JP3986408B2 - Non-contact tonometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact tonometer that measures intraocular pressure by compressing a fluid and spraying it on an eye to be examined and detecting a deformed state of the cornea, and more specifically, detecting a pulse wave based on pulse fluctuation, The present invention relates to a non-contact tonometer that measures intraocular pressure in association with detected pulse waves and intraocular pressure fluctuations.
[0002]
[Prior art]
Intraocular pressure has fluctuations synchronized with blood pulse fluctuations, but when measured randomly with a non-contact tonometer in time, it is unknown which part of the pulse fluctuations are measured, and accurate measurement results Is difficult to obtain. In view of this, a tonometer has been proposed in which a pulse wave based on pulse fluctuations is detected by a pulse wave detector and an intraocular pressure corresponding to (synchronized with) a desired phase position of the pulse wave is measured (for example, see Patent Document 1). . In this tonometer, a pulse wave detector is provided in the forehead contact portion that abuts the forehead of the subject. This is because the face portion closer to the subject's eyes can detect a pulse wave closer to the actual intraocular pressure fluctuation.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-102174
[Problems to be solved by the invention]
By the way, when a pulse wave detector is provided in the forehead support part, it is important that the subject's forehead is in contact with the pulse wave detector and starts measuring intraocular pressure without moving. When detecting the pulse wave, if the subject's face moves, a stable pulse wave signal cannot be obtained due to the influence of ambient light, making it difficult to measure intraocular pressure in synchronization with the desired phase position of the pulse wave, and the reliability of the measurement results. Sexuality also becomes poor.
[0005]
Normally, when detecting a pulse wave, the detection sensitivity (gain) is adjusted according to the detection signal level. However, when the subject's face moves, the detection signal level of the pulse wave is not stable. Therefore, it may take time to measure intraocular pressure. It may be possible for the examiner to confirm the fixed state of the face and eyes of the subject and manually input a pulse wave detection start signal, but this is troublesome for the examiner.
[0006]
In view of the above-described problems of the prior art, the present invention can reduce the time required to measure intraocular pressure associated with a pulse wave without taking the labor of the examiner, and can provide a highly reliable measurement result. It is a technical subject to provide a tonometer.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) In a non-contact tonometer that detects a pulse wave of a subject and measures intraocular pressure in association with the detected pulse wave, a face support unit that supports the face of the subject, and the face support unit A pulse wave detector provided on the eye, an eye detection unit for detecting the eye by irradiating a light beam to the eye to be examined and receiving reflected light thereof, and detecting the pulse wave based on a detection result by the eye detection unit Signal acquisition means for starting acquisition of a pulse wave detection signal from the device.
(2) In the non-contact tonometer of (1), the acquisition start of the pulse wave detection signal by the signal acquisition means includes an adjustment start of detection sensitivity of the pulse wave detection signal output from the pulse wave detector. It is characterized by.
(3) The eye detection means in (1) uses an alignment light beam for forming an alignment index on the cornea as a light beam to be applied to the eye, and the eye to be examined is based on the index formed on the eye cornea. It is characterized by detecting whether or not the measurement can be started.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a present Example is described based on drawing. FIG. 1 is a schematic external view of a non-contact tonometer according to the present invention.
On the base 13, a moving table 14 having a measuring unit 15 at the top is mounted so as to be horizontally movable. The moving table 14 is moved by operation of a joystick 19. Further, by operating the rotary knob of the joystick 19, the measuring unit 15 is moved in the vertical direction (Y direction). Further, the measuring unit 15 moves in the left-right direction (X direction) and the front-rear direction (Z direction) with respect to the moving table 14. The measurement unit 15 is moved in each direction (X, Y, and Z directions) by an X direction moving mechanism 80, a Y direction moving mechanism 81, and a Z direction moving mechanism 82 (see FIG. 2) each having a motor and a slide mechanism. Is called.
[0009]
A face support unit 16 for supporting the subject's face is fixed to the base 13. The face support unit 16 includes a chin base 10 that is fixed to the support base 16a and can be adjusted in height in the vertical direction, and a forehead support portion 17 that is attached to the upper portions of the two columns 16b. The forehead support 17 has a shape along the curve of the subject's forehead. A pulse wave detector 18 for detecting the pulse wave of the subject is provided at the center of the forehead pad 17. Also, two forehead rubbers 17 a are attached to the forehead support 17 on the left and right sides of the pulse wave detector 18. The forehead rubber 17a is disposed at an appropriate distance from the pulse wave detector 18 so that blood flows stably when the subject's forehead is fixed and ischemia does not occur in the forehead.
