Ultrasonic tonometer

Abstract

An object of the present application is to provide an ultrasonic tonometer capable of appropriately irradiating ultrasonic waves to an eye to be examined. An ultrasonic tonometer measures intraocular pressure of an eye to be examined using ultrasonic waves, and includes an ultrasonic wave irradiator that irradiates ultrasonic waves to the eye to be examined, and a control unit that applies a signal subjected to amplitude modulation to the ultrasonic wave irradiator. In addition, an ultrasonic tonometer measures intraocular pressure of an eye to be examined using ultrasonic waves, and includes an ultrasonic wave irradiator that has a Langevin vibrator provided with an opening portion and irradiates ultrasonic waves to the eye to be examined, a deformation detection unit that detects a deformation state of the cornea, and a control unit that calculates hysteresis of the cornea based on the deformation state of the cornea acquired by the deformation detection unit.

Description

Technical Field

[0001] This invention relates to an ultrasonic tonometer for measuring intraocular pressure in an eye using ultrasound. Background Technology

[0002] As a non-contact tonometer, the air-jet tonometer remains common. The air-jet tonometer measures the corneal deformation and the air pressure as it is ejected into the cornea, converting the air pressure at the predetermined deformation state into intraocular pressure.

[0003] In addition, as a non-contact tonometer, an ultrasonic tonometer that uses ultrasound to measure intraocular pressure has been proposed (see Patent Document 1). The ultrasonic tonometer in Patent Document 1 converts the radiation pressure under a predetermined deformation state into intraocular pressure by detecting the deformation state of the cornea when ultrasound is radiated to the cornea and the radiation pressure sprayed onto the cornea.

[0004] Patent Document 1: Japanese Patent Application Publication No. 5-253190

[0005] However, the existing devices are not yet capable of properly irradiating the cornea of ​​the examined eye with ultrasound. For example, the device according to Patent Document 1 is not actually capable of applying ultrasound to the examined eye to the degree that causes the cornea to flatten or concave, and is not capable of properly irradiating the examined eye with ultrasound. Summary of the Invention

[0006] The present invention was made in view of the existing problems, and its technical objective is to provide an ultrasonic tonometer capable of appropriately irradiating the examined eye with ultrasound.

[0007] To address the aforementioned issues, the present invention is characterized by having the following structure.

[0008] (1) An ultrasonic tonometer for measuring intraocular pressure of an eye under examination using ultrasound, characterized in that it comprises: an ultrasonic actuator for irradiating the eye under examination with ultrasound; and a control unit for applying an amplitude-modulated signal to the ultrasonic actuator.

[0009] (2) An ultrasonic tonometer for measuring intraocular pressure of an eye under examination using ultrasound, characterized in that it comprises: an ultrasonic actuator having a Langevin-type transducer with an opening and irradiating the eye under examination with ultrasound; a deformation detection unit for detecting the deformation state of the cornea; and a control unit for calculating the hysteresis of the cornea based on the deformation state of the cornea obtained by the deformation detection unit. Attached Figure Description

[0010] Figure 1 This is an image of the appearance of an ultrasonic tonometer.

[0011] Figure 2This is a diagram of the internal structure of an ultrasonic tonometer.

[0012] Figure 3 This is a diagram showing the structure of an ultrasonic actuator.

[0013] Figure 4 This is a diagram showing the structure of an ultrasonic actuator.

[0014] Figure 5 This diagram illustrates the control system of an ultrasonic tonometer.

[0015] Figure 6A This is a diagram representing the signal applied to the ultrasonic actuator.

[0016] Figure 6B This is a diagram representing the signal applied to the ultrasonic actuator.

[0017] Figure 7A It is a graph showing the change of pressure over time based on ultrasound.

[0018] Figure 7B It is a graph showing the change of pressure over time based on ultrasound.

