JPS59125542A - Eye pressure meter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Technical field The present invention relates to a tonometer for measuring intraocular pressure of an eye to be examined.

Conventional technology Intraocular pressure testing is performed for the prevention, early detection, diagnosis, and post-treatment or follow-up monitoring of glaucoma, which is associated with diabetic omentum 1 negative disease and has a high rate of blindness. IIJ pre-bottom inspection is being carried out. The history of intraocular pressure testing goes back to palpation.In recent years, the Goldmann tonometer, as described in Unpublished Patent No. 3,070,4197, has solved the problem of ocular wall stiffness and is extremely reliable. Widely used by ophthalmologists as a tonometer.

As shown in Figure 1, the Goldmann tonometer consists of a light source (2) from a tungsten lamp, a condensing lens (4), an infrared and near-infrared light cut filter (6), and an anno-char (8).
), an illumination optical system consisting of a blue filter (9), a projection lens (10) and a mirror (12) for projecting blue light onto the applanation plane, and an illumination optical system for applanating the anterior surface of the ocular surface of the eye to be examined Applanation pickup (PU) and applanation pickup (PU)
Manual dial (1,
4) It has an applanation drum (PD) (r) and a finder F for the examiner to view the applanation plane. The front surface of the pickup (PU) (the surface that contacts the eyeball) is a transparent flat surface, and two micro prisms (1
6a) (lfib) is provided. Then, when measuring intraocular pressure, fluorescein (a fluorescent substance) is applied to the eye to be examined.
After instilling into the eye, turn the manual dial (1) on the applanation drum (PD).
4)? Operate and gradually press the eyeball (D) with the pickup (pTJ).The illumination optical system illuminates the front of the pickup (PU) with only blue light,
- Form and form the char (8) on the second surface. As the eyeball (F2) is pressed by the applanation pick-up (PU'l), the front surface of the eyeball (F2) is gradually applanated and becomes flat, and the area between the eyeball ■ and the applanation pick-up (PU), i.e. Fluorescein (FL) remains around the pressure plane.

The peak of the absorption spectrum of fluorescene (FL) is around the wavelength 490 mm, and the peak of the excitation spectrum is around the wavelength 5.
Since it is around 20 mrn, the blue light is fluorescein (
When FL) is excited, a green fluorescent ring is formed surrounding the pressure plane. Therefore, the section surrounded by this fluorescent ring is the applanation plane.

In the Goldman pressure gauge, when this fluorescent ring kfl is observed through the finder (FIR), the prism (1,6a
) (16b), the second h (a) (
b) (Looks like ci.

Then, in advance, the diameter of the fluorescent ring was set to 3. When it becomes nfirrrn, it becomes exactly amphibious circular image (as shown in Figure 2) (at
18a) (18b) It becomes a sea urchin. This diameter 3. (16mm
This value was set because the wall stiffness of intraocular pressure can be ignored.

Therefore, the examiner can see the fluorescent ring image (1, 8a) fl with the naked eye.
, 8b)? Manual dials (x4) of applanation drum (PD) while observing? When the operation reaches the state shown in Fig. 2 (a) where the amphibious circular images are just touching, the applanation stops, and the applied pressure value W (
Find gl. Alternatively, the suppressed pressure value P (mmHg) can be obtained by multiplying this pressurization value W(g) by F2O.

This principle assumes that the shape of the applanation plane is a circle, and its diameter? e
(mm), area k S (cm2), the intraocular pressure value P is 12, which is 5-(2I!×10)×π, so when l = 3.06 mm, exactly PζIOW
...(3) This is because.

However, this Goldmann tonometer has the following drawbacks. Since it is assumed that the applanation plane is circular and has a circular shape, measurement accuracy will deteriorate if the applanation plane is not circular due to astigmatism or the like. As a way to completely improve this, in the case of severe astigmatism, a method is used in which the applanation pick-up (PU) is rotated by a predetermined angle and measured, but the direction of astigmatism differs from person to person!
! ! Therefore, even if this method is used, it is not possible to accurately measure intraocular pressure for all people, and the operation becomes complicated.

