JPH0556930A - Non-contact type ophthalmic pressure gage - Google Patents

Abstract

PURPOSE:To avoid unstability of a measurement caused by intrusion of the eyelashes, etc., by integrating a reflected light quantity level between reflected light quantity corresponding points which become the same reflected light quantity level in the increase side and the decrease side of the light quantity of a light quantity variation curve. CONSTITUTION:From a nozzle 9, an air current is emitted to the cornea C of an eye E to be examined. As a result, the cornea C is deformed. Subsequently, a reflected light quantity variation curve D which follows deformation of the cornea is obtained by an alignment projection optical system 2 and a photodetecting optical system 5. A pressure sensor 15a detects successively pressure in the nozzle 9. An arithmetic circuit 46 derives positions of reflected light quantity corresponding points X, Y which becomes the same reflected light quantity level in the increase side and the decrease side of the reflected light quantity variation curve D, respectively, calculates a reflected light quantity corresponding centroid point Z by calculating the reflected light quantity level of the light quantity variation curve D between each reflected light quantity corresponding point thereof X, Y, and calculates an ophthalmic pressure value, based on a pressure value of the pressure sensor 15a in the reflected light quantity corresponding centroid point Z. In such a way, unstability of a measurement caused by the eyelashes, etc., can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a non-contact tonometer for measuring intraocular pressure by blowing an air stream onto the cornea of an eye to be examined to deform the cornea.

[0002]

2. Description of the Related Art Conventionally, in a non-contact tonometer, an air flow blowing means for deforming the cornea of an eye to be inspected by blowing an air flow, and a light beam projected on the cornea to reflect the corneal deformation. A known one is provided with a corneal deformation detection optical system that detects the deformation of the cornea by detecting a change in the amount of light flux, and a pressure detection unit that is provided in the air flow blowing unit and that sequentially detects the pressure in the air flow blowing unit. Has been.

In this conventional non-contact tonometer, when a rotary solenoid which constitutes a part of the air flow blowing means is operated to drive a piston, the air flow is discharged from the nozzle of the air flow blowing means toward the cornea. ..

The cornea of the cornea is changed as shown in FIG.
It is transformed as shown in. In FIG. 8, symbol C indicates the cornea. The cornea C is hardly deformed immediately after the start of air flow emission (see the period t1). When a predetermined time elapses from the start of the discharge and the discharge pressure of the airflow increases, the cornea C is deformed as shown by the solid line (see period t2), and when the discharge pressure of the airflow further increases, the cornea C is flattened to a flat surface C '. It is leveled (see time t0). Further, when the discharge pressure of the airflow increases, the cornea C is depressed (see periods t3 and t4).

The amount of light reflected from the cornea C increases as the cornea C deforms from convex to flat, and theoretically reaches the maximum in the flat state, and changes from flat to concave. Decrease. Therefore, a light amount change curve as indicated by the symbol D is drawn.

On the other hand, the pressure detected by the pressure detecting means draws a pressure change curve P as shown in FIG. 9 over time. Since there is a correlation between the pressure value in the air flow blowing means and the intraocular pressure value of the eye to be inspected when the cornea C is in the flat state, the pressure change curve P when the light quantity change curve D shows the peak value D ′. The pressure value P0 is obtained, and the intraocular pressure value IOP is measured from this pressure value P0 using the arithmetic circuit.

[0007]

However, when the cornea C is in the flat state, the light amount change curve D does not always show the peak value. For example, when the eyelashes or the like of the eye to be inspected accidentally enter the projection reflection optical path of the corneal deformation detection optical system immediately before the cornea C reaches the flat state, the period t5 before and after the flat state of the cornea C is included. Thus, the light quantity of the reflected light flux decreases, and a light quantity change curve D as shown in FIG. 10 is obtained.

In this case, two peak values D1 ', D
2'is obtained before and after the flattened state of the cornea C, and the intraocular pressure value is obtained based on the peak values D1 'and D2', so that the measurement lacks stability (including reliability).

Further, a light amount change curve D as shown in FIGS. 11 and 12 may be obtained due to tears, elasticity of the cornea, non-uniformity of air flow, and the like. FIG. 11 shows a case where the light amount gradually increases and decreases, and in this case, it becomes difficult to specify the peak position. Further, FIG. 12 shows a case where a fine disturbance occurs in the peak, and in this case also, it is difficult to specify the peak position.

Therefore, the conventional non-contact tonometer, which measures the intraocular pressure based on the detection of the peak position of the cornea C, has a problem that the measurement is not stable.

Therefore, an object of the present invention is to provide a non-contact tonometer capable of avoiding instability of measurement due to nonuniformity of airflow blown to the cornea, tears, elasticity of the cornea, mixing of eyelashes and the like. To provide.

