JP5378745B2 - Non-contact ultrasonic tonometer - Google Patents

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.

A device that measures the intraocular pressure of a subject's eye in a non-contact manner using ultrasonic waves is reflected by a vibrator that emits an ultrasonic wave to be incident on the subject's eye (however, a model eye) and the subject's eye. There has been proposed an apparatus that has a probe having a sensor for detecting ultrasonic waves and that measures intraocular pressure based on a signal output from the probe (see Non-Patent Document 1).
Masayuki Kamide and three others "Fundamental research on non-contact type intraocular pressure measurement system using ultrasonic phase shift method", IEICE technical report Sensor Micromachine Division, 2007, p. 93-96

  By the way, in the non-contact ultrasonic tonometer as described above, when the open eye state of the subject's eye is not sufficient (for example, when there is blinking during measurement), the ultrasonic wave incident on the subject's eye May be interrupted by wrinkles (or wrinkles), and corneal reflected waves may not be detected properly, resulting in measurement errors.

  In view of the above-described conventional technology, an object of the present invention is to provide a non-contact ultrasonic tonometer that can suitably measure the intraocular pressure of a subject's eye.

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

(1) a probe that transmits and receives ultrasonic waves to and from the subject's eyes ;
A calculation unit for processing an output signal from the probe to obtain an intraocular pressure of the subject's eye;
In a non-contact ultrasonic tonometer having
It has a detecting means for detecting vignetting of ultrasonic waves caused by eyelids or eyelids of the subject's eyes based on an output signal from the probe.
(2) In the non-contact ultrasonic tonometer of (1),
The arithmetic unit, on the basis of the detection result by the detecting means, and obtains the intraocular pressure of the examinee's eye the obtained ultrasonic waves are received at the absence of the vignetting.

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

  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-right direction (X direction), the up-down direction (Y direction), and the front-rear direction (Z direction) with respect to the subject's 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. A measurement start switch 5 b is provided on the top of the joystick 5. A display monitor 72 is provided on the movable table 3.

  FIG. 2 is a diagram for explaining a measurement system, an optical system, and a control system of the non-contact ultrasonic tonometer according to the present embodiment. The probe (transducer) 10 disposed in front of the eye of the subject eye E is reflected by the vibrator 11 that emits an ultrasonic wave (incident wave) incident on the subject eye E and the subject eye E. And a vibration detection sensor (ultrasonic detection sensor) 13 that detects ultrasonic waves (reflected waves), and is used to measure intraocular pressure of the eye E of the subject in a non-contact manner. Note that the probe 10 of the present embodiment is configured to combine the operation of the transducer 11 and the operation of the vibration detection sensor 13 under the control of the control unit 70. However, the configuration is not limited to this, and the vibrator 11 and the vibration detection sensor 13 may have different configurations.

  In the present embodiment, a pulse wave is used as the ultrasonic wave incident on the subject's eye E, and the vibrator 11 is used as an ultrasonic wave transmitting unit that causes the ultrasonic pulse to be incident on the subject's eye E. The vibration detection sensor 13 is used as an ultrasonic receiving unit that receives a reflected wave by an ultrasonic pulse incident on the subject's eye E.

FIG. 3 is a diagram for explaining a main part of the probe 10 according to the present embodiment. The probe 10 is a broadband air-coupled transducer that transmits and receives ultrasonic waves having a broadband frequency component, and is used by the BAT ^TM probe of Microacoustic. It is done. The BAT ^TM probe is a capacitor type (capacitance type) sensor.

  More specifically, the probe 10 includes a substrate (back plate) 111 formed with a plurality of fine holes 111a each serving as an air pocket, and a lower portion of the substrate 111 (the substrate 111 is not roughened). The first electrode 113 arranged on the surface side), the second electrode 117 arranged on the upper portion of the substrate 111 (the roughened surface side of the substrate 111), the second electrode 117, and the substrate 111 And an insulating film (or dielectric film) 115 (hereinafter abbreviated as the insulating film 115) disposed therebetween.

