JP2011045602A - Non-contact ultrasonic tonometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the intraocular pressure of a subject's eye and to suitably confirm the condition of the eye examined. <P>SOLUTION: This non-contact ultrasonic tonometer includes an ultrasonic probe having a transmitting/receiving part for transmitting/receiving ultrasonic beams to the cornea of the subject's eye in a non-contact manner, and an observation optical system having an observation optical axis for observing the front eye part image of the subject's eye and arranged separately from the probe so that the center axis of the probe and the observation optical axis intersect at a predetermined angle. The intraocular pressure of the subject's eye is measured based on characteristics of cornea reflected waves received by the probe. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 an apparatus for measuring intraocular pressure of a subject's eye in comparison with an incident wave incident on the subject's eye and a reflected wave from the subject's eye, a vibrator that injects vibration into the subject's eye The probe has a probe having a vibration detection sensor for detecting a reflected wave from the subject's eye, and has a probe pen having an elastic cap that is in contact with the eyeball at the tip, and the elastic cap is attached to the subject's eye. A contact-type tonometry apparatus that measures the intraocular pressure of a subject's eye in a contacted state has been proposed (see Patent Document 1).

  Further, as a non-contact type configuration, a probe having a transducer for applying ultrasonic waves to a subject's eye (however, a model eye) and a vibration detection sensor for detecting a reflected wave from the subject's eye. There has been proposed an intraocular pressure inspection device that measures the intraocular pressure of a subject's eye in a non-contact manner in a state where a child is provided and a probe is placed in front of the subject's eye (see Patent Document 2). .

JP 2004-267299 A International Publication No. 2008/072527

  However, in the case of the configuration of Patent Document 1, the intraocular pressure measurement is performed in a state where the probe pen is in contact with the subject's eye, and the burden on the subject's eye is large. Moreover, in the case of the structure of patent document 2, it is only what assumed the measurement with respect to a model eye, and is still inadequate for measuring an actual human eye, and there are many problems for practical use. For example, in the case of a human eye, the eye moves due to microscopic eye movement or movement of the eye of the subject's eye. There is a possibility that characteristics (for example, frequency, phase, etc.) will change, resulting in variations in measurement results. Further, in order to alleviate the fear of the subject, it is necessary to secure a certain working distance between the cornea and the device (for example, about 10 mm).

  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 the intraocular pressure of the subject's eye and can suitably check the state of the subject's eye.

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

(1)
An ultrasonic probe having a transmission / reception unit for transmitting and receiving an ultrasonic beam to a subject's eye cornea in a non-contact manner;
It has an observation optical axis for observing the anterior segment image of the subject's eye, and is separated from the probe so that the central axis of the probe and the observation optical axis intersect at a predetermined angle And an observation optical system arranged
The intraocular pressure of the subject's eye is measured based on the characteristics of the corneal reflected wave received by the probe.
(2) In the non-contact ultrasonic tonometer of (1),
The probe is disposed to face the subject's eye,
The observation optical system is arranged obliquely forward with respect to the subject's eye.
(3) In the non-contact ultrasonic tonometer of (2),
An opening is formed at the center of the probe.
(4) In the non-contact ultrasonic tonometer of (3),
The probe has an alignment optical axis for detecting the alignment state of the probe with respect to the subject's eye, and the probe has a central axis intersecting the alignment optical axis at a predetermined angle with respect to the probe. It has an alignment detection optical system arranged separately,
The alignment detection optical system is characterized by being shared by an observation optical system or arranged separately from the observation optical system.
(5) In the non-contact ultrasonic tonometer of (4),
The probe is arranged so that its central axis is parallel to the horizontal plane,
The observation optical system is arranged below the probe.
(6) In the non-contact ultrasonic tonometer of (5),
The transmitter / receiver of the probe is configured such that a transmitter and a receiver are separated and the opening, the receiver, and the transmitter are concentrically formed in order from the center. And
(7) In the non-contact ultrasonic tonometer of (6),
A first alignment index projection optical system that is disposed outside the outer edge of the probe and projects an alignment index for aligning the probe in the vertical and horizontal directions with respect to the subject's eye; Features.
(8) In the non-contact ultrasonic tonometer of (7),
The first alignment index projection optical system is arranged such that a central axis thereof is coaxial with an observation optical axis of the observation optical system.
(9) In the non-contact ultrasonic tonometer of (8),
A second alignment index projection optical system that projects an alignment index for performing alignment in the working distance direction of the probe with respect to the subject's eye from an oblique direction;
A working distance detection optical system that detects corneal reflected light from the second alignment index projection optical system from an oblique direction;
The second alignment index projection optical system and the working distance detection optical system are arranged symmetrically with respect to the center axis of the probe.
(10) In the non-contact ultrasonic tonometer according to any one of (1) to (9), at least one of the transmission / reception units is a broadband air-coupled probe.
(11) In the non-contact ultrasonic tonometer of (10), the probe has a fixation optical axis for projecting a fixation target onto the subject's eye through the opening, and the central axis of the probe And a fixation target projection optical system arranged so that the optical axis is coaxial with the optical axis.
(12) In the non-contact ultrasonic tonometer of (6),
The alignment detection optical system is arranged in two directions obliquely forward with respect to the subject's eye.

