INTRAOCULAR MULTIFOCAL LENS
A multifocal intraocular lens providing greater or lesser refraction in relation to the position of the head and eyes of a user. The lens body is inserted into an artificial capsule bag or into a fluid-filled enucleated natural lens capsule of an eye, wherein the lens body encompasses the optical axis of the eye and by movement of the lens body within the capsule, provides different greater or lesser refraction depending upon the position of the eye.
This application is a continuation of U.S. patent application Ser. No. 11/464,005, which is a continuation of U.S. patent application Ser. No. 10/706,630, filed Nov. 12, 2003, now issued as U.S. Pat. No. 7,144,423, by Marguerite B. McDonald, and is entitled to those filing dates for priority. The specification and drawings of U.S. patent application Ser. Nos. 11/464,005 and 10/706,630 are incorporated herein in their entirety by specific reference for all purposes.
TECHNICAL FIELD OF THE INVENTIONThis invention relates to intraocular lenses (IOLs), specifically, to IOLs that may have a plurality of refractive indices.
BACKGROUND OF THE INVENTIONThe 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.
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.
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.
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 INVENTIONIn 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.
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.
Turning now to the drawings and first to
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.
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.
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.
Referring now to
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.
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.
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
Referring now to
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.
Claims
1. An intraocular lens, said lens comprising:
- a solid lens body with a top and bottom, having a lower section and an upper section, each section having a front surface and a back surface;
- wherein the lower section is substantially semi-circular in cross-section between the front and back surfaces; and
- wherein the upper section tapers upward to create a tapering periphery at the top of the lens body, the back surface of the upper section being a concave curve, and the front surface of the upper section being a convex curve.
2. The lens of claim 1, wherein the lens is substantially elliptical when viewed from the front.
3. The lens of claim 1, wherein the back surface of the upper section has at least two radii of curvature.
4. The lens of claim 1, wherein the front surface of the upper section has at least two radii of curvature.
5. The lens of claim 1, wherein the front and back surfaces of the upper section each have at least one radius of curvature, and said at least one radius of curvature of the back surface is shorter than the at least one radius of curvature of said front surface.
6. The lens of claim 1, wherein said lens body is formed of a synthetic material.
7. The multifocal intraocular lens of claim 6, wherein said synthetic material is selected from the group consisting of silicone, acrylic, and polymethylmethacrylate.
8. The lens of claim 1, wherein said lens body has at least one index of refraction.
9. The lens of claim 1, wherein said lens body has multiple indices of refraction.
10. The lens of claim 1, wherein said lower section of said lens body has a greater index of refraction or focusing power than said upper section.
11. The lens of claim 1, wherein said lens body is substantially aspheric.
12. The lens of claim 1, wherein said lens body is colored.
Type: Application
Filed: Sep 7, 2012
Publication Date: Dec 27, 2012
Inventor: Marguerite B. McDonald (New Orleans, LA)
Application Number: 13/606,366
International Classification: A61F 2/16 (20060101);