WO2010004094A1

WO2010004094A1 - A foldable intraocular lens implant

Info

Publication number: WO2010004094A1
Application number: PCT/FI2009/050622
Authority: WO
Inventors: Jani Pelto; Hannu Uusitalo
Original assignee: Tampereen Yliopisto; Tampereen Teknillinen Yliopisto
Priority date: 2008-07-09
Filing date: 2009-07-09
Publication date: 2010-01-14
Also published as: FI20085714A0

Abstract

The present invention relates to a foldable intraocular lens implant suitable to be mounted as a folded state. The implant consists of an optical part and a non-optical part. The implant comprises means for altering the refractive properties of the implant being integrated into the implant and the means for altering the refractive properties of the implant being adapted to react to an electric signal.

Description

A foldable intraocular lens implant

Field of invention

The present invention relates to a foldable intraocular lens implant.

Background of the invention

Untreated cataract is the leading cause for blindness in the world. According to recent Finnish statistics (Duodecim 2006), it affects approximately 16% of the 65-69 old, and over 70% of the 85 old in the general population. Cataract surgery is the only treatment for the disease. In the surgery, the original adaptable intraocular lens (IOL) is first removed and then replaced by an artificial IOL having a fixed refractive power. The focusing function of the human eye is permanently lost in the operation. The main reason for the impairment is that the function of the ciliary body through the action of the zonular fibers cannot be restored.

Prior the operation the surgeon measures the biometric characters of the eye and estimates the desired refractive power of the artificial IOL. The basis of the calculation is that the single focal length is predetermined. However, even with careful measurements and optical calculations the focus point might differ from the designed due to the unpredictability in the actual positioning on the IOL implant in its capsule. This might necessitate further surgical procedures, either placing another corrective lens or reshaping the anatomy of the eye by laser surgery. The fixed refractive power of the IOL necessitates also the need of large number lOL^'s with various refractive powers to be manufactured and stored.

The most commonly applied IOL implants today are foldable and elastomeric with optical part diameter of approximately 6 mm. They are mounted to the lens capsule by forceps or an applicator device through the same opening as the phacoemulsification instrument. For medical reasons related to the healing of the surgical opening, the current standard is an opening of approximately 3 mm in the cornea. This sets the practical limit to the size and the design of an active IOL implant. Summary of the Invention

The present invention relates to a foldable intraocular lens (IOL) implant to be mounted in a folded state, which makes it suitable for small incision surgery. The implant comprises an optical part with a diameter of approximately 6 mm and a non-optical part. The implant is capable of changing its refractive properties, such as the refractive power. The operation of the device mimics the natural accommodation of the human eye. The shape and therefore the focal length of the IOL implant can actively be changed by means for altering the refractive properties of the implant which are adapted to react to an electromagnetic signal. In other words, the above-mentioned means of the implant are electrically powered by either with a wire or wirelessly, wireless powering is preferred.

The means for altering the refractive properties of the implant may be integrated into the material of the implant, which means that these means are attached to the outer or inner surface of the implant, or they are embedded in the implant. Preferably the means for altering the refractive properties are embedded in the implant. The means for altering the refractive properties of the implant comprise actuators which are described below.

Large 10 Diopter changes in refractive power of the IOL implant are gained by changing the shape of the lens. The mechanism inducing the change must not interfere the optical performance of the lens. Therefore, preferably all actuating parts should be placed on the non-optical area of the implant, i.e. on the outer region of the implant. However, it is possible to place actuating parts on the optical area of the implant if the optical features of actuating parts are adequate. The IOL implant, including all auxiliary components, should be directly mountable through the approximately 3 mm surgical incision in the cornea and therefore foldable. The lens should have a mechanically rigid support in the walls of the lens capsule. The haptics utilized in the commercial lens designs in clinical use today meet this criterion. Preferably the implant comprises a wirelessly powered electrochemical actuator mechanism embedded into the optical material of the soft polymeric IOL structure or alternatively into the haptics. The mechanism can be used to tune the refractive power of the lens implant to the optimum value only once after the implantation, or the mechanism can be used several times so that there are sensors which control the need for tuning. Similarly the movement of the haptics changing the position of the IOL in the eye can be regulated. The adaptation can be controlled by sensory signals from the natural movement of the ciliary muscle, by sensors detecting the changes in the converge of optical axes of the eyes or by electrical microelectrodes detecting action potentials from the ciliary muscle.