[0012]

In order to solve the above-mentioned problems, a non-contact tonometer according to the present invention includes an air flow blowing means for blowing an air flow on the cornea of an eye to be examined to deform the cornea.
A corneal deformation detecting optical system for projecting a light flux onto the cornea to detect a light amount change curve of a reflected light flux associated with corneal deformation to detect deformation of the cornea; and an air flow blowing means provided in the air flow blowing means. The pressure detecting means for sequentially detecting the pressure and the positions of the reflected light amount corresponding points having the same reflected light amount level on the light amount increasing side and the light amount changing side of the light amount change curve are obtained, and the light amount between the respective reflected light amount corresponding points is obtained. A barycentric point corresponding to the reflected light amount for measuring the intraocular pressure value is calculated by integrating the reflected light amount level of the change curve, and the intraocular pressure value is calculated based on the pressure value of the pressure detecting means at the barycentric point corresponding to the reflected light amount. And an arithmetic circuit for performing the operation.

[0013]

According to the non-contact tonometer according to the present invention, the air flow blowing means discharges the air flow toward the cornea of the eye to be examined.
This deforms the cornea. The corneal deformation detection optical system can obtain a reflected light amount change curve associated with the corneal deformation. The pressure detecting means sequentially detects the pressure in the air flow blowing means.

The arithmetic circuit obtains the positions of the corresponding points of the reflected light quantity having the same reflected light quantity level on the increasing side and the decreasing side of the reflected light quantity change curve, and the reflected light quantity level of the light quantity change curve between the respective reflected light quantity change points. Is calculated to calculate the barycentric point corresponding to the reflected light amount, and the intraocular pressure value is calculated based on the pressure value of the pressure detecting means at the barycentric point corresponding to the reflected light amount.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is an observation optical system for observing the anterior segment of an eye E, and reference numerals 2 and 3 are projection corpuscles of a cornea C of the eye E.
Alignment projection optical systems 4, 5 for projecting toward the optical axis are light receiving optical systems for receiving the light flux reflected by each film C of the projected light flux. The observation optical system 1 has an objective lens 6, a half mirror 7, and a CCD camera 8. The optical axis of the objective lens 6 is
It is coaxial with the axis M of the nozzle 9. The nozzle 9 constitutes a part of an air flow blowing unit that discharges an air flow toward the cornea C. The eye E to be examined is illuminated by the light emitting diode 10, and the anterior eye image is formed on the CCD camera 8 by the objective lens 6. The CCD camera 8 is connected to a television monitor (not shown), and an anterior segment image 12 is displayed on its screen 11 as shown in FIG.

The nozzle 9 has a holding glass 1 as shown in FIG.
3 and is communicated with the chamber 15 of the cylinder device 14. Reference numeral 16 is a chamber window glass. The chamber 15 is provided with a pressure sensor 15a as a pressure detecting means for sequentially detecting the pressure inside the chamber.

The chamber 15 communicates with the compression chamber 17, and a reciprocable piston 18 is connected to a rotary solenoid 21 via a piston rod 19 and an arm 20. The rotary solenoid 21 starts driving when the eye E to be examined is properly aligned and the distance from the tip 9a of the nozzle 9 to the apex 22 of the cornea C reaches the reference working distance W.

As shown in FIG. 1, the alignment projection optical system 2 includes an infrared light emitting diode 24, a diaphragm 25, a condenser lens 26, a half mirror 27, and an objective lens 28. The alignment projection optical system 3 includes an infrared light emitting diode. Two
9, diaphragm 30, condenser lens 31, half mirror 3
2, 33 and an objective lens 34 are provided.

The infrared light from the infrared light emitting diode 24 is
The light passes through the diaphragm 25, is condensed by the condenser lens 26, passes through the central portion of the half mirror 27, and passes through the objective lens 2
8 and is projected by the objective lens 28 onto the cornea C as a parallel light beam P1. Similarly, the infrared light from the infrared light emitting diode 29 is projected by the objective lens 34 toward the cornea C as a parallel light flux P2. A pair of virtual images i and i'is formed by corneal specular reflection of the parallel light beams P1 and P2.

The light receiving optical system 4 is roughly composed of an objective lens 28, a half mirror 27, an image forming lens 35, a reflecting mirror 36, etc., and the light receiving optical system 5 is an objective lens 34, half mirrors 33, 32, and an image forming lens 37. The reflection mirror 38 is generally configured. The half mirror 32 has a function of reflecting the specularly reflected light flux forming the virtual image i based on the infrared light of the infrared light emitting diode 24 at its peripheral portion, and the half mirror 27 based on the infrared light of the infrared light emitting diode 29. It has a function of reflecting the specularly reflected light flux forming the virtual image i ′ at its peripheral portion.

The mirror-reflected light flux forming the virtual image i is collimated by the objective lens 34, reflected by the half mirror 32, guided to the imaging lens 37, converged by the imaging lens 37, and passed through the reflection mirror 38. Is guided to the half mirror 7. Similarly, the specularly reflected light flux forming the virtual image i ′ is guided to the half mirror 7 via the objective lens 28, the half mirror 27, the imaging lens 35, and the reflection mirror 36. A part of the specularly reflected light flux forming the virtual images i and i'is reflected by the half mirror 7 and guided to the light receiver 39 shown in FIG.

