Abstract:
Accommodative intraocular lens systems having two lenses or one lens and one ring connected by sections of the same material are manufactured from a sheet material, and then the connecting sections are bent to align the optical axis of the lenses. Accommodation is achieved either when the two lenses are moved closer and further from each other, or when the single lens is moved closer and farther from the retina of the eye.

Description:
This application is a Continuation-In-Part of U.S. patent application Ser. No. 07/793,470 filed Nov. 18, 1991 now U.S. Pat. No. 5,275,623. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to intraocular lenses for implanting in the capsular bag of the posterior chamber of the eye after an anterior capsulorhexis. After implantation the lens makes use of the ciliary muscle to adjust the refractive power of the lens. 
     BACKGROUND OF THE INVENTION 
     Cataract extraction is the most common ophthalmic surgical procedure performed in the United States. Extracapsular cataract extraction involves cutting a portion of the anterior capsule (anterior capsulorhexis) followed by removal of the nucleus. Alternatively, a probe may be inserted through the anterior capsule and ultrasonically vibrated, transforming lens material into an emulsion is then irrigated and aspirated from the capsular bag (phacoemulsification). After removal of the natural lens, images no longer focus on the retina and a replacement lens must be provided for clear vision. Replacement lenses can be glasses, contact lenses or intraocular lenses. Of these, intraocular lenses give the greatest convenience and undistorted vision, however, for insertion of a lens, the size of the incision is dictated by the size of the implant rather than requirements of removing the natural lens. Replacement lenses, however, lack the ability of a natural lens to accommodatively focus on near and far objects. 
     When a person looks at an object, light is reflected from the object through the cornea, the aqueous humor, through the pupil and into the lens which converges the light through the vitreous body onto the retina. To clearly focus on near objects, light rays must be bent more. To accomplish this the lens becomes more curved and thicker. Most of this change comes from pulling and relaxing the capsular bag at its equator. The equator of the bag is attached to the ciliary muscle by filaments called the zonules of Zinn which are in turn attached to the ciliary muscle. When looking at an object in the distance, the ciliary muscle relaxes and expands, thereby pulling on the zonules, flattening the capsule and lens. When looking at a near object, the ciliary muscle tenses and contracts moving the muscle sightly inward and relaxing the pull on the zonules, allowing the capsular bag to become more curved and thickened from front to back. The lens itself is composed of interlocking fibers which affect the elastic movement of the lens so that as the lens changes shape the fibers alter their curvature. As a person ages, the accommodative ability of the lens decreases which changes in the eye. Age related eye changes include thickening of the lens, an increase in the amount of insoluble protein in the lens, a migration in the points of attachment of the zonules away from the equator of the capsule, and partial liquefaction of the vitreous body. 
     Lenses are made from transparent material having the shape of a body of rotational symmetry, such as a sphere. The degree of curvature of the surface is inversely proportional to the radius of curvature and the focal length. Parallel light rays converge after being refracted through a convex surface and diverge after being refracted through a concave surface. Refractive power of a lens is dependent upon the refractive index of the lens material and the lens curvature. A simple lens has two sides, each with a curvature. Two lenses separated by a given distance, can be considered as one thick lens having two foci and two principal planes. The focal length of the system is the product of their focal lengths (f 1 ,f 2 ) divided by the sum of their focal lengths minus the distance (d) between them i.e. 
     
       
           F =( f   1   f   2 )/( f   1   +f   2   −d )  
       
     
     When the space between the lenses is not a vacuum but contains a substance, the amount substracted from the sum of the focal length is divided by the refractive index (n) of that substance. 
     
       
           F =( f   1   f   2 )/( f   1   +f   2   −d/n )  
       
     
     The refractive power of a lens system is given by the inverse of the focal length. By using two fixed lenses and varying the distance between them, a system of variable focal length can be constructed. If the curvature of one or both of the lens surfaces increases as the distance between lenses is increased, and decreases as the distance between the lenses is decreased, the change in focal length is enhanced. 
     Several attempts have been made to provide the eye with focal length accommodation. The most familiar of these is a bi or multi-focal lens. These are used in glasses, contacts, and intraocular lenses but have a disadvantage in that the focal accommodation is dependent upon direction of focus. 
     U.S. Pat. No. 4,254,509 discloses a lens which takes advantage of the ciliary muscle. However, this lens is placed in the anterior chamber of the eye. Such implants are at times accompanied by complications such as damage to the vascular iris. 