Furthermore, the position Wk of the pickup (PU) and the eyeball [F] must be precisely adjusted so that the boundary line of both prisms (1, 6a x 16b) passes through the center of the circular applanation plane. This adjustment is essential and the adjustment operation is troublesome, since the accuracy will be lowered. In addition, the amphibian image observed due to the smearing of the instilled fluorescein into the pressure plane appears quite blurry, and the diameter of the amphibian circle constantly changes due to heart beats. Fig. 2 (al) It takes skill to quickly detect with the naked eye when they are just in contact, and there are individual differences in detection, which affects accuracy.Furthermore, with the Goldmann tonometer, the fluorescent ring 9- The intraocular pressure when the diameter is 3.06 mm is only measured, and the 21st Zl (b
) Since the diameter of the applanation plane is unknown when it is deviated like cl, the intraocular pressure fluctuation due to the patient's 6-hour pulsation,
In other words, it is not possible to measure the maximum intraocular pressure and the average intraocular pressure.

Purpose The present invention was made in order to improve the drawbacks of the Goldmann tonometer described above.The purpose of the present invention is to easily and accurately measure the intraocular pressure even when the fluorescent rings are arranged in a circular manner, such as in astigmatic eyes. To provide a tonometer that can perform measurements with high precision, does not require skill, and does not cause individual differences among examiners.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a Goldmann tonometer prism (], fial (16b) and finder (3).
Instead, in order to measure the surface P surrounded by the fluorescent ring, an image sensor and an image forming means for forming an image of the fluorescent ring on the image sensor are used.

110-Example Hereinafter, a tonometer according to an embodiment of the present invention will be explained in detail with reference to the drawings.This example measures the intraocular pressure based on observation with the naked eye like the conventional Goldmann tonometer. It is an automatic tonometer that automatically measures the intraocular pressure value without using the naked eye and automatically displays the intraocular pressure value itself.

FIG. 3 is a diagram showing the arrangement of an optical system in a tonometer according to an embodiment of the present invention. In this figure, parts that operate in the same way as in FIG. 1 are designated by the same reference numerals, and explanations thereof will be omitted. In this embodiment, the illumination optical system σ,) is exactly the same as that in FIG. However, the pickup (P
U) has a prism (168) (16b) as shown in Figure 1, but instead is a flat glass (E) for applanating the eyeball (E).
20) and a big amplifier lens (22). The big amplifier lens (22) is arranged so that its focal plane exactly coincides with the applanation plane, that is, the eye contact surface of the flat glass (20). (24) is a file cut file I letter, (26
) beam lens, (28) is an image sensor.

The relay lens (26) and the pickup lens (22) constitute image forming means for forming a same-size image of the fluorescent ring on the image sensor (28).

The reason why the pressure plane is located on the focal plane of the pickup lens (22) is that even if the pickup (PU) is moved from side to side in the figure in order to change the pressure applied to the eyeball (2), the image sensor ( 28) This is to keep the image magnification of l unchanged. Furthermore, the blue cut filter (24) allows the illumination light from the illumination optical system (□□□) to be directly transmitted to the image sensor (28).
This is to remove noise that is incident on the

With this configuration, an image of a fluorescent ring formed to surround the applanation plane is formed on the image sensor (28) by the pickup lens (22) and the relay lens (26).

After that, the area s (i) of the range surrounded by the fluorescent ring image on the image sensor (28) and the applied pressure value W at that time are determined.
IIF), the intraocular pressure value P(-1k) may be calculated based on equation (1). In the case of this example, as is clear from equation (1), S = 0.07856A = 7. When It 5 becomes -l/-P#10W.

Next, with reference to FIG. 4, a configuration for applanating the eyeball stop using the pickup (PU) in this embodiment and for measuring the applied pressure value at that time will be described.

In FIG. 4, (PM) is a pulse motor that supports the pickup (PU) and moves a movable table (30) that is guided by a linear guide (not shown) and is movable in the left-right direction in the figure. (32) is a car electric converter fixed on the movable table (30), and has a strain gauge (SG) for axis conversion. The other end (36) of the lever (36)
b), the pickup (PU) is brought into contact with the other end (a 811 ) of a support lever (38) fixed to one end (38a), and the support lever (38) is attached to the moving table (
30) is rotatably supported by a shaft (40) fixed to the shaft (40).

