Non-contact tonometer and method of measuring intraocular pressure

Abstract

A non-contact tonometer (100, 200, 302, 502) is disclosed. This tonometer comprises an excitation and measurement unit (102, 202, 300, 504), which comprises at least one electric coil (106, 206, 304, 404, 508) driven by a fluctuating current (i) to generate a fluctuating magnetic field (416, 500). At least one magnetic armature (108, 208, 210, 212, 510) guides the fluctuating magnetic field through the cornea (112, 216, 301, 402) of the eye (110, 214, 303, 418, 512). A method for measuring intraocular pressure is also disclosed.

Description

Technical Field

[0001] The disclosure of the present application (hereinafter referred to as the present disclosure) relates to a non-contact tonometer. The present disclosure also relates to a method for measuring the intraocular pressure value of an eye. Background

[0002] A tonometer is a medical device used to measure the pressure inside the eyeball (intraocular pressure: IOP). Usually, intraocular pressure measurement is a quick, painless, and non-invasive examination, and it is generally carried out during a comprehensive ophthalmic examination. There are various types of tonometers based on different operating principles. One type of known tonometer applies vibration excitation to the eye and measures the vibration response. The tonometer measures the vibration generated on the cornea and calculates the intraocular pressure (IOP) of the eye from the measured value.

[0003] There are several techniques showing the correlation between the resonance frequency of the eyeball and the internal pressure. Based on this correlation, it is possible to calculate the internal pressure of the eyeball using the measured resonance frequency of the eyeball. In such techniques, the eyeball is measured using acoustic excitation and a laser Doppler velocimeter. The resonance frequency at which the first peak in the vibration amplitude of the cornea is observed is determined. The acoustic excitation is applied using a speaker. To enhance the energy transfer efficiency from the speaker to the eye, the speaker is attached to a soft cup and pressed against the face of the subject around the eye. Thereby, the vibration of the speaker diaphragm is transmitted to the eye through the air pressure fluctuations in the space surrounded by the speaker diaphragm, the soft cup, and the subject's face. This air pressure fluctuation applies a varying force to the cornea of the eye, causing the vibration of the eyeball. By changing the frequency of the air pressure applied to the eyeball, it becomes possible to measure the resonance frequency of the eyeball.

[0004] However, this technology is not contactless. Furthermore, because the soft cup is pressed against the subject's skin, there is a risk of disease transmission (such as COVID-19) from one subject to another. In some cases, the soft cup may be sterilized before use on other subjects. However, sterilization requires human intervention and cannot completely eliminate the risk of infection transmission. In addition, sterilization increases the time and cost of the procedure.

[0005] Furthermore, variable pressure has the disadvantage of applying a variable force to the annular region surrounding the eyeball. Intraocular pressure is measured using the vibrational response of the eyeball. However, the above techniques cannot accurately measure intraocular pressure. The main reason is that pressure fluctuations act not only on the cornea but simultaneously on the eyeball and the annular region surrounding it. These pressure fluctuations cause desirable vibrations of the cornea related to intraocular pressure, but also undesirable secondary vibrations in the entire eyeball and surrounding tissues. These secondary vibrations depend on the stiffness and volume of the surrounding tissues and are unrelated to intraocular pressure. Therefore, secondary vibrations interfere with measurement and make the relationship between intraocular pressure and the measured vibrational response of the cornea inaccurate.

[0006] In light of these circumstances, it is necessary to overcome the aforementioned shortcomings in existing technologies and devices for measuring intraocular pressure. Summary

[0007] This disclosure aims to provide a non-contact tonometer. This disclosure also aims to provide a method for measuring intraocular pressure. The object of this disclosure is to provide a solution that overcomes, at least partially, the problems encountered in the prior art.

[0008] According to one interpretation, embodiments of this disclosure provide a non-contact tonometer. This tonometer provides, Equipped with an excitation and measurement unit, The excitation and measurement unit has an electromagnetic exciter, The electromagnetic exciter is, • At least one electric coil, driven by a fluctuating current (i) and configured to generate a fluctuating magnetic field, • At least one magnetic armature configured to guide the fluctuating magnetic field toward the eye such that the fluctuating magnetic field passes through at least partially the cornea of ​​the eye, It is equipped with.

[0009] In another aspect, embodiments of the present disclosure provide a method for measuring intraocular pressure. This method is • By applying a fluctuating magnetic field, the cornea of ​​the eye is vibrated, - The frequency of the fluctuating magnetic field is changed within a predetermined frequency range, • Measuring at least the peak amplitude value of the corneal vibration, • In order to find the resonant frequency value of the cornea, the minimum value of the frequency corresponding to the peak amplitude value is found, • Calculating the intraocular pressure value of the eye using the aforementioned resonant frequency, Includes.

[0010] Embodiments of this disclosure substantially eliminate, or at least partially solve, the aforementioned problems of the prior art, realizing an improved non-contact tonometer that is simple, compact, accurate, reliable, efficient, and efficient. This non-contact tonometer employs an electromagnetic exciter and is advantageous because it applies excitation force to the cornea in a non-contact manner. Furthermore, because the excitation force is limited to a desired area of ​​the cornea, it becomes possible to measure intraocular pressure with high precision.

