Otonometer for measuring characteristics of eye and method thereof

Abstract

An tonometer (100, 200, 300, 400, 900) for measuring a characteristic of an eye (960). The invention relates to an ophthalmotonometer comprising: an execution unit (102, 202, 902) comprising an impingement member (104, 904) arranged to apply an impact on a cornea (962) of an eye when timing using intraocular pressure; comprising at least one optical sensor (108, 908); and, a controller (110, 910) coupled to the execution unit and the measurement unit, where the controller is configured, in use, to: operate the execution unit to apply an impact on the cornea of the eye with the impact member; and operating the at least one optical sensor to make multiple measurements of corneal displacement caused by the impact within a predetermined period of time.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a tonometer for measuring an eye characteristic. The present disclosure also relates to a method for measuring an eye characteristic. BACKGROUND

[0002] A tonometer is a medical device designed for examining an eye of a subject. The eye is examined by measuring various characteristics of the eye. For example, the characteristic is a pressure within the eye, referred to as intraocular pressure (IOP). The measured eye characteristic helps in diagnosing and managing various eye conditions, including glaucoma, which, if left untreated, can lead to a decrease in vision. Tonometers can be used to measure intraocular pressure (IOP). Typically, a tonometer is a fast, painless and non-invasive medical device.

[0003] Typically, there are various types of tonometers working on different principles, such as a Goldmann applanation tonometer and a re-bound tonometer. The Goldmann applanation tonometer is generally used as a gold standard for measuring IOP. However, this measurement requires a relatively long contact with the cornea and, thus, requires the use of anesthetic substances on the eye. In fact, the measurement with a Goldmann applanation tonometer causes discomfort and can cause potential damage to the corneal surface. The re-bound tonometer has an advantage over the Goldmann applanation tonometer in that it does not require anesthesia of the eye. In a re-bound tonometer measurement, a probe or the like is shot towards the cornea of the eye. The probe velocity curve is measured and, based on the measurement, an IOP value is determined.

[0004] Therefore, in view of the foregoing discussion, there is a need to overcome the aforementioned drawbacks associated with the prior art related to devices for measuring an eye characteristic. SUMMARY

[0005] The present disclosure seeks to provide a tonometer for measuring an eye characteristic. The present disclosure also seeks to provide a method for measuring an eye characteristic. It is an object of the present disclosure to provide a solution that at least partly overcomes the problems encountered in the prior art.

[0006] In one aspect, embodiments of the present disclosure provide a tonometer for measuring a characteristic of an eye, the tonometer comprising: an execution unit comprising an impact member arranged to exert an impact on a cornea of the eye when the tonometer is in use; a measurement unit comprising at least one optical sensor; and a controller connected to the execution unit and the measurement unit, wherein the controller is configured to, in use: operate the execution unit to exert the impact on the cornea of the eye with the impact member; and operating the at least one optical sensor to make a plurality of measurements of the corneal displacement caused by the impact over a predetermined period of time.

[0007] In another aspect, embodiments of the present disclosure provide a method for measuring a characteristic of an eye, the method comprising: generating an impact on a cornea of the eye with an impact member, and making a plurality of measurements of the corneal displacement caused by the impact over a predetermined period of time with a measurement unit.

[0008] Embodiments of the present disclosure substantially obviate one or more problems caused by limitations and disadvantages of the related art, and achieve improved, simple, compact, precise, reliable, and cost-effective tonometer. This is achieved by causing a vibration of the cornea with an impact member and measuring the vibration with at least one optical sensor. The vibration parameters, such as the frequency of the vibration, can be used to determine the intraocular pressure of the eye. In effect, the tonometer employs at least one optical sensor to enable measuring a characteristic of the eye with higher precision.

[0009] Other aspects, advantages, features and objects of the present disclosure will become more apparent as comparative embodiments thereof are described in detail with reference to the accompanying drawings in conjunction with the following detailed description.

[0010] It is to be understood that the features of the present disclosure can be combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] The above summary of the present disclosure is better understood when read in conjunction with the detailed description of illustrative embodiments thereof, when presented in conjunction with the following drawings, wherein:

[0012] Embodiments of the present disclosure will now be described, by way of example only, with reference to the following drawings. In the drawings, which are not to scale: Figure 1A is a block diagram illustrating a tonometer for measuring a characteristic of an eye according to an embodiment of the present disclosure; Figure 1B is a block diagram illustrating an execution unit of a tonometer according to an embodiment of the present disclosure; Figure 2 is a block diagram illustrating an execution unit of a tonometer according to another embodiment of the present disclosure; Figure 3 is a block diagram illustrating a tonometer according to another embodiment of the present disclosure; Figure 4 is a block diagram illustrating a tonometer according to another embodiment of the present disclosure; Figure 5 is a block diagram illustrating at least one optical sensor according to another embodiment of the present disclosure; Figure 6 is a flowchart depicting steps of a method for measuring a property of an eye according to an embodiment of the present disclosure; Figure 7 is a schematic illustration of corneal vibrations caused by an impact by an impact member; Figure 8 is a graphical illustration of a relationship between a vibration frequency and an intraocular pressure of an eye; Figure 9 is a schematic illustration of a tonometer and its use according to an embodiment of the present disclosure; and Figure 10 is a graphical illustration of a relationship between a damping factor and an intraocular pressure of an eye.

[0013] In the drawings, underlined numerals denote items that are discussed in the description in connection with the numerals. Un-underlined numerals refer to items that are identified in the description by lines linking the un-underlined numerals to the items. When a numeral is un-underlined and accompanied by an associated arrow, the un-underlined numeral is used to identify the overall item to which the arrow is pointing. DETAILED DESCRIPTION

[0014] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes for carrying out the present disclosure have been disclosed, one skilled in the art will recognize that other embodiments for carrying out or practicing the present disclosure are possible.

[0015] In one aspect, embodiments of the present disclosure provide a tonometer for measuring a property of an eye, the tonometer comprising: an execution unit comprising an impact member arranged to exert an impact on a cornea of the eye when the tonometer is in use; a measurement unit comprising at least one optical sensor; and a controller connected to the execution unit and the measurement unit, wherein the controller is configured to, in use: operate the execution unit to exert the impact on the cornea of the eye with the impact member; and operate the at least one optical sensor to make a plurality of measurements of a corneal displacement caused by the impact over a predetermined period of time.

