Intraocular pressure monitoring system based on contact lenses

Abstract

The invention discloses an intraocular pressure monitoring system based on contact lenses. The intraocular pressure monitoring system comprises a flexible contact lens matrix, a magnetic sensing unit, an external magnetic field detection device and a signal processing unit. The core of the contact lens is that the magnetic sensing unit adopts a 4-pole, 6-pole or 8-pole radial multi-pole magnetizing ring and is integrated in a non-optical area of the contact lens, and N-S poles which are alternately distributed on the circumference of the magnetic sensing unit are utilized to generate a high-gradient non-uniform magnetic field. When intraocular pressure change causes corneal curvature change, lens deformation causes physical structure change of the multi-pole magnetizing ring, and then external detectable magnetic field space distribution or gradient characteristic change is triggered. After an external magnetic field detection device captures the change, the change is mapped into a high-precision intraocular pressure value by resolving magnetic field gradient peak displacement or harmonic component proportion through a signal processing unit. The intraocular pressure monitoring system does not need a built-in power supply, has the advantages of high sensitivity, strong anti-interference capability and continuous non-invasive monitoring, and is suitable for long-term dynamic intraocular pressure management of diseases such as glaucoma.

Description

Technical Field

[0001] This invention belongs to the field of smart contact lenses, and particularly relates to an intraocular pressure monitoring system based on contact lenses. Background Technology

[0002] Glaucoma, an irreversible blinding eye disease characterized by optic nerve damage and visual field defects, has pathologically high intraocular pressure (IOP) as its most significant controllable risk factor. Therefore, long-term, continuous, and accurate monitoring of IOP is crucial for early diagnosis, disease assessment, and treatment adjustments in glaucoma. Currently, the gold standard for clinical IOP measurement is the Goldmann applanation method. However, this method has significant limitations: firstly, it is a single-point, contact measurement method and cannot provide a 24-hour dynamic IOP fluctuation curve, while peak IOP often occurs outside of outpatient hours; secondly, the measurement results are affected by corneal thickness, curvature, and operator subjectivity, which may lead to errors.

[0003] To overcome the aforementioned drawbacks, the industry has developed various dynamic intraocular pressure (IOP) monitoring technologies. One approach focuses on developing implantable micro-sensors, which are fixed inside the eye (e.g., in the anterior chamber or attached to the iris). While this technology enables continuous monitoring, its invasiveness brings significant surgical risks, such as infection, bleeding, and cataracts. Furthermore, implants may present biocompatibility, long-term stability, and power supply issues, hindering its widespread adoption as a routine diagnostic method. Another promising direction is non-invasive, wearable IOP monitoring technology, such as sensors based on contact lens platforms. Existing technologies disclose various solutions for integrating sensing elements into contact lenses. One method is strain gauge-based IOP detection, where a micro-resistance strain gauge is placed on the lens surface. Changes in IOP cause changes in corneal curvature, which in turn cause changes in the strain gauge's resistance. However, this approach is susceptible to temperature fluctuations and ambient temperature variations, exhibiting drift, and requires a wired signal lead, significantly impacting wearing comfort and practicality. Another method is intraocular pressure detection based on an LC resonant circuit. This method embeds an inductor (L) and a capacitor (C) into the lens to form a resonant circuit. Changes in intraocular pressure cause changes in the spacing between the capacitor plates, resulting in a shift in the resonant frequency. This approach can be used for wireless reading via radio frequency, but the frequency signal is easily affected by many factors such as reading distance, wearing posture, and the electrolyte composition of tears, resulting in poor stability and anti-interference capabilities.

[0004] In summary, existing intraocular pressure monitoring devices or systems, whether implantable or invasive, suffer from drawbacks such as invasiveness, discontinuity, low accuracy, or weak anti-interference capabilities. In particular, for contact lens-based platforms, how to capture the minute lens deformations caused by slight changes in intraocular pressure with high sensitivity and strong anti-interference capabilities in a passive and wireless manner remains a pressing technical challenge to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an intraocular pressure monitoring system based on contact lenses, comprising: a flexible contact lens substrate; Magnetic sensing unit is embedded in the non-optical area of ​​the flexible contact lens substrate; An external magnetic field detection device is used to detect changes in the magnetic field distribution or magnetic field gradient of the magnetic sensing unit in a non-contact manner. The signal processing unit is communicatively connected to the external magnetic field detection device and is used to map changes in magnetic field distribution or magnetic field gradient into intraocular pressure values.

