Tonometers and related methods for determining the characteristics of the eye

Abstract

A tonometer (100, 200) for measuring the characteristics of an eye (110) is disclosed. The tonometer comprises an execution unit (120) having an impact means (130) configured to impact the cornea of ​​the eye when in use, at least one measuring unit (140, 202), a first confocal chromatic sensor (150, 204), and a controller (160, 206) connected to the execution unit, the measuring unit and the first confocal chromatic sensor, wherein the controller is configured to impact the cornea of ​​the eye with the impact means using the execution unit when in use, to determine an intraocular pressure value using the measuring unit and to measure the corneal thickness value of the eye using the first confocal chromatic sensor, wherein the measuring unit (140) is a velocity measuring unit that measures the velocity profile of the impact means during impact, and the controller is configured to determine an intraocular pressure value using the measured velocity profile.

Description

Technical Field

[0001] The disclosure of the present application (hereinafter referred to as the present disclosure) relates to a tonometer for measuring the characteristics of an eye. The present disclosure also relates to a method for measuring the characteristics of an eye.

Background Art

[0002] Intraocular pressure (IOP) is one of the most important risk factors in the onset and progression of glaucoma, which is a major cause of irreversible blindness worldwide. Therefore, it is extremely important to suppress its increase. Glaucoma is a group of eye diseases characterized by progressive damage to the optic nerve, and if treatment is neglected, vision loss or blindness often occurs. An increase in IOP may damage the optic nerve by compressing blood vessels and reducing blood flow to the optic nerve.

[0003] Intraocular pressure (IOP) can be measured by various techniques. As an example, a Goldmann applanation tonometer is used for measuring IOP. In this type of tonometer, the pressure is determined by measuring the force applied to the cornea by a part of the device. The IOP value can be calculated from the measured force. As an alternative, a rebound tonometer can be used. In a rebound tonometer, a projectile is fired towards the cornea and its change in velocity is measured. The IOP value is calculated from this change in velocity (velocity profile). The problem with these techniques is that the derived IOP value is a theoretical value based on physiological assumptions of the eye. For example, the Goldmann applanation method is based on an assumption regarding the thickness of the eye. Here, a standard corneal thickness of 520 micrometers is assumed. If the assumption is incorrect, the measurement result does not provide an accurate value. Similarly, the measured values of a rebound tonometer may also be inaccurate for users with corneal characteristics different from the underlying model and tests. These may lead to measurement errors in the IOP value. Measurement errors in medical devices can lead to misdiagnosis and endanger the health of patients.

[0004] Therefore, based on the above discussion, there is a need to overcome the above-mentioned drawbacks associated with conventional tonometers and conventional methods for measuring IOP using tonometers.

Summary of the Invention

[0005] This disclosure aims to provide a tonometer for determining the characteristics of an eye. This disclosure also aims to provide a method for determining the characteristics of an eye. The purpose of this disclosure is to provide a solution that overcomes, at least partially, the problems encountered in the prior art.

[0006] In one aspect, embodiments of the present disclosure provide a tonometer for determining the characteristics of the eye. This tonometer is An execution unit equipped with an impact mechanism configured to deliver an impact to the cornea of ​​the eye during use; • At least one measuring unit; • With the first confocal chromatic sensor; The execution unit, the measurement unit, and the controller connected to the first confocal chromatic sensor; Equipped with, The aforementioned controller, during use, The execution unit is used to apply an impact to the cornea of ​​the eye using the aforementioned impact means. • Using the at least one measuring unit to determine the intraocular pressure value of the eye, The first confocal chromatic sensor is used to measure the corneal thickness of the eye. It is configured in this way.

[0007] In another aspect, embodiments of the present disclosure provide a method for measuring the characteristics of the eye. This method is a) an execution unit including an impact means configured to deliver an impact to the cornea of ​​the eye when in use, wherein the execution unit provided in the tonometer delivers an impact to the cornea of ​​the eye; b) Measuring the intraocular pressure of the eye using at least one measuring unit provided in the tonometer; c) Measuring the corneal thickness of the eye using at least one confocal chromatic sensor provided in the tonometer; Includes.

[0008] Embodiments of the present disclosure substantially resolve, or at least partially resolve, the aforementioned problems in the prior art, enabling precise detection of intraocular pressure and corneal thickness values ​​using a non-invasive tonometer.

[0009] Further aspects, advantages, features, and objectives of what is disclosed herein will be revealed by the accompanying drawings and the detailed description of exemplary embodiments, which shall be interpreted together with the accompanying claims.

[0010] 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]

[0011] 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 1] This is a schematic diagram of a tonometer for measuring the characteristics of the eye, according to one embodiment of the present disclosure. [Figure 2] This is a block diagram of a tonometer used to measure the characteristics of the eye. [Figure 3] This is a graph showing the vibration of the cornea over time, according to an embodiment of the present disclosure. [Figure 4] This flowchart shows the steps of a method for measuring eye characteristics according to one embodiment of the present disclosure. [Figure 5]This is an illustration of a tonometer according to an air impulse-based embodiment. In the accompanying drawings, underlined numbers are used to represent the item at the location of the number or an item adjacent to that number. Ununderlined numbers are associated with items identified by lines extending from the number. When a number is written without an underline and accompanied by an arrow, the number is used to identify the general item indicated by the arrow. [Modes for carrying out the invention]

[0012] The following detailed description illustrates embodiments of the disclosure and methods by which they may be implemented. While several forms for implementing the disclosure have been disclosed, those skilled in the art will recognize that other forms for implementing the disclosure are also possible.

