JPH01175831A - Non-contact ophthalmotonometer - Google Patents

Abstract

PURPOSE:To eliminate measuring errors based on the atmospheric variation and altitude difference by measuring the atmospheric pressure to correct an intraocular pressure value obtained from the measurement on the basis of measured atmospheric pressure. CONSTITUTION:An intraocular pressure value calculating circuit 40 has a barometer 41 as atmospheric pressure measuring means. The output of barometer 41 is amplified by an amplifying circuit 42 and converted to a digital signal by an A/D converter 43 to be input to ROMs 44, 45. The ROMs 44, 45 output factors ai and constants bi corresponding to the measured atmospheric pressure value AFi to determine a relation formula Pi=ai.t+bi on the basis of an actual flow pressure-time characteristic curve PRi in measuring the intraocular pressure. The output ai of ROM 44 is multiplied by a predetermined cornea deforming time t as the output of a clock 28 of a predetermined cornea deforming time measuring circuit 20 in a multiplication circuit 46 so that the multiplied output ai.t is input to an adding circuit 47. The adding circuit 47 adds the multiplied output ai.t to the constant bi output from ROM 45 to obtain the intraocular pressure Pi so that an indicator 50 indicates an intraocular pressure value P. Thus, the measuring errors of intraocular pressure value due to the variation of atmospheric pressure can be eliminated.

Description

[Detailed description of the invention] industrial benefits The present invention relates to improvements in non-contact tonometers.

[Theft] Q So 4 Traditionally, as a non-contact tonometer, for example, the
The one disclosed in Japanese Patent No. 4-38437 is known. The device disclosed in Japanese Patent Publication No. 54-38437 includes a fluid pulse generator as a fluid discharge means for generating fluid for deforming the cornea of the eye to be examined, and an injection device for emitting detection light toward the cornea of the eye to be examined. It includes an optical system and a detection optical system that detects detection light emitted from the emission optical system and reflected by the cornea of the eye to be examined. In this conventional device, when a fluid is released toward the cornea of the subject's eye, the cornea of the subject's eye deforms from a convex state to a flat state to a concave state as the flow pressure of the fluid increases; This method utilizes the phenomenon that when the fluid pressure is reduced, the cornea of the subject's eye returns from a concave state to a flat state to a convex state.

The ejection optical system and the detection optical system constitute a part of a corneal deformation detection means that detects a predetermined corneal deformation time from immediately after the fluid starts to be ejected until the cornea of the subject's eye undergoes a predetermined deformation by the fluid. The detection optical system is set so that the amount of light received by the detection optical system is maximum when the cornea of the eye to be examined is in a flat state. The fluid pulse generator is adapted to eject fluid according to a predetermined fluid pressure-time characteristic curve, the parameter of which is time T, as indicated by PR in FIG. The deformation and recovery time of the cornea of the subject's eye when receiving this fluid has a correlation with the intraocular pressure.
Intraocular pressure can be measured using the predetermined corneal deformation time t as a parameter. Therefore, in the method disclosed in Japanese Patent Publication No. 54-38437, the cornea of the eye to be examined, which is in a convex state, is deformed into a flat state immediately after the fluid starts flowing toward the cornea of the eye to be examined, following the flow pressure-time characteristic curve PR. The predetermined corneal deformation time t is measured as the time t until the light intensity of the light intensity-time characteristic curve R of the detection light reflected from the cornea of the eye to be examined reaches its maximum using the detection optical system, and the time t is It is converted into intraocular pressure.

That is, the predetermined fluid pressure-time characteristic curve P
Flow pressure p with time t of linear portion q0 of R0 as a parameter
o (in other words, intraocular pressure P) as P Hl = a o
-t + b o ...... It is calculated using the formula (1).

Here, a is the straight line portion q. is a coefficient representing the slope of
bo is a constant.

By the way, in the conventional non-contact tonometer described above, the flow pressure-time characteristic curve PR0 of the air fluid for applanating the cornea is unchanged, and therefore the coefficient of the above equation (1) is A constant.

It is assumed that is unchanged. However, the flow pressure-time characteristic curve of the air fluid changes depending on weather conditions and atmospheric pressure fluctuations based on the altitude of the location where the tonometer is installed. For example, under high pressure, the flow pressure-time characteristic curve of air fluid becomes a curve PR' as shown in FIG. 2, and therefore, the relationship between time t and intraocular pressure P1 in the straight line portion q' is p' = a' ・ten b' ・------・(
2), if the predetermined corneal deformation time as the corneal applanation time is t, the intraocular pressure is p
'(p'> p,) However, since the conventional non-contact tonometer calculates based on equation (1), it is measured as Po. In addition, under low pressure, the flow pressure-time characteristic curve of air fluid is curve PR as shown in Figure 2.
' Therefore, the relationship between time t and intraocular pressure P' in the straight line part q' is P/ == al・t+b' ・・・・・・
It is given by the formula (3), and if the predetermined corneal deformation time is t, the intraocular pressure is p'(p'< P,
) However, in the conventional non-contact tonometer, since the calculation is based on equation (1), it is measured as Po.