[0006] The curvature of the flexible contact lens substrate changes with intraocular pressure, which in turn causes deformation of the magnetic sensing unit.

[0007] Furthermore, the magnetic sensing unit is a radial multipole magnetized ring with N poles and S poles alternately distributed on its circumference to form a non-uniform magnetic field; the center of the radial multipole magnetized ring coincides with the center of the flexible contact lens substrate.

[0008] Furthermore, the radial multipole magnetization ring is a 4-pole, 6-pole, or 8-pole magnetization ring.

[0009] Furthermore, the magnetic sensing unit includes two concentric multipole magnetized rings, namely an inner ring and an outer ring.

[0010] Furthermore, the inner ring has 4, 6, or 8 magnetic poles, and the outer ring has 4, 6, or 8 magnetic poles. Furthermore, the external magnetic field detection device is an array-type magnetic sensor, which is installed on the eyeglass frame or head-mounted device; The number of array-type magnetic sensors is the same as the number of magnetic poles of the magnetic sensing unit, and their positions correspond one-to-one.

[0011] Furthermore, based on the changes in magnetic field distribution or gradient, the signal processing unit calculates at least one characteristic parameter from the changes in magnetic field distribution or gradient. The characteristic parameter includes the peak displacement of the magnetic field gradient, the proportional change of harmonic components, or the relative angle shift between magnetic poles. The peak displacement of the magnetic field gradient, the proportional change of harmonic components, or the relative angle shift between magnetic poles is mapped to an intraocular pressure value.

[0012] Furthermore, the peak displacement of the magnetic field gradient under different intraocular pressures is obtained, thereby obtaining the "intraocular pressure-peak displacement" curve. The peak displacement of the magnetic field gradient refers to the displacement relative to the peak position of the magnetic field gradient under normal intraocular pressure. The peak displacement of the magnetic field gradient calculated by the signal processing unit is compared with the "intraocular pressure-peak displacement" calibration curve to obtain the intraocular pressure value. or, Harmonic analysis is performed on the changes in magnetic field distribution or gradient under different intraocular pressures to obtain the amplitude ratio of at least one higher-order harmonic component to the fundamental component, and to obtain the "intraocular pressure-harmonic ratio" calibration curve; the ratio of the harmonic components calculated by the signal processing unit is compared with the "intraocular pressure-harmonic ratio" curve to obtain the intraocular pressure value; or, Under different intraocular pressures, the angular offset between the same magnetic poles in the multi-pole magnetization ring is obtained, and then the "intraocular pressure-angle offset" calibration curve is obtained. The angular offset between the same magnetic poles refers to the angular offset between the same magnetic poles under normal intraocular pressure. The relative angular offset between the same magnetic poles calculated by the signal processing unit is compared with the "intraocular pressure-angle offset" calibration curve to obtain the intraocular pressure value.

[0013] Furthermore, the intraocular pressure value is obtained by averaging the values ​​obtained from at least two feature parameters to obtain the final intraocular pressure value.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant features: 1. Extremely high sensitivity: Employing 4-, 6-, or 8-pole radial magnetizing rings, their inherent high-gradient magnetic field distribution is extremely sensitive to micron-level deformation. Nanoscale curvature changes in contact lenses caused by intraocular pressure can lead to circumferential strain in the magnetizing ring, inducing significant displacements in the peak value or harmonic components of the magnetic field gradient, thus amplifying and effectively capturing minute changes in intraocular pressure.

[0015] 2. Strong anti-interference capability: This invention detects the relative change in the spatial distribution of the magnetic field, rather than the absolute magnetic field strength. This method can effectively suppress interference introduced by the uniform magnetic field in the environment, temperature drift, and minute changes in the distance between the sensor and the glasses, resulting in a signal-to-noise ratio far exceeding that of schemes based on a single magnet.

[0016] 3. No built-in power supply required: The magnetic sensing unit is a passive permanent magnet, which does not require power supply, truly achieving passive operation and long-term continuous operation, thus solving the energy bottleneck problem of implantable devices or active sensors. Attached Figure Description Figure 1 This is a schematic diagram of a multipolar magnetized ring intraocular pressure monitoring contact lens; Figure 2 This is a schematic diagram illustrating the changes in intraocular pressure (IOP) of contact lenses during IOP monitoring from normal to elevated IOP states. Figure 3 This is a schematic diagram of a 4-pole radial, 6-pole radial, and 8-pole radial intraocular pressure monitoring contact lens with a permanent magnet structure having a non-uniform magnetic field distribution and a multi-pole magnetization ring. Figure 4 This is a schematic diagram of an intraocular pressure monitoring contact lens with a multipole magnetized ring structure having two non-uniform magnetic field distributions. Figure 5 This is a flowchart illustrating how intraocular pressure (IOP) is achieved using a multipolar magnetized ring contact lens. Figure 6 This is a real-time signal graph of intraocular pressure monitoring using a multi-polar magnetized ring contact lens on a simulated eyeball.

