JP2019208853A - Ultrasound tonometer - Google Patents

Abstract

To provide an ultrasound tonometer capable of appropriately projecting ultrasound to a subject eye.SOLUTION: Provided is an ultrasound tonometer which uses ultrasound to measure an intraocular pressure of a subject eye, comprising: projection means for projecting ultrasound to the subject eye; and suppression means for suppressing the ultrasound projected to the subject eye by the projection means. Alternatively provided is an ultrasound tonometer which uses ultrasound to measure an intraocular pressure of a subject eye, comprising: projection means for projecting ultrasound to the subject eye; and shield means for shielding at least a portion of an opening provided in the projection path of the projection means, in a housing in which the projection means is contained. This ensures appropriate ultrasound projection to the subject eye.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to an ultrasonic tonometer that measures intraocular pressure of an eye to be examined using ultrasonic waves.

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

  As a non-contact tonometer, an ultrasonic tonometer that measures intraocular pressure using ultrasound has been proposed (see Patent Document 1). The ultrasonic tonometer of Patent Document 1 detects the radiation pressure in a predetermined deformed state by detecting the applanation state of the cornea when the ultrasonic wave is radiated to the cornea and the radiation pressure injected to the cornea. It is converted into pressure.

  As an ultrasonic tonometer, a device that measures intraocular pressure based on the relationship between the characteristics (amplitude and phase) of a reflected wave from the cornea and the intraocular pressure has been proposed (see Patent Document 2).

JP-A-5-253190 JP 2009-268651 A

  The ultrasonic tonometer as described above is expected not to cause discomfort to the subject compared to the air jet tonometer. However, it has been found that even an ultrasonic tonometer may cause discomfort to the subject.

  This indication makes it a technical subject to provide the ultrasonic tonometer which can irradiate an ultrasonic wave suitably with respect to the eye to be examined in view of the conventional problem.

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

(1) An ultrasonic tonometer that measures intraocular pressure of an eye to be examined using ultrasonic waves, an irradiating unit that irradiates the subject eye with ultrasonic waves, and the irradiating unit irradiates the eye to be examined Suppression means for suppressing ultrasonic waves.
(2) An ultrasonic tonometer that measures an intraocular pressure of an eye to be examined using ultrasonic waves, an irradiating unit that irradiates the subject's eye with ultrasonic waves, and a housing that houses the irradiating unit inside It is characterized by comprising shielding means for shielding at least a part of the opening provided on the irradiation path of the irradiation means.

It is an external view of an ultrasonic tonometer. It is the schematic which shows the inside of a housing | casing. It is the schematic which shows the structure of an irradiation part. It is the schematic which shows the structure of a suppression part. It is a figure which shows the example of a change of a suppression part. It is a block diagram which shows the control system of a present Example. It is a flowchart which shows the control action of a present Example. It is a figure which shows a voltage waveform. It is a figure which shows the output of an irradiation part.

<Embodiment>
Hereinafter, embodiments according to the present disclosure will be described. The ultrasonic tonometer measures the intraocular pressure of the subject's eye using ultrasonic waves. The ultrasonic tonometer includes an irradiation unit (for example, the irradiation unit 100) and a suppression unit (for example, the suppression unit 300). For example, the irradiation unit irradiates the eye to be examined with ultrasonic waves. The irradiation unit includes a vibrator and the like. The suppression unit suppresses the ultrasonic wave irradiated to the eye to be examined by the irradiation unit. For example, the suppression unit suppresses the ultrasonic wave irradiated to the eye to be inspected until a predetermined output is obtained by the irradiation unit. For example, the suppression unit suppresses the ultrasonic wave coming out of the apparatus while increasing the output of the irradiation unit. The suppression unit can reduce the feeling of pressure or discomfort given to the subject's eye by suppressing excess ultrasonic waves. In addition, the suppression part should just suppress at least one part of the ultrasonic wave output from an irradiation part. Further, the suppressing unit may suppress the sound pressure, acoustic radiation pressure, acoustic flow, or the like of the ultrasonic waves by suppressing the ultrasonic waves.

  The ultrasonic tonometer may further include a control unit (for example, the control unit 70). For example, the control unit controls driving of the suppressing unit. A control part cancels | releases the suppression by a suppression part, when it determines with the output of the irradiation part becoming a predetermined value, while suppressing the ultrasonic wave from an irradiation part. As a result, the ultrasonic tonometer can irradiate the subject's eye with appropriate ultrasound without irradiating the subject's eye with extra ultrasound.

