JP2005087581A - Noncontact type tonometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an air quantity to be given to an eye to be examined stably regardless of the difference of reflectance at the cornea of the eye to be examined. <P>SOLUTION: With the received light quantity of an alignment detection means, a level of stopping driving of a pressure means by the detection of the prescribed level of a cornea deformation signal is changed to fix the timing of the stoppage of a pressurizing means regardless of the difference of the cornea reflectance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-contact tonometer.

In the conventional non-contact tonometer, the piston is moved in the cylinder by the rotation of the rotary solenoid, the air in the cylinder is compressed, the compressed air is blown to the cornea of the eye to be examined, and the measurement light is projected from the light source onto the cornea. The reflected light from the cornea is received by a photosensor, etc., and by detecting the peak of the output signal from the photosensor, a predetermined deformation of the cornea is detected, and the pressure in the cylinder at that time is measured to obtain an intraocular pressure value. Convert. Normally, this type of non-contact tonometer does not stop immediately when the rotary solenoid drive stops when the peak of the output signal from the photo sensor is detected, but the piston moves in the cylinder due to inertia, Since excess air is blown to the cornea of the eye to be inspected, the output signal from the photosensor is predetermined before the peak of the output signal from the photosensor is detected, as disclosed in Japanese Patent Publication No. 3-51409. It is known that when the threshold value is exceeded, the driving of the rotary solenoid is stopped to reduce the air pressure applied to the eye to be examined.
JP-B 3-51409

  However, since the reflectance of the eye cornea to be examined varies among individuals, the threshold value of the output signal from the photosensor for stopping the operation of the rotary solenoid is originally large in the cornea with high reflectance and small in the cornea with low reflectance. Although it is necessary, the magnitude of the output signal from the photosensor is not known unless it is measured. If a threshold value for a cornea with low reflectivity is adopted, if the cornea with high reflectivity is measured, the threshold value is low, so it is too early to stop driving the rotary solenoid, so that the predetermined deformation of the cornea cannot be obtained and normal measurement cannot be performed. Since there is a fear, a threshold value for a cornea having a high reflectance is usually adopted. For this reason, when the reflectivity of the cornea is low, the threshold for stopping the driving of the rotary solenoid is relatively larger than that of the cornea having a high reflectivity, so that the timing for stopping the driving of the solenoid is delayed and excess air is removed. There was a problem of spraying.

  An object of the present invention is to provide a non-contact tonometer that can stably reduce the amount of air given to a subject's eye regardless of the difference in reflectance of the subject's eye cornea.

  Alignment detection means that projects an alignment beam onto the subject's eye cornea and detects the reflected light, pressure means that deforms the cornea by spraying fluid onto the eye's cornea with variable pressure over time, and measurement on the eye's cornea A projection optical system for projecting a luminous flux for light, a light receiving means for detecting the amount of light reflected from the eye cornea to be examined, and a deformation detecting means for detecting a predetermined deformation of the cornea by detecting a peak of output from the light receiving means, In a non-contact tonometer having a control means for stopping the driving of the pressurizing means by detecting a predetermined output before the output of the light receiving means reaches a peak, the peak of the light receiving means for stopping the driving of the pressurizing means The predetermined output before reaching is changed in accordance with the amount of light received by the alignment detection means.

  As described above, the alignment detecting means for projecting the alignment light beam on the eye cornea and detecting the reflected light, and the pressure means for deforming the cornea by spraying fluid on the eye cornea with a variable pressure in time. A projection optical system for projecting a measurement beam onto the eye cornea, a light receiving means for detecting the amount of light reflected from the eye cornea, and a deformation for detecting a predetermined deformation of the cornea by detecting a peak of the output from the light receiving means. In a non-contact tonometer having a detecting means and having a control means for stopping the driving of the pressurizing means by detecting a predetermined output before the output of the light receiving means reaches a peak, in order to stop the driving of the pressurizing means The predetermined output before reaching the peak of the light receiving means is changed according to the amount of light received by the alignment detecting means, so that the air pressure stably applied to the eye to be examined can be reduced regardless of the difference in reflectance of the eye cornea. It can be.

(Example 1)
The present invention will be described in detail based on the illustrated embodiments.

  FIG. 1 is an external view of a non-contact tonometer of the present invention. On the surface operated by the examiner, a monitor 1 for displaying measured values and an eye image to be examined, a track ball 2 and a roller 3 for roughly aligning the measuring portion with the eye to be examined, a printer print switch, and a 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 face on a face receiving portion (not shown) on the opposite side to the surface operated by the examiner and placing the eye to be examined in front of the objective portion of the measuring portion.