[0013] In one aspect, embodiments of the present disclosure provide a tonometer for determining the characteristics of the eye. This tonometer is An execution unit equipped with an impact mechanism configured to deliver an impact to the cornea of ​​the eye during use; • At least one measuring unit; • With the first confocal chromatic sensor; The execution unit, the measurement unit, and the controller connected to the first confocal color difference sensor; Equipped with, The aforementioned controller, during use, The execution unit is used to apply an impact to the cornea of ​​the eye using the aforementioned impact means. • Using the at least one measuring unit to determine the intraocular pressure value of the eye, The first confocal chromatic sensor is used to measure the corneal thickness of the eye. It is configured in this way.

[0014] The term "in use" refers to using the tonometer. That is, while the tonometer is in use, an impact is applied to the cornea of the eye, and when the tonometer is used to determine the characteristics of the eye, the controller uses an execution unit, at least one measurement unit, and a first confocal sensor.

[0015] According to another aspect, an embodiment of the present disclosure provides a method for measuring the characteristics of an eye. This method includes a) applying an impact to the cornea of the eye using an execution unit including impact means configured to apply an impact to the cornea of the eye during use, the execution unit being provided in the tonometer; b) measuring the intraocular pressure value of the eye using at least one measurement unit provided in the tonometer; c) measuring the corneal thickness value of the eye using at least one confocal chromatic sensor provided in the tonometer; and includes.

[0016] This disclosure provides a tonometer for determining the properties of an eye and a method for determining the properties of an eye. One of the properties that can be determined or measured using the tonometer is intraocular pressure (IOP). Another property that can be determined or measured with the disclosed tonometer is corneal thickness. The confocal chromatic sensor of the tonometer enables accurate and simultaneous determination of IOP and / or corneal thickness. Conveniently, the corneal thickness of an eyeball can be used to correct the IOP of that eyeball, which is derived from measurements by at least one measuring unit. Even more conveniently, the tonometer of this disclosure can measure the distance between the anterior part of the tonometer and the eye, and this distance is used for accurate positioning of the tonometer relative to the eye, enabling efficient examination of the eye. This distance measurement can be used to automatically start a measurement cycle or to instruct the user to start a measurement cycle. Even more conveniently, the tonometer of this disclosure is compact in size, capable of measuring two different properties of the eye (IOP and corneal thickness) with the same device, and is easy to operate. Furthermore, the method for measuring the properties of the eye is easily implementable. To obtain an effective correction factor for intraocular pressure (IOP), it is desirable to measure corneal thickness and IOP at short time intervals from each other. For example, it is desirable to measure at short time intervals such as 0.1 seconds, 0.2 seconds, 0.3 seconds, 0.4 seconds, 0.5 seconds, 0.6 seconds, 0.7 seconds, 0.8 seconds, 0.9 seconds, 1 second, 5 seconds, 10 seconds, 30 seconds, and 1 minute.

[0017] As used herein, the term “execution unit” refers to a configuration used to apply force to the cornea of ​​the eye. As used herein, the term “impact means” refers to means used to impart impact to a surface. The impact means is configured as part of the execution unit. For example, the impact means is used to impart impact to the surface of the eyeball. The impact means may be, for example, a probe fired towards the eye by the execution unit. Alternatively, the impact means may be an air impulse, i.e., a relatively short-duration flow of air towards the eye. The impact means is configured to produce impact, preferably on the cornea of ​​the eye, without impacting the entire eye or the surrounding tissues of the eye.

[0018] As used herein, the term “measurement unit” refers to a component used to measure intraocular pressure (IOP). The measurement unit may measure (or determine) IOP by measuring physical phenomena, or it may derive a measurement result or value using those measurement results. For example, the velocity profile of an impact device (a probe as an impact device) can be measured by the measurement unit. This velocity profile can be used to determine IOP. For example, a fast rebound of the impact device may indicate a higher IOP than a slow rebound. Another example is measuring the frequency of free vibrations in the cornea after impact. The corneal vibration frequency is an indicator of the corneal IOP value. In fact, a nearly direct correlation has been observed between frequency and IOP. For example, at a frequency of 250 Hz, the IOP value is 10 mmHg. IOP increases linearly with frequency, with a frequency of 360 Hz corresponding to an IOP value of 40 mmHg. A frequency of 300 Hz corresponds to an IOP value of approximately 20 mmHg. This correlation can be used, for example, to calculate intraocular pressure values ​​after measuring vibration frequencies using mathematical formulas or lookup tables.

[0019] Intraocular pressure (IOP) refers to the fluid pressure within the eyeball. In some embodiments, the measuring unit may apply various mathematical models, such as regression analysis and curve fitting, to the raw data to obtain the most accurate and reliable measurements of IOP values. In some embodiments, the measuring unit may perform other functions such as error correction, data storage, and data analysis. In particular, IOP values ​​of the eye are measured to maintain the overall health and function of the eye. In some embodiments, the eyeball exhibits a mass-spring system, and the IOP value represents the spring constant. In some cases, the cornea, when displaced from its natural position by an external force, vibrates as a damped harmonic oscillator at a frequency related to intraocular pressure. Since intraocular pressure modulates the stiffness of the eyeball and cornea, the vibration frequency increases with increasing intraocular pressure. It can be understood that measuring intraocular pressure values ​​enables the diagnosis and treatment of ocular hypertension, which can lead to glaucoma. In particular, high IOP values ​​suggest increased stiffness of the eyeball, and consequently, an increase in the resonant frequency of the cornea.

[0020] In some embodiments, the impact means may be partially positioned within the hollow space of the loop of the measuring unit. (The loop is configured in a coil shape that at least partially encloses the impact means.) In this example, the impact means includes a magnetic part such as an elongated magnetic material. In this case, the impact means can move within the loop of the measuring unit. Furthermore, the movement of the impact means within the measuring unit generates an induced voltage in the measuring unit. This induced voltage indicates the velocity of the impact means. By determining the velocity profile, it becomes possible to determine (measure) the intraocular pressure value.

