JP5465946B2 - 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.

  As a device that measures the intraocular pressure of the subject eye by comparing the incident wave incident on the subject eye and the reflected wave from the subject eye, the transducer that detects vibration and the reflected wave from the subject eye is detected. Holding a probe having a vibration detection sensor, and having a probe pen having an elastic cap whose tip is in contact with the eyeball, and adjusting the intraocular pressure of the eye to be examined while the elastic cap is in contact with the eye to be examined A contact-type intraocular pressure inspection apparatus for measuring has been proposed (see Patent Document 1).

  In addition, as a non-contact type configuration, a probe having a transducer that inputs ultrasonic waves to the eye to be examined (however, a model eye) and a vibration detection sensor that detects a reflected wave from the eye to be examined is provided. There has been proposed an intraocular pressure inspection apparatus that measures the intraocular pressure of the eye to be examined in a non-contact manner with a probe placed in front of the eye to be examined (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 eye to be examined, and the burden on the eye to be examined is large. Further, in the case of the configuration of Non-Patent Document 1, it is only assumed to be measured for a model eye, and is still insufficient for measuring an actual human eye, and there are many problems for practical use. For example, in the case of the human eye, the eye moves due to microscopic eye movements or movement of the line of sight of the subject's eye, so the characteristics of the reflected wave detected by the vibration detection sensor (e.g. (Frequency, phase, etc.) may 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 prior art, the present invention provides a non-contact ultrasonic tonometer capable of accurately measuring intraocular pressure of a subject's eye and easily performing alignment with the subject's eye. To do.

  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 in a non-contact manner to a subject's eye cornea is provided, and the characteristics of the corneal reflected wave received by the ultrasonic probe are measured. A non-contact ultrasonic tonometer that measures the intraocular pressure of the subject's eye based on:
An observation optical system for observing the anterior segment of the subject's eye from the front direction;
In the ultrasonic probe, either one of the transmission unit and the reception unit in the transmission / reception unit is disposed outside the observation optical path of the observation optical system, and the other member is the observation optical path of the observation optical system. It is comprised by arrange | positioning in the position which can be transmitted or received using.
(2)
In the non-contact ultrasonic tonometer of (1),
The other transmission / reception unit is held in the observation optical path by a predetermined holding member.
(3)
In the non-contact ultrasonic tonometer of (1) or (2),
The non-contact ultrasonic tonometer is characterized in that the other transmitting / receiving unit is formed with an opening for allowing a light beam for projecting a fixation target or a light beam for projecting an alignment index to pass therethrough.

  According to the present invention, it is possible to accurately measure the intraocular pressure of the subject's eye and to easily perform alignment with 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 have different configurations and are arranged at different positions.

  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 the front direction, and a fixation target projection (presentation) for fixing the subject's eye E. ) The optical system 30, the first index projection optical system 40 for projecting the first index for detecting the alignment state in the vertical and horizontal directions onto the cornea Ec, and the second 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 the index onto the cornea Ec and an index detection optical system 55 for detecting the second index projected onto the cornea Ec are provided.

  In the following description, either one of the transmission unit 12 and the reception unit 13 in the transmission / reception unit 11 is disposed outside the observation optical path of the observation optical system 20, and the other member uses the optical path of the observation optical system 20. It is arranged at a position where transmission or reception is possible (see FIGS. 1, 2 and 6).

  FIG. 2 is a schematic configuration diagram when the probe 10 according to the present embodiment is viewed from the front. In the transmitter / receiver 11, the transmitter 12 is disposed outside the outer periphery of the opening 15, and the receiver 13 is disposed in the observation optical path of the observation optical system 20. Then, the control unit 70 controls the driving of the probe 10, transmits ultrasonic waves from the peripheral region to the subject's cornea using the transmission unit 12, and transmits from the cornea using the reception unit 13. The reflected wave is received from the front direction.