[0010]
The pulse wave detector 18 includes a light emitting unit and a light receiving unit. Blood hemoglobin contained in human blood has a strong absorption spectrum for light in a certain wavelength band. Blood hemoglobin changes in proportion to the amount of blood flowing through the blood vessels. Therefore, when light of a certain wavelength is emitted from the light emitting part, the detection light reflected from the bone through the skin part of the forehead surface changes according to the amount of change in hemoglobin that changes with the change in blood vessel capacity. The pulse wave of the subject can be detected by changing the intensity of the detection light into an electric signal.
[0011]
FIG. 2 is a diagram illustrating a schematic side configuration of a fluid ejection mechanism disposed in the measurement unit 15 and a schematic configuration of a tonometer control system. Reference numeral 1 denotes a cylinder for air compression, which is provided inclined with respect to the horizontal line of the tonometer main body. 2 is a piston, 3 is a rotary solenoid, and when charge (current, voltage) as drive energy is applied to the rotary solenoid 3, it is moved upward along the cylinder 1 to the piston 2 via the arm 4 and the connecting rod 5. Push up. The air compressed in the air compression chamber 11 that communicates with the cylinder portion 1 as the piston 2 rises is ejected from the nozzle 6 toward the cornea of the eye E. The rotary solenoid 3 is provided with a coil spring (not shown), and when the applied charge is cut, the piston 2 that has been lifted by the biasing force in the downward direction of the coil spring is lowered and returned to the initial position.
[0012]
A transparent glass plate 7 holds the nozzle 6 and transmits observation light, alignment light, and the like. The glass plate 7 is a side wall of the air compression chamber 11. A transparent glass plate 9 is provided on the back surface of the nozzle 6 and constitutes the rear wall of the air compression chamber 11 and transmits observation light and alignment light. Behind the glass plate 9 is an optical system 8 for observation and alignment described later. A pressure sensor 12 detects the pressure in the air compression chamber 11.
[0013]
Reference numeral 20 denotes a control unit for the pressure detection processing circuit 21 for the pressure sensor 12, the signal detection processing circuit 22 for the photodetector 56 of the corneal deformation detection optical system, which will be described later, and the one-dimensional position detection element 57 for the working distance detection. A signal detection processing circuit 26, an image processing circuit 27 for the CCD camera 35, a pulse wave detection processing circuit 28 for the pulse wave detector 18, and a drive circuit 23 for driving the rotary solenoid 3 are connected.
The image processing circuit 27 performs image processing on the photographed image from the CCD camera 35 and inputs the processing result information to the control unit 20. The control circuit 20 obtains the index image position information and pupil position information from the input signal.
[0014]
FIG. 3 is a principal view of the upper-view optical system of the non-contact tonometer. Reference numeral 40 denotes a first alignment light source, and 32 denotes a projection lens. The first alignment light source 40 emits infrared light having a wavelength of 950 nm. The infrared light beam emitted from the first alignment light source 40 is collimated by the projection lens 41 and then reflected by the beam splitter 31. A cornea bright spot i1 is formed by passing through the nozzle 6 along the optical axis L1 and irradiating the eye cornea E to be examined.
[0015]
The second alignment light source 30 has four light sources 30a to 30d. The light sources 30a and 30b and the light sources 30c and 30d are arranged at the same height distance across the axis L1, and the optical distances of the indexes are the same. The light sources 30a to 30d emit infrared light having the same wavelength as that of the first alignment infrared LED. Light from the light sources 30a and 30b is irradiated obliquely upward toward the periphery of the cornea of the eye to be examined, and corneal bright spots i2 and i3 are formed. Light from the light sources 30c and 30d is irradiated obliquely downward toward the periphery of the cornea of the eye to be examined, and corneal bright spots i4 and i5 are formed. The light sources 30a to 30d also serve as illumination light sources that illuminate the anterior segment of the eye to be examined.