     U.S. Pat. No. 4,253,199 discloses a lens attached directly to the ciliary body. The lens is in a more natural position but requires suturing to the ciliary body risking massive rupture during surgery and bleeding from the sutures. 
     U.S. Pat. No. 4,685,922, incorporated herein by reference, discloses a chambered lens system for which the refractive power can be changed. Such alteration is permanent, accomplished by rupture of the chambers. 
     U.S. Pat. No. 4,790,847 provides a single lens for in capsular bag implantation using rearwardly biased haptics which engage the capsular bag at its equator and move the lens forward and backward upon contraction and relaxation of the ciliary muscles. 
     U.S. Pat. No. 4,842,601, incorporated herein by reference, discloses a two section deformable lens assembly for implanting in the capsular bag. The lens allows division of refractive power and takes advantage of the action of the ciliary body and zonules on the capsular bag. This lens system is assembled after insertion. 
     U.S. Pat. No. 4,892,543 discloses another two lens assembly for placement in the posterior chamber, possibly in the bag where the capsular bag is not removed. This lens allows dividing the refractive power between two lenses and introduces a variable focal length in one of the lenses by compressing a flexible wall of one lens against the convex surface of the second fixed lens. This requires that the first and second lens be in substantially adjacent positions. 
     U.S. Pat. No. 4,932,966, incorporated herein by reference, presents an accommodative lens in which two lenses joined at their periphery enclosed a fluid filled sack, accommodation being accomplished selectively changing the fluid pressure in the sac. One lens is a rigid base lens and the other lens is membrane-like, the equatorial diameter of the lens assembly being substantially that of a dilated pupil and is supported by bladders or haptics. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides dual and thick lens optics, capable of accommodating focus at a range of distances in a simple unitary structure. It uses the eye capsule&#39;s natural shaping from the ciliary body to accommodate the focus. Embodiments provide for insertion into a small incision, natural centricity, and increased focusing of the components. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of the eye with an accomodative lens of the invention in place. 
     FIG. 2 is a vertical sectional view of an eye. 
     FIG. 3 is a partial sectional view showing an intraocular lens in accordance with the invention within the capsular bag when the eye is focused on a near object. 
     FIG. 4 is a partial sectional view showing the intraocular lens of FIG. 3 when the eye is focused on a distant object. 
     FIG. 5 is a partial sectional view showing an alternate embodiment. 
     FIG. 6 is a schematic side view of the natural lens 
     FIG. 7 is a side view of a thick lens embodiment of the lens assembly. 
     FIG. 8 is a perspective sectional view of the embodiment of FIG.  3 . 
     FIGS. 9A and 9B are side and top views of an alternate unitary lens assembly. 
     FIG. 10 is side view of concave unitary lens. 
     FIG. 11 is a side view of shouldered cylindrical unitary lens. 
     FIG. 12 is a side view of a cylindrical unitary lens. 
     FIGS. 13A and 13B are side and top views of a single shouldered unitary lens. 
     FIG. 14 is a side view of a lens being inserted into a capsular bag in which the lens has been removed through a side opening. 
     FIG. 15 is a side view of a cylindrical lens located in the capsular bag. 
     FIG. 16 is a cutaway view of of a hollow unitary lens. 
     FIGS. 17A and 17B are perspective views of accommodative lenses with FIG. 17A is shown without haptics and FIG. 17B is shown with haptics a helical lens connection. 
     FIGS. 18A and 18B are perspective and side views of cylindrical lenses having haptics. 
     FIGS. 19A,  19 B, are top views of an accommodative lens manufactured from sheet material before bending. 
     FIGS. 19C and 19D are side views of accommodative lenses manufacture from sheet material after bending. 
     FIGS. 20A,  20 B, and  20 C are a top and two side views of a lens manufactured from sheet material. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 shows a cross section of the eye. As light enters the eye it passes through the cornea  1 ; through the aqueous humor in the anterior chamber  2 ; through the pupil located centric of iris  3 ; through the anterior wall of the capsular bag  6   a ; is convergently refracted by the lens  8 ; passes through the posterior wall of capsular bag  6   b ; through the vitreous humor  9  to the retina  10  at the fovea  11 . The shape of the lens capsule is controlled by ciliary muscle  4  attached to the capsule by filaments called zonules  5 . 
     The natural lens, shown in FIG. 6, has a central biconvex nuclear portion  26  surrounded by a concavo-convex menisci  27  a and b. Lenses which are bi convex converge light rays. Lenses which are concavo-convex have a diverging effect on light rays. Therefore the menisci of the natural lens provides a moderating effect on the converging nucleus. The anterior-posterior or polar diameter of the lens is about 5 mm. The equatorial diameter is about 9 mm. 