  The control unit may start suppression by the suppression unit after irradiating the eye to be examined with a predetermined output. Thereby, the suppression unit can prevent the ultrasonic wave from hitting the eye to be examined more than necessary, and can reduce the feeling of pressure or discomfort given to the eye to be examined.

  The suppressing unit is a shielding unit (for example, a shielding unit) that shields an opening (for example, the opening unit 6) provided on the irradiation path of the irradiation unit in a housing (housing 3) that houses the irradiation unit. Part 310). Thereby, it is possible to protect the irradiation unit while suppressing the ultrasonic wave.

<Example>
Hereinafter, examples according to the present disclosure will be described. The ultrasonic tonometer of the present embodiment measures the intraocular pressure of the eye to be examined in a non-contact manner using, for example, ultrasonic waves. An ultrasonic tonometer measures intraocular pressure by optically or acoustically detecting, for example, a shape change or vibration of the subject eye when the subject eye is irradiated with ultrasound. For example, an ultrasonic tonometer continuously irradiates a cornea with a pulse wave or a burst wave, and calculates intraocular pressure based on ultrasonic output information when the cornea is deformed into a predetermined shape (for example, an applanation state). calculate. The output information is, for example, ultrasonic sound pressure, acoustic radiation pressure, irradiation time (for example, elapsed time since the trigger signal was input), frequency, or the like. When the cornea of the eye to be examined is deformed, for example, ultrasonic sound pressure, acoustic radiation pressure, or acoustic flow is used.

  FIG. 1 shows the 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, and the like. An irradiation unit 100, an optical unit 200, a suppression unit 300, and the like, which will be described later, are disposed inside the housing 3. The face support unit 4 supports the face of the eye to be examined. The face support unit 4 is installed on the base 2, for example. The drive unit 5 moves the housing 3 with respect to the base 2 for alignment, for example.

  FIG. 2 is a schematic view of the main configuration inside the housing. For example, the irradiation unit 100, the optical unit 200, the suppression unit 300, and the like are arranged inside the housing 3. The irradiation part 100, the optical unit 200, and the suppression part 300 are demonstrated in order using FIG.

  The irradiation unit 100 irradiates the eye E with ultrasonic waves, for example. For example, the irradiation unit 100 irradiates the cornea with ultrasonic waves and generates acoustic radiation pressure on the cornea. The acoustic radiation pressure is, for example, a force that works in the direction in which sound waves travel. The ultrasonic tonometer 1 of the present embodiment deforms the cornea using, for example, this acoustic radiation pressure. In addition, the irradiation part 100 of a present Example is cylindrical shape, and the optical axis O1 of the optical unit 200 mentioned later is arrange | positioned in the opening part 101 of the center.

  FIG. 3A is a cross-sectional view showing a schematic configuration of the irradiation unit 100, and FIG. 3B is an enlarged view of a range A1 shown in FIG. The irradiation unit 100 of the present embodiment is a so-called Langevin type vibrator. The irradiation unit 100 includes, for example, an ultrasonic element 110, an electrode 120, a mass member 130, a fastening member 160, and the like. The ultrasonic element 110 generates ultrasonic waves. The ultrasonic element 110 may be a voltage element (for example, piezoelectric ceramic) or a magnetostrictive element. The ultrasonic element 110 of the present embodiment has a ring shape. For example, the ultrasonic element 110 may be a laminate of a plurality of piezoelectric elements. In this embodiment, the ultrasonic element 110 uses two stacked piezoelectric elements (for example, the piezoelectric element 111 and the piezoelectric element 112). For example, the electrodes 120 (electrodes 121 and 122) are connected to the two piezoelectric elements, respectively. The electrode 121 and the electrode 122 of the present embodiment are, for example, ring-shaped.

  The mass member 130 sandwiches the ultrasonic element 110, for example. The mass member 130 sandwiches the ultrasonic element 110, for example, increases the tensile strength of the ultrasonic element 110 so that it can withstand strong vibration. Thereby, high output ultrasonic waves can be generated. The mass member 130 may be a metal block, for example. For example, the mass member 130 includes a sonotrode (also referred to as a horn or a front mass) 131, a back mass 132, and the like.

