WO2013059195A1

WO2013059195A1 - Methods, apparatus, and system for triggering an accommodative implantable ophthalmic device based on changes in intraocular pressure

Info

Publication number: WO2013059195A1
Application number: PCT/US2012/060426
Authority: WO
Inventors: Richard L. Lindstrom; Eric D. Donnenfeld; Rudy A. Mazzocchi; Amitava Gupta
Original assignee: Elenza, Inc.
Priority date: 2011-10-17
Filing date: 2012-10-16
Publication date: 2013-04-25

Abstract

An implantable ophthalmic device includes a processor and an intraocular pressure sensor. This device can be implanted in the eye of a patient suffering from a deficient accommodative response. The sensor detects changes in intraocular pressure caused by accommodation, convergence, ocular muscle movement, and even disease and transmits a signal representing the pressure change(s) to the processor. The processor determines whether an accommodative trigger is present by analyzing the signal for characteristics of intraocular pressure changes due to accommodation. If the processor determines that an accommodative trigger is present, it actuates a dynamic optical element, such as an electro-active shutter or a lens with a variable focal length, so as to change the eye's effective depth of field or focal length. The resulting change in the effective depth of field or focal length enables the patent to view a near object (e.g., an object within about 6 meters of the patient) in response to the accommodative trigger.

Description

METHODS, APPARATUS, AND SYSTEM FOR TRIGGERING AN ACCOMMODATIVE IMPLANTABLE OPHTHALMIC DEVICE BASED ON CHANGES IN INTRAOCULAR PRESSURE

CROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 61/548,072, filed on October 17, 201 1, which is entitled "In-Situ Measurement of Intraocular Pressure to Trigger a Dynamic Optic in an Intraocular Lens," and is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Accommodation is the process by which an eye focuses an image of an object at near distance, e.g., less than six feet away. Accommodation occurs in response to an

"accommodative impulse," which is the intent or desire to focus on a near object. The accommodative impulse follows an accommodative stimulus, which is any detectable event or set of circumstances correlated to an accommodative impulse or accommodative response. Exemplary accommodative stimuli include, but are not limited to, physiological cues (such as pupil constriction and other natural accommodative responses) and environmental cues (such as ambient lighting conditions).

[0003] The accommodative impulse is followed by one or more physical or physiological events, known as the accommodative response, that enhance near vision. Natural

accommodative responses (those that occur naturally in vivo) include, but are not limited to, ciliary muscle contraction, zonule movement, alteration of lens shape, iris sphincter contraction, pupil constriction, and convergence. The accommodative response (also known as the accommodative loop) includes at least three involuntary ocular responses: (1 ) ciliary muscle contraction, (2) iris sphincter contraction (pupil constriction increases depth of focus), and (3) convergence (looking inward enables binocular fusion at the object plane for maximum binocular summation and best stereoscopic vision). Ciliary muscle contraction is related to accommodation per se: the changing optical power of the lens. Pupil constriction and convergence relate to pseudo-accommodation; they do not affect the optical power of the lens, but they nevertheless enhance near-object focusing. [0004] In a healthy eye, the accommodative response quickly follows the accommodative impulse. Unfortunately, the accommodative amplitude decreases with age, leading to a degradation or complete loss in the ability to focus on near objects. The loss of ability to focus on near objects is called presbyopia. In a presbyopic eye, the accommodative impulse may be followed by a sub-optimal or absent accommodative response. This degradation or loss of the accommodative response makes it difficult or impossible to focus on near objects.

[0005] The natural lens can be replaced or supplemented with an artificial lens to enhance near vision. For example, many presbyopes use reading glasses or bifocals to view near objects. But reading glasses and bifocals are inconvenient because they do not provide any accommodation; rather, the user accommodates by putting the glasses on. Static intraocular lenses do not provide accommodation either because their focal lengths are fixed.

[0006] Many prior attempts to achieve an accommodative intraocular lens have also proved unsatisfactory. These prior accommodative intraocular lenses have relied upon unreliable triggers that may give a false positive or false negative signal for accommodation. That is, these prior accommodative intraocular lenses may signal for near vision when a near vision task is not present, or they may fail to signal for near vision when a near vision task is present.

SUMMARY

[0007] Embodiments of the present disclosure include methods of detecting the presence of accommodative trigger based on a change in intraocular pressure and corresponding implantable ophthalmic devices. In one example, an implantable ophthalmic device comprises an intraocular pressure sensor and a signal processor operably coupled to the intraocular pressure sensor. The intraocular pressure sensor measures a change in intraocular pressure, and the processor determines the presence of an accommodative trigger based on the change in intraocular pressure.

[0008] In some cases, the intraocular pressure sensor includes or defines a surface that moves in response to a change in intraocular pressure and a displacement sensor configured to measure the surface's movement. For instance, the surface may deform, displace, or both deform and displace in response to a change in intraocular pressure. The displacement sensor provides a signal representative of the surface's movement to processor, which evaluates whether or not an accommodative trigger is present based on the signal.