[0017] The components include: 1. a multi-pole magnetization ring; 2. a flexible contact lens substrate; 3. an external magnetic field detection device; and 4. a signal processing unit. Detailed Implementation

[0018] The present invention provides an intraocular pressure monitoring system based on contact lenses, comprising a flexible contact lens substrate, a magnetic sensing unit, an external magnetic field detection device, and a signal processing unit.

[0019] The magnetic sensing unit is embedded in the flexible contact lens substrate and is located in the non-optical area of ​​the flexible contact lens substrate. The external magnetic field detection device is used to non-contactly measure the spatial magnetic field distribution or magnetic field gradient changes generated by the magnetic sensing unit. The curvature of the flexible contact lens matrix can change slightly with variations in the wearer's intraocular pressure. For example... Figure 2 As shown, when intraocular pressure increases, the corneal curvature decreases, and the curvature of the flexible contact lens substrate also decreases, as does the curvature of the intraocular pressure monitoring contact lens. The change in corneal curvature causes a synchronous change in the curvature of the magnetization ring, which in turn causes a change in the relative distance between the magnetic pole and the external magnetic field detection device. When the corneal curvature decreases, the relative distance between the magnetic pole and the external magnetic field detection device increases, and when the corneal curvature increases, the relative distance between the magnetic pole and the external magnetic field detection device decreases.

[0020] The change in the relative distance between the magnetic pole and the external detection device causes a shift in the peak value of the magnetic field gradient of the magnetic pole. When the relative distance between the magnetic pole and the external detection device decreases, the peak value of the magnetic field gradient received by the external magnetic field detection device for the corresponding magnetic pole increases, and when the relative distance between the magnetic pole and the external detection device increases, the peak value of the magnetic field gradient received by the external magnetic field detection device for the corresponding magnetic pole decreases.

[0021] The magnetic sensing unit includes at least one permanent magnet with a non-uniform magnetic field distribution, such as... Figure 3 As shown, the permanent magnet is a radial magnetization ring including multiple magnetic poles, specifically a 4-pole, 6-pole, or 8-pole radial magnetization ring; the multi-pole magnetization ring has alternating N poles and S poles on its circumference, thereby generating a highly non-uniform magnetic field with a fixed gradient pattern in the space around it that dynamically changes with the deformation of the magnetization ring.

[0022] like Figure 4As shown, the magnetic sensing unit may also include two permanent magnets with non-uniform magnetic field distribution, namely a first permanent magnet and a second permanent magnet. The first permanent magnet is a 4-pole, 6-pole, or 8-pole radial magnetization ring, and the second permanent magnet is a 4-pole, 6-pole, or 8-pole radial magnetization ring. The first permanent magnet is the outer ring, and the second permanent magnet is the inner ring. The first permanent magnet and the second permanent magnet are nested together and share the same center.

[0023] like Figure 4 As shown in (a), the first permanent magnet is a 4-pole radial magnetization ring, and the second permanent magnet is a 6-pole radial magnetization ring; it can also be as follows: Figure 4 As shown in (b), the first permanent magnet uses an 8-pole radial magnetization ring, and the second permanent magnet uses a 6-pole radial magnetization ring, except... Figure 4 Besides the combination of extreme numbers in the formula, other combinations of extreme numbers can also be used; The external magnetic field detection device is an array of magnetic sensors fixed to eyeglass frames or head-mounted devices, capable of capturing magnetic field vector information with high spatial resolution.

[0024] The number of array-type magnetic sensors is the same as the number of central magnetic poles of the radial magnetization ring, and their positions correspond one-to-one. The array-type magnetic sensors are evenly distributed on the ring.

[0025] Furthermore, the signal processing unit, which is communicatively connected to the external magnetic field detection device, is configured to receive the magnetic induction intensity and direction of the magnetic field generated by the magnetic poles, and to calculate from the magnetic induction intensity and direction the position shift of the magnetic field gradient peak, the amplitude ratio change of a specific harmonic component, or the slight offset of the relative angle between the magnetic poles, and to map and calibrate the changes in magnetic field distribution or magnetic field gradient to the corresponding intraocular pressure value.

