WO2009021326A1 - Pneumatic intra-ocular lens - Google Patents

Abstract

The invention provides a device that provides for a resilient gas filled pneumatic intra-ocular lens, or a system of optical interfaces that includes at least one pneumatic lens, which may be inserted into the intra-capsular space of an aphakic eye after extra-capsular extraction, together with either an integrated or a compatible independent suspension system to restore accommodation by changing the curvature of at least one surface of the pneumatic lens in response to changes of ciliary muscle tone. A feature of the pneumatic lens may be used to alter the refractive power of the lenses by the inclusion of gas releasing, laser absorptive materials within the hollow interior of the pneumatic lens, so that its curvature may be altered after implanting. The lens therefore is also useful for incorporating in the existing accommodating or pseudo-accommodating systems which linearly displace the intra-ocular lens without changing the lens shape.

Description

PNEUMATIC INTRA OCULAR LENS

Reference to Related Applications

[0001] The present application claims the benefits, under 35 U.S.C.§119(e), of U.S. Provisional Application Serial No. 60/955,619 filed August 13, 2007 entitled "PNEUMATIC INTRA-OCULAR LENS" which is incorporated herein by this reference.

Technical Field [0002] The invention relates to the field of intra-ocular lens implants.

Background

[0003] The human crystalline lens is encapsulated by a transparent fibrous envelope called the lens capsule and is suspended behind the pupil by a network of fibrous ligaments called zonules. These zonules run radially along the entire equator of the lens capsule and attach it to the processes of the ciliary body as shown on Fig. 1. The muscles of the ciliary body pull systematically upon the zonules to compress the contents of the lens capsule, changing the curvature of the crystalline lens thereby focusing the eye upon different distances within space. This is called accommodation and for young people who have resilient crystalline lenses with little internal resistance, it happens almost instantaneously.

[0004] The eye focuses upon distant objects when the ciliary body dilates. The zonules pull upon the equator of the lens capsule causing the opposing walls of the lens capsule to squeeze the crystalline lens, compressing and flattening it into its extended state. Conversely, when the ciliary body constricts, tension within the zonules is relaxed and elastic forces within the crystalline lens return it to its steeper, habitual distended state, focusing the eye upon near objects. The refractive index of the human crystalline lens varies throughout its distinct regions shown on Fig. 1 but overall, it is slightly greater than the refractive index of the surrounding aqueous humor. Accommodation, therefore, requires a substantial curvature change of the crystalline lens to focus the eye upon 'near' objects in visual space.

[0005] Extra-capsular lens extraction is a surgical procedure whereby the crystalline lens within the human eye is removed while sparing the peripheral regions of the anterior lens capsule, the posterior lens capsule and the zonules. The central region of the posterior lens capsule is often removed post-operatively, to clear away opaque fibrous material. Conventionally, the extracted crystalline lens is replaced by a synthetic lens which is suspended within a collapsed and gaping lens capsule by means of hooks, wires, springs and the like. The geometry of the lens capsule is compromised and the functional relationship between the ciliary body and the lens capsule is lost, resulting in a complete loss of accommodation. The contents of the vitreous body are precipitously shifted out of normal position leaving the eye vulnerable to a host of post-operative complications, such as vitreous membrane obstructions, retinal detachment, macular trauma, etc.

[0006] A second type of procedure, referred to as 'pseudo accommodation', which is more difficult to install, changes the vergence of light with the use of mechanical suspension systems that shift the position of a mono-focal intra-ocular lens forward toward the iris plane in response to ciliary muscle action to focus the eye upon near objects. Apparatus of the "pseudo-accommodative" type are shown in United States Patent no. 6,027,531 Tassignon and United States Patent Application Publication no. 2007/0123981 Tassignon. Damaging wear on the bearing surfaces of the lens capsule remains a long term concern. Recent attempts to restore the post-operative loss of accommodation have resulted in the development of a new class of intra-ocular lens implants called 'accommodative' intra-ocular lens implants. The refractive elements of these devices actually change curvature in response to changes in the tone of ciliary muscle. An accommodative intra-ocular lens implant which consists of a resilient convex lens and a suspension system made of springs and flexible housing materials, has been recently introduced to the market place under the trademark CRYSTALENS by Sysonics, Inc. This entire apparatus is inserted into the anterior chamber of the eye and then fitted into an aphakic lens capsule. Accommodation is re-established in keeping with the same basic principles operational for the natural crystalline lens but its efficiency is poor. Accommodation is limited due to the fact that the lens capsule geometry is poorly restored, the range of curvature change of the resilient convex lens is nominal and its refractive index is close to that of the aqueous humor. Material fatigue and damaging wear on the bearing surfaces of the lens capsule are long term issues yet to be assessed. This device is difficult to install, calibrate and align and much more difficult to retrieve in the event of an unacceptable outcome.