  According to the present invention, it is possible to accurately measure the intraocular pressure of the subject's eye and to suitably check the state of the subject's eye.

  FIG. 1 is a schematic configuration diagram of a measurement system and an optical system of a non-contact ultrasonic tonometer according to the present embodiment. The following measurement system and optical system are built in a housing (not shown). Further, the housing may be moved three-dimensionally with respect to the subject's eye E by a known alignment moving mechanism. Moreover, a hand-held type (handy type) may be used.

  The ultrasonic probe 10 emits an ultrasonic beam (pulse wave or continuous wave) toward the cornea Ec of the subject's eye E using air as a medium, and detects the ultrasonic beam reflected by the cornea Ec. To do. The probe 10 includes, as an ultrasonic transmission / reception unit 11, a transmission unit 12 that emits ultrasonic waves (incident waves) that are incident on the cornea Ec, and a reception unit that detects ultrasonic waves (reflected waves) reflected by the cornea Ec. 13 and is used to measure the intraocular pressure of the subject's eye E in a non-contact manner. In the probe 10, the transmission unit 12 and the reception unit 13 are separated from each other. Of course, the transmission unit 12 and the reception unit 13 may be used in a single configuration.

  The transmission unit 12 and the reception unit 13 in the transmission / reception unit 11 are disposed to face the subject's eye at a predetermined working distance, and are disposed at a position where ultrasonic waves can be transmitted / received from the substantially front direction with respect to the subject's eye. (See FIG. 1). More preferably, the transmission unit 12 and the reception unit 13 are arranged in the vicinity of the subject eye E. In the present embodiment, the probe 10 is arranged so that the central axis C1 of the probe 10 is parallel to the horizontal plane.

FIG. 2 is a schematic configuration diagram when the probe 10 according to the present embodiment is viewed from the front. The probe 10 has an opening 18 (for example, a circular hole having a diameter of about 1 mm) at the center (on the central axis C1), a ring-shaped receiving unit 13 outside the opening 18, and the receiving unit 13 The ring-shaped transmission unit 12 is provided on the outer side. The opening 18 is formed in the probe 10 in order to pass a fixation light beam emitted from a fixation light source 32 (described later). More specifically, the opening 18, the receiver 13, and the transmitter 12 are formed concentrically in order from the center, whereby ultrasonic waves are transmitted from the outside toward the cornea Ec by the transmitter 12. The corneal reflection wave is received inside by the receiving unit 13. Note that the positional relationship between the transmission unit 12 and the reception unit 13 may be reversed.

In addition, an air-coupled ultrasonic transmission / reception unit (ultrasonic probe) that transmits and receives an ultrasonic beam having a broadband frequency component is used for the transmission / reception unit 11 in order to increase propagation efficiency in the air. Is preferred. In this case, a Microacoustic BAT ^™ probe can be used. For details of such a probe, refer to US Pat. No. 5,287,331, JP 2005-506783 A and the like. Of course, the present invention is not limited to this, and a piezoelectric ultrasonic transmission / reception unit (ultrasonic probe) may be used. One transmitter / receiver may be a broadband air-coupled probe, and the other transmitter / receiver may be a piezo-type probe.

