System for measuring intraocular implants

Abstract

The objective is to provide a technique for measuring intraocular implants. [Solution] An intraocular pressure sensor implant comprising: a substrate defining a surface that can be implanted in the eye; a membrane bonded to the substrate, which is operable to change shape as a function of the intraocular pressure of the eye and defines an active region; and a lens bonded to the substrate, which is operable to focus a light beam onto the active region for measuring intraocular pressure based on the distance between the membrane and the surface.

Description

Technical Field

[0001] The subject matter of the present disclosure relates to techniques for measuring an intraocular implant, and more particularly, to measuring a pressure sensor intraocular implant using the aid of a small lens. Such techniques are useful for treating and / or monitoring the progression of eye diseases including glaucoma, but are not limited to use in connection with the treatment of eye diseases.

Background Art

[0002] Typically, intraocular parameters, such as intraocular pressure (IOP), are measured using a tonometer. A tonometer is a device located outside the eye and therefore does not require a sensor inside the eye. Contact tonometry is performed in a clinical setting, and this procedure requires numbing the patient's eye, resulting in both inconvenience and discomfort. Non-contact tonometry involves directing a puff or jet of air towards the patient's eye and measuring the resulting eye strain dynamics. However, this requires a bulky and power-hungry pump configuration, making it impractical for home use, and is not as accurate as contact tonometry. Furthermore, in some cases, it is desirable to be able to measure such parameters frequently and conveniently at home. For example, in cases of conditions such as glaucoma that cause chronically elevated IOP, treatment primarily involves regularly administering medications to the eye to lower IOP. These medications can be delivered, for example, by injection or eye drops. However, effective treatment of glaucoma requires adherence to medication schedules and knowledge of the patient's IOP (Intraocular Pressure). IOP in a given patient can vary significantly based on time of day, exercise, how recently medication was administered, and other factors. Typically, IOP measurements are performed in a physician's office, often only once or twice a year or less. These infrequent measurements have little capacity to account for the variability in a patient's IOP and can become obsolete due to the length of time between them. This means that any given measurement is uncertain, and therefore, performing several IOP measurements over a period of time can provide reliability in the patient's eye health.

[0003] A wireless, embeddable, continuous IOP monitoring system has been proposed, comprising a commercially available pressure-sensitive element with digital readout, and a small electronic chip supporting wireless power / data telemetry and a wired serial communication interface with the pressure-sensitive element. An on-chip integrated RF coil receives power from near-field RF coupling at 915 MHz and transmits pressure measurement bits to an external reader via RF backscattering. However, to ensure accurate measurements by the external reader, it is crucial that the external reader is precisely aligned with the pressure-sensitive element. [Overview of the project]

[0004] Aspects of this disclosure relate to systems and processes for measuring intraocular parameters from an implant, including miniaturized lenses to reduce positional adjustment sensitivity. In some embodiments, the intraocular parameter to be measured may be the eye's IOP. Typically, in some embodiments, a reader or sensor reading device (a portable, battery-powered electronic device that can be held by the person) is positioned with the eye and a light beam is emitted by a transmitter in the reader. The reader is not physically attached to the sensor and may be outside the eye. The beam travels through free space (the surrounding environment outside the eye) and then enters the cornea, where it may collide with a sensor and be reflected by the sensor toward a receiver in the reader. The reflection changes so that it follows the eye's changing IOP (e.g., over the course of a day). The sensor may be passive in that it does not have a stored power source used to transmit a signal containing information about the IOP. Instead, a portion of the sensor reflecting the incident beam bends or compresses, resulting in a reflection that changes accordingly as a function of the nearby IOP. Next, the estimated IOP is determined by digitally processing the receiver's electrical output signal (responding to reflections that travel from the sensor and then through the surrounding environment before hitting the receiver).