  The sonotrode 131 is a mass member arranged in front of the ultrasonic element 110 (on the eye side to be examined). The sonotrode 131 propagates ultrasonic waves generated by the ultrasonic element 110 into the air. The sonotrode 131 of this embodiment is cylindrical. A female thread portion 133 is formed in part on the inner circle portion of the sonotrode 131. The female screw portion 133 is screwed with a male screw portion 161 formed on a fastening member 160 described later. The sonotrode 131 may have a shape that converges ultrasonic waves. For example, the end surface of the sonotrode 131 on the eye side may be inclined toward the opening 101 and may have a tapered shape. The sonotrode 131 may be a cylinder having a non-uniform thickness. For example, the sonotrode 131 may have a shape whose outer diameter and inner diameter change with respect to the longitudinal direction of the cylinder.

  The back mass 132 is a mass member disposed behind the ultrasonic element 110. The back mass 132 sandwiches the ultrasonic element 110 together with the sonotrode 131. The back mass 132 is, for example, cylindrical. A female screw part 134 is formed in part on the inner circle part of the back mass 132. The female screw portion 134 is screwed with a male screw portion 161 of a fastening member 160 described later. Further, the back mass 132 includes a flange portion 135. The flange portion 135 is held by the mounting portion 400.

  For example, the tightening member 160 tightens the mass member 130 and the ultrasonic element 110 sandwiched between the mass members 130. The fastening member 160 is, for example, a hollow bolt. The tightening member 160 has, for example, a cylindrical shape and includes an external thread portion 161 on the outer circle portion. The male threaded portion 161 of the tightening member 160 is screwed with female threaded portions 133 and 134 formed inside the sonotrode 131 and the back mass 132. The sonotrode 131 and the back mass 132 are tightened in the direction in which they are attracted to each other by the tightening member 160. As a result, the ultrasonic element 101 sandwiched between the sonotrode 131 and the back mass 132 is tightened and a pressure is applied.

  The irradiation unit 100 may include an insulating member 170. The insulating member 170 prevents, for example, the electrode 120 or the ultrasonic element 110 from coming into contact with the fastening member 160. For example, the insulating member 170 is disposed between the electrode 120 and the fastening member 160. The insulating member 170 has, for example, a sleeve shape.

<Optical unit>
The optical unit 200 performs, for example, observation or measurement of the eye to be examined (see FIG. 2). The optical unit 200 includes, for example, an objective system 210, an observation system 220, a fixation target projection system 230, an index projection system 250, an applanation detection system 260, a dichroic mirror 201, a beam splitter 202, a beam splitter 203, a beam splitter 204, and the like. Prepare.

  The objective system 210 is, for example, an optical system for taking light from outside the housing 3 into the optical unit 200 or irradiating the light from the optical unit 200 to the outside of the housing 3. The objective system 210 includes, for example, an optical element. The objective system 210 may include an optical element (such as an objective lens and a relay lens).

  The illumination optical system 240 illuminates the eye to be examined. For example, the illumination optical system 240 illuminates the eye to be examined with infrared light. For example, the illumination optical system 240 includes an illumination light source 241. For example, the illumination light source 241 is disposed obliquely in front of the eye to be examined. The illumination light source 241 emits infrared light, for example. The illumination light source 240 may include a plurality of illumination light sources 241.

  The observation system 220 captures an observation image of the eye to be examined, for example. For example, the observation system 220 captures an anterior segment image of the eye to be examined. The observation system 220 includes, for example, a light receiving lens 221 and a light receiving element 222. For example, the observation system 220 receives light from the illumination light source 241 reflected by the eye to be examined. The observation system receives, for example, a reflected light beam from the eye to be examined with the optical axis O1 as the center. For example, reflected light from the eye to be examined passes through the opening 110 of the irradiation unit 100 and is received by the light receiving element 222 via the objective system 210 and the light receiving lens 221.

  The fixation target projection system 230 projects a fixation target on the eye to be examined, for example. The fixation target projection system 230 includes, for example, a target light source 231, an aperture 232, a light projection lens 233, an aperture 234, and the like. Light from the target light source 231 passes through the diaphragm 232, the light projecting lens 233, the diaphragm 232, and the like along the 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 beam splitter 2 passes through the objective system 210 along the optical axis O1 and is irradiated to the eye to be examined. Since the visual target of the fixation target projection system 230 is fixed by the subject, the visual line of the subject is stabilized.