[0009] An exemplary intraocular pressure sensor may include a piezoelectric actuator that actuates (e.g., vibrates) the surface so as to produce a standing wave along at least a portion of the surface. The displacement sensor measures the surface's movement by sensing a change in the wavelength of this standing wave. Alternatively, the intraocular pressure sensor may include a first conductive material disposed on at least a portion of the surface and a second conductive material disposed opposite the first conductive material. The displacement sensor, which may also include a bridge circuit, may measure the surface's movement by sensing a change in capacitance between the first conductive material and the second conductive material. In another example, the sensor may include a photodetector that senses a change in optical path length through or to the surface, e.g., by measuring a change in position of a beam of light transmitted through or reflected off the surface.

[0010] In some embodiments, the implantable ophthalmic device includes a sealed membrane that defines a cavity, which may be filled with a liquid crystal material. The sealed membrane may also define a surface that moves in response to changes in intraocular pressure. An actuator, operably coupled to the signal processor, changes the liquid crystal material's index of refraction, birefringence, or both in response to the accommodative trigger. For instance, the actuator may include a first electrode, a second electrode, and resistive material. The first and second electrodes may be disposed on a surface of the sealed membrane orthogonal to an optical axis of the implantable ophthalmic device, and the resistive material may be disposed on the surface of the sealed membrane between the first electrode and the second electrode.

[0011] An exemplary implantable ophthalmic device may also include a foldable membrane that defines a cavity filled with fluid. This foldable membrane can include a wall that defines and a surface that moves in response to changes in intraocular pressure. This wall may be more flexible and/or thinner than the foldable membrane's other walls. The cavity may have an area of about 4.0 mm² to about 36.0 mm² and a thickness of about 3.0 μιτι to about 1000.0 μηι (e.g., about 4.0 μιη to about 50.0 μηι). [0012] Other embodiments of the present disclosure include an implantable ophthalmic device with a sealed membrane, a sensor, a processor, and an actuator. The sealed membrane defines a cavity that is at least partially filled with liquid crystal material. It also includes a flexible wall that defines at least one of its surfaces. A first conductive material is disposed over at least part of this flexible wall, and a second conductive material disposed opposite the first conductive material. The sensor measures a change in capacitance between the first conductive material and the second conductive material due to movement of the surface in response to a change in intraocular pressure. In response to sensing such a capacitance change, the sensor transmits a signal representative of the movement to the processor, which determines whether or not an accommodative trigger is present based on the signal. If an accommodative trigger is present, the processor may trigger the actuator, which applies an electromagnetic potential to the liquid crystal material so as to change the liquid crystal material's index of refraction or birefringence.

[0013] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the following drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain principles of the invention.

[0015] FIGS. 1A, I B, and 1C are plots of changes in intraocular pressure during voluntary blinking, accommodation, and eye movement, respectively.

[0016] FIG. 2 is a plot that illustrates the change in intraocular pressure with

accommodation for myopes and emmetropes.

[0017] FIG.3 illustrates an implantable ophthalmic device with an intraocular pressure sensor coupled to a processor that identifies accommodative stimuli based on intraocular pressure measurements from the intraocular pressure sensor. [0018] FIGS. 4A and 4B illustrate an intraocular pressure sensor with a piezoelectric actuator that produces a standing wave along a surface of the intraocular pressure sensor and a displacement sensor that measures movement of the surface by sensing a change in the wavelength of the standing wave.

[0019] FIG. 5 illustrates an intraocular pressure sensor with a bridge circuit that measures movement of the surface by sensing a change in capacitance between a pair of conductive surfaces.

[0020] FIGS. 6A and 6B illustrate an intraocular pressure sensor with a photosensor that measures changes in optical path length to or through a surface of the intraocular pressure sensor.

DETAILED DESCRIPTION

[0021] Presently preferred embodiments of the invention are illustrated in the drawings. An effort has been made to use the same or like reference numbers to refer to the same or like parts.

[0022] Accommodation and Changes in Intraocular Pressure

[0023] As understood by those of skill in the art, intraocular pressure is the eye's internal pressure. Intraocular pressure is a function of inflow and outflow rates of the aqueous humor and the inner architecture of the anterior chamber of the eye. More specifically, it is regulated by resistance to the flow of aqueous humor through the fine sieve of the trabecular meshwork; contraction or relaxation of the longitudinal muscles of the ciliary body affects the size of the opening in the meshwork. In the elderly, the trabecular meshwork may become sclerotic and obstructed, preventing the aqueous humor from passing out at normal rates and causing an increase in the intraocular pressure. It varies with convergence, accommodation, eye movement, and other muscular operations in the eye. Disease (e.g., glaucoma) may also cause it to change.

[0024] Because intraocular pressure varies with accommodation and convergence, it is a suitable trigger for detecting accommodation and convergence. In the devices described herein, an intraocular pressure sensor detects a change in intraocular pressure and transmits a signal representing that change to a processor. The processor uses the signal from the intraocular to determine whether or not the change in intraocular pressure represents an accommodative trigger (e.g., a physiological event or response correlated with

accommodation). For example, the processor may compare changes in intraocular pressure over time with a characteristic signature or temporal profile indicative of accommodation. If the processor determines that the measured change in intraocular pressure matches or is similar to the characteristic signature, it may in turn determine the presence of an

accommodative trigger. The processor may also use signals from one or more other sensors, including pupillary constriction sensors and Ca²⁺ ion sensors, to confirm the presence of accommodation.