  The measuring unit 6 can be moved in a three-dimensional direction with respect to the eye E by driving the left, right, up, down, and front and rear three-axis motors 35, 36, and 37, and the measuring unit 6 can be aligned with the eye to be examined by electric drive. It is like that.

  FIG. 2 shows the internal configuration of the measurement unit 6. A test eye observation optical system is arranged on the axis L so as to face the test eye E. The observation image of the eye E passes through the perforated window 10, the outside of the nozzle 12, the lens 11, passes through the dichroic mirror 13, and is guided to the CCD camera 16 through the opening 14 c of the alignment prism diaphragm 14 and the lens 15. In the alignment optical system, the alignment light receiving system is partially shared with the observation optical system. First, the alignment projection system is irradiated 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, is irradiated into the nozzle 12, and travels toward the eye E. The light beam of the alignment light receiving system reflected by the eye cornea is partially transmitted through the perforated window 10 and the lens 11 and partially transmitted through the dichroic mirror 13 and separated into two light beams by the prisms 14a and 14b of the alignment prism diaphragm 14. Guided to the CCD camera 16. The alignment prism diaphragm is as shown in FIG. The observation optical system passes through the central opening 14c, and the alignment light receiving system is incident on the prisms 14a and 14b that transmit only the wavelength of the light source 18. The left prism 14a has the light beam downward, and the right prism 14b has the light beam upward. At an appropriate working distance, the spot image of the light source is formed as two bright spots in a vertical line near the center on the CCD camera 16. The anterior segment image at that time is as shown in FIG. When the working distance deviates back and forth, each of the two bright spots moves 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 intraocular pressure measuring unit 1 moves in the vertical and horizontal directions with respect to the eye E, both the two bright spots move in the vertical and horizontal directions without changing the relative positions of the two bright spots.

  The projection optical system of the corneal deformation detection system is shared with the alignment projection optical system, is irradiated from the light source 21, passes through the projection lens 20, the dichroic mirror 19, the half mirror 18, and the lens 17, and is reflected by the dichroic mirror 13. 11 is irradiated to the eye E to be examined. In the corneal light receiving optical system, the corneal reflected light beam is partially reflected by the dichroic mirror 13 through the apertured window 10 and the lens 11, transmitted through the lens 17, and partially reflected by the half mirror 12. The light is guided to the photo sensor 23 through the aperture 22. The light receiving optical system is adjusted so that the amount of light received by the photosensor is maximized when the cornea of the eye E is applanated.

  In the fixation target projection optical system, the light beam emitted from the fixation LED 24 is reflected by the dichroic mirror 19, passes through the half mirror 18 and the lens 17, is reflected by the dichroic mirror 13, passes through the nozzle 4, and passes through the nozzle E. Led. 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 is connected to a cylinder 27 via a tube 28. A piston 26 is contained in the cylinder 27, and the piston 26 is connected to a solenoid 25.

  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 built-in rotary encoder on the roller 3, and a printer for printing measurement results 5 is connected to the port of the CPU 31.

  The 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. Based on the image data stored in the image memory 33, the CPU 31 performs image processing for extracting alignment bright spots and detects alignment. The video signal of the anterior ocular segment image captured by the CCD camera 16 is combined with the signal from the character generator 34, and the anterior ocular segment image, measurement value, and the like are displayed on the monitor 1.

  The left and right motors 35, the upper and lower motors 36, and the front and rear motors 37 are connected to a motor driver 38, and are driven by commands from the CPU 31 according to the input of the rotary encoders of the trackball 2 and the roller 3 and the misalignment during the auto alignment operation. The

  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 one selected from two inputs by the CPU. The 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 trackball 2 and the roller 3 are operated until two alignment bright spots can be confirmed on the monitor 1 to drive the left, right, up, down, and front and rear motors 35, 36, and 37, and the eye E and the optometry unit 6 of the apparatus. Perform rough alignment adjustment. Thereafter, the start switch on the switch panel 4 is pressed to start the auto alignment operation. In the auto alignment operation, 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 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 bright spots for alignment. In step 3, the left and right from the detected bright spot positions are detected. Calculate the amount of misalignment in the up / down and front / rear directions. In step 4, it is determined whether or not the alignment deviation is within a predetermined range. If it is out of the range, the process proceeds to step 5, and the left, right, up, down, and front and rear motors 35, 36, and 37 are driven according to the amount of alignment deviation. The auto-alignment operation from step 1 to step 5 for moving the eye 6 is repeated until it is determined in step 4 that the alignment deviation is within a predetermined range that can be measured.