  Note that it is only necessary that one (upper) surface of the substrate 111 is roughened to form a small air pocket. The insulating film 115 may be made of an insulating polymer material such as polyethylene or polyimide, or an insulating non-polymer material such as silicon nitride, aluminum oxide, or mica.

  Note that the substrate 111, the insulating film 115, and the second electrode 117 have a concavely curved shape, and are configured to converge the ultrasonic beam irradiated to the subject's eye. In addition, at the approximate center of the probe 10, an opening 15 (for example, having a diameter of about 1 to 5 mm) for allowing at least one of a light beam from the fixation light source 32 (described later) and a light beam from the alignment light source 42 to pass therethrough. (See FIG. 2).

  Here, when a voltage is applied between the first electrode 113 and the second electrode 117, the insulating film 115 is vibrated and ultrasonic waves are generated. Further, when the insulating film 115 is vibrated, the air layer between the insulating film 115 and the substrate 111 is vibrated, and the plurality of fine holes 111a each function as an air pocket. Then, the air in the air pocket, and the insulating film 115 and the second electrode 117 are in a resonance state, so that ultrasonic waves with high propagation efficiency in the air are irradiated toward the subject's eye. In this case, for example, broadband ultrasonic waves having a frequency band from about 200 kHz to 1 MHz are emitted. For details of the broadband air-coupled ultrasonic probe shown in FIG. 3, refer to US Pat. No. 5,287,331, JP 2005-506783, and the like.

  Returning to FIG. The probe 10 is sequentially connected to an amplifier 81, a frequency component analysis unit 82, a frequency phase difference specifying unit 83, and a control unit 70. Then, an electric signal corresponding to an incident wave incident on the subject's eye (an outgoing wave emitted from the vibrator 11) and a reflected wave reflected from the subject's eye is an appropriate signal by an amplifier 81. The frequency component analysis unit 82 performs frequency component analysis of the incident wave and the reflected wave, and obtains the spectrum distribution of the phase difference with respect to the frequency for each of the incident wave and the reflected wave.

  Next, the frequency phase difference specifying unit 83 compares the spectrum distribution of the incident wave and the spectrum distribution of the reflected wave, and a phase difference that is a difference between the phase of the incident wave and the phase of the reflected wave at each frequency fx. θx is determined and specified. Here, since the phase difference θx at the frequency fx changes in accordance with the intraocular pressure of the subject eye E (strictly speaking, the change in the hardness of the cornea due to the change in the intraocular pressure), the control unit 70 has the frequency phase difference. The phase difference θx is detected based on the output signal of the specifying unit 83, and the intraocular pressure value of the subject's eye E is obtained based on the detection result. For the hardness detection method using the ultrasonic pulse method described above, refer to Japanese Patent Application Laid-Open No. 2002-272743.

  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. And a first index projection optical system 40 for projecting onto the subject's eye cornea.

  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 subject's eye, the probe 10 is disposed in front of the subject's eye.

  An anterior ocular segment illumination light source 38 that illuminates the subject's eye with infrared light is disposed obliquely in front of the subject's eye. The filter 25 transmits light from the light source 38 and a light source 42 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 subject's anterior ocular segment image to the two-dimensional imaging device 26. In this embodiment, the subject's anterior ocular segment image is guided onto the two-dimensional imaging device 26 by a lens system composed of a plurality of lenses. However, the subject's anterior ocular segment image is formed by one objective lens. May be configured to guide light onto the two-dimensional image sensor 26.

  The fixation target projection optical system 30 includes at least a fixation light source for fixation target projection, and projects a fixation target for fixing the subject's eye toward the subject's eye. 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, and a beam splitter 46. A fixation target is projected onto the subject's eye through an opening 15 formed in the child 10. 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 is directed to the subject's eye via the beam splitter 36 and the opening 15, and projected onto the subject's eye fundus. Thereby, fixation of a subject's eye is made.