With this configuration, a pulse motor (
PM) is driven, and the movable table (30) is moved to the left -/Z in the figure as shown by the arrow (A). Then, in the trench where the big slope up (PU) touches the eyeball (6), press the cicada lever (
36) (88) does not rotate, but after making contact, the pickup (PU) receives a reaction force from the eyeball (4) as shown by the dotted line, so the support lever (38) rotates clockwise, thereby causing the lever to rotate. (36) is rotated counterclockwise to change the way the strain gauge (SG) outputs electricity.

That is, the force applied to [lji[(g) is converted into an electrical quantity by the strain gauge (SG).

Here, in this embodiment, the length of the support lever (38) from the shaft (4o) to the pickup (PU) is
0) to the other end (88b), and therefore, the force applied to the eyeball (5) is 10 times the force measured on the strain gauge (SG). be done. An electric signal corresponding to the change in the electric resistance value of the strain gauge (SG) is processed as a signal corresponding to the pressurization value W to the eyeball (6).

Next, a method for determining the area of the applanation plane from the fluorescent link image on the image sensor (28) will be explained using FIG. To simplify the explanation, in Fig. 5, the image sensor is assumed to be a t, ox + o area image sensor, and each element is (
A, +, +)... (AIo, 10). (
I) shows a fluorescent ring image, which is blurred and has a colorful width due to bleeding of fluorescein onto the pressure plane. The image sensor first scans A(+,
A) Sequentially output an output according to the amount of light received by the element in row (""')21"' t I Q ), then shift in the vertical scanning line direction to row (2, n ), A (s, n ) line"'
-A The elements in the (10*”) row output in sequence. Here, the output of the element that does not receive the fluorescent ring image (I) is low, and the output of the element that receives the fluorescent ring image (T) is the amount of light received. The method of determining the area of the fluorescent ring image (I) from the output of the image sensor will be described later.

FIG. 6 shows changes in the video signal in the -horizontal scanning line of the image sensor (28). The signal will be as shown.

Then, as shown in the figure, if the output of the part corresponding to the inside of the applanation plane is set to dark level ■0, then in this embodiment, y o-
Two threshold levels are set, 1-V and Vo+2V, and the intersections of the signal output and the Vo+2V level are respectively (v+) (vs), and the signal output and Vo+2V level are set as (v+) (vs).
-1-V level and the intersection with (vl) (and
), then the intersection of the straight line ) is detected as the cross-sectional width of the fluorescent ring image on this horizontal scanning line, and by detecting this width for each horizontal scanning line and adding them all, the area of the fluorescent ring image is determined. be. Kokote, between 11 N ha, (t/,)
(v,)fN'l interval is Nt, ('t/,XI/
4) If the interval between them is N, then N-2N, -
N, is calculated from N, ,N,.

FIG. 7 is a schematic diagram of the automatic tonometer of this embodiment, including the optical system for measuring intraocular pressure shown in FIG. 3 and the pressurizing means shown in FIG. 4. below,
The configuration of the device of this embodiment will be explained along with its operation. First, it is assumed that the illumination optical system (g) illuminates the subject's eyeball (5) with blue light in advance. When the measurer closes the measurement start switch (SW), the microprocessor (MP) is activated and the image sensor 15- (28) is activated and the pulse motor (PM) is activated.
) to move the moving table (30) in FIG. 4 to the left. The subject's eyes are injected with a fluorescent substance and their faces are fixed with gold, thus preventing the eyeballs from moving. The pulse motor (PM) initially moves the moving stage (30) close to the eyeball (g) at high speed. Pressure value measurement circuit (42
) is a strain gauge (SG) before moving the moving table (30).
)'s electrical output EO is stored in memory.

When the pickup (PU) comes into contact with the cornea of the eyeball (5), the pulse motor (PM) is switched to move the movement 4th (80) at a slower speed, and the pickup (PU)
This causes the eyeball (5) to become applanated. Then, the electrical output of the strain gauge (SG) increases in accordance with the pressure applied to the eyeball. Since the periphery of the applanation plane is surrounded by fluorescein, the image of the fluorescent ring corresponding to the shape of the applanation plane is transmitted via a pickup (PU) to an image sensor (
28) Formed on. The video signal from the image sensor (28) is input to a transverse line calculation circuit (44), and the circuit (44) calculates the interval N according to the diameter of the fluorescent ring image as explained using FIG. Each.