[0005] Precise spatial alignment between the sensor and the reader is necessary to ensure accurate measurements. For example, to perform the measurements in the previously discussed example, a single-point optical interrogation can be used in which a light beam from a handheld device is focused onto a region at the center of the flexible membrane of the implant (having a spot size of approximately 40 μm in diameter). To ensure accurate measurements, angular alignment should be approximately 0.02 degrees or better between the implant and the handheld device. However, such precise alignment requirements can hinder quick, reliable, and user-friendly measurements. Therefore, this disclosure proposes a technique to address the above technical limitations by directly mounting a miniature lens with a very short focal length onto the sensor (implant). In some embodiments, the miniature lens may have a diameter of approximately 74 microns to approximately 125 microns, or approximately 100 microns. Such a miniature lens effectively restricts the optical measurement to only the region close to its focal point. This also enables the use of a collimated (as opposed to a focused) light beam for optical measurements, which can significantly reduce lateral and angular alignment sensitivity. It should be further understood that the techniques proposed herein are not limited to ophthalmic / medical sensing applications but can be used in a much broader range of measurement applications, including the iterative repositioning of miniature sensors and external optical measuring devices. For example, similar techniques may be implemented in applications involving non-contact reading of sensors, or in applications using spectral reflectance measurements, techniques used to determine the thickness of a thin film or the distance between two surfaces by measuring the reflectance spectrum from a sample.

[0006] Typically, in one embodiment, an intraocular pressure sensor implant is provided, comprising: a substrate defining a surface that can be implanted in the eye; a membrane bonded to the substrate, operable to change shape as a function of intraocular pressure in the eye, defining an active region; and a lens bonded to the substrate, operable to focus a light beam into the active region for measuring intraocular pressure based on the distance between the membrane and the surface. In some embodiments, the lens is bonded to the surface of the substrate opposite the membrane. In other embodiments, the lens has a focal length that coincides with the active region. The lens may include a convex lens and / or a miniature lens having a diameter smaller than the diameter of the light beam. In some embodiments, the light beam includes a collimated beam. In some embodiments, the lens is operable to focus a light beam with an angular displacement into the active region. The angular displacement may be greater than 0.02 degrees. The substrate may be a rigid substrate, and the membrane may be a flexible membrane that jointly defines a cavity between the substrate and the eye, allowing changes in intraocular pressure to change the shape of the membrane. A light beam may be emitted by a light transmitter in a handheld reading device, and the reflection of the light beam from the sensor is received by the device to measure the intraocular pressure of the eye.

[0007] In other embodiments, an intraocular pressure measurement system includes an intraocular pressure sensor implantable in the eye, the sensor comprising: an intraocular pressure sensor comprising: a lens coupled to a first surface of a substrate; and a film coupled to a second surface of the substrate, which changes shape as a function of the intraocular pressure of the eye; and a sensor reading device comprising: an optical transmitter that emits a light beam focused by the lens onto the active region of the sensor; and a receiver that generates an output signal in response to receiving a reflection of the light beam from the sensor in order to measure the intraocular pressure of the eye. In some embodiments, when the sensor is implanted in the eye, the first surface of the substrate faces the sensor reading device, and the second surface of the substrate faces the eye. In some embodiments, the lens includes a focal point that coincides with the active region of the sensor. For example, the lens may be a convex lens. In some embodiments, the lens may be operable to focus a light beam with an angular misalignment onto the active region of the sensor. In some embodiments, the angular misalignment is greater than 0.02 degrees. The light beam may include a collimated beam having a diameter greater than the diameter of the lens. The substrate may be a rigid substrate, and the membrane is a flexible membrane that together defines a cavity between the substrate and the eye, allowing changes in intraocular pressure to change the shape of the membrane. In some embodiments, the system may further include a processor configured to estimate the intraocular pressure of the eye based on processing the output signal of a receiver. In further embodiments, the sensor reading device may be a handheld device.

[0008] The above summary does not constitute an exhaustive list of all embodiments of this disclosure. This disclosure is intended to include all systems and methods that can be implemented from all appropriate combinations of the various embodiments summarized above, as well as those disclosed in the following “Modes for Carrying Out the Invention” and specifically pointed out in the “Claims” section. Such combinations may have specific advantages not specifically enumerated in the above summary of the invention. [Brief explanation of the drawing]

