JP2005102991A - Non-contact type tonometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-contact type tonometer permitting stable measurement of the ocular tension by reducing the burden on a subject, without excess/lack of blowing of compressed air even if the signal waveform from a deformation detection system is varied according to the difference of the reflectance of the cornea of an examined eye or the shape of the cornea. <P>SOLUTION: The tonometer comprises a fluid injection means for blowing a fluid to the cornea of the examined eye with the pressure variable in time, a pressure detecting means mounted on the fluid injection means, a light receiving means for detecting the quantity of reflection light from a projection optical system for projecting a luminous flux for measurement to the cornea of the examined eye and from the cornea of the examined eye, a first time detecting means for detecting the time for taking the peak value from the output waveform from the light receiving means, a second time detecting means for detecting the time for taking the peak value from the output waveform from the pressure detecting means, and a control means for stopping the driving of the fluid injection means by detecting that the output value of the light receiving means exceeds a prescribed value. The prescribed value for the next tonometry is determined based on the result of detection by the first time detecting means and the second time detecting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-contact tonometer.

  A conventional non-contact tonometer moves a piston in a cylinder by rotating a rotary solenoid, compresses air in the cylinder, blows compressed air on the cornea of the eye to be examined, and projects measurement light from a light source onto the cornea. When the subject's eye cornea has a predetermined curvature, it is received by the photosensor of the light receiving means provided so that the amount of reflected light from the cornea is maximized, and the peak of the output signal from the photosensor is detected. Thus, a predetermined deformation of the cornea is detected, and the pressure in the cylinder at that time is measured and converted into an intraocular pressure value.

  Normally, this type of non-contact tonometer stops driving the rotary solenoid when the peak of the output signal from the photosensor is detected, but in reality the piston does not stop immediately but moves inside the cylinder. It moved due to inertia, and excessive compressed air was blown onto the cornea of the eye to be examined. An invention for solving this problem is disclosed in Patent Document 1. According to the present invention, when the output signal from the photosensor exceeds a predetermined threshold before the peak of the output signal from the photosensor is detected, the rotary solenoid is stopped to reduce the air pressure applied to the eye to be examined. , Reduce the burden on the subject.

Japanese Examined Patent Publication No. 3-51409

  However, as in the above conventional example, when the output signal from the photosensor exceeds a predetermined threshold before the peak of the output signal from the photosensor is detected, the rotary solenoid is stopped and applied to the eye to be examined. Even if the air pressure is reduced, there is an individual difference in the reflectivity of the eye cornea, so even if the rotary solenoid is stopped when the output signal from the photosensor reaches a predetermined threshold, the reflectivity of the cornea In the case of a low eye to be examined, the predetermined threshold value for the peak value of the output signal from the photosensor becomes high, so compressed air will be blown more than necessary. Since the predetermined threshold value with respect to the peak value of the output signal from the output becomes low, the blowing of compressed air becomes insufficient, resulting in a decrease in measurement accuracy. Changes to the compression air pressure differs by individual differences of the corneal shape and the corneal thickness, may result in excessive or insufficient blowing compressed air, the measurement accuracy is disadvantageously reduced.

  The present invention has been made in view of the above problems, and the object of the present invention is that even if the signal waveform of the deformation detection system changes due to the difference in reflectance of the eye cornea or the shape of the eye cornea, the compressed air An object of the present invention is to provide a non-contact tonometer that can reduce the burden on the subject and can stably measure the intraocular pressure without excessive or insufficient spraying.

  In order to achieve the above object, a first aspect of the present invention is directed to a fluid ejecting means for deforming the cornea by spraying a fluid onto a subject's cornea with a temporally variable pressure, and a pressure detecting means provided in the fluid ejecting means. A projection optical system for projecting the measurement light beam onto the eye cornea, a light receiving means for detecting the amount of light reflected from the eye cornea, and a first time detecting means for detecting a time at which a peak value is obtained from an output waveform from the light receiving means A second time detecting means for detecting a time at which a peak value is obtained from an output waveform from the pressure detecting means, and driving the fluid ejecting means by detecting that the output value of the light receiving means exceeds a predetermined value. Control means for stopping the control, and a predetermined value at the time of the next intraocular pressure measurement is determined from the results of the first time detection means and the second time detection means.