[0011] Further aspects, advantages, features, and objectives of what is disclosed herein will be made clearer by the accompanying drawings and the detailed description of exemplary embodiments, as to be interpreted in conjunction with the accompanying claims.

[0012] It will also be understood that a feature of this disclosure is that it can be combined in various ways without departing from the scope defined by the attached claims. [Brief explanation of the drawing]

[0013] The above summary and the following detailed description of exemplary embodiments will be better understood in conjunction with the accompanying drawings. For illustrative purposes of this disclosure, exemplary configurations of this disclosure are shown in the drawings. However, this disclosure is not limited to the specific methods and apparatus disclosed herein. The scale of the drawings is not accurate. Similar elements are indicated by the same number whenever possible. Hereinafter, embodiments of the present disclosure will be described only as examples, with reference to the following drawings. [Figure 1A] This figure shows a first preferred embodiment of a non-contact tonometer according to the embodiments of the present disclosure. [Figure 1B] This figure shows a first preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 1C] This figure shows a first preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 2A] This figure shows a second preferred embodiment of a non-contact tonometer according to the embodiments of the present disclosure. [Figure 2B] This figure shows a second preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 2C] This figure shows a second preferred embodiment of a non-contact tonometer according to the embodiments of the present disclosure. [Figure 2D] This figure shows a second preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 3A] This figure shows a third preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 3B] This figure shows a third preferred embodiment of the excitation and measurement unit according to the embodiments of the present disclosure. [Figure 3C] This figure shows a third preferred embodiment of a non-contact tonometer according to the embodiments of the present disclosure. [Figure 4] This is another figure of a third preferred embodiment of an electromagnetic exciter according to the embodiments of the present disclosure. [Figure 5A] This figure illustrates the fluctuating magnetic field generated toward the eye using a non-contact tonometer according to a first preferred embodiment of the present disclosure. [Figure 5B] FIG. showing a first preferred embodiment of a current induced by a changing magnetic field inside the eyeball according to the first preferred embodiment and the second preferred embodiment of the present disclosure. [Figure 5C] FIG. showing a first preferred embodiment of a current induced by a changing magnetic field inside the eyeball according to the first preferred embodiment and the second preferred embodiment of the present disclosure. [Figure 6A] Another illustration of a changing magnetic field generated toward the eye using a non-contact tonometer according to the third preferred embodiment of the present disclosure. [Figure 6B] Another illustration of a changing magnetic field generated toward the eye using a non-contact tonometer according to the third preferred embodiment of the present disclosure. [Figure 7] A flowchart showing steps of a method for measuring an intraocular pressure value of an eye according to an embodiment of the present disclosure. In the accompanying drawings, the underlined numbers are used to represent the item at the location where the number is located or the item adjacent to that number. The non-underlined numbers are associated with the item specified by the line extending from the number. When a number is written without an underline and with an arrow, that number is used to identify the general item indicated by the arrow. Detailed Description of Embodiments

[0014] The following detailed description illustrates embodiments of the present disclosure and methods by which they may be implemented. Although several forms for implementing the present disclosure have been disclosed, those skilled in the art will recognize that other forms for implementing the present disclosure are also possible.

[0015] In one aspect, embodiments of the present disclosure provide a non-contact tonometer. This tonometer comprises an excitation and measurement unit, the excitation and measurement unit has an electromagnetic exciter, the electromagnetic exciter · at least one electric coil driven by an alternating current (i) and configured to generate an alternating magnetic field, • At least one magnetic armature configured to guide the fluctuating magnetic field toward the eye such that the fluctuating magnetic field passes through at least partially the cornea of ​​the eye, It is equipped with.

[0016] In another aspect, embodiments of the present disclosure provide a method for measuring intraocular pressure. This method is • By applying a fluctuating magnetic field, the cornea of ​​the eye is vibrated, - The frequency of the fluctuating magnetic field is changed within a predetermined frequency range, • Measuring at least the peak amplitude value of the corneal vibration, • In order to find the resonant frequency value of the cornea, the minimum value of the frequency corresponding to the peak amplitude value is found, • Calculating the intraocular pressure value of the eye using the aforementioned resonant frequency, Includes.

[0017] This disclosure provides the aforementioned non-contact tonometer and method, which are simple, compact, robust, highly accurate, reliable, and user-friendly. Advantageously, this non-contact tonometer employs an electromagnetic exciter that enables the application of an excitation force to the cornea without contact. Furthermore, this non-contact tonometer eliminates the risk of disease transmission between subjects. The electromagnetic exciter employed in this non-contact tonometer comprises at least one electric coil and at least one magnetic armature, which work together to determine the ocular vibration response and internal pressure of the eye.