[0016] In another aspect, embodiments of the present disclosure provide a method for measuring a property of an eye, the method comprising: Using an impact component to generate an impact on the cornea of ​​the eye, and Using a measuring unit, the corneal displacement caused by the impact is measured multiple times within a predetermined time period.

[0017] This disclosure provides the aforementioned tonometer and method, which are simple, cost-effective, robust, accurate, reliable, and user-friendly. In fact, the impact member contacts the cornea of ​​the eye and remains in contact for a short period of time. The contact time is less than the time it takes for a person to blink. Furthermore, the tonometer employs at least one optical sensor that provides accurate measurements of eye characteristics in a cost-effective manner.

[0018] According to embodiments of this disclosure, the term " Tonometer A tonometer is an instrument used to measure various characteristics of the eye. In this sense, characteristics refer to physiological parameters associated with the eye. Optionally, the eye parameter measured by a tonometer is intraocular pressure.

[0019] The term "in this article" Execution unit "" refers to the apparatus used to apply force (impact) to the cornea of ​​the eye. The term "" as used in this article Impact member "Impact" refers to a component used to impact a surface. The impact component is considered part of the actuation unit. In an embodiment, the impact component is used to impact the corneal surface of the eye. It should be understood that the impact component is arranged to generate an impact only on the cornea of ​​the eye, without impacting the entire eye or a large amount of tissue around the eye. The typical duration of the impact is in the range of 1 millisecond (msec) to 5 milliseconds, depending on the velocity and weight of the impact component and the characteristics of the eye (i.e., intraocular pressure and the elasticity of the eye surface). The duration can be 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0 up to 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0. Between 6.0 milliseconds. The impact is applied by launching an impact component at the surface of the eye. Therefore, an impact refers to a rapid touch / impact / application of a momentary force (pulse) onto the cornea of ​​the eye. The impact is applied to the cornea of ​​the eye to cause it to vibrate. The eye vibration caused by the short-duration impact is called the free vibration of the cornea. Advantageously, the duration of the impact is in the range of 1 to 5 milliseconds. In one embodiment, the tonometer is implemented as a spring-loaded tonometer, and the measurement of the vibration generated by the impact of the tonometer probe provides an accurate measurement of the intraocular pressure (i.e., IOP) value for the spring-loaded tonometer. In this way, IOP can be measured using two methods: the probe velocity profile and the vibration generated by the impact.

[0020] The term "in this article" Measurement unitThis refers to a component used to measure the free vibration of the cornea of ​​the eye. The measuring unit includes at least one optical sensor. This at least one optical sensor is used to measure the corneal displacement value caused by an impact within a predetermined time period. The impact causes the cornea to vibrate. Displacement refers to the movement of the corneal surface from its "normal" level. In practice, the term "optical sensor" is used to perform multiple measurements (e.g., in nanometers) of corneal displacement within a predetermined time period. In this way, a set of displacement (from 0 to the horizontal displacement) values ​​are collected over time, at least for the duration of the predetermined time period. The predetermined time period can be the time from the start of the impact to the end of the vibration (when the vibration is damped to a level that is typically insignificant about 50 milliseconds after the impact). The predetermined time period can also begin during or after the impact. Ideally, the predetermined time period lasts long enough to collect a sufficient number of data points to find the frequency of the vibration. It is expected that the vibration frequency is approximately 100 Hz to 500 Hz, i.e., from this perspective, the predetermined time should be at least The frequency range is from 1 to 10 vibrations (1 / 500 to 10 / 100 of a second). Optionally, the predetermined time interval is at least 0.001, 0.005, 0.01, 0.015, 0.020, 0.025, 0.030, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5, 1.0, or 2.0 seconds. Since the frequency is in the range up to 500 Hz, at least one optical sensor should be configured to perform 500 × 2⁻¹⁰ measurements per second, i.e., every… 1000 to 5000 measurements per second are performed to obtain sufficient sampling from the displacement. An alternative method for measuring displacement is to measure the "0-value" at (or just before) the impact, and then determine a binary value (e.g., a value of 1 if the corneal surface is closer to the retina than the 0-level, and a value of 0 if the corneal surface is farther from the 0-level) from the distance value. In this way, we can detect vibrations toward and away from the retina from the 0-value. The term "0-value" is used in this paper. Optical sensor A corneal transducer (CVT) is an instrument that works by providing a beam of light to the eye. The beam is reflected from the surface of the eye, and the reflection is analyzed to find the corneal displacement at a given moment during the measurement. As mentioned above, multiple measurements are performed to collect enough data to determine the displacement based on the measured vibration frequency. Furthermore, using optical sensors to collect multiple measurements of displacement over time provides several advantages, including high temporal resolution, allowing for precise characterization of rapid or instantaneous changes in displacement, dynamic behavior and response analysis, displacement pattern recognition, noise reduction, and improved quality of displacement data. It also provides statistical analysis of quantitative measurements of variability, stability, or statistical significance to generate deeper insights, adaptive control to optimize performance, maintain stability, or respond in real time to changing conditions, and long-term monitoring of displacement trends and patterns.

[0021] Typically, in rebound tonometers, the impact time between the probe and the eye is very short, allowing subsequent corneal oscillations to occur freely without external damage to the contact element (impact device, such as the probe). In contact vibration measurements, the contact element may direct its own weight and external force towards the cornea, interfering with the eye's vibrational characteristics and leading to inaccurate measurements. Furthermore, their longer contact time with the cornea and longer measurement time can potentially cause patient discomfort. Therefore, using a rebound tonometer with only 0.1 to 5 milliseconds of contact with the eye and employing an optical sensor to measure corneal vibrations non-contactly results in more accurate measurements, shorter measurement times, and greater patient comfort. Measuring corneal vibrations instead of simple rebound also improves accuracy compared to existing rebound tonometers because more data about eye characteristics are received in a single measurement.

[0022] Optionally, at least one optical sensor is selected from at least one of a chromatic confocal sensor, a laser Doppler vibrator, and a laser displacement sensor. The term "optical sensor" as used herein... Laser Doppler vibrometer A "laser Doppler vibrator" refers to a type of sensor used to measure the distance between a tonometer and the cornea of ​​the eye. In this case, a laser beam from a laser Doppler vibrator is directed at the cornea, and the amplitude and frequency of vibration are extracted from the Doppler shift of the reflected laser beam frequency caused by corneal motion. Typically, the output of the laser Doppler vibrator is a continuous analog voltage proportional to a target velocity component along the direction of the laser beam. This target velocity component can be used to derive the corneal displacement as a measurement.