[0019] Figure 8 This is a graph showing the changes in the light signal and acoustic radiation pressure of the deformation detection system over time. Detailed Implementation

[0020] <Implementation Method>

[0021] Hereinafter, embodiments of the present invention will be described. The ultrasonic tonometer of this embodiment (e.g., ultrasonic tonometer 1) uses ultrasound to measure the intraocular pressure of the examined eye. The ultrasonic tonometer includes, for example, an ultrasonic actuator (e.g., ultrasonic actuator 100) and a control unit (e.g., control unit 70). The ultrasonic actuator irradiates the examined eye with ultrasound. The control unit applies an amplitude-modulated signal to the ultrasonic actuator. The ultrasonic tonometer of this embodiment, by having such a structure, can appropriately irradiate the examined eye with ultrasound. For example, by applying a slowly increasing pressure to the examined eye, the examined eye can be reliably deformed.

[0022] In addition, the signal applied to the ultrasonic actuator can be a burst signal. By applying a burst signal, ultrasonic waves can be generated more appropriately.

[0023] Furthermore, the control unit can modulate the signal by gradually increasing the amplitude. This allows the pressure rise generated by the ultrasound to be slowed down. For example, the control unit can modulate the signal using a sine wave as the modulation wave.

[0024] Additionally, the ultrasonic actuator may include a Langevin-type transducer with an opening (e.g., opening 101). For example, the opening may be oriented in a direction parallel to the sound axis (e.g., sound axis Q1) of the ultrasonic wave. Furthermore, the opening may be configured to allow the optical axis (e.g., optical axis O1) of an observation optical system (e.g., frontal imaging system 220) used to observe the examined eye to pass through.

[0025] Furthermore, the ultrasonic tonometer can include a deformation detection unit (e.g., deformation detection system 260) for detecting the deformation state of the cornea. In this case, the control unit can calculate the corneal hysteresis based on the corneal deformation state obtained by the deformation detection unit. The control unit can calculate a more accurate intraocular pressure based on the corneal hysteresis. Additionally, the control unit can correct the intraocular pressure based on the corneal hysteresis. The ultrasonic tonometer utilizes the ultrasonic waves of a Langevin-type oscillator to sufficiently deform the cornea, thereby accurately calculating the corneal hysteresis. Furthermore, the control unit can determine whether the cornea has deformed into a predetermined shape based on the detection results of the deformation detection unit, and calculate the intraocular pressure of the examined eye based on the output information of the ultrasonic actuator when the cornea has deformed into the predetermined shape.

[0026] In addition, the deformation detection unit can detect the deformation state of the cornea optically or acoustically. For example, the deformation detection unit can irradiate the cornea of ​​the eye being examined with measurement light or ultrasound, and detect the deformation state of the cornea by detecting the reflection of the measurement light or ultrasound.

[0027] <Example>

[0028] Hereinafter, embodiments of the present invention will be described. The ultrasonic tonometer of this embodiment, for example, uses ultrasound to non-contactly measure the intraocular pressure of the examined eye. The ultrasonic tonometer measures intraocular pressure by detecting, for example, changes in the shape or vibration of the examined eye when irradiated with ultrasound using optical or acoustic methods. For example, the ultrasonic tonometer continuously irradiates the cornea with pulsed waves or burst waveforms, and calculates the intraocular pressure based on the output information of the ultrasound waves when the cornea deforms into a predetermined shape. The output information includes, for example, the sound pressure level, sound radiation pressure, irradiation time (e.g., elapsed time from the input of the trigger signal), or frequency of the ultrasound waves. Furthermore, when the cornea of ​​the examined eye is deformed, for example, the sound pressure level, sound radiation pressure, or sound flow of the ultrasound waves can be used.

[0029] like Figure 1 As shown, the ultrasonic tonometer 1 includes, for example, a base 2, a measuring section 3, a face support section 4, and a drive section 5. An ultrasonic actuator 100 and an optical unit 200 (described later) are disposed inside the measuring section 3. The face support section 4 supports the face of the eye being examined. The face support section 4 is, for example, disposed on the base 2. The drive section 5 moves the measuring section 3 relative to the base 2, for example, for calibration. An ultrasonic actuator 100 and an optical unit 200 are disposed inside the measuring section 3 (see...). Figure 2 ).

