The approximate center of the lens capsule encompasses the optical axis of the eye. Multifocal intraocular lens body  38  provides only minimal additional refraction or no refraction consummate with the minimal or no additional refraction or required when looking at infinity, i.e. at the horizon. When anterior surface  54  of lens capsule  40  is tilted downwardly, lens body  38  moves towards upper edge  58  of the lens capsule and begins to “float” or slide more and more over the visual axis (i.e. the line of sight). After implantation, and when the user requires more focusing power, i.e. refraction, such as when reading, lens body  38  similarly slides upwards into the optical axis as the user tilts their head downwardly causing anterior surface  54  of lens capsule  40  to also move downwardly. By doing so, the lower portion of the lens body which has a higher add component, moves into the optical axis and provides greater correction at near. Movement of the multifocal intraocular lens body  38  within artificial capsule bag  40  is slowed by the presence of translucent fluid  62  contained within bag  40 . Translucent fluid  62  may be a liquid, gel, or sol, is preferably visco-elastic, and can be silicone or a related material or a combination of materials. However, any translucent substance capable of slowing movement of the multifocal intraocular lens body  38  within the artificial capsule bag  40  consistent with the practice of this invention is suitable.  
         [0023]     In another embodiment of the present invention, attached to the outside edge of artificial capsule bag  40  is securer  64 . Securer  64  secures artificial capsule bag  40  containing multifocal intraocular lens body  38  within the eye. Securer  64  are preferably positioned so as to extend from upper edge  58  and lower edge  60  of artificial capsule bag  40  and hold the artificial capsule bag  40  in place within either the posterior chamber, the capsular bag or remnants thereof, or anterior chamber, or a combination thereof. Haptics  64 , as shown in  FIGS. 2-4 , are commonly used in the art. Any haptic shape, configuration, or number may be utilized in accordance with the teachings of the present invention. While haptics are satisfactory for the present invention, any other suitable securer is acceptable if a securer is desired.  
         [0024]     Referring now to  FIG. 5 , there is illustrated multifocal intraocular lens body  38  according to another embodiment of the present invention. Multifocal intraocular lens body  38  is placed within capsular bag  26  of the human phakic eye from which the nucleus of the natural lens has been removed, i.e. the lens is enucleated. The capsular bag  26  has an anterior capsulotomy (not shown) through which the lens body  38  is inserted into the bag  26 . In this embodiment the natural lens capsule  26  contains the lens body  38  rather than the artificial capsule bag  40  as described above. The anterior capsulotomy, probably small in size, may be plugged with a natural or synthetic material after the lens body is inserted and the capsular bag filled with a translucent substance. Similarly to the embodiment of the present invention that utilizes an artificial capsule bag  40 , a translucent substance such as a liquid, gel, oil or sol, or any similar substance, is placed within capsular bag  26  to slow movement of the lens body  38 . The structure and composition of the lens body  38  is also as described above with respect to  FIGS. 2-4 .  
         [0025]     Whereas it is intended that the description of the present invention is but one embodiment for implementing the invention. Variations in the description likely to be conceived by those skilled in the art still fall within the breadth and scope of the disclosure of the present invention. It is also understood that additional applications of the present invention will be apparent to those skilled in the art upon a reading of the description and a consideration of the appended claims and drawings.