Light amount I and [true] The present invention has been made in consideration of the above circumstances.

The purpose is to provide a non-contact tonometer that can eliminate measurement errors due to atmospheric pressure fluctuations and elevation differences in the location where the non-contact tonometer is installed.

The non-contact tonometer according to the present invention is characterized by: an atmospheric pressure measuring means for measuring atmospheric pressure; and a correcting means for correcting the intraocular pressure value obtained by measurement based on the measured atmospheric pressure. It is equipped with the following.

The non-contact tonometer according to the present invention measures atmospheric pressure using an atmospheric pressure measuring means, and based on the measured atmospheric pressure,
Since the intraocular pressure value measured by the correction means is corrected, it is possible to eliminate measurement errors due to atmospheric pressure fluctuations and elevation differences in the location where the non-contact tonometer is installed.

Large" L Yu (First Embodiment) FIG. 1 shows a first embodiment of a non-contact tonometer according to the present invention. In FIG. 1, 1 indicates a fluid discharge means;
2 is the cornea of the eye to be examined, 3 is the exit optical system, 4 is the detection optical system, 0
1 is the visual axis of the cornea of the eye to be examined.

The fluid discharge means 1 is connected to the cornea of the eye to be examined (hereinafter referred to as cornea) 2
Fluid is ejected towards this cornea 2 in order to deform it. The fluid discharge means 1 is roughly composed of a mouth-to-tally solenoid 5, a cylinder 6, and a rotary solenoid drive circuit 7, and 8 is a drum of the rotary solenoid 5. The cylinder 6 has a cylinder tube section 9 and a nozzle tube section 10. A piston 12 is provided in the cylinder tube portion 9 so as to be able to reciprocate. The piston 12 is connected to the drum 8 of the rotary solenoid 5 via a piston rod 13. The nozzle cylinder part 10 extends straight toward the cornea 2, and has a diameter of 0. is the nozzle cylinder portion lO
is the axis of Fluid is discharged from this nozzle cylinder section 10 by the reciprocating movement of the piston 12.

The corner llI2 is deformed based on the fluid flow pressure, and deforms from a convex state to a planar state to a concave state as the fluid flow pressure increases. In FIG. 1, reference numeral C indicates a state in which the cornea 2 has undergone a predetermined deformation and has been applanated.

The exit optical system 3 and the detection optical system 4 constitute part of a corneal deformation detection means and have a function of photoelectrically detecting applanation of the cornea 2. The exit optical system 3 is roughly composed of a light source 14, a condenser lens 15, an aperture 16, and a projection lens 17, and Ol is an optical axis of the exit optical system 3. Aperture 16
is located at the focal point of the lens 17, and the light emitted from the light source 14 is directed to the condenser lens 15. It passes through the aperture 16 and the projection lens 17 and becomes a detection light consisting of a parallel light beam,
It is designed to be ejected onto the cornea 2.

The detection optical system 4 is composed of an imaging lens 18, an aperture 19, and a light receiving element 20, and 0□ is its front axis.

The detection light emitted from the exit optical system 3 and reflected by the cornea 2 passes through the imaging lens 18 and the aperture 19 to the light receiving element 20.
The light is received, photoelectrically converted, and input into an amplifier circuit 21 of a corneal predetermined deformation time measuring circuit, which will be described later. This amplifier circuit 21 outputs a corneal reflected light amount detection signal corresponding to a predetermined amount of deformation of the cornea 2. Here, the corneal reflected light amount changes according to the light amount-time curve R shown in FIG. 2 due to the deformation of the cornea.
It reaches its maximum at time Ta when the cornea 2 is applanated.

The corneal deformation detection means includes a corneal applanation time measuring circuit 22.

It has a measured intraocular pressure value calculation circuit 40. The configurations of both circuits will be explained below along with their functions.