[0023] The term "in this article" Laser displacement sensor A laser displacement sensor is a device that uses a laser beam to measure the distance between two objects. Time-of-flight (TOF) measurement technology can be used to design a laser displacement sensor. Optionally, the laser displacement sensor sends a laser pulse to the cornea and measures the time required for the pulse to bounce back to the cornea. The time of flight of the laser pulse is then used to determine the distance between the laser displacement sensor and the cornea, i.e., to measure the displacement.

[0024] The term "spectral confocal sensor" refers to a device that uses a high-dispersion objective lens to deliver a beam of light (typically white light) with a broad wavelength range to a target surface (such as the eye). The reflected light is analyzed using a spectrometer to identify which wavelength in the broad wavelength range has a peak in the spectrum. The peak wavelength corresponds to the distance between the sensor and the reflecting surface (the surface of the eye). Again, as described in the preceding embodiments, by performing multiple measurements consecutively, we are able to collect a sufficient dataset of corneal displacements changing over time. This data can be used to discover the eye's vibrational frequency. For example, as discussed, the number of measurements per second could be, for example, 1000 to 5000 times per second or higher, depending on the required accuracy. For example, 10k to 20k measurements per second could be used.

[0025] The measurement unit includes one or more optical sensors. Optionally, the measurement unit includes multiple optical sensors to improve the accuracy of IOP measurements. For example, different regions of the cornea may have different biomechanical properties. In this case, multiple optical sensors can measure the cornea from multiple angles or positions and provide more information for measuring eye characteristics.

[0026] Optionally, at least one optical sensor includes at least one light-emitting diode (LED) and at least one photoelectric sensor, wherein the at least one photoelectric sensor is selected from at least one of a phototransistor or a photodiode. The term "..." as used herein Light emitting diode A light source is a semiconductor device that emits light when an electric current flows through it. Furthermore, each of at least one optical sensor includes an LED as its light source. Photons emitted by the LED are directed to a target object, such as the cornea of ​​the eye. When the photons strike the cornea, some are reflected back to at least one optical sensor. Optionally, the amount of light reflected back to the at least one optical sensor depends on the reflectivity of the cornea. An advantage of using LEDs instead of lasers is that LEDs are not monochromatic. Monochromatic light emitted by lasers can have adverse effects on the retina. LEDs provide a relatively broad spectrum (compared to lasers).

[0027] The term "in this article" Phototransistor "Light" refers to a class of semiconductor devices used for detecting light. Furthermore, each of at least one optical sensor includes a phototransistor that operates in combination with an LED. The term "light" as used herein... Photo sensor ControllerA phototransistor is a device that detects light and converts it into an electrical signal. Furthermore, the phototransistor works in combination with an LED present in each of at least one optical sensor. Optionally, the phototransistor is a photodiode, a light-sensitive semiconductor device. Both phototransistors and photodiodes are fast-moving components, thus suitable for accurately measuring rapid transients, such as pulsed light sources. According to the implementation, the measured corneal displacement does not need to be an absolute value (such as nanometers), but sufficient to detect the time evolution of the displacement. For this purpose, using a pair of LEDs and a phototransistor can provide a time-varying photocurrent as the output. This photocurrent does not provide direct information about the actual amount of displacement (in meters). However, the time-varying photocurrent can be considered to represent relative displacement (between different moments) and can be used in further data processing to find the frequency of the vibration. Furthermore, the LED and photodiode combination is non-invasive and can be comfortably placed near the eye without causing discomfort or interfering with normal vision. An additional advantage of using LEDs and a phototransistor / phototransistor is the low cost of these components.

[0028] It should be understood that at least one optical sensor is positioned appropriately to accurately identify corneal vibrations. Preferably, the optical sensor is arranged close to the actuation unit, and more preferably, arranged to measure from the same direction as the direction in which the impact member is applied to the cornea. Optionally, the beam is preferably oriented perpendicular to the cornea. Advantageously, at least one optical sensor has the ability to allow a large angle (even tens of degrees) between the beam axis and the normal direction of the measured surface. It should be understood that at least one optical sensor is used to resolve displacement measurements in the tens of nanometers and has the ability to measure at frequencies in the tens of kilohertz (kHz). Advantageously, at least one optical sensor is customized to identify the vibration frequency of the cornea to make it cost-effective. Optionally, at least one optical sensor uses infrared light (IR) as the measurement beam. Advantageously, the subject's eye cannot see infrared light. In this case, the incentive for the subject to blink is reduced.

[0029] the term" Computing unit A controller is a computing device operable for controlling the overall operation of a tonometer. The controller performs tasks during operation, such as, but not limited to, using the execution unit, using the measurement unit, and responding to and processing information. In embodiments, the controller may be an embedded microcontroller, a microprocessor, etc. For this purpose, the controller is coupled to the measurement unit and the execution unit. The controller may be implemented as an internal component of the tonometer, an external component of the tonometer, or a combination thereof.

[0030] The controller is configured to operate the actuator by energizing it. At this point, the actuator is energized to apply an impact, i.e., a force, to the cornea of ​​the eye. It is worth noting that the eye is considered a thin-walled elastic container filled with a pressurized fluid. Therefore, the eye exhibits mechanical vibration behavior and resonant frequencies. Furthermore, when the cornea is impacted, it deforms and then rapidly returns to its original shape, generating vibrations on its surface. Vibration is the evolution of corneal surface displacement over time. The term "displacement" refers to the amplitude of the vibration.

[0031] In this paper, multiple measurements refer to measuring corneal displacement once or multiple times within a predetermined time period. For this purpose, multiple measurements provide more accurate and reliable data because they help resolve any variability or inconsistency in the measurements. Optionally, multiple measurements enable tracking the progression of corneal displacement over time and a better understanding of the effects of shocks on the cornea. In this paper, displacement refers to the change in corneal position caused by corneal vibrations. The frequency of multiple measurements is high enough to identify corneal vibrations.