[0009] Some aspects of the disclosure herein are shown in the accompanying drawings as examples, not limitations, where similar references indicate similar elements. It should be noted that references to “an” or “one” aspects in this disclosure do not necessarily refer to the same aspect, but rather mean at least one. Furthermore, for brevity and to reduce the total number of figures, a given figure could be used to illustrate features of two or more aspects of this disclosure, and not all elements in the figure are required for a given aspect. [Figure 1] A schematic diagram of an exemplary system including sensors and reader devices for measuring intraocular parameters of the eye is shown. [Figure 2] Figure 1 shows a schematic diagram of a user holding a reader device close to their eye to measure intraocular parameters of the eye. [Figure 3] A block diagram illustrating an exemplary system for measuring intraocular parameters of the eye is shown. [Figure 4] A schematic diagram of an exemplary sensor for measuring intraocular parameters is shown. [Figure 5] A schematic diagram of an exemplary sensor for measuring intraocular parameters is shown. [Modes for carrying out the invention]

[0010] Next, several aspects of this disclosure will be described with reference to the accompanying drawings. Wherever the shape, relative position and other aspects of the described parts are not expressly defined, the scope of the invention is not limited to the parts shown merely as examples. Also, although many details are described, it will be understood that some aspects of the disclosure can be carried out without these details. In other examples, well-known circuits, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0011] The terms used herein are for illustrative purposes only and are not intended to limit the disclosure. Spatially relative terms such as “beneath,” “below,” “lower,” “above,” and “upper” are used herein for ease of explanation to describe the relationship of one element or feature part to another, as shown in the drawings. It will be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientations depicted in the drawings. For example, if the device in the drawing is inverted, an element described as “below” or “beneath” of another element or feature will therefore be oriented “above” of the other element or feature. Thus, the exemplary term “below” can encompass both upward and downward directions. The device may be oriented in other ways (e.g., rotated 90 degrees or in other directions), and the spatially relative descriptors used herein may be interpreted accordingly.

[0012] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context specifically indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising" may specify the presence of the described features, steps, actions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, actions, elements, components, and / or groups thereof.

[0013] As used herein, the terms “or” and “and / or” should be interpreted as inclusive or to mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “A; B; C; A and B; A and C; B and C; any of A, B, and C.” Exceptions to this definition would only arise if the combination of elements, functions, steps, or actions is intrinsically mutually exclusive in some way.

[0014] Figure 1 shows an exemplary system for measuring intraocular parameters using a handheld device 2 (e.g., a reader device) and an implant 1 (e.g., an IOP sensor). Figure 1 shows an implant containing a sensor which is entirely implanted in the cornea, or alternatively, entirely implanted in the sclera. The drawings in this disclosure may not be to scale, but they show that the sensor or implant 1 is small enough to be implanted in a typical cornea or sclera (e.g., about 0.25–0.5 mm thick and / or about 1 mm in diameter). The sensor 1 may be passive in that it does not have a stored power source used to transmit signals containing information about the IOP. Instead, a portion of the sensor 1 is designed to bend, compress, or adapt in response to the IOP, and that portion is also designed to reflect incident light energy. As a result, the sensor 1 changes how it reflects light energy as a function of the IOP at that moment. Thus, the reflection changes, for example, over the course of a day, to follow the changing IOP (in the anterior chamber). Because the sensor is passive, it can be made small and thin so that it can be implanted in the cornea more easily and with a lower risk of complications compared to implantation sites further inside the eye, using minimally invasive means. The implant can be small enough, for example, about 1 mm in the xy plane, so that it fits perfectly into the indicated cornea or sclera. 2 It can be manufactured with a footprint or area and a thickness of 0.2 to 0.3 mm in the z direction.

[0015] Figure 2 illustrates a user holding device 2 in their hand, bringing the handheld device close to their eye to read sensor 1. In this embodiment, handheld device 2 is a portable or handheld device configured to read measured intraocular data when handheld device 2 is brought close to the eye and aligned with sensor 1. For example, handheld device 2 may be considered aligned with implant 1 when device 2 determines that certain alignment parameters are met and / or an alignment operation is performed (e.g., a visual target is aligned) and it is close to the eye and able to read sensor 1. Once device 2 determines that the alignment and distance parameters are met, device 2 can then read pressure data measured from sensor 1 and notify the user of the measured intraocular parameters.