  More specifically, the probe 10 has a substantially ring-shaped opening 15 having a sufficient size for observing the anterior eye part, and a substantially ring-shaped transmitting part 12 outside the opening 15. And has a receiver 13 at the center of the opening 15. The receiving unit 13 is disposed to face the subject eye E at a predetermined working distance. More preferably, the receiving unit 13 is disposed in the vicinity of the eye E of the subject's eye (see FIG. 1).

  In addition, the receiver 13, the opening 15, and the transmitter 12 are arranged concentrically in order from the center. The opening 15 is used as an observation optical path K of the observation optical system 20.

  The transmitter 11 is disposed on the subject eye E side of the base portion 10a in which a through hole having an inner diameter corresponding to the opening 15 is formed, and is disposed in a substantially annular shape outside the through hole. Further, the shape of the outer periphery of the opening 15 is not limited to a perfect circle, and may be various shapes (for example, a rectangle, an ellipse, etc.).

  Further, a light beam for projecting a fixation target emitted from a fixation light source 32 (described later) and a light beam for projecting an alignment index emitted from an alignment light source 42 are provided at the center (on the central axis) of the receiving unit 13. An opening 14 (for example, a circular hole having a diameter of about 1 mm) is formed.

  The objective lens 22 of the observation optical system 20 is disposed in the opening 15, and a hole for holding the receiving unit 13 is formed at the center thereof. Thereby, the receiving unit 13 is held by the objective lens 22. Of course, another optical member (for example, a glass plate, a filter, or the like) may be disposed in the opening 15, or the optical member as described above may not be disposed (however, reception is possible). A member for holding the portion 13 is necessary).

  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 BATTM 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 observation optical system 20 includes an objective lens 22, an imaging lens 24, and a two-dimensional imaging device 26, and the optical axis (observation optical axis) L 1 is substantially coaxial with the central axis of the receiving unit 13. Is arranged. 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 eye E, the vertical and horizontal alignment of the probe 10 with respect to the subject eye E is performed. Made.

  The anterior segment image of the subject's eye E illuminated by the infrared light source 38 passes through the aperture 15 (objective lens 22), transmits through the half mirror 46, and dichroic mirror (infrared transmission / visible reflection) 36. , And an image is formed on the image sensor 26 by the imaging lens 24. The anterior segment image captured by the image sensor 26 is displayed on a monitor 72 described later.

  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 32 a, reflected by the dichroic mirror 36, transmitted through the half mirror 46, and projected onto the fundus of the subject eye E through the opening 14. The optical axis L2 of the fixation target projection optical system 30 is coaxial with the observation optical axis L1 by a dichroic mirror 36 disposed in the optical path (observation optical path) of the observation optical system 20.

  The first index projection optical system 40 has an infrared light source 42 and projects infrared light, which is a first index for detecting the alignment state in the vertical and horizontal directions, onto the cornea Ec from the front direction. Infrared light from the light source 42 has its beam diameter reduced by the aperture stop 42 a, reflected by the half mirror 46, and projected onto the cornea Ec through the opening 14. The optical axis L3 of the first index projection optical system 40 is coaxial with the observation optical axis L1 by a half mirror 46 disposed in the observation optical path (the optical path of the observation light beam).

  The first index image formed on the cornea Ec by the first index projection optical system 40 passes through the aperture 15 (objective lens 22), passes through the half mirror 46, and is dichroic mirror (infrared transmission / visible reflection). ) 36, and forms an image on the image sensor 26 by the imaging lens 24. That is, the observation optical system 20 detects the first index image formed on the cornea Ec by the first index projection optical system 40 (receives infrared light from the light source 42 reflected by the cornea Ec). That is, the observation optical system 20 also serves as an index detection optical system. The first index image captured by the image sensor 26 is displayed on the monitor 72 (see point image I in FIG. 3).

