Ultrasonic ophthalmic tonometer

Abstract

The present invention addresses the technical problem of providing an ultrasonic ophthalmic tonometer that can use a plurality of ultrasonic wave elements to irradiate a subject's eye with ultrasonic waves of sufficient output for eye pressure measurement, and an ultrasonic ophthalmic tonometer control program. An ultrasonic ophthalmic tonometer that measures the eye pressure of a subject's eye using ultrasonic waves is characterized by comprising an imaging optical system that images the subject's eye, and an irradiation means that includes a plurality of ultrasonic wave elements and a support member that supports the ultrasonic wave elements, and that irradiates the subject's eye with ultrasonic waves, the support member having an opening portion for passing the optical axis of the imaging optical system.

Description

Ultrasonic tonometer

[0001] The present disclosure relates to an ultrasonic tonometer that measures intraocular pressure in a subject's eye using ultrasound.

[0002] The most common non-contact tonometer is the air-injection tonometer, which detects the deformation of the cornea when air is injected onto it and the pressure of the air injected onto the cornea, and converts the air pressure when the cornea is applanated into intraocular pressure.

[0003] Another non-contact tonometer proposed is an ultrasonic tonometer that measures intraocular pressure using ultrasound (see Patent Document 1). The ultrasonic tonometer in Patent Document 1 detects the deformation state of the cornea when ultrasound is radiated onto the cornea and the radiation pressure emitted onto the cornea, and converts the radiation pressure in an applanated state into intraocular pressure.

[0004] Furthermore, as an ultrasonic tonometer, a non-contact ocular vibration type tonometer has been proposed that calculates the intraocular pressure of the subject's eye based on vibration data of the subject's eye in response to sound waves from a parametric speaker using multiple ultrasonic elements (see Patent Document 2).

[0005] JP 5-253190 JP 2015-092980

[0006] Incidentally, when using multiple ultrasonic elements, if a parametric speaker is placed obliquely to the subject's eye as in Patent Document 2 in order to position an observation optical system for observing the anterior segment of the subject's eye, it is not possible to generate an acoustic radiation pressure (or sound pressure) high enough to deform the cornea into a predetermined state (e.g., applanation state) and measure the intraocular pressure as in Patent Document 1.

[0007] In view of the problems of the related art, the present disclosure has as its technical object to provide an ultrasonic tonometer that can irradiate an examinee's eye with ultrasonic waves of sufficient output for measuring intraocular pressure using a plurality of ultrasonic elements.

[0008] In order to solve the above problems, the present disclosure is characterized by having the following configuration.

[0009] (1) An ultrasonic tonometer for measuring the intraocular pressure of a test eye using ultrasound, comprising: an imaging optical system for imaging the test eye; a plurality of ultrasonic elements; and an irradiation means for irradiating the test eye with ultrasound, the irradiation means having a support member for supporting the ultrasonic elements, wherein an opening for passing the optical axis of the imaging optical system is provided in the support member.

[0010] 1 is an external view of an ultrasonic tonometer; FIG. 2 is a schematic diagram showing the inside of a housing; FIG. 3 is a schematic diagram showing the configuration of an irradiation unit; FIG. 4 is a block diagram showing a control system; FIG. 5 is a flowchart showing a measurement operation; FIG. 6 is a diagram showing an example of transformation of the irradiation unit; FIG. 7 is a diagram showing an example of transformation of the irradiation unit.

[0011] Examples of the present disclosure will be described below. The ultrasonic tonometer of this example uses ultrasound to measure the intraocular pressure of a subject's eye in a non-contact manner. The ultrasonic tonometer measures intraocular pressure by optically or acoustically detecting changes in the shape or vibration of the subject's eye when ultrasound is applied to the subject's eye. For example, the ultrasonic tonometer continuously applies pulse waves or burst waves to the cornea and calculates intraocular pressure based on ultrasound output information when the cornea is deformed to a predetermined state (e.g., applanation or flattening). Examples of output information include the sound pressure, acoustic radiation pressure, irradiation time (e.g., the elapsed time since a trigger signal was input), or frequency of the ultrasound. When deforming the cornea of ​​the subject's eye, for example, the sound pressure, acoustic radiation pressure, or acoustic streaming of the ultrasound is used.