[0032] The controller is configured to operate or energize the measuring unit. In this respect, the controller operates the measuring unit, which has at least one optical sensor, to measure corneal displacement. As an example, the photoelectric sensor includes an LED as a light emitter. The LED of the optical sensor sends (emits) a light beam onto the cornea, and a corresponding photodetector (such as at least one photoelectric sensor) measures the amount of light reflected back from the cornea to measure corneal displacement. In this embodiment, when the impact member strikes the cornea, the cornea deforms slightly. For this reason, the distance between at least one LED and at least one photoelectric sensor changes, causing a change in the amount of light reflected back to at least one photoelectric sensor. The change in the amount of reflected light can be used as the measured displacement (displacement value, such as X meters (e.g., -150 to 150 micrometers) from the "0-level" of the corneal surface, or as a change in current in the photoelectric sensor). Herein, the measuring unit is used to perform multiple measurements of corneal displacement caused by the impact within a predetermined time period.

[0033] Optionally, the tonometer also includes a computing unit coupled to the controller and operable to: The frequency of the free vibration of the cornea caused by the impact is calculated using the measured displacement; and The internal pressure of the eye is calculated using the frequency of the free vibration of the cornea (which can be assumed to be a function of the frequency of the free vibration of the cornea caused by an impact). In fact, the measured displacement (such as the amplitude of a movement away from the "zero" level) as a function of time provides a method for finding the vibration frequency. By finding the periodicity of the measurement, i.e., the time difference between two peaks or multiple pairs of peaks, and calculating their average, the frequency of the free vibration can be calculated from the measured displacement. Therefore, the frequency is the reciprocal of the found average time difference (1 / s = Hz). For example, the internal pressure of the eye can be found from the calculated frequency of the free vibration (undisturbed vibration) by using a lookup table with a correlation table between frequency and intraocular pressure (IOP). That is, the frequency of the free vibration of the cornea is used to calculate the internal pressure of the eye. An alternative calculation method is to use a mathematical model of eye vibration and use the frequency as the input value to the mathematical model.

[0034] Additionally, the tonometer may optionally include a computing unit coupled to the controller and operable to: The damping factor of the free vibration of the cornea caused by the impact is calculated using the measured displacement; and The internal pressure value of the eye is calculated using the damping factor.

[0035] In addition, the tonometer is configured to adjust the internal pressure value as follows: The internal pressure of the eye, calculated using a damping factor, is used to adjust the internal pressure of the eye, calculated using the frequency of free vibration. The internal pressure value of the eye, calculated using the frequency of free vibration, is adjusted by using the internal pressure value of the eye calculated using a damping factor.

[0036] The term "in this article" Emission member"Calculation unit" refers to electronic hardware or software algorithms used to perform mathematical operations to transform raw data into meaningful measurements. In this respect, the calculation unit is associated with the controller to allow for greater flexibility and customization of the tonometer based on its design. Optionally, the calculation unit is integrated into the controller; that is, it is part of the controller. Optionally, the calculation unit is implemented using cloud services. Furthermore, the calculation unit can operatively use the measured displacement (the value or index of the displacement) to calculate the frequency of free vibration of the cornea. Free vibration refers to the resonant frequency or natural vibration frequency of the cornea caused by impact. In practice, the cornea vibrates at a frequency equal to (or close to) the frequency of free vibration. The cornea vibrates freely at its resonant frequency, with the amplitude gradually decreasing until it stops. One method to calculate the frequency is to use the inverse Fourier transform. The frequency of the free vibration is related to the internal pressure of the eye, so by determining / measuring this frequency, it is possible to measure the value of the internal pressure of the eye (intraocular pressure, IOP). Another method to calculate the frequency is by comparing the "0-level" crossover obtained from the optical sensor. This simplifies the process because we can easily calculate the time it takes to change from 1 (indicating that the corneal surface is closer to the retina than normal) and 0 (indicating that the corneal surface is farther from the retina than normal) and from 1 to 0.

[0037] As mentioned above, the cornea vibrates at a frequency of free vibration. The amplitude of the vibration decreases over time (from a few milliseconds to 100 milliseconds). This decrease in amplitude can be described by the damping factor of the vibration. Furthermore, multiple measured displacement values ​​(as a function of time) can be used to calculate the internal pressure value of the eye. Thus, by performing multiple measurements of corneal displacement caused by impact, IOP (intraocular pressure) can be measured (indirectly) via the damping factor. Generally speaking, the eye can be considered as a harmonic oscillator. The basic equation of a harmonic oscillator is:

[0038] Where x is the measured displacement value (from the normal level), i.e., the amplitude; t is time, ω is frequency, and ζ is the damping factor. Solving for x(t) yields the displacement as a function of time:

[0039] In fact, by taking multiple displacement measurements over a period of time, we can obtain data points x(t). These can be used to calculate the frequency and damping factor.

[0040] Based on experiments, in addition to frequency, the damping factor can be used to define the internal pressure value of the eye. This can be done, for example, through curve fitting, using a lookup table, or a predetermined equation. Using a damping factor is advantageous because the error tolerance associated with its determination is small. An alternative method for calculating the damping factor is to find the maximum and minimum values ​​of each oscillation from the peak displacement values ​​of multiple measurements performed. The peak maximum and minimum values ​​can be used to find the damping by comparing, for example, two different peak maximum values.

[0041] According to an alternative embodiment, the internal pressure value of the eye is calculated using the frequency of free vibration, and this value is adjusted based on the internal pressure value calculated using a damping factor. According to another alternative embodiment, the internal pressure value of the eye is calculated using a damping factor, and this value is adjusted based on the internal pressure value calculated using the free vibration frequency of the cornea. This improves the accuracy of the measurement.

[0042] The term "internal pressure" (i.e., intraocular pressure (IOP)) used in this paper refers to the fluid pressure within the eye. Optionally, the computational unit can apply different mathematical models, such as regression analysis or curve fitting, to the raw data to obtain the most accurate and reliable measurement of the intraocular pressure value. Optionally, the computational unit can perform other functions, such as error correction, data storage, and data analysis. It is noteworthy that determining the intraocular pressure value is crucial for maintaining overall eye health and function. Optionally, the eye presents as a mass-spring system, where IOP describes the spring constant. Optionally, when the cornea is displaced from its natural position by an external force, it acts as a damped resonator, vibrating at a frequency relative to the IOP. The IOP modulates the stiffness of the eye and the cornea such that the vibration frequency increases with increasing IOP. It should be understood that measuring the intraocular pressure value enables the diagnosis and treatment of high intraocular pressure before the development of eye-related diseases. Furthermore, determining the size is used for diagnosing eye growth regulation, and determining touch sensitivity is used for treating eye-related diseases such as conjunctivitis, corneal infections, glaucoma, dry eye, etc.