[0025] If the change in intraocular pressure does represent accommodation, the processor actuates an implanted electro-active optical component, such as a lens with a variable focal length or an electro-active shutter. This electro-active optical component responds to the actuation signal by causing the eye's focus, depth of field, or both focus and depth of field to change. Because the intraocular pressure sensor detects accommodative triggers with greater fidelity (e.g., fewer false positive or false negatives), the electro-active optical component can mimic accommodation more accurately.

[0026] FIGS. 1 A-l C are plots of intraocular pressure versus time for the right eye of a 26- year-old man with cycloplegia (paralysis of the ciliary muscle of the eye). FIG. 1 A shows that the intraocular pressure increases by about 5 mm Hg to about 10 mm Hg when the subject blinks voluntarily. FIG. IB shows that intraocular pressure increases by about 2 mm Hg to about 4 mm Hg when the subject focuses on an object about 14 cm away and decreases by a corresponding amount when the subject relaxes and the object is removed. And FIG. 1C shows that the intraocular pressure increases by 5 mm Hg to about 10 mm Hg and remains elevated as the subject moves his right eye to the left, then decreases when he looks straight ahead. These results indicate that intraocular pressure changes in a unique fashion for each of these viewing tasks, including accommodation. Thus, a measurement of intraocular pressure versus time can be used to distinguish accommodation from other viewing tasks, such as blinking, and changes in intraocular pressure due to the onset of disease.

[0027] FIG. 2 is a plot of intraocular pressure measured for myopic (near-sighted) and emmetropic (perfectly sighted) young adults performing a three-dimensional accommodation task. It shows that intraocular pressure falls significantly and by roughly the same amount for both myopes and emmetropes as a result of the accommodation task. More specifically, the mean change in intraocular pressure with accommodation for all subjects is about -1.8 mm Hg with a standard deviation of ±1.1 mm Hg. Error bars represent standard error of the mean. This change in intraocular pressure is highly statistically significant (p < 0.0001). This change in intraocular pressure with accommodation is about the same for the myopes (-1.8 ± 0.8 mm Hg) as it was for the emmetropes (-1.9 ± 1.4 mm Hg, p = 0.8) despite the differences in their baseline intraocular pressures (the mean baseline in the myopes is 17.6 ± 2.0 mm Hg; in the emmetropes, it is 16.8 ± 3.0 mm Hg, p = 0.4). These results show that change in intraocular pressure reliably indicates accommodation in a wide swath of the general population.

[0028] An Implantable Ophthalmic Device with an Intraocular Pressure Sensor

[0029] FIG. 3 shows an implantable ophthalmic device 100, such as an intraocular lens, intraocular optics, corneal inlay, corneal onlay, or other implantable device. The implantable ophthalmic device 100 shown here includes an intraocular pressure sensor 1 10, a processor 120, a dynamic electro-active element 130, an (optional) static optical element 140, and one or more haptics 150. It may be implanted or inserted in the anterior chamber or posterior chamber of the eye (e.g., anterior to the iris), into the capsular sac, or the stroma of the cornea (similar to a corneal inlay), or into the epithelial layer of the cornea (similar to a corneal onlay), or within any anatomical structure of the eye or in any other suitable location in the eye using well-established surgical techniques. Before or during implantation, the device 100 may be rolled, compressed, or folded to fit through a small incision (e.g., a 1.0-2.0 mm incision), then expanded when positioned correctly and secured within the eye using haptics 150 or other suitable anchors. For instance, the device 100 may be folded along a fold line as disclosed in U.S. Patent Application No. 201 1/0015733 to Schnell et ai, which is hereby incorporated herein by reference in its entirety. When implanted, the opaque components (e.g., the processor 120) may be disposed out of the patient's line of sight (e.g., in the vicinity of the haptic/optic junction).

[0030] When implanted, the intraocular pressure sensor 1 10 senses changes in intraocular pressure over time. In some cases, the intraocular pressure includes a surface (FIGS. 4-6) that moves in response to changes in intraocular pressure. For instance, the surface may displace, deform, or otherwise change shape in a repeatable manner as the pressure increases or decreases as described below with respect to FIGS. 4-6. This movement may be correlated with or related to changes in pressure. In some cases, for example, at least a portion of the surface may move by about 1.0 micron in response to a change in intraocular pressure of about 1.0 mm Hg. In these examples, a 2.0 mm Hg pressure increase produces a 2.0-micron movement, a 3.0 mm Hg pressure increase produces a 3.0-micron movement, up to a maximum movement of, e.g., 10.0 microns, 1 1.0 microns, 12.0 microns, 13.0 microns, 14.0 microns, or 15.0 microns. The relationship between movement and pressure change may be based on a model or determined experimentally.

