JP3881566B2 - 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 spraying fluid onto a subject's eye and detecting the deformation state of the subject's cornea.
[0002]
[Prior art]
The intraocular pressure has temporal fluctuations synchronized with blood pulsation (pulse wave). It is unclear which point in the pulsation change is being measured when measured randomly in time with a non-contact tonometer. When the number of measurements is small, although the intraocular pressure is actually high, the lowest point in the intraocular pressure fluctuation is measured, and the increase in intraocular pressure may be overlooked. For this reason, a non-contact tonometer is proposed that detects pulsation with the forehead, finger, etc., synchronizes with the desired phase position of the pulsation, and further starts an intraocular pressure measurement after obtaining an alignment completion signal for the eye to be examined. ing.
[0003]
[Problems to be solved by the invention]
However, when starting the measurement by synchronizing the phase position where the pulsation is expected and the alignment completion signal, there is a problem that it is difficult to start the measurement if the pulsation signal is not obtained even if the alignment completion signal is obtained. It was. Considering intraocular pressure measurement with pulsation synchronization as a priority, sufficient pulsation may not be obtained depending on the subject, making synchronization measurement with completion of alignment more difficult.
[0004]
In view of the above-mentioned problems of the prior art, the present invention avoids a state where it is difficult to start intraocular pressure measurement in the case of a subject who cannot obtain sufficient pulsation, and can perform the intraocular pressure measurement smoothly. The technical problem is to provide a tonometer.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) A fluid ejecting means for ejecting fluid from the nozzle to the eye to be examined, a pulsation detecting means for detecting the pulsation of the subject, and an alignment detecting means for detecting an alignment completion state between the eye to be examined and the nozzle, In the non-contact tonometer that starts the intraocular pressure measurement by operating the fluid ejection unit based on the pulsation signal detected by the pulsation detection unit and the alignment signal detected by the alignment detection unit, the pulsation detection unit A determination unit that determines whether or not the detected pulsation signal satisfies a predetermined condition, and a pulsation signal that is synchronized with the pulsation when a pulsation signal that satisfies the predetermined condition is not obtained within a predetermined period based on the determination unit. Mode switching means for canceling the measured intraocular pressure and switching to a mode for performing intraocular pressure measurement based on the alignment signal.
(2) The non-contact tonometer according to (1), further comprising display means for displaying that a pulsation satisfying the predetermined condition is obtained based on a pulsation signal detected by the pulsation detection means. To do.
(3) The non-contact tonometer of (1) is characterized by comprising display means for displaying that the mode is switched by the mode switching means.
(4) In the non-contact tonometer of (1), when the pulsation detecting unit further determines that the pulsation satisfies a predetermined condition by the determining unit, the intraocular pressure is again based on the pulsation signal and the alignment signal. Returning means for returning to the mode for starting measurement is provided.
(5) The mode switching means of (1) performs intraocular pressure measurement synchronized with pulsation when a pulsation signal satisfying the predetermined condition is not obtained more than a predetermined number of times within a predetermined period based on the determination means. It cancels and it switches to the mode which performs intraocular pressure measurement based on the said alignment signal.
(6) The non-contact tonometer of (1) is characterized by comprising output means for adding the presence or absence of pulsation synchronization to the measurement result obtained by measuring the intraocular pressure and outputting the result.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a present Example is described based on drawing. FIG. 1 is a diagram showing a side view of a fluid ejection mechanism of a non-contact tonometer and a main part of a 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, the piston 2 is moved upward along the cylinder 1 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). 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.
[0007]
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.
[0008]
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, a signal detection processing circuit 27 for the CCD camera 35, a pulsation detection processing circuit 28 for the pulsation detector 18, a drive circuit 23 for driving the rotary solenoid 3, measurement data, measurement control conditions, etc. A memory 24 for storing is connected. An input unit 25 includes a measurement mode selection switch 25a and the like. Reference numeral 25b denotes a measurement start switch.