[0018] In accordance with embodiments of this disclosure, the term “non-contact tonometer” as used herein refers to a device used to measure intraocular pressure in a non-contact manner. The term “intraocular pressure (IOP)” as used herein refers to the fluid pressure within the eyeball. Intraocular pressure exerts force on all parts of the eyeball. The cornea is a suitable surface for measuring intraocular pressure. Measuring intraocular pressure on the cornea is easier and more accurate than measuring it on other surfaces of the eyeball, such as the sclera. Measuring intraocular pressure is crucial for maintaining the overall health and function of the eye. Non-contact tonometers can be used to measure intraocular pressure. This measurement allows for the diagnosis and treatment of ocular hypertension before the onset of eye diseases such as glaucoma.

[0019] Non-contact tonometers include an excitation and measurement unit. In this specification, “excitation and measurement unit” refers to a configuration used to measure the internal pressure of the cornea by exciting the cornea and measuring its vibrational response. Here, excitation refers to the process of applying a fluctuating force to the cornea. The excitation and measurement unit includes an electromagnetic exciter. As used herein, the term “electromagnetic exciter” refers to a device capable of generating an electromagnetic force in the anterior part of the eye, thereby causing mechanical movement in the cornea. In this context, electromagnetic force refers to the excitation force that causes mechanical movement of the cornea, such as mechanical vibration or oscillation. The eyeball can be considered, for example, a thin-walled elastic vessel filled with a pressurized fluid. Therefore, the eyeball has mechanical vibrational behavior and resonant frequencies.

[0020] An electromagnetic exciter has at least one electric coil that is driven by a fluctuating current (i) and arranged to generate a fluctuating magnetic field. The term “electric coil” as used herein refers to a conductor such as a coiled (spiral or helical) wire.

[0021] In some embodiments, the at least one electric coil is composed of one or more wire windings.

[0022] Depending on the embodiment, the shape and number of the at least one electrical coil may vary depending on its application.

[0023] In some embodiments, the at least one electric coil is manufactured using insulated copper wire. Typically, the at least one electric coil is wound around a core. The electrical terminals of the coil are connected to a power source to receive current, which is variable and preferably alternating current. During operation, the electric coil is driven by the fluctuating current, generating a fluctuating magnetic field. The amount of current can be changed by increasing or decreasing the power supplied from the power source.

[0024] The electromagnetic exciter has at least one magnetic armature. Here, "magnetic armature" refers to a structure made of ferromagnetic material associated with at least one winding (or group of windings) of an electric coil.

[0025] In some embodiments, the at least one magnetic armature is a U-shaped magnetic armature having a first arm with a first end and a second arm with a second end. Regardless of its shape, the at least one magnetic armature can direct a fluctuating magnetic field toward the eye.

[0026] The at least one electric coil and the at least one magnetic armature are mounted together such that the fluctuating magnetic field generated by the at least one electric coil can be directed by the at least one magnetic armature toward the cornea of ​​the eye. The fluctuating magnetic field is directed so that it passes at least partially through the cornea of ​​the eye. The fluctuating magnetic field induces an electric current within the conductive materials of the cornea and aqueous humor. The interaction between the induced current and the fluctuating magnetic field generates a fluctuating axial force on the cornea. This fluctuating axial force applied to the cornea causes mechanical vibration of the cornea. The frequency of the alternating current driving the electric coil is equal to the fluctuating frequency of the fluctuating magnetic field generated by the electric coil, equal to the fluctuating electromagnetic force applied to the cornea, and equal to the frequency of the mechanical vibration of the cornea.

[0027] Depending on the embodiment, the at least one magnetic armature includes an internal magnetic armature, an external magnetic armature, and a rear magnetic armature.

[0028] In some embodiments, the internal magnetic armature has a conical shape with an internal bore that may be substantially conical.

[0029] Depending on the embodiment, the number and shape of the magnetic armature may vary depending on the application.

[0030] In some embodiments, the at least one electric coil is located within the external magnetic armature.

[0031] In some embodiments, the at least one electric coil is arranged to surround the internal magnetic armature.

[0032] Depending on the embodiment, the electromagnetic exciter further comprises at least one permanent magnet.

[0033] Depending on the embodiment, the permanent magnet may be a neodymium magnet or a samarium-cobalt magnet, both of which are well known as strong magnets.

[0034] In some embodiments, the electromagnetic exciter has one or more permanent magnets that, together with the magnetic armature, apply a strong steady magnetic field to the cornea. Advantageously, the at least one permanent magnet is used to generate a steady magnetic field in the eye with a higher magnetic flux density than the fluctuating magnetic field magnetic flux density generated when using only at least one electric coil in a non-contact tonometer.

[0035] When an electric coil is driven by a fluctuating current, the fluctuating magnetic field generated by the coil is added to the steady magnetic field generated by the permanent magnet. As a result, a magnetic field is created in which the magnetic flux density fluctuates around a steady value. The fluctuation in magnetic flux density in the anterior chamber of the eye generates a fluctuating current in the conductive materials of the cornea and aqueous humor. The interaction between this fluctuating current and the strong steady component of the magnetic field generated by the permanent magnet results in a fluctuating electromagnetic force stronger than the electromagnetic force obtained in the preferred embodiment without a permanent magnet described earlier. This strong electromagnetic force improves the vibration excitation efficiency of the cornea.