[0030] <Ultrasonic Actuator>

[0031] The ultrasonic actuator 100, for example, irradiates ultrasonic waves into the eye E being examined. For example, the ultrasonic actuator 100 irradiates ultrasonic waves into the cornea, causing acoustic radiation pressure in the cornea. Acoustic radiation pressure is, for example, a force acting in the direction of sound wave propagation. The ultrasonic tonometer 1 of this embodiment, for example, utilizes this acoustic radiation pressure to deform the cornea. Furthermore, the ultrasonic actuator 100 of this embodiment is cylindrical, and the optical axis O1 of the optical unit 200 (described later) is disposed in the central opening 101.

[0032] The ultrasonic actuator 100 in this embodiment is a so-called Langevin-type transducer. For example... Figure 3 As shown, the ultrasonic actuator 100 includes, for example, an ultrasonic element 110, an electrode 120, a mass component 130, and a fastening component 160. The ultrasonic element 110 generates ultrasonic waves. The ultrasonic element 110 can be a voltage element (e.g., piezoelectric ceramic) or a magnetostrictive element. In this embodiment, the ultrasonic element 110 is ring-shaped. For example, the ultrasonic element 110 can be laminated with multiple piezoelectric elements. Figure 4 It is Figure 3 A magnified view of region A1. In this embodiment, as... Figure 4 As shown, the ultrasonic element 110 employs two stacked piezoelectric elements (e.g., piezoelectric element 111 and piezoelectric element 112). For example, the two piezoelectric elements are connected to electrodes 120 (electrode 121 and electrode 122), respectively. In this embodiment, electrodes 121 and electrode 122 are, for example, ring-shaped.

[0033] The mass component 130, for example, clamps the ultrasonic element 110. By clamping the ultrasonic element 110, the mass component 130 enhances the tensile strength of the ultrasonic element 110, enabling it to withstand strong vibrations. This allows the generation of high-output ultrasonic waves. The mass component 130 can be, for example, a metal block. For example, the mass component 130 may include an ultrasonic oscillator (sonotrode; also called a horn or front mass) 131 and a rear mass 132, etc.

[0034] The ultrasonic oscillator 131 is a mass component disposed in front of the ultrasonic element 110 (on the side of the eye being examined). The ultrasonic oscillator 131 propagates and amplifies the ultrasonic waves generated by the ultrasonic element 110. In this embodiment, the ultrasonic oscillator 131 is hollow cylindrical. A female thread portion 133 is formed locally on the inner circular side of the ultrasonic oscillator 131. The female thread portion 133 is threadedly connected to the male thread portion 161 formed in the fastening member 160 described later.

[0035] The ultrasonic oscillator 131 in this embodiment is a hollow cylinder with uneven thickness. For example, the ultrasonic oscillator 131 has a shape in which the outer diameter and inner diameter vary along the sound axis O1 direction (long side direction) of the hollow cylinder. For example... Figure 3 As shown, the ultrasonic oscillator 131 has a concave-convex portion 180, which includes a thick-walled portion 181 and a thin-walled portion 182.

[0036] The rear mass portion 132 is a mass component disposed behind the ultrasonic element 110. The rear mass portion 132, together with the ultrasonic oscillator 131, clamps the ultrasonic element 110. The rear mass portion 132 is, for example, cylindrical. A female thread portion 134 is partially formed on the inner circumference of the rear mass portion 132. The female thread portion 134 is threadedly connected to the male thread portion 161 of the fastening member 160, which will be described later. Furthermore, the rear mass portion 132 includes a flange portion 135. The flange portion 135 is held by the mounting portion 400.

[0037] The fastening member 160, for example, fastens the mass member 130 and the ultrasonic element 110 held by the mass member 130. The fastening member 160 is, for example, a hollow bolt. The fastening member 160 is, for example, cylindrical and has a male threaded portion 161 on its outer circumference. The male threaded portion 161 of the fastening member 160 is threadedly connected to female threads 133 and 134 formed on the inner sides of the ultrasonic oscillator 131 and the rear mass member 132. The ultrasonic oscillator 131 and the rear mass member 132 are fastened by the fastening member 160 in a direction of mutual pulling. As a result, the ultrasonic element 110, held between the ultrasonic oscillator 131 and the rear mass member 132, is fastened and pressure is applied.