[0016] Typically, in some embodiments, device 2 may have an optical lens that focuses the incident light beam 9 emitted by transmitter 13 onto the active area of ​​sensor 1 used for measurement. Transmitter 13 may be a single light emitter or an array of light emitters. In some embodiments, the emitted beam 9 may be directional and have a narrow or directional primary lobe aimed at sensor 1. In other embodiments, the emitted beam 9 may be a collimated beam having multiple parallel rays. Receiver 14 may be a single photodetector or it may be a one-dimensional or two-dimensional array of photodetectors (the latter is particularly useful if a processor determines an interference pattern, for example, via an imaging function performed on the signals generated by the array of photodetectors). IOP is then measured by detecting changes in the cornea that bend or compress the embedded sensor during the reflection of the incident beam detected by the receiver.

[0017] As discussed earlier, to ensure accurate readings, the focused or narrowed incident beam should be positioned within the active area of ​​sensor 1 using an angular position adjustment of approximately 0.02 degrees or better. Such precise position adjustment constraints may be difficult for the user to achieve. To mitigate these position adjustment constraints, sensor 1 may include, for example, a small optical lens configured to focus a relatively wide or narrow beam outside the desired angular position adjustment range toward the active area of ​​sensor 1. This, in turn, reduces the lateral and angular position adjustment sensitivity of device 2 to sensor 1, enabling faster, more reliable, and easier-to-use measurements.

[0018] Typically, Figure 3 shows a general overview of sensor 1 and device 2. Sensor 1 may include a rigid substrate 3 to which a flexible film 5 is attached (the terms rigid and flexible are relative to each other), thereby forming a sealed cavity 6. The sealed cavity 6 may be in contact with (or defined by) the inner surfaces of the substrate 3 and film 5. Film 5 may be spaced apart from the rigid surface 10 of substrate 3 in thickness or in the z-direction, for example, between 5 and 30 microns. Film 5 may be fabricated or coated from one or more of the following biocompatible materials: silica or any material having a suitable difference in optical refractive index compared to the surrounding tissue. In addition, substrate 3 may be fabricated or coated from one of the same biocompatible materials. The refractive indices of the film and substrate surfaces should be selected to maximize the contrast of interference resulting from reflections from their surfaces on sensor 1.

[0019] To perform IOP measurements, the reader 2 includes an optical transmitter (Tx) 13 and an optical receiver (Rx) 14, both of which may be integrated within the housing of the reader 2. The reader 2 is positioned with the eye (as shown in Figure 2) such that an optical beam 9 of incident light energy (radiation or wave) emitted by the transmitter 13 collides with the active region 7 of the sensor 1, while the reflections 9A, 9B of that radiation from the sensor 1 are detected (as its output signal) by the receiver 14. Note that the term “beam” is used commonly herein and does not require a beamforming transmitter array. The beam 9 enters the cornea, where it collides with (or is incident on) the active region 7 of the sensor 1 and is reflected by the sensor 1 toward the receiver. To help focus the beam 9 into the active region 7 of the sensor 1, the sensor 1 may further include an optical lens 8 positioned along the substrate 5 as shown. In some embodiments, lens 8 may be a convex lens or other type of lens having a short focal length to sensor 1 such that the focal alignment (focus or focal length) of lens 8 coincides with the center of the active region 7. For example, lens 8 may be a small lens mounted on the surface of substrate 5 opposite to film 5. For example, lens 8 may be mounted on a surface of substrate 5 (e.g., outer surface 10) that faces away from the eye or toward the beam 9 emitted by device 2, and can focus the beam 9 through the sensor into the active region 7.

[0020] Typically, in the specific example shown in Figure 3, the sensor 1 is directed such that the incident beam 9 first travels through the lens 8 and then focuses or aligns with the active region 7. The beam 9 strikes the rigid substrate 3, and some of the incident energy is reflected towards the receiver 14, while some is transmitted into the cavity 6, where it is reflected from the film 5 (towards the receiver) as shown. The estimated IOP is then determined by the optical measurement processor by digitally processing the electrical output signal of the receiver in response to interference reflections from at least two surfaces of the sensor 1. This is possible because the output signal of the receiver changes by a detectable means when the sensor 1 bends or changes shape due to the changing IOP.