[0031] A displacement sensor in the intraocular pressure sensor measures the surface's displacement and produces a corresponding change in voltage, current, and/or capacitance. Upon sensing this change in voltage, current, and/or capacitance, the intraocular pressure sensor 1 10 (displacement sensor) transmits a signal to the processor 120 via a wired, radio- frequency, optical, or inductive communications link. The processor 120 receives this signal and analyzes it to determine whether or not an accommodative trigger (e.g., an

accommodative stimulus, impulse, or response) is present. The processor 120 may perform this analysis by measuring the magnitude and duration of the intraocular pressure change. For example, the processor 120 may determine that an accommodative trigger is present if the signal from the sensor 1 10 indicates that the pressure has decreased by at least about 1.0 mm Hg (e.g., by about 2.0-5.0 mm Hg) over a period of about 0.5-3.0 seconds.

[0032] The processor 120 may also compare values representing the pressure change to values stored in a non- volatile, non-transitory memory 122 or evaluate the pressure change according to a computer-implementable instructions (e.g., a computer program) stored in the memory 122. For instance, the memory 122 may store calibration data based on the measurements of changes in the patient's intraocular pressure as the patient's eye undergoes accommodation. These calibration data may be stored as amplitude and duration values in a look-up table embodied in the memory 122. They may also be stored as coefficients to be applied to an equation, also stored in the memory 122, that the processor 120 computes in response to and based on the signal from the intraocular pressure sensor 1 10. For more details on suitable processors, see WO 201 1/163080 filed June 17, 2011, and entitled, "ASIC Design and Function," which is incorporated herein by reference in its entirety. [0033] The processor 120 actuates the dynamic electro-active element 130 in response to detection of an accommodative trigger. The dynamic electro-active element 130 responds to this actuation by changing the eye's effective optical power, focal length, depth of field, or a combination thereof so as to cause the eye to focus on a near object. For instance, the dynamic electro-active element 130 may include a liquid-crystal device that occludes some or all of the eye's field of view so as to increase the depth of field (as shown in FIG. 3) as described in U.S. Patent No. 7,926,940 to Blum et al., which is incorporated herein by reference in its entirety. Such a liquid-crystal device may include birefringent liquid crystal material sandwiched between a pair of substrates, each of which is coated with at least one transparent electrode (e.g., an indium tin oxide electrode) and, optionally, a polarizing film. Applying an electric potential across the transparent electrodes causes the liquid crystals to re- align themselves, which in turn changes the material's birefringence. In some examples, the liquid crystal material is sandwiched between a pair of polarizers, so this change in birefringence leads to a change in the electro-active element's transmissivity. In other examples, the re-alignment causes the electro-active element's index of refraction to change without necessarily changing its birefringence.

[0034] For instance, the dynamic electro-active element 130 may include a single pair of opposing electrodes which can be actuated in a binary fashion (e.g., on/off) to open and close a shutter. That is, when the device is actuated, it defines a clear aperture with a first diameter, and when it is not actuated, it defines a clear aperture with a second (larger) diameter, or vice versa. Stopping down the aperture increases the depth of field, improving the subject's ability to focus on the nearly object. Alternatively, the liquid crystal device may include a plurality of electrodes, each of which defines part of an individual pixel. The electrodes may be patterned in any suitable shape, e.g., quadrilaterals, hexagons, triangles, wedges, and/or complete or partial annular sections (rings). These pixels can be addressed individually so as to define clear apertures of varying sizes, shapes, and positions. As understood by those of skill in the art, changing the transmissivity and/or refractive index of some or all of the pixels may cause the electro-active element 130 to diffract incident light so as change the eye's effective optical power (focal length).

[0035] Alternatively, or in addition, the dynamic electro-active element 130 may also include a lens element or other optical element whose shape changes so as to change the eye's effective focal length. Such a lens element may be formed of a flexible, fluid-filled membrane actuated by a heater or electrode. Heating or applying an electromagnetic potential to the fluid inside the membrane causes the fluid to expand (e.g., by undergoing a phase transition), which in turn causes at least part of the membrane to bulge outwards. This bulge causes the membrane's radius of curvature to change, resulting in a change in the

membrane's focal length as described in WO 2012/067994, "Adaptive Intraocular Lens," which is incorporated herein by reference in its entirety.

[0036] In some cases, the dynamic electro-active element 130 may be in optical

communication with a static optical element 140, such as a lens, prism, diffractive element, or optical flat. For instance, the static optical element 140 may include a lens that provides a base optical power of anywhere from 1.0 Diopters to about 35.0 Diopters (e.g., 5.0 Diopters, 10.0 Diopters, 15.0 Diopters, 20.0 Diopters, 25.0 Diopters, or 30.0 Diopters). This lens may be spherical or aspheric as desired. Together, the dynamic electro-active element 130 and the static optical element 140 may provide an optical power that varies by about 0.5-5.0 Diopters (e.g., 1.0 Diopters, 1.5 Diopters, 2.0 Diopters, or 2.5 Diopters) from the base optical power provided by the static optical element 140.

[0037] The dynamic electro-active element 130 may also include one or more deformable haptics that move a static or dynamic lens element (e.g., static optical element 140) along the eye's optical axis so as to change the eye's effective optical power. For instance, the haptics may be at least partially formed of temperature-sensitive shape-memory alloy that changes shape when heated above a certain critical temperature. As the haptics change shape, they may move the lens element along the eye's optical axis so to increase the eye's effective focal length, as explained in greater detail in PCT/US201 1/067516, "Intraocular Lens with

Dynamic Focusing Movement," which is incorporated by reference herein in its entirety.