[0009]
In order to detect the subject's pulsation, the pulsation detector 18 is attached to a forehead pad 17 provided in a face support unit 16 for supporting the subject's face as shown in FIG. In the present embodiment, the pulsation detector 18 is provided on the forehead pad 17 in order to obtain a phase substantially the same as the phase of pulsation fluctuation in the eyeball. However, the pulsation detector 18 is located at a position in contact with the face of the subject such as a chin rest. It may be provided.
[0010]
The pulsation detector 18 includes a light emitting part and a light receiving part. The light emitting part is a light emitting diode (LED) having a narrow emission wavelength band at a near infrared wavelength corresponding to the absorption spectrum of blood hemoglobin, and the light receiving part is a photodiode. is there. Blood hemoglobin has a strong absorption spectrum for light in a certain wavelength band. Since the reflected light of the living body when irradiated with light in this wavelength band changes according to the amount of hemoglobin that changes with the change in the volume of the blood vessel, the intensity of this reflected light is changed to an electrical signal to detect pulsation. Since blood hemoglobin has a wide absorption spectrum not only in the near infrared region but also in the visible region, a white LED may be used as the light emitting unit. In this case, it is preferable that the light receiving part has sensitivity in a wide wavelength region such as a photoconductive element.
[0011]
In FIG. 2, reference numeral 15 denotes a measuring unit on which a fluid ejecting mechanism and an optical system to be described later are arranged. The movable table 14 is moved by operating the joystick 19, and the measurement unit 15 is moved up and down by operating the rotary knob of the joystick 19.
[0012]
FIG. 3 is a principal part diagram of the optical system of the non-contact tonometer. The eye image illuminated by the infrared illumination light source 30 forms an image on the CCD camera 35 via the beam splitter 31, the objective lens 32, the beam splitter 33 and the filter 34. The filter 34 transmits light from the light source 30 and the light source 40 for alignment, and has an opaque characteristic 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.
[0013]
Reference numeral 40 denotes an alignment infrared LED. The infrared light projected via the projection lens 41 is reflected by the beam splitter 31 and projected onto the eye to be examined from the front. The corneal bright spot formed at the apex of the cornea by the LED 40 forms an image on the CCD camera 35 via the beam splitter 31 to the filter 34 and is used for alignment detection in the vertical and horizontal directions.
[0014]
Reference numeral 45 denotes a fixation target projection LED. The 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. The examiner performs the measurement while fixing the fixation target 46 to the eye to be examined.
Reference numeral 50 denotes an infrared LED for detecting corneal deformation. The light emitted from the LED 50 is made into a substantially parallel light beam by the collimator lens 51 and projected onto the cornea of the eye to be examined. The light reflected by the cornea passes through a 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 a beam splitter 54 and passes through a pinhole plate 55 to detect light. The light is received by the device 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).
[0015]
The corneal deformation detection optical system also serves as a part of the working distance detection optical system, and the light projected from the LED 50 and reflected by the cornea forms an index image that is a virtual image of the LED 50. The light of 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 to be examined (cornea) moves in the working distance direction, the index image by the LED 50 also moves on the one-dimensional position detection element 57, so the control unit 20 operates the working distance information based on the output signal from the one-dimensional position detection element 57. Get.
[0016]
The operation of the non-contact tonometer having the above configuration will be described. The automatic measurement mode of pulsation synchronization is selected by the selection switch 25a. The examiner instructs the subject so that the forehead of the subject is in contact with the forehead pad 17 and measures the pulsation of the subject with the pulsation detector 18 attached to the forehead pad 17. The pulsation detector 18 converts the subject's pulsation into an electrical signal and sends it to the pulsation detection processing circuit 28. The pulsation waveform signal detected by the pulsation detection processing circuit 28 is input to the control unit 20. The control unit 20 determines whether the usable condition is satisfied for the input pulsation waveform signal, that is, whether sufficient pulsation is stably obtained as follows.