     When the natural lens  8  is removed through capsulorhexis  25 , the intraocular implant shown in FIGS. 3 and 4 can restore focusing. The implant has an anterior lens  12  with an anterior surface  14  and a posterior lens  13  with an posterior surface  15 . Extending from and connecting the equatorial perimeters of the anterior and posterior lenses i a flexible cell wall  16  forming a discoid cell  17  having an equatorial diameter substantially the same as the capsule  6 . Cell  17  formed by the two lenses  12  and  13  is filled with a fluid (gas or liquid) such as air after implantation. Pressure around the equator of the cell supports the lens assembly in place. 
     FIG. 8 shows the same lens assembly having a cell equatorial diameter of D e , a cell polar diameter of D p , and a polar axis P a P p . The equatorial perimeter  24  of the anterior lens  12  is substantially the size of a pupil (4-5 mm.). 
     Although the lenses may be rigid or flexible, flexible lenses can provide greater accommodation. Anterior and posterior lenses, if rigid can be made out of a biocompatible, transparent material such as PMMA (polymethyl methacrylate), HEMA (hydroxyethyl methacrylate), polysulfones, polycarbonates, or a silicon polymer (polydimethyl siloxanes). Materials for a soft lens would include gel forming polymers such as silica hydrogels, polysaccharides such as hyaluronic acid, or a transparent, lens-shaped sack of polyvinyl alcohol. The equatorial diameter of the anterior lens is about the size of a dilated pupil or 5 mm. Posterior and anterior lenses have a thickness of 1 to 1.5 mm. For a typical eye the anterior radius of curvature for the anterior lens is between 8 and 14 mm., and the posterior radius of curvature for the posterior lens is between 4 and 7 mm. The curvature of both faces of each lens can be altered to correct for differences in the shape of the eye (i.e. myopia). Since both lenses are converging lenses with a space between them, focal length and power is divided between them, however, if desired, the power could be in one lens. The cell wall  16  has a thickness of 0.1 mm., and can be made of a methacrylate, silicon polymer or other biocompatible, flexible material. The discoid shape is preferably an ellipsoid having a polar diameter of about 5 mm, and an equatorial diameter of 9 mm. when filled. When the ciliary muscles  4  relax and swell, the zonnules  5  pull on the equator of the capsule  6 , the lens assembly flattens increasing its equatorial diameter and decreasing its polar diameter thus decreasing the distance between the two lenses and altering the power of the lens assembly. If the lenses are made from a soft material, such as a lens shaped sack filled with polyvinyl alcohol, they also pull into a flatted form enhancing optical power change. To facilitate inserting the lens assembly through an incision, soft lenses could be made of a gel forming polymer and dehydrated (thus shrinking them) and the cell left unfilled until after insertion. After insertion fluids from the surrounding tissue could reconstitute the lenses and fill the cell. The cell could also be filled with a microtube or hypodermic. 
     FIG. 5 shows an alternative form of the invention. In capsular bag  6  is a lens assembly having an anterior lens  19  with anterior curved surface  20  and a posterior lens  21  with posterior curved surface  22 . Extending from and connecting the equatorial perimeters of the anterior and posterior lenses is a flexible, resilient cell wall  23  having a diameter substantially the same as lenses  19  and  21 . The substantially paraboloid cell  24  thus formed may be filled with a fluid (gas or liquid) such as air. Two or more resilient haptics may be substituted for the cell wall to space the lenses and bias them against the capsular poles. The springlike action of the haptics or cell wall bias the lenses against the surface of the capsular poles supporting the lens assembly in place. As the capsular bag is pulled and released by the ciliary muscles, the lenses approach and withdraw from each other to provide focal accommodation. If a soft lens is used a support ring may be provided around the equator of the lens. 
     FIG. 7 shows an embodiment of the invention comprising a thick lens having an anterior surface  29  and a posterior surface  30 . The body of the lens  28  is substantially paraboloid. Paraboloid for the purposes of this invention includes cylindrical, hyperboloid and paraboloid. The lens is made of a resilient material to bias the anterior and posterior surfaces against the capsular poles. This springlike action supports the lens in place such that when the capsular bag is pulled and released, the anterior and posterior surfaces approach and withdraw from each other providing focal accommodation. 
     The lens assemblies shown in FIGS. 5 and 7 can be inserted through an incision substantially the width of the lens then turned or be compressed for insertion. 
