Patent Grant
7247168
The present invention relates to intraocular lenses (“IOLs”) having optical parameters that are changeable in-situ. More particularly, the invention has application in IOLs for in-capsule implantation for cataract patients, wherein movement of the ciliary muscles induces transfer of fluid media within the interior of the IOL, thereby altering an optical power of the lens to provide accommodation.
Cataracts are a major cause of blindness in the world and the most prevalent ocular disease. Visual disability from cataracts accounts for more than 8 million physician office visits per year. When the disability from cataracts affects or alters an individual's activities of daily living, surgical lens removal with intraocular lens (IOL) implantation is the preferred method of treating the functional limitations. In the United States, about 2.5 million cataract surgical procedures are performed annually, making it the most common surgery for Americans over the age of 65. About 97 percent of cataract surgery patients receive intraocular lens implants, with the annual costs for cataract surgery and associated care in the United States being upwards of $4 billion.
A cataract is any opacity of a patient's lens, whether it is a localized opacity or a diffuse general loss of transparency. To be clinically significant, however, the cataract must cause a significant reduction in visual acuity or a functional impairment. A cataract occurs as a result of aging or secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, or radiation. Age related cataract conditions are the most common.
In treating a cataract, the surgeon removes the crystalline lens matrix from the lens capsule and replaces it with an intraocular lens (“IOL”) implant. The typical IOL provides a selected focal length that allows the patient to have fairly good distance vision. Since the lens can no longer accommodate, however, the patient typically needs glasses for reading.
More specifically, the imaging properties of the human eye are facilitated by several optical interfaces. A healthy youthful human eye has a total power of approximately 59 diopters, with the anterior surface of the cornea (e.g. the exterior surface, including the tear layer) providing about 48 diopters of power, while the posterior surface provides about −4 diopters. The crystalline lens, which is situated posterior of the pupil in a transparent elastic capsule supported by the ciliary muscles, provides about 15 diopters of power, and also performs the critical function of focusing images upon the retina. This focusing ability, referred to as “accommodation,” enables imaging of objects at various distances.
The power of the lens in a youthful eye can be adjusted from 15 diopters to about 29 diopters by adjusting the shape of the lens from a moderately convex shape to a highly convex shape. The mechanism generally accepted to cause this adjustment is that ciliary muscles supporting the capsule (and the lens contained therein), move between a relaxed state (corresponding to the moderately convex shape) and a contracted state (corresponding to the highly convex shape). Because the lens itself is composed of viscous, gelatinous transparent fibers, arranged in an “onion-like” layered structure, forces applied to the capsule by the ciliary muscles cause the lens to change shape.
Isolated from the eye, the relaxed capsule and lens take on a spherical shape. Within the eye, however, the capsule is connected around its circumference by approximately 70 tiny ligament fibers to the ciliary muscles, which in turn are attached to an inner surface of the eyeball. The ciliary muscles that support the lens and capsule therefore are believed to act in a sphincter-muscular mode. Accordingly, when the ciliary muscles are relaxed, the capsule and lens are pulled about the circumference to a larger diameter, thereby flattening the lens, whereas when the ciliary muscles are contracted the lens and capsule relax somewhat and assume a smaller diameter that approaches a more spherical shape.
As noted above, the youthful eye has approximately 14 diopters of accommodation. As a person ages, the lens hardens and becomes less elastic, so that by about age 45–50, accommodation is reduced to about 2 diopters. At a later age the lens may be considered to be non-accommodating, a condition known as “presbyopia”. Because the imaging distance is fixed, presbyopia typically entails the need for bi-focals to facilitate near and far vision.
Apart from age-related loss of accommodation ability, such loss is innate to the placement of IOLs for the treatment of cataracts. IOLs are generally single element lenses made from a suitable polymer material, such as acrylics or silicones. After placement, accommodation is no longer possible, although this ability is typically already lost for persons receiving an IOL. There is significant need to provide for accommodation in IOL products so that IOL recipients will have accommodating ability.
Although previously known workers in the field of accommodating IOLs have made some progress, the relative complexity of the methods and apparatus developed to date have prevented widespread commercialization of such devices. Previously known these devices have proved too complex to be practical to construct or have achieved only limited success, due to the inability to provide accommodation of more than 1–2 diopters.