16- Detect each horizontal scanning line, convert it to a digital signal, and output it. Pressure value measuring circuit (42) c. Electrical output E to E of the sequential strain gauge (SG) at that time
The value obtained by subtracting O is detected, and this is converted into a digital signal and output. The area calculation circuit (46) in the microprocessor (MP) sequentially receives digital signals according to the interval N regarding each scanning line from the transverse line image calculation circuit (44), and calculates the sum of these signals in all vertical scanning directions. The area surrounded by the fluorescent ring image is calculated from the predetermined light receiving area of each element of the image sensor (28), and a signal corresponding to the calculated area is output. This area corresponds to the area S of the ocular pressure plane, and when the area S of the pressure plane becomes 7.35-, the microprocessor (MP) outputs a stop signal and stops the pulse motor (PM). Stop applying pressure to the eyeball (□□□). This area of 7.85-' is a value determined within a range where the wall hardness of the eyeball can be ignored.

The pressurization value measurement circuit (42) measures the eyeball (6) in this state.
Measures the number of pressurization values and outputs a digital signal accordingly.

Intraocular pressure value calculation circuit (48
) calculates the intraocular pressure value P in this state based on equation (1) using the above s and lA/, and outputs a signal corresponding to the calculated value. However, in the case of this example, as mentioned above, the eyeball
) is 10 times the force applied to the strain gauge (S
G) and the eyeball [F]
) between the pressure value W ig) and the intraocular pressure value P (-l4g), P#10W holds when the area S (shoulder) of the pressure plane is 0.0735 (7A), so Since the IOW is 4111 constant result W of the pressurization value measuring circuit (42), it is
It is used as the intraocular pressure value P, and there is no need to perform complicated calculations. l1II! The output of the H binary arithmetic circuit (48) is displayed on the display.In addition, in the Goldmann tonometer, the diameter of the fluorescent ring is 3.0 mm.
Only the intraocular pressure at 6- is measured, and the diameter of the applanation plane deviates from the state shown in Figure 2 (a), where the amphipod images are just touching, as shown in (1) or (0). Since the intraocular pressure is not known, it is not possible to measure the intraocular pressure fluctuations due to the heartbeat of the subject, that is, the maximum intraocular pressure, the minimum intraocular pressure, and the average intraocular pressure. On the other hand, in the above example, if the area of the fluorescent ring image is continued to be measured with the pressure applied to the eyeball stopped, the area A pressure value P is obtained, and intraocular pressure fluctuations due to heart beats can be measured. More specifically, a microprocessor (MP) measures each area Si (i-1, 2,...K) at predetermined time intervals.
The intraocular pressure value when the maximum area Smax is measured is the minimum P sea bream, the intraocular pressure value when the minimum area S is measured is the maximum intraocular pressure pmax, and the average of the total intraocular pressure values is memorized. mean intraocular pressure p
It may be displayed as ave. Alternatively, the intraocular pressure t11) may be changed at predetermined time intervals so that the examiner obtains the various intraocular pressure values from a large number of displayed intraocular pressure values.

According to this embodiment, all intraocular pressure measurements are automated, and the examiner simply turns on the measurement start switch (SW) and displays the display (
It is only necessary to read the displayed value (50), and the examiner manually operates the dial (14) to apply pressure to the eyeball and performs observation using the knob and finder port, as in the Goldmann tonometer shown in Figure 1. This eliminates the need for complex operations and calculations such as determining the pressure value from the rotational position of the dial when the two semicircular images to be observed are just touching each other, and multiplying this value by 10 to obtain the intraocular pressure value. Pressure measurement becomes significantly easier. Fourth, the fluorescent ring formed around the compressed surface due to bleeding of the instilled fluorescein onto the compressed surface is quite blurred, and it is necessary to detect with the naked eye when the two semicircular images just touch. With the Goldmann tonometer, skill is required for this detection, and there are individual differences among the examiners, but in this example, blurring of the fluorescent ring image can be detected using two threshold levels, as explained using Fig. 6. It is well approximated by a straight line approximation with Can be measured. Furthermore, the Goldmann tonometer measures intraocular pressure using the diameter of the fluorescent ring based on the assumption that the intraocular pressure plane is circular, and if the pressure plane is not circular, measurement errors will occur. As mentioned above, when measuring the astigmatic eye, a special operation of rotating the applanation pickup is required, but in this example, the area within the fluorescent ring is measured with an image sensor and the measurement is performed based on this. Since intraocular pressure is measured, accurate measurements can be made regardless of the shape of the fluorescent ring, and no special operations are required when measuring astigmatic eyes.