  The index projection system 250 projects an index on the eye to be examined, for example. The index projection system 250 projects an index for XY alignment onto the eye to be examined. The index projection system 250 includes, for example, an index light source (for example, an infrared light source) 251, an aperture 252, a light projecting lens 253, and the like. The light from the index light source 251 passes through the stop 252 and the light projection lens 253 along the optical axis O3, and is reflected by the beam splitter 202. For example, the beam splitter 202 makes the optical axis O3 of the index projection system 250 coaxial with the optical axis O1. The light of the index light source 251 reflected by the beam splitter 202 passes through the objective system 210 along the optical axis O1 and is irradiated to the eye to be examined. The light of the index light source 251 irradiated to the eye to be examined is reflected by the eye to be examined, passes through the objective system 210, the light receiving lens 221 and the like along the optical axis O1 again and is received by the light receiving element 222. The index received by the light receiving element is used for XY alignment, for example. In this case, for example, the index projection system 250 and the observation system 220 function as XY alignment detection means.

  The deformation detection system 260 detects, for example, the corneal shape of the eye to be examined. The deformation detection system 260 detects, for example, deformation of the cornea of the eye to be examined. The deformation detection system 260 includes, for example, a light receiving lens 261, a diaphragm 262, a light receiving element 263, and the like. For example, the deformation detection system 260 may detect the deformation of the cornea based on the corneal reflection light received by the light receiving element 263. For example, the deformation detection system 260 may detect the deformation of the cornea by causing the light receiving element 263 to receive the light reflected from the cornea of the eye to be examined by the light from the index light source 251. For example, the corneal reflection light passes through the objective system 210 along the optical axis O <b> 1 and is reflected by the beam splitter 202 and the beam splitter 203. Then, the corneal reflection light passes through the light receiving lens 261 and the diaphragm 262 along the optical axis O4 and is received by the light receiving element 263.

  For example, the deformation detection system 260 may detect the deformation state of the cornea based on the magnitude of the light reception signal of the light receiving element 236. For example, the deformation detection system 260 may detect that the cornea is in an applanation state when the amount of light received by the light receiving element 236 is maximized. In this case, for example, the deformation detection system 260 is set so that the amount of received light is maximized when the cornea of the eye to be examined is in an applanation state.

  The deformation detection system 260 may be an anterior ocular segment image capturing unit such as an OCT or a Scheimpflug camera. For example, the deformation detection system 260 may detect the deformation amount or deformation speed of the cornea.

  The corneal thickness measurement system 270 measures, for example, the corneal thickness of the eye to be examined. The corneal thickness measurement system 270 may include, for example, a measurement light source 271, a light projection lens 272, a diaphragm 273, a light receiving lens 274, a light receiving element 275, and the like. For example, the light from the light source 271 passes through the light projection lens 272 and the stop 273 along the optical axis O5 and is applied to the eye to be examined. The reflected light reflected by the eye to be examined is collected by the light receiving lens 274 along the optical axis O6 and received by the light receiving element 275.

  For example, the Z alignment detection system 280 detects an alignment state in the Z direction. For example, the Z alignment detection system 280 includes a light receiving element 281. 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 reflected light that is reflected from the cornea of the eye to be examined by the light from the light source 271. In this case, the Z alignment detection system 280 may receive, for example, a bright spot formed by reflection of light from the light source 271 by the cornea of the eye to be examined. Thus, the light source 271 may also be used as a light source for Z alignment detection. For example, light from the light source 271 reflected by the cornea is reflected by the beam splitter 204 along the optical axis O 6 and received by the light receiving element 281.

<Suppression part>
The suppression unit 300 suppresses, for example, ultrasonic waves that are irradiated to the eye to be inspected until a predetermined output is obtained by the irradiation unit 100. The predetermined output is, for example, the output of the irradiation unit 100 necessary for measuring intraocular pressure, and can be arbitrarily set. When the intraocular pressure is measured by deforming the eye to be examined as in this embodiment, the output value is set to deform the eye to be examined into a predetermined shape.

  The suppression unit 300 according to the present embodiment shields the opening 6 of the apparatus housing 3 provided on the front surface (examinee side) of the irradiation unit 100. The suppression unit 300 includes, for example, a shielding unit 310 and a driving unit 320. The shielding part 310 shields at least a part of the opening 6. The driving unit 320 drives the shielding unit 310. By the driving of the driving unit 320, the shielding state of the opening 6 is changed.

