US20080161914A1 - Pre-stressed haptic for accommodating intraocular lens - Google Patents

Abstract

An intraocular lens is disclosed, with an optic that changes shape in response to a deforming force exerted by the zonules of the eye. A haptic supports the optic around its equator and couples the optic to the capsular bag of the eye. The haptic may be pre-stressed before the optic is placed within it. After such placement, the pre-stress may be relieved, and the haptic may produce stress in the optic. The pre-stress may produce a radial tension or a radial compression in the optic. Alternatively, once the optic is placed within the haptic, both may undergo a process that changes the size and/or shape of one with respect to the other, causing a stress within the optic. This process may produce a radial tension or a radial compression in the optic. The haptic may include an annular ring having outer and inner diameters that may depend on the stiffness of the haptic.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention is directed to intraocular lenses, and more particularly to accommodating intraocular lenses.
• 2. Description of the Related Art
• A human eye can suffer diseases that impair a patient's vision. For instance, a cataract may increase the opacity of the lens, causing blindness. To restore the patient's vision, the diseased lens may be surgically removed and replaced with an artificial lens, known as an intraocular lens, or IOL. An IOL may also be used for presbyopic lens exchange.
• The simplest IOLs have a single focal length, or, equivalently, a single power. Unlike the eye's natural lens, which can adjust its focal length within a particular range in a process known as accommodation, these single focal length IOLs cannot generally accommodate. As a result, objects at a particular position away from the eye appear in focus, while objects at an increasing distance away from that position appear increasingly blurred.
• An improvement over the single focal length IOLs is an accommodating IOL, which can adjust its power within a particular range. As a result, the patient can clearly focus on objects in a range of distances away from the eye, rather than at a single distance. This ability to accommodate is of tremendous benefit for the patient, and more closely approximates the patient's natural vision than a single focal length IOL.
• When the eye focuses on a relatively distant object, the lens power is at the low end of the accommodation range, which may be referred to as the “far” power. When the eye focuses on a relatively close object, the lens power is at the high end of the accommodation range, which may be referred to as the “near” power. The accommodation range or add power is defined as the near power minus the far power. In general, an accommodation range of 2 to 4 diopters is considered sufficient for most patients.
• The human eye contains a structure known as the capsular bag, which surrounds the natural lens. The capsular bag is transparent, and serves to hold the lens. In the natural eye, accommodation is initiated by the ciliary muscle and a series of zonular fibers, also known as zonules. The zonules are located in a relatively thick band mostly around the equator of the lens, and impart a largely radial force to the capsular bag that can alter the shape and/or the location of the natural lens and thereby change its effective power.
• In a typical surgery in which the natural lens is removed from the eye, the lens material is typically broken up and vacuumed out of the eye, but the capsular bag is left intact. The remaining capsular bag is extremely useful for an accommodating intraocular lens, in that the eye's natural accommodation is initiated at least in part by the zonules through the capsular bag. The capsular bag may be used to house an accommodating IOL, which in turn can change shape and/or shift in some manner to affect the power and/or the axial location of the image.
• The IOL has an optic, which refracts light that passes through it and forms an image on the retina, and a haptic, which mechanically couples the optic to the capsular bag. During accommodation, the zonules exert a force on the capsular bag, which in turn exerts a force on the optic. The force may be transmitted from the capsular bag directly to the optic, or from the capsular bag through the haptic to the optic.
• A desirable optic for an accommodating IOL is one that distorts in response to a squeezing or expanding radial force applied largely to the equator of the optic (i.e., by pushing or pulling on or near the edge of the optic, circumferentially around the optic axis). Under the influence of a squeezing force, the optic bulges slightly in the axial direction, producing more steeply curved anterior and/or posterior faces, and producing an increase in the power of the optic. Likewise, an expanding radial force produces a decrease in the optic power by flattening the optic. This change in power is accomplished in a manner similar to that of the natural eye and is well adapted to accommodation. Furthermore, this method of changing the lens power reduces any undesirable pressures exerted on some of the structures in the eye.
• One challenge in implementing such an optic is designing the optic so that it does not distort undesirably anywhere in the accommodation range. More specifically, while a change in surface curvature may be desirable for causing a change in optical power, irregularities on one or both surfaces of the optic may undesirably lead to optical aberrations or artifacts and thereby degrade the performance of the optic.
• Accordingly, there exists a need for an intraocular lens having an optic with an increased resistance to undesirable surface irregularities during accommodation.
SUMMARY OF THE INVENTION
• An embodiment is an intraocular lens for implantation into a capsular bag of an eye, comprising a stressed optic; and a haptic for coupling the optic to the capsular bag. The haptic stresses the stressed optic when the intraocular lens is in a natural state.
• A further embodiment is an intraocular lens for implantation into a capsular bag of an eye, comprising an optic; and a haptic for coupling the optic to the capsular bag. The optic is under tension when the intraocular lens is in a natural state.
• A further embodiment is an intraocular lens for implantation into a capsular bag of an eye, comprising an optic having a periphery; and an annular ring engaging at least a portion of the periphery of the optic for coupling the optic to the capsular bag. The annular ring stresses the optic in the absence of an external compressive force on the annular ling.
• A further embodiment is an intraocular lens for implantation into a capsular bag of an eye, comprising an optic having a periphery; and an annular ring engaging at least a portion of the periphery of the optic for coupling the optic to the capsular bag. The optic has a uncompressed surface profile in the absence of an external compressive force on the annular ring. The optic has a compressed surface profile in the presence of an external compressive force on the annular ring. The compressed surface profile is more spherical than the uncompressed surface profile.
• A further embodiment is an intraocular lens for implantation into a capsular bag of an eye, comprising an optic having an equatorial region and a shape, the shape comprising an anterior curvature and a posterior curvature; and a haptic for coupling the optic to the capsular bag. The optic can change its shape in response to essentially radial forces exerted by the capsular bag and transmitted to the equatorial region of the optic by the haptic. The haptic is stiffer than the optic. The haptic is coaxial with the optic. The haptic stresses the optic when the intraocular lens is in a natural state.
• A further embodiment is a method for manufacturing an intraocular lens having a haptic, comprising stressing the haptic under an external stress; placing an optic within the haptic; and removing the external stress from the haptic, so that at equilibrium, the optic is internally stressed.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a cross-section drawing of a human eye with an implanted intraocular lens, focused on a relatively close object.
• FIG. 2 is a cross-section drawing of a portion of a human eye with an implanted intraocular lens, focused on a relatively distant object.
• FIG. 3 is a flow chart of a manufacturing process that may induce an internal stress to the optic.
• FIG. 4 is an end-on drawing of a haptic and optic, shown throughout various stages of construction.