  According to a second aspect of the present invention, there is provided a fluid ejecting means for deforming the cornea by spraying a fluid onto the eye cornea with a variable pressure in time, a pressure detecting means provided in the fluid ejecting means, and a measurement for applying to the eye cornea From a projection optical system for projecting a light beam, a light receiving means for detecting the amount of light reflected from the cornea of the eye to be examined, a first time detecting means for detecting a time when a peak value is obtained from an output waveform from the light receiving means, and the pressure detecting means A second time detecting means for detecting a time at which a peak value is taken from the output waveform, and a control means for stopping the driving of the fluid ejecting means by detecting that the output value of the light receiving means exceeds a predetermined value; Display means for displaying a measurement result, and displaying on the display means when the time difference obtained from the results of the first time detection means and the second time detection means is smaller than a predetermined value.

  According to the present invention, a non-contact tonometer includes a fluid ejecting unit that deforms the cornea by spraying fluid onto the eye cornea with a variable pressure in time, a pressure detecting unit provided in the fluid ejecting unit, A projection optical system for projecting a measurement light beam onto the optometry cornea, a light receiving means for detecting the amount of light reflected from the eye cornea to be examined, a first time detection means for detecting a time at which a peak value is obtained from an output waveform from the light receiving means, Second time detection means for detecting a time at which a peak value is obtained from the output waveform from the pressure detection means, and stopping the fluid ejection means by detecting that the output value of the light receiving means exceeds a predetermined value Control means, and by determining a predetermined value at the time of the next intraocular pressure measurement from the results of the first time detection means and the second time detection means, regardless of the difference in the reflectance of the eye cornea, etc. Appropriate compressed air without excess or deficiency It is possible to blow the film, and reduce the load on the subject, and, thereby enabling stable tonometry.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an external view of a non-contact tonometer of the present invention.

  On the surface operated by the examiner, the monitor 1 displays the measured values and the eye image, the trackball 2 and the roller 3 for roughly aligning the measuring unit with the eye, the printer print switch, and the measurement start A switch panel 4 and a printer 5 on which switches and selection setting switches are arranged are arranged. The subject can measure by placing his / her face on a face receiving portion (not shown) on the opposite side of the surface operated by the examiner and placing the eye to be examined in front of the objective portion of the measuring portion.

  With respect to the eye E, the optometry unit 6 can be moved in a three-dimensional direction by driving three-axis motors 35, 36, and 37 on the left, right, up, down, and front and back, and the optometry unit 6 is positioned with respect to the eye to be examined by electric drive It can be adjusted.

  FIG. 2 shows an internal configuration of the optometry unit 6.

  A test eye observation system is arranged on the optical axis L so as to face the test eye E. An observation light beam of the eye E illuminated by a light beam from an anterior segment illumination light source (not shown) passes through the perforated window 10, the outside of the nozzle 12, the lens 11, and the dichroic mirror 13 to be described later. Through the aperture 14 c and the lens 15, the light is guided onto the light receiving surface of the CCD camera 16 to form an image.

  The alignment optical system includes an alignment light projection system and an alignment light receiving system. The light beam emitted from the light source 21 passes through the projection lens 20, the dichroic mirror 19, the half mirror 18, and the lens 17, is reflected by the dichroic mirror 13, forms an image once in the nozzle 12, and reaches the eye E to be examined. These constitute an alignment light projection system. The light beam reflected by the subject's eye cornea passes through the perforated window 10 and the lens 11, partially passes through the dichroic mirror 13, and is split into two light beams by the prisms 14 a and 14 b of the alignment prism diaphragm 14, and is received by the CCD camera 16. Led to the face. These constitute an alignment light receiving system.

  Here, the alignment prism diaphragm 14 is as shown in FIG. The observation light beam passes through the central opening 14c, and the alignment light receiving system light beam is divided into two light beams by the openings 14a and 14b that transmit only the wavelength of the light source 21, and enters the prisms 14a and 14b. Is deflected downward, and the light beam is deflected upward by the prism 14b.

  When the eye E and the optometry unit 6 are in an appropriate positional relationship, the spot image of the light source 21 is formed as two bright spots P1 and P2 in a vertical line near the center on the CCD camera 16. The anterior segment image at that time is as shown in FIG. 4A. When the working distance deviates back and forth, the two bright spots P1 and P2 move relative to each other in the left and right directions with reference to the bright spot position at the proper working distance, as shown in FIGS. 4B and 4C, respectively. When the tonometry part 6 moves in the vertical and horizontal directions with respect to the eye E, the relative positions of the two bright spots P1 and P2 are changed in the vertical and horizontal directions in accordance with the amount of deviation of the two bright spots P1 and P2. Without moving.

  The corneal deformation detection system includes a measurement light projection system and a measurement light reception system.