Before starting the measurement, a measurement start signal is input to a measurement control circuit (not shown) to close the reset switch 26 for a certain period of time to discharge the charge in the capacitor 25, and then to open the reset switch 26. At the same time as this measurement starts, the rotary solenoid drive circuit 7 is turned on, the solenoid 8 is driven, and the piston 12 is activated.
Air as a fluid is discharged from the nozzle cylinder portion lσ. The output of the solenoid drive circuit 7 is input to a starter circuit 29. The starter circuit 29 immediately after receiving the output from the rotary solenoid drive circuit 7 (after a short period of time)
, outputs the start signal ST to the clock 28, and outputs the start signal ST to the clock 28.
starts timing. The start time of this timer 28 is time S shown in FIG. The corneal reflected light amount detection signal output from the amplifier circuit 21 is applied to the protective resistor 23 as an output voltage A.
, diode 24. The signal is input to a peak hold circuit PH consisting of a capacitor 25 and (-) input terminals of a comparator 27.

As shown in FIG. 3, the output voltage B of the diode 24 of the peak hold circuit PH is lower than the output voltage A of the amplifier circuit 21 by an amount that takes into account the voltage drop ΔV of the diode 24. Charge is accumulated in the capacitor 25 by this output voltage B, and the voltage of the capacitor 25 rises as shown by the broken line in FIG. 3, becomes constant after a certain period of time, and the peak hold circuit PH holds the peak. The output voltage B of the peak hold circuit PH is input as a comparison voltage to the (+) input terminals of the comparator 27, and the output voltage A
When the output voltage A becomes smaller than the output voltage B, the output of the comparator 27 becomes H (High) as shown in FIG.
) to L (Lo%I), this low level output is input to the timer 28 as a stop signal SP of the timer 28, and the timer 28 stops timing. As a result, the timer 28 measures the time T a (actually, the output voltage A This is the time when ΔV becomes smaller than the output voltage B of the peak bold circuit PH, but since ΔV is extremely small, it can be regarded as the time of the maximum output of the output A. In other words, it can be regarded as the corneal applanation time). Measure time t.

The intraocular pressure value calculation circuit 40 has a barometer 41 as an atmospheric pressure measuring means, and the barometer 41 is comprised of, for example, a semiconductor pressure sensor or a capacitive pressure sensor. After the output of the barometer 41 is amplified by the amplifier circuit 42,
It is converted into a digital signal by the A/D converter 43 and stored in the ROM 4.
4 is input to the ROM2S.

In order to calculate the intraocular pressure P based on the corneal predetermined deformation time t measured by the corneal applanation time measuring circuit 22, the ROM 44 calculates the linear part q of the fluid pressure-time characteristic curve PR shown in FIG.
This is to find the coefficient a of the relational expression % formula % (4) between L and applanation time t from the atmospheric pressure value AF measured by the barometer 41, and the atmospheric pressure value AF determined by experiment.
, and coefficient a are stored in the ROM 44 as a correlation table.

Similarly, the constants determined in advance by experiments,
The value of AFL and the atmospheric pressure value AFL are stored in the ROM 45 as a correlation table.

ROM44. The ROM 45 outputs a coefficient at and a constant s corresponding to the atmospheric pressure value AF on a one-to-one basis according to the atmospheric pressure value AF measured by the barometer 41, and calculates the actual flow pressure-time at the time of intraocular pressure measurement. The relational expression % is determined based on the characteristic curve PR.

The output a of the ROM 44 is multiplied by the corneal predetermined deformation time t as an output from the timer 28 of the corneal predetermined deformation time measuring circuit 20 in the multiplication circuit 46, and the multiplication output a,·t of the multiplication circuit 46 is multiplied by the corneal predetermined deformation time t as an output from the timer 28 of the corneal predetermined deformation time measuring circuit 20. is input. The adding circuit 47 adds the multiplication output a,·t and the output of the constant S output from the ROM 45, and calculates the intraocular pressure PL (PL=aL·
Find t+b,). The addition result is output to the display 50, and the display 50 displays the intraocular pressure value P.

Thus, in this embodiment, the barometer 4 is used for each intraocular pressure measurement.
Based on the atmospheric pressure value AF measured using 1, the actual intraocular pressure calculation formula % of the flow pressure-time characteristic curve of the air pulse emitted toward the cornea 2 is determined, and this determined calculation Since the intraocular pressure PL is determined based on the formula, it is possible to eliminate measurement errors in the intraocular pressure value due to fluctuations in atmospheric pressure.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention, in which the multiplier circuit 4
This configuration is such that the ROM 55 also serves as the function of 6. A/D converter 43 is installed at the upper digit address of ROM2S.
The atmospheric pressure measurement value AF is inputted, and the corneal predetermined deformation time t from the timer 28 is inputted into the lower digit address, and the atmospheric pressure value AFL, the corneal predetermined deformation time t, and the The product a of the coefficient a in equation (4) and the time t, ・
t is stored as a correlation table. The ROM 55 adds the product a,·t specified based on the atmospheric pressure value AFL inputted to the ROM 55 and the predetermined corneal deformation time t to the adder 4.
7. Note that the remaining configuration is the same as that of the first embodiment, so detailed explanation thereof will be omitted.