• FIG. 5 is an isometric drawing of the haptic and optic ofFIG. 4, only with the lens in the plane of the page and the optical axis of the lens being perpendicular to the page.
• FIG. 6 is an end-on drawing of a haptic and optic, shown throughout various stages of construction.
• FIG. 7 is an isometric drawing of the haptic and optic ofFIG. 5, only with the lens in the plane of the page and the optical axis of the lens being perpendicular to the page.
• FIG. 8 is a schematic drawing of an optic and a haptic under compression from an asymmetric external force.
• FIG. 9 is a schematic drawing of the haptic and optic ofFIG. 8 removed from the asymmetric external force.
• FIG. 10 is a flow chart of a manufacturing process that may induce an internal stress to the optic.
• FIG. 11 is an isometric drawing of an optic placed within a haptic.
• FIG. 12 is a cross-section drawing of a haptic.
• FIG. 13 is a cross-sectional drawing of the haptic ofFIG. 12, with an optic.
• FIG. 14 is the cross-section drawing of the haptic and optic ofFIG. 13, with additional hidden lines.
• FIG. 15 is an end-on cross-sectional drawing of the haptic and optic ofFIG. 13.
• FIG. 16 is a plan drawing of the haptic ofFIG. 12.
• FIG. 17 is a plan drawing of the haptic ofFIG. 16, with an optic.
• FIG. 18 is the cross-section drawing of the haptic and optic ofFIG. 17, with additional hidden lines.
• FIG. 19 is a plan drawing of a haptic.
• FIG. 20 is a plan drawing of the haptic ofFIG. 19, with an optic.
• FIG. 21 is the plan drawing of the haptic and optic ofFIG. 20, with additional hidden lines.
• FIG. 22 is a top-view plan drawing of a haptic with an optic.
• FIG. 23 is a side-view plan drawing of the haptic and optic ofFIG. 22.
• FIG. 24 is a side-view cross-sectional drawing of the haptic and optic ofFIG. 22.
• FIG. 25 is a plan drawing of the haptic and optic ofFIG. 22.
• FIG. 26 is a cross-sectional drawing of the haptic and optic ofFIG. 22.
DETAILED DESCRIPTION OF THE DRAWINGS
• In a healthy human eye, the natural lens is housed in a structure known as the capsular bag. The capsular bag is driven by a ciliary muscle and zonular fibers (also known as zonules) in the eye, which can compress and/or pull on the capsular bag to change its shape. The motions of the capsular bag distort the natural lens in order to change its power and/or the location of the lens, so that the eye can focus on objects at varying distances away from the eye in a process known as accommodation.
• For some people suffering from cataracts, the natural lens of the eye becomes clouded or opaque. If left untreated, the vision of the eye becomes degraded and blindness can occur in the eye. A standard treatment is surgery, during which the natural lens is broken up, removed, and replaced with a manufactured intraocular lens. Typically, the capsular bag is left intact in the eye, so that it may house the implanted intraocular lens.
• Because the capsular bag is capable of motion, initiated by the ciliary muscle and/or zonules, it is desirable that the implanted intraocular lens change its power and/or location in the eye in a manner similar to that of the natural lens. Such an accommodating lens may produce improved vision over a lens with a fixed power and location that does not accommodate.
• FIG. 1 shows ahuman eye10, after an accommodating intraocular lens has been implanted. Light enters from the left ofFIG. 1, and passes through thecornea11, theanterior chamber12, theiris13, and enters thecapsular bag14. Prior to surgery, the natural lens occupies essentially the entire interior of thecapsular bag14. After surgery, thecapsular bag14 houses the intraocular lens, in addition to a fluid that occupies the remaining volume and equalizes the pressure in the eye. The intraocular lens is described in more detail below. After passing through the intraocular lens, light exits theposterior wall15 of thecapsular bag14, passes through theposterior chamber24, and strikes theretina16, which detects the light and converts it to a signal transmitted through theoptic nerve17 to the brain.
• A well-corrected eye forms an image at theretina16. If the lens has too much or too little power, the image shifts axially along the optical axis away from the retina, toward or away from the lens. Note that the power required to focus on a close or near object is more than the power required to focus on a distant or far object. The difference between the “near” and “far” powers is known typically as the add power or the range of accommodation. A normal range of accommodation is about 3 to 4 diopters, which is considered sufficient for most patients.
• The capsular bag is acted upon by theciliary muscle25 via thezonules18, which distort thecapsular bag14 by stretching it radially in a relatively thick band about its equator. Experimentally, it is found that theciliary muscle25 and/or thezonules18 typically exert a total ocular force of up to about 10 grams of force, which is distributed generally uniformly around the equator of thecapsular bag14. Although the range of ocular force may vary from patient to patient, it should be noted that for each patient, the range of accommodation is limited by the total ocular force that can be exert. Therefore, it is highly desirable that the intraocular lens be configured to vary its power over the full range of accommodation, in response to this limited range of ocular forces. In other words, it is desirable to have a relatively large change in power for a relatively small driving force.
• Because the zonules' or ocular force is limited, it is desirable to use a fairly thin lens, compared to the full thickness of the capsular bag. In general, a thin lens may distort more easily than a very thick one, and may therefore convert the ocular force more efficiently into a change in power. In other words, for a relatively thin lens, a lower force is required to cover the full range of accommodation.
• Note that the lens may be designed so that its relaxed state is the “far” condition (sometimes referred to as “disaccommodative biased”, the “near” condition (“accommodative biased”), or some condition in between the two.
• The intraocular lens itself generally has two components, an optic21, which is made of a transparent, deformable and/or elastic material, and a haptic23, which holds the optic21 in place and mechanically transfers forces on thecapsular bag14 to the optic21. The haptic23 may have an engagement member with a central recess that is sized to receive the peripheral edge of the optic21.
• When theeye10 focuses on a relatively close object, as shown inFIG. 1, thezonules18 relax and compress thecapsular bag14 returns to its natural shape in which it is relatively thick at its center and has more steeply curved sides. As a result of this action, the power of the lens increases (i.e., one or both of the radii of curvature can decrease, and/or the lens can become thicker, and/or the lens may also move axially), placing the image of the relatively close object at theretina16. Note that if the lens could not accommodate, the image of the relatively close object would be located behind the retina, and would appear blurred.
• FIG. 2 shows a portion of aneye20 that is focused on a relatively distant object. Thecornea11 andanterior chamber12 are typically unaffected by accommodation, and are substantially identical to the corresponding elements inFIG. 1. To focus on the distant object, theciliary muscle37 contracts and thezonules26 retract and change the shape of thecapsular bag25, which becomes thinner at its center and has less steeply curved sides. This reduces the lens power by flattening (i.e., lengthening radii of curvature and/or thinning) the lens, placing the image of the relatively distant object at the retina (not shown).
• For both the “near” case ofFIG. 1 and the “far” case ofFIG. 2, the intraocular lens itself deforms and changes in response to the ciliary muscles and/or to the distortion of the capsular bag. For the “near” object, the haptic23 compresses the optic21 at its edge, increasing the thickness of the optic21 at its center and more steeply curving itsanterior face19 and/or itsposterior face22. As a result, the lens power increases. For the “far” object, the haptic30 expands, pulling on the optic28 at its edge, and thereby decreasing the thickness of the optic28 at its center and less steeply curving (e.g., lengthening one or both radius of curvature) itsanterior face27 and/or itsposterior face29. As a result, the lens power decreases.
