JP4907320B2 - Non-contact tonometer - Google Patents

Description

  The present invention relates to a non-contact tonometer that measures the intraocular pressure of a subject's eye in a non-contact manner.

  Non-contact tonometers that measure intraocular pressure based on fluid pressure when a fluid is ejected toward the eye to be examined and the cornea is in a predetermined deformed state are known. The effect of thickness was not taken into account, and when the cornea was hard and thick, the intraocular pressure of the subject eye was measured to be high, and when the cornea was soft and thin, the intraocular pressure of the subject eye tended to be measured low .

Against this background, the pressure value at the first peak of the detection signal output from the corneal deformation detection optical system for detecting the applanation state of the eye cornea, and again to recover from the concave state of the cornea There is known a non-contact tonometer that corrects an intraocular pressure value from a difference (hysteresis) from a pressure value at a second peak that occurs during an applanation state and obtains an intraocular pressure value that eliminates the effect of the cornea. (See Patent Document 1).
JP-A-2005-53368

  However, when correcting the intraocular pressure value using an apparatus as disclosed in Patent Document 1, sufficient fluid pressure is sufficient for the eye cornea to detect the second peak signal with high accuracy. Necessitating proper injection, which is a heavy burden on the patient (eye to be examined).

  In view of the above problems, the present invention reduces the burden on the subject's eye due to the fluid ejected to the subject's eye, and obtains an accurate intraocular pressure value regardless of the hardness and thickness of the cornea of the subject's eye. It is an object of the present invention to provide a non-contact tonometer that can be used.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) fluid ejecting means for ejecting a compressed fluid toward the eye cornea to be examined, corneal deformation detecting means for optically detecting a deformation state of the cornea due to the compressed fluid from the fluid ejecting means,
A pressure detecting means for detecting the pressure of the compressed fluid injected into the cornea; and the cornea deformation detecting means detects that the cornea is in a predetermined deformed state, and a detection result of the pressure detecting means at the time of the detection A non-contact tonometer comprising: a calculating means for obtaining an intraocular pressure value based on the above-mentioned: addition of the cornea deformed by the additional pressure of the compressed fluid to be added after the eye cornea to be examined is deformed into the predetermined deformed state Correction means for obtaining an intraocular pressure value obtained from the corneal deformation detection means based on the pressure of the compressed fluid when deformed to a predetermined deformation state based on the additional deformation signal It is characterized by providing.
(2) The additional deformation signal of the compressed fluid in () is a light amount signal when the pressure of the compressed fluid is maximum or the compressed fluid is increased by a predetermined pressure .
(3) The correction means of (1) has a correction table in which the pre-correction intraocular pressure value is associated with the ratio of the deformation signal when it is deformed to a predetermined deformation state and the additional deformation signal. Features.

  ADVANTAGE OF THE INVENTION According to this invention, while reducing the burden of the test eye by the fluid injected with respect to a test eye, an exact intraocular pressure value can be calculated | required irrespective of the hardness and thickness of the cornea of a test eye.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a fluid ejection mechanism and its control mechanism of a non-contact tonometer according to this embodiment, and FIG. 2 is a diagram showing a schematic configuration of an optical system.

[Fluid injection mechanism]
The fluid pressure is generated by being compressed in the air compression chamber 11 by pressing the air in the cylinder 1 with the piston 2 driven by the solenoid 3. The compressed air passes through the nozzle 6 and is ejected toward the cornea of the eye E to be examined.

  A transparent glass plate 7 holds the nozzle 6 and transmits observation light and alignment light. 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 a rear wall of the air compression chamber 11 and transmits observation light and alignment light. Behind the glass plate 9, an optical system for observation and alignment described later is arranged. A pressure sensor 12 detects the pressure in the air compression chamber 11.

[Optical system]
In FIG. 2, 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, and the filter 34. The filter 34 transmits light from the light source 30 and the alignment light source 40, and has an opaque characteristic to light from an LED 50 for detecting corneal deformation described later. The image formed on the CCD camera 35 is displayed on the television monitor 36. O _L represents the optical axis of the observation optical system is coincident with the axis of the nozzle 6.

  Reference numeral 40 denotes an alignment infrared LED. The infrared light projected through the projection lens 41 is reflected by the beam splitter 31 and projected onto the eye E from the front. The corneal bright spot formed on the eye cornea by the LED 40 is imaged on the CCD camera 35 via the beam splitter 31 to the filter 34 and used for alignment.