[0007] The elastic coefficient of the crystalline lens, the refractive index of the crystalline lens, the geometry or 'shape' of the lens capsule, the internal resistance of these structures and the forces conducted by the zonules, are crucial elements that make the delicate dynamic called accommodation work well. In addition to the task of creating functional improvements, risk mitigation - short term and long term - must be seriously considered. There is therefore a need for improvement.

[0008] The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

Summary

[0009] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

[0010] The invention therefore is a device that provides for a resilient gas filled 'pneumatic' intra-ocular lens, or a system of optical interfaces that includes at least one pneumatic lens, which may be inserted into the intracapsular space of an aphakic eye after extra-capsular extraction, together with either an integrated or a compatible independent suspension system to restore accommodation by changing the curvature of at least one surface of the pneumatic lens in response to changes of ciliary muscle tone.

[0011] More particularly the invention provides an intraocular lens for implantation into the intra-capsular space of an aphakic eye to restore accommodation by changing the curvature of at least one surface of said lens in response to changes of ciliary muscle tone, comprising: i) a resilient optical lens body of elastically deformable, non-gas-permeable material forming a gas-filled interior chamber, and having an anterior surface and a posterior surface and a central transparent optical zone; and ii) haptic means for transferring changes of ciliary muscle tone to said optical lens body.

[0012] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.

Brief Description of Drawings

[0013] Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.

[0014] In drawings which illustrate a preferred embodiment of the invention: Fig. 1 is a diagram illustrating the components of the related ocular anatomy.

Fig. 2a is a vertical cross section of a first embodiment of the invention shown in distended state.

Fig. 2b is a vertical cross section of the embodiment of the invention shown in Fig. 2a in extended state.

Fig. 2c is a front view of the embodiment of the invention shown in Fig. 2a. Fig. 3a is a vertical cross section of a second embodiment of the invention in distended state.

Fig. 3b is a vertical cross section of the embodiment of the invention shown in Fig. 3a in extended state.

Fig. 3c is a front view of the embodiment shown in Fig. 3a.

Description

[0015] Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0016] Fig. 1 shows the natural bi-convex crystalline lens within the human eye. Overall, the refractive index of the crystalline lens is approximately 1.420. The refractive index of aqueous humor is 1.336. The differential: 1.420 - 1.336, is thus +0.094. The differential of the refractive index between a pneumatic lens and aqueous humor: 1.000 - 1.336 is thus: - 0.336. This differential is approximately three and one half times greater between air and aqueous humor than it is between the crystalline lens and aqueous humor. The present invention takes advantage of the fact that to produce the same magnitude of accommodation, a gas-filled lens will require less than one-third the change of curvature than does a solid crystalline lens. The minus sign indicates that the curvature change of the pneumatic lens must be opposite to that of the crystalline lens. In this respect then, a pneumatic lens must either increase the concave curvature of one of its surfaces to focus the eye upon near objects within visual space or it must decrease the convex curvature of one of its surfaces to focus the eye upon near objects within visual space.

[0017] The present invention has found that gasses within a resilient optical encasement present an excellent opportunity to re-establish accommodation effectively. In addition to advantageous refractive properties, gasses have excellent elasticity and fluidity with very little internal resistance. Gasses used to fill the pneumatic intra-ocular lens implant should be relatively inert, physiologically compatible and preferably of large molecular weight, such as the ones used for reparative retinal surgery, available from Alcon Laboratories Inc under the trademark Ispan C3F8 for medical grade perflurocarbon gas and Ispan SG6 for medical grade sulfurhexafloride gas. Air may also be used.

[0018] A pneumatic intra-ocular lense according to the invention may be constructed of many suitable varieties and combinations of non- permeable medical-grade resilient, flexible and semi-rigid materials. Preferably, all construction materials are optically transparent, compatible with anti-reflective surface coatings and possess ultra-violet absorbing properties. The pneumatic lenses are manufactured with the use of plastic injection molding technologies and split mold technologies that are used to predetermine the shape and the optical properties of the pneumatic lenses. Heat and laser welding techniques and vapor controlled environments are used to produce the lenses at atmospheric pressures. For example, the lenses can be welded in a chamber or similar environment where the gas in the chamber is controlled and restricted to the gas for filling the lens, at the appropriate pressure, which will typically be ambient or atmospheric. Alternatively the gas can be injected into the lens at the desired pressure.