[0021] The sealed cavity 6 may be a gas volume that is at a sufficiently low pressure, e.g., at or below atmospheric pressure, that allows changes in the IOP to sufficiently bend or change the shape of the membrane 5 (surrounding the sensor 1 and via the movement of corneal tissue caused by the changing IOP) so that it is detectable in reflection. When the sensor 1 is embedded in the indicated orientation, i.e., with the outer surface of the membrane 5 facing the inside of the eye (or the anterior chamber of the eye) and the outer surface of the substrate 3 (e.g., surface 10) facing the transmitter Tx (or the external environment of the eye), the incident beam 9 will be reflected at least four times, including at the boundary between the tissue and the substrate, the boundary between the substrate and the cavity, the boundary between the cavity and the membrane, and finally the boundary between the membrane and the tissue. Typically, the two reflections at the cavity boundaries are the most important, and the other two reflections can be minimized by an anti-reflective coating or appropriate selection of materials. More generally, the membrane 5 changes shape as a function of IOP, thereby changing the distance between the two reflective boundaries. The system further includes a processor that analyzes the signal from receiver Rx to interpret the reflection from sensor 1 in units of mmHg, for example, as an estimate of IOP. The processor may determine spectral frequency-dependent reflectivity characteristics in the receiver output signal that can be correlated with how much sensor 1 is bent or compressed (by IOP). Thus, the processor may function as a spectrometer (performing a spectroscopic algorithm). In another embodiment, the processor analyzes the signal from receiver Rx with spatial recognition to determine or evaluate interference patterns generated by reflection (the interference patterns vary as a function of the membrane's bending). The processor may determine an absolute pressure reading as the pressure acting on the sensor. An ambient pressure sensor may be used in the reader to determine the intraocular pressure relative to ambient pressure (typically required for IOP), and this reading can be subtracted from the absolute pressure reading. In yet another embodiment, the reader may also include an ambient temperature monitor to calibrate any temperature-dependent performance of the implant. In addition, the leader may include an accelerometer to determine the orientation of the implant.

[0022] However, as discussed above, an inclination of approximately 0.02 degrees or more from the optical axis or the normal of the beam emitted by the reader 2 to the normal of the implant can cause the reflected beam from the sensor 1 to lose sight of the reader 2. For example, any lateral displacement of the sensor 1 in any direction results in a displacement of the beam focus from the active area 7 of the sensor 1 and an inaccurate thickness measurement. Further, it can be difficult for the user to know that the position adjustment is close to optimal. To reduce the position adjustment sensitivity, the lens 8, as shown in more detail by the enlarged views of FIGS. 4 and 5, is designed to focus the active area of the sensor 1 and a beam that is less focused, collimated, imperfectly position-adjusted, laterally canceled, or otherwise not precisely position-adjusted.

[0023] Typically, FIG. 4 shows a lens 8 attached to the sensor 1 for focusing a portion of a collimated light beam 9 onto the active area 7. For example, as shown by the enlarged view of section A in FIG. 4, the lens 8 has a focal length or length 11 such that the focus is aligned or remains directly on the active area 7. For example, the lens 8 can have a short focal length to the sensor 1 such that the focus alignment of the lens 8 coincides with the center of the active area 7 where the measurement is used. In this manner, the lens 8 can focus a beam 9 having a diameter (D1) several times larger than the size or diameter (D2) of the lens 8 onto the active area 7. For example, the diameter (D2) of the lens 8 can be from about 75 microns to about 125 microns, and the diameter (D1) of the beam 9 can be several times larger than the diameter (D2) of the lens 8. The illustrated configuration provides two main advantages. First, even when some lateral displacement of the sensor / reader is introduced, the lens 8 remains illuminated. Thus, depending on the application, the user can trade off the percentage of lost light intensity and the sensitivity to lateral displacement. Second, any angular misalignment between the reader 2 and the sensor 1 results in a minimal displacement of the focus. Generally, such a displacement is f *Equal to tan(a), where f is the focal length of the small lens and a is the angular deviation. For f = 200 microns (μm) and an active area of 40 μm, this results in an acceptable angular deviation of ±6 degrees (°). Thus, depending on the application, the user can trade off the ratio of the captured light intensity (the proportional ratio of the area of the lens to the area of the beam cross-section) and the angular / transverse displacement sensitivity (proportional to the ratio of the small lens focal length to the size of the active area).