  The light beam emitted from the light source 21 passes through the projection lens 20, the dichroic mirror 19, and the half mirror 18, is converged by the lens 17, reflected by the dichroic mirror 13, and once imaged in the nozzle 12 to be covered. Reach optometry E. These constitute a measuring light projection system.

  The light beam reaching the eye E to be examined by the measurement light projection optical system is reflected by the cornea, reflected by the dichroic mirror 13 through the perforated window 10 and the lens 11, condensed by the lens 17, and then collected by the half mirror 12. It is reflected and reaches an aperture 22 having a pinhole. Then, the light beam that has passed through the pinhole is received by the photosensor 23. These constitute a measurement light receiving system. The aperture 22 having the pinhole was emitted from the measurement light projection optical system when the cornea of the eye E deformed by compressed air emitted from a fluid ejection system described later has a predetermined curvature. It is arranged at a position optically conjugate with the cornea reflection image of the light beam. That is, when the cornea of the eye E has a predetermined curvature, the amount of light received by the photosensor 23 is maximized.

  The light beam emitted from the fixation LED 24 is reflected by the dichroic mirror 19, passes through the half mirror 18, becomes substantially parallel light by the lens 17, is reflected by the dichroic mirror 13, passes through the nozzle 4, and reaches the eye E to be examined. Led. These constitute a fixation target projection system.

  A pressure sensor 30 that detects internal pressure is attached to a compression chamber 29 surrounded by the lens 11, the dichroic mirror 13, and the lens 17. The compression chamber 29 is connected to a cylinder 27 through a tube 28. A piston 26 is contained in the cylinder 27, and the piston 26 is connected to a rotary solenoid 25. Thus, a fluid ejection system is configured.

  FIG. 5 is an electrical block diagram of the non-contact tonometer.

  A switch panel 4 on which a measurement switch, a print start switch, and the like are arranged, a trackball 2 for roughly aligning the measurement unit with the eye to be examined, a rotary encoder built in the roller 3, and a printer 5 for printing measurement results It is connected to the CPU 31 port.

  A video signal of the anterior segment image captured by the CCD camera 16 is converted into digital data by the A / D converter 32 and stored in the image memory 33. The CPU 31 performs image processing for extracting two alignment bright spot images P1 and P2 based on the image data stored in the image memory 33, and detects the relative position of the eye E to the optometry unit 6. The video signal of the anterior segment image captured by the CCD camera 16 is combined with the signal from the character generator 34 and displayed on the monitor 1 together with the alignment mark and the measured value.

  The left / right motor 35, the up / down motor 36, and the front / rear motor 37 are connected to a motor driver 38, and input according to the input of the rotary encoders of the trackball 2 and the roller 3 and the relative position of the eye E to the optometry unit 6 during auto-alignment operation. And driven by a command from the CPU 31.

  The rotary solenoid 25 is connected to a driver 43 and is driven by a command from the CPU 31. The output from the pressure sensor 30 is input to the analog switch 39, and the output from the photosensor 23 is also input to the analog switch 39. The analog switch 39 is selected from the two inputs by the CPU 31. One signal is output to the A / D converter 42.

  The measurement operation in the non-contact tonometer configured as described above will be described based on the flowchart shown in FIG.

  First, the examiner operates the trackball 2 and the roller 3 until two alignment bright spots can be confirmed on the monitor 1, and drives the left, right, up, down, front and back motors 35, 36, and 37, and the eye E to be examined. Rough alignment adjustment of the optometry unit 6 of the apparatus is performed, and then the measurement switch on the switch panel 4 is pressed. Then, the CPU 31 starts an auto alignment operation. The auto alignment operation is performed in steps 1 to 5.

  In step 1, the video signal of the anterior segment image of the eye E to be examined photographed by the CCD camera 16 is converted into digital data by the A / D converter 32 and is taken into the image memory 33. Next, in step 2, the CPU 31 performs image processing from the image data in the image memory 33 fetched in step 1, and detects the positions of the two alignment bright spot images P1 and P2. In step 3, the amount of misalignment in each of the left, right, up, down, and front and rear directions is calculated from the positions of the two detected bright spot images P1 and P2.

  In step 4, it is determined whether or not the alignment deviation amount is within a predetermined range that can be measured. If it is out of the range, the process proceeds to step 5, and the left, right, upper, lower, and front and rear motors 35, 36, 37 is driven to move the optometry unit 6. These auto-alignment operations from step 1 to step 5 are repeated until it is determined in step 4 that the amount of misalignment is within a predetermined range that can be measured.