  The first index projection optical system 40 has at least an alignment light source for alignment index projection, and projects the alignment index from the front direction toward the anterior eye portion of the subject. 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 an opening 15 formed in the probe 10. And projecting an XY alignment index on the subject's cornea. 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.

  Here, the alignment light beam emitted from the light source 42 passes through the projection lens 44, is reflected by the beam splitter 36, and then irradiates the subject's eye cornea through the opening 15. Then, an index i1 (alignment index image) that is a virtual image of the light source 42 is formed by the alignment light flux specularly reflected by the cornea Ec.

  Then, the light beam from the index i1 travels toward the objective lens 22. In this case, the alignment reflected light that has reached the peripheral region of the probe 10 passes through the objective lens 22, passes through the beam splitter 36 and the beam splitter 46, and is formed on the two-dimensional imaging device 26 by the imaging lens 24. Imaged. That is, the cornea reflection image i1 from the alignment light source 42 and the anterior eye image of the subject eye from the anterior illumination light source 38 are formed on the two-dimensional imaging device 26 through the peripheral region of the probe 10. As a result, the anterior segment image and the corneal bright spot image (alignment index image) are received on the two-dimensional image sensor 26.

  Next, the configuration of the control system will be described. The control unit 70 includes a frequency phase difference specifying unit 83, a light source 32, a light source 42, a two-dimensional imaging device 26, a light source 38, a display monitor 72, a memory 75 as a storage unit, a rotary knob 5a, a measurement start switch 5b, and various switches. It is connected to the arranged control unit 74, XYZ driving unit 6 and the like, and performs control of the entire apparatus, calculation processing of measured values, and the like.

  The memory 75 stores a table indicating the correlation between the phase difference θx at the frequency fx and the intraocular pressure value of the subject's eye, and the control unit 70 is output from the frequency phase difference specifying unit 83. The intraocular pressure value of the subject's eye corresponding to the phase difference θx is acquired by the memory 75 and the obtained intraocular pressure value is displayed on the display monitor 72.

  The correlation between the phase difference θx and the intraocular pressure value of the subject's eye is, for example, the intraocular pressure value of the subject's eye obtained by the Goldman tonometer and the phase difference θx obtained by the present apparatus. The correlation can be set by obtaining an experiment in advance. The memory 75 stores a program for measuring the intraocular pressure of the subject's eye using the probe 10 and a control program for controlling the entire apparatus.

  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 probe 10. Further, the control unit 74 selects an automatic alignment mode for automatically aligning the measuring unit 4 with respect to the subject's eye and a manual alignment mode for manually aligning the measuring unit 4 with respect to the subject's eye. Selection switch 74a for selecting, auto-shot mode for automatically generating a trigger for starting measurement upon completion of alignment, and selection switch 74b for selecting a manual shot mode for generating a trigger for starting measurement based on an operation signal from measurement start switch 5b Is arranged. When the auto-shot mode is set, the control unit 70 determines the suitability of the alignment state based on the detection results from the two-dimensional image sensor 26 and the probe 10, and uses the determination result. Based on this, a trigger signal for starting measurement is issued.

  In addition, the control unit 70 notifies the examiner of the mode selected by the examiner. For example, the selected mode is displayed on the monitor 72 or the selected mode is notified by voice.

  The operation of the apparatus having the above configuration will be described. Here, a case where the automatic alignment mode and the auto shot mode are selected will be described. First, the examiner performs rough alignment with the subject's eyes by moving the measuring unit 4 using the joystick 5 while looking at the display monitor 72. Further, the examiner instructs the subject to look at the fixation target. At this time, as shown in FIG. 4, the control unit 70 monitors the anterior segment image acquired by the two-dimensional imaging device 26 and the reticle LT and the indicator G that are used for alignment with the eye of the subject. 72 is synthesized and displayed.

  FIG. 5 is a flowchart for explaining the operation of the present apparatus. When rough alignment is performed by the examiner and the index i1 image is received on the image sensor 26, the control unit 70 detects the image position of the index i1 image with respect to the observation optical axis L1, and performs measurement on the eye of the subject. An alignment shift in the XY direction of the unit 4 is detected. Then, the control unit 70 drives the drive unit 6 to move the measurement unit 4 in the XY directions so that the detected misalignment falls within a predetermined allowable alignment range. As a result, the index image i1 enters the reticle LT on the monitor 72.