  Reference numeral 50 denotes an LED for detecting corneal deformation. Light emitted from the LED 50 is made into a substantially parallel light beam by the collimator lens 51 and projected onto the eye cornea to be examined. The light reflected by the cornea passes through a filter 53 having characteristics that are opaque to the light from 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 to detect light. The light is received by the device 56. Thereby, the deformation state of the eye cornea to be examined is optically detected. The corneal deformation detection optical system is configured so that the detection signal from the light detector 56 becomes a maximum value (peak) when the eye cornea to be examined is in a predetermined deformation state (for example, an applanation state or a flat state). Is arranged. And in this embodiment, when the eye cornea to be examined is applanated, it arrange | positions so that the light-receiving amount of the photodetector 56 may become the maximum, and the eye cornea to be examined became the applanation state by injection of the compressed fluid. Can be detected.

  The optical system for detecting corneal deformation also serves as a part of the working distance detecting optical system. The light passing through the beam splitter 54 enters the one-dimensional detecting element 57, and the working distance is detected from the output signal. Is done.

[Control system]
In FIG. 1, reference numeral 20 denotes a control circuit that controls the entire apparatus. An output signal from the pressure sensor 12 and an output signal from the photodetector 56 are transmitted via an applanation detection signal processing circuit 21 and a signal detection processing circuit 22. Input to the control circuit 20. The control circuit 20 performs predetermined calculation processing based on each input output signal to obtain intraocular pressure. The measurement result is displayed and output on the television monitor 36. Reference numeral 23 denotes a drive circuit for driving the solenoid 3. Reference numeral 24 denotes a memory that stores data on the pressure change with time detected by the pressure sensor 12 and output signal data with time from the photodetector 56. The memory 24 stores intraocular pressure correction data for converting and correcting the output signal from the pressure sensor 12 into intraocular pressure data.

  In the apparatus having the above configuration, the operation for calculating intraocular pressure will be mainly described. The examiner observes the anterior segment image and the alignment bright spot displayed on the television monitor 36, and performs alignment adjustment in the vertical and horizontal directions. Moreover, since the guidance index is displayed on the television monitor 36 based on the position information sent from the one-dimensional detection element 57, the alignment adjustment is performed according to this.

  After the alignment is completed, when the examiner presses the measurement start switch (or the control circuit 20 automatically issues a measurement start signal based on the detection signal from the alignment optical system), the control circuit 20 passes the drive circuit 23 through the solenoid 3. Drive. The piston 2 compresses the air in the cylinder 1 and blows the compressed air from the nozzle 6 onto the eye cornea. When the compressed air is blown, the cornea is gradually deformed, and when the cornea reaches the applanation state, the maximum amount of light enters the photodetector 56. Output signals from the pressure sensor 12 and the light detector 56 are sequentially processed and stored in the memory 24 with time.

  FIG. 3 is a diagram showing temporal changes in the pressure signal Ps from the pressure sensor 12 and the corneal reflection light quantity signal Qs from the photodetector 56. The light amount signal Qs increases as the pressure signal Ps increases when the corneal surface deformation starts, and exhibits a peak (first peak) when the cornea is in an applanation state. The control circuit 20 stores the pressure signal Ps and the light amount signal Qs in the memory 24 over time from the start to the end of the compressed air blowing.

  In this embodiment, the control circuit 20 outputs a detection signal from the photodetector 56 that detects the deformation state of the eye cornea in order to measure the intraocular pressure without applying more fluid pressure than necessary to the eye. Based on this, the fluid pressure of the compressed fluid ejected to the eye to be examined is controlled. In this case, for example, the charge supply to the rotary solenoid 3 may be stopped after it is detected that the eye cornea is in an applanation state (the light amount signal is maximum), or the eye cornea is deformed. The pressurization operation may be stopped at a timing when the fluid pressure is increased by a predetermined pressure from the fluid pressure at the start (see Japanese Patent Application Laid-Open No. 11-192209 by the present applicant). In addition, the pressurizing operation may be reduced when the deformation of the eye cornea to be examined is started.

First, the control circuit 20 calculates the intraocular pressure PE1 before correction by computing a predetermined eye圧演formula from the pressure values Ps ₁ when the peak Qmax of the light quantity signal Qs is obtained. In addition, since the intraocular pressure value PE1 obtained here is a value that does not consider the influence of the thickness and hardness of the cornea, the calculated intraocular pressure value PE1 differs depending on the hardness and thickness of the cornea. Become. That is, the control circuit 20 obtains the detection result detected by the above-described corneal deformation detection optical system when the cornea is in an applanation state as the first detection result, and calculates the intraocular pressure value PE1 based on the detection result. To do.