  When auto-alignment is completed, the process proceeds to step 6 and the brightness of the bright spot for alignment detection is obtained from the image data of the anterior segment in the image memory 33 captured in step 1 when the alignment is completed. The threshold value of the output from the photosensor 23 for stopping the drive of the rotary solenoid 25 is calculated by the equation, and the process proceeds to step 7 where the drive of the rotary solenoid 25 is started via the driver 43 in response to a command from the CPU 31. As the drive starts, the piston 26 moves in the cylinder 27 and feeds air into the compression chamber 29 connected via the tube 28. The fed air is compressed and passes through the nozzle 12 and is blown to the eye E to be deformed. Is started.

  In the next step, the internal pressure signal in the compression chamber 29 and the corneal deformation signal are sampled. The internal pressure signal and the deformation signal are sampled a set number of times at a predetermined sampling period, and are stored in the memory 44 in chronological order. In step 8, the internal pressure signal is sampled. 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. In step 9, the cornea deformation signal is sampled. 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. . In step 10, the number of samplings is determined.

  In step 11, the digital data of the photosensor 23 is compared with the threshold value for stopping the driving of the rotary solenoid set in step 6. When the threshold value is exceeded, the driving of the rotary solenoid 25 is stopped in step 12. When it is determined in step 10 that 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 signal 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 from the data of.

  FIG. 7 shows the outputs of the pressure sensor 30 and the photosensor 23 when the rotary solenoid 25 is stopped at a certain threshold without considering the reflectance of the cornea. The horizontal axis represents the elapsed time t, and the vertical axis represents the outputs of the pressure sensor 30 and the photosensor 23. When the cornea reflectivity is high, the output of the photosensor 23 has a waveform of Ph (t), and when the output exceeds the threshold value ΔPh, the driving of the rotary solenoid 25 is stopped. At this time, the output of the pressure sensor 30 has a waveform of Prs (t). When the reflectivity of the cornea is low, the output of the photosensor 23 becomes low and becomes a waveform Ph ′ (t), and when the output exceeds the threshold ΔPh, the driving of the rotary solenoid 25 is stopped. At this time, the pressure sensor 30 has a waveform of Prs ′ (t) and is stronger than Prs (t). Thus, even when the intraocular pressure is low, the reflectivity of the cornea is low. The time to stop driving is delayed by ts′−ts, and the air pressure applied to the eye to be examined becomes high.

  FIG. 8 shows the pressure sensor 30 and the photosensor 23 when the threshold of the rotary solenoid 25 is changed by predicting the magnitude of the output of the photosensor 23 according to the brightness of the corneal bright spot at the completion of the alignment performed in step 6 described above. Is an output waveform. The cornea having a high reflectance has a threshold value ΔPh represented by a solid line, and if the reflectance is low, ΔPh ′ represented by a dotted line, the timing for stopping the driving of the rotary solenoid 25 is the same at time ts. By stopping the rotary solenoid 25 at the same timing, the output waveform of the pressure sensor 30 also becomes the same waveform Prs (t) regardless of the reflectivity of the cornea, and the air pressure stably given to the eye to be examined is stable regardless of the reflectivity. Can be reduced.

It is an external view of an Example. It is a block diagram of a measurement part. It is a figure of an alignment prism stop. It is an 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 a figure of the output of a pressure sensor and a photo sensor. It is a figure of the output 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 (1)

Alignment detection means for projecting alignment light beam onto the subject's eye cornea and detecting the reflected light, pressure means for deforming the cornea by spraying fluid onto the eye's cornea with a variable pressure in time, and measurement on the eye's cornea A projection optical system for projecting a luminous flux for light, a light receiving means for detecting the amount of light reflected from the eye cornea to be examined, and a deformation detecting means for detecting a predetermined deformation of the cornea by detecting a peak of output from the light receiving means, In a non-contact tonometer having a control means for stopping driving of the pressurizing means by detecting a predetermined output before the output of the light receiving means reaches a peak, the peak of the light receiving means for stopping the driving of the pressurizing means A non-contact tonometer characterized in that the predetermined output before reaching is changed according to the amount of light received by the alignment detection means.

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