[0036] In some embodiments, the excitation and measurement unit further includes an optical displacement sensor. Here, "optical displacement sensor" refers to a displacement sensor that uses an optical element and a light beam to measure the distance between the sensor and the object.

[0037] In some embodiments, the optical displacement sensor is positioned between the first and second arms of the U-shaped magnetic armature to detect corneal vibrations. The optical displacement sensor is positioned appropriately to accurately identify corneal vibrations.

[0038] In some embodiments, the distance between the first arm and the second arm is minimized towards the first and second ends that are closer to the eye. This geometric structure enables efficient measurement of corneal vibrations.

[0039] Depending on the embodiment, the optical displacement sensor may be selected as at least one of a confocal chromatic displacement sensor or a laser Doppler vibrometer. As used herein, the term “confocal chromatic displacement sensor” refers to an instrument that operates by focusing light having a broadband wavelength (usually white light) onto the surface of a target (e.g., an eye) using a high-dispersion objective lens. Confocal chromatic displacement sensors are used for displacement measurements with a measurement frequency of several tens of kilohertz (kHz) and a resolution of several tens of nanometers.

[0040] Depending on the embodiment, the confocal chromatic displacement sensor is used to measure the distance between the user and their eye in the range of several millimeters to tens of millimeters. To reduce costs, the confocal chromatic displacement sensor may be customized.

[0041] As used herein, the term “laser Doppler vibrometer” refers to a type of sensor used to non-contact measure vibrations of a target surface (such as the eyeball). A laser beam from the laser Doppler vibrometer is directed at the target surface, and the amplitude and frequency of the vibration are extracted from the Doppler shift of the reflected laser beam frequency due to the movement of the surface. Typically, the output of a laser Doppler vibrometer is a continuous analog voltage directly proportional to the target velocity component along the laser beam direction. Laser Doppler vibrometers enable accurate measurement of corneal vibration amplitudes.

[0042] Depending on the embodiment, a confocal chromatic displacement sensor may be designed to enable measurements using an infrared light beam. The confocal chromatic displacement sensor uses broadband infrared light as the measurement beam to measure the displacement of the cornea of ​​the eye. Beneficially, infrared light is invisible to the eyes of subjects such as patients. This reduces the subject's urge to blink during initial stages, such as setting the appropriate relative position between the non-contact tonometer and the eye.

[0043] In some embodiments, infrared light is used to suppress blinking during measurement. Furthermore, infrared light is less likely to damage the eye being measured. The light beam of the confocal chromatic sensor is directed perpendicularly to the cornea.

[0044] Depending on the embodiment, the confocal chromatic displacement sensor can easily accommodate even if the optical axis is significantly tilted relative to the normal direction of the eyeball. As a result, even if a non-contact tonometer is handheld and not properly centered or oriented, it may not affect the measurement.

[0045] Depending on the embodiment, the optical displacement sensor can measure at least one of the following: • The amplitude of vibration at at least one point on the cornea. • The thickness of the cornea at at least one point. • The distance between the cornea and the excitation / measurement unit.

[0046] The excitation and measurement unit includes the optical displacement sensor. The optical displacement sensor, together with the electromagnetic exciter, is positioned close to the cornea of ​​the eye.

[0047] In some embodiments, the optical displacement sensor is capable of measuring the amplitude of vibration at at least one point on the cornea. The amplitude of vibration at at least one point on the cornea refers to the difference between the maximum and minimum distances between the optical displacement sensor and the cornea during corneal vibration.

[0048] In some embodiments, the amplitude is measured to determine the movement or displacement of at least one point during blinking or other eye movements. The confocal chromatic displacement sensor is capable of performing thousands of observations per second with a resolution of tens of nanometers, thereby enabling precise measurement of the vibration amplitude of at least one point on the cornea.

[0049] In some embodiments, the corneal resonant frequency can be determined using the vibration amplitude at at least one point on the cornea. When the cornea is excited by a fluctuating force, it vibrates at the frequency of the fluctuating force. When the frequency of the fluctuating force is equal to the corneal resonant frequency, the corneal vibration amplitude shows a peak value. By scanning the frequency of the electromagnetic force that excites the cornea over a frequency range, the corneal resonant frequency can be identified as the frequency corresponding to the peak of the corneal vibration amplitude. The corneal resonant frequency depends on intraocular pressure (pressure inside the eyeball) and is typically in the range of 100 to 500 Hz, depending on the thickness of the cornea.

[0050] Depending on the embodiment, the optical displacement sensor can measure the corneal thickness at at least one point on the cornea. Using a confocal chromatic displacement sensor is advantageous because it allows for the measurement of this corneal thickness. This is because the confocal chromatic displacement sensor has the ability to simultaneously measure the position of both the outer and inner surfaces of the cornea. Corneal thickness characterizes corneal stiffness and is a factor that interferes with intraocular pressure (IOP) measurement. When corneal thickness is measured, the value can be used to apply a correction when calculating IOP, thereby improving the accuracy of IOP calculation.