  Next, the control circuit 20 performs the second deformation state of the eye cornea with respect to the pressure value of the compressed fluid set in advance while the eye cornea is further deformed in the intraocular direction after the eye cornea is in a predetermined deformation state. Is detected by the aforementioned corneal deformation detection optical system to obtain a second detection result, and the intraocular pressure value before correction is corrected based on the relationship between the first detection result and the second detection result. More specifically, as described above, the photodetector is calculated when the pre-correction intraocular pressure value calculated using the first detection result and a predetermined fluid pressure is injected to the eye cornea after the applanation. The intraocular pressure value is corrected based on the detected amount of light detected by 56.

  In FIG. 3, the light amount signal Qs (solid line or dotted line) after reaching the first peak decreases toward the indentation state of the eye cornea when the eye cornea is most deformed in the intraocular direction ( It increases as the cornea returns to the applanation state. Then, when the cornea is again in the applanation state, it reaches a peak (second peak), and finally returns to the detected light amount before the start of applanation.

  Here, both of the light amount signals Qs drawn by the solid line or the dotted line are those having the pressure value Ps1 when the first peak Qmax is reached. The light amount signal Qs drawn with a dotted line has a large amount of detected light during the time when the eye cornea is in an applanation state and then is depressed, and the light amount signal Qs drawn with a solid line is that the eye cornea is in an applanation state. This indicates that the detected light amount is small during the collapsed state. Conversely, the light amount signal Qs drawn by the dotted line has a small decrease in the detected light amount from the first peak Qmax, and the light amount signal Qs drawn by the solid line has a decrease in the detected light amount from the first peak Qmax. It is big. The amount of light detected varies depending on the amount of deformation of the cornea of the eye to be examined while the eye cornea is in an applanation state and then in a depressed state. The deformation amount of the cornea based on the injection pressure with fluid is considered to be influenced not only by the intraocular pressure of the eye to be examined but also by the hardness and thickness of the cornea. Therefore, the degree of influence of the hardness and thickness of the cornea of the eye to be examined can be obtained by obtaining the deformation amount of the cornea after corneal applanation based on the detection signal of the light quantity signal Qs after corneal applanation.

Next, the control circuit 20 corrects the shift of the intraocular pressure value due to the influence of the thickness and hardness of the cornea using the change in the detected light amount after the corneal applanation as described above. Here, the control circuit 20 calculates the detected light quantity Qm (second detection result) when the eye cornea to be examined is most deformed in the intraocular direction based on the light quantity signal Qs after cornea applanation stored in the memory 24. obtain. In this case, the light amount signal Qs when the fluid pressure ejected to the eye to be examined is maximum (when the pressure signal Ps is Pmax) may be acquired from the memory 24. At this time, the detected light quantity Qm obtained is higher as the cornea of the subject's eye is thicker and harder (for example, Qm ₁ ), and the lower value (eg, Qm ₂ ) is obtained as the cornea of the subject's eye is thinner and softer. It is done. Further, the control circuit 20 obtains a detected light amount Qmax during corneal applanation based on the light amount signal Qs stored in the memory 24.

Next, the control circuit 20 calculates a ratio Qm / Qmax between the detected light quantity Qm obtained as described above and the detected light quantity Qmax at the time of corneal applanation. The ratio Qm / Qmax obtained here can be converted into an amount of deformation from the cornea applanation of the subject's eye cornea to the intraocular direction, and the ratio Qm (for example, Qm ₁ ) / Qmax is increased as the cornea of the subject's eye becomes thicker and harder. The ratio Qm (for example, Qm ₂ ) / Qmax decreases as the cornea of the eye to be examined becomes thinner and softer. Therefore, the control circuit 20 corrects the shift of the intraocular pressure value due to the influence of the hardness and thickness of the eye cornea using the ratio Qm / Qmax calculated as described above.

  In the memory 24, a table of correction values Ph (PE1, Qm / Qmax) corresponding to combinations of the measured intraocular pressure value PE1 and the ratio Qm / Qmax as shown in FIG. 4 is stored in advance, and correction is necessary. The correction value is obtained from this table. Note that, when the fluid pressure of the compressed fluid is controlled to reduce the fluid pressure on the eye to be examined as in the present embodiment, the maximum fluid pressure Pmax may change for each measured value of the intraocular pressure value PE1. Therefore, the maximum air pressure Pmax is stored for each measured value of PE1. In addition, depending on the fluid pressure control method, there is a possibility that the maximum fluid pressure Pmax may change even if the measured values of PE1 are the same. In this case, the intraocular pressure value PE1, the ratio Qm / Qmax, and the maximum fluid pressure Pmax. A three-dimensional table consisting of these three parameters is stored in the memory 24. Further, a table composed of the intraocular pressure value PE1 and the ratio Qm / Qmax at a predetermined pressure value may be used. In addition to storing the table in the memory 24, a predetermined arithmetic expression may be constructed from the above combination, and a correction value may be obtained based on this.