  Returning to the description of FIG. The optical system of the present apparatus includes an observation optical system 20 for observing the anterior segment of the subject's eye E from an oblique direction, and a fixation target projection for fixing the subject's eye E from the front direction ( Presentation) Optical system 30, first index projection optical system 40 for projecting a first index for detecting the alignment state in the vertical and horizontal directions onto the cornea Ec, and a first index for detecting the alignment state in the working distance direction which is the front-rear direction. A second index projection optical system 50 for projecting two indices onto the cornea Ec and an index detection optical system 55 for detecting the second index projected onto the cornea Ec are provided.

  The observation optical system 20 includes an objective lens 23 and a two-dimensional image sensor 26, and the optical axis (observation optical axis) L <b> 1 is the central axis C <b> 1 of the probe 10 on the eye side of the probe 10. Are arranged so as to intersect at a predetermined angle. The observation optical system 20 is disposed outside the outer edge portion of the probe 10 (for example, below the probe 10). The anterior ocular segment image illuminated by the anterior ocular segment illumination light source (for example, the first index projection optical system 40) is imaged on the image sensor 26 by the objective lens 23. The anterior segment image captured by the image sensor 26 is displayed on a monitor 72 described later.

  The observation optical system 20 can be used as an alignment detection optical system that detects a ring index image R, which will be described later, and detects the alignment state of the probe 10 with respect to the subject's eye. The detection result from the image sensor 26 can be used for alignment error determination, automatic alignment of the probe 10 with respect to the subject's eye, and the like.

  The fixation target projection optical system 30 has a visible light source 32 and projects a fixation target for fixing the subject eye E onto the subject eye E. Visible light from the light source 32 has its beam diameter reduced by the aperture stop, reflected by the total reflection mirror 36, and projected onto the fundus of the subject's eye E through the opening 18. The optical axis L2 of the fixation target projection optical system 30 is coaxial with the central axis C1 of the probe 10 by the mirror 36. Thereby, the probe 10 will be in the state arrange | positioned in the gaze direction of a subject's eye.

  The first index projection optical system 40 is disposed outside the outer edge portion of the probe 10, has an infrared light source 42, and projects infrared light as a first alignment index onto the cornea Ec from an oblique direction. More specifically, the infrared light source 42 is a substantially ring-shaped light source, and is arranged so that its central axis is coaxial with the observation optical axis L1. As a result, a ring index image R is formed on the cornea Ec (see FIG. 3). The light source 42 also serves as an anterior ocular segment illumination light source.

  The ring index image R formed on the cornea Ec is imaged on the image sensor 26 by the objective lens 23 together with the anterior segment image. Then, the ring index image R detected by the image sensor 26 is displayed on the monitor 72 (see the ring R in FIG. 3). In this case, the position where the ring center of the index image R coincides with the observation optical axis L1 is the alignment completion position.

  Note that the projection optical system 40 may be arranged so that its projection optical axis (center axis) is coaxial with the observation optical axis L1. For example, an optical path branching mirror such as a half mirror is disposed in the optical path of the observation optical system 20, and light from the light source 42 is projected onto the subject's eye via the optical path branching mirror.

  The second index projection optical system 50 includes an infrared light source 51 and projects infrared light as a second alignment index onto the cornea Ec from an oblique direction. The index detection optical system 55 includes a position detection element (for example, a line CCD) 58 and detects a second index image formed on the cornea Ec by the second index projection optical system 50 (light source reflected by the cornea Ec). Infrared light from 51 is received). The optical axis L4 of the projection optical system 50 and the optical axis L5 of the index detection optical system 55 have an axis that is symmetric with respect to the central axis of the probe 10, and the optical axis L5 is on the optical axis L4 and the central axis C1. Cross at. Thereby, the working distance between the subject's eye and the probe 10 is detected with high accuracy. In FIG. 1, the projection optical system 50 and the detection optical system 55 are arranged in the vertical direction for convenience of explanation, but are actually arranged in the horizontal direction.

  The alignment state in the working distance direction may be detected by the probe 10 (for example, the time until the ultrasonic wave emitted to the subject's eye returns to the probe 10 is the distance. Converted).

  FIG. 3 is a schematic block diagram of a control system of the apparatus according to the present embodiment. The arithmetic control unit 70 controls the entire apparatus. The transmission / reception unit 11 is connected to the control unit 70, and a drive signal from the control unit 70 is input to the transmission unit 12. The electric signal output from the receiving unit 13 is amplified and then input to the control unit 70. Then, the control unit 70 analyzes the output waveform of the reflected wave detected by the receiving unit 13 and calculates an intraocular pressure value. Further, the image pickup device 26, the light source 32, the light source 42, the light source 51, the position detection element 58, the monitor 72, the memory 75, and the like are connected to the arithmetic control unit 70. The memory 75 stores a measurement program for measuring intraocular pressure using the probe 10, a control program for controlling the entire apparatus, and the like.