U.S. Pat. No. 5,443,506 to Garabet describes an accommodating fluid-filled lens wherein electrical potentials generated by contraction of the ciliary muscles cause changes in the index of refraction of fluid carried within a central optic portion. U.S. Pat. No. 4,816,031 to Pfoff discloses an IOL with a hard PMMA lens separated by a single chamber from a flexible thin lens layer that uses microfluid pumps to vary a volume of fluid between the PMMA lens portion and the thin layer portion and provide accommodation. U.S. Pat. No. 4,932,966 to Christie et al. discloses an intraocular lens comprising a thin flexible layer sealed along its periphery to a support layer, wherein forces applied to fluid reservoirs in the haptics vary a volume of fluid between the layers to provide accommodation.
Although fluid-actuated mechanisms such as described in the aforementioned patents have been investigated, currently available accommodating lenses, such as developed by Eyeonics, Inc. (formerly C&C Vision, Inc.) of Aliso Viejo, Calif., employ a substantially rigid frame configured to vault posteriorly responsive to ciliary muscle contraction, thereby moving the optic towards or away from the retina to adjust the focus of the device.
In view of the foregoing, it would be desirable to provide apparatus and methods that restore appropriate optical focusing power action to the human eye.
It further would be desirable to provide methods and apparatus wherein a dynamic lens surface may be effectively manipulated responsive to movements of the ciliary muscles.
It still further would be desirable to provide methods and apparatus that utilize forces arising due to natural accommodating muscular action to induce deflection of an optical surface of the IOL. In particular, it would be desirable to provide an IOL in which muscle movements result in the application of, or removal of, forces to the IOL so as to operate one or more actuators to cause deflection of the dynamic surface.
In view of the foregoing, it is an object of the present invention to provide apparatus and methods that restore appropriate optical focusing power action to the human eye.
It is a further object of this invention to provide methods and apparatus wherein a dynamic lens surface may be effectively manipulated responsive to movement of the ciliary muscles.
It is another object of the present invention to provide methods and apparatus that utilize forces arising due to natural accommodating muscular action to induce deflection of an optical surface of the IOL.
It is a further object of this invention to provide methods and apparatus for reversibly communicating forces arising due to muscle movement to a dynamic surface via one or more actuators, thereby altering the optical parameters of one of more surfaces of the IOL.
These and other objects of the present invention are accomplished by providing an intraocular lens responsive to forces communicated from the ciliary muscles through the capsular bag to operate one or more actuators disposed within the IOL. The actuator is coupled to a dynamic surface of the IOL to deflect the dynamic surface, e.g., from a moderately convex to a highly convex shape, responsive to operation of the one or more actuators. In accordance with the principles of the present invention, the IOL includes at least one fluid-mediated actuator coupled to a fluid column disposed in at least one haptic of the IOL. Forces applied to the haptic by the capsular bag, responsive to movement of the ciliary muscles, cause the transfer of fluid between the fluid column and the actuator, which in turn deflects a dynamic surface of the lens.
In a preferred embodiment, the intraocular lens comprises an optic portion and a haptic (or non-optic) portion. The optic portion comprises a light transmissive substrate defining one or more fluid channels, at least one actuator coupled in fluid communication with the fluid channels, and anterior and posterior lens elements. One of the anterior and posterior lens elements includes a dynamic surface that is operatively coupled to the actuator to cause deflection of the dynamic surface. The other of the anterior or posterior lens elements may be coupled to the substrate or integrally formed therewith.
The haptic portion is disposed at the periphery of the optic portion and comprises one or more haptics that extend outward from the optic portion, each haptic including a fluid channel coupled in fluid communication with a fluid channel in the optic portion. In accordance with one aspect of the present invention, the haptics have a cross-sectional configuration selected so that the internal volume of the haptic is small in an unstressed state. The unstressed state is selected to correspond to the accommodated state of the eye, when the ciliary muscles are contracted and lateral forces applied by the capsular bag to the haptics are minimal. When the ciliary muscles relax, the zonules pull the capsular bag taut and apply forces to the lateral faces of the haptic. These forces cause the cross-sectional area of the haptic to increase and increase the internal volume of the haptic. This action in turn causes fluid to be withdrawn from the actuator disposed in the optic portion, so that the dynamic surface of the IOL transitions from an accommodated state to an unaccommodated state.