• Note that the specific degrees of change in curvature of the anterior and posterior faces depend on the nominal curvatures. Although theoptics21 and28 are drawn as bi-convex, they may also be plano-convex, meniscus or other lens shapes. In all of these cases, the optic is compressed or expanded by forces applied by the haptic to the edge and/or faces of the optic. In addition, there may be some axial movement of the optic. In some embodiments, the haptic is configured to transfer the generally symmetric radial forces symmetrically to the optic to deform the optic in a spherically symmetric way. However, in alternate embodiments the haptic is configured non-uniformly (e.g., having different material properties, thickness, dimensions, spacing, angles or curvatures), to allow for non-uniform transfer of forces by the haptic to the optic. For example, this could be used to combat astigmatism, coma or other asymmetric aberrations of the eye/lens system. The optic may optionally have one or more diffractive elements, one or more multifocal elements, and/or one or more aspheric elements.
• In many cases, it is desirable that during accommodation, the distortion of the optic produces a change in optic thickness and/or a change in the radius of curvature of the anterior and/or posterior surfaces of the optic. Any other types of distortions to the surface, such as “ripples” or “waves”, may unacceptably degrade the optical performance of the lens. These “ripples” or “waves” are described in more detail below.
• Because the optic is round, it may be difficult to envision any undesirable surface ripples that may accompany a squeezing or expanding of the optic about its equator. For this reason, it is instructive to consider the geometry of a linear beam or rod, which can produce analogous ripples along a single dimension. This 1-D geometry is much simpler to visualize, and adequately describes the issue of undesirable surface distortion.
• Consider a linear beam or rod, which is being compressed by pushing on its ends. While the intended effect of the compression may be to shorten the beam and/or produce a slight bulge along the length of the beam, an unintended effect may be to cause a small amount of “buckling” along the length of the beam. Similarly, if the beam is stretched by pulling on its ends, the intended effect of the stretching may be to lengthen the beam and/or produce a slight thinning of the beam along its length, but an unintended effect may be to cause a small amount of “cracking” along the surface, similar in character to that of a desert floor. Both the “buckling” and “cracking” may occur along the surface of the beam, while the compression or expansion may be initiated at or near the ends of the beam.
• This analogy may be extended to the two-dimensional, essentially circular geometry of the accommodating optic. To focus on relatively near objects, as inFIG. 1, the haptic may squeeze the optic about its equator and cause a radial compression of the optic. The intended effect of the squeezing may be to increase the thickness of the optic and/or change the curvature of the anterior and/or posterior surfaces of the optic. However, an unintended effect may be to produce the two-dimensional, circular equivalent of “buckling” on one or both of these surfaces. Similarly, to focus on relatively distant objects, as inFIG. 2, the haptic may stretch the optic about its equator and cause a radial expansion of the optic. The intended effect of the expansion may be to decrease the thickness of the optic and/or change the curvature of the anterior and/or posterior surfaces of the optic. However, an unintended effect may be to produce the twos dimensional, circular equivalent of “cracking” on one or both of these surfaces. For the purposes of this document, the circular equivalents of “buckling” and “cracking” may be referred to as “ripples” or “waves”. For known optics, these “ripples” or “waves” may degrade the performance of the optic, which is highly undesirable.
• It is possible that the “ripples” or “waves” during accommodation may be avoided if the optic has internal stress. For instance, if the haptic applies a compression or expansion force to the optic, separate and distinct from any compression or expansion forces applied by the capsular bag of the eye, then the optic may have some internal stress, which may reduce any “ripples” or “waves” that appear during accommodation. The internal stress in the optic may be present throughout the range of accommodation, or may alternatively pass through “zero” at some point in the range of accommodation.
• In some embodiments, the anterior and/or posterior surfaces may be designed so that they attain particular profiles when the optic is compressed about its equator, as occurs when the lens is implanted. For instance, in some embodiments, it may be particularly desirable to have spherical anterior and/or posterior surfaces; in these embodiments, the anterior and/or posterior surface profiles may or may not deviate from spherical when the optic is uncompressed about its equator. In other words, for some embodiments, compressing the optic about its equator causes the anterior and/or posterior surfaces to become more spherical in profile. If there is asphericity in either surface in the uncompressed state, it may be reduced when the optic is compressed.
• FIG. 3 is a flow chart of amanufacturing process31 that may induce an internal stress to the optic when the intraocular lens is in a natual or nominally unstressed state.
• First, externally stress the haptic, as inelement32. In some embodiments, an external compressive or expansive force is applied to a haptic, so that the haptic becomes compressed or stretched. Note that the haptic may be made from a generally elastic material, so that the haptic may return roughly to its initial shape and size when the external force is removed.
• Next, place or form an optic within the externally stressed haptic, as inelement33. In some embodiments, the optic may be molded or otherwise manufactured directly onto the externally stressed haptic. In other embodiments, the optic may be manufactured separately, then attached to the haptic. For the purposes of this document, for all of these embodiments, the optic is said to be “placed” within the haptic.
• In some embodiments, the optic is held by the haptic in a region around the equator of the optic. The haptic may contact the optic at the edge of the optic, at the circumference of the anterior face of the optic, and/or at the circumference of the posterior face of the optic. The haptic may optionally extend over a portion of the anterior and/or posterior faces, typically around the edge of the optic and outside the clear aperture of the optic. In some embodiments, the haptic may not truly surround the optic, but may contact it in portions at or near the equator of the optic or may contact it only on the anterior or posterior face. In other embodiments, portions of the haptic may be disposed inside the optic so that the haptic portion protrudes into the optic. For the purposes of this document, the optic is said to be placed “within” the haptic for all of these orientations.
• Next, remove the external stress from the haptic, as inelement34. This may involve removing the external compressive or expansive force applied inelement32.
• The intraocular lens reaches a natural state, as in element35. For the purposes of this document, a “natural” state is a state of the intraocular lens in which there is an absence of external forces, such as external compressive or expansive forces applied inelement32. In some embodiments, the “natural” state is the state of the intraocular lens prior to implantation into an eye.
• Finally, the optic is internally stressed, as inelement36. In some embodiments where the haptic is stiffer than the optic, the haptic is generally relaxed and returns nearly to the size and shape it had before the external stress was applied, while the optic becomes stretched or compressed to maintain contact with the generally relaxed haptic. Note that in this generally relaxed state of the intraocular lens, the haptic may have some residual stresses that oppose the internal stresses of the optic; the magnitude of these residual stresses may vary inversely with the stiffness of the haptic. For typical haptics, which are much stiffer than the optic, the residual stresses are quite small, and the haptic may be considered to be essentially relaxed.
• For the purposes of this document, an intraocular lens and/or the optic contained therein in which a haptic uses its internal stress to affect the internal stress of the optic may be referred to as a “pre-stressed” intraocular lens and/or a “pre-stressed” optic.