  A case where the intraocular pressure of the subject eye E is measured in the apparatus having the above configuration will be described. First, the examiner causes the subject to gaze at the fixation target (light source 32). In addition, the probe 10 is aligned with the subject eye E while observing the anterior segment image displayed on the monitor 72. At this time, as shown in FIG. 3, the arithmetic control unit 70 displays on the monitor 72 an anterior ocular segment image including the ring index image R imaged by the image sensor 26 and a later-described reticle LT and indicator G. The arithmetic control unit 70 detects the alignment state in the working distance direction based on the output signal from the position detection element 58, and controls the display of the indicator G based on the detection result.

  The examiner performs vertical and horizontal alignment so that the ring index image R and the reticle LR are concentric. Further, alignment in the working distance direction is performed so that the indicator G is in an appropriate display state (for example, a single indicator).

  When alignment in the up / down / left / right / front / rear direction is completed and a predetermined trigger signal is input manually or automatically, the calculation control unit 70 emits an ultrasonic beam from the transmission unit 12 toward the cornea Ec, and the cornea Ec. The receiving unit 13 detects the ultrasonic beam reflected by. Then, the arithmetic control unit 70 obtains the intraocular pressure of the subject's eye E based on the detection result by the transmission / reception unit 11 and displays the result on the monitor 72.

  When an ultrasonic beam having a predetermined waveform is irradiated from the transmitter 12 to the cornea Ec, the characteristic / waveform (amplitude, phase, etc. of the reflected wave) of the corneal reflected wave by the ultrasonic beam depends on the intraocular pressure of the subject. Change. Therefore, the control unit 70 determines the intraocular pressure of the subject's eye from the relationship between the characteristic and waveform of the reflected wave detected by the receiving unit 13 (for example, a predetermined physical quantity such as the amplitude and phase of ultrasonic waves) and the intraocular pressure. Calculate the value.

  For example, the control unit 70 performs frequency analysis (for example, Fourier analysis) on the acoustic intensity of the detected reflected wave, and acquires an amplitude spectrum that is an amplitude level for each frequency in the reflected wave. FIG. 4 is an example of the amplitude spectrum of the reflected wave.

  Here, the control unit 70 detects the peak amplitude level of the obtained amplitude spectrum (for example, the peak value P of the amplitude spectrum S in FIG. 4). And the control part 70 calculates intraocular pressure based on the peak amplitude level of an amplitude spectrum. The memory 75 stores a correlation between the peak amplitude level and the intraocular pressure value as a table, and the control unit 70 obtains the intraocular pressure value corresponding to the detected peak amplitude level from the memory 75 and obtains it. The intraocular pressure value is displayed on the monitor 72. The correlation between the peak amplitude level and the intraocular pressure value can be set, for example, by obtaining in advance the correlation between the peak amplitude level acquired by this device and the intraocular pressure value obtained by the Goldman tonometer. It is.

  As described above, the probe 10 and the observation optical system (alignment detection optical system) 20 are arranged separately and independently, so that the probe 10 and the observation optical system 20 do not interfere with each other, and the probe 10 An optical system that is not restricted by can be easily configured, and sufficient observation and alignment can be performed.

  Further, according to the above configuration, since the probe 10 is disposed at a position facing the subject's eye, ultrasonic waves can be efficiently transmitted / received to / from the subject's eye. Can be measured with high accuracy. Furthermore, since the transmission unit 12 is arranged outside, a wide area of the transmission unit 12 can be ensured, and a strong ultrasonic beam can be applied to the cornea Ec. Further, since the receiving unit 13 is arranged at the center, the receiving unit 13 is arranged to face the corneal apex, and the reflected wave from the vicinity of the corneal apex can be detected efficiently.

  In addition, according to the above configuration, the probe 10 is disposed in front of the subject's eye and the observation optical system 20 is disposed obliquely in front of the subject's eye. The pressure can be measured with high accuracy and sufficient observation and alignment can be performed by the observation optical system 20.