[0051] Depending on the embodiment, the optical displacement sensor can measure the distance between the anterior end of the non-contact tonometer and the cornea. The measured distance is used as feedback (visual feedback, acoustic feedback, etc.) in the initial stages of measurement. The measured distance also serves as an indicator of the correct position of the non-contact tonometer relative to the eye.

[0052] In some embodiments, if the non-contact tonometer is handheld, the measured distance may be used as feedback to confirm to the operator that the non-contact tonometer is positioned correctly relative to the eye, or as feedback indicating that a position change is necessary. It may also be used as feedback for an automatic position control system. The automatic position control system includes at least one actuator for changing the relative position between the non-contact tonometer and the eyeball. In this case, the actuator is controlled using the measured distance as feedback.

[0053] In some embodiments, the at least one electric coil is used as a sensor by measuring the change in the electrical impedance of the at least one electric coil caused by corneal vibration. In this regard, the maximum value of the electrical impedance of the coil corresponds to the peak of the amplitude of the corneal vibration.

[0054] Depending on the embodiment, in the non-contact tonometer, The permanent magnet has a substantially annular shape, with a first pole on one of its two opposing faces and a second pole on the other; The electromagnetic exciter has a proximal end and a distal end, and has a spatial volume extending along the centerline of the electromagnetic exciter from the proximal end to the distal end; The at least one magnetic armature is • An internal magnetic armature that at least partially encloses the spatial volume at the proximal end and is magnetically coupled to the first pole of the permanent magnet via the second end, • An external magnetic armature that at least partially surrounds the electric coil and is magnetically coupled to the second pole of the permanent magnet, It has, The electric coil surrounds the internal magnetic armature at least partially. Here, "annular shape" refers to a ring-shaped geometric pattern.

[0055] Depending on the embodiment, the permanent magnet may have an annular shape with an internal bore, and the internal bore may have a cylindrical shape.

[0056] In some embodiments, the permanent magnet has a first pole on one of its two opposing surfaces and a second pole on the other.

[0057] In some embodiments, the electromagnetic exciter has a proximal end and a distal end. The proximal end is closer to the cornea of ​​the eye, and the distal end is further away from the eye.

[0058] In some embodiments, the electromagnetic exciter has a spatial volume that extends along the centerline of the electromagnetic exciter from the proximal end to the distal end.

[0059] In some embodiments, the at least one magnetic armature has an internal magnetic armature, which at least partially encloses the spatial volume at its proximal end. The internal magnetic armature may also be magnetically coupled to the first pole of the permanent magnet via its second end.

[0060] In some embodiments, the at least one magnetic armature has an external magnetic armature, which at least partially surrounds the electric coil, and is magnetically coupled to the permanent magnet.

[0061] In some embodiments, the electric coil at least partially surrounds the internal magnetic armature. The above configuration contributes to improving the accuracy of measuring the intracorneal pressure of the eye.

[0062] In some embodiments, the electromagnetic exciter may function even if the at least one electric coil surrounds only the internal magnetic armature.

[0063] Depending on the embodiment, the electromagnetic exciter may function using a single electric coil and a coaxial structure of the at least one magnetic armature and the electric coil, even in the absence of a permanent magnet.

[0064] In some embodiments, the optical displacement sensor is positioned within the spatial volume. The above configuration allows the optical displacement sensor to be positioned near or at least partially inside the internal magnetic armature. In this case, the light beam emitted from the optical displacement sensor passes through the internal magnetic armature and reaches the cornea of ​​the eye to measure its displacement.

[0065] This disclosure also relates to the method described above. Various embodiments and modifications disclosed above are applicable to this method.

[0066] In some embodiments, a fluctuating magnetic field is generated by a coil driven by a fluctuating current (i), and the frequency scanning of the fluctuating current is performed within a predetermined frequency range.

[0067] Depending on the embodiment, the method may further be: • To measure the thickness of the cornea at at least one point; • Measuring the resonant frequency value of the cornea; The intraocular pressure of the eye is calculated using both the resonant frequency value of the cornea and the thickness value of the cornea; Includes.

[0068] Depending on the embodiment, the method may further be: • To measure the distance between the cornea and the excitation / measurement unit; The measured distance value is used as a feedback signal, and the excitation / measurement unit is positioned at a desired location relative to the cornea; Includes.

[0069] In some embodiments, the electrical impedance of the coil is continuously measured during the frequency scanning of the fluctuating current (i). In this case, the corneal resonant frequency is measured as the lowest frequency of the current (i) that causes the amplitude peak value of the coil's electrical impedance.