[0016]
The luminous fluxes of the corneal bright spots (indexes) i1, i2, i3, i4, and i5 are incident on the CCD camera 35 via the beam splitter 31, the objective lens 32, the beam splitter 33, and the filter 34, and on the imaging device of the CCD camera 35. To form an image. The filter 34 transmits light from the light source 30 and the light source 40 and has a non-transmission characteristic with respect to light from the LED 50 for detecting corneal deformation described later. The image formed on the CCD camera 35 is displayed on the monitor 36.
[0017]
61 is a reticle projection light source, 62 is a reticle plate on which an annular mark or the like is formed, and 63 is a projection lens. The reticle on the reticle plate 62 illuminated by the reticle projection light source is received by the CCD camera 35 via the projection lens 63, the beam splitter 33, and the filter 34.
[0018]
Reference numeral 45 denotes a fixation target projection LED. Light of the fixation target 46 illuminated by the LED 45 passes through the projection lens 47 and is then reflected by the beam splitter 33 toward the eye E. Measurement is performed with the fixation target 46 fixed on the eye to be examined.
[0019]
Reference numeral 50 denotes an infrared LED for detecting corneal deformation. The light emitted from the LED 50 is converted into a substantially parallel light beam by the collimator lens 51 and projected onto the cornea of the eye E to be examined. The light reflected by the eye E passes through the filter 53 having a non-transmission characteristic with respect to the light of the light receiving lens 52, the light source 30, and the light source 40, and then is reflected by the beam splitter 54 and passes through the pinhole plate 55. The light is received by the photodetector 56. The corneal deformation detection optical system is arranged so that the amount of light received by the photodetector 56 is maximized when the eye to be examined is in a predetermined deformed state (flat state).
[0020]
This corneal deformation detection optical system also serves as a part of the working distance detection optical system, and is projected from the LED 50 to form a corneal bright point i6. The light of the corneal bright point i6 that is the index image passes through the light receiving lens 52, the filter 53, and the beam splitter 54 and enters the one-dimensional position detection element 57 such as a PSD or a line sensor. When the eye cornea to be examined moves in the working distance direction, the index image of the corneal bright spot i6 also moves on the one-dimensional position detecting element 57, so that the control unit 20 outputs working distance information from the one-dimensional position detecting element 57 based on the output signal. Get.
[0021]
The operation of the non-contact tonometer having the above configuration will be described. The examiner fixes the eye to be examined using the chin rest 10 and instructs the subject so that the forehead of the subject contacts the forehead support portion 17. When the subject positions the forehead so as to hit the two forehead rubbers 17a, the forehead also comes into contact with the pulse wave detector 18 located at the center thereof. The examiner operates the joystick 19 and the like while observing the anterior segment image displayed on the monitor 36 to roughly align the measurement unit 15 with respect to the subject's eye. When the fixation target 46 becomes visible to the eye to be examined, this is fixed.
[0022]
FIG. 4 shows an example of a screen displayed on the monitor 36 when the XY directions are aligned in an appropriate state. In the state in which the XY directions are aligned in an appropriate state, bright spots i2, i3, i4, and i5 formed around the cornea by alignment light sources 30a, 30b, 30c, and 30d, respectively, and the cornea center by the first alignment light source 40 The formed bright spot i1 is picked up by the camera 35 and displayed on the monitor 36. Reference numeral 64 denotes a reticle image.
[0023]
The control unit 20 drives and controls the X-direction moving mechanism 80 and the Y-direction moving mechanism 81 based on the number of bright spots detected and the positional relationship, and executes auto-alignment that moves the measuring unit 15. Since the positional relationship of the bright spots i1 to i5 and the intervals between the bright spots are given as predetermined data, the control unit 20 specifies which of the detected bright spots i1 to i5, The measurement unit 14 is moved so that the bright spot i1 comes to the center of the reticle image 64. The bright spots i1 to i5 satisfy a predetermined amount of light and can be distinguished from noise depending on whether or not the size is within a predetermined range. If the bright spot i1 falls within a predetermined allowable range, alignment in the XY directions is completed. For details of this auto-alignment, refer to Japanese Patent Application Laid-Open No. 10-71122 filed by the present applicant. Further, the control unit 20 obtains deviation information in the front-rear direction with respect to the eye to be examined based on a signal from the one-dimensional position detection element 57, and drives and controls the Z-direction moving mechanism 82 based on the information to control the measurement unit 15 to Z. Move in the direction.