• FIG. 4 is an end-on drawing of a haptic and optic, shown throughout various stages of construction. In this figure, the optical axis is vertical and the plane of the lens is horizontal.
• For the purposes of this figure and several of the following figures, the haptic is drawn as being essentially solid, and the optic is attached to the side of the haptic. It will be understood that in practice, the haptic may be hollow or cylindrical in nature, such as a circumferential ring, and may surround all or part of the optic around its equator and/or may at least partially protrude into the optic.
• Thetopmost element41 is a haptic in a natural, unstressed state, without an optic.
• The next element down is the haptic42 with an external stress applied. An external force, denoted by the shaded arrows at the left and right ofelement42, expands the haptic. The haptic increases in size, as shown by the dotted lines that indicate the unstressed size of the haptic. The haptic also has an internal stress, denoted by the solid arrows inside the haptic. In this case, the haptic is under tension.
• Still further down, an optic43 is placed within the stressed haptic44. Although the optic typically does not extend along the optical axis past the edges of the haptic, it is drawn as such inFIG. 4 for simplicity.
• At the bottom ofFIG. 4, the external force is removed from the haptic46. The haptic46 largely relaxes and returns nearly to its original, unstressed size, as shown by the pair of dotted lines at each end of the haptic46. The optic45, which is mechanically coupled to the haptic46 and is typically less stiff than the haptic46, provides little resistance to the change in size of the haptic. As a result, the optic45 becomes compressed and develops an internal stress, shown by the pair of solid arrows inside the optic45. In this case, the internal stress of the optic45 is compression. In other embodiments, the internal stress of the optic45 is stretched expansion.
• Note that the internal stress of the haptic46 is largely relieved by removing the external stress. However, there may be a small residual internal stress that remains inside the haptic46, which is denoted by the thin, solid arrows inside the haptic46. The magnitude of this residual stress may be proportional to the stiffness of the optic45; if the optic45 had no stiffness at all, there would be no residual stress, and the haptic46 would be completely relaxed and would return roughly to its unstressed size.
• FIG. 5 shows the haptic and optic ofFIG. 4, only with the lens in the plane of the page and the optical axis of the lens being perpendicular to the page.
• Element41 is the haptic in an unstressed state. For clarity, the dotted lines showing the unstressed size of the haptic are omitted.
• Element42 is the haptic with an external stress applied. In this case, the external stress is an expansion, and the haptic42 is under tension. In some embodiments, the external stress and tension are both radially symmetric.
• Element43 is the optic, placed within the stressed haptic44. At this stage, the optic43 is not under significant stress.
• The external stress is removed at the bottom ofFIG. 5, and the haptic46 andoptic45 are both seen to radially contract, causing an internal stress in the optic45. In this case, the internal stress in the optic45 is compression. At this stage, the lens may be ready for implantation.
• FIGS. 6 and 7 are analogous toFIGS. 4 and 5, but the external force applied to the haptic is compression rather than expansion. Note that combinations of compression and expansion are possible, with compression along one direction and expansion along another, although these are not shown in the figures.
• FIG. 6 is an end-on drawing of a haptic and optic, shown throughout various stages of construction. In this figure, the optical axis is vertical and the plane of the lens is horizontal.
• Thetopmost element61 is haptic in a natural, unstressed state, without an optic.
• The next element down is the haptic62 with an external stress applied. An external force, denoted by the shaded arrows at the left and right ofelement62, compresses the haptic. The haptic decreases in size, as shown by the dotted lines that indicate the unstressed size of the haptic. The haptic also has an internal stress, denoted by the solid arrows inside the haptic. In this case, the haptic is under compression.
• Still further down, an optic63 is placed within the stressed haptic64. Although the optic typically does not extend along the optical axis past the edges of the haptic, it is drawn as such inFIG. 6 for simplicity.
• At the bottom ofFIG. 6, the external force is removed from the haptic66. The haptic66 largely relaxes and returns nearly to its original, unstressed size, as shown by the pair of dotted lines at each end of the haptic66. The optic65, which is mechanically coupled to the haptic66 and is typically less stiff than the haptic66, provides little resistance to the change in size of the haptic. As a result, the optic65 becomes expanded and develops an internal stress, shown by the pair of solid arrows inside the optic65. In this case, the internal stress of the optic65 is tension.
• FIG. 7 shows the haptic and optic of FIG,5, only with the lens in the plane of the page and the optical axis of the lens being perpendicular to the page.
• Element61 is the haptic in an unstressed state. For clarity, the dotted lines showing the unstressed size of the haptic are omitted.
• Element62 is the haptic with an external stress applied. In this case, the external stress is a compression, and the haptic62 is under compression. In some embodiments, the external stress and compression are both radially symmetric.
• Element63 is the optic, placed within the stressed haptic64. At this stage, the optic63 is not under significant stress.
• The external stress is removed at the bottom ofFIG. 7, and the haptic66 andoptic65 are both seen to radially expand, causing an internal stress in the optic65. In this case, the internal stress in the optic65 is tension. At this stage, the lens may be ready for implantation.
• FIGS. 8 and 9 show a haptic81 andoptic82 analogous to those in the bottom portion ofFIG. 7, but with an asymmetric external force applied to the haptic81. Such an asymmetry may be used to reduce astigmatism in the optical system of an eye.
• InFIG. 8, a haptic81 is under compression from an asymmetric external force. InFIG. 8, the compressive force is larger in the vertical direction than in the horizontal direction, although in practice, the asymmetry may have any orientation and any degree of asymmetry. In addition, the asymmetry may optionally include a compressive force along one dimension and an expansive force along another. Alternatively, the asymmetry may include an expansive force along one dimension and an expansive force with a different magnitude along a different dimension.
• While under the external compression, the haptic81 is shown inFIG. 8 to be elliptical in shape, with a compressed size smaller than the uncompressed size denoted by the dashedline83. An optic82 is placed within the externally compressed haptic81. At this stage, the optic82 is largely unstressed.
• Once the optic is placed within the externally stressed haptic, the external stress is removed. The haptic91 andoptic92 then expand, as shown in FIG,9. The resulting tension within the optic92 may be radially asymmetric, with a direction-dependent tension that varies as a function of how much the haptic81 was externally compressed along the particular direction. InFIG. 9, the tension along the vertical direction is larger than along the horizontal direction. Note that the asymmetry stresses in the optic92 may have any orientation, and are not confined to vertical and horizontal, as shown inFIG. 9.
• Note that inFIGS. 4 though97 the haptic is stretched or compressed by an external force. In one embodiment, the external force is mechanical in origin, and may be realized by pushing or pulling on various locations on the haptic.
• Note also that for the typical circularly symmetric geometries of an intraocular lens, the stresses in the haptic and optic are generally radial in orientation and are generally coaxial with each other.
• In another embodiment, the pre-stress is caused by shrinkage or expansion of the materials during molding, extraction or another manufacturing or processing step. The haptic and the optic may be made from materials having different mechanical properties, so that during a shrinking or expanding step, one shrinks or expands more than the other. If the optic is placed within the haptic before the shrinking or expanding step, then the optic and/or haptic may become internally stressed after the shrinking or expanding step. Note that if the haptic is significantly stiffer than the optic, then the optic may have significantly more internal stress than the haptic after the shrinking or expanding step.