[0021] As described above, the impact means may be implemented as a probe. In some embodiments, the impact means is an elongated magnetic probe. The elongated magnetic probe may be partially located within the execution unit. The elongated magnetic probe has two ends located opposite each other, namely a first end and a second end. The second end is located within the execution unit, and the first end is positioned to protrude outward from an opening in the execution unit. The elongated magnetic probe also has an intermediate portion between the first and second ends. In some embodiments, the first end of the elongated magnetic probe is made of a biocompatible material and impacts the surface of the object (such as the cornea of ​​the eye) during use. The fact that the first portion is made of a biocompatible material is beneficial, as it allows the probe to function in direct contact with the biological tissue of the eyeball, minimizing discomfort and pain, for example. It should be noted that biocompatible materials are non-carcinogenic, non-toxic, and corrosion-resistant. In some embodiments, the execution unit has a group of electrically controllable loops (coils arranged to at least partially surround the elongated magnetic probe). When an electric current is applied to the loop, a magnetic force is generated, which ejects the impact device towards the target (the cornea of ​​the eye).

[0022] In some embodiments, the impact means is an air impulse having a predetermined duration and predetermined force. The air impulse can be generated, for example, by a pressurized vessel equipped with a valve-controlled nozzle. The nozzle is directed towards the eye, and when the valve is open for a first period, air flows from the pressurized vessel through the nozzle towards the eye. The movement of the air generates a first force proportional to the ambient pressure and the pressure difference in the pressurized vessel, the size of the nozzle, and the distance between the nozzle and the eye. By keeping the valve open for the first period, the air impulse is thus generated. After the first period, the air impulse stops. According to this embodiment, the first force of the air impulse is stopped with a decay time shorter than the period of free vibration of the cornea. This ensures that the force acting on the surface of the eyeball stops sufficiently quickly. When the air impulse force stops, the eyeball begins to vibrate. It is desirable that the stopping decay is faster than the period of free corneal vibration. Since the typical vibration frequency is 100Hz to 500Hz, it is desirable that the air impulse be stopped within 1 / 500Hz = 2 milliseconds from maximum force to zero level (for example, by closing the valve system). As an alternative implementation method for the air impulse, the use of a piston mechanism can be considered.

[0023] As used herein, a “confocal chromatic sensor” (CCS) refers to an instrument that operates by focusing a broadband wavelength (usually white light) light beam onto a target surface (such as the eye) using a high-dispersion objective lens. In some embodiments, the light beam is directed perpendicular to the cornea. Advantageously, confocal chromatic sensors have the ability to tolerate large inclinations (including tens of degrees) of the beam axis relative to the normal direction of the surface being measured. Confocal chromatic sensors can be used to measure the central corneal thickness (CCT) of the eyeball. When in use, the light source of the CCS emits a (white) light beam toward the cornea. A lens system is placed in the optical path between the light source and the cornea. This lens system disperses the light so that different wavelengths of light have different focal points. When the dispersed light is reflected from the cornea, the spectrum of the reflected light is measured. Within this spectrum, multiple peak intensity values ​​corresponding to different wavelengths of light can be observed. For example, the first peak may be associated with the first wavelength, and the second peak with the second wavelength. The difference between the first and second wavelengths corresponds to a specific thickness value (depending on the geometric structure and optical properties of the lens system), allowing for thickness measurement. CCS can be used to measure corneal thickness. Corneal thickness can be measured from any visible region of the eye surface. When measured from the "center" of the cornea, the value is also called the central corneal thickness (CCT) value.

[0024] Confocal chromatic sensors can also be used for displacement measurement. Displacement refers to the change in distance from the sensor to the object (e.g., from the CCS to the corneal surface). Displacement measurement resolution in the order of tens of nanometers can be obtained. Measurement frequencies in the order of tens of kilohertz (kHz) can also be obtained. Time-series measurement of displacement values ​​can be used to determine the frequency of vibrations on the cornea. In some embodiments, the confocal chromatic sensor uses infrared (IR) as the measurement beam. Advantageously, infrared light is invisible to the patient's eye. This reduces the urge for the subject to blink during the initial stage of setting the appropriate relative position between the tonometer and the eye, and during measurement.

[0025] In some embodiments, the confocal chromatic sensor is operable to measure the distance between the cornea and the tonometer in order to provide positional information of the tonometer relative to the eye. In some embodiments, the confocal chromatic sensor is used to measure the distance between itself and the eye in the range of several millimeters to tens of millimeters. In some embodiments, the positional information is provided by either visual or acoustic feedback. For example, the measured distance between the tonometer and the cornea is displayed on the device screen. In some embodiments, the visual feedback is expressed in the form of text or graphic information. In the case of a handheld tonometer, the tonometer position can be manually optimized. In some embodiments, the measured distance is used as a feedback signal for an automatic position control system, where the relative position of the tonometer to the eye is optimized using at least one actuator, which is controlled using the measured distance as a feedback signal. Preferably, visual or acoustic feedback is used to assist in the correct positioning of the tonometer relative to the eye. Furthermore, in some embodiments, the positional information can be used to automatically initiate a measurement cycle.

[0026] The term "controller" refers to a computer device capable of operating to control the overall operation of the tonometer. During operation, the controller performs tasks using the execution unit, measurement unit, and at least one confocal chromatic sensor, and responds to and processes information. For example, the controller may be an embedded microcontroller, microprocessor, etc. The controller is connected to the execution unit, measurement unit, and at least one confocal chromatic sensor. The controller may be implemented as an internal component of the tonometer, as an external component of the tonometer, or as a combination of these.