[0043] The frequency and damping factor of free corneal vibrations can provide valuable information for assessing IOP based on biomechanical properties (including corneal stiffness and elasticity) that affect how the cornea responds to changes in IOP. Notably, corneal thickness varies from person to person, affecting the accuracy of intraocular pressure (IOP) measurements. By taking into account corneal biomechanical properties such as frequency and damping factor, IOP estimates using a simple tonometer can be obtained that are less dependent on corneal thickness, potentially improving accuracy, especially in patients with abnormal corneal thickness. Furthermore, IOP calculations based on the frequency and damping factor of free corneal vibrations provide a more comprehensive understanding of the factors contributing to ocular pathology and allow for the development of tailored treatment strategies accordingly. For example, changes in corneal biomechanics over time (including changes in the frequency and damping factor of corneal vibrations) can be monitored to aid in the early detection and management of glaucoma or corneal ectasia by providing additional indicators of eye health, disease progression, or treatment effectiveness beyond traditional IOP measurements, ultimately improving clinical decision-making and patient care.

[0044] Optionally, the impact member of the actuator is a solid probe, and the actuator also includes a firing member operable to fire the solid probe toward the eye to generate an impact.

[0045] The term "in this article" Feedback element A "launching member" refers to a mechanical element used to launch at least one solid probe from an actuating unit toward the eye (or in the direction of the eye). In this respect, the launching member enables the solid probe to be moved effectively and accurately during use. For example, the solid probe may be an elongated probe having a magnetic elongated body and a biocompatible tip portion. In this embodiment, the launching member partially surrounds the magnetic elongated body of the solid probe. Hereinafter, the launching member is arranged as a set of (electric coil) loops through which at least one solid probe can move. When current is supplied through this set of loop members, the launching member moves at least one solid probe. The current generates a magnetic field in the loop, which moves the probe (because it has a magnetic elongated body at least partially arranged inside the loop). The launching member launches the solid probe toward the eye at a certain velocity, where the velocity is a function of the current supplied through the loop of the launching member and the magnetization of the solid probe body. It should be understood that the launching member and at least one solid probe work together to produce an accurate impact on the cornea of ​​the eye, meaning at the correct point on the cornea.

[0046] Optionally, the impact member of the actuator is at least one drop of liquid, and the actuator also includes a firing member operably configured to fire at least one drop of liquid toward the eye to generate an impact.

[0047] In this text, the emitting element refers to another mechanical component used to release or emit one or more drops of liquid toward the eye to generate an impact on the cornea. Optionally, at least one drop of liquid is selected from at least one of water, saline, or a physiological solution. Optionally, at least one drop of liquid is water. Optionally, the water droplet can be a non-irritating liquid that can be emitted toward the eye without causing harm or discomfort. Optionally, at least one drop of liquid is saline. Typically, saline is a sterile solution of water and salt used for various purposes, such as eye irrigation. Eye irrigation is the process of rinsing the eye with a stream of liquid to remove foreign objects, irritants, or chemicals that may have entered the eye. Optionally, at least one drop of liquid is a physiological solution. In this respect, when operated, the controller is configured to operate the actuator in such a way that the emitting element associated therewith emits at least one drop of liquid toward the eye to generate vibration in the cornea. As discussed, the frequency of the vibration represents the value of IOP. It is worth noting that a higher IOP indicates increased rigidity of the eyeball, and therefore an increased resonant frequency of the cornea. In alternative or additional embodiments, the liquid may be a drug, and the tonometer is configured to administer the drug. Measurements can be used to detect whether a drug has been administered (by detecting, with an optical sensor, the presence of movement in the cornea caused by the administered drug).

[0048] Optionally, at least one drop of liquid is stored in a hollow container. Optionally, the hollow container is disposed inside at least one solid probe associated with the emission member. It should be understood that the emission member works in combination with at least one solid probe to deliver an optimal amount of at least one drop of liquid to the cornea. Advantageously, when at least one drop of liquid is delivered in an optimal amount, it produces a precise impact on the cornea of ​​the eye.

[0049] Advantageously, applying at least one drop of liquid to the eye is a non-invasive method that minimizes the risk of discomfort, harm, and / or side effects to the patient. Furthermore, applying at least one drop of liquid to induce corneal vibration can be standardized and reproducible across different patients, ensuring protocol consistency and facilitating comparisons between studies. Additionally, by controlling the droplet volume and composition, the amplitude and frequency of induced corneal vibrations in the eye can be modulated. This allows for precise manipulation of experimental conditions, such as fluctuations in external stimuli or ocular conditions, to study their effects on IOP dynamics, such as in glaucoma, and helps identify biomarkers or patterns indicative of disease progression or treatment response.

[0050] Optionally, the tonometer also includes: - At least one sensor element operable for measuring the distance between the eye and a tonometer, and A feedback element coupled to at least one sensor element and operable to provide feedback based on the measured distance; The feedback is selected from at least one of visual feedback, auditory feedback, or feedback signal.

[0051] In this document, a sensor element refers to a device that detects and responds to physical changes in its environment. In this document, a tonometer includes one or more sensors for converting physical phenomena (such as light, motion, etc.) into electrical or digital signals that can be measured or processed. Optionally, at least one sensor is an internal component or an external component of the tonometer. Optionally, at least one sensor element can be used alone or in combination with other sensors to provide more complex and detailed measurements of the monitored environment or system. The term "…" is used herein. Actuator A feedback element refers to an electronic component that provides information about the sensor's output and allows adjustments to the sensor's input or output in response to that information. Optionally, the feedback element can be a physical component (such as a potentiometer) or a digital component (such as a microcontroller). It should be understood that the feedback element is used to improve the accuracy and reliability of at least one sensor element by detecting errors or differences between the desired distance value and the measured distance value and making adjustments to correct them.

[0052] In this respect, during operation, at least one sensor element is operable to measure the distance between the cornea and the tonometer, and provides the measured distance as feedback to a coupled feedback element. The feedback element compares the measured distance of the at least one sensor element with a reference value (such as a desired or optimal distance), and the controller adjusts the sensor input based on the difference between the two values. It should be understood that when the tonometer is a handheld unit, at least one sensor works in conjunction with the feedback element to correctly position the tonometer relative to the eye. Furthermore, feedback is provided as visual feedback. For example, the measured distance is displayed on the device's screen. Optionally, visual feedback is represented in the form of text or graphic information. Additionally, feedback is provided as auditory feedback. For example, the measured feedback is provided to the operator of the tonometer as audio feedback via a speaker associated with the device. Advantageously, visual or auditory feedback is used to aid in the correct positioning of the tonometer relative to the eye. Furthermore, feedback can be provided as a feedback signal. The feedback signal is an electrical signal (such as a command, voltage value, or bit stream) that can be provided to other electrical components to control those components or to provide control commands to them.