[0038] Additionally, the ultrasonic actuator 100 may include an insulating member 170. The insulating member 170, for example, prevents the electrode 120 or ultrasonic element 110 from contacting the fastening member 160. The insulating member 170 is, for example, disposed between the electrode 120 and the fastening member 160. The insulating member 170 is, for example, sleeve-shaped.

[0039] <Optical Unit>

[0040] The optical unit 200 is used for, for example, observation or measurement of the eye being examined (see...). Figure 2 The optical unit 200 may include, for example, an objective lens system 210, a frontal imaging system 220, a fixed target projection system 230, a marker projection system 250, a distortion detection system 260, a corneal thickness measurement system 270, a motion distance detection system 280, a cross-sectional imaging system 290, a dichroic mirror 201, a beam splitter 202, a beam splitter 203, and a beam splitter 204.

[0041] The objective lens system 210 is, for example, an optical system for receiving light from outside the measuring unit 3 into the optical unit 200, or for irradiating light from the optical unit 200 to outside the measuring unit 3. The objective lens system 210 may include optical elements. The objective lens system 210 may include optical elements (objective lens, relay lens, etc.).

[0042] The illumination optical system 240 illuminates the eye being examined. The illumination optical system 240 illuminates the eye being examined, for example, using infrared light. The illumination optical system 240 includes, for example, an illumination source 241. The illumination source 241 is, for example, positioned diagonally in front of the eye being examined. The illumination source 241 emits, for example, infrared light. The illumination optical system 240 may include multiple illumination sources 241.

[0043] The frontal imaging system 220, for example, captures images of the observed eye being examined. The frontal imaging system 220, for example, captures images of the anterior portion of the eye being examined. The frontal imaging system 220, for example, includes a light-receiving lens 221 and a light-receiving element 222. The frontal imaging system 220, for example, receives light reflected from the illumination source 241 by the eye being examined. The frontal imaging system 220, for example, receives a reflected light beam from the eye being examined, centered on the optical axis O1. For example, the reflected light from the eye being examined passes through the opening 101 of the ultrasonic actuator 100 and is received by the light-receiving element 222 via the objective lens system 210 and the light-receiving lens 221.

[0044] The fixed target projection system 230 projects a fixed target onto the examined eye, for example. The fixed target projection system 230 includes, for example, a target light source 231, an aperture 232, a projection lens 233, and an aperture 234. Light from the target light source 231 passes along the optical axis O2 through the aperture 232, the projection lens 233, and the aperture 234, and is reflected by the dichroic mirror 201. The dichroic mirror 201, for example, makes the optical axis O2 of the fixed target projection system 230 coaxial with the optical axis O1. The light from the target light source 231, reflected by the dichroic mirror 201, passes along the optical axis O1 through the objective lens system 210 and illuminates the examined eye. The examinee fixates on observing the target of the fixed target projection system 230, thereby stabilizing the examinee's line of sight.

[0045] The marker projection system 250 projects markers, for example, onto the eye being examined. The marker projection system 250 projects markers for XY calibration onto the eye being examined. The marker projection system 250 includes, for example, a marker light source (e.g., an infrared light source) 251, an aperture 252, and a projection lens 253. Light from the marker light source 251 passes along the optical axis O3 through the aperture 252 and the projection lens 253, and is reflected by a beam splitter 202. The beam splitter 202, for example, makes the optical axis O3 of the marker projection system 250 coaxial with the optical axis O1. The light from the marker light source 251 reflected by the beam splitter 202 passes along the optical axis O1 through the objective lens system 210 and illuminates the eye being examined. The light from the marker light source 251 illuminating the eye being examined is reflected by the eye, passes again along the optical axis O1 through the objective lens system 210 and the light-receiving lens 221, and is received by a light-receiving element 222. The markers received by the light-receiving element are used, for example, for XY calibration. In this case, for example, the sign projection system 250 and the frontal camera system 220 function as XY calibration detection units.