[0027] In some embodiments, the at least one measurement unit is a first confocal chromatic sensor or a second confocal chromatic sensor. Furthermore, the controller may be configured to measure intraocular pressure (IOP) values ​​using the first and / or second confocal chromatic sensors. This measurement is performed by configuring the first or second confocal chromatic sensor to measure the vibration frequency of free vibrations of the cornea caused by impact (by an impact means), and determining the IOP value using the measured vibration frequency. In this regard, the measurement unit comprises a first or second confocal chromatic sensor. The confocal chromatic sensor is positioned appropriately to accurately identify corneal vibrations. Advantageously, the confocal chromatic sensor is customized to identify corneal vibration frequencies and calculate IOP values ​​as a function of corneal vibration frequencies. The confocal chromatic displacement sensor is capable of performing thousands of observations per second with a resolution of tens of nanometers, thereby precisely measuring the vibration amplitude at at least one point on the cornea, and using these observations to calculate the vibration frequency. In some embodiments, the vibration amplitude of at least one point on the cornea is used to determine the corneal resonant frequency. The corneal resonant frequency is typically in the range of 100 to 500 Hz. A technical advantage of using a first confocal chromatic displacement sensor in the measurement unit is that the same sensor used for measuring corneal thickness can also be used for determining intraocular pressure values ​​by vibration frequency measurement. An advantage of providing a second confocal chromatic sensor is that this method allows the second confocal chromatic sensor to be adjusted (or configured) to output intraocular pressure values ​​instead of thickness values, thus simplifying the design. As mentioned above, the thickness value can be the thickness of any part of the cornea, but it may also be, for example, the central corneal thickness.

[0028] In some embodiments, the at least one measuring unit is a velocity measuring unit that measures the velocity profile of the impact means during impact. The controller is configured to determine the intraocular pressure (IOP) value using the measured velocity profile. The velocity profile (e.g., velocity against time = acceleration) can be used to determine the IOP using a lookup table or other predetermined formula. In this example, the tonometer can be considered a rebound tonometer. The tonometer provides an accurate determination of the IOP value. Integrating the velocity measuring unit into the tonometer improves the accuracy and precision of IOP measurement. Furthermore, measuring the velocity profile of the impact means during interaction with the cornea provides the tonometer with valuable dynamic data, which is cleverly utilized by the controller to refine the IOP calculation using a lookup table or predetermined formula. In some embodiments, the tonometer is a rebound tonometer.

[0029] In particular, corneal thickness is used as an important parameter when accurately measuring intraocular pressure (IOP) values. It is clear that corneal thickness is not uniform throughout the cornea, but varies depending on the location, in both healthy and diseased corneas, and is thought to affect the accuracy of IOP measurement. CCS is used to measure corneal thickness, which varies from central corneal thickness. An advantage is that by integrating corneal thickness measurement into the same device as IOP measurement using impact-based means, it is ensured that corneal thickness is measured at the same location where the impact means acted on the cornea, thereby correcting IOP measurement results with accurate corneal thickness measurements. The controller acquires this velocity profile and cleverly utilizes it when determining IOP values.

[0030] Furthermore, by incorporating velocity profiles into intraocular pressure (IOP) calculations, the tonometer can more precisely understand the eye's response to impact. This not only improves the accuracy of IOP measurement but also provides additional insights into the biomechanical properties of the eye during impact. Moreover, measuring the velocity profile of the impact device during its interaction with the cornea provides the tonometer with valuable dynamic data, which is cleverly utilized by the controller to refine IOP calculations using lookup tables and predetermined formulas.

[0031] Furthermore, in some embodiments, if the impact means is an air impulse having a first duration and a first force, the measurement unit is a functional combination of a controller and a first confocal chromatic sensor, or a controller and a second confocal chromatic sensor. That is, the controller can receive information from either a first confocal chromatic sensor (CCS) (the same one used for thickness measurement) or a second confocal chromatic sensor (dedicated to vibration measurement). The controller uses this information (essentially the distance from the first or second sensor) to measure the vibration frequency of the free vibration of the cornea caused by the impact, and determines the intraocular pressure value from that vibration frequency. The term "functional combination" means that the data from the CCS is processed by the controller, and therefore the CCS and controller function together as a measurement means. In a preferred embodiment, only the first CCS is present; that is, the first CCS is used for both thickness measurement and vibration measurement. In some embodiments, this tonometer is an air impulse tonometer. The advantage of the air impulse type is that no physical object comes into contact with the eyeball during the measurement cycle. Furthermore, in some embodiments, the measurement of the vibration frequency of corneal free vibration is initiated after a first time interval. The technical advantage of this is that the vibration measurement (i.e., intraocular pressure measurement) can be precisely timed to begin when the valve of the air nozzle closes.

[0032] In some embodiments, when the initial force of the air impulse stops, its decay should be rapid, preferably significantly shorter than the period of free corneal vibration. This allows the eye to vibrate freely because the air impulse itself does not interfere with the measurement and there is no initial force from the airflow. In some embodiments, the controller is configured to correct the measured intraocular pressure (IOP) value using the measured corneal thickness (or central corneal thickness). Corneal thickness is an important factor in determining the IOP value of the eye. For example, if the cornea is thick, the IOP value may be overestimated, and if the cornea is thin, the IOP value may be underestimated. Therefore, the IOP value is corrected based on the corneal thickness of the eyeball or the central corneal thickness.

[0033] For example, when measuring intraocular pressure using the principle of a rebound tonometer, the measurement may be underestimated if the corneal thickness is thinner than normal. Conversely, the measurement may be overestimated if the corneal thickness is thicker than normal.

[0034] For example, when measuring central corneal thickness, the values ​​in Table 1 (below) can be used as a basis for correction calculations. For instance, if the thickness is 485 micrometers, the intraocular pressure value is corrected by adding 3 mmHg. If the measurement point is not at the center, the values ​​in the table need to be modified. This table can be used as a lookup table, and it is also possible to derive correction values ​​as a function of corneal thickness from these values. The technical benefit of this is that it enables more accurate measurement of intraocular pressure. [Table 1]

[0035] As another example, the central corneal thickness is correlated with the corneal resonant frequency. As mentioned earlier, the corneal resonant frequency is related to intraocular pressure (IOP). Therefore, by correcting the relationship between the resonant frequency and IOP using the corneal thickness value at the center, the IOP can be accurately determined. Table 1 can be used for this correction. A similar correction table can be created for corneal thickness values ​​measured from areas other than the center.