• FIG. 10 is a flow chart of anexemplary manufacturing process101 that may induce an internal stress to the optic. Initially, the haptic may be provided for the manufacturing process. In one embodiment, the haptic is externally stressed, where the external stress is to be removed at a later manufacturing step; this is analogous to the manufacturing process shown above inFIG. 3. In another embodiment, the haptic is essentially unstressed at this stage. Such an initially unstressed haptic may be made from a material that may expand or contract in response to a size-altering process, such as a heating, a cooling, or an absorption or emission of water or other substance.
• Inelement102, an optic is placed within the haptic. In one embodiment, the optic may be molded onto or around the haptic. In another embodiment, the optic may be manufactured separately from the haptic and then attached to the haptic. The optic may be attached to the interior of the haptic, or may be attached to the exterior of the haptic. The haptic may surround all or part of the optic, or may be adjacent to the optic. In all of these cases, the optic is said to be “placed within” the haptic.
• Inelement103, stress is induced between the haptic and the optic. The stress may be induced by changing the size and/or shape of the haptic and/or the optic, once the optic has been placed within the haptic. As long as the haptic and optic expand or contract by different amounts, there will be a stress between the haptic and the optic. For instance, the haptic may expand and the optic may contract, remain the same size, or expand by amount different from that of the haptic. Alternatively, the haptic may contract and the optic may expand, remain the same size, or contract by amount different from that of the haptic. As a further alternative, the haptic may remain the same size and the optic may contract or expand.
• Because the haptic and the optic may be connected afterelement102 inFIG. 10, the haptic and optic may not be able to expand or contract free of each other. For instance, if the haptic surrounds the optic so that the outer diameter of the optic fits inside the inner diameter of the haptic, the optic may not expand significantly compared to what its expansion would be if it were not mounted within the haptic. In this case, an expansion of the optic by heating or another method may not produce a significant expansion of the optic, but may produce compression within the optic. For this reason, the expansion and/or contraction described above may be considered to be an expansion and/or contraction in free space, as if the haptic were detached from the optic.
• Inelement104, the haptic and the optic reach a natural state, analogous to element35 inFIG. 3. Inelement105, the optic is internally stressed, analogous toelement36 inFIG. 3.
• In one embodiment, the expansion and/or contraction may be caused by a shrinking and/or expanding step that occurs during molding, extraction or any other manufacturing or processing step. For instance, if the haptic has a higher shrinkage than the optic, and the optic is placed within the haptic before a shrinking step, then the optic may be in a compressed state after the shrinking step. Similarly, if the haptic has a lower shrinkage than the optic, and the optic is placed within the haptic before a shrinking step, then the optic may be in an expanded state after the shrinking step.
• In another embodiment, the pre-stress is caused by using hydrophilic and/or hydrophobic materials for the haptic and/or optic. Upon insertion into the aqueous solution of the eye, a hydrophilic material may swell and a hydrophobic material may shrink or remain the same size. The swelling and/or shrinking upon insertion into the eye is analogous to the expanding and/or shrinking steps described above.
• For instance, consider a hydrophilic optic placed within a hydrophobic haptic. Upon insertion into the aqueous solution of the eye, the optic may swell and the haptic may absorb some of the swelling force. The lens may then reach an equilibrium in the eye, in which the optic may be under compression.
• In one embodiment, the haptic and optic may have different levels of hydrophilia and/or hydrophobia, so that upon insertion into the eye they may swell at different rates and may therefore internally stress the optic.
• As noted inFIGS. 8 and 9, the haptic may be pre-stressed differently in different directions. In addition, the haptic may also have an axial component to the pre-stressing. This axial component may help dampen or eliminate any undesirable axial movement of the lens during accommodation.
• BecauseFIGS. 4 though9 are largely schematic in nature, it is instructive to consider a haptic having a more realistic design.
• FIG. 11 is an isometric drawing of an exemplary haptic, after manufacture and prior to installation in the eye. The optic, when placed within the haptic, will be located at or near the center of the haptic. The haptic may protrude into the optic. Alternatively, the haptic may engage all or a portion of the periphery of the optic only. The outer circumference of the haptic mechanically couples with the capsular bag of the eye (not shown), so that any compression or expansion initiated by the zonules is coupled into the haptic, and, in turn, into the optic through its periphery.
• The exemplary haptic has various segments or filaments, each of which extends generally radially in a plane roughly perpendicular to the optical axis of the lens. For the exemplary haptic ofFIG. 11 the segments are joined to each other at the outer circumference and extend radially inward until they contact the edge of the optic. Alternatively, they need not be joined together at the outer circumference. At locations other than the outer circumference, the haptic segments may remain separate from each other, as shown inFIG. 11, or alternatively some or all segments may be joined together. Any or all of the width, shape and thickness of the segments may optionally vary along the length of the segments. The haptic may have any suitable number of segments, including but not limited to, 3, 4, 6, 8, 10, 12, 14, and 16.
• The exemplary haptic110 is then compressed radially, so that the overall diameter of the haptic is reduced. A typical compression may be on the order of about 1 mm, although more or less compression may be used. For instance, the haptic may be compressed by a fraction of its diameter, such as a value in the range of about 0.4% to about 2.0%. This compressed state may be referred to as a “pre-stressed” state.
• FIG. 11 is an isometric drawing of an optic111 placed within a haptic112. The haptic112 engages a portion of the periphery of the optic111 in a region roughly around theequator115 of the optic111. This exemplary haptic112 contacts the optic111 in four regions, each roughly equally spaced apart around theequator115 of the optic111, although any suitable number of contact portions may be used and they need not be spaced equally apart. The haptic112 includes an annular ring, also known as a circumferential ring. The ring has an inner diameter given byelement113, and an outer diameter given byelement114. The ratio of the inner to out diameters may vary as a function of the stiffness of the haptic112. For instance, a stiffer haptic may require relatively little material, and the ratio may be fairly close to 1. Alternatively, a less stiff haptic may require more material, and the ratio may deviate significantly from 1.
• For the haptic shown inFIG. 11, theouter diameter116 of the annular ring is the outer portion of the haptic112, and may remain in contact with the capsular bag of the eye during and after implantation. Alternatively, the annular ring may be contained in the interior of the haptic, with arms or filaments that may extend outward beyond the outer diameter of the annular ring to contact the capsular bag; these filaments are analogous to the four inward-extending filaments shown inFIG. 11. As a further alternative, the inner diameter of the annular ring may be the inner diameter of the haptic, and may contact the circumference or the equator of the optic.