The means for altering the refractive properties of the lens implant comprise electrically conductive material, such as electrically conductive polymers or carbon nanotubes. Common to both these materials is that they are capable of undergoing a dimensional change under conditions to be specified below and, as a part of an actuator structure, to convert this change to a motion of other parts.

Electrically conductive polymers, i.e. conjugated polymers are particularly well suited materials for biomedical applications. They produce large strains (up to 30%) and stresses higher than in the muscle tissue. Their favourable mechanical properties, Young's modulus (0.05-100 GPa) and tensile strength (1 -1000 MPa) enable considerable force output for a multitude of practical tasks (Smela, E. Advanced Materials Vol. 15 (2003), No.6.481 and references therein). Other attractive features of the conductive polymers in biomedical applications are: they have low actuation voltage, typically 1 Volt or even less, they can continuously be positioned as a function of the electrical driving potential, and additionally, they keep fairly well their strain under DC voltage without considerable sustained power input. For example, polyaniline, polythiophenes and polypyrrole may be used as the conductive polymer. However, polypyrrole or poly(3,4-ethylene dioxythiophene) (PEDOT) are the preferred choices.

Cell- and protein adhesion and generation of fibrous tissue on the implanted surfaces are crucial for the performance of most devices in vivo. Among the electrically conductive polymers, polypyrroles have proven biocompatibility (Rivers et al. Advanced Functional Materials VoI 12 (2003) p. 33), both in vitro and in vivo, and the biological affinity (including hydrophopicity) of the polypyrrole surface towards different cell lines can be tailored by the choice of the dopants. Eye humour contains relatively low concentration of protein, about 200 times less than blood plasma (Adler's Physiology of the Eye, p.242) and therefore it is not expected that the polypyrrole would induce unwanted protein- and cell adsorption into the lens area. Such problems, however, can be solved by the right choice of the dopant in the polypyrrole surface in contact with the eye humour or by applying an ion-permeable biocompatible layer. Most importantly, the lens is designed so that the cell migration and attachment after phacoemulsification will restrict the development of secondary cataract over the optical parts of the lens implant. One important factor is that the lens implant does not contain any cavities or edges which are prone to collect impurities, such as stray cells and protein, because the means for altering the refractive properties of the lens implant are situated on the surface of the implant, or they are embedded in the implant. Therefore, in the preferred embodiment the actuator element and all the necessary electronic component are embedded in the biocompatible lens material.

The refractive power of the soft implanted convex or biconvex lens is adjusted by a electrochemical actuator mechanism. The actuator or array of actuators is integrated into a soft artificial IOL lens by embedding or by directly attaching to a soft artificial IOL lens, such as the commercially available silicone elastomer or acrylic elastomer lenses. The bending motion of the polypyrrole bilayer actuator array, the volumetric expansion of the polypyrrole or the linear motion of a polypyrrole fiber actuator is deforming the soft optical part of the IOL. The force generated by the actuators is sufficiently large to deform the soft lens into a more convex shape and to sustain the deformed shape with minimum electric power.

The actuator, or the array of actuator elements, is based on the electroactivity and the related dimensional changes of a conductive polymer film upon ion fluxes from the surrounding electrolyte. Similar swelling behaviour, albeit based on different physical background can be also observed in a nonwoven carbon nanotube paper (bucky paper). In particular, the single walled carbon nanotube (SWCNT) sheets have proven efficient motion in 1 M sodium chloride electrolyte under electrical stimulus of ±1 Volts vs. SCE [Science, Baughmann vol 284 (1999) p.1340]. In the present invention the concept ofelectrochemical actuator should be understood in this wider sense.

The actuation motion can be either bending of a bilayer structure or direct coupling of volumetric expansion to an moving mechanism. The electrolyte providing the ions for the actuation can be complex buffer media [Pandey, S.S. Sensors and actuators B 102 (2004)] or the body electrolytes (blood, urine etc.) [Jager, E.W.D. et Al. Science VoI 290 (2000) p.1540]. Certain biocompatible polypyrroles can be in direct contact with the fluid without any encapsulation or embedded in a biocompatible solid polymer electrolyte gel.