[0038] The implantable ophthalmic device 100 may also include one or more additional sensors (not shown) to provide further indications of accommodation, including leading indicators of accommodation, lagging indicators of accommodation, or both. The processor 120 may receive signals from these additional sensors and may use them to distinguish changes in intraocular pressure due to accommodation from other causes of intraocular pressure changes. For instance, the processor 120 may count "votes" from two or more different types of sensor, including the intraocular pressure sensor 1 10, and it may determine that an accommodative trigger is present based on a majority of the sensors' "votes." These additional sensors also provide redundancy in case any one sensor fails. Suitable additional sensors include photosensors to detect pupil constriction and/or ambient light levels as disclosed in WO 2012/037019 filed September 12, 201 1 , and entitled, "Method and

Apparatus for Detecting Accommodations," which is incorporated herein by reference in its entirety. Other suitable sensors include ion sensors like those disclosed in U.S. Patent Application Publication No. 2010/0004741 filed July 2, 2009, and entitled, "Sensor for Detecting Accommodative Trigger," which also is incorporated herein by reference in its entirety.

[0039] The implantable ophthalmic device 100 may also include a battery, solar cell, or other power source (not shown) that provides power to the intraocular pressure sensor 1 10, the processor 120, and/or the electro -active element 130. For instance, the device 100 may include one or more sealed, rechargeable batteries such as those disclosed in

WO 2012/033752 filed September 6, 201 1 , and entitled, "Installation and Sealing of a Battery on a Thin Glass Wafer to Supply Power to an Intraocular Implant," which is incorporated herein by reference in its entirety. Such batteries may be recharged using an inductive coil that also serves as an antenna to transmit and receive data as well as instructions to or from the processor 120. Components within the implantable ophthalmic device 100 and/or the device 100 itself may be hermetically sealed so as to reduce the likelihood of leaks that might affect the eye or the patient's eye, e.g., as described in WO 2012/033752 and

WO 201 1/163080.

[0040] Standing- Wave Intraocular Pressure Sensor

[0041] FIG. 4A illustrates a standing-wave intraocular pressure sensor 210 suitable for detecting changes in intraocular pressure indicative of accommodative triggers. It includes a frame 218 that supports a flexible membrane 214 made of polyvinylidene fluoride (PVDF); fluorocarbon (e.g., Tedlar^® or ynar^®), polyimide (e.g., Kapton^®), or any other suitable biocompatible material. The membrane 214 is about 2.0-10.0 microns thick (e.g., 5.0 microns thick) and defines a surface 212 that moves by up to about 10 microns in response to changes in intraocular pressure. For instance, the surface 212 may move by about 0.5 microns to about 1.5 microns (e.g., 1.0 microns) for every 1.0 mm Hg change in intraocular pressure (e.g., a 2.0-micron movement for a 2.0 mm Hg pressure change, a 3.0-micron movement for a 2.0 mm Hg change in intraocular pressure, and so on).

[0042] The standing-wave intraocular pressure sensor 210 also includes a piezoelectric actuator 216 coupled between the membrane 214 and the frame 218 and a driver circuit 220 coupled to the piezoelectric actuator 216. (It may also include a capacitive actuator instead of or in addition to the piezoelectric actuator 216.) The driver circuit 220 applies a voltage to the piezoelectric actuator 216; this causes the actuator 216 to expand and contract, which in turn causes the membrane 214 to expand and contract as well. This expansion and contraction sets up a standing wave 21 1 of mechanical oscillations along the width of the membrane 214 at a wavelength λ determined, in part, by the oscillation frequency and the length of the membrane 214. In some examples, the frequency of the standing wave is 10 cm ¹ to 1000 cm ¹ (e.g., 50 cm^"1, 100 an^{" 1}, 250 cm^"1, 500 cm^"1, or 750 cm^"1).

[0043] FIG. 4B illustrates the standing wave intraocular pressure sensor 210 responding to a change in intraocular pressure associated with an accommodative trigger. This pressure change causes the surface 212 to sag or displace by an amount 213 proportional to the pressure change's magnitude. It also causes the membrane 214 to stretch, which in turn increases the length of the surface 212. And, in turn, this length change causes the

wavelength λ' (and frequency) of the standing wave 21 1 ' to change by an amount proportional to magnitude of the intraocular pressure change. In addition to driving the piezoelectric actuator 216, the driver circuit 220 acts as a displacement sensor that senses this change in wavelength (and, by extension, the movement of the surface 212) as a detuning that can be measured as a change in voltage or current. In other words, when the surface 212 shifts, the piezoelectric actuator 216 absorbs energy, and the driver circuit 220 detects this absorbed energy.