  Next, when the auto-alignment is completed, the process proceeds to step 6 and the driving of the rotary solenoid 25 is started via the driver 43 according to a command from the CPU 31. The piston 26 moves in the cylinder 27 with the start of driving, and air is sent into the compression chamber 29 connected via the tube 28. The sent air is compressed, passes through the nozzle 12, and is blown to the eye E. The cornea of the eye E is deformed.

  In the next step 7, the input of the analog switch 39 is alternately switched, in step 8, the internal pressure signal in the compression chamber 29 is sampled, and in step 9, the corneal deformation signal is sampled a set number of times at a predetermined sampling period, They are stored in the memory 44 in chronological order. In the sampling of the internal pressure signal in step 8, the CPU 31 switches the input of the analog switch 39, inputs the signal of the pressure sensor 30 to the A / D converter 42, performs A / D conversion, and stores the digital data in the memory 44. To do. In sampling of the corneal deformation signal in step 9, the CPU 31 switches the input of the analog switch 39, inputs the signal of the photosensor 23 to the A / D converter 42, performs A / D conversion, and stores the digital data in the memory 44. Store.

  In step 10, the number of samplings is determined.

  In step 11, the digital data of the photo sensor 23 is compared with the set threshold value So1 for stopping the driving of the rotary solenoid. If the threshold value So1 is exceeded, the driving of the rotary solenoid 25 is stopped in step 12. Let When it is determined in step 10 that the sampling has been completed a predetermined number of times, the process proceeds to step 13 where the peak of the deformation signal is detected from the data of the deformation signal stored in the memory 44, and the internal pressure corresponding to the peak of the deformation signal is detected in step 14. The intraocular pressure value of the eye to be examined is obtained by a conversion formula prepared in advance based on the signal data.

  Next, in step 15, the CPU 31 determines whether the intraocular pressure measurement has been performed a predetermined number of times. If the intraocular pressure measurement has not been performed a predetermined number of times, the process proceeds to step 16. In step 16, a time t 1 at which the deformation signal peaks is detected from the deformation signal data stored in the memory 44. In step 17, a time t 2 at which the internal pressure signal peaks from the internal pressure signal data stored in the memory 44. Is detected. In step 18, a difference Δt between the time t2 when the internal pressure signal peaks and the time t1 when the deformation signal peaks is calculated, and in step 19, it is determined whether the difference Δt is within an allowable range by comparison with a predetermined time. To do. When it is determined that the difference Δt is not within the allowable range, the threshold So1 of the stop level of the rotary solenoid 25 is reset so that Δt is within the allowable range in Step 20, and the process proceeds to Step 1 to perform the next intraocular pressure measurement operation. To start. If it is determined in step 20 that Δt is within the allowable range, the process proceeds to step 1 to start the next intraocular pressure measurement operation.

  If it is determined in step 15 that the intraocular pressure measurement has been performed a predetermined number of times, the measurement operation is terminated, the measurement result is displayed on the monitor 1 and printed on the printer 5.

  FIG. 7 shows the outputs of the pressure sensor 30 and the photosensor 23 when the amount of compressed air sprayed by the fluid ejection system is appropriate. The horizontal axis represents time t, and the vertical axis represents outputs from the pressure sensor 30 and the photosensor 23.

  Ph (t) represents the output waveform of the photosensor 23, and Prs (t) represents the output waveform of the pressure sensor 30. So1 is a threshold value for stopping the driving of the rotary solenoid 25. When the output value Ph (t) of the photosensor 23 exceeds the threshold value So1, the driving of the rotary solenoid 25 is stopped. The time t1r at which the peak value of the output waveform Ph (t) of the photosensor 23 when the amount of compressed air blowing is appropriate, and the time t2r at which the peak value of the output waveform Prs (t) of the pressure sensor 30 is taken. Is the difference Δtr.

  FIG. 8 shows the outputs of the pressure sensor 30 and the photosensor 23 when measuring the eye E with high corneal reflectivity.

  When the reflectivity of the cornea is high, the output value Ph (t) of the photosensor 23 exceeds the threshold value So1 even though the curvature of the cornea is not so much deformed by the compressed air by the fluid ejection system. The drive of the rotary solenoid 25 is stopped, and the cornea cannot be deformed to a predetermined curvature. In this case, if the difference between the time t1s at which the peak value of the output waveform Ph (t) of the photosensor 23 takes and the time t2s at which the peak value of the output waveform Prs (t) of the pressure sensor 30 takes is Δts, the compression is performed. It is smaller than Δtr when the amount of air blowing is appropriate.

  FIG. 9 shows the outputs of the pressure sensor 30 and the photosensor 23 when measuring an eye to be examined having a low corneal reflectivity or a corneal eye that is difficult to deform with weak compressed air.