For such an embodiment, the actuator used in the optic portion of the IOL may comprise a bellows centrally located within the optic portion that, when filled with fluid, biases the dynamic surface of the IOL to the accommodated state. When the ciliary muscles are contracted, the zonules and capsular bag remain loose, and the haptics are unstressed. Relaxation of the ciliary muscle causes the zonules to transition the capsule to an ellipsoidal shape, which applies compressive forces to the haptic, thereby withdrawing fluid from the actuator and causing the lens to transition to the unaccommodated state. Alternatively, the actuator may comprise bellows-shaped structures disposed at the periphery of the optic portion, so as to minimize refractive effects and optical aberrations in the optic portion.
In an alternative embodiment, the haptic portion comprises one or more haptics having maximal internal volume in the unstressed state, wherein the internal volume of the haptic decreases when compressive forces are applied to the lateral faces of the haptic. In this case, compression of the haptic causes fluid to be transferred into the actuator when the ciliary muscles relax. For such an embodiment, the actuator disposed in the optic portion is reverse-acting, in the sense that operation of the actuator causes the dynamic surface of the IOL to deflect to lower optical power.
Reverse-acting actuators may comprise, for example, a fluid-filled primary bellows that deflects the dynamic surface to an accommodated state when the haptics are unstressed. A secondary bellows may be coupled to the primary bellows and in fluid communication with the haptic portion. Accordingly, when the ciliary muscles relax, the capsule bag tautens and the lateral faces of the haptics are compressed. This causes fluid to be transferred from the haptics to the secondary bellows. As the secondary bellows expands, it lowers the pressure in the primary bellows, and reduces the deflection of the dynamic surface. Alternatively, a reverse-acting actuator may comprise a hollow cylindrical structure coupled to the dynamic surface, where the cylindrical structure is configured to shorten when fluid is introduced into its interior.
In addition, the optic portion may include any of a number of additional features. Such features may include expandable reservoirs to accommodate fluid volumes expelled during disaccommodation of the lens or a constant volume configuration that simply redistributes fluid volumes to change the optical power of the lens. Alternatively, or in addition, the optic portion may include a fulcrum arrangement configured to multiply the volumetric changes induced by fluid transfers between the haptic portion and optic portion. The IOL also may include a barrier coating on either its internal fluid channels and/or the exterior of the lens to reduce diffusion of fluid into the polymer matrix of the lens.
Methods of making and using the lens of the present invention also are provided.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:
In accordance with the principles of the present invention, an intraocular lens is provided having a haptic portion and a light-transmissive optic portion. The optic portion contains one or more fluid-mediated actuators arranged to apply a deflecting force on a dynamic surface of the lens to provide accommodation. As used herein, the lens is fully “accommodated” when it assumes its most highly convex shape, and fully “unaccommodated” when it assumes its most flattened, least convex state. The lens of the present invention is capable of dynamically assuming any desired degree of accommodation between the fully accommodated state and fully unaccommodated state responsive movement of the ciliary muscles.
Forces applied to a haptic portion of the intraocular lens by movement of the ciliary muscles are communicated to at least one actuator that control deflection of a dynamic surface, which may comprise an anterior or posterior element of the lens. The lens actuator and surrounding fluids all are index-matched to prevent the occurrence of optical aberrations and reflections throughout the range of motion of the actuator and dynamic surface.
Referring to
Isolated from the eye, the relaxed capsule and lens takes on a spherical shape. However, when suspended within the eye by zonules 14, capsule 15 moves between a moderately convex shape (when the ciliary muscles are relaxed) and a highly convex shape (when the ciliary muscles are contracted). As depicted in
Accommodating lenses that are currently commercially available, such as the Crystalens device developed by Eyeonics, Inc., Aliso Viejo, Calif., typically involve converting movements of the ciliary muscle into anterior and posterior movement of an optic portion of the IOL relative to the retina. Such devices do not employ the natural accommodation mechanisms described above with respect to
By contrast, according to one aspect of the present invention, an intraocular lens is designed to engage capsule 15 and to transition between the accommodated and unaccommodated states responsive to forces applied to capsule 15 by ciliary muscle 13 and zonules 14, thereby more closely mimicking operation of the natural eye.