[0024]
Here, in this apparatus, using the detection results of the bright spots i1 to i5 for alignment, whether or not the subject's face is in a fixed state, that is, the subject can start measurement. Determine whether or not. At this time, even if the alignment is not in an appropriate state, if any of the bright spots i1 to i5 is detected by the camera 35, it can be considered that the subject is ready to start measurement. If any of the bright spots i1 to i5 can be detected by moving the measurement unit 15, the fixation target 46 can be seen by the eye to be examined. By fixing the fixation target 46 to the eye to be examined, the face of the subject is fixed. In this apparatus, if two or more of the bright spots i1 to i5 can be identified, detection of the pulse wave signal from the pulse wave detector 18 is started.
[0025]
In the auto-alignment in the XY directions, five bright spots are used in order to increase the detection range in the apparatus of the embodiment. However, only the bright spot i1 formed at the corneal apex may be used. In this case, if the bright spot i1 satisfies a predetermined detection condition, it is determined that the subject is ready to start measurement. Further, instead of using the bright spots for alignment, an anterior segment image captured by the CCD camera 35 can also be used. For example, the pupil center is detected from the image data of the anterior segment image by image processing, and the fixed state of the subject's face (a state where measurement can be started) is determined based on whether or not the pupil center is within a predetermined range.
[0026]
FIG. 5 is a diagram schematically showing an example of a pulse wave signal processed by the pulse wave detection processing circuit 28. A sudden change appears in the pulse wave detection signal at time t1 when the forehead of the subject contacts the pulse wave detector 18. Then, it is assumed that two or more of the bright spots i1 to i5 can be identified at time t2 by the alignment movement of the measurement unit 15. The control unit 20 commands the pulse wave detection processing circuit 28 to start acquiring the pulse wave detection signal from the pulse wave detector 18 from the time t2. The pulse wave detection processing circuit 28 starts level (gain) adjustment of the output signal from the pulse wave detector 18 according to the instruction signal from the control unit 20. The pulse wave signal processed by the pulse wave detection processing circuit 28 is input to the control unit 20. The level adjustment of the pulse wave detection signal may be started from time t1 when a rapid change appears in the pulse wave detection signal, but extra noise is generated when it starts from time t2 when the stability of the eye to be examined is detected. Since it is not included, it can be adjusted without taking time.
[0027]
The control unit 20 determines whether the usable condition is satisfied for the input pulse wave signal (whether the pulse wave signal is stably obtained) as follows. The determination of the usable condition of the pulse wave signal uses the detection time of the pulse wave peak (the pulse wave peak is determined from the rising slope of the waveform signal, the signal level, etc.) and the height of the pulse wave peak. Either of these may be used, but the determination with higher accuracy can be made by using both. As shown in FIG. 6, the detection time (cycle) from the first pulse wave peak to the second pulse wave peak for three cycles of the pulse wave waveform signal sequentially obtained from the start of pulse wave detection is T1, The detection time (cycle) from the second pulse wave peak to the third pulse wave peak is T2. Here, when both change time Th = | T1-T2 | becomes Th> 10 ms, it is determined as a time error of the pulse wave waveform signal and cannot be used.
[0028]
The height of the first pulse wave peak (height from the bottom) is defined as P1, the height P2 of the second pulse wave peak P2, and the height P3 of the third pulse wave peak. Each peak fluctuation rate is calculated by Pa = P1 / P2, Pb = P2 / P3, and Pc = P1 / P3. As a result, when all of Pa, Pb, and Pc do not fall within the range of 0.9 to 1.1, it is determined that the pulse wave waveform signal has a peak error and cannot be used.
[0029]
In determining the use conditions of the pulse wave signal in this way, if the pulse wave signal with the subject's face moving is used, the number of distorted waveform signals increases, so it is easy to determine that the pulse wave signal cannot be used. It is difficult to move to the measurable state. Also, if signal level adjustment is started when there is a distorted waveform signal, it takes time to adjust the signal level stably, and the accuracy in determining the timing of the desired phase position also deteriorates. Therefore, as described above, such problems can be reduced by starting pulse wave detection after determining the stable state of the subject's face. Furthermore, when the subject's forehead slowly contacts the pulse wave detector 18, the detection signal at time t1 may not change suddenly. Even in such a case, since a trigger signal for starting pulse wave detection can be provided, measurement can be performed smoothly.