  When the index image i1 falls within the allowable range, the control unit 70 stops driving in the XY directions and proceeds to determination of the working distance and the open state. Here, the control unit 70 uses the probe 10 to emit an ultrasonic pulse toward the subject's eye and detects a reflected wave due to the ultrasonic pulse incident on the subject's eye.

  FIG. 6 is a diagram for explaining the emission control of ultrasonic pulses emitted from the probe 10. In the case of FIG. 6, a pulse oscillation time T1 (for example, 20 μs) and a pulse pause time T2 (for example, about 1 ms) are alternately provided. At time T2, pulse oscillation is stopped. In this case, the oscillation time T1 and the pause time T2 are alternately repeated.

  The reason why the ultrasonic pulse was oscillated a plurality of times during the oscillation time T1 is to improve the S / N ratio by performing FFT processing on the detection signal of the reflected wave output from the probe 10. It is. The pause time T2 is provided in order to prevent interference between the corneal reflected wave by the ultrasonic wave emitted from the probe 10 and the outgoing wave emitted from the probe 10 next.

  FIG. 7 is a waveform diagram showing detection signals of reflected waves output from the probe 10. The control unit 70 detects the working distance W of the probe 10 relative to the subject's eye based on the detection signal of the reflected wave output from the probe 10. More specifically, the time until the ultrasonic pulse emitted from the probe 10 returns to the probe 10 after being reflected by the eye of the subject is measured, and the measured time is the working distance W. Detected as

  Then, the control unit 70 detects the amount of deviation between the working distance W and the appropriate working distance to detect the misalignment in the Z direction, and drives so that the detected misalignment falls within a predetermined allowable alignment range. The unit 6 is driven to move the measuring unit 4 in the Z direction. Then, the control unit 70 stops driving in the Z direction when the misalignment falls within the allowable range. Further, the control unit 70 electronically displays alignment information in the Z direction on the monitor 72 based on the detected Z alignment deviation (for example, display control of the indicator G).

  Further, the control unit 70 detects ultrasonic vignetting (open state of the subject's eye) due to eyelids or eyelids of the subject's eye based on the detection signal of the reflected wave output from the probe 10. More specifically, when the acoustic intensity V of the reflected wave detected by the probe 10 is smaller than the predetermined value Vs, the control unit 70 detects ultrasonic vignetting due to eyelids or wrinkles of the subject's eyes. In this case, the probe 10 that detects the corneal reflection wave for measuring intraocular pressure and the control unit 70 that obtains an output signal from the probe 10 vignetting the ultrasonic wave by the eyelid or eyelid of the subject's eye. It is used as a sensor for detecting the optometry state.

  When the eyelids are firmly open, the ultrasonic wave applied to the subject's eyes is reflected by the cornea without being destroyed by the eyelids (瞼), so that a reflected wave sufficient for measuring intraocular pressure is detected by the probe 10 (See FIG. 7A). On the other hand, when the eyelid is closed or the eyelid is lowered, the ultrasonic wave applied to the eye of the subject is diffusely reflected on the surface of the eyelid (睫) without reaching the cornea (瞼 (睫) Therefore, only a very small amount of ultrasonic waves is detected by the probe 10 (see FIG. 7B).

  Therefore, the control unit 70 determines the presence or absence of ultrasonic vignetting (open eye open state) based on whether or not the acoustic intensity V is equal to or greater than the predetermined value Vs, and monitors the determination result (vignetting detection result). 72 is displayed. Here, if the acoustic intensity V is equal to or greater than the predetermined value Vs, it is determined that the opening is sufficient (no vignetting due to wrinkles / wrinkles). Further, if the sound intensity V is smaller than the predetermined value Vs, it is determined that the opening is insufficient (there is vignetting due to wrinkles and wrinkles), and notification that opening is performed is made on the monitor 8 (for example, “OPEN THE EYE”). ”,“ There is an ultrasonic vignetting due to 瞼 / 睫 ”, etc.). In addition, a voice generation unit may be provided so that the fact that opening is performed is notified by voice.