[0070] The amplitude peak of corneal vibration is measured using at least one electrical coil. An induced current (I) flows through the anterior part of the vibrating eye, causing a change in the electrical impedance of the at least one electrical coil. When the corneal vibration reaches its amplitude peak, the impedance of the at least one electrical coil reaches its maximum value. Therefore, by measuring the impedance fluctuation of the at least one electrical coil using various electrical means, it is possible to determine the initial amplitude peak of the corneal vibration. The electrical impedance of the at least one electrical coil is continuously measured through current frequency scanning to complete the measurement. The lowest frequency of the current that causes a peak in the electrical impedance of the at least one coil is identified as the resonant frequency of the corneal vibration. Detailed description of the drawings

[0071] Referring to Figure 1A, a preferred embodiment of a non-contact tonometer 100 according to an embodiment of the present disclosure is shown. Referring to Figures 1B and 1C, a perspective view of a first preferred embodiment of an excitation and measurement unit 102 according to an embodiment of the present disclosure is shown. The non-contact tonometer 100 has an excitation and measurement unit 102 comprising an electromagnetic exciter 104. The electromagnetic exciter 104 comprises at least one electric coil 106, which is driven by a fluctuating current (i) (not shown) and configured to generate a fluctuating magnetic field (not shown). The electromagnetic exciter 104 comprises at least one magnetic armature 108, which is positioned to direct the fluctuating magnetic field toward the eye 110. This fluctuating magnetic field passes at least partially through the cornea 112 of the eye 110. The excitation and measurement unit 102 further comprises an optical displacement sensor 114 positioned close to the cornea 112 of the eye 110 together with the electromagnetic exciter 104.

[0072] Figure 1C is a perspective view of the excitation and measurement unit 102. As shown, at least one magnetic armature 108 is a U-shaped magnetic armature having a first arm 116 having a first end and a second arm 118 having a second end. As shown, at least one electrical coil 106 is attached to the first arm 116 and the second arm 118 of the U-shaped magnetic armature. The non-contact tonometer 100 further includes electrical terminals 120 for supplying power to at least one electrical coil 106.

[0073] Figures 1A-1C are for illustrative purposes only and should not unduly limit the scope of the claims. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of the embodiments of this disclosure.

[0074] Referring to Figures 2A and 2C, a second preferred embodiment of a non-contact tonometer 200 according to an embodiment of the present disclosure is shown. Referring to Figures 2B and 2D, a second preferred embodiment of an excitation and measurement unit 202 according to an embodiment of the present disclosure is shown. The non-contact tonometer 200 comprises an excitation and measurement unit 202. The excitation and measurement unit 202 comprises an electromagnetic exciter 204. The electromagnetic exciter 204 comprises at least one electric coil 206 driven by a fluctuating current (i) and configured to generate a fluctuating magnetic field. The electromagnetic exciter 204 further comprises at least one magnetic armature, as shown in 208, 210, 212. The magnetic armature is configured to direct the fluctuating magnetic field toward the eye 214. The fluctuating magnetic field passes at least partially through the cornea 216 of the eye 214. The electromagnetic exciter 204 further comprises at least one permanent magnet, as shown in 218, 220. A magnetic field guided toward the eye by at least one magnetic armature has a tangential component of the magnetic flux density (Bt) within the eye. Here, Figure 2A shows a top view of the non-contact tonometer 200, and Figure 2B shows a perspective view of the non-contact tonometer 200. As shown in the figure, the excitation and measurement unit 202 includes an optical displacement sensor 222 positioned close to the cornea 216 of the eye 214, together with an electromagnetic exciter 204.

[0075] Figure 2C shows a plan view of the non-contact tonometer 200, and Figure 2D shows a perspective view of the excitation and measurement unit 202. As shown, at least one magnetic armature, indicated by 208, 210, and 212, is a U-shaped magnetic armature having a first arm with a first end and a second arm with a second end. The non-contact tonometer 200 further includes electrical terminals 224 for supplying power to at least one electric coil 206.

[0076] Figures 2A-2D and 2D are for illustrative purposes only and should not unduly limit the scope of the claims. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of the embodiments of this disclosure.

[0077] Referring to Figures 3A and 3B, a third preferred embodiment of an excitation and measurement unit 300 according to an embodiment of the present disclosure is shown. Referring to Figure 3C, a third preferred embodiment of a non-contact tonometer 302 according to an embodiment of the present disclosure is shown. Figure 3A is a longitudinal cross-sectional view of the excitation and measurement unit 300 in an operating position close to the cornea 301 of an eye 303. The excitation and measurement unit 300 has at least one electric coil 304. The excitation and measurement unit 300 comprises an electromagnetic exciter 309 having a proximal end 308 and a distal end 310. The electromagnetic exciter 309 further comprises a spatial volume 306 extending along the centerline of the electromagnetic exciter 309 from the proximal end 308 to the distal end 310. At least one magnetic armature includes an internal magnetic armature 312 positioned at the proximal end 308 to at least partially enclose the spatial volume. Also shown is an external magnetic armature 314 that is positioned to at least partially surround at least one electric coil 304 and is magnetically coupled to at least one permanent magnet 316. The at least one permanent magnet 316 has a substantially annular shape and has a first pole on one of its two opposing faces and a second pole on the other. The at least one permanent magnet 316 is an optional component of the excitation and measurement unit 300 and is used to increase its efficiency. The at least one electric coil 304 is positioned to at least partially surround the internal magnetic armature 312. The excitation and measurement unit 300 further includes an electrical terminal 318 for supplying power to the at least one electric coil 304. As shown in Figure 3C, the non-contact tonometer 300 includes an optical displacement sensor 320. Figure 3B is a perspective view of the excitation and measurement unit 300 in an operating position close to the eye 303. Figure 3C is a top view of the non-contact tonometer 300 in an operating position close to the eye 303.