[0012] 1 shows the external appearance of the device. The ultrasonic tonometer 1 includes, for example, a base 2, a housing 3, a face support unit 4, a drive unit 5, etc. An irradiation unit 100, an optical system 200, etc., which will be described later, are arranged inside the housing 3. The face support unit 4 supports the face of the subject's eye. The face support unit 4 is installed on, for example, the base 2. The drive unit 5 moves the housing 3 relative to the base 2, for example, for alignment purposes.

[0013] 2 is a schematic diagram of the main components inside the housing 3. For example, an irradiation unit 100 and an optical system 200 are arranged inside the housing 3. The irradiation unit 100 and the optical system 200 will be described in order using FIG. 2.

[0014] <Irradiation Unit> The irradiation unit 100 irradiates, for example, ultrasonic waves onto the subject's eye E. For example, the irradiation unit 100 irradiates the cornea with ultrasonic waves to generate acoustic radiation pressure on the cornea. The acoustic radiation pressure is, for example, a force acting in the direction in which sound waves travel. The ultrasonic tonometer 1 of this embodiment uses, for example, this acoustic radiation pressure to deform the cornea.

[0015] The irradiation unit 100 of this embodiment is a parametric speaker, and multiple (e.g., two or more) ultrasonic elements 110 are arranged therein. The irradiation unit 100 is arranged in a front direction of the subject's eye. The ultrasonic elements 110 generate ultrasonic waves. The ultrasonic elements 110 may be piezoelectric elements (e.g., piezoelectric ceramics), magnetostrictive elements, or the like. The multiple ultrasonic elements 110 are supported by, for example, a support member 101. The support member 101 of this embodiment has a hemispherical (bowl-shaped) shape, and the ultrasonic elements 110 are arranged in a spherical shape by being supported by the support member 101. This causes the sound axes of the ultrasonic elements 110 to intersect at a single point, making it easier to focus the ultrasonic waves. However, the ultrasonic elements do not necessarily have to be arranged in a spherical shape; they may be arranged in an aspherical (curved) shape, such as an ellipsoidal sphere, or may be arranged in a planar shape.

[0016] The support member 101 is provided with an opening 102 through which the optical axis of the optical system 200 passes. In this embodiment, the opening 102 through which the optical axis O1 of the observation system (photography optical system) 220 described later passes is provided in the center of the support member 101. That is, the optical axis O1 of the observation system 220 is disposed in the opening 102. In this manner, by providing the openings 102 through which the optical axis O1 of the observation system 220 passes in the support member 101 that supports each ultrasonic element 110, it is possible to observe the subject's eye while irradiating ultrasonic waves with sufficient output. In this embodiment, holes 103 (first holes) through which the light projection optical axis O3 of the deformation detection system 260 (or the Z alignment detection system 280) passes and holes 104 (second holes) through which the light reception optical axis O4 passes are provided on the left and right sides of the opening 102. Optical members such as transparent plates 102a (or lenses), 103a, and 104a may be disposed in the opening 102 or the holes 103 and 104. This can prevent foreign matter (such as dust) from entering the inside of the device through the opening 102 or the holes 103 and 104.

[0017] The irradiation unit 100 of this embodiment is arranged so that the sound source area is large. In other words, the ultrasonic elements 110 of this embodiment are arranged so that the density of the ultrasonic elements 110 is high. The magnitude of the acoustic radiation pressure (or sound pressure) is determined by the acoustic intensity and spot diameter supplied from the sound source, and in particular, the larger the area of ​​the sound source, the greater the supplied acoustic intensity and the greater the generated acoustic radiation pressure. Therefore, by increasing the arrangement density of the ultrasonic elements 110 as in this embodiment, it is possible to increase the acoustic radiation pressure (or sound pressure) while suppressing the size of the irradiation unit 100.

[0018] 3 is a diagram of the irradiation unit 100 as viewed from the subject side. As shown in Fig. 3, a plurality of installation holes 105 for installing ultrasonic elements 110 are provided in the support member 101 around the opening 102. By installing the ultrasonic elements 110 in the installation holes 105, the ultrasonic elements 110 are arranged so as to surround the opening 102 through which the optical axis O1 of the observation system 220 passes.