  As shown in FIG. 4, the shielding part 310 of the present embodiment includes a plurality of blade parts and has a configuration like a diaphragm of a camera. The plurality of blade portions (311a to 311h) rotate on their respective rotation shafts (312a to 312h), whereby the opening 6 is gradually shielded from the periphery toward the center. For example, the state where the opening 6 is opened as shown in FIG. 4A, the state where a part of the opening 6 is shielded as shown in FIG. 4B, and the whole opening 6 as shown in FIG. 4C. Can be in a shielded state. For example, as shown in FIG. 4B, shielding is performed until the cylindrical portion of the irradiation unit 100 that outputs ultrasonic waves is hidden, and the area around the optical axis O1 of the optical unit 200 (the central portion of the opening 6) is released. By setting the state, observation or measurement by the optical unit 200 can be performed while suppressing the ultrasonic wave irradiated from the irradiation unit 100.

  In addition, the suppression part 300 can prevent the irradiation part 100 from always exposing from the opening part 6 by providing the shielding part 310, and can protect the irradiation part 100. For example, as shown in FIGS. 4B and 4C, a finger of an examiner or the like comes into contact with the irradiation unit 100 or is soiled by shielding part or the whole of the opening 6 except during ultrasonic irradiation. Or it can prevent that dust etc. adhere. Thereby, it is possible to reduce a decrease in output due to a change in the characteristics of the irradiation unit 100.

  In addition, the shape of the shielding part 310 is not restricted to the structure shown in FIG. For example, as shown to Fig.5 (a), the structure which match | combines two shielding board 318a, 318b provided with the semicircle notch 319a, 319b may be sufficient. For example, in the case of suppressing the ultrasonic wave, as shown in FIG. 5B, the casing is formed with a circular opening 317 formed at the center by the notches 319a and 319b of the two shielding plates 318a and 318b. 3 openings 6 are shielded. As a result, the optical path of the optical unit 200 can be secured while suppressing ultrasonic waves. Further, when the power of the apparatus is turned off, as shown in FIG. 5 (c), the two openings 318a and 318b are put together so that the notches 319a and 319b are overlapped with each other, so that the entire opening 6 is made. The irradiation unit 100 may be protected by shielding. Of course, the structure which has two or more shielding boards provided with the notch may be sufficient. For example, the structure which the several shielding board which has a notch opens and closes radially may be sufficient.

  The shielding part 310 may be transparent (translucent material). In this case, observation or measurement by the optical system can be performed using the light transmitted through the shielding part 310 even while the opening part 6 is shielded by the shielding part 310 and the ultrasonic waves are suppressed.

  The suppressing unit 300 is not limited to a shielding member such as a shutter, and may be configured to arrange a sound absorbing material or the like in an ultrasonic wave irradiation path. The suppression unit 300 does not need to block all of the ultrasonic waves output from the irradiation unit 100, and it is sufficient if the ultrasonic waves irradiated to the eye to be examined can be reduced by suppressing at least some of the ultrasonic waves. Further, the suppressing unit 300 may be an elastic body such as rubber. In this case, until the necessary output is reached, the vibration may be restricted by bringing the suppressing unit 300 into contact with the irradiation unit 100 and the ultrasonic wave irradiated to the eye to be examined may be suppressed. That is, the suppression unit 300 may include a vibration damping unit that suppresses vibration of the irradiation unit 100 by contacting an elastic body or the like.

<Control unit>
Next, the configuration of the control system will be described with reference to FIG. The control unit 70 performs, for example, control of the entire apparatus, calculation processing of measurement values, and the like. The control unit 70 is realized by, for example, a general CPU (Central Processing Unit) 71, a ROM 72, a RAM 73, and the like. The ROM 72 stores various programs for controlling the operation of the ultrasonic tonometer 1, initial values, and the like. The RAM 73 temporarily stores various information. The control unit 70 may be configured by one control unit or a plurality of control units (that is, a plurality of processors). The control unit 70 may be connected to, for example, the drive unit 5, the storage unit 74, the display unit 75, the operation unit 76, the irradiation unit 100, the optical unit 200, and the like.

  The storage unit 74 is a non-transitory storage medium that can retain stored contents even when power supply is interrupted. For example, a hard disk drive, a flash ROM, a removable USB memory, or the like can be used as the storage unit 74.

  The display unit 75 displays the measurement result of the eye to be examined, for example. The display unit 75 may have a touch panel function.