  The second index projection optical system 50 has an infrared light source 51 and projects infrared light, which is a second index for detecting the alignment state in the working distance direction, 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 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 38, 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. 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 first index image I captured by the image sensor 26, a reticle LT and an indicator G described later. 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 first index image I is within the reticle LT. 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, since the transmitter 12 is disposed outside the outer periphery of the opening 15, the area of the transmitter 12 can be secured widely, so that a strong ultrasonic beam can be applied to the cornea Ec. Further, since the receiving unit 13 is disposed at the center, the receiving unit 13 is disposed to face the cornea Ec, so that a corneal reflected wave from the vicinity of the apex of the cornea can be detected efficiently. Therefore, even if the working distance with respect to the subject eye E is increased, the intraocular pressure of the subject eye can be accurately measured. Furthermore, since the receiving unit 13 is disposed in the vicinity of the eye E of the subject's eye E, the corneal reflected wave can be detected more efficiently.

  Further, since the transmission unit 12 is arranged outside the observation optical path, the configuration arranged in the observation optical path is only the reception unit 13, so that a light-shielding region in the central part of the observation optical path is small.

  Further, by arranging the transmission unit 12 so as to surround the opening 15, the S / N ratio of the detection signal of the corneal reflected wave can be increased even if the working distance to the subject eye E is increased. In addition, since the incident wave to the cornea Ec becomes substantially uniform by making the transmitter 12 substantially annular, the reflected wave from the cornea Ec can be detected with high accuracy.

  Further, the cross-sectional shape of the transmission unit 12 on the subject eye E side is not a flat shape as shown in FIG. 1 but may be a conical shape (tapered shape) as shown in FIG. 5A, or FIG. A spherical shape such as

  Further, the transmission unit 12 may be configured by two or more rings. Further, the transmission unit 11 may not be configured to surround substantially the entire opening 15 as illustrated in FIG. 2, but may be configured to surround a part of the outer periphery of the opening 15. Therefore, when the transmission / reception part 11 is arrange | positioned at substantially annular shape, an intermittent circle may be sufficient instead of a continuous circle. 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).

  In the above configuration, the central axes of the transmission unit 12 and the reception unit 13 are arranged so as to be coaxial. However, the present invention is not limited to this, and the central axes of the transmission unit 12 and the reception unit 13 are eccentric. It may be arranged.

  Moreover, in the said structure, although the transmission part 12 and the receiving part 13 become the structure integrated via the objective lens 22, the transmission part 12 and the receiving part 13 may be arrange | positioned separately and independently. Well, the positional relationship before and after is not necessarily the same. Further, the positional relationship between the transmission unit 12 and the reception unit 13 may be reversed.

  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.

  FIG. 6 is a diagram for explaining the measurement system and the optical system of the non-contact ultrasonic tonometer according to the present embodiment, and a specific example in the case where the receiving unit 13 is arranged outside the observation optical path of the observation optical system 20. FIG. In FIG. 6, the same reference numerals as in FIG. 1 perform the same functions unless otherwise specified.

  The ultrasonic reflecting member (acoustic mirror) 90 is disposed at a position facing the subject's eye, and the receiving unit 13 is disposed at a position where the ultrasonic wave can be received via the ultrasonic reflecting member 90.

  More specifically, the reflecting member 90 is disposed in the observation optical path of the observation optical system 20 and reflects the corneal reflection wave by the ultrasonic beam of the transmission unit 12 toward the reception unit 13. In the observation optical system 20, the receiving unit 13 is disposed outside the observation optical path, and the observation optical axis L1 is formed on the ultrasonic propagation path between the ultrasonic reflection member 90 and the eye to be examined. Is provided. The objective lens 22 is formed with an opening 22b for allowing ultrasonic waves to pass therethrough.

  Here, the ultrasonic beam emitted from the transmitter 12 is reflected by the cornea Ec. The corneal reflection wave traveling in the front direction passes through the opening 22 b formed in the objective lens 22, is reflected by the ultrasonic reflection member 90, and then detected by the receiving unit 13. Then, the arithmetic control unit 70 calculates the intraocular pressure based on the output signal from the receiving unit 13.

  In the case where the objective lens 22 is disposed between the ultrasonic reflection member 90 and the eye to be inspected as shown in FIG. 6, the attenuation of the ultrasonic wave by the objective lens 22 can be avoided by providing the opening 22b. . In this case, in order to prevent the anterior ocular segment observation light from being received by the two-dimensional imaging device 26 through the opening 22b and becoming noise light, the ultrasonic reflecting member 90 with a coating having a characteristic of cutting the observation light beam is provided. You may make it use.