[0019] Various optical features, such as aspheric optical interfaces, may be integrated within a pneumatic intra-ocular lens implant according to this invention to sharpen the resolution of the resultant retinal image. There are illustrated in the following description two viable accommodative pneumatic intra-ocular lens implant designs. The first is a concave pneumatic lens which flattens to focus upon distant objects, as shown of Fig. 2a, 2b and 2c. The second is a pneumatic lens which increases in convexity to focus upon distant objects, as shown on Fig. 3a, 3b and 3b.

[0020] Fig. 2a is a cross section of an embodiment of the invention where pneumatic lens 20, a concave lens, is shown in its habitual 'distended' state. In the present context of a pneumatic intra-ocular lens, the 'distended' state refers to the lens capsule as being relaxed. Normally, a relaxed lens capsule means that the human eye is focused upon near objects in visual space. Conversely, the 'extended' state shown in Fig. 2b refers to the lens capsule as being compressed. Normally, a compressed lens capsule means that the human eye is focused upon distant objects in visual space.

[0021] Pneumatic lens 20 is formed of a hollow, flexible body 21 molded of a non-permeable, medical-grade resilient, flexible, semi-rigid optically transparent material. It preferably has an anti-reflective surface coating and ultra-violet absorbing properties. It has a hollow interior 23 filled with a gas such as air or medical-grade perflurocarbon gas to a pressure roughly equal to or higher than atmospheric pressure but low enough to preserve flexibility. Optical plate 22 is a semi-rigid shield that defines the optical zone 24 of pneumatic lens 20. Its surfaces may be shaped to provide for the correction of hyperopia, myopia, and astigmatism. It is circumscribed by shelf 26 which serves as an interface for any compatible intra-ocular suspension system. [0022] The outer region of pneumatic lens 20, which extends beyond the optical zone, is referred to as haptic zone 28. The structure of the haptic zone 28 consists of convex wall 30 on one side and concave wall 32 on the other side. The perimeter of haptic zone 28 is circumscribed by a series of 'pleated' projections called skates 34.

[0023] In operation, haptic zone 28 is compressed when shelf 26 is pressed toward concave wall 32 by forces exerted upon skates 34 by a compatible suspension system when ciliary muscle tone changes. Skates 34 slide distally and then proximally upon the surface of this compatible suspension system when haptic zone 28 is either compressed or relaxed. Respectively, this movement changes the diameter of pneumatic lens 20 and alters the curvature of concave optical zone 36. This dynamic is mediated by the ciliary muscle at one end of the mechanical chain and by the elasticity of convex wall 30, concave wall 32 and the elements within them. Skates 34 are constructed so as to minimize friction upon the surface of the compatible suspension system and to allow aqueous humor to vent freely between concave optical zone 36 and the supporting surface of the compatible suspension system.

[0024] Radiations 38 are a series of expandable 'pleats' within both the convex and the concave walls of pneumatic lens 20 as shown on Fig. 2c. These radiations and the pleated skates 34 provide for the expansion and the contraction of pneumatic lens 20 so that the curvature of concave optical zone 36 may change evenly and easily.

[0025] The sagital depth A is the distance measured from the apex 33 of concave wall 32 to the base 40 of concave wall 32. The sagital depth is greatest when haptic zone 28 is relaxed as shown in Fig. 2a -the 'distended' state. When haptic zone 28 is compressed between shelf 26 and skates 34, the sagital depth A decreases as does the curvature of concave optical zone 36 as shown of Fig. 2b - the extended state.

[0026] Fig. 3a is a cross section of another embodiment of the invention where pneumatic lens 50 is shown in its habitual 'distended' shape. Pneumatic lens 50 is similarly formed of a hollow, flexible body 51 molded of a non-permeable, medical-grade resilient, flexible, semi-rigid optically transparent material. It preferably has an anti-reflective surface coating and ultra-violet absorbing properties. It has a hollow interior 53 filled with a gas such as air or medical-grade perflurocarbon gas to a pressure higher than atmospheric pressure but low enough to preserve flexibility. Resilient optical interface 52 defines optical zone 54. Optical zone 54 is circumscribed by a series of projections called suspension interface 56. The suspension interface attaches to any compatible independent intra-ocular suspension system.