[0017]
In determining the usable condition of the pulsation waveform signal, the detection time of the pulsation peak (the pulsation peak is determined from the rising slope of the waveform signal, the signal level, etc.) and the pulsation detection peak height are used. Either of these may be used, but the determination with higher accuracy can be made by using both. As shown in FIG. 5, the detection time (cycle) from the first pulsation peak to the second pulsation peak for three periods of the pulsation waveform signal sequentially obtained from the start of the pulsation measurement is T1, The detection time (cycle) from the pulsation peak to the third pulsation peak is T2. Here, when the change time Th = | T1-T2 | of both becomes Th> 10 ms, it is considered as a time error (unusable) of the pulsation waveform signal.
[0018]
The first pulsation peak height (height from the bottom) is P1, the second pulsation peak height is P2, and the third pulsation peak height is P3. Then, each peak fluctuation rate is calculated as Pa = P1 / P2, Pb = P2 / P3, and Pc = P1 / P3. When all of Pa, Pb, and Pc do not fall within the range of 0.9 to 1.1, it is determined that the peak fluctuation is large, and a pulsation peak error (unusable) of the pulsation waveform signal is determined.
If the pulsation waveform signal satisfies the above usable conditions, the control unit 20 obtains the pulsation phase from the sampling data (preferably obtained from the average of the pulsation waveforms that can be sampled), and the intraocular pressure that is synchronized with a predetermined phase position. Calculate the measurement time.
[0019]
FIG. 4 shows an example of measuring intraocular pressure in synchronization with a peak in the pulsation phase. S1 indicates the timing of the peak P of the pulsation phase, which is sequentially obtained assuming that it comes after the phase period Ta from the pulsation peak immediately before the usable condition is satisfied. S2 indicates the intraocular pressure measurement timing at which the signal S3 for driving the solenoid 3 is output. At this timing S2, after the solenoid drive signal S3 is output, the applanation is detected until the cornea is flattened by the injection of compressed air from the nozzle 6 (until the peak of the applanation signal Q output from the photodetector 56). It is obtained at the timing determined from the timing S1 by the time Tapl.
[0020]
After determining that the pulsation waveform signal for three cycles satisfies the usable condition as described above from the start of pulsation detection, if the pulsation peak for one cycle can be detected, the pulsation peak height Pn is the above-described value. It is also possible to determine that it can be used when it is within a range of ± 10% with respect to the average peak height of P1, P2, and P3, and to determine the next timing S1.
[0021]
The applanation detection time Tapl will be described. In the first measurement, the applanation detection time Tapl is set using an average intraocular pressure value. If the intraocular pressure of the eye to be examined can be predicted to some extent, the intraocular pressure value is input from the input unit 25. The applanation detection time Tapl is set. In the second and subsequent measurements, the intraocular pressure measurement timing S2 is obtained using the applanation detection time Tapl in the previous measurement.
[0022]
In the automatic measurement mode of pulsation synchronization, a “SAMP” mark 61 is displayed on the upper left of the monitor 36 screen as shown in FIG. When a pulsation peak that satisfies the usable condition is obtained, the heart mark 63 is lit for 0.5 seconds. If the pulsation peak is continuously obtained, the heart mark 63 appears to blink. If the heart symbol 63 is periodically blinked, it can be understood that pulsation is stably obtained, and pulsation synchronization can be measured.
[0023]
The examiner moves the measurement unit 15 by operating the joystick 19 or the like based on the alignment information displayed on the monitor 36 to perform alignment adjustment. The alignment adjustment in the vertical and horizontal directions is performed so that the corneal bright spot 80 formed by the LED 40 comes to the center of the reticle 81 displayed on the monitor 36. The alignment adjustment in the working distance direction is performed according to a distance guidance mark (not shown) displayed based on the working distance information obtained from the one-dimensional position detection element 57. For details of the alignment adjustment, refer to Japanese Patent Application Laid-Open No. 7-23907 by the present applicant. In addition, automatic alignment that controls the movement of the measurement unit 15 based on the detection information of the alignment index image may be used.