[0078] Figures 3A, 3B, and 3C are illustrative and do not unduly limit the scope of the claims herein. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0079] Referring to Figure 4, another diagram of a third preferred embodiment of the electromagnetic exciter 400 according to an embodiment of the present disclosure is shown. Figure 4 shows a coaxial version of the electromagnetic exciter 400. This diagram shows a cross-section of the electromagnetic exciter 400 that applies vibrational excitation to the cornea 402. The electromagnetic exciter 400 includes at least one electric coil 404 and at least one magnetic armature. The at least one magnetic armature includes an internal magnetic armature 406, an external magnetic armature 408, and a rear magnetic armature 410. The internal magnetic armature 406 has a conical shape with an internal hole which may be substantially conical.

[0080] In some embodiments, at least one electric coil 404 is located within an external magnetic armature 408 and at least partially surrounds an internal magnetic armature 406.

[0081] In some embodiments, the electromagnetic exciter 400 has at least one permanent magnet 412. The electromagnetic exciter 400 also has electrical terminals 414 for supplying power to at least one electric coil 404. The at least one electric coil 404 is driven by a fluctuating current (i) and configured to generate a fluctuating magnetic field 416, where the fluctuating magnetic field 416 is a toroidal magnetic field. The electromagnetic exciter 400 includes at least one magnetic armature configured to guide the fluctuating magnetic field 416 toward the eyeball 418 such that the fluctuating magnetic field 416 passes at least partially through the cornea 402 of the eyeball 418.

[0082] Figure 4 is for illustrative purposes only and does not unduly limit the claims of this specification. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of embodiments of this disclosure.

[0083] Referring to Figure 5A, an illustration of a fluctuating magnetic field 500 generated using a non-contact tonometer 502 is shown according to a first preferred embodiment of the present disclosure. As shown in Figure 5A, the first preferred embodiment of the non-contact tonometer 502 comprises an excitation and measurement unit 504. The excitation and measurement unit 504 comprises an electromagnetic exciter 506. The electromagnetic exciter 506 is driven by a fluctuating current (i). The electromagnetic exciter 506 also has at least one electric coil 508 configured to generate a fluctuating magnetic field 500. Furthermore, the electromagnetic exciter 506 comprises at least one magnetic armature 510 configured to guide the fluctuating magnetic field 500 toward the eye 512 so that it passes at least partially through the cornea 514 of the eye 512.

[0084] Referring to Figures 5B and 5C, a first preferred embodiment of a current induced by a fluctuating magnetic field inside the eyeball 512 is shown. The fluctuating magnetic field is generated by an electromagnetic exciter with an induced current (I) and an electromagnetic force (Fem) applied to the cornea 514 of the eyeball 512. The fluctuating magnetic field has a tangential component of the magnetic flux density (Bt). Furthermore, an electromagnetic force is generated by the interaction between the induced current and the tangential component of the fluctuating magnetic field.

[0085] Figures 5A, 5B, and 5C are for illustrative purposes only and do not unduly limit the scope of the claims herein. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0086] Referring to Figures 6A and 6B, another illustration of a fluctuating magnetic field generated using a non-contact tonometer (not shown) according to a third preferred embodiment of the present disclosure is shown. As shown in Figures 6A and 6B, the fluctuating magnetic field is generated by an electromagnetic exciter (not shown), and an induced current and a generated electromagnetic force (Fem) are applied to the cornea (indicated as 112 in Figure 1A) of the eye (indicated as 110 in Figure 1A). The fluctuating magnetic field is generated by the electromagnetic exciter with an induced current (I) and an electromagnetic force (Fem) applied to the cornea 514 of the eyeball 512. A steady magnetic field from at least one permanent magnet (not shown) is guided to the cornea of ​​the eye by at least one magnetic armature and, together with the fluctuating magnetic field generated by at least one electric coil (not shown), at least partially penetrates and closes the cornea. Here, the steady magnetic field generated by at least one permanent magnet 412 inside the eyeball has a radial component of magnetic induction (Br). An electromagnetic force (Fem) is generated by the interaction between the induced current (I) and the radial component of magnetic induction (Br).