[0046] The deformation detection system 260, for example, detects the deformation state of the cornea of ​​the examined eye. The deformation detection system 260 includes, for example, a light-receiving lens 261, an aperture 262, and a light-receiving element 263. The deformation detection system 260 can detect the corneal deformation state based on corneal reflected light received by the light-receiving element 263. For example, the deformation detection system 260 can detect corneal deformation by receiving light from the marker light source 251, which is reflected by the cornea of ​​the examined eye, through the light-receiving element 263. For example, the corneal reflected light passes along the optical axis O1 through the objective lens system 210 and is reflected by beam splitters 202 and 203. Then, the corneal reflected light passes along the optical axis O4 through the light-receiving lens 261 and the aperture 262 and is received by the light-receiving element 263.

[0047] The deformation detection system 260 can detect the corneal deformation state, for example, based on the magnitude of the light-receiving signal from the light-receiving element 263. For instance, the deformation detection system 260 can detect when the cornea is in a flattened state when the light-receiving amount from the light-receiving element 263 is at its maximum. In this case, for example, the deformation detection system 260 is configured to receive the maximum light when the cornea of ​​the examined eye is in a flattened state.

[0048] The corneal thickness measurement system 270 measures, for example, the corneal thickness of an eye being examined. The corneal thickness measurement system 270 may include, for example, a light source 271, a projection lens 272, an aperture 273, a receiving lens 274, and a light-receiving element 275. Light from the light source 271 passes along the optical axis O5 through the projection lens 272 and the aperture 273, and illuminates the eye being examined. Then, the reflected light from the eye is focused along the optical axis O6 by the receiving lens 274 and received by the light-receiving element 275.

[0049] The motion distance detection system 280, for example, detects the calibration state in the Z direction. The motion distance detection system 280, for example, includes a light-receiving element 281. The motion distance detection system 280 can detect the calibration state in the Z direction, for example, by detecting reflected light from the cornea. For example, the motion distance detection system 280 can receive reflected light formed by light from the light source 271 being reflected by the cornea of ​​the examined eye. In this case, the motion distance detection system 280 can, for example, receive a light spot formed by light from the light source 271 being reflected by the cornea of ​​the examined eye. Thus, the light source 271 can also be used as a light source for motion distance detection. For example, light from the light source 271 reflected by the cornea is reflected along the optical axis O6 by the beam splitter 204 and received by the light-receiving element 281.

[0050] <Testing Department>

[0051] The detection unit 500, for example, detects the output of the ultrasonic actuator 100. The detection unit 500 may be a sensor such as an ultrasonic sensor, a displacement sensor, or a pressure sensor. The ultrasonic sensor detects the ultrasonic waves generated by the ultrasonic actuator 100. The displacement sensor detects the displacement of the ultrasonic actuator 100. The displacement sensor can detect the vibration of the ultrasonic actuator 100 when it generates ultrasonic waves by continuously detecting the displacement.

[0052] like Figure 2 As shown, the detection unit 500 is disposed outside the ultrasonic irradiation path A. The irradiation path A is, for example, the area connecting the front surface F of the ultrasonic actuator 100 to the ultrasonic irradiation target Ti. The detection unit 500 is disposed, for example, to the side or rear of the ultrasonic actuator 100. When the detection unit 500 is disposed to the side as in this embodiment, it is easier to observe the eye being examined in the frontal imaging system 220. When an ultrasonic sensor is used as the detection unit 500, the detection unit 500 detects ultrasonic waves leaking from the side or rear of the ultrasonic actuator 100. When a displacement sensor is used as the detection unit 500, the detection unit 500 detects the displacement of the ultrasonic actuator 100 from the side or rear of the ultrasonic actuator 100. The displacement sensor, for example, irradiates the ultrasonic actuator 100 with a laser and detects the displacement of the ultrasonic actuator 100 based on the reflected laser light. The detection signal detected by the detection unit 500 is sent to the control unit.