Especially suitable conductive polymer for implantation are the polypyrroles doped with bulky anions, such as dodecylbenzene sulfonate (DBS ); and polyanions such as poly(sodium-4-sulfonate) PSS^", hyaluronate (HA^"), chondroitin sulphate (CS^") and their derivatives for they are practically immobile in polypyrrole matrix and render the polypyrrole a cation exchanging material that can actuate by the fluxes of alkali ions and their hydration presents in the bodily fluids.

In another design, leading to somewhat increased electrochemical stability and performance (speed, power output), but decreased biocompatibility of the polypyrrole, the actuator utilizes encapsulated active layer with a solid polymer electrolyte e.g. consisting of an organic solvent such as propylene carbonate and an organic electrolyte salt such as tetraethylammonium tetrafluorophosphate. The above mentioned and the other well known organic solvents and electrolyte salts cannot be utilized without an permanent encapsulation layer because the chemicals are not biocompatible and must not leach out to the eye humour.

The material of the lens implant must be such that it can be folded during the implantation, i.e. the lens is inserted through a small incision during a surgery in a folded state. The incision is made in a cornea or corneoscleral limbus and its diameter according to the current standards is approximately three millimeters, but at least 20% less than the diameter of the optical part of the lens. Usually the material of the lens implant is referred to as being soft. Suitable materials for the lens implant are, for example, silicone elastomers or acrylic elastomers.

The mechanical properties of the lens material are important in dimensioning the deformable parts of the IOL implant. The elastomeric material and the lens design, especially in the optical part of the lens should allow easy deformation under mN forces and bending moments. It is advantageous to use a hollow lens filled with fluid. An obvious advantage to the convex deformability of the optical part is gained when the supporting periphery of the IOL implant is free to deform along the other parts. Therefore the outer non-optical part may consist of several more rigid parts connected by very soft deformable parts.

The adjustable lens mechanism can be utilized with slight modifications in post-surgery fine adjustment i.e. in one-shot operation. The final geometry of the implant can be fixed by (i) an interlocking mechanism utilizing electrochemical actuators or (ii) photoactive interlocking by a photopolymerizable support mechanism activated by an ophthalmic laser.

Powering and the data transmission of the implant and sensor components measuring properties of an eye are preferably wireless. The wireless transtissue energy transfer is based on either radiofrequency inductive link, photoelectric transfer in infrared or near infrared bands or on acoustic (ultrasonic) transfer of energy. Particularly useful is a inductive link operating at 1 -10 MHz range, where the unwanted absorption of energy to tissue is minimized. Adaptable electronics should be used to ensure that safe level of electromagnetic radiation is passed through the tissue. An example of a adaptable wireless powering system for an ophthalmic retinal implant is given in (IEEE Transaction of Circuits and Systems 2005, Vol.52, No.10 p.2109). The general principle of adaptable inductive link is described in the following: optimized pair of coils driven by Class-E power amplifier. Reverse telemetry forms a feedback loop with a power control unit thus regulating the transmitted power. Rectifying diode and voltage regulating circuits are utilized to compensate the variations in the inductive coupling of the transmitting and receiving coils and the loading of the receiving circuit without passing excessive power. The electric current drawn by the electrochemical actuator on each cycle is in the order of 10- 100 mA. Working in a 1 Volt potential window requires approximately 10-100 mW power on each actuation. Such momentary power is fairly easily supplied by the adaptable inductive link described above. The active electronic components of the receiver circuit are packed on a miniaturized integrated CMOS circuit. The on chip electronics, receiving antenna and other necessary passive component, such as voltage regulation capacitor are implanted in the ciliary capsule of the eye, i.e. they are integrated in the implant. It is possible, for example, to arrange the integrated antenna around the lens structure as a thin coil, which makes the power transmission effective, or to the haptics, where the coil structure is smaller than around the lens structure.