[0030]
If the pulse wave signal satisfies the above-described usable conditions, the control unit 20 obtains the phase of the pulse wave from the sampled pulse wave signal (preferably obtained from the average of the sampled pulse wave waveforms), and a predetermined phase position The timing of intraocular pressure measurement is calculated so as to synchronize with.
[0031]
FIG. 7 shows an example of measuring intraocular pressure in synchronization with the phase position of the pulse wave peak. The signal S1 indicates the timing of the pulse wave peak P, which is sequentially determined as coming after the phase period Ta from the pulse wave peak immediately before the usable condition is satisfied. A signal R indicates an alignment completion signal. The solenoid drive signal S3 is output at the timing when both the alignment completion signal R and the signal S1 are obtained, and the measurement is executed. In order to adjust the intraocular pressure measurement timing to the phase position of the pulse wave peak with higher accuracy, the applanation detection time Tapl from when the solenoid node drive signal 3 is output until the cornea is flattened by air injection is considered. Then, it is preferable to output the solenoid drive signal S3 at a timing increased by the time Tapl. The time Tapl may be set using an average intraocular pressure value in the first measurement of the same eye, and set based on the previous intraocular pressure measurement in the second and subsequent measurements. it can.
[0032]
When the solenoid 36 is driven by the solenoid drive signal S3, the piston 2 rises and compressed air is blown from the nozzle 6 to the eye to be examined. The cornea of the eye to be examined is gradually deformed by blowing air, and when the cornea reaches a flat state, the maximum amount of light enters the photodetector 56. The intraocular pressure value is obtained using the time when the applanation signal output from the photodetector 56 shows a peak, or the output signal from the pressure sensor 12 obtained at this time.
[0033]
The phase position of the pulse wave in the intraocular pressure measurement described above, the numerical value in the determination of the availability of the pulse wave signal, etc. are merely examples, and can be changed according to the use situation.
[0034]
【The invention's effect】
As described above, according to the present invention, stable pulse waves can be quickly detected without taking time and effort on the subject. This shortens the measurement time when measuring intraocular pressure synchronized with an arbitrary phase position of the pulse wave. Moreover, a highly reliable measurement result can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic external view of a non-contact tonometer.
FIG. 2 is a diagram illustrating a schematic side configuration of a fluid ejection mechanism and a schematic configuration of a tonometer control system.
FIG. 3 is a diagram showing the main part of the upper viewing optical system of the non-contact tonometer.
FIG. 4 is a diagram showing a screen image displayed on a monitor when an eye to be examined is aligned in an appropriate state.
FIG. 5 is a diagram schematically showing an example of a pulse wave signal processed by a pulse wave detection processing circuit.
FIG. 6 is a diagram illustrating a method in which a control unit determines whether or not an input pulse wave signal satisfies a usable condition (whether or not a pulse wave signal is stably obtained).
FIG. 7 is a diagram illustrating measurement start timing synchronized with a pulse wave peak.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder part 2 Piston 3 Rotary solenoid 15 Measurement part 16 Face support unit 17 Forehead support part 18 Pulse wave detector 20 Control part 28 Pulsation detection processing circuit 30 Second alignment light source 35 CCD camera

Claims (3)

In a non-contact tonometer that detects a pulse wave of a subject and measures intraocular pressure in association with the detected pulse wave, a face support unit that supports the face of the subject, and the face support unit A pulse wave detector, an eye detection unit for irradiating a light beam to the eye to be examined and receiving reflected light thereof to detect the eye to be examined; and a detection result from the pulse wave detector based on a detection result by the eye detection unit. And a signal acquisition means for starting acquisition of a pulse wave detection signal. 2. The non-contact tonometer according to claim 1, wherein the acquisition start of the pulse wave detection signal by the signal acquisition means includes an adjustment start of detection sensitivity of the pulse wave detection signal output from the pulse wave detector. Non-contact tonometer. The eye detection unit according to claim 1 uses an alignment light beam for forming an alignment index on the cornea as a light beam to be irradiated to the eye, and the eye to start measurement based on the index formed on the eye cornea A non-contact tonometer characterized by detecting whether or not it is ready.

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