[0053] <Control Department>

[0054] use Figure 5The structure of the control system will be described below. The control unit 70, for example, performs overall control of the device and calculates and processes measured values. The control unit 70 is implemented, for example, by a typical CPU (Central Processing Unit) 71, ROM 72, RAM 73, etc. The ROM 72 stores various programs and initial values ​​used to control the operation of the ultrasonic tonometer 1. The RAM 73 temporarily stores various information. Furthermore, the control unit 70 can be composed of one or more control units (i.e., multiple processors). The control unit 70 can be connected, for example, to the drive unit 5, storage unit 74, display unit 75, operation unit 76, ultrasonic actuator 100, optical unit 200, and detection unit 500.

[0055] Storage unit 74 is a non-transitory storage medium that retains its stored content even when the power supply is cut off. For example, hard disk drives, flash ROMs, and removable USB memory devices can be used as storage units 74.

[0056] The display unit 75 displays, for example, the measurement results of the examined eye. The display unit 75 may have a touch panel function.

[0057] The operation unit 76 receives various operation instructions from the inspector. The operation unit 76 outputs operation signals corresponding to the input operation instructions to the control unit 70. The operation unit 76 can employ at least one user interface, such as a touch panel, mouse, joystick, or keyboard. Furthermore, if the display unit 75 is a touch panel, the display unit 75 can function as the operation unit 76.

[0058] <Measurement Action>

[0059] The control operation of the device with the above structure will be explained. First, the control unit 70 calibrates the ultrasonic tonometer 1 for the subject's eye, which is supported by the face support unit 4. For example, the control unit 70 drives the drive unit 5 to position the bright spot formed by the frontal image detection mark projection system 250 obtained by the light receiving element 222 so that the position of the bright spot is in a predetermined position. Of course, the examiner can manually calibrate the subject's eye while observing the display unit 75 and using the operation unit 76, etc. If the drive unit 5 is driven, the control unit 70 determines whether the calibration is appropriate by whether the position of the bright spot in the anterior eye image is in the predetermined position.

[0060] After calibration of the examined eye E, the control unit 70 measures the corneal thickness using the corneal thickness measurement system 270. For example, the control unit 70 calculates the corneal thickness based on the light-receiving signal received by the light-receiving element 275. For example, the control unit 70 can determine the corneal thickness based on the positional relationship between the peak value of reflected light from the corneal surface and the peak value of reflected light from the posterior surface of the cornea, according to the light-receiving signal. The control unit 70 stores the calculated corneal thickness in the storage unit 74, for example.

[0061] Next, the control unit 70 uses the ultrasonic actuator 100 to measure the intraocular pressure of the examined eye. For example, the control unit 70 applies a burst signal of voltage to the ultrasonic element 110 to irradiate the examined eye E with ultrasonic waves. If acoustic radiation pressure is generated in the cornea of ​​the examined eye due to the ultrasonic waves irradiated from the ultrasonic actuator 100, the cornea deforms. The control unit 70 detects the deformation state of the cornea through the deformation detection system 260. For example, the control unit 70 detects whether the cornea has deformed into a predetermined shape (flattened state or flattened state) based on the light-receiving signal of the light-receiving element 263. As the acoustic radiation pressure gradually increases, the cornea becomes flattened (flattened state). At this time, the signal of the deformation detection system 260 becomes maximum, and the control unit 70 determines that the cornea has become flattened.

[0062] If the acoustic radiation pressure increases further, the cornea becomes concave. At this time, the light-receiving signal of the deformation detection system 260 weakens. The control unit 70 gradually weakens and then stops the ultrasonic irradiation. As a result, the cornea recovers from the concave state to the flattened state. At this time, the light-receiving signal becomes maximum again. Then, as the cornea returns to its original shape, the light-receiving signal of the deformation detection system 260 also weakens.

