JP2015008955A - Non-contact ultrasonic tonometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact ultrasonic tonometer capable of accurately measuring intraocular pressure by ultrasonic waves.SOLUTION: A non-contact ultrasonic tonometer comprises: a vibrator that emits ultrasonic waves for bringing about infinitesimal deformation of the cornea of an eye to be examined; measurement means for measuring the deformation volume and deformation speed of the cornea deformed by the ultrasonic waves; and intraocular pressure calculation means for calculating the intraocular pressure of the eye to be examined, on the basis of the deformation volume and the deformation speed, which are measured by the measurement means.

Description

  The present invention relates to a non-contact ultrasonic tonometer that measures intraocular pressure of a subject's eye in a non-contact manner using ultrasonic waves.

  As a non-contact tonometer, an air jet tonometer is still common. The air-jet tonometer converts the air pressure in a predetermined deformed state into an intraocular pressure by detecting the applanation state of the cornea when air is injected into the cornea and the air pressure injected into the cornea.

  An ultrasonic tonometer based on the same concept as the air jet tonometer has been proposed (see Patent Document 1). The ultrasonic tonometer of Patent Document 1 detects the radiation pressure in a predetermined deformed state by detecting the applanation state of the cornea when the ultrasonic wave is radiated to the cornea and the radiation pressure injected to the cornea. It was converted to pressure.

As an ultrasonic tonometer that measures intraocular pressure using ultrasonic waves, a device that measures intraocular pressure based on the relationship between the characteristics (amplitude and phase) of reflected waves from the cornea and intraocular pressure has been proposed. (See Patent Document 2).
JP-A-5-253190 JP 2009-268651 A

  An air-jet tonometer was a burden on the subject's eye. Further, the ultrasonic tonometer has not reached a practical level, and various improvements are required. The device of Patent Document 1 requires an ultrasonic pressure that can flatten or dent the cornea. Therefore, the burden on the subject remains before. Since the apparatus of Patent Document 2 has a weak S / N ratio of the reflected wave, the measurement accuracy at a level comparable to that of the air injection type has not been obtained so far.

  In view of the above-described prior art, an object of the present invention is to provide a non-contact ultrasonic tonometer that can accurately measure intraocular pressure with ultrasonic waves.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

  A non-contact ultrasonic tonometer, a vibrator for emitting ultrasonic waves for minutely deforming the eye cornea to be examined, and a measuring means for measuring the deformation amount and deformation speed of the cornea deformed by the ultrasonic waves And intraocular pressure calculating means for calculating intraocular pressure of the eye to be examined based on the deformation amount and the deformation speed measured by the measuring means.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external configuration diagram of a non-contact ultrasonic tonometer according to the present embodiment. The non-contact ultrasonic tonometer 100 is a so-called stationary non-contact ultrasonic tonometer, and is movable on the base 1, the face support unit 2 attached to the base 1, and the base 1. And a measuring unit (measuring unit) 4 that is movably provided on the moving table 3 and houses a measurement system and an optical system, which will be described later. The measuring unit 4 is moved in the left and right direction (X direction), the up and down direction (Y direction), and the front and rear direction (Z direction) with respect to the eye E by an XYZ driving unit 6 provided on the moving table 3. The movable table 3 is moved in the X direction and the Z direction on the base 1 by operating the joystick 5. Further, when the examiner rotates the rotary knob 5 a, the measurement unit 4 is moved in the Y direction by the Y drive of the XYZ drive unit 6. On the top of the joystick 5, a measurement start switch 5b is provided. A display monitor 72 is provided on the movable table 3.

FIG. 2 is a diagram for explaining a measurement system and an optical system of the non-contact ultrasonic tonometer according to the present embodiment, and is a specific example when a probe is arranged in the observation optical path. FIG. 3 is a diagram for explaining a control system of the non-contact ultrasonic tonometer according to the present embodiment.
A probe (transducer) 10 includes a vibrator 11 that emits ultrasonic waves for minutely deforming an eye cornea to be examined. The probe (transducer) 10 is disposed in front of the eye E, for example. For example, a piezoelectric element is used for the probe 10. In the present embodiment, a pulse wave is used as the ultrasonic wave incident on the eye to be examined, and the vibrator 11 is used as an ultrasonic wave incident unit for causing the ultrasonic pulse to be incident on the eye to be examined.