[0026] First, a two-dimensional planar model is used to illustrate the relationship between the displacement of the magnetic field gradient peak and changes in intraocular pressure. Assume a multi-pole magnetized ring on the surface of an intraocular pressure monitoring contact lens has a 4-pole, 6-pole, or 8-pole radial magnetized ring with an initial radius of curvature of R1. On a plane at a fixed distance from the center of the ring, the magnetic field gradient has a clear radial peak, initially located at angle θ1 = 0°. As intraocular pressure increases, the radius of curvature of the cornea decreases, stretching the magnetized ring to an effective radius of curvature of R2. During this process, the circumference of the magnetized ring changes by ΔC = 2π(R1 - R2). This change in circumference causes a displacement of the magnetic field gradient peak. The angular displacement Δθ of the magnetic field gradient peak is proportional to the rate of change of the radius of curvature ΔR / R, where Δθ = k ((R1-R2) / R1), where k is a scaling factor determined by calibration.

[0027] Normal intraocular pressure is IOP1. The peak position of the magnetic field gradient measured at this intraocular pressure is P1 (coordinates x1, y1). When the intraocular pressure increases to IOP2, the peak position of the magnetic field gradient measured at this intraocular pressure is P2 (coordinates x2, y2). The magnitude of the displacement vector can then be calculated. By simulating different intraocular pressures (or directly corresponding to different radii of curvature), a calibration curve of "intraocular pressure-peak displacement" is established. Based on the actual positional shift of the peak magnetic field gradient measured in the experiment, the real-time intraocular pressure value can be calculated.

[0028] Secondly, the relationship between the amplitude ratio change of specific harmonic components and intraocular pressure (IOP) changes is explained. Multipolar magnetic fields can be decomposed into components of different orders using spherical harmonic function analysis. IOP-induced deformation leads to a change in the ratio of higher-order harmonic components (such as the quadrupole moment |B4|) to the fundamental component (dipole moment |B2|). After the external sensor array acquires the spatial magnetic field strength, the signal processing unit performs real-time harmonic analysis to calculate the amplitude of each harmonic component. The amplitude ratio of the quadrupole component to the dipole component, |B4| / |B2|, is used as a sensitive indicator. Normal IOP is IOP1; at this IOP, the amplitude ratio change of the harmonic components is |B4| / |B2| = ΔB1. When the IOP increases to IOP2, the amplitude ratio of the harmonic components is |B4| / |B2| = ΔB2. Similarly, a calibration curve for the "IOP-harmonic ratio" is established experimentally: ΔIOP = α(ΔB2 - ΔB1), where α is a proportionality coefficient determined through calibration. The real-time intraocular pressure can be calculated by measuring the amplitude ratio of specific harmonic components in the experiment.

[0029] Furthermore, the relationship between minute shifts in the relative angles between magnetic poles and changes in intraocular pressure is explained. Ideally, for a 4-pole magnetic ring, the angle between the four poles should be 90°; for a 6-pole ring, the angle between any two adjacent poles should be 60°; and for an 8-pole ring, the angle between any two adjacent poles should be 45°. When the magnetic ring is stretched unevenly, the angles between adjacent poles change. By precisely tracking the direction of the magnetic field vector generated by each pole, these angular changes can be calculated, and an external sensor can be used to distinguish the direction of the magnetic field generated by each pole. The sensor analyzes the direction of the magnetic field vector and calculates the angle φ formed by two adjacent N poles and the center point (ideally 180° for a 4-pole magnetic ring, 120° for a 6-pole magnetic ring, and 90° for an 8-pole magnetic ring). Normal intraocular pressure (IOP) is IOP1, and the relative angle between identical magnetic poles is measured at this IOP as φ1. When the IOP increases to IOP2, the relative angle between the magnetic poles is measured at this IOP as φ2, and the angle offset is Δφ. The relative angle between identical magnetic poles refers to the angle formed by the lines connecting the two identical magnetic poles to the center of the magnetized ring. An "IOP-angle offset" calibration curve is established based on the IOP value and the angle offset, where ΔIOP = ε. Δφ, where ε is a proportionality coefficient determined through calibration. Substituting the measured real-time offset into the formula, the corresponding intraocular pressure value can be calculated.

[0030] Therefore, the real-time intraocular pressure change can be obtained by simultaneously calculating the positional shift of the magnetic field gradient peak, the amplitude ratio change of specific harmonic components, and the offset of the relative angle between magnetic poles.