Fourth, according to this embodiment, it is possible to measure the area under pressure and the eyeball pressurization value, and it is also possible to capture their fluctuations, which makes it possible to measure them using a Goldmann tonometer. It is possible to measure the maximum intraocular pressure, minimum intraocular pressure, average intraocular pressure, etc., which was previously impossible, and it is also possible to measure intraocular pressure fluctuations due to heart beats. Also, with the Goldmann tonometer, accurate measurements could not be made unless the relative position between the pickup and the eyeball was adjusted so that the boundary line of the 7" IJ rhythm (16a) (t6b) passed through the center of the fluorescent ring. In the embodiment, since it is sufficient to form an image of the fluorescent ring on the image sensor, the relative position adjustment between the pickup and the eyeball is simple.

Effects As described above, the present invention applanates the eyeball to be examined into which a fluorescent substance has been instilled using an applanation pickup, and determines the intraocular pressure of the eyeball from the size of the fluorescent ring formed around the applanation surface. A tonometer for measuring the value, which includes: a pressurizing means for pressing the applanation pickup against the eyeball; a pressurizing value I'1111 determining means for measuring the pressurization value of the eyeball by the applanation pickup; an image forming means for forming an image; an image sensor for receiving the fluorescent ring image formed by the image forming means; and an area measuring means for measuring the area surrounded by the fluorescent ring image from the output of the image sensor. - A display means for displaying an eye pressure value according to a test calculation result based on the recorded eyeball pressure value and the recorded value, and is configured in this way. With this, you can directly read the intraocular pressure value without having to press the eyeball while looking through the finder like with a Goldmann tonometer and calculate the intraocular pressure value from the pressure value when the two semicircular images just touch. Since the area of the light ring is measured, intraocular pressure can be measured without any problem even if the shape of the applanation plane surrounded by the fluorescent ring is not circular, and no special operation is required even in the case of astigmatic eyes. Furthermore,
According to the present invention, since judgment by the examiner's naked eye is not required, measurement does not require any skill.In addition, individual differences among examiners often affect the measurement results, making highly accurate measurements difficult. can.

Furthermore, according to the present invention, it is only necessary to form an image of the fluorescent ring around the rolled surface on the image sensor, and the position of the nuclear image on the image sensor is irrelevant to measurement accuracy, so the position adjustment of the optical system is not necessary. It is much easier than the Goldmann tonometer.

As in the embodiment, by providing the pink-up with a glass plate for eyeball applanation and a pickup lens whose base point is the contact surface of the eyeball, even when the pickup is moved for eyeball applanation, 73- The magnification of the fluorescent ring image on the image sensor remains unchanged;
The area of the applanation plane can be easily measured without considering changes in the image magnification of the image forming means.

Fourth, in order to measure the area surrounded by the fluorescent ring image on the image sensor as in the embodiment, the cross-sectional width of the fluorescent ring on each horizontal scanning line is detected and added in the vertical direction, and a single The area can be easily measured by calculating the area from the sum of the light-receiving area and the cross-sectional width of the image sensor element. By determining each cross-sectional width using the responses N:2N, -N, as described above, it is possible to measure the area with a good approximation that takes into account the blurring of the fluorescent ring.