  In this case, in order to make the open state appropriate, the examiner performs an operation such as urging the subject to open or using the examiner's hand to raise the eyelid or the eyelid. Here, if the opening state becomes an appropriate state, the notification that the opening is performed is ended.

  As described above, when it is determined that the alignment determination and the eyelid determination are appropriate, the control unit 70 automatically issues a trigger signal for starting measurement, and starts tonometry using the reflected wave detection signal. . In this case, the corneal reflected wave Tb is detected at any time corresponding to the ultrasonic wave emitted at a predetermined time interval (for example, the pause time T2) set so as to avoid interference between the emitted wave and the reflected wave. (See FIG. 8).

  Here, the control unit 70 performs blink determination for each corneal reflected wave Tb acquired after the trigger signal is generated, and continues tonometry until a predetermined number of reflected waves for which an intraocular pressure value can be calculated are acquired. To do. In this case, the control unit 70 determines whether or not the corneal reflection wave Tb detected at any time is detected without vignetting using the above-described vignetting detection method. That is, the reflected wave Tb having the acoustic intensity V equal to or higher than the predetermined value Vs is determined as a reflected wave from which an intraocular pressure value can be calculated. Further, the reflected wave Tb having the acoustic intensity V smaller than the predetermined value Vs is determined to be a reflected wave that is caused by blinking, and is excluded from the measurement target. Thereby, a corneal reflection wave detected without vignetting is obtained. It should be noted that the number of acquired reflected waves used for intraocular pressure calculation only needs to be such that variations in intraocular pressure values calculated according to the respective reflected waves fall within a predetermined allowable range.

  When a predetermined number of calculable reflected waves are obtained as described above, an intraocular pressure value is calculated using each reflected wave, and the calculation result is output to the monitor 72 (paper output or data output to an external device). Good). In this case, it is conceivable that an intraocular pressure value corresponding to each reflected wave, an average value, a maximum value, a minimum value, an intermediate value, etc., among a predetermined number of acquired intraocular pressure values are output.

  Note that, during the sampling of the ultrasound for calculating the intraocular pressure value, if an alignment shift exceeding the allowable range is detected, the control unit 70 may interrupt the sampling and restart the automatic alignment. Further, the control unit 70 may determine the working distance for each reflected wave, and exclude the reflected wave whose working distance W exceeds the allowable range from the measurement target. When the state where the opening state is insufficient continues for a predetermined time or longer (for example, 1 second or longer), the control unit 70 interrupts sampling and displays on the monitor 72 that opening is performed. Good.

  With the above configuration, when there is blinking of the subject's eye during the measurement of intraocular pressure, the intraocular pressure is calculated using the reflected wave created by the eyelid or eyelid of the subject's eye. Since it can be avoided, the intraocular pressure is accurately measured.

  In the above description, the open state is determined by the acoustic intensity V of the reflected wave (including blinking determination), but the reflected wave from the cornea and the reflected wave from other than the cornea (瞼, 睫) However, the method is not limited to this as long as the change in the waveform is used. For example, after completion of alignment in the Z direction, when the apportioning distance of the subject's eyes is changed, it may be determined that the open state is insufficient.

  Further, since the intraocular pressure and blink detection are performed using the probe 10, the detection of the reflected wave and the blink detection at a predetermined time interval (for example, the pause time T2) are synchronized. Therefore, blink determination for each reflected wave detected during intraocular pressure measurement is performed with high accuracy. Further, it is not necessary to separately arrange a blink detection configuration, and the apparatus configuration is simplified.