[0063] The control unit 70 calculates the intraocular pressure (IOP) of the examined eye, for example, based on the acoustic radiation pressure when the cornea of ​​the examined eye is deformed into a predetermined shape. The acoustic radiation pressure applied to the examined eye is related to the ultrasound irradiation time and increases with the increase of ultrasound irradiation time. Therefore, the control unit 70 calculates the acoustic radiation pressure when the cornea is deformed into a predetermined shape based on the ultrasound irradiation time. The relationship between the acoustic radiation pressure when the cornea is deformed into a predetermined shape and the IOP of the examined eye is determined in advance through experiments, etc., and stored in the storage unit 74, etc. The control unit 70 determines the IOP of the examined eye based on the acoustic radiation pressure when the cornea is deformed into a predetermined shape and the relationship stored in the storage unit 74.

[0064] Amplitude Modulation of Burst Signals

[0065] The control unit 70 performs amplitude modulation on the burst signal of the voltage applied to the ultrasonic element 110. For example... Figure 6A This shows the burst signal B1 before amplitude modulation. Figure 6B This shows the amplitude-modulated burst signal B2. (Example:) Figure 6A , Figure 6B As shown, the amplitude of the burst signal B1 before amplitude modulation is constant, while the amplitude of the burst signal B2 after amplitude modulation changes. For example, the control unit 70 performs amplitude modulation by gradually increasing and then gradually decreasing the voltage. For example, the control unit 70 can use a sine wave as the modulation wave. That is, amplitude modulation can be performed by gradually increasing and then gradually decreasing the amplitude of the burst signal according to the waveform of a sine wave.

[0066] Figure 7AIt is the change of acoustic radiation pressure over time when a burst signal B1 is applied to the ultrasonic actuator 100. Figure 7B This is the time-varying acoustic radiation pressure when a burst signal B2 is applied to the ultrasonic actuator 100. For example... Figure 7A , Figure 7B As shown, compared to the case where a burst signal B1 with a constant amplitude is applied, the rise of the acoustic radiation pressure becomes slower when a burst signal B2 with amplitude modulation is applied. In other words, the control unit 70 can change the rate of rise of the acoustic radiation pressure (e.g., the amount of rise per unit time) by modulating the amplitude of the voltage applied to the ultrasonic element 110.

[0067] For example, the acoustic radiation pressure required to measure intraocular pressure J1 for the examined eye is set as K1, and the acoustic radiation pressure required to measure intraocular pressure J2 (>J1), which is greater than intraocular pressure J2, is set as K2 (see...). Figure 7A , Figure 7B Additionally, the time from the application of the burst signal B1 to the attainment of the acoustic radiation pressure K1 is defined as t11, and the time from the application of the burst signal B1 to the attainment of the acoustic radiation pressure K2 is defined as t12 (see [reference]). Figure 7A Furthermore, the time from the application of the burst signal B2 to the attainment of the acoustic radiation pressure K1 is defined as t21, and the time from the application of the burst signal B2 to the attainment of the acoustic radiation pressure K2 is defined as t22 (see [reference]). Figure 7B ).like Figure 7A , Figure 7B As shown, by modulating the amplitude of the voltage signal to gradually increase the voltage, the pressure rise becomes slower. Therefore, the time interval Δt2 between time t21 and time t22 becomes larger than the time interval Δt1 between time t11 and time t12, improving the time resolution. In other words, by slowing the rise of the acoustic radiation pressure, the peak interval of the corneal deformation signal for each intraocular pressure value is widened, reducing the possibility of falsely detecting the peak position of each intraocular pressure value. Thus, the accuracy of intraocular pressure measurement is improved.

[0068] <Lag Calculation>

[0069] Furthermore, the control unit 70 can fully deform the cornea using ultrasound from a Langevin-type oscillator, thereby calculating the corneal hysteresis. Hysteresis is used, for example, as an indicator of corneal rigidity. For instance, the control unit 70 can calculate the corneal hysteresis based on the light-receiving signal from the deformation detection system 260 when the cornea is deformed by ultrasound. For example, in… Figure 8In the light-receiving signal Sg of the deformation detection system 260 shown, the time interval t1 when the signal intensity reaches its maximum as the cornea changes from its normal shape to a flattened state, and the time t2 when the signal intensity reaches its maximum again as the cornea recovers from a concave state to a flattened state, is defined as time Δt. Furthermore, the difference between the signal intensity V1 in the flattened state and the signal intensity V2 in the state of maximum deformation (concavity) is defined as intensity difference ΔV. The control unit 70 can calculate the corneal hysteresis based on these parameters. For example, the control unit 70 can calculate the hysteresis using time Δt, intensity difference ΔV, etc., or it can calculate the hysteresis based on the corneal separation rate (the separation ratio of reflections from the cornea) calculated using ΔV / Δt. Alternatively, the control unit 70 can calculate the hysteresis using time Δt or intensity difference ΔV relative to time t1, etc.