[0027] The outer region of pneumatic lens 50 that extends beyond the optical zone 54 is referred to as haptic zone 58. The structure of haptic zone 58 consists of convex wall 60 on one side and concave wall 62 on the other side. The concave wall 62 thickens in its central region to create static optical interface 64. Static optical interface 64 may be shaped to correct myopia, hyperopic and astigmatic refractive errors. Central lens thickness B is the distance separating the center of resilient optical interface 52 and the center of static optical interface 64, as shown on Fig. 3a and Fig. 3b.

[0028] In operation, haptic zone 58 is compressed when suspension interface 56 is pressed toward concave wall 60 by forces exerted by the ciliary body upon a compatible suspension system. The gas 53 within pneumatic lens 50 is displaced centrally, pushing against resilient optical interface 52 to increase central lens thickness B. Respectively, the curvature of optical zone 54 is increased and the eye is focused upon distant objects in visual space as shown in Fig. 3b. When force exerted by the compatible suspension system is reduced, elastic properties within resilient optical interface 52, convex wall 60, and concave wall 62 cause pneumatic lens 50 to return to its habitual 'distended' state as shown in Fig. 3a. The eye is then focused upon near objects in visual space. This dynamic is mediated by the ciliary muscle at one end of the mechanical chain and by the elasticity of pneumatic lens 50 at the other end. A variation of this embodiment would be for concave wall 62 to actually be flat or even convex in shape.

[0029] Features from the foregoing embodiments may be amalgamated into various hybrid designs. For example lens 50 may have both a resilient optical interface 52 on the front surface as shown in Fig. 3a and a concave optical zone on the back surface as shown at 36 in Fig. 2a.

[0030] A useful feature which may be used to alter the refractive power of pneumatic intra-ocular lenses is the inclusion of gas releasing, laser absorptive materials within the hollow interior 23, 53 of the pneumatic lens. Materials such as collagen or carbamide may be situated within the pneumatic lens 20, 50 and then irradiated with laser energy to release carbon dioxide, nitrogen and other heavier gasses within the pneumatic lens. Pulsed YAG laser systems may be selected and calibrated to release discrete volumes of gas to alter the curvature of at least one surface of a pneumatic intra ocular lens, allowing the clinical refractionist the ability to accurately determine the 'end-point of refraction' of the eye. These adjustments could be performed at the time of surgery or at any future date as needed. An optically transparent collagen interface, optionally supported by laser reflective material could be retained within either the optical zone or the haptic zone of the pneumatic lens. Accurate laser technologies, such as Intralase femtosecond laser systems, could be used to reshape the optical surface of the collagen interface at the same time as it releases gasses. Opaque gas releasing materials must be located peripherally to the optical zone 24, 54. [0031] Ultimately, laser systems could be used to alter the curvature of any laser-absorptive refractive surface of the pneumatic intra-capsular lens 20, 50 or any other optical interface used in conjunction with pneumatic intra-ocular lenses to correct unwanted ametropia. Released gasses would either permeate through the tissues of the eye, eventually disappearing or be retained within the pneumatic intra-ocular lens.

[0032] The pneumatic intra-ocular lens may be introduced into the eye through a tubule fitted through a small incision, such as rolled up upon itself, and then unfolded once positioned within the intra-capsular space. The present invention is particularly useful when used in conjunction with the inflatable lens capsule retainer which is the subject of this same Applicant's co-pending United States provisional patent application serial no. 61/051,075 entitled INFLATABLE INTRA OCULAR LENS/LENS RETAINER, and which is incorporated herein by reference.

[0033] The lens described according to this invention is also useful for incorporating in the existing accommodating or pseudo-accommodating systems described above which linearly displace the intra-ocular lens without changing the lens shape. This arises from the feature of the pneumatic lens which may be used to alter the refractive power of the lenses by the inclusion of gas releasing, laser absorptive materials within the hollow interior 23, 53 of the pneumatic lens. The pneumatic intra-ocular lens 20, 50 may be inserted into the accommodating or pseudo- accommodative structure, and by irradiating materials within the lens as described above with laser energy to release carbon dioxide, nitrogen and other heavier gasses within the pneumatic lens, its curvature can be altered or corrected. For example if the eye surgeon determines that a correction to the curvature of the lens is required after insertion, pulsed laser radiation could be directed to release discrete volumes of gas to alter the curvature of at least one surface of the pneumatic intra-ocular lens, allowing the surgeon or clinical refractionist to alter the curvature of the lens surfaces, correct the ' end-point of refraction' of the eye or reshape the optical surface of the collagen interface at the same time as it releases gasses. These adjustments could be performed at the time of surgery or at any future date as needed after the lens is implanted.