[0036] Confocal chromatic sensors have the ability to simultaneously measure the positions of the outer and inner surfaces of the cornea, thereby measuring the corneal thickness of the eye. In some embodiments, the confocal chromatic sensor simultaneously measures the positions of the outer and inner surfaces of the cornea while the cornea is vibrating. Corneal thickness characterizes corneal stiffness and is an interfering factor in intraocular pressure (IOP) measurement. When corneal thickness is measured, this value can be used to apply a correction when calculating IOP. This improves the accuracy of IOP calculation. In some embodiments, regression analysis is used to determine the correction coefficient for IOP. The technical advantage of this is that IOP can be precisely corrected by taking into account the corneal thickness of the eye.

[0037] In some embodiments, at least one measuring unit is configured to measure intraocular pressure (IOP) during a first time period (dt). The first time period begins at a first time point (t1) and lasts until a second time point (t2). The first time point (t1) is the point in time when the impact means strikes (impacts) the cornea. This impact causes the cornea to vibrate. The vibration decays over time and is substantially absent by the second time point. In other words, the total duration of the first time period is preferably greater than or equal to the duration of the vibration. Furthermore, the first confocal chromatic sensor is configured to measure the corneal thickness of the eye at the second time point (t2). In this regard, the difference between the first time point (t1) and the second time point (t2) is in the range of 0.1 to 3 seconds (e.g., 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 seconds, or up to 4.0 seconds).

[0038] In some embodiments, intraocular pressure (IOP) and corneal thickness can be measured at different time points, and the IOP measured during the first time period (between t1 and t2) can be corrected based on the corneal thickness measured at the second time point (t2). As a first example, IOP is measured in the first 0.1 seconds after the impact of the impact device (i.e., 0.1 seconds after t1), and the corneal thickness is measured 2.1 seconds after the IOP measurement. The technical advantage of measuring IOP during the first time period (dt) and measuring the corneal thickness of the eyeball at least at the second time point (t2) is that the IOP can be easily and / or accurately corrected based on the corneal thickness of the eyeball. Alternatively, the corneal thickness can be measured before the first time period.

[0039] In some embodiments, the first time period is the time difference (dt) between a first time point (t1) and a second time point (t2). The duration of the first time period may be determined based on the measured corneal thickness value and / or the measured intraocular pressure value. In this case, the length of the first time period (dt) is a function of at least one of the measured corneal thickness value and / or the measured intraocular pressure value. In some embodiments, the length of the first time period (dt) may be determined based on the measured corneal thickness value. Thickness can affect the damping time constant related to corneal vibration. When the thickness is thin, the rate at which vibrations dampen may be faster compared to when the thickness is thick. This is because there is a difference in the elastic properties of the eye between small and large thickness values. In other embodiments, the duration of the first time period (dt) may be determined based on the measured intraocular pressure value. In some embodiments, the duration of the first time period (dt) is calculated to ensure accurate correction of the intraocular pressure measurement based on the corneal thickness value. The technical effect of determining the duration of the first time period is that it enables accurate measurement of corneal thickness and / or intraocular pressure values ​​within a predetermined time interval, and further enables accurate correction of the intraocular pressure value based on the corneal thickness value. In fact, with this configuration, corneal thickness measurement is performed using a confocal chromatic sensor when the eye surface is not vibrating. This improves measurement accuracy. One example of determining the duration of the first time period is to measure the duration of vibration caused by impact. Specifically, a confocal chromatic sensor is used to measure the vibration amplitude over time after impact. When the amplitude becomes negligibly small, that point in time can be used as the second time point (t2). A further technical effect of determining the length of the first period is that the next measurement cycle (using an impact means) is not started before the vibration has subsided. This eliminates the possibility of problems due to interference between the previous and next measurements.

[0040] Depending on the embodiment, the first time point (t1) may be either before or after the second time point (t2). The intraocular pressure value is measured either before or after the corneal thickness value. It is also possible to measure the intraocular pressure value and the corneal thickness value at the same moment. The technical effect of determining the time difference between the first time point (t1) and the second time point (t2) (i.e., the length of the first period) is to enable accurate measurement of the corneal thickness value and / or intraocular pressure value of the eye within a predetermined time interval, and further enable accurate correction of the intraocular pressure value based on the corneal thickness value.

[0041] Depending on the embodiment, the controller is configured to repeat the following measurements. • Measurement of intraocular pressure using at least one measurement unit during a second time period between the third time point (t3) and the fourth time point (t4). • Measurement of corneal thickness using the first confocal chromatic sensor at at least the fourth time point (t4).

[0042] In this regard, intraocular pressure and corneal thickness are measured again during a second time period (i.e., between the third time point (t3) and the fourth time point (t4)). Depending on the embodiment, the time difference between the third time point (t3) and the fourth time point (t4) is within 0.1 seconds. The third time point (t3) and the fourth time point (t4) occur after the first time point (t1) and the second time point (t2). Referring to the first example, the intraocular pressure may be measured at 5 seconds and the corneal thickness may be measured at 7 seconds.