The circuit driving the electrochemical actuator array can be controlled by multitude of sensory inputs. The actuator array is activated upon accommodation of the eye. The sensory input on the accommodation can be drawn from the electrical or mechanical activation of (i) ciliary muscle, (ii) ciliary body-zonular complex, (iii) the six extraocular muscles or (iv) by detecting the convergence of the optical axes. The electrical activity (action potentials) of the eye muscles can directly detected by microelectrodes. Mechanical movement of the muscles can be measured by e.g. miniaturized pressure sensor placed in the ciliary body. The convergence and divergence of the eyes can be detected by e.g. miniaturized low power acceleration sensors. The pressure and acceleration sensors are preferably based on Microelectromechanical Systems (MEMS) or Nanoelectromechanical Systems (NEMS) technology. Such sensors designed for invasive biomedical measurement of the eye and blood pressure exist and they are commercially available, for example, from VTI Technologies Oy, Finland. The necessary circuits for driving and reading the sensors are preferably integrated to the same chip as the wireless link. The present invention is not, however, limited to NEMS and MEMS technologies but can utilize any other low power miniaturepressure- and acceleration sensor technology such as piezoelectric sensors.

Standardized inductive RF links for implantable devices exist, operating at specific frequency range. For example, The Federal Communications

Commission (FCC) and The European Telecommunications Standards Institute (ETSI) have defined such ranges. Medical Implant

Communication Service (MICS) allows a range from 402 MHz to 405 MHz.

Description of the Drawings

Foldable designs of electrochemical bending, linear or volumetric actuators, integrated into lens structures are described in the following examples of detailed description. The examples are accompanied by drawings, in which

Figs. 1 a and 1 b show the intraocular implant in vertical cross-section and front view according to a first embodiment,

Fig. 1 c shows the actuator of the implant in cross-section along line A-A of

Figs. 1 d and 1 e show the intraocular implant of Figs. 1 a and 1 b in a second position, Figs. 2a and 2b show the intraocular implant in vertical cross-section and front view according to another embodiment,

Figs. 3a and 3b show the intraocular implant in vertical cross-section and front view according to still one embodiment, and

Fig. 4 shows the coupling between the external means for controlling the refractive properties of the IOL and the IOL.

Detailed Description of the Invention

In the following examples, polypyrrole is used as an electrically conductive material. However, e.g. poly(3,4-ethylene dioxythiophene) is usable in the same kind of applications.

Example 1.

Bending beam type actuators (bending bimorph actuators) integrated into the soft lens:

In the structure of the example of Figs. 1 a to 1 e, the IOL comprises several radially extending, polypyrrole containing bending beam type actuator elements 1 , symmetrically positioned to the outer region of the IOL, around the optical aperture, and electrically connected in parallel, and haptics 1 1 attached to the outside of the lens and supporting the lens in the lens capsule. The haptics are normally a pair of resiliently deformable elements known as such.

The bending beam type actuator 1 comprises one (bilayer type) or two (trilayer type) active polymer layers electropolymerized on thin metal layers. The actuator will bend and generate a bending moment upon applying a reducing or oxidative potential on the metallic conductive substrate of the active polypyrrole.

The 10-100 μm thick polypyrrole layers (shown in black in Fig. 1 c) are electrochemically grown onto thin (10-200 nm) porous electrically conductive substrates 2 supported by flexible backing 3. The polypyrrole in grown either on one- (bilayer) or both sides (trilayer) of the backing material. The force output of the actuator can be increase by increasing the thickness of the polypyrrole film. On the other hand, the speed of the actuators 1 can be increased by decreasing the layer thickness.

The suitable polypyrroles contain polyanionic immobile dopants and therefore swell by cation influx upon electrochemical reduction at around (-0.8 V vs. Ag/AgCI) and shrink upon oxidation (at around 0 V vs. Ag/AgCI): Oxidized, positively charged polypyrrole cation PPy⁺ can be reversibly reduced into neutral polypyrrole PPy⁰. The immobile dopant uncompensated charge is balanced by alkali metal cations and their hydration shell entering the polypyrrole from the electrolyte. Thus the electroactive material expands upon reduction. The reversible oxidation reaction from PPy⁰ to PPy⁺ forces the cations to flow out of the material. Thus the material shrinks upon oxidation.

Suitable substrate materials for electrically conductive substrates 2 are physically or chemically applied, sufficiently electrochemically stable materials such as gold, titanium, platinum, metals and carbon.