[0087] Figures 6A and 6B are for illustrative purposes only and do not unduly limit the scope of the claims herein. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0088] Referring to Figure 7, a flowchart 700 is shown illustrating the steps of a method for measuring intraocular pressure according to an embodiment of the present disclosure. Step 702 involves vibrating the cornea of ​​the eye by applying a fluctuating magnetic field. Step 704 involves changing the frequency of the fluctuating magnetic field within a predetermined frequency range. Step 706 involves measuring at least the peak amplitude of the vibration of the cornea of ​​the eye. Step 708 involves detecting the minimum frequency corresponding to the peak amplitude to determine the resonant frequency of the cornea of ​​the eye. Step 710 involves calculating the intraocular pressure using the resonant frequency.

[0089] Steps 702, 704, 706, 708, and 710 are merely illustrative, and other options exist. That is, one or more steps can be added, one or more steps can be omitted, or one or more steps can be performed in a different order without departing from the scope of the appended claims.

[0090] It is possible to modify the embodiments of this disclosure described herein without departing from the scope defined by the attached claims. Expressions such as “includes,” “equip,” “incorporates,” “possesses,” and “is” used to describe and claim this disclosure are intended to be interpreted non-exclusively, that is, to allow for the existence of items, parts, or components not expressly described. The absence of explicit indication that an element is plural does not prevent the existence of multiple such elements.

Claims

1. Non-contact tonometer, Equipped with an excitation and measurement unit, The excitation and measurement unit has an electromagnetic exciter. The electromagnetic exciter is, - At least one electric coil, driven by a fluctuating current (i) and configured to generate a fluctuating magnetic field, - At least one magnetic armature configured to guide the fluctuating magnetic field toward the eye such that the fluctuating magnetic field passes through at least partially the cornea of ​​the eye, A non-contact tonometer equipped with [feature / feature].

2. The non-contact tonometer according to claim 1, wherein the electromagnetic exciter further comprises at least one permanent magnet.

3. The non-contact tonometer according to claim 1 or 2, wherein the excitation and measurement unit further comprises an optical displacement sensor.

4. The non-contact tonometer according to claim 3, wherein the optical displacement sensor is selected as at least one of a confocal chromatic displacement sensor or a laser Doppler vibrometer.

5. The non-contact tonometer according to claim 4, wherein the confocal chromatic displacement sensor is operable to measure using an infrared light beam.

6. The optical displacement sensor is, - The amplitude of vibration at at least one point on the cornea; - The thickness of the cornea at at least one of the aforementioned points; - The distance between the cornea and the excitation / measurement unit; A non-contact tonometer according to any one of claims 3 to 5, capable of measuring at least one of the following.

7. The non-contact tonometer according to any of the preceding claims, wherein the at least one magnetic armature is a U-shaped magnetic armature having a first arm having a first end and a second arm having a second end.

8. The non-contact tonometer according to claim 7, wherein the optical displacement sensor is positioned between the first arm and the second arm.

9. The non-contact tonometer according to claim 7 or 8, wherein the distance between the first arm and the second arm decreases toward the first and second ends.

10. The permanent magnet has a substantially annular shape and has a first pole on one of its two opposing faces and a second pole on the other; The electromagnetic exciter has a proximal end and a distal end, and has a spatial volume that extends along the centerline of the electromagnetic exciter from the proximal end to the distal end; The aforementioned at least one magnetic armature is - An internal magnetic armature that at least partially encloses the aforementioned spatial volume and is magnetically coupled to the first pole of the permanent magnet via the second end, - An external magnetic armature that at least partially surrounds the electric coil and is magnetically coupled to the second pole of the permanent magnet, The electric coil has a structure that at least partially surrounds the internal magnetic armature; A non-contact tonometer according to any one of claims 2 to 6.

11. The non-contact tonometer according to claim 10, wherein the optical displacement sensor is arranged within the spatial volume.

12. A method for measuring intraocular pressure, - Vibrating the cornea of ​​the eye by applying a fluctuating magnetic field, - Changing the frequency of the fluctuating magnetic field within a predetermined frequency range, - To measure at least the peak amplitude value of the corneal vibration, - In order to find the resonant frequency value of the cornea, the minimum value of the frequency corresponding to the peak amplitude value is found, - Calculating the intraocular pressure value of the eye using the aforementioned resonant frequency, Methods that include...

13. The method according to claim 12, wherein the fluctuating magnetic field is generated by a coil driven by a fluctuating current (i), and the frequency scanning of the fluctuating current is performed within a predetermined frequency range.

14. - Measure the thickness of the cornea at at least one point; - Measuring the resonant frequency value of the cornea; - Calculating the intraocular pressure value of the eye using both the resonant frequency value of the cornea and the thickness value of the cornea; The method according to claim 12 or 13, further comprising:

15. - To measure the distance between the cornea and the excitation / measurement unit; - The measured distance value is used as a feedback signal, and the excitation / measurement unit is placed in a desired position relative to the cornea; The method according to claims 12 to 14, further comprising:

16. The method according to any one of claims 13 to 15, wherein the electrical impedance of the coil is continuously measured during the frequency scanning of the fluctuating current, and the resonant frequency value is the lowest frequency of the current that causes the amplitude peak value of the electrical impedance of the coil.

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