[0043] In some embodiments, the controller is further configured to repeat the determination (or measurement) of intraocular pressure (IOP) values ​​using at least one measurement unit and the determination (or measurement) of corneal thickness values ​​using a first confocal chromatic sensor until the corrected IOP values ​​fall within a predetermined tolerance range. In other words, the IOP and corneal thickness values ​​of an eye are measured and corrected at different time points. The measurements continue until the corrected IOP values ​​at different time points fall within a predetermined tolerance range. Referring to the first example, the IOP value measured at t1 may be corrected based on the corneal thickness value measured at t2. Similarly, the IOP value measured at t3 may be corrected based on the corneal thickness value measured at t4, and so on. In this example, if the IOP value at t1 is similar to the IOP value at t3 (e.g., within ±5%), the IOP values ​​obtained at t1 and t3 can be considered as the IOP values ​​of the eyeball being measured. In this example, if the intraocular pressure (IOP) value at time t1 differs from the IOP value at time t3 (the difference is 5% or more), the IOP measurement is continued at t5, and the corneal thickness measurement is continued at t6. Advantageously, repeating the measurement of IOP and corneal thickness significantly improves the accuracy and precision of the IOP measurement. The predetermined tolerance can be, for example, 1.0 mmHg, meaning that the measurement cycle can be stopped if the deviation of the measured value is less than the predetermined tolerance.

[0044] In some embodiments, the tonometer is a rebound tonometer. In this respect, the term “rebound tonometer” refers to a device used to measure the properties of an object. In a rebound tonometer, intraocular pressure is measured by measuring the velocity profile of an impact means applied to the cornea of ​​the eye and rebounding, using at least one measuring unit.

[0045] This disclosure also relates to the method described above. The various embodiments and modifications disclosed above with respect to the first approach described above are applicable mutatis mutandis to this method.

[0046] Depending on the embodiment, the measured intraocular pressure value can be corrected using the measured corneal thickness value.

[0047] In some embodiments, intraocular pressure is measured during a first time period. The corneal thickness of the eyeball is measured at least at the second time point (t2).

[0048] In some embodiments, the first time period is the time difference (dt) between a first time point (t1) and a second time point (t2), and is determined based on at least one selected from either corneal thickness values ​​or intraocular pressure values.

[0049] Depending on the embodiment, the method further includes repeating steps (a) and (b) until a corrected intraocular pressure value within a predetermined tolerance range is obtained.

[0050] Depending on the embodiment, the first time point is either before or after the second time point (t2).

[0051] In some embodiments, the measurement of the vibration frequency is started after a first time period has elapsed, i.e., after the air impulse has stopped (for example, within 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, or 5 milliseconds after it has stopped).

[0052] In summary, a tonometer for measuring ocular properties is presented. The properties to be measured (by direct or indirect measurement) are intraocular pressure and central corneal thickness. The tonometer comprises an execution unit used to fire an impact means toward the cornea of ​​the eye. The impact means may be, for example, a probe. At least one measuring unit is used to measure intraocular pressure. For example, if the impact means is a probe, the measuring unit measures the velocity profile of the probe during impact. This velocity profile can be used to determine the intraocular pressure. The tonometer further comprises a first confocal chromatic sensor. The confocal chromatic sensor is used to measure (or determine) the corneal thickness value of the eye. The execution unit, measuring unit, and confocal chromatic sensor are all controlled (or used) by a controller. The presented configuration provides a reliable and accurate tonometer for determining the aforementioned properties.

[0053] In other embodiments, the impact means is an air impulse. In this embodiment, the measurement unit is a functional combination of a controller and a first confocal chromatic sensor. This combination is configured to measure vibrations and derive intraocular pressure from them. The pressure measurement is corrected using corneal thickness measurement by the first confocal chromatic sensor. Alternatively, the functional combination may consist of a controller and a second confocal chromatic sensor. The advantage of having two different confocal chromatic sensors is that the first sensor can be adjusted for thickness measurement (sub-micrometer accuracy) and the other for corneal motion measurement (micrometer accuracy).

[0054] Combining a rebound tonometer with a CCS pachymeter to correct intraocular pressure (IOP) values ​​using corneal thickness offers several technical advantages. Firstly, corneal thickness is not uniform. In both healthy and diseased corneas, corneal thickness varies depending on the location, and this is thought to affect the accuracy of IOP measurement. Typically, applanation tonometers correct IOP measurements using central corneal thickness (CCT) values. With rebound tonometers, the measurement (i.e., the impact of the probe) does not always hit the center of the cornea. In these areas, CCS can be used to measure corneal thickness different from that of central corneal thickness (CCT). Especially in cases of astigmatism, corneal thickness can vary significantly at different locations. Since CCS can be set to measure thickness at the point of impact, this method allows us to understand the impact of thickness on the measurement results.

[0055] Furthermore, corneal thickness changes rapidly. The use of anesthetic eye drops alters corneal thickness in a short period. In patients with corneal damage, these eye drops are frequently needed because measuring rebound intraocular pressure without anesthesia is painful. Intraocular pressure itself can alter corneal thickness; at high intraocular pressure, the cornea stretches and narrows compared to at low intraocular pressure. This change can occur within minutes. For example, intraocular pressure can fluctuate by up to 5 mmHg between standing / walking and sitting / resting. Also, activities that tense the shoulders can increase intraocular pressure by up to 5 mmHg.

[0056] Furthermore, the supine position affects central corneal thickness (CCT). In other words, if corneal thickness is unknown, central corneal thickness can change rapidly, potentially leading to errors in intraocular pressure measurements.

[0057] Furthermore, corneal thickness shows gradual changes. Normal use of therapeutic contact lenses and misuse of conventional contact lenses are known to cause corneal edema, i.e., alter corneal thickness. Rapid myopia progression in children can alter corneal thickness within a few months. Rapidly progressive keratoconus can also alter corneal thickness within a few months.

[0058] For the reasons stated above, it is important to measure corneal thickness simultaneously with intraocular pressure measurement. (See detailed diagram)

[0059] Referring to Figure 1, a schematic diagram of a tonometer 100 for measuring (or determining) the characteristics of an eye 110 according to one embodiment of the present disclosure is shown. The tonometer 100 comprises an execution unit 120 equipped with an impact means 130 for applying impact to the cornea 112 of the eye 110, at least one measurement unit (indicated, for example, as a measurement unit 140), at least one confocal chromatic sensor (indicated, for example, as a confocal chromatic sensor 150), and a controller 160. The controller 160 is connected to the execution unit 120, the measurement unit 140, and the confocal chromatic sensor 150.