The flexible backing layer 3 serves to stabilize the electrochemical actuator 1 mechanically and to transfer the electrochemically induced stress and strain into bending motion of the device. The backing material should be dimensioned to minimally consume the generated mechanical energy (the force output) of the actuator. Each actuator element 1 is preferably embedded into the soft lens material 4. The interior space 5 of the lens consist either of the same soft elastomer or it is filled with an electrolyte solution or electrolyte gel serving as an ion source for the electrochemical actuator elements 1.

In one embodiment the actuator 1 is embedded into the lens by first polymerizing the ionic polymer gel in-situ into the lens shaped mold containing the actuator array and the necessary electrical components and thereafter encapsulating the molded article by the soft elastomer shell. The elastomer shell is preferably molded in a separate process into an optically optimal shape.

The electrochemical potentials below are in reference to a standard Ag/AgCI electrode. In the conventional three-electrode operation mode the potential of the polypyrrole layer must be well defined (by a reference electrode) and the electrical current for the electrochemical reactions is drawn from an auxiliary current injecting electrode.

Practically applied, the actuator array is preferably working in two electrode mode i.e. the circuit driving the actuators is connected either to an auxiliary electrode 6 with serves both as a current source and a pseudo-reference electrode (bilayer mode) or to another polypyrrole actuator array, galvanically separated from the first array (trilayer mode). The auxiliary electrode 6 can be positioned in several ways in proximity to the polypyrrole actuators, only (i) it has to be part of the electrochemical cell comprising the actuators 1 and the working electrolyte, and (ii) it must have surface area equal of greater than the polypyrrole coated electrode. In the three layer structure the two counteracting layers of polypyrrole should have matching surface areas.

When a -0.5 to -1.2 Volts negative potential difference is applied between the actuator elements 1 and the auxiliary electrode 6, the polypyrrole layer reduces and swells. The swelling generates a bending moment in the order on 1 mN-cm on each actuator elements which forces the lens structure to deform. Likewise, a positive potential causes the actuator 1 to its original shape. The oxidized shape is thermodynamically more stable i.e. the system will slowly return into it without a negative hold-bias voltage. Holding the actuator 1 in either oxidized or reduced state does not draw considerable electrical current.

The momentary charge injected during the reduction and the oxidation, slightly dependent on the morphology and the geometry of the whole actuator array is in the order of 100-200 mC/10^"3 cm³ for 10 μm polypyrrole films.

Based on the injected charge, for a 0.2 cm² 10 μm actuator array each actuation over a period of one second draws an average current of approximately 20-40 mA. Thus the power drawn from the driving circuit is about 20-40 mW.

In the case of trilayer actuator elements, the 0.5-1.2 V potential window of operation is chosen so that the charges injected on both polarities are equal. This ensures that the full capacity of the both polypyrrole layers are utilized: while the other layer, in more positive potential, oxidizes fully, the other which is in more negative potential, is fully reduced. Thus the net force generated by the trilayer actuator is the sum of the force components of the both layers.

Example 2.

Actuator mechanism based directly on the volumetric swelling of a polypyrrole layer

The materials and electrochemical principles of the example 1 can be further applied in different mechanisms based on partially restricted volumetric expansion of polypyrrole. Volumetric expansion of as high as 30-50% for certain cation exchanging polypyrroles can be utilized for example in a mechanism of Figs. 3a and 3b that amplifies and transfers the mechanical energy of the deformation into the soft lens structure. The electroactive material e.g. PPy(DBS) is enclosed in a space that allows expansion in only one spatial dimension only.

The expanding polypyrrole layer 7 is enclosed partially in a supporting ring 8 extending along the outer periphery of the lens. The supporting ring 8 may be made of the same material as described earlier in connection with the flexible backing layer 3. The supporting ring 8 may be discontinuous in such a manner that it could be bent. For example, the supporting ring 8 may comprise sectors which are separated from each other. The supporting ring 8 itself has rigid support in the periphery of the lens body. Attached to the outer part of the supporting ring 8 are arrays of radially extending rigid benders 9 which are embedded in the lens in their outer parts. The benders 9 comprise a flexible backing material on which the metallic layer and the polypyrrole layer are situated. The inner part of the benders 9 can move freely inside the lens interior when actuated by the expanding polypyrrole ring 7. The swelling of the polypyrrole now generates a constant stress, analogous to hydrostatic- or osmotic pressure to the contact area. The stress (force density) acting on the rigid benders 9 in the contact area is typically in the order of 3-5 MPa.