Here, the corrected intraocular pressure value PE _TH of the eye to be examined is
PE _TH = PE1 + Ph (PE1, Qm / Qmax)
And is displayed on the monitor 36.

  The correction value Ph table includes, for example, a manometry measurement result in which the intraocular pressure is measured by inserting a needle directly into the eye, and the intraocular pressure value PE1 and the ratio Qm / Qmax obtained by the above measurement with the same eye to be examined. It can be created by determining the relationship through clinical experiments and doing this for a number of eyes.

  According to the configuration as described above, when correcting the intraocular pressure value due to the influence of the hardness and thickness of the cornea of the eye to be examined, it is not necessary to detect the second peak position with high accuracy. Therefore, since it is not necessary to increase the fluid pressure of the compressed fluid with respect to the eye to be examined, unnecessary fluid pressure is not applied to the eye to be examined, and measurement with a weaker fluid ejection becomes possible. In addition, by calculating the degree of influence of the hardness and thickness of the cornea from the change in the amount of light detected after applanation of the cornea, compared to when correcting intraocular pressure using the time to cornea applanation, etc. The detection error due to is small, and the stability of the required influence level is high.

Further, in the present embodiment, since the detected light amount when the fluid pressure ejected to the eye to be examined is maximum, the amount of change in the detected light amount due to the influence of the hardness and thickness of the cornea is large, and the correction value (or The degree of influence of the hardness and thickness of the cornea). However, the present invention is not limited to this, and as shown in FIG. 5, when the fluid pressure injected to the eye to be examined is a predetermined pressure value P _PR (for example, when the predetermined pressure ΔP has increased from the time of corneal applanation). The correction value may be obtained using the detected light quantity Q _PR (eg, Q _PR1 , Q _PR2 ). In this case, the larger the amount of change in the detected light quantity due to the influence of the hardness and thickness of the cornea, the more the measurement error is reduced.Therefore, if an appropriate detection position is obtained in consideration of the relationship between the change in the detected light quantity and the measurement error. Good.

  In the present embodiment, the correction value is obtained using the ratio Qm / Qmax. However, the present invention is not limited to this as long as the correction value is obtained using the detected light quantity Qm obtained from the memory 24. is not. For example, the correction value may be obtained based on Qmax−Qm obtained by dividing the detected light quantity Qm from the detected light quantity Qmax at the maximum fluid pressure.

It is a figure which shows the fluid ejection mechanism of the non-contact-type tonometer which concerns on this embodiment, and its control mechanism. It is a figure which shows schematic structure of the optical system of the non-contact type tonometer which concerns on this embodiment. It is the figure which showed the time-dependent change of the pressure signal by a pressure sensor, and the corneal reflection light quantity signal by a photodetector. It is an example of the table of correction value Ph (PE1, Qm / Qmax) corresponding to the combination of measured intraocular pressure value PE1 and ratio Qm / Qmax. Predetermined pressure value P _PR (e.g., when the increased predetermined pressure ΔP from the time of corneal applanation) is a diagram illustrating a case of obtaining the correction values by using the detected light quantity Q _PR when a.

Explanation of symbols

1 Cylinder 2 Piston 3 Solenoid 12 Pressure Sensor 20 Control Circuit 22 Signal Detection Processing Circuit 23 Drive Circuit 24 Memory 50 LED
56 photodetectors

Claims (3)

Fluid ejecting means for ejecting a compressed fluid toward the eye cornea to be examined; corneal deformation detecting means for optically detecting a deformation state of the cornea due to the compressed fluid from the fluid ejecting means;
A pressure detecting means for detecting the pressure of the compressed fluid injected into the cornea; and the cornea deformation detecting means detects that the cornea is in a predetermined deformed state, and a detection result of the pressure detecting means at the time of the detection A non-contact tonometer comprising an arithmetic means for obtaining an intraocular pressure value based on
After the subject eye cornea is deformed into the predetermined deformation state, an additional deformation signal of the cornea deformed by the additional pressure of the additional compressed fluid is obtained from the cornea deformation detecting means, and based on the additional deformation signal A non-contact tonometer comprising correction means for correcting an intraocular pressure value obtained based on the pressure of the compressed fluid when deformed into a predetermined deformation state . The non-contact type tonometer according to claim 1, wherein the additional deformation signal of the compressed fluid is a light amount signal when the pressure of the compressed fluid is maximum or the compressed fluid is increased by a predetermined pressure. The correction means according to claim 1 has a correction table in which the ratio between the deformation signal when the eye pressure value before correction is deformed to a predetermined deformation state and the additional deformation signal are associated with each other. Non-contact tonometer.