[0053] Optionally, the tonometer also includes: At least one actuator operable to automatically change the relative position of the tonometer with respect to the cornea of ​​the eye based on a feedback signal.

[0054] The term "in this article" Figure 1AA tonometer is a component responsible for automatically changing its relative position to the eye based on feedback signals received from a feedback element. Optionally, this may involve moving the tonometer closer to or further from the eye, or adjusting its angle or orientation. Examples of actuators include motors, solenoids, and piezoelectric devices. In this respect, the tonometer is positioned relative to the eye by means of at least one actuator, wherein a position feedback signal is obtained by measuring the distance between the tonometer and the eye by means of at least one sensor element. For example, if the measured distance is greater than a desired distance, the feedback element can be operated to provide a feedback signal to the actuator, which can then be operated to move the tonometer to an optimal position relative to the eye.

[0055] Optionally, at least one sensor element is selected from a laser displacement sensor. In this respect, the tonometer is associated with one or more sensor elements for providing positional feedback. Positional feedback is provided at least during the initial stage of the tonometer's positioning relative to the cornea, before the cornea enters the measurement area of ​​a given optical sensor. Optionally, when the cornea is within the measurement area of ​​the given optical sensor, positional feedback can be obtained using the given optical sensor, or the laser displacement sensor can continue to be used. Advantageously, the laser displacement sensor is a low-cost sensor.

[0056] The disclosed tonometer is capable of measuring corneal displacement over the entire or partial free vibration period to determine the accurate intraocular pressure of the eye by employing a contact tonometer, i.e., using a tonometer implemented with a spring-loaded tonometer. In this respect, the tonometer uses an actuation unit including an impact member and a measurement unit including at least one optical sensor, wherein the impact member is arranged to apply an impact to the cornea of ​​the eye when using the tonometer, wherein the impact is in the range of 0.1 to 5 milliseconds. When using a spring-loaded tonometer, the probe of the spring-loaded tonometer impacts the cornea of ​​the eye, causing displacement of the cornea, and then the free vibration is measured. However, the probe only impacts the cornea of ​​the eye for a short impact time, and the contact time is insufficient to measure corneal vibration to obtain an accurate intraocular pressure value. Furthermore, the measurement using an optical sensor allows for the measurement of corneal displacement over a longer period without contact with the eye, which allows for more accurate measurements, and consequently, more accurate intraocular pressure values. Furthermore, the use of optical sensors solves the technical problem of how to measure corneal displacement throughout the entire free vibration cycle, so as to determine the accurate intraocular pressure of the eye using a spring-loaded tonometer (i.e., a contact tonometer) without the need for a non-contact tonometer.

[0057] This disclosure also relates to the method described above. With respect to the first aspect mentioned above, the various embodiments and variations disclosed herein are applicable to this method after necessary adjustments.

[0058] According to one embodiment, eye characteristics are measured by generating an impact on the cornea of ​​the eye using an impact member. The impact causes corneal vibration. According to this method, multiple measurements of displacement (related to corneal vibration) are performed within a predetermined time period. The predetermined time period is, for example, the duration of the vibration. Multiple measurements are completed to collect displacement (value / index) as a function of time. The impact can be generated using an impact member of an execution unit. At least one optical sensor can be used for displacement measurement.

[0059] Optionally, the method further includes: - The frequency of free corneal vibration caused by the impact was calculated using multiple measurements of corneal displacement; and The intraocular pressure is calculated from the frequency of the free vibration of the cornea caused by the generated impact. The intraocular pressure is a function of the measured frequency. This value can be determined using a device-specific function or lookup table.

[0060] Optionally, multiple displacement measurements are performed using at least one optical sensor selected from at least one of a confocal chromatograph sensor, a laser Doppler vibrator, or a laser displacement sensor.

[0061] Optionally, the at least one optical sensor includes at least one light-emitting diode (LED) and at least one photoelectric sensor, wherein the at least one photoelectric sensor is selected from at least one of a phototransistor or a photodiode.

[0062] Optionally, the method further includes: Measuring the distance between the cornea and the tonometer, and The measured distance is used as a feedback signal to move the actuator to the desired position relative to the cornea.

[0063] Optionally, an impact on the cornea is generated by releasing at least one probe into the eye, the at least one solid probe being contained in the execution unit.

[0064] Optionally, the method includes using multiple measurements of corneal displacement to calculate a damping factor for free corneal vibration caused by an impact; and using the calculated damping factor to calculate the internal pressure value of the eye.

[0065] According to one embodiment, a tonometer for measuring eye characteristics is provided. The tonometer includes: - An actuation unit including an impact member arranged to apply an impact to the cornea of ​​the eye when using an intraocular tonometer, wherein the duration of the impact is in the range of 0.1 to 5 milliseconds; A measurement unit including at least one optical sensor; Computational unit; and A controller coupled to the execution unit, measurement unit, and computing unit; The controller is configured for use when: The operating unit uses an impact component to apply an impact to the cornea of ​​the eye; Operate at least one optical sensor to perform multiple measurements of corneal displacement caused by impact within a predetermined time period; and The calculation unit uses the measured displacement to calculate the frequency of the corneal free vibration caused by the impact, and uses the frequency of the corneal free vibration to calculate the internal pressure value of the eye, or The calculation unit uses the measured displacement to calculate the damping factor of the corneal free vibration caused by the impact, and uses the damping factor to calculate the internal pressure value of the eye. The impact component of the execution unit is a solid probe, and the solid unit also includes: Launching components, The launching component is operable to launch a solid probe toward the eye to generate an impact. Alternatively, a combination of the frequency of free vibration and the damping factor can be used to calculate the internal pressure value of the eye.