The advantages of volumetric expansion is that (i) the actuator is utilizing all the energy available from the expansion work and (ii) the actuator structure is very robust, e.g. free from delamination problems sometime problematic in layered bending actuators. Possible downsides of the design are that the range of motion and the actuator speed are limited compared to the bilayer and trilayer designs of the example 1.

Example 3.

Linear ring actuator

In another design the electrochemical expansion is utilized in creating linear motion. Figs. 2a and 2b present a mechanism consisting of linear actuators 10 in series embedded in the soft lens material. The linear array of the actuator elements forms a closed loop around the optical aperture of the lens. Linear actuator elements 10 based on polypyrrole are described in the following:

An actuator element 10 can consist of a compliant metal support e.g. a spiral wound thin metal wire and the conductive polymer filling the space between the turns of the compliant structure. Such compliant structures of spiral wound helical platinum wires and electropolymerized polypyrrole have been described earlier by Ding et Al (J. Ding, L. Liu, G. M. Spinks, D. Zhou, G. G. Wallace and J. Gillespie, Synth. Met. 138 (2003), pp. 391-398.). Upon swelling and contracting of the conductive polymer, the element produces linear motion. The spiral wound wire acts as a counteracting spring load and stabilises the actuator element 10 mechanically. The achievable stress output and actuation strain from such an element are about 2% isotonic strain at 0-5 MPa applied stress. In a slightly different design, utilizing the same idea, described in detail by Bay et Al. (Advanced Materials,Volume 15, Issue 4, 2003, Pages: 310-313 L. Bay, K. West, P. Sommer-Larsen, S. Skaarup, M. Benslimane) a polypyrrole film is simply coated with thin corrugated, elastic layer of metal. Such device is capable of producing a large linear 12% strain (at 0.5 MPa stress).

Connecting one or several above described actuator elements mechanically into a ring and embedding the ring into the periphery of the soft optical part of an IOL, concentrically to the optical axis as shown in the Figures, produces a structure capable of changing its refractive power upon electrical stimulus.

Common features of various embodiments

The electrically conductive material capable of dimensional change upon electrical stimulus and forming part of the actuator is in contact with an electrolyte when the actuator is integrated in the IOL and the IOL is in its place in the eye after the surgical operation. Electrolyte is inherently present in eye environment as physiological fluid, and this fluid can act as said electrolyte. This is possible if the actuators are attached on the outer surface of the implant. The interior of the implant may also be provided with an electrolyte, and it can enter in contact with the material of the actuator if the actuator is attached on the inner surface of the implant. If the actuator is embedded in the implant, the electrolyte must be able to diffuse through the material of the implant to contact with the material of the actuator from outside or inside the implant.

Example of a surgical operation where the IOL implant according to the invention can be used

The surgical measure for replacing the native lens with an IOL implant comprises the following steps in a summary: - making a small incision smaller than 3 mm through cornea or limbus - performing an opening in the lens capsule containing the native lens

- disintegrating the native lens inside the capsule and removing the disintegrated lens from inside the capsule through the opening while leaving the capsule in its place, folding an intraocular implant to a folded state,

- inserting the intraocular implant to the inside of the capsule through the small incision and opening in the folded state, and

- allowing the implant to expand from the folded state inside the capsule.

In the modern cataract surgery the hazy lens is removed by using a high speed oscillating ultrasonic probe inserted in a handpiece with infusion and aspiration system. For the handpiece the surgeon is making a small incision (<3mm) either in the clear cornea or corneoscleral limbus. In many cases an other small incision is made for the second instrument. A circular opening to the anterior lens capsule is performed. The ultrasonic probe head is inserted into the eye and into the lens and used to split the hard nucleus of the lens into small pieces, which are aspirated out of the eye. The cortex is removed by using an irrigation- aspiration hand piece. The thin lens capsule that is attached via the zonular fibers to the ciliary body is left otherwise intact and is forming a capsular bag with a circular anterior opening. An intraocular lens with refractive power selected on the basis of the biometrical calculations is folded by using forceps or an injector and inserted into the eye through the small incision and finally allowed to open into the capsular bag. During the operation the sensitive structures of the eye are protected with viscoelastic agents. Viscoelastics are aspirated out of the eye at the end of the operation.