  Further, in the above configuration, the intraocular pressure measurement and the working distance detection are performed using the probe 10, so that the detection of the reflected wave and the working distance detection at a predetermined time interval (for example, the rest time T2) are synchronized. Is done. Therefore, the determination of misalignment with respect to each reflected wave detected during intraocular pressure measurement is performed with high accuracy. Further, it is not necessary to separately arrange a working distance detection configuration, and the device configuration is simplified.

  In the above description, the emission surface shape of the probe 10 is concave so that the ultrasonic irradiation area is formed in a minute region on the cornea. However, the present invention is not limited to this. Ultrasonic waves may be irradiated over a wide range (for example, a region having a diameter of 3 mm on the cornea) within the open eye area of the subject's eye. In this case, since the detection signal of the reflected wave is changed according to the degree of opening of the eyelid of the subject's eye, the opening state of the eyelid (how much the eyelid is open) is detected based on the change of the detection signal. You may do it. A configuration is conceivable in which the open state is detected as insufficient (including blink detection) when the open state of the reed is below a predetermined threshold. Further, the threshold value may be arbitrarily changed.

  Further, even when the surface shape of the emission surface of the probe 10 is a planar shape, it is possible to adopt a configuration for converging ultrasonic waves. In this case, a configuration (so-called acoustic Fresnel zone plate) in which a part of the second electrode 117 is removed in a ring shape and a concentric multiple ring pattern by the second electrode 117 is formed on the emission surface is considered. It is done. In this case, the ultrasonic waves are converged by the interference between the ultrasonic waves emitted from the respective electrodes 117 formed in a ring shape.

  In the above description, the intraocular pressure of the subject's eye is obtained from the phase difference between the incident wave and the reflected wave. However, the intraocular pressure is obtained by processing the output signal from the probe 10 (sensor 13). If it measures, it will not be restricted to this. For example, the intraocular pressure of the subject's eye may be obtained by detecting the acoustic intensity of the reflected wave. In this case, the higher the intraocular pressure, the greater the difference in acoustic impedance between the cornea and air, so the stronger the acoustic intensity is detected, and the lower the intraocular pressure, the smaller the difference in acoustic impedance between the cornea and air, Is weakly detected.

  Further, the intraocular pressure may be obtained by a calculation process by comparing the frequency of the incident wave emitted from the vibrator 11 and the frequency of the reflected wave detected by the sensor 13. More specifically, the phase difference is reduced to zero by changing the frequency of the ultrasonic wave generated by the vibrator 11 when a phase difference occurs between the input waveform to the vibrator 11 and the output waveform from the sensor 13. A phase shift circuit for shifting may be provided, and the intraocular pressure may be obtained by detecting a frequency change amount when the phase difference is shifted to zero.

  In the above description, a broadband air-coupled ultrasonic probe is used as the probe 10. However, the present invention is not limited to this, and a ceramic piezoelectric vibrator may be used.

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 of the non-contact-type ultrasonic tonometer concerning this embodiment, an optical system, and a control system. It is a figure explaining the principal part of the probe 10 which concerns on this embodiment. It is a figure which shows an example of an anterior ocular segment observation screen. It is a flowchart explaining operation | movement of this apparatus. It is a figure explaining the emission control of the ultrasonic pulse radiate | emitted from a probe. It is a wave form diagram which shows the detection signal of the reflected wave output from a probe. It is a wave form diagram which shows the reflected wave detected at any time by a predetermined time interval.

Explanation of symbols

10 Probe 70 Control unit (calculation unit)
72 Monitor

Claims (2)

A probe that transmits and receives ultrasonic waves to and from the subject's eyes ;
A calculation unit for processing an output signal from the probe to obtain an intraocular pressure of the subject's eye;
In a non-contact ultrasonic tonometer having
A non-contact ultrasonic tonometer characterized by comprising detection means for detecting ultrasonic vignetting caused by eyelids or eyelids of a subject's eye based on an output signal from the probe. The non-contact ultrasonic tonometer according to claim 1,
The arithmetic unit, on the basis of the detection result by the detecting means, non-contact type than that and obtains the intraocular pressure of the examinee's eye to obtain the ultrasonic waves received at the absence of the eclipse Sonic tonometer.