[0019] In the irradiation unit 100 of this embodiment, the size of each ultrasonic element 110 is reduced and a large number of ultrasonic elements 110 are arranged, thereby reducing the gap between the ultrasonic elements and increasing the sound source area. The diameter of each ultrasonic element 110 in this embodiment (e.g., the diameter in a direction perpendicular to the sound axis of each ultrasonic element 110) is smaller than the diameter of the opening 102 for the observation system 220 (e.g., the diameter in a direction perpendicular to the optical axis O1). This reduces the gap between the ultrasonic elements when the ultrasonic elements 110 are arranged around the opening 102, thereby increasing the density of the ultrasonic elements 110 in the parametric speaker. For example, the opening 102 of the observation system 220 in this embodiment has a diameter of 20 mm, and the diameter of the ultrasonic elements 110 is 15 mm or less.

[0020] It is preferable that the distance between ultrasonic elements (center-to-center distance) is equal to or less than the wavelength of the ultrasonic waves to be output. This can suppress the occurrence of grating lobes. Grating lobes are unwanted ultrasonic waves that occur when the center-to-center distance between ultrasonic elements exceeds the wavelength of the ultrasonic waves. For example, if the frequency of the output ultrasonic waves is 40 kHz, the wavelength of the ultrasonic waves is 8.5 mm, so it is preferable that the center-to-center distance of each ultrasonic element be 8.5 mm or less.

[0021] In this embodiment, the ultrasonic elements 110 are arranged so as to form a circle when viewed from the direction of the subject's eye. This allows a circular pressure plane to be suitably formed when the cornea of ​​the subject's eye is applanated. For example, when determining the intraocular pressure value based on the diameter of the pressure plane, as with a Goldmann tonometer, forming a circular pressure plane can improve measurement accuracy. Alternatively, the ultrasonic elements 110 may be arranged concentrically.

[0022] As shown in FIG. 3 , the ultrasonic elements 110 may be arranged so that the sound source areas (the total areas of the irradiation surfaces 110a of the ultrasonic elements 110) are symmetrical (the same) in the upper and lower regions when the support member 101 is divided by a horizontal plane H including the optical axis O1, or so that the sound source areas are symmetrical (the same) in the left and right regions when the support member 101 is divided by a vertical plane V including the optical axis O1. This makes it possible to prevent the sound axis L1 of the ultrasonic waves from being deflected with respect to the optical axis O1. Furthermore, by arranging the sound source areas symmetrically, it is possible to prevent differences in measurement conditions between the right eye and the left eye. Of course, the ultrasonic elements 110 may be arranged so as to be plane-symmetrical (vertically symmetrical) with respect to the horizontal plane H, or so as to be plane-symmetrical (left-right symmetrical) with respect to the vertical plane V. The sound axis is, for example, the central axis of the ultrasonic waves irradiated by the irradiation unit 100. The acoustic axis extends, for example, in the propagation direction of the ultrasonic waves or in the vibration direction of the irradiation unit 100, and passes through the focal position where the ultrasonic waves output by the irradiation unit 100 are focused.

[0023] 3, the ultrasonic elements 110 may be arranged such that the heights of adjacent ultrasonic elements 110 in the left-right direction are different. In other words, by making the heights of the ultrasonic elements 110 different between any row of ultrasonic elements 110 and the adjacent row, the spacing between vertical rows of ultrasonic elements 110 can be narrowed. This makes it possible to reduce wasted space compared to when the ultrasonic elements 110 are arranged in a grid pattern at regular intervals in the vertical and horizontal directions, for example.

[0024] The ultrasonic elements 110 of this embodiment are arranged in a manner as described in Fig. 3, which increases the arrangement density and increases the sound source area. Therefore, the acoustic radiation pressure (or sound pressure) can be increased while suppressing the size of the irradiation unit 100. However, the arrangement of the ultrasonic elements 110 does not necessarily have to be the same as that shown in Fig. 3. For example, the arrangement density can be improved by incorporating at least one of the elements such as the size, spacing, arrangement shape, symmetry, and height of each ultrasonic element 110 into the arrangement.

[0025] The optical system 200 performs, for example, observation or measurement of the subject's eye (see FIG. 2 ). The optical system 200 includes, for example, an objective system 210, an observation system 220, a fixation target projection system 230, a deformation detection system 260, a dichroic mirror 201, and a beam splitter 204.

[0026] The objective system 210 is, for example, an optical system for taking in light from outside the housing 3 into the optical system 200 or for irradiating light from the optical system 200 to the outside of the housing 3. The objective system 210 includes, for example, optical elements. The objective system 210 may include optical elements such as an objective lens and a relay lens.