  In the present embodiment, the vibrator 11 requires an output sufficient to deform (flatten) the cornea Ec. However, a radiation pressure that can flatten or dent the cornea is not required. Hereinafter, the sound pressure necessary for deforming (flattening) the cornea Ec will be described.

  The sound pressure becomes 10 mmHg when applanating 3.06 mm in diameter with a weight of 1 g. The sound pressure at this time is derived by the following calculation when the intraocular pressure of the eye to be examined is 60 mmHg.

  According to the above equation, in order to flatten the eye to be examined having an intraocular pressure of 60 mmHg by a range of 3.06 mm in diameter, the sound pressure level is theoretically 172 dB.

  However, at 172 dB, the cornea may be damaged depending on the irradiation time. In this embodiment, instead of obtaining the applanation of the cornea, the intraocular pressure can be measured if physical deformation with hysteresis occurs. Therefore, the applanation requires a sound pressure of 172 dB, but the irradiation time is extremely shortened to a few [ns] (nanoseconds), or an acoustic energy of about 6 [W / cm ^ 2] (about 167 dB). By doing so, the displacement of the cornea may be obtained.

  In the present embodiment, an ultrasonic pulse is incident on the eye to be inspected using the probe 10 that can emit ultrasonic waves that can detect deformation of the cornea. The sound pressure level of the ultrasonic wave incident on the eye to be inspected only needs to be able to output an ultrasonic wave that can deform (flatten) the cornea Ec.

  In addition, as a frequency of the ultrasonic wave incident on the subject's eye, for example, a frequency larger than the audible range is preferable so that the subject cannot hear it. Moreover, the ultrasonic wave attenuates in the air as the frequency increases. For this reason, a frequency that exceeds the audible range and has a small attenuation in the air is preferable. For example, 40 to 200 KHz is preferable. In the present embodiment, for example, the vibrator 11 having a frequency of 50 KHz and capable of outputting an ultrasonic wave of 50 KHz is used.

  In addition, if there exists an irradiation reference | standard when irradiating a human body with an ultrasonic wave via air, this content shall follow it.

  Further, an acoustic lens 16 for converging the ultrasonic wave emitted from the transducer 11 is provided on the eye side of the probe 10 so that the alignment between the eye to be examined and the probe 10 is appropriate. Sometimes, the eye to be examined is in focus.

  Returning to the description of FIG. A light beam for projecting a fixation target emitted from a fixation light source 32 (described later) and a light flux for projecting an alignment index emitted from an alignment light source 42 pass through the center of the probe 10 and the acoustic lens 16. An opening 18 (for example, a circular hole having a diameter of about 1 mm) is formed.

  Further, the vibrator 11 arranged at the center of the objective lens 22 and the circuit system (amplifier circuit 81, control unit 70, etc.) arranged at a position deviated from the optical path of the observation optical system 20 are provided with a wiring cable 95. Are electrically connected.

  Next, the configuration of the optical system will be described. In this optical system, an observation optical system 20 for observing the anterior segment of the subject's eye, a fixation target projection optical system 30 for fixing the subject's eye, and an index for XY alignment on the subject's eye cornea. A first index projection optical system 40 for projecting, an index projection optical system 50 for projecting an index for alignment detection in the working distance direction onto the eye cornea, and an index for alignment detection in the working distance direction projected onto the eye cornea A distance index detection optical system 55 is provided for detecting.

  In the observation optical system 20, the probe 10 is disposed in the observation optical path, and an anterior ocular segment image is formed through the peripheral region of the probe 10. More specifically, the observation optical system 20 includes an objective lens 22, an imaging lens 24, a filter 25, and a two-dimensional image sensor 26, and the probe 10 is disposed on the observation optical axis L1. . For this reason, when the observation optical axis L1 is aligned with a predetermined part (for example, the center of the cornea and the center of the pupil) of the eye to be examined, the probe 10 is disposed in front of the eye to be examined. Further, in the configuration shown in FIG. 2, since the central axis of the probe 10 (extension line of the central axis) and the observation optical axis L1 are arranged coaxially, the observation light is applied to a predetermined part of the eye to be examined. When the axis L1 is aligned, the center axis of the probe 10 (extended line of the center axis) and the predetermined part of the eye to be inspected coincide with each other, so that reflected waves from the eye to be inspected by ultrasound can be efficiently acquired. .