The implant to be mounted in a folded state is a solution enabling a cataract surgery where a required incision could be a much smaller due to that folded state of the implant. Smaller incision heals faster, induces less refractive changes, needs no stitches and stresses an eye less. In addition, integrated actuators that are embedded in the lens keeps the implant cleaner

In the following, the transmission system for bringing about a change in the refractive properties of the IOL is described in more detailed with reference to the enclosed Fig. 4, which shows one example of a possible coupling between the IOL and the external means for controlling the refractive properties of the IOL. The example of the Fig. 4 presents the essential blocks of implanted electronics: receiving circuit, the rectifying and regulating circuits and the connections to the electrochemical actuator array and the internal reference electrode. The essential circuitry can be further coupled to the sensory and reverse telemetry circuits. The sensors may provide means to measure the physiological signals from the eye, such as activation of the ciliary muscle, or the shape of the IOL implant. Such sensory signals are useful in closed loop control of the device. The reverse telemetry may further involve sending back data from the receiver circuits to the driving electronics located outside the patient. The reverse telemetry information is useful in controlling the transmitted power for the device.

Claims

Claims:

1. A foldable intraocular lens implant, the implant comprising an optical part and a non-optical part, wherein the implant comprises means for altering the refractive properties of the implant and the means for altering the refractive properties of the implant being adapted to react to an electric signal and wherein the means are integrated into the implant.

2. The implant according to claim 1 , wherein the means for altering the refractive properties of the implant are integrated by attaching the means to the outer surface of the optical part of the implant.

3. The implant according to claim 1 , wherein the means for altering the refractive properties of the implant are integrated by attaching the means to the junction of the optical part and haptics of the implant.

4. The implant according to claim 1 , wherein the means for altering the refractive properties of the implant are integrated by embedding the means in the optical part of the implant.

5. The implant according to claim 1 , wherein the means for altering the refractive properties of the implant are situated in the non-optical part of the implant.

6. The implant according to any preceding claim, wherein the implant is configured to be mounted in a folded state.

7. The implant according to claim 1 , wherein

- the means for altering the refractive properties are actuator elements integrated into the foldable optical part of the implant,

- actuator elements are arranged in the outer region of the optical part of the implant, and - the optical part of the lens implant is foldable to a width of at least 20% less than diameter of the optical part of the implant.

8. The implant according to claim 7, wherein the actuator elements comprise substance capable of reversible dimensional changes upon electrical stimulus.

9 The implant according to claim 8, wherein said actuator elements are electrochemical actuator elements, said substance being capable of reversible dimensional changes in contact with an electrolyte.

10. The implant according to any of the preceding claims 7 to 9, wherein the implant comprises an antenna coil for an electromagnetic link.

11. The implant according to any preceding claim, wherein the means for altering the refractive properties of the implant comprises bending beam type actuator elements (1 ) which are electrically connected in parallel and symmetrically positioned in the non-optical part of the intraocular lens implant.

12. The implant according to claim 1 1 , wherein the bending beam type actuator element (1 ) comprise a flexible backing (3) and at least on one side of the flexible backing (3) an electrically conductive substrate (2) on which an electrically conductive polymer layer is situated.

13. The implant according to claim 12, wherein the electrically conductive polymer layer is made of polypyrrole or poly(3,4-ethylene dioxythiophene).

14. The implant according to any of the preceding claims 1 to 10, wherein the means for altering the refractive properties of the implant comprises an electrically conductive supporting ring (8) and attached to the electrically conductive supporting ring (8) benders (9) which are symmetrically positioned in the non-optical part of the intraocular lens implant.

15. The implant according to claim 14, wherein the electrically conductive supporting ring (8) is made of polypyrrole or poly(3,4-ethylene dioxythiophene).

16. The implant according to any of the preceding claims 1 to 8, wherein the means for altering the refractive properties of the implant comprises an actuator element (10) comprising at least one metallic spring surrounding the non-optical part of the implant, the metallic spring comprising turns between of which there is a filling made of an electrically conductive polymer.

17. The implant according to claim 16, wherein the filling is made of polypyrrole or poly(3,4-ethylene dioxythiophene).