  In addition, in the ultrasonic reflection member 90, a member (for example, a colorless and transparent hard plastic plate) having characteristics of reflecting ultrasonic waves and transmitting light may be used as the ultrasonic reflection member 90. Thereby, even if the ultrasonic reflection member 90 is arranged in the optical path of the fixation target projection optical system 30 and in the optical path of the alignment projection optical system 40, vignetting of the fixation light flux and the alignment light flux can be avoided. When the ultrasonic reflecting member 90 having optical transparency is used, in consideration of a change in optical path length due to light passing through the ultrasonic reflecting member, the optical path dividing member such as the beam splitter 36 and the beam splitter 46 is comparable. A member having an area may be used.

  In addition, the present invention is not limited to the above configuration, and by providing an opening in a part of the ultrasonic reflection member 90, the fixation light beam and the alignment light beam may pass through the opening and enter the eye to be examined. . In the above configuration, the case where the ultrasonic reflecting member 90 is disposed in the common optical path of the fixation target projection optical system 30 and the alignment projection optical system 40 has been described. Even when the ultrasonic reflection member 90 is disposed in at least one of the optical paths of the optical system 40, the above configuration can be applied.

  The configuration is not limited to the above, and an ultrasonic reflecting member 90 may be provided between the objective lens 22 of the observation optical system 20 and the eye to be examined.

  In the above configuration, the positional relationship between the transmission unit 12 and the reception unit 13 may be reversed. In this case, the receiving unit 12 is disposed at a position where ultrasonic waves can be transmitted to the subject's eyes via the ultrasonic reflection member 90. The ultrasonic reflection member 90 is used to reflect the ultrasonic beam emitted from the transmission unit 12 toward the eye to be examined.

  In the above configuration, a measurement optical unit for measuring another eye characteristic different from the intraocular pressure may be provided in a part of the optical system. As the measurement optical unit, an eye refractive power measurement unit that projects an index of the fundus of the subject's eye and measures the eye refractive power based on the reflected light, and projects the index on the subject's cornea and shapes the cornea shape based on the reflected light. A corneal shape measurement unit or the like for measurement can be considered.

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 a figure which shows the example of a change of the cross-sectional shape of a transmission part. It is a figure explaining the measurement system and optical system of the non-contact-type ultrasonic tonometer concerning this embodiment, Comprising: It is a figure which shows the specific example when a receiving part is arrange | positioned out of the observation optical path of an observation optical system.

DESCRIPTION OF SYMBOLS 10 Ultrasonic probe 11 Transmission / reception part 12 Transmission part 13 Reception part 14 Opening part 15 Opening part 20 Observation optical system 22 Objective lens 90 Ultrasonic reflection member

Claims (3)

Transmitted in a non-contact ultrasonic beam to an examinee's eye cornea, comprising an ultrasonic probe having a transmitting and receiving unit for receiving, said the characteristics of the corneal reflection wave received by the ultrasonic probe A non-contact ultrasonic tonometer that measures the intraocular pressure of the subject's eye based on:
An observation optical system for observing the anterior segment of the subject's eye from the front direction;
In the ultrasonic probe, either one of the transmission unit and the reception unit in the transmission / reception unit is disposed outside the observation optical path of the observation optical system, and the other member is the observation optical path of the observation optical system. A non-contact ultrasonic tonometer characterized by being arranged at a position where transmission or reception is possible. The non-contact ultrasonic tonometer according to claim 1,
The non-contact ultrasonic tonometer is characterized in that the other transmission / reception unit is held in an observation optical path by a predetermined holding member. The non-contact ultrasonic tonometer according to claim 1 or 2,
The non-contact ultrasonic tonometer is characterized in that the other transmitting / receiving unit is formed with an opening for allowing a light beam for projecting a fixation target or a light beam for projecting an alignment index to pass therethrough.

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