  An anterior ocular segment illumination light source 38 for illuminating the subject eye with infrared light is disposed obliquely in front of the subject eye. The filter 25 transmits light from the light source 38 and a light source 42 to be described later, and has an opaque characteristic to light from a light source 51 for detecting a working distance to be described later.

  Here, the anterior ocular segment reflected light from the anterior ocular segment illumination light source 38 travels toward the objective lens 22. In this case, the anterior ocular segment reflected light that has reached the peripheral region of the probe 10 passes through the objective lens 22 and passes through the beam splitter 36 and the beam splitter 46 to the two-dimensional imaging device 26 by the imaging lens 24. Imaged.

  In the above configuration, the two-dimensional image sensor 26 is used as an image sensor for anterior segment observation. Then, the imaging signal output from the two-dimensional imaging device 26 is input to the control unit 70 and displayed on the screen of the display monitor 72. The imaging optical system including the objective lens 22 and the imaging lens 24 is used as a light guide member that guides the anterior eye image of the eye to be examined to the two-dimensional imaging device 26.

  As a specific configuration in which the objective lens 22 is arranged at the same position with respect to the probe 10, a configuration as shown in FIG. An insertion hole 22a into which the probe 10 is inserted is formed in the objective lens 22, and the probe 10 is attached to the objective lens 22 through the insertion hole 22a.

  Returning to the description of FIG. The fixation target projection optical system 30 has at least a fixation light source for fixation target projection, and projects a fixation target for fixing the eye to be examined toward the eye to be examined. More specifically, the fixation target projection optical system 30 includes a fixation light source 32 that emits visible light, a fixation target 33, an aperture stop 34, a projection lens 35, a beam splitter 46, and a beam splitter 36. Then, the fixation target is projected onto the eye to be examined through the opening 18 formed in the probe 10 and the acoustic lens 16. The projection optical axis L2 of the fixation target projection optical system 30 is coaxial with the observation optical axis L1 by the beam splitter 46 disposed in the optical path of the observation optical system 20.

  Here, the light from the fixation target 33 that is illuminated by the light beam for projecting the fixation target emitted from the light source 32 passes through the projection lens 35 after the diameter of the light beam is reduced by the aperture stop 34, and then the beam splitter. After being reflected by 46, it passes through the beam splitter 36 and the opening 18 toward the eye to be examined and is projected onto the fundus of the eye to be examined. Thereby, fixation of the eye to be examined is performed.

  The first index projection optical system 40 includes at least an alignment light source for alignment index projection, and projects the alignment index from the front direction toward the anterior eye portion to be examined. More specifically, the first index projection optical system 40 includes an alignment light source 42 that emits infrared light, a projection lens 44, and a beam splitter 36, and the opening 18 formed in the probe 10. An XY alignment index is projected onto the eye cornea through the eye. Further, the projection optical axis L3 of the alignment index projection optical system 40 is coaxial with the observation optical axis L1 by the beam splitter 36 disposed in the optical path of the observation optical system 20.

  The working distance index projection optical system 50 has an infrared light source 51 and a projection lens 52 for alignment detection in the Z direction (front-rear direction), and displays an index for alignment detection in the working distance (Z) direction on the eye cornea. Project to. Note that the projection optical axis L4 of the projection optical system 50 intersects the observation optical axis L1 at a predetermined angle. Here, the light from the light source 51 is converted into a substantially parallel light beam by the projection lens 52, and then projected from the oblique direction onto the cornea of the eye along the projection optical axis L 4. The light beam specularly reflected by the cornea Ec is a virtual image of the light source 51. An index i2 is formed.

  The working distance index detection optical system 55 includes a light receiving lens 56, a filter 57, and a position detection element 58 (for example, a line CCD), and detects an alignment index image formed by the distance index projection optical system 50. The filter 57 transmits light from the light source 51 and has a characteristic that does not transmit light from the light sources 38 and 42. The projection optical axis L5 of the working distance index detection optical system 55 and the projection optical axis L4 of the working distance index projection optical system 50 have an axis symmetrical to the observation optical axis L1, and the optical axis L5 is an optical axis L4 and a light beam. Cross on axis L1. Here, the light beam from the index i <b> 2 is imaged on the position detection element 58 via the filter 57 by the light receiving lens 56. When the eye E (cornea Ec) moves in the Z direction, the index i2 moves on the position detection element 58. Therefore, the probe 10 is aligned with the eye E in the Z direction based on the detection signal from the position detection element 58. The state can be detected.