[0060] In one example, the impact means 130 is a probe comprising an elongated magnetic body 134 and a tip 132 connected to the first end of the magnetic body 134. During use, the controller 160 supplies electricity through a series of electrical loops 142, which generates a magnetic force on the elongated magnetic body 134. This magnetic force propels the impact means 130 toward the cornea 112 of the eye 110. The tip 132 of the probe contacts the cornea 112 of the eye at a first time point (t1), bounces back, and returns to the inside of the tonometer. During this movement, the elongated magnetic body 134 of the impact means 130 (probe) induces an electric current in the measuring unit 140.

[0061] In this embodiment, the measuring unit 140 is a measuring coil, positioned to at least partially surround the elongated magnetic body 134 of the impact means 130. This induced current is a function of the velocity of the impact means 130 during impact (and before and after impact). The velocity of the impact means can be used to determine intraocular pressure. In fact, a high rate of change of velocity of the impact means (dv / dt (time derivative of velocity)) suggests higher intraocular pressure (harder eyeball) than a low rate of change of velocity. This determination can be made, for example, by using a lookup table that associates velocity changes with intraocular pressure (IOP) values, or by using an equation in which IOP is a function of (dv / dt). This makes it possible to determine (measure) the intraocular pressure of the eye.

[0062] The impact device vibrates the cornea 112 during a first period (t1 to t2). After the vibration stops (or nearly stops), the central thickness of the cornea 112 is measured using a confocal chromatic sensor 150. The central thickness value of the cornea can be used to correct (calibrate, adjust) the measured intraocular pressure value, for example, using a lookup table or correlation formula.

[0063] Figure 1 is for illustrative purposes only and should not unduly limit the scope of the claims of this application. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of the embodiments of this disclosure.

[0064] Figure 2 is a block diagram of a tonometer 200 for measuring the characteristics of the eye according to one embodiment of the present disclosure. The tonometer 200 includes at least one confocal chromatic sensor (for example, shown as confocal chromatic sensor 204) provided in a measuring unit 202, and a controller 206 configured to measure intraocular pressure values ​​using the confocal chromatic sensor 204.

[0065] Figure 2 is for illustrative purposes only and should not unduly limit the scope of the claims of this application. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of the embodiments of this disclosure.

[0066] Referring to Figure 3, a graph representing corneal vibration over time is shown according to an embodiment of the present disclosure. Corneal vibration is represented on the Y-axis, and time on the X-axis. Corneal vibration is depicted as damped vibration at a first time point (t1), a second time point (t2), a third time point (t3), and a fourth time point (t4). The vibration begins when the impact means strikes the cornea of ​​the eye (as described above). The cornea vibrates at the vibration frequency of the corneal free vibration during the first period (the period from t1 to t2, or from t3 to t4). The vibration dampens, and the corneal thickness value becomes measurable at the second or fourth time point. In one embodiment, the measurement is performed during the measurement period between the second time point (t2) and the third time point (t3). Depending on the configuration, the measurement unit may be a first confocal sensor. In this case, the measurement unit measures the vibration, determines the vibration frequency, and calculates the measured intraocular pressure value based on it. In an alternative configuration, the measuring unit is part of a rebound tonometer; that is, it measures the velocity of the impact device and uses it as an indirect measure of intraocular pressure, as described above. The vibration frequency can be measured with the confocal chromatic sensor 150 shown in Figure 1. This vibration frequency can then be used to determine the intraocular pressure using a lookup table or equation.

[0067] Figure 3 is for illustrative purposes only and should not unduly limit the scope of the claims of this application. Those skilled in the art will be able to recognize many variations, alternatives, and modifications of the embodiments of this disclosure.

[0068] Figure 4 shows a flowchart illustrating the steps of a method for measuring eye characteristics according to one embodiment of the present disclosure. In step 402, the cornea of ​​the eye is struck using an execution unit provided in a tonometer, which includes an execution unit configured to strike the cornea of ​​the eye when in use. In step 404, the intraocular pressure is measured using at least one measuring unit provided in the tonometer. In step 406, the corneal thickness of the eyeball is measured using at least one confocal chromatic sensor provided in the tonometer. A velocity profile is measured during the impact, and the measured velocity profile is used to determine the intraocular pressure.

[0069] Figure 5 illustrates a tonometer 500 in which the impact means is an air impulse 524. A magnified view of a typical pulse shape is shown in 524E. The air impulses 524, 524E have a first force (shown in the figure as height in the y-axis direction) and a first duration 522. The air impulse is generated by opening a valve 530 between the nozzle 520 and the pressure chamber 526 using a control signal from the controller 528. Air is released from the opening 512 of the nozzle 520 toward the eyeball 510. A first confocal chromatic sensor 550 measures the vibration caused by the air impulse together with the central corneal thickness. The measuring unit is a functional combination of the controller 528 and the confocal chromatic sensor 550, which measures the displacement (i.e. vibration) caused by the air impulse. A magnified view of the air impulse 524E shows the decay time 523 after the valve 530 is closed. The decay time 523 is in the range of 2 milliseconds, i.e., shorter than a single period of oscillation. This ensures free oscillation undisturbed by air impulses. In the example shown in the figure, air impulses 524 and 524E are flying from the tonometer 500 toward the eyeball 510 in the direction indicated by the arrows. The right edge of the air impulses first strikes the surface of the eyeball (524 and 524E), followed by the first force acting. The end of the air impulse with decay time 523 is shown as the left edge of the air impulse. The first force may be constant or variable. For example, it may start at a low value and then increase.

[0070] The steps described above are merely illustrative, and alternative steps may also be included. That is, one or more steps may be added, one or more steps may be omitted, or one or more steps may be performed in a different order without departing from the scope of the attached claims.