[0044] In alternative embodiments (not shown), the membrane 214 may define one wall or one section of a sealed membrane filled with fluid. This fluid may be a transparent, biocompatible substance, such as saline, silicone oil, or liquid crystal material (e.g., as described with respect to FIG. 7). This fluid may be at a pressure about equal to baseline intraocular pressure (e.g., about 16.0-17.0 mm Hg) to resist changes in intraocular pressure. The membrane 214 may be thinner and/or more flexible than the other walls of the sealed membrane to increase the sensor's sensitivity to intraocular pressure changes. [0045] Capacitive Intraocular Pressure Sensor

[0046] FIG. 5 shows a capacitive intraocular pressure sensor 310 suitable for detecting changes in intraocular pressure indicative of accommodative triggers. The capacitive intraocular pressure sensor 310 comprises a sealed membrane made of PVDF, fluorocarbon, polyimide, or any other suitable biocompatible material. The membrane is formed into a thinner, more flexible section 314 and a thicker, more rigid section 324. When the sensor 310 is implanted in the eye, one surface 312 of the more flexible section 314 responds to changes in intraocular pressure by moving back and forth, sagging, displacing, deforming, or otherwise changing shape or position as described above.

[0047] Together, the sections 314 and 324 form a optical cavity that can be implanted facing the iris. The cavity's interior surface includes a polygonal, elliptical, or circular area of about 4.0-36.0 mm² (e.g., 10.0 mm², 20.0 mm², or 30.0 mm²) on the sections 314 and 324. This area may be bounded by a square of about 2.0 mm ^χ 2.0 mm to about 6.0 mm ^χ 6.0 mm. The cavity's baseline depth, which is the distance separating the sections 314 and 324, may be about 3 microns to about 1000 microns (e.g., about 4-50 microns) at baseline intraocular pressure. The cavity may be filled with a transparent, biocompatible liquid, such as silicone oil, saline, or liquid crystal as described in greater detail below.

[0048] The capacitive intraocular pressure sensor 310 also includes conductive material 316 coated over at least a portion of the thinner, more flexible section 314 and more conductive material 326 coated over at least a portion of the thicker, more rigid section 324. The conductive material 316, 326 may coated on the outside of the membrane sections, deposited on the inside of the membrane sections, or embedded within the membrane sections or between layers of the membrane sections. The conductive material 316, 326 may include or be formed of an extremely thin layer of metal, such as gold or silver, or transparent oxide, such as indium tin oxide (ITO), Sn0₂, ZnO, and/or Zn0₂. If the sensor 310 is outside the patient's line of sight, the conductive material 316, 326 may be opaque or only partially transmitting.

[0049] In operation, charge accumulates between the conductive material 316 on the thinner, more flexible section 314 and the conductive material 326 on the thicker, more rigid section 324. As a result, the two pieces of conductive material 316, 326 act as a parallel plate capacitor whose capacitance is inversely proportional to the distance separating the two pieces of conductive material 316, 326. Changes in intraocular pressure cause the more flexible section 314 (and conductive material 316) to move towards or away from the more rigid section 324 (and conductive material 326), which in turn causes this capacitance to change. For instance, the capacitance may change by about 0.5% to about 2.5% (e.g., 1.0%) of the base capacitance, or about 0.5 pF to about 2.5 pF (e.g., 1.0 pF), in response to a pressure change of about 1.0 mm Hg.

[0050] The sensor 310 also includes a capacitance bridge circuit 320 or any other suitable capacitance-based displacement sensor senses this change in capacitance and provides an indication of the capacitance change to a processor (e.g., processor 120), which determines whether an accommodative trigger is present or not based on the indication. As understood by those of skill in the art, the capacitance bridge circuit 320 has two circuit branches (usually in parallel with each other) that are bridged by a third branch connected between the first two branches. The two pieces of conductive material 316, 326 are inserted into the bridge circuit 320 and the capacitance values of the other legs of the bridge circuit 320 are varied so as to bring the bridge into balance, thereby providing the capacitance between the conductive materials 316 and 326.

[0051] Those of skill in the art will readily appreciate that the surface 312 may be defined by a membrane that does not enclose an optical cavity. Rather, the membrane could be attached to a frame, and the second conductive material 326 could be disposed on the frame or another member whose position does not change in response to changes in intraocular pressure. Alternatively, the pieces of conductive material 316, 326 could be disposed on opposing surfaces that move towards each other when pressure increases and away from each other when pressure decreases or vice versa.

[0052] Liquid-Crystal-Filled Intraocular Pressure Sensor

[0053] In some cases, the fluid 318 inside the cavity comprises liquid crystal polymer material. The liquid crystal polymer may enhances the sensor's response to intraocular pressure changes compared to silicon or other pressure-sensitive ceramics or metals because since the polymer exhibits a greater deflection to stresses than those other materials. It also allows the sensor 310 to combine the functions of the intraocular pressure sensor 1 10 and the dynamic electro-active element 140 shown in FIG. 3. In other words, an intraocular pressure sensor comprising a cavity filled with liquid-crystal polymer (e.g., sensor 310) can both sense and respond to accommodative triggers. The sensor 310 can be used with other sensors, including photosensors and ion sensors, and with additional static and/or dynamic optical elements, including fixed lenses, lenses with variable focal lengths, switchable diffractive elements, dynamic shutters, etc.