[0031] Theoretically, changes in intraocular pressure can be obtained by calculating only the positional shift of the magnetic field gradient peak, the amplitude ratio change of specific harmonic components, or the offset of the relative angle between magnetic poles. However, calculating all three simultaneously can eliminate some external interference, such as interference from blinking and eye movement signals.

[0032] like Figure 6 As shown, the functionality of the multi-pole magnetized ring intraocular pressure monitoring contact lens was verified by simulating changes in intraocular pressure through an eyeball simulation. As the intraocular pressure continuously increases and decreases, the multi-pole magnetized ring intraocular pressure monitoring contact lens can accurately read the intraocular pressure data.

Claims

1. An intraocular pressure monitoring system based on contact lenses, characterized in that, include: Flexible contact lens substrate; Magnetic sensing unit is embedded in the non-optical area of ​​the flexible contact lens substrate; An external magnetic field detection device is used to detect changes in the magnetic field distribution or magnetic field gradient of the magnetic sensing unit in a non-contact manner. The signal processing unit is communicatively connected to the external magnetic field detection device and is used to map changes in magnetic field distribution or magnetic field gradient into intraocular pressure values.

2. The intraocular pressure monitoring system based on contact lenses according to claim 1, characterized in that, The curvature of the flexible contact lens substrate changes with intraocular pressure, which in turn causes deformation of the magnetic sensing unit.

3. The intraocular pressure monitoring system based on contact lenses according to claim 1, characterized in that, The magnetic sensing unit is a radial multipole magnetized ring with N poles and S poles alternately distributed on its circumference, forming a non-uniform magnetic field.

4. The intraocular pressure monitoring system according to claim 3, characterized in that, The radial multipole magnetization ring is a 4-pole, 6-pole, or 8-pole magnetization ring.

5. The intraocular pressure monitoring system based on contact lenses according to claim 1, characterized in that, The magnetic sensing unit includes two concentric multipole magnetized rings, namely an inner ring and an outer ring.

6. The intraocular pressure monitoring system according to claim 5, characterized in that, The inner ring has 4, 6, or 8 magnetic poles, and the outer ring has 4, 6, or 8 magnetic poles.

7. The intraocular pressure monitoring system based on contact lenses according to claim 1, characterized in that, The external magnetic field detection device is an array-type magnetic sensor, which is installed on the eyeglass frame or head-mounted device; The number of array-type magnetic sensors is the same as the number of magnetic poles of the magnetic sensing unit, and their positions correspond one-to-one.

8. The intraocular pressure monitoring system based on contact lenses according to claim 1, characterized in that, Based on the changes in magnetic field distribution or gradient, the signal processing unit calculates at least one characteristic parameter from the changes in magnetic field distribution or gradient. The characteristic parameter includes the peak displacement of the magnetic field gradient, the proportional change of harmonic components, or the relative angular offset between magnetic poles. The peak displacement of the magnetic field gradient, the proportional change of harmonic components, or the relative angular offset between magnetic poles is mapped to an intraocular pressure value.

9. The intraocular pressure monitoring system based on contact lenses according to claim 8, characterized in that, The peak displacement of the magnetic field gradient under different intraocular pressures is obtained, and then the "intraocular pressure-peak displacement" curve is obtained. The peak displacement of the magnetic field gradient refers to the displacement relative to the peak position of the magnetic field gradient under normal intraocular pressure. The peak displacement of the magnetic field gradient calculated by the signal processing unit is compared with the "intraocular pressure-peak displacement" calibration curve to obtain the intraocular pressure value. or, Harmonic analysis is performed on the changes in magnetic field distribution or gradient under different intraocular pressures to obtain the amplitude ratio of at least one higher-order harmonic component to the fundamental component, and to obtain the "intraocular pressure-harmonic ratio" calibration curve; the ratio of the harmonic components calculated by the signal processing unit is compared with the "intraocular pressure-harmonic ratio" curve to obtain the intraocular pressure value; or, Under different intraocular pressures, the angular offset between the same magnetic poles in the multi-pole magnetization ring is obtained, and then the "intraocular pressure-angle offset" calibration curve is obtained. The angular offset between the same magnetic poles refers to the offset of the angle between the same magnetic poles under normal intraocular pressure. The relative angular offset between the same magnetic poles calculated by the signal processing unit is compared with the "intraocular pressure-angle offset" calibration curve to obtain the intraocular pressure value.

10. The intraocular pressure monitoring system based on contact lenses according to claim 9, characterized in that, The final intraocular pressure value is obtained by averaging the values ​​obtained from at least two feature parameters.

Images