     The unitary lens assembly of FIGS. 9A and B has anterior  100  and posterior  102  lens surfaces and a bulged bag engaging central section  104 . The lens assembly is molded in one piece from a compressible optically transparent material such as a hydrogel, silicon rubber and soft acrylics. The lens of FIG. 10 has a rounded central section  106  between the anterior  108  and posterior  110  concave lens surfaces. The lens of FIG. 11 has annular ridges  112 A and  112 B to engage the capsular bag  6 A,  6 B. FIG. 12 shows a lens having a cylindrical body  114 , and is preferably used where the lens is inserted through a lateral capsular incision. The lens of FIGS. 13A and 13B has a single shoulder  116  and a body which forms a continuous curved surface  118  which includes a posterior lens surface. 
     FIG. 14 shows a detail of the lens of FIG. 12 as placed inside the capsular bag. To insert the lens, the lens  120  is compressed laterally and placed in a tube  122  similar to U.S. Pat. No. 5,123,905, incorporated herein by reference, or by specialized forceps such as shown in U.S. Pat. No. 4,950,289, incorporated herein by reference. The tube  122  is placed into the bag  6 A,  6 B and the lens  120  is forced out of the needle gently into the bag. For adequate compression, it is desirable to have a high degree of compressibility and memory in the material, or be able to dehydrate the material. Common hydrogels offer this possibility, but may lack a sufficient index of refraction necessary for proper magnification, however, means for altering the index of refraction exist such as incorporation of a solute into the hydrogel, and such hydrogels are becoming available. Alternatively a very compressible clear silicone compound may be suitable. To increase the index of refraction and to further reduce deformation of the lens surface, the surface may be provided with a thin coating of a harder material such as quartz or PMMA, as is now done in glasses. The lens shown in FIG. 15 has a cylindrical body  120  and a set of C shaped haptics  140 ,  142  to provide greater positional stability. 
     The lens of FIG. 16 is similar to that of FIG. 9 except the center  124  is hollow. This allows greater compressibility for insertion. 
     The lens of FIGS. 17A and 17B has anterior  126  and posterior  128  lenses connected by a compressible helix  130 . The lens of  17 B is provided with bag engaging haptics  132 A and  132 B. 
     The lens of FIG. 18A is similar to that of FIG. 12, however, it is provided with haptics  134 A,  134 B to stabilize the lens. FIG. 18 B shows an alternative haptic  150  which extends from and connects the anterior  100  and posterior  102  lenses. 
     Haptics may be attached to either anterior or posterior surfaces, but should be very flexible to allow for compression into a tube. 
     Macular degeneration requires a very strong lens. Single lenses offer an optical change of about 30 diopters, two lenses can provide up to 60 diopters. However, the greater the magnification, the smaller the field of vision. Presently this is treated by a lens placed in front of the eye (glasses). However, by moving the posterior surface of the magnifier towards the retina, the field of vision can be increased and thus a lens assembly having two lens surfaces such as proposed here could be used for treatment of macular degeneration. Similarly, treatment of severe myopia (nearsightedness) could be treated by use of a convex surface on the posterior and/or anterior lens surfaces. 
     FIGS. 19A, B, C, D show a lens which can be made from a sheet material with some resiliency such as thin acrylic. The anterior  152  and posterior  162  lenses are Fresnal type lenses. These lenses can be provided with haptics  164 A,  164 B. A central ring  158  has an opening  160  to allow vision between the anterior and posterior lenses  152 ,  162 . A bridge  154  connects the lenses with the central section. The bridge  154  is provided with creases  156  for easier bending into as form shown in FIG.  19 C. FIG. 19B shows a similar lens having no haptics. 
     To provide more spring, the lens of FIG. 19D has been provided with a second central ring  158 . Several such sections are possible. The lens would also work if only the anterior lens were a fresnal lens since it would move towards and away from the retina. 
     FIGS. 20A, B, and C show an alternative lens made from sheet material. The lenses  100 ,  102  are connected by a ring  180 . When bent so that the anterior  100  and posterior lenses are located so that the optical axes are aligned, the ring  180  serves to engage the bag. Both halves of the ring may bend in the same direction as shown in FIG. 20 B or opposite directions as shown in FIG.  20 C. 
     The principle of this lens could be adapted into a toy for children to learn about lenses and accommodation by making a pillow with the same features of this lens. The material for this pillow is a special transparent compressible material. Handles located on the greatest circumference could be incorporated into the design. Pulling the handles outward decreases the magnification Releasing or pushing the handles inward would increase the magnification so that it becomes an educational toy.