  The operation unit 76 receives various operation instructions from the examiner. The operation unit 76 outputs an operation signal corresponding to the input operation instruction to the control unit 70. For the operation unit 76, for example, at least one of user interfaces such as a touch panel, a mouse, a joystick, and a keyboard may be used. When the display unit 75 is a touch panel, the display unit 75 may function as the operation unit 76.

<Control action>
The control operation of the ultrasonic tonometer having the above configuration will be described with reference to FIG.
(Step S1: Alignment)
First, the control unit 70 performs alignment with respect to the subject's eye of the subject whose face is supported by the face support unit 4. For example, the control unit 70 detects a bright spot by the index projection unit 250 from the front image of the anterior segment acquired by the light receiving element 222, and drives the drive unit 5 so that the position of the bright spot becomes a predetermined position. Of course, the examiner may manually perform alignment on the eye to be examined using the operation unit 76 or the like while viewing the display unit 75. When the drive unit 5 is driven, the control unit 70 determines whether or not the alignment is appropriate based on whether or not the position of the bright spot in the anterior segment image is a predetermined position.

(Step S2: Measurement of corneal thickness)
After the alignment with respect to the eye E is completed, the control unit 70 measures the corneal thickness using the corneal thickness measurement system 270. For example, the control unit 70 calculates the corneal thickness based on the light reception signal received by the light receiving element 275. For example, the control unit 70 may obtain the corneal thickness from the positional relationship between the peak value of the reflected light on the corneal surface and the peak value of the reflected light on the corneal back surface based on the light reception signal. For example, the control unit 70 stores the obtained corneal thickness in the storage unit 74 or the like.

(Step S3: Start suppression)
The control unit 70 controls the suppression unit 300 so as to be able to suppress the ultrasonic wave output by the irradiation unit 100. For example, the control part 70 drives the shielding part 310 by the drive part 320, and shields the opening part 6 to such an extent that the irradiation part 100 is hidden. By irradiating the irradiation unit 100 with the shielding unit 310, the ultrasonic wave irradiated from the irradiation unit 100 to the eye to be examined is suppressed. Note that step S3 may be performed before or during step S1 or step S2 as long as the irradiation unit 100 is not driven. For example, suppression by the suppression unit 300 may be started when the apparatus is started, or suppression may be started during alignment or corneal thickness measurement. When the shielding part 310 is shielding the opening part 6 before starting of an apparatus, you may maintain a shielding state as it is. Of course, if the output of the irradiating unit 100 is still weak during the increase, even if the suppression is started after the driving of the irradiating unit 100 is started, it is possible to suppress a part of the ultrasonic wave irradiated to the eye to be examined. It is.

(Step S4: Start of irradiation unit output)
The control unit 70 starts driving the irradiation unit 100. For example, the control unit 70 generates an ultrasonic wave by applying a voltage to the ultrasonic element 110. In this embodiment, sound pressure or acoustic radiation pressure is generated 140 dB or more in order to measure an eye to be examined having a size of 5 mmHg or more. The acoustic radiation pressure gradually rises by continuously applying a voltage burst wave. For example, in order to obtain a sound pressure or acoustic radiation pressure of 140 dB or more, a burst wave is continuously applied to the ultrasonic element 110 for a time of 1 to 100 msec or more. In addition, while the sound pressure or the acoustic radiation pressure is increased, an ultrasonic wave is generated from the irradiation unit 100. However, since the opening 6 is shielded by the suppression unit 300, the ultrasonic wave hitting the eye to be examined is suppressed. .

(Step S5: Output monitoring)
The control unit 70 monitors the output of the irradiation unit 100. When monitoring the output, for example, the voltage waveform applied to the ultrasonic element 110 may be monitored, or the output of the irradiation unit 100 may be monitored by a separately provided sensor. In the former case, if it is assumed that the resonance frequency of the irradiation unit 100 is stable, the control unit 70 correlates with the ultrasonic output such as the number of cycles or application time of the burst wave B to be applied as shown in FIG. The output of the irradiation unit 100 is monitored based on a certain numerical value. In the latter case, the output of the irradiation unit 100 is monitored by a sensor 500 provided around the irradiation unit 100 as shown in FIG. The sensor 500 is an ultrasonic sensor, a displacement sensor, a pressure sensor, or the like.