  In this embodiment, the working distance index projection optical system 50 and the working distance index detection optical system 55 are used as a measurement unit for measuring the deformation amount and the deformation speed of the cornea deformed by ultrasonic waves. The deformation amount and the deformation speed may be detected optically or may be detected by ultrasonic waves. Alternatively, other displacement detection sensors may be used.

  For example, the control unit 70 monitors the amount of deformation of the cornea due to ultrasonic waves over time based on the detection signal from the position detection element 58. The control unit 70 calculates the deformation amount of the cornea deformed by the ultrasonic waves and the speed at which the cornea is deformed by the ultrasonic waves. The control unit 70 measures the intraocular pressure based on the calculation result (details will be described later).

  In the present embodiment, the measurement unit that optically measures the deformation amount and the deformation speed also serves as a unit that optically detects the alignment state with respect to the eye E in the Z direction. This simplifies the device configuration. As a measurement unit that optically measures the deformation amount and the deformation speed, an anterior ocular segment image capturing unit such as an OCT or a Scheimpflug camera may be used.

  Next, the configuration of the control system will be described with reference to FIG. The control unit 70 includes a light source 32, a light source 42, a light source 51, a two-dimensional imaging device 26, a position detection device 58, a light source 38, a display monitor 72, a memory 75 as a storage unit, a rotation knob 5a, a measurement start switch 5b, and various switches. Are connected to the control unit 74, the XYZ drive unit 6, and the like, which perform control of the entire apparatus, calculation processing of measured values, and the like.

  The control unit 70 performs alignment detection in the XY directions based on the detection signal from the two-dimensional image sensor 26 and performs alignment detection in the Z direction based on the detection signal from the position detection element 58. The control unit 74 includes a selection switch 74a for selecting an automatic alignment mode for automatically aligning the measuring unit 4 with respect to the eye to be examined and a manual alignment mode for manually aligning the measuring unit 4 with respect to the eye to be examined. A selection switch 74b for selecting an auto shot mode for automatically issuing a measurement start trigger when alignment is completed and a manual shot mode for generating a measurement start trigger based on an operation signal from the measurement start switch 5b are arranged. Yes.

  The operation of the apparatus having the above configuration will be described. First, the examiner fixes the subject's face to the face support unit 2 and then aligns the subject's eye with the joystick 5 while viewing the display monitor 72. At this time, as shown in FIG. 4, the control unit 70 displays on the monitor 72 an anterior segment image acquired by the two-dimensional image sensor 26 and a reticle LT and an indicator G used for alignment with the eye to be examined. And display it.

  When a trigger signal for starting measurement is issued (input) after the alignment for the eye to be examined is completed, the control unit 70 continuously uses the vibrator 11 to direct ultrasonic pulses toward the eye to be examined based on the trigger signal. May be emitted automatically. Of course, the ultrasonic pulse may be single. The ultrasonic wave radiated to the cornea may be a continuous wave.

  In the present embodiment, the control unit 70 measures the intraocular pressure of the eye to be examined based on the deformation amount and the deformation speed of the cornea during vibration. In the following description, the control unit 70 calculates corneal hysteresis due to ultrasonic deformation based on the measured deformation speed. The control unit 70 calculates the intraocular pressure of the eye to be examined based on the measured deformation amount of the cornea and the calculated hysteresis.

  FIG. 5 is a diagram illustrating an example of a pulse signal for irradiating ultrasonic waves. FIG. 5 is an example of the pulse signal Sg <b> 1 formed by the voltage applied from the control unit 70 to the vibration 11. The vibrator 11 vibrates when the pulse signal Sg1 is applied to generate an ultrasonic pulse.

  In the present embodiment, the ultrasonic pulse has a frequency of 50 KHz, for example. The control unit 70 controls the pulse signal Sg1 so that the ultrasonic pulse is incident on the cornea Ec five times as the repetition frequency PRF.

  The repetition frequency PRF is preferably set so that the subsequent ultrasonic pulse enters the cornea Ec after the cornea Ec deformed (flattened) by the ultrasonic pulse previously incident returns to its original shape. . Therefore, the repetition frequency PRF is preferably set by the frequency of the ultrasonic pulse and the predicted value (described later) of the hysteresis H of the cornea Ec.