[0066] Detailed description of the attached figures refer to Figure 1B A block diagram of a tonometer 100 for measuring eye characteristics according to an embodiment of the present disclosure is shown. As shown, the tonometer 100 includes an execution unit 102 including an impact member 104 arranged to apply an impact to the cornea of ​​the eye. Furthermore, the tonometer 100 includes a measurement unit 106 including at least one optical sensor 108, and a controller 110 coupled to the execution unit 102 and the measurement unit 106. It should be understood that the controller 110 is configured to operate the execution unit 102 to apply an impact to the cornea of ​​the eye using the impact member 104, and to perform multiple measurements of corneal displacement caused by the impact using at least one optical sensor 108 within a predetermined time period. Additionally, the tonometer 100 includes a calculation unit 112 coupled to the controller 110, operable to calculate the frequency of free corneal vibration caused by the impact using the multiple measurements of corneal displacement, and to calculate an intraocular pressure value as a function of the frequency of free corneal vibration caused by the impact.

[0067] refer to Figure 1A The figure shows a block diagram of an actuation unit 102 of an intraocular tonometer 100 according to an embodiment of the present disclosure. As shown, the actuation unit 102 further includes a firing member 114 and at least one solid probe 116, wherein the firing member 114 is operable to fire at least one solid probe 116 toward the eye to generate an impact.

[0068] Figure 1B and Figure 2 These are merely examples and should not unduly limit the scope of the claims herein. Those skilled in the art will recognize many variations, alternatives, and modifications to the embodiments disclosed herein.

[0069] refer to Figure 3 The figure shows a block diagram of the execution unit 202 of a tonometer 200 according to another embodiment of the present disclosure. As shown, the execution unit 202 further includes a firing member 204 and at least one drop of liquid 206, wherein the firing member 204 is operable to fire at least one drop of liquid 206 toward the eye to generate an impact.

[0070] refer to Figure 4 The diagram illustrates a block diagram of a tonometer 300 according to another embodiment of the present disclosure. Optionally, the tonometer 300 further includes: at least one sensor element 302 operable to measure the distance between the cornea of ​​the eye and the tonometer 300; and a feedback element 304 coupled to the at least one sensor element 302 and operable to provide feedback based on the measured distance. Optionally, the feedback is selected from at least one of visual feedback, auditory feedback, and feedback signals.

[0071] refer to Figure 5 The diagram illustrates a block diagram of a tonometer 400 according to another embodiment of the present disclosure. Optionally, the tonometer 400 further includes at least one sensor element 402 operable to measure the distance between the eye (not shown) and the tonometer 400. Additionally, the tonometer 400 may optionally include at least one actuator 404 operable to automatically change the relative position of the tonometer 400 with respect to the cornea of ​​the eye, wherein the measured distance between the tonometer 400 and the cornea serves as a feedback signal to automatically control the relative position between the tonometer 400 and the cornea.

[0072] refer to Figure 2 The diagram illustrates a block diagram of at least one optical sensor 500 according to an embodiment of the present disclosure. As shown, the at least one optical sensor 500 includes at least one LED 502 and at least one photoelectric sensor 504. Optionally, the at least one photoelectric sensor 504 is selected from at least one of a phototransistor and a photodiode.

[0073] Figure 3 , Figure 4 , Figure 5 and Figure 6 These are merely examples and should not unduly limit the scope of the claims herein. Those skilled in the art will recognize many variations, alternatives, and modifications to the embodiments disclosed herein.

[0074] refer to Figure 7The diagram illustrates a flowchart of the steps of a method for measuring eye characteristics according to an embodiment of the present disclosure. In step 602, an impact is generated on the cornea using an impact member of an actuation unit included in a tonometer. In step 604, the corneal displacement caused by the impact is measured multiple times within a predetermined time period using a measuring unit.

[0075] Figure 8 The diagram shows the measurement results of corneal displacement caused by an impact over a predetermined time period. The X-axis represents time in arbitrary units. The Y-axis represents displacement in arbitrary units. It can be seen that the frequency 764A (solid line) of the first set of measurements is lower than the frequency 764B (dashed line) of the second set of measurements. The graph can be obtained by performing multiple measurements of displacement as a function of time. For example, if the total duration of the predetermined time period is 50 milliseconds, the number of measurements during said time period can be, for example, 20, 50, 100, 1000, or 10000. These measurements can be used to determine the frequency of the vibration.

[0076] Figure 9 This is a graph showing the correlation between vibration frequency (Hz) and intraocular pressure (mmHg). It can be seen that a larger frequency indicates a larger pressure value, and vice versa. Figure 10 This is an illustration of the steps of using a tonometer 900 according to an embodiment of the present disclosure. The tonometer 900 includes an actuation unit 902. The actuation unit includes an impact member 904. In this figure, the impact member is a solid probe having a tip portion 930 connected to an elongated magnetic body 932. The elongated magnetic body is surrounded by an electrical circuit 903 portion of the actuation unit 902.

[0077] The measuring unit 906 is connected to the body of the tonometer 900 in such a way that, when the tonometer is used, the measuring unit 906 is pointed at the eye 960. The measuring unit includes at least one optical sensor 908. A controller 910 is coupled to the execution unit 902 and the measuring unit 906. In step S1, the controller operates the execution unit 902. In this embodiment, the electrical circuit 903 is energized. The current flowing through the electrical circuit 903 generates an electric field, which in turn generates a magnetic force on the elongated magnetic body 932 of the impact member 904. This force propels the impact member toward the cornea 962 of the eye 960 (as indicated by the arrow). In step S2, the impact member 904, as shown, applies an impact to the cornea 962. That is, the tip portion 930 collides with the cornea 962 of the eye 960.

[0078] Due to the elasticity of the eye 960, the impact member 904 springs back after the impact is applied, as indicated by the arrow in step S3. According to an alternative embodiment, the execution unit 902 can be configured to actively pull back the impact member 904 after the impact. This can be achieved by reversing the current direction in the electrical circuit 903 relative to the firing direction. After the impact, the cornea 962 vibrates. Vibration 964 is indicated by a thick line in the figure. The optical sensor 908 of the measurement unit 906 measures the vibration displacement caused by the impact multiple times within a predetermined time period. The measurement results are stored in the memory of the controller 910 for further data processing. The controller may include a calculation unit (or a separate calculation unit may exist). The calculation unit is used to use the stored measurements and these measurements to calculate the frequency of free vibration (e.g., through Fourier analysis). Furthermore, this frequency is used to calculate (using a lookup table or equation) the internal pressure value of the eye.