[0027] The illumination system 240 illuminates the subject's eye. The illumination system 240 illuminates the subject's eye with, for example, infrared light. The illumination system 240 includes, for example, an illumination light source 241. The illumination light source 241 is disposed, for example, diagonally in front of the subject's eye. The illumination light source 241 emits, for example, infrared light. The illumination system 240 may include a plurality of illumination light sources 241.

[0028] The observation system 220, for example, captures an observation image of the subject's eye. The observation system 220, for example, captures an image of the anterior segment of the subject's eye. The observation system 220 includes, for example, a light-receiving lens 221, a light-receiving element 222, and the like. The observation system 220, for example, receives light from the illumination light source 241 reflected by the subject's eye. The observation system 220, for example, receives a light beam reflected from the subject's eye centered on the optical axis O1. For example, the reflected light from the subject's eye passes through the opening 102 of the irradiation unit 100, passes through the objective system 210 and the light-receiving lens 221, and is received by the light-receiving element 222. The corneal reflection bright spot of the illumination light source 241 received by the light-receiving element 222 is used, for example, for alignment in the up / down and left / right directions (XY alignment). In this case, for example, the illumination system 240 and the observation system 220 function as an XY alignment detection unit. Of course, an index projection system that projects an index for XY alignment from the optical axis O1 onto the subject's eye may be provided in addition to the illumination system 240. In this case, the central corneal bright spot is captured in the observation image of the observation system 220, and XY alignment may be performed based on this central corneal bright spot.

[0029] The fixation target projection system 230 projects a fixation target onto the subject's eye, for example. The fixation target projection system 230 includes, for example, a target light source 231, an aperture 232, a projection lens 233, an aperture 234, etc. Light from the target light source 231 passes through the aperture 232, the projection lens 233, the aperture 232, etc. along an optical axis O2 and is reflected by the dichroic mirror 201. The dichroic mirror 201, for example, makes the optical axis O2 of the fixation 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 through the objective system 210 along the optical axis O1 and is irradiated onto the subject's eye. When the subject fixates on the target of the fixation target projection system 230, the subject's line of sight is stabilized.

[0030] The deformation detection system 260 detects, for example, deformation of the cornea of ​​the subject's eye. The deformation detection system 260 includes, for example, a light source 261, a projector lens 262, an aperture 263, a light-receiving lens 264, an aperture 265, and a light-receiving element 266. Light from the light source 261 passes through the projector lens 262 and the aperture 263 along the optical axis O3, for example, and is irradiated onto the subject's eye. The light reflected by the subject's eye is then reflected by the beam splitter 204 along the optical axis O4, passes through the light-receiving lens 264 and the aperture 265, and is received by the light-receiving element 266. The deformation detection system 260 may detect the deformation of the cornea based on, for example, the corneal reflected light received by the light-receiving element 266.

[0031] The deformation detection system 260 may detect the deformation state of the cornea based on, for example, the magnitude of the light-receiving signal of the light-receiving element 266. For example, the deformation detection system 260 may detect that the cornea has entered an applanation state when the amount of light received by the light-receiving element 266 reaches a maximum. In this case, for example, the deformation detection system 260 is set so that the amount of light received reaches a maximum when the cornea of ​​the subject's eye enters an applanation state.

[0032] The deformation detection system 260 may be an anterior segment cross-sectional image capturing unit such as an OCT or Scheimpflug camera, etc. For example, the deformation detection system 260 may detect the amount or speed of deformation of the cornea.

[0033] The Z alignment detection system 280 detects, for example, the alignment state in the Z direction. The Z alignment detection system 280 includes, for example, a light-receiving lens 281 and a light-receiving element 282. The Z alignment detection system 280 may detect the alignment state in the Z direction, for example, by detecting reflected light from the cornea. For example, the Z alignment detection system may receive light reflected from the cornea of ​​the subject's eye when light from the light source 261 is reflected. In this case, the Z alignment detection system 280 may receive, for example, a bright spot formed when light from the light source 261 is reflected by the cornea of ​​the subject's eye. In this way, the light source 261 may also be used as a light source for Z alignment detection.