  The cornea Ec is forcibly vibrated and deformed (flattened) by a continuous ultrasonic pulse. The working distance index projection optical system 50 and the working distance index detection optical system 55 detect the deformation amount W of the deformed (flat) cornea Ec.

  FIG. 6 is a diagram illustrating an example for explaining the deformation amount W of the cornea Ec by ultrasonic waves. The position detection element 58 detects the reflected light of the light source 11 reflected by the cornea Ec. When the cornea Ec is vibrated and deformed (flattened) by the ultrasonic pulse, the direction of the reflected light from the light source 11 changes, and the peak position of the detection signal received by the position detection element 58 changes. The controller 70 detects the deformation amount W of the cornea Ec based on the change amount of the peak position. For example, the amount of change in the peak position may be converted to the deformation amount W of the cornea Ec using a conversion formula obtained experimentally in advance.

  For example, the control unit 70 acquires the temporal deformation amount W of the cornea Ec based on the detection signal detected by the position detection element 58, and stores the memory 75. The stored deformation amount W is used for calculation of intraocular pressure. The deformation amount W may be, for example, the maximum value of the deformation amount W or the deformation amount after a predetermined time has elapsed since the start of deformation.

  FIG. 7 is a graph showing temporal changes in the deformation amount W of the cornea Ec measured by the working distance index projection optical system 50 and the working distance index detection optical system 55.

  The control unit 70 obtains the hysteresis H of the cornea Ec based on the time (speed) required for the cornea to return to the shape before deformation.

  For example, the control unit 70 calculates the hysteresis H of the cornea Ec from the temporal change in the deformation amount W of the cornea Ec. In FIG. 7, a time Tr indicates a time from when the cornea Ec starts to be deformed until it returns to the original shape. The time Tf indicates the time from when the cornea Ec starts to deform until the deformation amount W reaches the maximum (deformation amount Wmax). The time Ts indicates the time from when the deformation amount W of the cornea Ec becomes maximum until it returns to the original shape. The inclination Df indicates the inclination of the deformation amount W from when the cornea Ec starts to deform until the deformation amount W reaches the maximum (deformation amount Wmax). The inclination Ds indicates the inclination of the deformation amount W from when the deformation amount W of the cornea Ec becomes maximum until it returns to the original shape. The control unit 70 calculates, as the hysteresis H, at least one temporal component of the time and the slope such as the time Tr, the time Tf, the time Ts, the slope Df, and the slope Ds. Hysteresis is used, for example, as one of indices indicating the temporal deformation state of the cornea.

  Subsequently, the control unit 70 calculates the intraocular pressure based on the calculated hysteresis H and the deformation amount W, for example. There are various methods for calculating intraocular pressure. For example, the intraocular pressure may be obtained by multiplying the maximum deformation amount Wmax and the hysteresis H and further multiplying by a conversion coefficient.

  Thus, the intraocular pressure can be calculated based on the deformation amount W of the cornea Ec and the hysteresis H of the cornea Ec.

  For example, when jetting compressed air to deform the eye to be examined, it takes about 25 [ms]. If ultrasonic waves are used instead of air, the time is reduced to about 1/1000. This is because the propagation speed of ultrasonic waves traveling in the air is faster than the air ejection speed. The time during which the cornea Ec is deformed (flattened) by ultrasonic waves is very short, and the subject does not feel uncomfortable due to the deformation (flattened) of the cornea Ec.

  Therefore, as described above, by using ultrasonic waves to deform the cornea of the eye to be examined, the intraocular pressure can be measured without giving the subject a feeling of fear or discomfort.

  As described above, by obtaining the deformation amount W and the hysteresis H of the cornea Ec, the influence of the hysteresis H is small, and a more accurate intraocular pressure value can be obtained.

  In addition, the variation in the deformation amount of the cornea Ec can be detected by continuously irradiating the ultrasonic pulse. Therefore, a more accurate intraocular pressure value can be obtained by using the variation in deformation amount for correcting the intraocular pressure value.