• FIGS. 12 through 18 show an exemplary haptic120 in various plan and cross-sectional views, both with and without an optic130.FIG. 12 is a cross-section drawing of a haptic120.FIG. 13 is a cross-sectional drawing of the haptic ofFIG. 12, with an optic130.FIG. 14 is the cross-section drawing of the haptic120 andoptic130 ofFIG. 13, with additional hidden lines.FIG. 15 is an end-on cross-sectional drawing of the haptic120 andoptic130 ofFIG. 13.FIG. 16 is a plan drawing of the haptic120 ofFIG. 12.FIG. 17 is a plan drawing of the haptic120 ofFIG. 16, with an optic130.FIG. 18 is the cross-section drawing of the haptic120 andoptic130 ofFIG. 17, with additional hidden lines.
• The haptic120 ofFIGS. 12 through 18 has eight filaments denoted byelements121athrough121h. Alternatively, the haptic120 may have more or fewer than eight filaments. The filaments121a-hmay be connected at their outermost edge and may be unconnected at their innermost edge.
• Note that the filaments121a-hmay vary in size along their lengths, from theinnermost edge123 to the ends of the filament adjacent to theoutermost edge122 of the haptic120. In particular, the filaments12la-hmay increase in cross-sectional dimensions with radial distance away from the center of the lens. In a direction parallel to the optical axis (vertical inFIG. 12), the outermost extent of the haptic filaments, denoted bylength129, may be larger than the innermost extent of the haptic filaments, denoted bydimension128. Alternatively, thelength129 may be equal to or less thanlength128. Simlarly, in a direction perpendicular to the optical axis (essentially in the plane of the lens), the filaments may be effectively wedge-shaped, with a greater radial extent at the outer edge than at the inner edge. The cross-section of each filament may be symmetric with respect to the plane of the lens, as shown inFIG. 12. Alternatively, the cross-section of one or more filaments may be asymmetric with respect to the plane of the lens, with differing amounts of material on anterior and posterior sides of the filament.
• Theoutermost edge122 of the haptic120 mechanically couples the intraocular lens to the capsular bag of the eye. The haptic120 may receive an optic130 in its central region, which may be molded directly onto the haptic120. Alternatively, the optic may be manufactured separately from the haptic, then attached to the haptic.
• The haptic120 may have an optional lip orridge124 on one or both of the anterior and posterior faces, so that if an optic is molded directly onto the haptic120, the optic resides in the central portion of the haptic within thelip124. Thelip124 may be circularly symmetric on both faces of the haptic, as shown inFIGS. 12 through 18. Alternatively, thelip124 may have a different radius on one or more filaments, so that optic material may extend out different radial distances along particular filaments. As a further alternative, thelip124 may have different radii on the anterior and posterior faces of the haptic120.
• Once the optic130 is formed on, attached to, or placed within the haptic120, the haptic120 protrudes into theedge131 of the optic130. For the specific design ofFIGS. 12 through 18, portions of each filament12la-hextend into theedge131 of the optic130, with the anterior and posterior faces of the optic130 surrounding and/or encompassing the haptic filaments121a-hin the central portion demarcated by thelip124.
• For a cross-section of the filaments12la-h, taken in a plane parallel to the optical axis of the lens (vertical inFIGS. 12 through 18), the cross-section has a particular profile that extends into theedge131 of the optic130. The profile may contain one or more straight and/or curved portions, and may have a deepest portion at one or more points or along a straight segment. For instance, the profile inFIGS. 12 and 15 has a generallystraight portion125 extending generally radially inward, followed by a generallystraight portion126 extending generally parallel to the optical axis, followed by a generallystraight portion127 extending generally radially outward. The generallystraight portions125,126 and127 may optionally have one or morerounded portions151 between them.Straight portions125 and127 may be generally parallel to each other, or may be generally inclined with respect to each other. The generallystraight portion126 may be generally parallel to the optical axis, as inFIGS. 12 and 15, or may alternatively be inclined with respect to the optical axis. The deepest portion of the profile ofFIGS. 12 and 15 may be thestraight portion126. The profile made up ofsegments125,126 and127 shown inFIGS. 12 and 15 may be generally convex in a direction parallel to the optical axis of the lens. Other configurations of protruding haptics may incorporated into embodiments of the present invention such, for examples, those discussed in copending U.S. patent application Ser. No. 11/618,325, which is herein incorporated by reference.
• Referring toFIG. 15, the axial thickness (i.e., along an axis parallel to the optical axis passing through the center of the optic130) of the portions of the haptic120 disposed within the optic130 may be selected to control the amount and/or distribution of an ocular force acting on the intraocular lens240. For example, in some embodiments, the performance (e.g., the change Diopter power of the optic130 between accommodative and disaccommodative configurations) increases as the edge thickness increases. In such embodiments, other design constraints (e.g., optical performance or physical constraints of the eye) may, however, place an upper limit on the maximum optic edge thickness. In some embodiments, the portion of the haptic120 inside the optic130 has a maximum axial thickness that is at least one half a maximum axial thickness of the optic130 along the optical axis, as clearly illustrated inFIG. 15. In other embodiments, the portion of the haptic120 inside the optic130 has a maximum axial thickness that is at least75% of a maximum axial thickness of the central zone. The advantages of the axial thickness the protruding portions of the haptic120 may also be applied to other embodiments of the invention discussed herein.
• In certain embodiments, the optic130 is a multifocal optic. For example, the portion of the optic130 between theends126 of the haptic120 may comprise a first zone having a first optical power and the portion of the optic130 into which the filaments121 protrude may comprise a second zone having a second optic power that is different from the first optical power. In some embodiments, the optic130 may change from a monofocal optic to a multifocal optic, depending upon the amount of ocular force on the haptic120 and/or the state of accommodation of the eye into which the intraocular lens is inserted.
• If the optic130 may be molded directly onto the haptic120, the haptic120 may be first expanded or contracted radially by an external force, prior to molding. The optic130 may then be molded directly onto the expanded or contracted haptic120. After molding, the external force may be removed, and the haptic may return to its original size or fairly close to its original size, forming radial stresses within theoptic130.
• It is desirable that the haptic be made from a stiffer material than the optic, so that any distorting forces induced by the zonules or capsular bag are transmitted efficiently through the haptic to the optic, and efficiently change the shape of the optic. It is also desirable that the haptic and the optic have similar or essentially equal refractive indices, which would reduce any reflections at the interfaces between the haptic and the optic.
• FIGS. 19 through 21 show another exemplary haptic190 in various plan views, both with and without an optic200.FIG. 19 is a plan drawing of a haptic190.FIG. 20 is a plan drawing of the haptic190 ofFIG. 19, with an optic200.FIG. 21 is the plan drawing of the haptic190 andoptic200 ofFIG. 20, with additional hidden lines.
• The haptic190 ofFIGS. 19 through 21 has eight filaments denoted byelements191athrough191h. Alternatively, the haptic190 may have more or fewer than eight filaments. Filaments19la-hmay have non-uniformities along their lengths, such as width variations, height variations, and/or holes192a-h.
• The holes192a-hmay desirably alter the mechanical properties of the respective filaments, so that a given zonular force may be transmitted efficiently into a distortion of the optic. The holes192a-hmay be triangular in shape, or may be any other suitable shape, such as round, square, rectangular, polygonal, and may optionally have one or more rounded corners and/or edges. Each hole may optionally vary in profile along its depth. There may optionally be more than one hole per filament. There may optionally be differing numbers of holes for different filaments. There may optionally be differently-shaped holes on the same filament.