(Third Example) In this third example, the first example uses the atmospheric pressure value AF to determine the coefficient at and constant s of the intraocular pressure calculation formula pt = fi, j t + b. On the other hand, as shown by PR in Fig. 2, the intraocular pressure value P is determined using the calculation formula % formula % based on the predetermined reference flow pressure-time characteristic curve, and the obtained intraocular pressure value P .

is corrected by the atmospheric pressure AFL measured by the barometer 41,
The corrected intraocular pressure value PLj is determined, and the configuration of this embodiment will be explained based on the block diagram shown in FIG.

Note that the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Also, configurations that are completely the same as those of the first embodiment and are not directly related to this description are omitted from illustration. 61 is a ROM, and the ROM 61 contains an arithmetic expression p,=3. based on a reference fluid pressure-time characteristic curve PR.・t
+b, coefficient a. and the value of constant b0 are stored. The output of the ROM 61 is input to an arithmetic circuit 62.

This arithmetic circuit 62 uses the coefficient a, the constant b0, and the corneal predetermined deformation time t to form a reference fluid pressure-time characteristic curve PR.
The intraocular pressure value PL is calculated by calculating the calculation formula p, =H0・t+b, based on 0, and the obtained intraocular pressure value P is stored in the ROM.
Output to the lower digit address of 63.

In addition, the atmospheric pressure value AF is stored in the upper digit address of ROM63.
, is input. As shown in FIG.
are the intraocular pressure value P, the atmospheric pressure value AF, and the corrected intraocular pressure value Ps.
i(iej=LLL'''sn) is stored as a conversion matrix table. This conversion table is determined in advance through experiments or the like.

The ROM 63 outputs a corrected intraocular pressure value P L J from the intraocular pressure value P input into the lower digit address and the atmospheric pressure AFL input into the upper digit address, and displays it on the display 50. For example, when the measured intraocular pressure value is P and the atmospheric pressure value is AF, the corrected intraocular pressure value P, , is output from the ROM 63.

As described above, in this third embodiment, the intraocular pressure value calculated based on the reference fluid pressure-time characteristic curve PR is corrected using the measured atmospheric pressure value AF, and the correct intraocular pressure value (corrected intraocular pressure value AF) is corrected using the measured atmospheric pressure value AF. pressure value).

^ Bean summer shame As mentioned above, in the present invention, the atmospheric pressure can be measured and the intraocular pressure value under the measured atmospheric pressure can be determined, so the intraocular pressure value can be adjusted due to atmospheric fluctuations due to weather conditions or altitude differences. measurement errors can be removed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a first embodiment of a non-contact tonometer according to the present invention, and FIG. 2 is a diagram showing a corneal reflected light amount-time curve and a fluid flow pressure-time characteristic curve according to the present invention. A diagram showing the relationship,
FIG. 3 is a diagram showing the relationship between the output voltage A of the amplifier circuit 21, the output voltage B of the peak hold circuit PH, and the output of the comparator 27 according to the present invention. FIG. 4 is a block diagram of main parts showing a second embodiment of a non-contact tonometer according to the present invention, FIG. 5 is a block diagram of main parts showing a third embodiment of a non-contact tonometer according to the present invention, FIG. 6 is a matrix table showing the contents stored in the ROM 63 of the third embodiment. 1...Fluid discharge means 3...Ejection optical system (corneal deformation detection means) 4...Detection optical system (corneal deformation detection means) 22...Cornea predetermined deformation time measuring circuit (corneal deformation detection means) 40 ... Intraocular pressure value correction circuit (correction means) 41 ... Barometer 44.45 ... ROM 62 ... Arithmetic circuit Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 section

Claims (1)

[Scope of Claims] Fluid discharge means for discharging a fluid according to a predetermined fluid pressure-time characteristic curve toward the cornea of the subject's eye, and immediately after the fluid starts to be discharged, the cornea of the subject's eye is in a predetermined position due to the fluid. and a corneal deformation detection means for detecting a predetermined corneal deformation time until the cornea undergoes deformation, and a non-contact type that determines the intraocular pressure value of the eye to be examined from the correlation between the fluid-time characteristic curve and the corneal predetermined deformation time. A non-contact tonometer, characterized in that the tonometer is provided with an atmospheric pressure measuring means for measuring atmospheric pressure, and a correcting means for correcting an intraocular pressure value based on the measured atmospheric pressure.