[0054] In certain embodiments, the conductive material 316 and/or 326 is patterned or segmented to provide a plurality of electrodes, each of which is associated with a

corresponding pixel. These pixels may have any suitable shape (e.g., quadrilaterals, annular sections, wedges, triangles, hexagons, etc.) and can be distributed on a regular or irregular grid. An actuator 322 applies an electromagnetic potential across a particular pair of electrodes causes the liquid crystals positioned between the electrodes to align themselves in a particular direction, e.g., with the field vector of the electromagnetic potential. This may induce a birefringence change in the liquid-crystal material; if the liquid-crystal material is positioned between a pair of polarizers (not shown), this birefringence results in a change in the pixel's transmissivity. Alternatively, the electromagnetic potential may cause the liquid- crystal material's refractive index and/or transmissivity to change. The pixels may be separated by resistive layers and actuated independently by a processor (e.g., processor 120 in FIG. 3) or other microcontroller. Actuated pixels (rings) attenuate or reflect incident light and unactuated pixels transmit at least some of the incident light. In some cases, the pixels defining the aperture's edge may be tuned to partially transmit light so as to apodize the aperture.

[0055] For instance, the pixels may form a series of concentric annular electrodes arranged to provide a clear aperture. When implanted, the liquid-crystal-filled sensor 310 may be oriented such that the surface 312 (and by extension, the sections 314 and 324) are substantially orthogonal to the eye's optical axis. In this orientation, the concentric, ring-like pixels form a clear aperture whose diameter can be varied depending on the desired depth of focus. In this embodiment, actuating the ring-like pixels so as to open or stop down the clear aperture can provide a change in the eye's optical power of up to about 5.0 Diopters (e.g., 1.0 Diopters, 2.0 Diopters, 3.0 Diopters, or 4.0 Diopters). [0056] Optical Intraocular Pressure Sensor

[0057] FIGS. 6A and 6B illustrate an optical intraocular pressure sensor 410 suitable for detecting accommodative triggers in an implantable ophthalmic device. Like the sensor 310 shown in FIG. 3, the sensor 410 shown in FIG. 4 comprises a sealed membrane formed by two or more sections 414 and 424 of PVDF, fluorocarbon, polyimide, or other suitable biocompatible material. The sealed membrane may be filled with any suitable biocompatible liquid, including liquid-crystal polymer, which can be actuated with electrodes (not shown) so as to provide a change in the eye's effective optical power as explained above. One section 414 of the membrane may be thinner and more flexible than the other section 424, allowing the sensor 410 to be folded, rolled, or otherwise compressed for implantation in the eye via a narrow incision and unfolded, unrolled, or otherwise expanded once positioned within the eye.

[0058] Like the other sensors disclosed herein, the optical intraocular pressure sensor 410 includes a surface 412 that moves in response to changes in intraocular pressure. One or more photosensors 420 monitor the surface's movement by detecting the light transmitted through the sensor 410 and transmitting signals (e.g., photocurrent) to a processor (e.g., processor 120 in FIG. 3) representative of the detected light. The processor 120 forms an image based on the received signals and determines the surface's position based on the quality of the image. Alternatively, or in addition, an opaque portion (not shown) of the surface 412 may occlude some or all of the photodetectors 420 as a function of the surface's position. For instance, at normal (baseline) intraocular pressure, the opaque portion of the surface 412 may not occlude any of the photodetectors 420. A 1.0 mm Hg decrease in the intraocular pressure may cause the surface's opaque section to occlude 10% of the total photodetector 420 area, resulting in a 10% reduction in the signal strength. (Similarly, a 20% reduction in signal strength may correspond to a 2.0 mm Hg change in intraocular pressure, etc.) The processor 120 may sense this reduction in signal strength along with signals from other sensors (e.g., an ambient light sensor) and consequently determine that the intraocular pressure has changed.

[0059] The optical intraocular pressure sensor 410 may also include an infrared light source 430, such as a light-emitting diode (LED), configured to transmit infrared light through or within the optical cavity formed by the membrane. The light refracts through or reflects off the more flexible membrane section 414 towards the photodetectors 420, which detect the refracted or reflected infrared light. The photodetectors 420 produce a signal, such as a photocurrent, in response to the detected light and transmit this signal to the processor.

Depending on the sensor's layout, the strength of this signal represents the optical path length through or to the optical cavity. Changes in intraocular pressure cause the surface 412 (and section 414) to move, which in turn causes this optical path length to change.

[0060] For example, under baseline intraocular pressure, the more flexible section 414 may reflect infrared light 431 from the LED 430 to the photodetectors 420. Decreasing the intraocular pressure causes the more flexible section 414 to move away from the less flexible section 424, which causes the cavity to expand. This in turn causes the infrared beam 431 ' from the LED 430 propagate farther before striking the more flexible section's inner surface, which in turn causes the beam 43 Γ to mvoe away from the photodetectors 420. This shift in the beam's position causes the amplitudes of photodetectors' outputs to change accordingly (some photodetectors 420 detect less light and emit weaker signals; other photodetectors 420 detect more light and emit stronger signals). In other words, movement of the surface 412 modulates amplitude and/or position the beam of light detected by the photodetectors. The processor senses these changes in amplitude and determines, accordingly, that the intraocular pressure has changed or is changing.

[0061] Conclusion

[0062] It should be appreciated that all combinations of the concepts disclosed herein (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter in this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0063] The use of flow diagrams is not meant to be limiting with respect to the order of operations performed. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected", or "operably coupled", to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable", to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

[0064] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[0065] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations.