(Step S6: determination process)
The control unit 70 determines whether or not the output of the irradiation unit 100 has reached a predetermined value. For example, as shown in FIG. 9, in the ultrasonic output acquired by the sensor 500, it may be determined whether or not the value has reached a predetermined value K, or the output does not increase due to saturation. It may be determined whether or not. In this embodiment, it is determined whether or not an acoustic radiation pressure (for example, 140 dB or more) necessary for deforming the cornea has been reached. When the output of the irradiation unit 100 exceeds a predetermined value, the control unit 70 proceeds to step S7.

(Step S7: Suppression cancellation / ultrasound irradiation)
When the output of the irradiation unit 100 reaches a predetermined value, the control unit 70 releases the suppression of ultrasonic waves by the suppression unit 300. For example, the driving unit 320 drives the shielding unit 310 to open the opening 6. As a result, the ultrasonic wave output from the irradiation unit 100 is irradiated to the eye without being suppressed, and the cornea of the eye to be examined is deformed by the acoustic radiation pressure of the ultrasonic wave. Note that the control unit 70 may control the timing at which the suppression of the suppression unit 300 is released in consideration of the drive time of the suppression unit 300. For example, when it takes about 1 to 50 msec for the suppression unit 300 to open the opening 6, the timing is 1 to 50 msec earlier than the time when a predetermined output is obtained after starting the output of the irradiation unit 100. The suppression unit 300 is driven in advance. Accordingly, the opening 6 is just opened when the output becomes 140 dB or more after about 1 to 100 msec from the output start of the irradiation unit 100. In addition, when the time until the predetermined output is obtained after the output of the irradiation unit 100 is started is shorter than the driving time of the suppression unit 300, the suppression unit 300 is driven before the irradiation unit 100 is driven. Also good.

(Step S8: Deformation detection)
The control unit 70 detects the deformation state of the cornea by the deformation detection system 260. For example, the control unit 70 detects that the cornea is deformed into a predetermined shape (applanation state or flat state) based on the light reception signal of the light receiving element 263.

(Step S9: Resume suppression)
When the irradiation unit 100 irradiates the subject's eye with ultrasonic waves, the control unit 70 starts suppression of the ultrasonic waves by the suppression unit 300 again. For example, the control unit 70 may restart the suppression of the suppression unit 300 after detecting that the cornea has been deformed by the deformation detection system 260, or a predetermined time has elapsed since the suppression of the ultrasonic wave was canceled in step S6. Suppression may be resumed later. In the former case, even if the cornea is not deformed to the applanation state, suppression may be resumed when the cornea starts to flatten. For example, the suppression unit 300 may be driven when the deformation detection signal starts to be detected by the deformation detection system 260.

(Step S10: intraocular pressure calculation)
For example, the control unit 70 calculates the intraocular pressure of the subject eye based on the acoustic radiation pressure (or sound pressure) when the cornea of the subject eye is deformed into a predetermined shape. The acoustic radiation pressure (or sound pressure) applied to the eye to be examined has a correlation with the ultrasonic irradiation time, and increases as the ultrasonic irradiation time increases. Therefore, the control unit 70 obtains the acoustic radiation pressure (or sound pressure) when the cornea is deformed into a predetermined shape based on the ultrasonic wave irradiation time. The relationship between the acoustic radiation pressure (or sound pressure) when the cornea is deformed into a predetermined shape and the intraocular pressure of the eye to be examined is obtained in advance by experiments or the like and stored in the storage unit 74 or the like. The control unit 70 determines the intraocular pressure of the eye to be examined based on the acoustic radiation pressure (or sound pressure) when the cornea is deformed into a predetermined shape and the relationship stored in the storage unit 74.

  Of course, the calculation method of the intraocular pressure is not limited to the above, and various methods may be used. For example, the control unit 70 may obtain the amount of cornea deformation by the deformation detection system 260 and obtain the intraocular pressure by multiplying the amount of deformation by a conversion coefficient. For example, the control unit 70 may correct the intraocular pressure value calculated according to the corneal thickness stored in the storage unit 74.

  The control unit 70 may measure the intraocular pressure based on the ultrasonic wave reflected by the eye to be examined. For example, the intraocular pressure may be measured based on the characteristic change of the ultrasonic wave reflected by the eye to be examined, or the deformation amount of the cornea is acquired from the ultrasonic wave reflected by the eye to be examined, and the intraocular pressure is calculated based on the deformation amount. You may measure.