  Further, according to the above configuration, the central axis of the probe 10 is arranged in parallel to the horizontal plane, and the observation optical system 20 is arranged below the probe 10, so that Since the ultrasonic wave and the anterior ocular segment image are less likely to be vignetted due to wrinkles or the like, intraocular pressure measurement and anterior ocular segment observation can be performed smoothly.

  The observation optical system 20 is not limited to the above configuration, and may be arranged separately from the probe so that the center axis C1 of the probe 10 and the observation optical axis L1 intersect at a predetermined angle. That's fine. For example, the configuration in which the observation optical system 20 is disposed at the center and the probe 10 is disposed obliquely in front of the subject's eye may be employed. Further, the probe 10 and the observation optical system 20 may be arranged such that the central axis C1 and the observation optical axis L1 intersect at a predetermined angle with respect to the optical axis of the fixation optical system 30. .

  In the above configuration, the observation optical system 20 is also used as the alignment detection optical system. However, the alignment detection optical system may be arranged separately from the observation optical system.

  Further, the transmission unit 12 and the reception unit 13 may be configured by two or more rings. The transmission unit 12 and the reception unit 13 may be intermittent circles instead of continuous circles. In addition, the shape of the transmission / reception unit 11 is preferably substantially annular, but various modifications are possible. For example, it may be polygonal (a larger number of sides is preferred).

  Further, the present invention is not limited to the above configuration, and the position of the reticle LT is set based on the state where the probe 10 and the subject's eye are in a predetermined positional relationship, or alignment detection is performed. Various transformations are possible. For example, a configuration in which the central axis of the projection optical system 40 and the central axis of the probe 10 are arranged coaxially and the cornea reflection image is detected by the observation optical system 20 may be employed.

  FIG. 5 is an upper schematic view of the measurement system and the optical system of the apparatus according to the modified example of the present invention as viewed from above. In addition, about what attached | subjected the number same as FIG. 1, it shall have the same function and structure unless there is particular description.

  Objective lenses 23a and 23b and imaging elements 26a and 26b are disposed in two directions obliquely forward of the subject's eye E, and the first observation optical system 20a and the second observation optical system 20b are formed by these optical members. The The anterior segment image illuminated by the anterior segment illumination light source 44 is captured by the imaging elements 26a and 26b via the objective lenses 23a and 23b. Imaging signals from the imaging elements 26 a and 26 b are input to the control unit 70 and output to the monitor 72. Note that the first observation optical system 20a and the second observation optical system 20b also serve as alignment detection optical systems.

  The projection optical system 45 that projects the alignment index onto the cornea Ec has an infrared light source 46 and is disposed behind the probe 10. The light beam emitted from the light source 46 is projected onto the cornea Ec through the half mirror 44 and the opening 18. Then, the index image formed on the cornea Ec is picked up by the image pickup devices 26a and 26b.

  FIG. 6 is an example showing a display screen in the apparatus according to the modified example of the present invention. The index image I1 and the index image I2 are index images formed on the cornea Ec by the projection optical system 45. The control unit 70 controls the monitor 72 to synthesize and display the imaging signals from the imaging elements 26a and 26b. The anterior segment image A1 and the index image I1 are based on the imaging signal from the imaging element 26a. Further, in order to improve the observability, only the index image I2 is extracted from the image pickup signal from the image pickup device 26b by image processing, and the anterior segment image is removed. Therefore, only the index image I2 is displayed on the monitor 72.

  In this case, first, alignment in the vertical and horizontal directions is performed so that the center position of the index image I1 and the index image I2 matches the reticle LT (see FIG. 6A). After that, alignment in the working distance direction is performed so that the index image I1 and the index image I2 overlap on the reticle LT. The indicator G can also be used for precise alignment in the working distance direction. In this way, alignment with respect to the eye to be examined can be performed smoothly.

  In the modification example, the control unit 70 may detect the center position between the index image I1 and the index image I2, and electronically display the alignment index corresponding to the detected center position.

  In the above description, the intraocular pressure is calculated based on the amplitude spectrum. However, the intraocular pressure may be calculated based on the phase spectrum when the corneal reflection wave is subjected to frequency analysis. More specifically, the spectral distribution of the incident wave and the reflected wave is obtained, and the intraocular pressure value is calculated based on the phase difference between the phase of the incident wave and the phase of the reflected wave at a predetermined frequency. For the hardness detection method using the ultrasonic pulse method described above, refer to Japanese Patent Application Laid-Open No. 2002-272743.