(Fumata Ding Margin) 24-

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a conventional Goldmann tonometer, FIG. FIG. 4 is a diagram showing the optical system of the pressure gauge, FIG. 4 is a diagram showing the pressurizing means and pressurized value measuring means of this embodiment, FIG. 5 is a diagram showing the state of image formation on the image sensor, and FIG. 6 is a diagram showing the image sensor. FIG. 7 is a diagram showing the output of one horizontal scanning line, and FIG. 7 is a schematic diagram showing the overall configuration of this embodiment. (G) Soaked eyeball to be examined, (FL); Fluorescent substance, (PU)
; applanation pickup, (22) (26), image forming means, (28) i image sensor, (PM) (30) (
38); Pressurizing means, (SG) (36) (42)
i Pressure value measuring means, (I) ; Fluorescent ring image, (4
4) (46) i area measuring means, (48) i intraocular pressure value calculating means. (50) i display means. Applicant Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. The eyeball to be examined in which a fluorescent substance has been instilled is applanated with an applanation pickup, and the IIIN pressure value of the 119 balls is determined based on the size of the fluorescent ring formed around the applanation plane. - In the tonometer to be measured, there is a pressure means that presses the applanation pickup against the eyeball, and the 111 to 1 value of the bulb due to the applanation pickup? I
TIII A pressurization value measuring means for forming the above-mentioned fluorescent ring A, and an image for receiving a fluorescent ring image formed by the image shape t'+ and the means Fiv. a sensor; an area measuring means for determining the area surrounded by the fluorescent ring image from the output of the image sensor; and an intraocular pressure value of the eyeball to be examined based on the pressurization value of the eyeball and the area. 1. A tonometer characterized by having a lateral pressure value calculation means for calculating the lateral pressure value, and a display means for displaying the intraocular pressure value according to the calculation result. 2. The applanation pickup has a transparent glass plate for applanating the eyeball, and a pickup lens whose focal plane is the eyeball contact surface of the glass plate, and the image forming means includes the pip-up lens. The tonometer according to claim 1, wherein the area measuring means is configured to form the light ring on the image sensor at a constant magnification. It has an addition means that can add the total in the direction and request the total, and the total and the transport.
The tonometer according to claim 1 or claim 2, wherein the tonometer is configured to measure the area surrounded by the fluorescent ring image based on the area of the image sensor element. 4. The transverse width detecting means detects the output of the image sensor element that does not receive the fluorescent ring image (i' Vo as V. 10 V. Two threshold levels of Vo + 2 V are set in advance, and - on the horizontal scanning line, By vignetting different circumferential parts of the fluorescent image, the distance between the two image sensor elements that output V. is N2, then N
3. A return pressure gauge according to claim 3, characterized in that 4' and 6 are configured to detect the N'rlz transverse width determined by =2 NI N2. 5. The pressurizing means is directed toward the eyeball to be examined fixed in a predetermined position.8. The present invention is characterized by having a movable movable table, excitation θ1 means for moving one movable concavity toward the eyeball, and support means supported by one movable concavity and movably supporting an applanation pickup. The tonometer according to any one of claims 1m to 4. 6. The tonometer according to claim 5, characterized in that the support means is pivotally supported on a movable table, and the applanation pickup is fixed to one side of the support lever. 7. The pressure value measuring means is configured to measure the pressure value applied to the eyeball from the relative displacement of the support lever with respect to the transfer table at the other end to which the applanation pickup is not fixed. 4-1+-The tonometer according to claim 6. 8 The distance from the fulcrum of the support lever to the one end where the applanation pickup is fixed is 10 times the distance from the fulcrum to the other end, and the force applied to the eyeball is 10 times the pressure applied to the eyeball. 8. The tonometer according to claim 7, wherein the tonometer is configured to be measured by the pressurization value measuring means. 9. The tonometer according to claim 7 or 8, wherein the pressurization value measuring means comprises a strain gauge whose electrical output changes according to the amount of displacement of the other end of the support lever. 10 The control means further includes a control means, and the control means controls the pressure applied to the eyeball by the pressurizing means when the area of the pressure plane is approximately 7.35 cm2, based on the result measured by the area measuring means. A patent claim characterized in that the intraocular pressure value calculation means is configured to control the intraocular pressure value calculation means so that the intraocular pressure value cannot be obtained by stopping the pressurization and multiplying the pressurization value in this state [i- by 10] The tonometer according to any one of the ranges 1 to 1. 11 The pressurization value measuring means is configured to output a value corresponding to 10 times the pressurization value to the eyeball, and in the above state, the intraocular pressure value calculating means converts the output value of the pressurization value measuring means into that value. −
11. The tonometer according to claim 10, wherein the tonometer is configured to obtain a calculation result as a 1-1 intraocular pressure value.