[0024]
The control unit 20 obtains the alignment completion signal R when the index image detected by the one-dimensional position detection element 57 and the index image detected by the CCD camera 35 are within a predetermined allowable range. Then, when the alignment completion signal R and the intraocular pressure measurement timing S2 are synchronized, a solenoid drive signal S3 is output and measurement is performed. That is, the control unit 20 applies electric charges as operable driving energy to the rotary solenoid 3 through the driving circuit 23 to drive it.
[0025]
After the subject's pulsation measurement is started (when the subject puts the forehead on the pulsation detector 18, the pulsation waveform signal changes greatly, so that the start of the pulsation measurement is known), and a predetermined period (5 seconds) or more has elapsed However, if the pulsation waveform signal that satisfies the above-mentioned usable conditions cannot be obtained, the control unit 20 cancels the automatic measurement mode of pulsation synchronization, and a “NO SAMP” mark is displayed at the upper left of the monitor 36 screen as shown in FIG. 62 is displayed. In this state, if only the alignment completion signal R is obtained, this is used as a measurement execution instruction signal, and the solenoid drive signal S3 is output to perform measurement. In other words, the automatic measurement mode based on only alignment completion without using pulsation synchronization is automatically switched. After that, when a pulsation waveform signal satisfying the usable conditions described in FIG. 5 is obtained, the pulsation synchronization automatic measurement mode is automatically restored.
[0026]
In addition, even if the pulsation waveform signal that satisfies the usable conditions cannot be obtained while the pulsation synchronization automatic measurement mode continues, the pulsation synchronization automatic measurement mode is canceled and the automatic measurement mode based only on the alignment completion signal is automatically selected. Switch to. This switching is performed when a pulsation waveform signal satisfying the usable condition is never obtained even after a predetermined period (5 seconds) has elapsed from the latest pulsation peak satisfying the usable condition. The predetermined time period of 5 seconds is variable and can be arbitrarily set before measuring the intraocular pressure. Further, if the pulsation cycle is obtained by the first sampling, it may be determined according to the pulsation of the subject, such as a period of three cycles. In the above description, the mode is switched when a pulsating waveform signal satisfying the usable condition is never obtained within a predetermined period. However, the number of times satisfying the usable condition within the predetermined period can be arbitrarily set in advance.
[0027]
Then, again, a pulsation waveform signal that satisfies the usable condition (in this case, the applicability of use for one period of the pulsation waveform signal is determined based on the pulsation peak as described above) can be obtained. In this case, the mode automatically returns to the pulsation synchronous automatic measurement mode. It should be noted that, during a predetermined period (5 seconds) from the most recent pulsation peak for determining whether to cancel the automatic measurement mode of pulsation synchronization, the intraocular pressure measurement tiling obtained from the pulsation waveform signal satisfying the usable condition regardless of the pulsation waveform signal S2 may be output predictively for each period Ta. Thus, even if the pulsation is interrupted for a period of time due to the subject's fine movement or the like, the measurement can be executed without missing the synchronization timing with the completion of alignment.
[0028]
When the solenoid drive signal S3 is output, the piston 2 is raised by driving the rotary solenoid 3, the air in the air compression chamber 11 is compressed by the piston 2, and the compressed air is blown from the nozzle 6 toward the cornea of the eye E to be examined. Attached. The cornea of the eye E is gradually deformed by the blown compressed air, and when the cornea reaches a flat state, the maximum amount of light enters the photodetector 56. The output signal from the photodetector 56 and the output signal from the pressure sensor 12 are sequentially processed and input to the control unit 20. The control unit 20 uses the time when the applanation signal Q output from the photodetector 56 shows a peak, the pressure Pr obtained at this time, or the average pressure obtained before and after that time, to determine a predetermined value. The intraocular pressure value is obtained by the intraocular pressure conversion formula.