[0024] Figure 5 shows another scenario where a misaligned beam 9 is focused onto the active area 7 using a lens 8 attached to the sensor 1. For example, as shown by the enlarged view of section B in Figure 5, the beam 9 can be a relatively narrow or focused beam, but it is either displaced at an angle 12 (e.g., greater than or equal to about 0.02 degrees) from the normal or center of the active area 7 of the sensor 1, or it can be a canceled-out tilt. Without the lens 8, this displacement can cause the beam 9 to miss the active area 7 of the sensor 1 and result in an inaccurate thickness measurement. However, as can be shown from section B of Figure 5, when the beam 9 hits the lens 8, the lens 8 redirects the misaligned beam 9 and focuses it onto the active area 7. In this manner, the lateral and / or angular position adjustment sensitivity is significantly reduced, making the system more reliable and easier to use.

[0025] While certain embodiments are described and shown in the accompanying drawings, these are merely illustrative and not limiting to the broader invention, and it will be understood by those skilled in the art that the present invention is not limited to the specific structures and arrangements shown and described, as various other modifications may be made. For example, while passive implants or sensors are primarily disclosed herein, it should be understood that in some embodiments, the sensor or implant may be considered an active sensor and have a stored power source used to transmit signals containing information about IOPs. In addition, the embodiments disclosed herein are not limited to ophthalmic / medical sensing applications but can be used in a much wider range of measurement applications involving miniature sensors and iterative repositioning of external optical measuring devices. Therefore, this description should be considered illustrative rather than limiting.

Claims

1. An intraocular pressure sensor implant, A substrate defining a surface that can be implanted in the eye, A membrane bonded to the substrate, which is operable to change shape as a function of the intraocular pressure of the eye, and defines an active region, An intraocular pressure sensor implant comprising: a lens bonded to the substrate, which is operable to focus a light beam onto the active region for measuring the intraocular pressure based on the distance between the film and the surface;

2. The implant according to claim 1, wherein the lens is bonded to the surface of the substrate opposite to the film.

3. The implant according to claim 1, wherein the lens includes a focal length that coincides with the active region.

4. The implant according to claim 1, wherein the lens includes a convex lens.

5. The implant according to claim 1, wherein the lens includes a small lens having a diameter smaller than the diameter of the light beam.

6. The implant according to claim 1, wherein the light beam includes a collimated beam.

7. The implant according to claim 1, wherein the lens is operable to focus the light beam having an angular misalignment into the active region.

8. The implant according to claim 7, wherein the deviation of the angle is greater than 0.02 degrees.

9. The implant according to claim 1, wherein the substrate is a rigid substrate, and the membrane is a flexible membrane that jointly defines a cavity between the substrate and the eye, and allows changes in the intraocular pressure to change the shape of the membrane.

10. The implant according to claim 1, wherein the light beam is emitted by a light transmitter of a handheld reading device, and the reflection of the light beam from the sensor is received by the device to measure the intraocular pressure of the eye.

11. An intraocular pressure measurement system, An intraocular pressure sensor that can be implanted in the eye, wherein the sensor includes a lens bonded to a first surface of a substrate and a membrane bonded to a second surface of the substrate that changes shape as a function of the intraocular pressure of the eye, An intraocular pressure measurement system comprising: a sensor reading device including a light transmitter that emits a light beam focused into the active region of the sensor by the lens; and a receiver that generates an output signal in response to receiving a reflection of the light beam from the sensor for measuring the intraocular pressure of the eye.

12. The system according to claim 11, wherein when the sensor is embedded in the eye, the first surface of the substrate faces the sensor reading device and the second surface of the substrate faces the eye.

13. The system according to claim 11, wherein the lens includes a focal point that coincides with the center of the active region of the sensor.

14. The system according to claim 11, wherein the lens includes a convex lens.

15. The system according to claim 11, wherein the lens is operable to focus the light beam having an angular misalignment onto the active region of the sensor.

16. The system according to claim 15, wherein the angular deviation is greater than 0.02 degrees.

17. The system according to claim 11, wherein the light beam includes a collimated beam having a diameter larger than the diameter of the lens.

18. The system according to claim 11, wherein the substrate is a rigid substrate, and the membrane is a flexible membrane that jointly defines a cavity between the substrate and the eye, and allows changes in the intraocular pressure to change the shape of the membrane.

19. The system according to claim 11, further comprising a processor configured to estimate the intraocular pressure of the eye based on processing the output signal of the receiver.

20. The system according to claim 11, wherein the sensor reading device is a handheld device.

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