It is a schematic block diagram of the measurement system and optical system of the non-contact ultrasonic tonometer according to the present embodiment. It is a schematic block diagram when the probe concerning this embodiment is seen from the front. It is a schematic block diagram of the control system of the apparatus which concerns on this embodiment. It is an example of the amplitude spectrum of a reflected wave. It is an upper schematic diagram when the measurement system and the optical system of the apparatus according to the modified example of the present invention are viewed from above. It is a figure which shows the display screen in the apparatus which concerns on the example of a change of this invention.

DESCRIPTION OF SYMBOLS 10 Probe 11 Transmission / reception part 12 Transmission part 13 Reception part 18 Aperture 20 Observation optical system (alignment detection optical system)
30 fixation target projection optical system 40 first index projection optical system 50 second index projection optical system L1 observation optical axis

Claims (12)

An ultrasonic probe having a transmission / reception unit for transmitting and receiving an ultrasonic beam to a subject's eye cornea in a non-contact manner;
It has an observation optical axis for observing the anterior segment image of the subject's eye, and is separated from the probe so that the central axis of the probe and the observation optical axis intersect at a predetermined angle And an observation optical system arranged
A non-contact ultrasonic tonometer that measures an intraocular pressure of a subject's eye based on a characteristic of a corneal reflected wave received by the probe. The non-contact ultrasonic tonometer according to claim 1,
The probe is disposed to face the subject's eye,
The non-contact ultrasonic tonometer is characterized in that the observation optical system is disposed obliquely forward with respect to the subject's eye. The non-contact ultrasonic tonometer according to claim 2,
A non-contact ultrasonic tonometer characterized in that an opening is formed in the center of the probe. The non-contact ultrasonic tonometer according to claim 3,
The probe has an alignment optical axis for detecting the alignment state of the probe with respect to the subject's eye, and the probe has a central axis intersecting the alignment optical axis at a predetermined angle with respect to the probe. It has an alignment detection optical system arranged separately,
The non-contact type ultrasonic tonometer is characterized in that the alignment detection optical system is shared by the observation optical system or is arranged separately from the observation optical system. The non-contact ultrasonic tonometer according to claim 4,
The probe is arranged so that its central axis is parallel to the horizontal plane,
The non-contact type ultrasonic tonometer is characterized in that the observation optical system is disposed below the probe. The non-contact ultrasonic tonometer according to claim 5,
The transmitter / receiver of the probe is configured such that a transmitter and a receiver are separated and the opening, the receiver, and the transmitter are concentrically formed in order from the center. Non-contact ultrasonic tonometer. The non-contact ultrasonic tonometer according to claim 6,
A first alignment index projection optical system that is disposed outside the outer edge of the probe and projects an alignment index for aligning the probe in the vertical and horizontal directions with respect to the subject's eye; A non-contact ultrasonic tonometer. The non-contact ultrasonic tonometer according to claim 7,
The non-contact ultrasonic tonometer, wherein the first alignment index projection optical system is arranged so that a central axis thereof is coaxial with an observation optical axis of the observation optical system. The non-contact ultrasonic tonometer according to claim 8,
A second alignment index projection optical system that projects an alignment index for performing alignment in the working distance direction of the probe with respect to the subject's eye from an oblique direction;
A working distance detection optical system that detects corneal reflected light from the second alignment index projection optical system from an oblique direction;
The non-contact ultrasonic tonometer, wherein the second alignment index projection optical system and the working distance detection optical system are arranged symmetrically with respect to the central axis of the probe.   10. The non-contact ultrasonic tonometer according to claim 1, wherein at least one of the transmission / reception units is a broadband air-coupled probe.   The non-contact ultrasonic tonometer according to claim 10, further comprising: a fixation optical axis for projecting a fixation target onto the subject's eye through the opening, and a central axis of the probe and the light A non-contact ultrasonic tonometer comprising a fixation target projection optical system arranged so as to be coaxial with an axis. The non-contact ultrasonic tonometer according to claim 6,
The non-contact type ultrasonic tonometer is characterized in that the alignment detection optical system is disposed in two directions obliquely forward with respect to the subject's eye.

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