• Unlike the filaments121a-hofFIGS. 12 through 18, the filaments191a-hare connected at both their outermost edge and their innermost edge. The filaments19la-hare joined at an outerannular ring193 and an innerannular ring194. The innerannular ring194 may lie within the circumference of the optic200, as inFIGS. 19 through 21. Alternatively, the innerannular ring194 may lie outside the circumference of the optic200, or may straddle the circumference of the optic200.
• The dimensions of the innerannular ring194, specifically, the inner and outer diameters of the innerannular ring194, may be determined in part by the stiffness of the haptic190 and/or the stiffness of the optic200. For instance, a stiffer haptic may require relatively little material, and the ratio may be fairly close to 1. Alternatively, a less stiff haptic may require more material, and the ratio may deviate significantly from 1.
• FIGS. 22 through 26 show another exemplary haptic220 in various plan views, with an optic230.FIG. 22 is a top-view plan drawing of a haptic220 with an optic230. FIG,23 is a side-view plan drawing of the haptic220 andoptic230 ofFIG. 22.FIG. 24 is a side-view cross-sectional drawing of the haptic220 andoptic230 ofFIG. 22.FIG. 25 is a plan drawing of the haptic220 andoptic230 ofFIG. 22.FIG. 26 is a cross-sectional drawing of the haptic220 andoptic230 of FIG,22.
• The haptic220 ofFIGS. 22 through 26 has a more complex shape than the haptics shown inFIGS. 12 through 21. The haptic220 has eight filaments221a-h, each of which has one end attached to an innerannular ring222 and has the opposite end attached to an outerannular ring223. Alternatively, the haptic220 may have more or fewer than eight filaments. In contrast with the haptics ofFIGS. 12 through 21 the haptic220 contacts the capsular bag of the eye at one or more points along the filaments221a-hbetween the inner and outerannular rings222 and223. In some embodiments, the filaments22la-hmay loop back on themselves, and may contact the capsular bag at one or more extrema along the loop, rather than at the outerannular ring223.
• As with the innerannular ring194 ofFIGS. 19 through 21, the innerannular ring222 may lie inside the circumference of the optic230, once the optic230 is placed within the haptic220, may lie outside the circumference of the optic230, or may straddle the circumference of the optic230.
• In some embodiments, such as the disc-shaped intraocular lenses shown inFIGS. 12 through 21, the haptic filaments engage an equatorial region of the capsular bag. In many of these embodiments, the optical power of intraocular lens may be selected to provide a disaccommodative bias, although some embodiments may alternatively provide an accommodative bias.
• In other embodiments, the haptic filaments may engage substantially the entire capsular bag, rather than just the equatorial region of the capsular bag. In some of these embodiments, the filaments may extend generally in a plane that includes the optical axis of the lens, and there may be uncontacted portions of the capsular bag in the regions between the filaments. In many of these embodiments, the intraocular lens has an accommodative bias, although some embodiments may alternatively use a disaccommodative bias.
• For the designs ofFIGS. 12 through 26, the haptic may be pre-stressed, and the optic may then be molded onto or attached to the haptic while the haptic is in the pre-stressed state. For instance, the haptic may be compressed or expanded radially prior to placing the optic within the haptic. The pre-stress may then be removed, and the lens may be allowed to relax to its substantially unstressed state, or a “natural” state. For a haptic that is much stiffer than the optic, the haptic may expand/contract by nearly the full compression/expansion amount, and the optic becomes expanded/compressed about its equator. In its expanded state, the optic is under radial tension.
• This pre-stress may help reduce or eliminate buckling of the optic, if the optic is compressed. It may also reduce the need for a thicker optic for maximizing the power change for a given external force (e.g., an ocular force produced by the ciliary muscles, the zonules, and/or the capsular bag of the eye.) Furthermore, the pre-stress may allow for a so-called “fail-safe” design that allows only a certain amount of power change during accommodation; the lens may minimize the power change beyond a prescribed accommodation range. In addition, the pres-stress may reduce the amount of force required for a given power change.
• The optic may be made from a relatively soft material, so that it can distort or change shape readily under the limited deforming force initiated by the capsular bag and transmitted through the haptic. An exemplary material is a relatively soft silicone material, although other suitable materials may be used as well. The stiffness of the optic121 may be less than 500 kPa, or preferably may be between 0.5 kPa and 500 kPa, or more preferably may be between 25 kPa and 200 kPa, or even more preferably may be between 25 kPa and 50 kPa.
• In contrast with the optic, the haptic may be made from a relatively stiff material, so that it can efficiently transmit the deforming forces from the capsular bag to the optic. An exemplary material is a relatively stiff silicone material, although other suitable materials may be used as well, such as acrylic, polystyrene, or clear polyurethanes. The haptic may preferably be stiffer than the optic. The stiffness of the haptic may be greater than 500 kPa, or preferably may be greater than 3000 kPa.
• Because the haptic may extend into the optic in a region around its circumference, it also may extend into the clear aperture of the optic. For this reason, the haptic may preferably be transparent or nearly transparent, so that it does not substantially block any light transmitted through the lens. The haptic generally has a power transmission of at least about 80%, preferably at least 90% or even 95%.
• In addition, it is desirable that the interface between the optic and the haptic not produce any significant reflections, which would produce scattered light within the eye, and would appear as a haze to the patient. A convenient way to reduce the reflections from the interface is to match the refractive indices of the haptic and the optic to each other.
• A simple numerical example shows the effect of mismatch of refractive indices on reflected power. For a planar interface at normal incidence between air (refractive index of 1) and glass (refractive index of 1.5), 4% of the incident power is reflected at the interface. For such an interface between air and glass, there is no attempt to match refractive indices, and this 4% reflection will merely provide a baseline for comparison. If, instead of 1 and 1.5, the refractive indices differ by 4%, such as 1.5 and 1.56 or 1.5 and 1.44, there is a 0.04% reflection, or a factor of 100 improvement over air/glass. Finally, if the refractive indices differ by only 0.3%, such as 1.5 and 1.505 or 1.5 and 1.495, there is a 0.00028% reflection, or a factor of over 14000 improvement over air/glass. In practice, tolerances such as the 0.3% case may be achievable, and it is seen that a negligible fraction of power may be reflected at the interface between a haptic and an optic whose refractive indices differ by 0.3%. Note that the above base value of 1.5 was chosen for simplicity, and that the haptic and optic may have any suitable refractive index.
• It is desirable that the refractive indices of the haptic and optic be essentially the same. For the purposes of this document, “essentially the same” may mean that their refractive indices are equal to each other at a wavelength within the visible spectrum (i.e., between 400 nm and 700 nm). Note that the haptic and optic may optionally have different dispersions, where the refractive index variation, as a function of wavelength, may be different for the haptic and the optic. In other words, if the refractive indices of the haptic and optic are plotted as a function of wavelength, they may or may not have different slopes, and if the two curves cross at one or more wavelengths between 400 nm and 700 nm, then the refractive indices may be considered to be essentially the same or essentially equal.
• The description of the invention and its applications as set forth herein is illustrative and is not intended to limit the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and practical alternatives to and equivalents of the various elements of the embodiments would be understood to those of ordinary skill in the art upon study of this patent document. These and other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims (36)