  In the above description, when calculating the intraocular pressure, the intraocular pressure is calculated by multiplying the deformation amount W of the cornea Ec and the hysteresis H, and further multiplying the conversion factor. Not exclusively. For example, the final intraocular pressure value may be obtained by multiplying the deformation amount W of the cornea Ec by a conversion factor and correcting the obtained intraocular pressure value with the hysteresis H.

  In the present embodiment, the pulse wave has been described as being continuously incident on the cornea Ec. However, the present invention is not limited to this. For example, as shown in FIG. 8, burst waves may be continuously incident. By making the burst wave incident, the S / N ratio can be increased.

  In the above description, the corneal hysteresis is obtained as the deformation speed of the cornea, but the present invention is not limited to this. For example, the moving speed of the cornea deformed by ultrasonic waves (for example, the moving speed of the apex of the cornea) may be measured using an anterior ocular segment image capturing unit such as an OCT or a Scheimpflug camera. The control unit 70 measures the intraocular pressure using the obtained moving speed. Note that the present invention is not limited to the anterior segment cross-sectional image capturing unit, and some speedometer may be used.

  In addition, in the above description, although it was set as the structure which irradiates the to-be-examined eye directly with the ultrasonic wave from the vibrator | oscillator 11, it is not limited to this. For example, the subject's eye may be irradiated with ultrasonic waves via the ultrasonic reflection mirror 90 (see FIG. 9). FIG. 9 is a diagram showing an example in which an ultrasonic reflection mirror is used. The components denoted by the same reference numerals as those in FIG. 2 perform the same functions as those in FIG. For example, the ultrasonic reflection mirror 90 may be disposed in the observation optical path of the observation optical system 20. The vibrator 11 may be disposed outside the observation optical path of the observation optical system 20.

It is an external appearance block diagram of the non-contact-type ultrasonic tonometer concerning this embodiment. It is a figure explaining the measurement system and optical system of the non-contact-type ultrasonic tonometer concerning this embodiment. It is a figure explaining the control system of the non-contact-type ultrasonic tonometer concerning this embodiment. The anterior ocular segment observation screen displayed on the display monitor will be described. It is a figure which shows the pulse signal applied to a vibrator | oscillator. It is a figure which shows a mode that the deformation amount of a cornea is measured. It is a graph which shows the time change of the deformation | transformation amount of a cornea. It is a figure which shows an example of a pulse signal. It is a figure explaining the specific example of the structure by which the probe is arrange | positioned out of the observation optical path of an observation optical system.

DESCRIPTION OF SYMBOLS 10 Probe 11 Vibrator 16 Acoustic lens 18 Aperture 20 Observation optical system L1 Observation optical axis 22 Objective lens 30 Fixation target projection optical system 40 First index projection optical system 55 Working distance index projection optical system 70 Control unit 81 Amplifier 90 Ultrasonic reflection member 310 Measurement optical system

Claims (5)

A vibrator that emits ultrasonic waves for minutely deforming the eye cornea to be examined;
A measuring means for measuring a deformation amount and a deformation speed of the cornea deformed by the ultrasonic wave,
A non-contact ultrasonic tonometer comprising: an intraocular pressure calculating unit that calculates an intraocular pressure of the eye to be examined based on the deformation amount and the deformation speed measured by the measuring unit. The non-contact ultrasonic tonometer according to claim 1, further comprising hysteresis calculating means for calculating hysteresis of the cornea based on the deformation speed measured by the measuring means,
The non-contact ultrasonic tonometer calculates the intraocular pressure of the eye to be examined based on the deformation amount of the cornea and the hysteresis calculated by the hysteresis calculating unit. The non-contact ultrasonic tonometer according to claim 1,
Control means for controlling the vibrator and vibrating the cornea by continuously irradiating the cornea with a pulse wave;
The intraocular pressure calculating means is a non-contact ultrasonic tonometer for measuring intraocular pressure of the eye to be examined based on a deformation amount and a deformation speed of the cornea during vibration. The non-contact ultrasonic tonometer according to claim 3,
The control means is a non-contact ultrasonic tonometer that controls the vibrator and continuously irradiates the cornea with a burst wave. The non-contact ultrasonic tonometer according to claim 1 or 2,
The measuring means includes
A measuring means for optically measuring a deformation amount and a deformation speed of the cornea deformed by the ultrasonic wave, and also serving as an alignment detecting means for optically detecting an alignment state with respect to an eye to be examined in a working distance direction. Non-contact ultrasonic tonometer.

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