Referring now to
Optic portion 21 comprises anterior lens element 23 including actuator 24 (see
Haptic portion 22 illustratively comprises haptics 28 and 29 that extend from substrate 26, although other haptic configurations may be employed. Each of haptics 28 and 29 includes an interior volume 30 that communicates with channel 31 in substrate 26. Actuator 24 is disposed in well 32 formed in intermediate layer 25 and substrate 26, so that a lower end of the actuator seats within well 32. Haptics 28 and 29 may each include a resilient support member 33 (see
Although channel 31 and well 32 are depicted in
As depicted in
Actuator 24 is disposed in well 31 of intermediate layer 25 and substrate 26, and preferably comprises a sturdy elastomeric material. Intermediate layer 25 isolates fluid in channel 31, well 32 and the interior of actuator 24 from the fluid disposed in the space 34 between anterior lens element 23 and intermediate layer 25. Fluids disposed within channels 31 and space 34, preferably comprise silicone or acrylic oils or other suitable biocompatible fluids, and are selected to have refractive indices that match the materials of anterior lens element 23, actuator 24, intermediate layer 25 and substrate 26.
In a preferred embodiment, actuator 24 comprises a bellows structure integrally formed with anterior lens element 23, and is configured to deflect anterior lens element 23 responsive to fluid pressure applied within the bellows by haptics 28 and 29. Alternatively, actuator 24 may be fabricated as a separate component and glued or otherwise bonded to anterior lens element 23 and intermediate layer 25.
Deflection of the anterior lens element resulting from movement of actuator 24 cause the anterior lens element to transition between an accommodated state, in which the lens surface is more convex, to an unaccommodated state, in which the lens surface is less convex. As will of course be understood, optic portion could instead be arranged so that actuator 24 deflects posterior lens element 27. Still further, the actuator may be configured to induce a major deflection of one lens element and a minor deflection of the other lens element; the arrangement depicted in
The inner surface and thickness of anterior element 23 (relative to the optical axis of the lens) are selected so that the outer surface of anterior element 23 retains an optically corrective shape, e.g., spherical, throughout the entire range of motion of actuator 24, e.g., for accommodations 0–10 diopters. It should of course be understood that the inner surface and thickness of anterior element 23 may be selected to provide an aspherical outer surface, as required for a desired degree of optical correction.
As shown in
In addition, IOL also may include coating 35 disposed on all interior fluid-contacting surfaces within the IOL, such as fluid channel 31 and well 32 and the surfaces defining space 34. Coating 35 is configured to reduce or prevent diffusion of the index-matched fluid used to drive actuator 24, and within space 34, from diffusing into the polymer matrix of the lens components. The IOL of the present invention also may include coating 36, which may comprise the same or a different material than coating 35, disposed on the exterior surfaces of the lens. Coating 36 is intended to serve as a barrier to prevent the diffusion of fluids from the eye into the IOL, and may be disposed on the entire exterior surface of the optic portion and haptic portion, including the anterior and posterior lens elements and haptics.
Alternatively, both coatings 35 and 36 may be layered onto a single surface to prevent or reduce both ingress of bodily fluids into the IOL or fluid circuit, and loss of index-matched fluid from the interior spaces of the IOL. Coatings 35 and 36 preferably comprise a suitable biocompatible polymer, inorganic (e.g., silicone dioxide) or metallic layer (e.g., nickel-titanium) applied by any of a variety of methods known in the art.
Operation of IOL 20 of
When the ciliary muscles relax, the zonules pull the capsule taut, thereby applying compressive forces on the lateral surfaces of the haptics. These forces cause the haptics to deform to the deformed state depicted by the dotted lines in
Referring now to
As depicted in
Referring now to
In the embodiment of
Still referring to
Referring to
In accordance with one aspect of the present invention, substrate 85 includes convex anterior surface 86 having a curvature that provides a predetermined degree of optical correction. Convex surface 86 may be employed either to regularly support anterior lens element 82 in the unaccommodated state, or alternatively only in a fail-safe mode.