1. An intraocular lens for implantation into a capsular hag of an eye, comprising:

a stressed optic, and

a haptic for coupling the optic to the capsular bag;

wherein the haptic stresses the stressed optic when the intraocular lens is in a natural state.

2. The intraocular lens ofclaim 1, wherein the stressed optic is under tension and the haptic is under compression when the intraocular lens is in a natural state.

3. The intraocular lens ofclaim 2, wherein the tension of the stressed optic and the compression of the haptic are radial and coaxial.

4. The intraocular lens ofclaim 1, wherein the stressed optic is under compression and the haptic is under tension when the intraocular lens is in a natural state.

5. The intraocular lens ofclaim 4, wherein the compression of the stressed optic and the tension of the haptic are radial and coaxial.

6. An intraocular lens for implantation into a capsular bag of an eye, comprising:

an optic; and

a haptic for coupling the optic to the capsular bag;

wherein the optic is under tension when the intraocular lens is in a natural state.

7. The intraocular lens ofclaim 6, wherein the haptic is under compression when the intraocular lens is in a natural state.

8. The intraocular lens ofclaim 7, wherein the tension in the optic and the compression in the haptic are radial and coaxial.

9. An intraocular lens for implantation into a capsular bag of an eye, comprising,

an optic having a periphery; and

an annular ring engaging at least a portion of the periphery of the optic for coupling the optic to the capsular bag;

wherein the annular ring stresses the optic in the absence of an external compressive force on the annular ring.

10. The intraocular lens ofclaim 9, wherein the stress on the optic is tension.

11. The intraocular lens ofclaim 9, wherein the stress on the optic is radial.

12. The intraocular lens ofclaim 9, wherein the annular ring has an inner radius and an outer radius, the inner and outer radii being in a ratio that relates to a stiffness of the haptic.

13. An intraocular lens for implantation into a capsular bag of an eye, comprising:

an optic having a periphery; and

an annular ring engaging at least a portion of the periphery of the optic for coupling the optic to the capsular bag;

wherein the optic has a uncompressed surface profile in the absence of an external compressive force on the annular ring;

wherein the optic has a compressed surface profile in the presence of an external compressive force on the annular ring; and

wherein the compressed surface profile is more spherical than the uncompressed surface profile.

14. An intraocular lens for implantation into a capsular bag of an eye, comprising.

an optic having an equatorial region and a shape, the shape comprising an anterior curvature and a posterior curvature; and

a haptic for coupling the optic to the capsular bag;

wherein the optic can change its shape in response to essentially radial forces exerted by the capsular bag and transmitted to the equatorial region of the optic by the haptic;

wherein the haptic is stiffer than the optic;

wherein the haptic is coaxial with the optic; and

wherein the haptic stresses the optic when the intraocular lens is in a natural state.

15. The intraocular lens ofclaim 14, wherein the haptic produces tension in the optic when the intraocular lens is in a natural state.

16. The intraocular lens ofclaim 15, wherein the tension in the optic is radially symmetric.

17. The intraocular lens ofclaim 15, wherein the tension in the optic is radially asymmetric.

18. The intraocular lens ofclaim 14, wherein the haptic protrudes into the optic.

19. The intraocular lens ofclaim 14, wherein the haptic comprises a circumferential ring.

20. The intraocular lens ofclaim 19, wherein the circumferential ring of the haptic is disposed within the circumference of the optic.

21. The intraocular lens ofclaim 14, wherein the haptic essentially fills the capsular bag of the eye.

22. The intraocular lens ofclaim 21, wherein the optic is disaccommodatively biased.

23. The intraocular lens ofclaim 14, wherein the optic and haptic are both transparent.

24. The intraocular lens ofclaim 14, wherein the optic and haptic have essentially equal refractive indices.

25. The intraocular lens ofclaim 14, wherein the optic is made from silicone.

26. The intraocular lens ofclaim 14, wherein the haptic is made from silicone.

27. A method for manufacturing an intraocular lens having a haptic, comprising:

stressing the haptic under an external stress;

placing an optic within the haptic; and

removing the external stress from the haptic,

so that at equilibrium, the optic is internally stressed.

28. The method ofclaim 27, wherein the stressing step comprises compressing the haptic.

29. The method ofclaim 27, wherein the stressing step comprises tensing the haptic.

30. The method ofclaim 27, wherein the stressing step comprises stressing the haptic under a largely radial external stress.

31. The method ofclaim 27, wherein the stressing step comprises stressing the haptic under a non-symmetric external stress.

32. The method ofclaim 27, further comprising changing the diameter of the haptic between about 0.4% and about 2.0%.

33. The method ofclaim 27, wherein the placing step comprises molding the optic directly onto the haptic.

34. The method ofclaim 27, wherein the placing step comprises attaching a pre-formed optic to the haptic.

35. The method ofclaim 27, further comprising supporting the optic around an equator of the optic.

36. The method ofclaim 27, further comprising producing an internal stress in the optic.

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