[0070] Furthermore, the method for determining hysteresis is not limited to the methods described above. For example, the control unit 70 can calculate the corneal hysteresis from the change in the light-receiving signal Sg of the deformation detection system 260 over time. For example, the time from when the cornea begins to deform until it returns to its original shape, the time from when the cornea begins to deform until the deformation reaches its maximum, or the time from when the cornea reaches its maximum deformation until it returns to its original shape can be used as hysteresis. Additionally, the control unit 70 can use the slope of the signal intensity from when the cornea begins to deform until the deformation reaches its maximum, or the slope of the signal intensity from when the cornea reaches its maximum deformation until it returns to its original shape, as hysteresis. The control unit 70 can, for example, use hysteresis as one of the indicators representing the corneal deformation state over time.

[0071] Additionally, for example in Figure 8 In the coordinate graph of acoustic radiation pressure P, the control unit 70 can calculate the pressure difference ΔP between the acoustic radiation pressure P1 at time t1 and the acoustic radiation pressure P2 at time t2 as a hysteresis. The control unit 70 can, for example, use the calculated hysteresis to correct intraocular pressure. For example, when the hysteresis parameter is a value when the corneal rigidity is low, the intraocular pressure can be corrected more effectively.

[0072] Furthermore, as mentioned above, the method for calculating intraocular pressure (IOP) is not limited to the method based on the output of the ultrasonic actuator 100 when the cornea undergoes a predetermined deformation; various methods can be employed. For example, the control unit 70 can determine the amount of corneal deformation using the deformation detection system 260 and calculate the IOP by multiplying the deformation amount by a conversion factor. Additionally, the control unit 70 can, for example, correct the calculated IOP value based on the corneal thickness of the examined eye.

[0073] In addition, the control unit 70 can measure intraocular pressure based on ultrasound waves reflected by the examined eye. For example, intraocular pressure can be measured based on changes in the characteristics of ultrasound waves reflected by the examined eye, or the amount of corneal deformation can be obtained from ultrasound waves reflected by the examined eye, and intraocular pressure can be measured based on this amount of deformation.

[0074] Explanation of reference numerals in the attached figures

[0075] 1. Ultrasonic tonometer

[0076] 2 abutment

[0077] 3 Measurement Section

[0078] 4. Face support

[0079] 5. Drive Unit

[0080] 70 Control Department

[0081] 75 Display Section

[0082] 76 Operations Department

[0083] 100 Ultrasonic Actuator

[0084] 101 Opening

[0085] 200 optical units.

Claims

1. An ultrasonic tonometer, used to measure the intraocular pressure of an eye under examination using ultrasound, characterized in that, including: an ultrasonic wave actuator that irradiates an ultrasonic wave to an eye to be examined; and a control unit that applies a burst signal after amplitude modulation to the ultrasonic wave actuator, the control unit modulates the burst signal so that the amplitude gradually increases, thereby changing a rising rate of an acoustic radiation pressure in such a manner that the rising of the acoustic radiation pressure becomes gentle, and calculates an intraocular pressure of the eye to be examined from the acoustic radiation pressure at the time when the cornea of the eye to be examined is deformed into a prescribed shape, and improves a time resolution compared with a case where a burst signal with a constant amplitude is applied.

2. The ultrasonic wave tonometer according to claim 1, wherein the control unit modulates the burst signal using a sine wave as a modulation wave.

3. The ultrasonic wave tonometer according to claim 1 or 2, comprising: a deformation detection unit that detects a deformation state of the cornea, the control unit calculates a hysteresis of the cornea based on the deformation state of the cornea obtained by the deformation detection unit.

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