[0034] For example, light from the light source 261 reflected by the cornea passes through the beam splitter 204 and the light-receiving lens 281 along the optical axis O4 and is received by the light-receiving element 282. When the eye to be examined and the Z-alignment detection system 280 are misaligned in the Z direction, the reception position of the light from the light source 261 reflected by the cornea (e.g., the position where the intensity of the received light signal is maximum) shifts on the light-receiving element 282. Therefore, the Z-alignment detection system 280 may detect the alignment state based on the reception position of the light from the light source 261 on the light-receiving element 282. For example, the Z-alignment detection system 280 may detect the alignment state by detecting whether the reception position of the light from the light source 261 is at a predetermined pixel (detection reference position) of the light-receiving element 282, or by detecting how many pixels it is shifted from the predetermined pixel.

[0035] <Controller> Next, the configuration of the control system will be described with reference to FIG. 4 . The controller 70, for example, controls the entire device and performs calculation processing of measurement values. The controller 70 is realized, for example, by a general CPU (Central Processing Unit) 71, ROM 72, RAM 73, etc. The ROM 72 stores various programs for controlling the operation of the ultrasonic tonometer 1, initial values, etc. The RAM 73 temporarily stores various information. The controller 70 may be configured with one controller or multiple controllers (i.e., multiple processors). The controller 70 may be connected to, for example, the driver 5, the memory 74, the display 75, the operation unit 76, the irradiation unit 100, the optical system 200, etc.

[0036] The storage unit 74 is a non-transitory storage medium that can retain its contents even when the power supply is cut off. For example, a hard disk drive, a flash ROM, a removable USB memory, etc. can be used as the storage unit 74.

[0037] The display unit 75 displays, for example, the measurement results of the subject's eye. The display unit 75 may have a touch panel function.

[0038] The operation unit 76 accepts various operation instructions from the examiner. The operation unit 76 outputs an operation signal according to the input operation instruction to the control unit 70. The operation unit 76 may be, for example, at least one user interface such as a touch panel, a mouse, a joystick, or a keyboard. Note that if the display unit 75 is a touch panel, the display unit 75 may function as the operation unit 76.

[0039] <Control Operation> The control operation when measuring intraocular pressure in the ultrasonic tonometer having the above-described configuration will be described with reference to FIG.

[0040] (Step S1: Alignment) First, the control unit 70 performs alignment with the subject's eye, whose face is supported by the face support unit 4. For example, the control unit 70 detects a bright spot by the target projection system 250 from an anterior eye front image acquired by the light receiving element 222, and drives the drive unit 5 so that the position of the bright spot is at a predetermined position. Of course, the examiner may manually perform alignment with the subject's eye using the operation unit 76 or the like while looking at the display unit 75. After driving the drive unit 5, the control unit 70 determines whether the alignment is appropriate based on whether the position of the bright spot in the anterior eye image is at a predetermined position.

[0041] (Step S2: Ultrasound irradiation) The control unit 70 generates ultrasound by applying a voltage to the ultrasound element 110. The ultrasound output from the irradiation unit 100 is irradiated onto the subject's eye, and the acoustic radiation pressure of this ultrasound deforms the cornea of ​​the subject's eye.

[0042] (Step S3: Deformation Detection) The control unit 70 detects the deformation state of the cornea using the deformation detection system 260. For example, the control unit 70 detects that the cornea has been deformed into a predetermined state (applanation state or flattened state) based on the light receiving signal of the light receiving element 266.

[0043] (Step S4: Calculation of Intraocular Pressure) The control unit 70 calculates the intraocular pressure of the subject's eye based on, for example, the acoustic radiation pressure (or sound pressure) when the cornea of ​​the subject's eye is deformed to a predetermined state. The acoustic radiation pressure (or sound pressure) applied to the subject's eye is correlated with the ultrasound irradiation time, and increases as the ultrasound irradiation time becomes longer. Therefore, the control unit 70 determines the acoustic radiation pressure (or sound pressure) when the cornea is deformed to a predetermined state based on the ultrasound irradiation time. The relationship between the acoustic radiation pressure (or sound pressure) when the cornea is deformed to a predetermined state and the intraocular pressure of the subject's eye is determined in advance by experiments or the like and stored in the memory unit 74 or the like. The control unit 70 determines the intraocular pressure of the subject's eye based on the acoustic radiation pressure (or sound pressure) when the cornea is deformed to a predetermined state and the relationship stored in the memory unit 74. In this way, the control unit 70 functions as a calculation means for calculating the intraocular pressure.