  When the reflectivity of the cornea is low, the output value Ph (t) of the photosensor 23 does not exceed the threshold value So1 even though the curvature of the cornea is deformed to some extent by the compressed air by the fluid ejection system. In the case of a corneal eye that is difficult to deform with weak compressed air, the timing for stopping the driving of the rotary solenoid 25 is delayed, and compressed air is blown onto the eye E more than necessary. In this case, if the difference between the time t1h at which the peak value of the output waveform Ph (t) of the photosensor 23 takes and the time t2h at which the peak value of the output waveform Prs (t) of the pressure sensor 30 takes is Δth, compression is performed. It is larger than Δtr when the air blowing amount is appropriate.

  Therefore, the time t1 when the peak value of the output waveform Ph (t) of the photosensor 23 at the time of the first intraocular pressure measurement is taken and the time t2 when the peak value of the output waveform Prs (t) of the pressure sensor 30 is taken. Δt is obtained as the difference, and the time t1r at which the peak value of the output waveform Ph (t) of the photosensor 23 when the amount of compressed air spray is appropriate and the peak value of the output waveform Prs (t) of the pressure sensor 30 are taken. The difference from the time t2r is compared with Δtr, and the rotary solenoid 25 is driven to set the stop level threshold value So1 so that Δt is substantially equal to Δtr. Appropriate compressed air can be blown onto the subject's eye cornea, so that the load on the subject can be reduced and stable intraocular pressure can be measured.

  The difference between the time t1 when the peak value of the output waveform Ph (t) of the photosensor 23 is taken and the time t2 when the peak value of the output waveform Prs (t) of the pressure sensor 30 is obtained is obtained as Δt. If the value is smaller than the value, the amount of compressed air sprayed is small, so it is judged that the measurement accuracy of the measured intraocular pressure value is low, and a “*” mark is added to the measured value displayed on the monitor 1 to inform the examiner. Anyway.

  The present invention blows compressed air onto the cornea of the eye to be examined and projects measurement light from the light source onto the cornea so that the amount of reflected light from the cornea is maximized when the eye cornea has a predetermined curvature. Light is received by a photosensor of the provided light receiving means, and a predetermined deformation of the cornea is detected by detecting the peak of the output signal from the photosensor, and the pressure in the cylinder at that time is measured to obtain an intraocular pressure value. It can be applied to a non-contact tonometer to be converted.

1 is a perspective view of a non-contact tonometer according to the present invention. It is a block diagram of the measurement part of the non-contact type tonometer according to the present invention. It is a figure of an alignment prism stop. It is a figure which shows the anterior ocular segment image at the time of alignment by alignment light. It is an electrical block diagram of an apparatus. It is a flowchart of an intraocular pressure measurement. It is an output figure of a pressure sensor and a photo sensor. It is an output figure of a pressure sensor and a photo sensor. It is an output figure of a pressure sensor and a photo sensor.

Explanation of symbols

12 Nozzles 16 CCD Camera 21 Light Source 23 Photo Sensor 25 Rotary Solenoid 30 Pressure Sensor 31 CPU
39 Analog switch 42 A / D converter

Claims (2)

  Fluid ejecting means for deforming the cornea by spraying fluid onto the eye cornea with variable pressure in time, pressure detecting means provided in the fluid ejecting means, and a projection optical system for projecting a measurement light beam onto the eye cornea A light receiving means for detecting the amount of reflected light from the eye cornea, a first time detecting means for detecting a time at which a peak value is obtained from the output waveform from the light receiving means, and a peak value from the output waveform from the pressure detecting means. A second time detection means for detecting time; and a control means for stopping the driving of the fluid ejection means by detecting that the output value of the light receiving means exceeds a predetermined value. A non-contact tonometer that determines a predetermined value at the time of the next intraocular pressure measurement from the result of the means and the second time detection means.   Fluid ejecting means for deforming the cornea by spraying fluid onto the eye cornea with variable pressure in time, pressure detecting means provided in the fluid ejecting means, and a projection optical system for projecting a measurement light beam onto the eye cornea A light receiving means for detecting the amount of reflected light from the eye cornea, a first time detecting means for detecting a time at which a peak value is obtained from the output waveform from the light receiving means, and a peak value from the output waveform from the pressure detecting means. Second time detecting means for detecting time; control means for stopping driving of the fluid ejecting means by detecting that an output value of the light receiving means exceeds a predetermined value; and display means for displaying a measurement result A non-contact tonometer is displayed on the display means when the time difference obtained from the results of the first time detection means and the second time detection means is smaller than a predetermined value.

Images