[0029]
When the measurement result is obtained, the intraocular pressure measurement value is displayed on the monitor 36. FIG. 7 shows an example of the screen at this time. The left and right eye intraocular pressure measurement results are displayed on the screen. On the right side of each measurement value, when the intraocular pressure measurement is synchronized at the peak position of the pulsation waveform signal, a “P” mark is displayed, and the intraocular pressure measurement is performed with a synchronization error without being synchronized with the pulsation. In such a case, an “E” mark is displayed (the “E” mark may be omitted). In addition, when the intraocular pressure is measured at the bottom position of the pulsation waveform and the synchronous measurement is performed at the bottom position of the pulsation waveform signal, a “B” mark is displayed beside the measurement value. Similarly, when printing out with a printer (not shown), these marks are printed together with the intraocular pressure measurement result. The same applies when outputting data to an external computer.
[0030]
The numerical values, the number of sample pulsations, the time for determining the mode switching, etc. in the above-described pulsation waveform signal availability determination are merely examples, and it goes without saying that they can be changed in the usage situation.
[0031]
【The invention's effect】
As described above, according to the present invention, in the case of a subject who cannot obtain sufficient pulsation, a state in which intraocular pressure measurement cannot be easily started is avoided, and measurement in an appropriate alignment state is smoothly performed. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic side configuration and a control system of an air compression mechanism.
FIG. 2 is a diagram showing the appearance of the apparatus and the installation location of the pulsation detector.
FIG. 3 is a diagram showing an optical system of the apparatus.
FIG. 4 is a diagram illustrating timing of pulsation and intraocular pressure measurement.
FIG. 5 is a diagram for explaining a usable condition of a pulsation waveform signal.
FIG. 6 is a diagram showing a screen display of the apparatus.
FIG. 7 is a diagram showing a screen display of the apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder part 2 Piston 3 Rotary solenoid 12 Pressure sensor 18 Pulsation detector 20 Control part 23 Drive circuit 28 Pulsation detection processing circuit 35 CCD camera 36 Monitor 50 LED
56 Photodetector 57 One-dimensional position detection element

Claims (6)

A fluid ejecting means for ejecting a fluid from the nozzle to the eye to be examined; a pulsation detecting means for detecting a pulsation of the subject; and an alignment detecting means for detecting an alignment completion state between the eye to be examined and the nozzle; In the non-contact tonometer that starts the intraocular pressure measurement by operating the fluid ejection means based on the pulsation signal detected by the means and the alignment signal detected by the alignment detection means, the pulsation detection means detects Determining means for determining whether or not the pulsation signal satisfies a predetermined condition; and when the pulsation signal satisfying the predetermined condition is not obtained within a predetermined period based on the determination means, the eye synchronized with the pulsation Non-contact type eye comprising: mode switching means for canceling pressure measurement and switching to a mode for performing intraocular pressure measurement based on the alignment signal Total. 2. The non-contact tonometer according to claim 1, further comprising display means for displaying that a pulsation satisfying the predetermined condition is obtained based on a pulsation signal detected by the pulsation detecting means. Tonometer. 2. The non-contact tonometer according to claim 1, further comprising display means for displaying that the mode is switched by the mode switching means. 2. The non-contact tonometer according to claim 1, wherein when the pulsation detecting means further determines that the pulsation satisfies a predetermined condition by the determining means, the tonometry is started again based on the pulsation signal and the alignment signal. A non-contact tonometer comprising return means for returning to the mode to perform. The mode switching means of claim 1 cancels the intraocular pressure measurement synchronized with the pulsation when the pulsation signal satisfying the predetermined condition is not obtained more than a predetermined number of times within a predetermined period based on the determination means, A non-contact tonometer that switches to a mode for measuring intraocular pressure based on the alignment signal. 2. The non-contact tonometer according to claim 1, further comprising output means for outputting the measurement result obtained by measuring the intraocular pressure by adding the presence or absence of pulsation synchronization.

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