[0044] Of course, the method for calculating the intraocular pressure is not limited to the above, and various other methods may be used. For example, the control unit 70 may calculate the intraocular pressure by determining the amount of corneal deformation using the deformation detection system 260 and multiplying the amount of deformation by a conversion coefficient. Alternatively, the control unit 70 may measure the intraocular pressure based on ultrasound reflected by the subject's eye. For example, the control unit 70 may measure the intraocular pressure based on a change in the characteristics of the ultrasound reflected by the subject's eye, or may obtain the amount of corneal deformation from the ultrasound reflected by the subject's eye and measure the intraocular pressure based on the amount of deformation.

[0045] As described above, even when the ultrasonic tonometer 1 of this embodiment uses a parametric speaker for the irradiation unit 100, by passing the optical axis O1 of the observation system 220 through the parametric speaker, the irradiation unit 100 can be appropriately positioned with respect to the test eye, and the test eye can be observed while being irradiated with ultrasound of sufficient output.

[0046] Furthermore, by increasing the arrangement density of the ultrasonic elements 110 as in the above embodiment, it is possible to generate the acoustic radiation pressure (or sound pressure) required for intraocular pressure measurement while keeping the size of the irradiation unit 100 small.

[0047] The number and arrangement of the openings (or holes) are not limited to those in this embodiment. For example, the support member 101 may be provided with only the central opening 102. In this case, for example, the deformation detection system 260 and the Z-alignment detection system 280 may be disposed in front of the subject's eye, and a common optical axis O1 of the observation system 220, the deformation detection system 260, and the Z-alignment detection system 280 may pass through a single opening 102. Furthermore, in addition to the central opening 102 and the three holes 103 and 104 on either side thereof, the support member 101 may be provided with holes for an anterior eye illumination light source or an alignment bright spot light source.

[0048] The size of each ultrasonic element 110 may be changed to suit the arrangement. For example, as shown in FIG. 6, small ultrasonic elements 110b may be arranged in the gaps between adjacent ultrasonic elements 110. This reduces wasted space and increases the sound source area. The shape of each ultrasonic element 110 (or a case that houses each ultrasonic element) may also be changed to suit the arrangement. For example, as shown in FIG. 7, the ultrasonic elements 110 may be fan-shaped and arranged to surround the opening 102. In this way, changing the shape of the ultrasonic elements 110 also reduces wasted space in the irradiation unit 100.

[0049] REFERENCE SIGNS LIST 1 ultrasonic tonometer 2 base 3 housing 4 face support unit 5 driving unit 6 support base 100 irradiation unit 101 support member 102 opening 103 hole 104 hole 105 installation hole 200 optical system

Claims

1. An ultrasonic tonometer for measuring intraocular pressure of a subject's eye using ultrasound, an imaging optical system for imaging the subject's eye; an irradiation means having a plurality of ultrasonic elements and a support member that supports the ultrasonic elements, and that irradiates the subject's eye with ultrasonic waves; An ultrasonic tonometer, wherein the support member has an opening for passing an optical axis of the photographing optical system.

2. 2. The ultrasonic tonometer according to claim 1, wherein the diameter of the ultrasonic element is smaller than the diameter of the opening.

3. a second optical system different from the imaging optical system; a light-projecting system and a light-receiving system of the second optical system are disposed obliquely with respect to the optical axis of the photographing optical system, 3. The ultrasonic tonometer according to claim 1, wherein a first hole for passing a light projection optical axis of the second optical system and a second hole for passing a light receiving optical axis of the second optical system are provided in the support member separately from the opening.

4. 3. The ultrasonic tonometer according to claim 1, wherein the center-to-center distance of the plurality of ultrasonic elements is equal to or less than the wavelength of the ultrasonic waves irradiated onto the subject's eye.

5. 3. The ultrasonic tonometer according to claim 1, wherein the plurality of ultrasonic elements are arranged so that the sound source areas are symmetrical in left and right regions when the support member is divided by a vertical plane including the optical axis, and / or in top and bottom regions when the support member is divided by a horizontal plane including the optical axis.

6. a deformation detection means for detecting whether the cornea of ​​the subject's eye has been deformed to a predetermined state by the ultrasonic waves from the irradiation means; 3. The ultrasonic tonometer according to claim 1, further comprising a calculation unit that calculates the intraocular pressure of the subject's eye based on the ultrasonic output of the irradiation unit when the cornea is deformed to a predetermined state.