[0034] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the invention be interpreted to include all such modifications, permutations, additions and sub-combinations as are within its true spirit and scope.

Claims

WHAT IS CLAIMED IS:

1. An intraocular lens for implantation into the intra-capsular space of an aphakic eye to restore accommodation by changing the curvature of at least one surface of said lens in response to changes of ciliary muscle tone, comprising: i) an optical lens body of elastically deformable, non-gas- permeable material forming a gas-filled interior chamber, and having an anterior surface and a posterior surface and a central transparent optical zone; and ii) haptic means for transferring said changes of ciliary muscle tone to said optical lens body.

2. The intraocular lens of claim 1 wherein said gas filling said interior chamber has a pressure equal to or greater than atmospheric pressure.

3. The intraocular lens of claim 1 wherein said gas is an inert gas of large molecular weight.

4. The intraocular lens of claim 3 wherein said gas is selected from the group perflurocarbon gas, sulfurhexafloride gas and air.

5. The intraocular lens of claim 1 wherein said optical lens body is concave in the distended state and decreases in concavity in the extended state.

6. The intraocular lens of claim 5 wherein said optical lens body decreases in concavity in the extended state by decreasing the curvature of said posterior surface.

7. The intraocular lens of claim 1 wherein said optical lens body is convex in the distended state and increases in convexity in the extended state.

8. The intraocular lens of claim 7 wherein said posterior surface of said optical lens body has a larger radius of curvature than said anterior surface.

9. The intraocular lens of claim 7 wherein said optical lens body increases in convexity in the extended state by increasing the curvature of said anterior surface.

10. The intraocular lens of claim 9 wherein said posterior surface of said optical lens body comprises an optical surface shaped to correct refractive errors.

11. The intraocular lens of claim 1 wherein said haptic means comprises an outer region extending beyond said optical zone, comprising a plurality of projections for engaging an intra-ocular suspension system .

12. The intraocular lens of claim 11 wherein said haptic means comprises an outer region extending beyond said optical zone, comprising a convex wall, a concave wall and a perimeter provided with said plurality of projections for engaging an intra-ocular suspension system.

13. The intraocular lens of claim 1 further comprising a gas releasing, laser absorptive material within the hollow interior of said optical lens body , so that its curvature may be altered after implanting.

14. The intraocular lens of claim 1 further comprising means for engaging an intra-ocular suspension system .

15. The intraocular lens of claim 1 further comprising a transparent optical shield on said anterior surface in said optical zone, said shield having a surface shaped to provide for vision correction.

16. The intraocular lens of claim 15 wherein said shield comprises at its periphery means for engaging an intra-ocular suspension system.

17. An intraocular lens for implantation into the intra-capsular space of an aphakic eye to restore accommodation by changing the curvature of at least one surface of said lens in response to changes of ciliary muscle tone, comprising: i) an optical lens body of elastically deformable non-gas- permeable material forming a gas-filled interior chamber, and having an anterior surface and a posterior surface and a central transparent optical zone; and iii) a gas releasing, laser absorptive material within the hollow interior of said optical lens body , so that its curvature may be altered after implanting.

18. The intraocular lens of claim 17 wherein said laser absorptive material is a collagen or carbamide.

19. The intraocular lens of claim 18 wherein said laser absorptive material is an opaque material located peripherally to said optical zone.

20. A method of altering the refractive power of an intra-ocular lens implanted into an eye, said intra-ocular lens comprising a resilient optical lens body of elastically deformable, non-gas-permeable material forming a gas-filled interior chamber, and having an anterior surface and a posterior surface and a central transparent optical zone, said method comprising the steps of:

i) providing a gas releasing, laser absorptive material within the interior chamber of said optical lens body, so that its curvature may be altered after implanting; ii) after implanting of said intra-ocular lens, irradiating said laser absorptive material within the interior chamber of said optical lens body with laser energy to release gas within the interior chamber of said optical lens body, so that its curvature is altered.

21. The method of claim 20 wherein said laser absorptive material is a collagen or carbamide.

22. The method of claim 21 wherein said laser absorptive material is an opaque material located peripherally to said optical zone.