[0079] ​ This is a graph illustrating the relationship between the damping factor (amplitude decrease over time) of vibrations from a set of experiments. The x-axis of the graph represents the intraocular pressure (IOP) of the eye (in mmHg), and the y-axis represents the damping factor. It can be seen that, particularly for lower pressures (below 20 mmHg), the damping factor provides a good indication of pressure with a good level of confidence. In fact, the damping factor can provide better adjustment (calibration / correction) for IOP measured at frequency in the lower range compared to the higher range. According to one embodiment, if the IOP is below 15, 20, 25, 30, or 40 mmHg as IOP values, the damping factor is used, or the IOP value measured using the frequency of free vibration is adjusted. Advantageously, the disclosed tonometer can be calibrated periodically to ensure accuracy, helping to maintain the reliability of measurements and ensure the proper functioning of the tonometer.

[0080] The steps described above are merely illustrative, and other alternatives may be provided without departing from the scope of the claims herein, such as adding one or more steps, removing one or more steps, or providing one or more steps in a different order.

[0081] Modifications to the embodiments of the present disclosure described above may be made without departing from the scope of the disclosure as defined by the appended claims. Expressions such as “comprising,” “including,” “containing,” “having,” and “is” used to describe and claim the present disclosure are intended to be interpreted in a non-exclusive manner, allowing for the presence of items, parts, or elements not explicitly described. The singular references should also be interpreted to refer to the plural.

Claims

1. A tonometer (100, 200, 300, 400, 900) for measuring characteristics of an eye (960), said tonometer comprising: An execution unit (102, 202, 902) includes an impact member (104, 904) arranged to apply an impact to the cornea (962) of the eye when the tonometer is used; A measurement unit (106, 906) including at least one optical sensor (108, 908); and A controller (110, 910) coupled to the execution unit and the measurement unit. The controller is configured to, when in use: Operate the actuator to apply an impact to the cornea of ​​the eye using the impact member; and The at least one optical sensor is operated to perform multiple measurements of corneal displacement caused by the impact within a predetermined time period.

2. The tonometer (100, 200, 300, 400) according to claim 1 further includes a calculation unit (112), said calculation unit (112) being coupled to the controller (110) and operable for... The frequencies of the free vibrations of the cornea caused by the impact (964, 764B, 764A) were calculated using the measured displacement; and The internal pressure value of the eye is calculated using the frequency of the free vibration of the cornea.

3. The tonometer (100, 200, 300, 400) according to claim 1 further includes a calculation unit (112), said calculation unit (112) being coupled to the controller (110) and operable for... The damping factor of the free vibration of the cornea caused by the impact is calculated using the measured displacement; and The internal pressure value of the eye is calculated using the damping factor.

4. The tonometer according to claims 2 and 3, wherein: The internal pressure value of the eye, calculated using the damping factor, is adjusted to the internal pressure value of the eye, calculated using the frequency of the free vibration. The internal pressure value of the eye, calculated using the frequency of the free vibration, is adjusted by using the internal pressure value of the eye calculated using the damping factor.

5. The tonometer (100, 200, 300, 400) according to any one of the preceding claims, wherein, The at least one optical sensor is selected from at least one of a spectral confocal sensor, a laser Doppler vibrator, or a laser displacement sensor.

6. The tonometer (100, 200, 300, 400) according to any one of claims 1 to 4, wherein, The at least one optical sensor includes at least one light-emitting diode and at least one photoelectric sensor, wherein the at least one photoelectric sensor is selected from at least one of a phototransistor or a photodiode.

7. The tonometer (100, 200, 300, 400) according to any one of the preceding claims, wherein, The impact component of the execution unit is a solid probe, and the execution unit also includes a launching component (114) wherein the launching component is operable to launch the solid probe toward the eye to generate an impact.

8. The tonometer (100, 200, 300, 400) according to any one of claims 1 to 6, wherein, The impact component of the actuation unit is at least one drop of liquid, and the actuation unit also includes... Launching component (204); and Furthermore, the launching member is operable to launch at least one drop of liquid toward the eye to generate an impact.

9. The tonometer (100, 200, 300, 400) according to claim 8, wherein, The at least one drop of liquid (206) is selected from at least one of water, saline or physiological solution.

10. The tonometer (100, 200, 300, 400) according to any one of the preceding claims further includes... At least one sensor element (302, 402), said at least one sensor element being operable for measuring the distance between the eye and the tonometer; and A feedback element (304), coupled to the at least one sensor element, operable to provide feedback based on the measured distance; The feedback is selected from at least one of visual feedback, auditory feedback, or feedback signal.

11. The tonometer (100, 200, 300, 400) according to claim 10 further comprises at least one actuator (404) operable to automatically change the relative position of the tonometer with respect to the cornea of ​​the eye based on the feedback signal.

12. The tonometer (100, 200, 300, 400) according to at least one of claims 10 or 11, wherein, The at least one sensor element (302, 402) is a laser displacement sensor.

13. The tonometer according to any one of the preceding claims, wherein, The duration of the impact ranged from 0.1 milliseconds to 5 milliseconds.

14. A method for measuring characteristics of the eye, the method comprising: Using an impact component to generate an impact on the cornea of ​​the eye, and The corneal displacement caused by the impact was measured multiple times within a predetermined time period.

15. The method of claim 14, further comprising: The frequency of free vibration of the cornea caused by the impact is calculated by using multiple measurements of the corneal displacement. and The internal pressure value of the eye is calculated from the frequency of the free vibration of the cornea caused by the generated impact.

16. The method of claim 14, further comprising: The damping factor of the free vibration of the cornea caused by the impact was calculated using multiple measurements of the corneal displacement. and The internal pressure value of the eye is calculated using the calculated damping factor.

17. The method according to claims 14 to 16, wherein, The displacement is measured multiple times using at least one optical sensor selected from at least one of a spectral confocal sensor, a laser Doppler vibrator, or a laser displacement sensor.

18. The method according to claims 14 to 17, wherein, The displacement is measured multiple times using at least one optical sensor, the at least one optical sensor including at least one light-emitting diode (LED) and at least one photoelectric sensor, wherein the at least one photoelectric sensor is selected from at least one of a phototransistor or a photodiode.

19. The method according to any one of claims 14 to 18, further comprising: Measuring the distance between the cornea of ​​the eye and the tonometer, and The measured distance is used as a feedback signal to move the tonometer to the desired position relative to the cornea.

20. The method according to any one of claims 14 to 19, wherein, The impact component is either a solid probe or at least a drop of liquid.

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