In the first case, where convex surface 86 supports anterior lens element 82 in the unaccommodated state, anterior lens element 82 lies flat against convex surface 86 when actuator 83 is in a contracted state, corresponding to the unaccommodated state of IOL 80. Convex surface 86 accordingly results in an unaccommodated degree of optical correction corresponding to the sum of the optical corrections provided by convex surface 86 and posterior surface 87 of substrate 85. For example, posterior lens surface 87 may provide 17 diopters of correction in vivo, while convex surface 86 provides 3 diopters of correction, for a total unaccommodated correction of 20 diopters in vivo.
Actuator 83 is configured to deflect anterior lens element 82 away from convex surface 86 of substrate 85, thereby increasing the optical correction of the anterior lens element. As a central portion of the anterior lens element assumes a more convex shape, the outer periphery of the lens, indicated by zones 88, deflects inward, as indicated by the dotted line in
In addition, convex surface 86 may include radially oriented grooves (not shown) extending from the optical axis to space 89 at the periphery of the optic portion. These grooves permit fluid to flow freely between the posterior surface of anterior lens element 82 and convex surface 86. This arrangement ensures that no vacuum develops between the anterior lens element and convex surface when actuator 83 lifts the anterior lens element away from the convex surface.
Alternatively, anterior lens element 82 may be configured to rest against convex surface 86 only in a fail-safe mode. In this case, anterior lens element 82 is lifted away from convex surface 86 by actuator 83 during normal operation of the IOL. It may be noted that in the foregoing embodiments of the IOL of the present invention, in the undeformed state the haptics maintain the lens in the accommodated or high power state. Accordingly, any failure that allows the actuator to assume the undeformed state without any physiologic influence could result in a residual near-sighted condition. In accordance with another aspect of the present invention, a mechanism is provided to relieve a small amount of quiescent pressure within the lens so that the actuator assumes the unaccommodated, low power state.
In the embodiment of
Alternatively, the sacrificial plug may de disposed on a channel that leads to an evacuated cavity. In this case remodeling of the plug may permit a predetermined quantity of fluid to enter the evacuated space from the fluid channel, again dampening the response of the actuator to fluid transfers resulting from movement of the haptics and ciliary muscles.
Referring now to
Primary actuator 94 is illustratively integrally formed with anterior lens element 93. Intermediate layer 95 includes bellows structures 97 that form secondary actuator 98. Secondary actuator 98 surrounds and is bonded to the lower portion of primary actuator 94, so that the primary and secondary actuators more in unison. Channels 99 extend from the periphery of intermediate layer to the interior of secondary actuator 98, thereby providing fluid communication between the haptic portion and the secondary actuator. As depicted in
Haptic portion 92 comprises haptics 100 and 101 that are coupled in fluid communication to optic portion 91. As depicted in
Still referring to
As described immediately above, the primary and secondary actuators of IOL 90 provide a “reverse” accommodating action compared to the actuators of the preceding embodiments, in that the lens transitions from the accommodated to the unaccommodated states due to the displacement of fluid from the haptic portion to the optic portion of the lens. Due to the relative complexity and potential for optical aberrations arising from the presence of the primary and secondary actuators within the optic portion, it may be advantageous to relocate such mechanisms to the periphery of the optic portion of the lens. The embodiment of
Referring now to
Haptics 116 and 117 are similar to those described for the embodiment of
In operation, compression of haptics 116 and 117 displaces fluid from the haptics flows into reservoirs 118, thereby causing the bellows-like walls of the reservoir to expand. This in turn increases the volume in the adjoining reservoir 115 and withdraws fluid from channel 114, thereby reducing the extension of the actuator and the displacement of the anterior lens element. In this manner, positive fluid flows from the haptics result in the reduction of the deflection of the anterior lens element, transitioning IOL 110 from an accommodated state to an unaccommodated state.
As also illustrated in
Referring now to
When the ciliary muscles relax, compressive forces applied by the capsule displace fluid from the haptic portion to the optic portion of the lens. In particular, as fluid is displaced into actuator 132, the cylindrical wall of the actuator expands to a spherical configuration, as depicted in
While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.
This application is a continuation-in-part of U.S. patent application Ser. No. 10/971,598, filed Oct. 22, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 10/734,514, filed Dec. 12, 2003, now issued as U.S. Pat. No. 7,122,053 and claims the benefit of priority from U.S. provisional patent application Ser. No. 60/433,046, filed Dec. 12, 2002.
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| Child | 10971598 | US |