  As described above, the ultrasonic tonometer according to the present embodiment temporarily shields the opening 6 by the suppressing unit 300 until the sound pressure or the acoustic radiation pressure rises to a predetermined output, and extra ultrasonic waves. Avoid contact with the subject's eye. If the ultrasonic wave continues to hit the eye to be examined for a long time, the eyes (cornea) may feel pressure. Therefore, the ultrasonic wave applied to the eye to be examined is suppressed by the suppression unit 300 and is given to the eye to be examined. The feeling of pressure or discomfort can be suppressed.

  Moreover, the control part 70 of a present Example determines whether the ultrasonic wave became a predetermined output value, and cancels the suppression by the suppression part 300, when it determines with having become the predetermined output value. Accordingly, it is possible to irradiate the subject's eye with appropriate ultrasound without applying unnecessary ultrasound to the subject's eye.

  In addition, after irradiating ultrasonic waves with an output capable of measuring intraocular pressure, by starting suppression by the suppression unit 300, it is possible to prevent excessive ultrasonic waves that hit the subject's eye after the intraocular pressure becomes measurable, and The feeling of pressure or discomfort given can be reduced.

  In order to protect the irradiation unit 100, the control unit 70 may shield the opening 6 with the shielding unit 310 after the measurement is completed, or may shield the opening 6 when the apparatus is turned off or during sleep. Also good. In this case, the whole or part of the opening 6 shielded at the time of starting the apparatus or before starting the measurement may be opened. The control unit 70 may perform control for suppressing the ultrasonic wave and control for protecting the irradiation unit 100 on the shielding unit 310 in a stepwise manner. The shielding unit 310 may be used as a suppressing unit that suppresses ultrasonic waves and a protective unit that protects the irradiation unit.

  Note that the examiner may arbitrarily select whether or not the drive control of the suppressing unit 300 is performed. For example, the presence / absence of drive control of the suppression unit 300 may be switched based on an operation signal output from the operation unit 76 by accepting the operation of the examiner.

  Note that the timing at which the examiner starts driving the suppression unit 300 may be arbitrarily set in advance. For example, the examiner may set the time until the ultrasonic wave can be suppressed by the suppression unit 300.

  In the present embodiment, the irradiation unit 100 has a cylindrical shape, and the suppression unit 300 suppresses the ultrasonic wave from the irradiation unit 100 by shielding a part of the opening 6, but is not limited thereto. For example, the irradiation unit 100 may have a cylindrical shape or other shapes. When the irradiation unit 100 has a non-hollow shape such as a columnar shape, the suppression unit 300 may shield all the openings 6 in order to suppress the ultrasonic waves output from the irradiation unit 100.

DESCRIPTION OF SYMBOLS 1 Non-contact-type ultrasonic tonometer 2 Base 3 Case 4 Face support part 5 Drive part 6 Support base 100 Irradiation part 200 Optical unit 300 Suppression part 310 Shielding part 320 Drive part

Claims (9)

An ultrasonic tonometer that measures intraocular pressure of a subject's eye using ultrasonic waves,
Irradiating means for irradiating the subject's eye with ultrasound;
Suppression means for suppressing ultrasonic waves irradiated to the eye to be examined by the irradiation means;
An ultrasonic tonometer comprising:   The ultrasonic tonometer according to claim 1, further comprising control means for controlling driving of the suppression means.   The ultrasonic tonometer according to claim 2, wherein when the output of the irradiation unit is determined to be predetermined, the control unit cancels the suppression by the suppression unit.   The ultrasonic tonometer according to claim 2, wherein the control unit starts suppression by the suppression unit after irradiating the eye to be examined with a predetermined output.   The control unit starts driving the suppression unit at a timing set based on a time until the output of the irradiation unit becomes predetermined and a drive time of the suppression unit. The ultrasonic tonometer in any one of 2-4.   The said suppression means is provided with the shielding means which shields at least one part of the opening part provided on the irradiation path | route of the said irradiation means in the housing | casing which accommodates the said irradiation means inside. 5. The ultrasonic tonometer of any of 5.   The ultrasonic tonometer according to claim 1, wherein the suppression unit includes a vibration suppression unit that suppresses vibration by contacting the irradiation unit. An ultrasonic tonometer that measures intraocular pressure of a subject's eye using ultrasonic waves,
Irradiating means for irradiating the subject's eye with ultrasound;
An ultrasonic tonometer comprising: a shielding unit that shields at least a part of an opening provided on an irradiation path of the irradiation unit in a housing that houses the irradiation unit. The ultrasonic tonometer according to claim 8, wherein the shielding unit is also used as a protection unit for protecting the irradiation unit.

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