[0071] It is possible to modify the embodiments of this disclosure described above 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 preclude the existence of multiple such elements.

Claims

1. A tonometer that determines the characteristics of the eye, An execution unit equipped with an impact mechanism configured to deliver an impact to the cornea of ​​the eye during use; • At least one measuring unit; • With the first confocal chromatic sensor; - The execution unit, the measurement unit, and the controller connected to the first confocal chromatic sensor; The controller is equipped with, - Using the aforementioned impact means, the execution unit is used to apply an impact to the cornea of ​​the eye. - Using the at least one measuring unit to determine the intraocular pressure value of the eye, - The first confocal chromatic sensor is used to measure the corneal thickness of the eye. A tonometer configured in such a way.

2. The tonometer according to claim 1, wherein the at least one measuring unit is a velocity measuring unit that measures the velocity profile of the impact means during impact, and the controller is configured to determine an intraocular pressure value using the measured velocity profile.

3. The tonometer according to claim 1, wherein the impact means is an air impulse having a first duration and a first force, the measurement unit is a functional combination of a controller and a first confocal chromatic sensor, or a controller and a second confocal chromatic sensor, and the controller is configured to use the first confocal chromatic sensor or the second confocal chromatic sensor to measure the vibration frequency of the free vibration of the cornea caused by the impact, and to determine an intraocular pressure value from the vibration frequency.

4. The tonometer according to claim 1 or 2, wherein the controller is configured to use the first confocal chromatic sensor or the second confocal chromatic sensor to measure the vibration frequency of the free vibration of the cornea caused by the impact, and to determine the intraocular pressure value from the vibration frequency.

5. The tonometer according to any of the preceding claims, wherein the controller is configured to correct the intraocular pressure value measured using the measured corneal thickness value.

6. The tonometer according to any of the preceding claims, wherein the at least one measuring unit is configured to measure an intraocular pressure value during a first time period, and the first confocal chromatic sensor is configured to measure an ocular corneal thickness value at a second time point.

7. The tonometer according to claim 6, wherein the first time period is the time between the first time point and the second time point, and is determined based on the measured corneal thickness value and / or measured intraocular pressure value.

8. The tonometer according to claim 6 or 7, wherein the first time point is before or after the second time point.

9. - Measurement of intraocular pressure values ​​using at least one of the measurement units during a second time period between the third and fourth time points; - Measurement of corneal thickness using the first confocal chromatic sensor at least the fourth time point; A tonometer according to any one of claims 6 to 8, configured to repeat the process.

10. The tonometer according to any of the preceding claims, wherein the controller is further configured to repeat the determination of an intraocular pressure value using the at least one measurement unit and the determination of a corneal thickness value using the first confocal chromatic sensor or the second confocal chromatic sensor until the corrected intraocular pressure value falls within a predetermined tolerance range.

11. A rebound-type tonometer, as described in any one of claims 1, 2, 4, 5, 6, 7, 8, 9, or 10.

12. A tonometer according to any one of claims 1, 3, 4, 5, 6, 7, 8, 9, or 10, which is an air impulse type tonometer.

13. The tonometer according to any one of claims 3 to 10 or 12, wherein the measurement of the vibration frequency of the free vibration of the cornea is started after the first time period has elapsed.

14. The tonometer according to any one of claims 3 to 10 or 12 to 13, wherein the first force is stopped with a decay time shorter than the period of free vibration of the cornea.

15. A method for measuring the characteristics of the eye, a) an execution unit including an impact means configured to apply an impact to the cornea of ​​the eye when in use, wherein an execution unit provided in a tonometer is used to apply an impact to the cornea of ​​the eye; b) Measuring the intraocular pressure of the eye using at least one measuring unit provided in the tonometer; c) Measuring the corneal thickness of the eye using at least one confocal chromatic sensor provided in the tonometer; Methods that include...

16. The method according to claim 15, wherein the at least one measuring unit is a velocity measuring unit, the velocity measuring unit is a unit for measuring the velocity profile of the impact means during impact, and the measured velocity profile is used to determine the intraocular pressure value of the eye.

17. The method according to claim 15, wherein the impact means is an air impulse having a first duration and a first force, the at least one measuring unit is a functional combination of a controller and a first confocal chromatic sensor, or a controller and a second confocal chromatic sensor, and the controller is configured to use the first confocal chromatic sensor or the second confocal chromatic sensor to measure the vibration frequency of the free vibration of the cornea caused by the impact, and to determine an intraocular pressure value from the vibration frequency.

18. The method according to any one of claims 15 to 17, wherein the measured intraocular pressure value is corrected using the measured corneal thickness value.

19. The method according to any one of claims 15 to 18, wherein the intraocular pressure value is measured during a first time period, and the corneal thickness value is measured at least at a second time point.

20. The method according to claim 19, wherein the first time period is the time difference between a first time point and a second time point, and is determined based on the corneal thickness value and / or the intraocular pressure value.

21. The method according to any one of claims 15 to 20, comprising repeating steps (a) and (b) until the corrected intraocular pressure value remains within a predetermined tolerance range.

22. The method according to any one of claims 19 to 21, wherein the first time point is before or after the second time point.

23. The method according to any one of claims 15, 16, 18, 19, 20, 21, or 22, wherein the at least one measuring unit is a rebound tonometer.

24. The method according to any one of claims 15, 17, 18, 19, 20, 21, or 22, wherein the at least one measuring unit is an air impulse tonometer.

25. The method according to any one of claims 17 to 22 or 24, wherein the measurement of the vibration frequency of the free vibration of the cornea is started after the first time period has elapsed.

26. The method according to any one of claims 17 to 21 or 24 to 25, wherein the first force of the air impulse is stopped with a decay time shorter than the period of free vibration of the cornea.

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