[0066] However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).

[0067] Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.).

[0068] It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0069] The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. An implantable ophthalmic device comprising:

an intraocular pressure sensor configured to measure a change in intraocular pressure; and

a signal processor, operably coupled to the intraocular pressure sensor, configured to determine the presence of an accommodative trigger based on the change in intraocular pressure.

2. The implantable ophthalmic device of claim 1 , wherein the intraocular pressure sensor comprises:

a surface configured to move in response to a change in intraocular pressure; and a displacement sensor configured to measure movement of the surface and to provide a signal representative of the movement of the surface.

3. The implantable ophthalmic device of claim 2 wherein the surface is configured to deform in response to a change in intraocular pressure.

4. The implantable ophthalmic device of claim 2 wherein the surface is configured to displace in response to a change in intraocular pressure.

5. The implantable ophthalmic device of claim 2 further comprising:

a piezoelectric actuator configured to actuate the surface so as to produce a standing wave along at least a portion of the surface, and

wherein the displacement sensor is configured to measure the movement by sensing a change in the wavelength of the standing wave.

6. The implantable ophthalmic device of claim 2 furthering comprising:

a first conductive material disposed on at least a portion of the surface;

a second conductive material disposed opposite the first conductive material, and wherein the displacement sensor is configured to measure the movement by sensing a change in capacitance between the first conductive material and the second conductive material.

7. The implantable ophthalmic device of claim 6 wherein the displacement sensor comprises a bridge circuit configured to measure the change in capacitance.

8. The implantable ophthalmic device of claim 2 wherein the displacement sensor comprises a photodetector configured to sense a change in optical path length through or to the surface.

9. The implantable ophthalmic device of claim 2, further comprising:

a sealed membrane defining a cavity filled with a liquid crystal material, the sealed membrane defining the surface; and

an actuator, operably coupled to the signal processor, configured to change at least one of an index of refraction of the liquid crystal material and a birefringence of the liquid crystal material in response to the accommodative trigger.

10. The implantable ophthalmic device of claim 9 wherein the actuator comprises:

a first electrode disposed on a surface of the sealed membrane orthogonal to an optical axis of the implantable ophthalmic device; and

a second electrode disposed on the surface of the sealed membrane orthogonal to the optical axis of the implantable ophthalmic device.

1 1. The implantable ophthalmic device of claim 9 wherein the cavity has an area of about 4.0 mm² to about 36.0 mm².

12. The implantable ophthalmic device of claim 9 wherein the cavity has a thickness of about 3.0 μηι to about 1000.0 μιη.

13. The implantable ophthalmic device of claim 9 wherein the cavity has a thickness of about 4.0 μπι to about 50.0 μηι.

14. The implantable ophthalmic device of claim 2 further comprising:

a foldable membrane defining the surface.

15. The implantable ophthalmic device of claim 14 wherein the foldable membrane comprises a wall that defines the surface and is more flexible than the other walls of the foldable membrane.

16. The implantable ophthalmic device of claim 14 wherein the foldable membrane comprises a wall that defines the surface and is thinner than the other walls of the foldable membrane.

17. A method of sensing an accommodative trigger, the method comprising:

(a) detecting a change in intraocular pressure with an intraocular pressure sensor implanted in an eye; and

(b) determining the presence of the accommodative trigger based on the change in intraocular pressure.

18. The method of claim 17 wherein (a) comprises:

detecting movement of a surface in response to the change in intraocular pressure.

19. The method of claim 18 wherein (a) further comprises:

(i) actuating the surface so as to create a standing wave along at least a portion of the surface; and

(ii) sensing a change in the wavelength of the standing wave caused by the change in intraocular pressure.

20. The method of claim 18 wherein (a) comprises:

measuring a change in capacitance caused by the movement of the surface.

21 . The method of claim 18 wherein (a) comprises:

(i) illuminating the surface with a beam of light; and

(ii) sensing modulation of the beam of light caused by the movement of the

surface.

22. The method of claim 21 wherein (ii) comprises:

detecting light reflected by the surface.

23. The method of claim 21 wherein (ii) comprises:

detecting light transmitted through the surface.

24. The method of claim 17 further comprising: (c) actuating an intraocular optical element in response to the accommodative trigger.

25. The method of claim 24 wherein (c) comprises:

causing a change in at least one of an index of refraction of the liquid crystal material and a birefringence of the liquid crystal material.

26. An implantable ophthalmic device comprising:

a sealed membrane defining a cavity at least partially filled with liquid crystal material, the sealed membrane comprising a flexible wall that defines a surface of the sealed membrane;

a first conductive material disposed over at least part of the flexible wall;

a second conductive material disposed opposite the first conductive material;

a sensor configured to:

(i) measure a change in capacitance between the first conductive material and the second conductive material due to movement of the surface in response to a change in intraocular pressure; and

(ii) provide a signal representative of the movement;

a processor, operably coupled to the sensor, configured to determine the presence of an accommodative trigger based on the signal; and

an actuator, operably coupled to processor, configured to apply an electric potential to the liquid crystal material so as to change an index of refraction of the liquid crystal material in response to the presence of an accommodative trigger.