On the screen 11, a pair of index images K and K'corresponding to a pair of virtual images i and i'is formed by the specularly reflected light flux which is transmitted through the half mirror 7 and is guided to the CCD camera 8. The index images K and K'of the target eye E are aligned normally (optical axes L1 and L2 of the light receiving optical systems 4 and 5).
When the intersection of the axis M of the nozzle 9 and the axis M of the nozzle 9 coincides with the apex 22 of the cornea), they coincide with each other as shown in FIG. 5, and when the eye E to be inspected is not properly aligned, they are separated as shown in FIG. The light receiver 39 outputs a detection signal to the detection circuit 40 when the pair of index images K and K'match. As a result, the detection circuit 40 outputs a drive signal to the solenoid drive means 41, and discharge of the air flow toward the cornea C is started.

Alignment projection optical system 2 and light receiving optical system 5
Is also used as a corneal deformation detection optical system for detecting the deformation of the cornea C by projecting the light beam toward the cornea C and detecting the change in the amount of the reflected light beam accompanying the deformation of the cornea C. The light flux reflected from the cornea C is reflected by the half mirror 33 and guided to the condenser lens 43, condensed by the condenser lens 43 and guided to the diaphragm 44, and the diaphragm 44.
To reach the light receiver 45.

The output of the pressure sensor 15a and the output of the light receiver 45 are input to the arithmetic circuit 46. Pressure sensor 1
The pressure in the chamber detected by 5a draws a pressure change curve P as shown in FIG.
The light quantity of the reflected light flux received by the light receiver 45 draws a light quantity change curve D along with the deformation of the cornea C accompanying the air flow blowing. Here, the arithmetic circuit 46 is provided with a light amount detection level L of the reflected light flux.
Are provided as shown in FIG.

This light amount detection level L is the light amount detection level L of the reflected light flux on the light amount increasing side of the light amount change curve D.
It is used to define a reflected light quantity corresponding point X that crosses the light quantity change curve D and a reflected light quantity corresponding point Y that the light quantity of the reflected light flux crosses the light quantity detection level L on the light quantity decrease side of the light quantity change curve D.

The arithmetic circuit 46 integrates the light amount detection level L of the light amount change curve D between the position of the reflected light amount corresponding point X and the reflected light amount corresponding point Y to calculate the position of the reflected light amount corresponding barycentric point Z. Then, the calculation circuit 46 calculates the intraocular pressure value IOP from the pressure value P0 of the pressure sensor 15a corresponding to the position of the center of gravity Z corresponding to the reflected light amount.

A plurality of light amount detection levels L are provided, a plurality of barycentric points corresponding to the reflected light amounts are obtained, and a pressure value P0 corresponding to an average value of the plurality of barycentric points corresponding to the reflected light amounts is calculated to an intraocular pressure value IOP. It is also possible to ask. Further, the pressure values P0 corresponding to the plurality of gravity points corresponding to the reflected light amounts are obtained,
The intraocular pressure value IOP may be obtained based on the average pressure value.

FIG. 7 shows an embodiment in which the light quantity detection level L of the reflected light flux is set to 0. In this case, the reflected light quantity corresponding point X means the light quantity change start point X ', and the reflected light quantity corresponding point X'. The point Y means the light amount change end point Y ′, and the reflected light amount corresponding centroid point Z is the position of the light amount change start point X ′ and the light amount change end point Y ′.
It is obtained by integrating the light amount detection level L of the light amount change curve D with respect to the position.

According to these embodiments, instead of detecting that the cornea C which theoretically has the peak value is flattened to the flattened C ', the same reflection occurs on the increasing side and the decreasing side of the light amount change curve D. Since the positions of the corresponding points of the reflected light amount that are the light amount levels are obtained respectively, and the barycentric points of the reflected light amount level of the light amount change curve between the respective reflected light amount corresponding points are obtained to measure the intraocular pressure value, the air flow is not measured. Measurement instability due to uniformity, corneal elasticity, tears, eyelashes, etc. can be avoided.

The light amount detection level L can be set by software or hardware. For example, the light receiver 45
A backward diode for setting the light amount detection level L is provided in the subsequent stage so that the detection signal of the light receiver 45 is not output to the arithmetic circuit 46 unless the light amount of the reflected light flux is equal to or more than a predetermined value. The light quantity level L can also be set.

Although the time corresponding to the reflected light amount corresponding point can be used, the coordinate position of the memory can also be used.

[0032]

Since the non-contact tonometer according to the present invention is constructed as described above, the measurement is caused by the nonuniformity of the air flow blown onto the cornea, tears, elasticity of the cornea, and mixing of eyelashes. The instability of can be avoided.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of an optical system of a non-contact tonometer according to the present invention.

FIG. 2 is an explanatory diagram of a non-alignment state of the non-contact tonometer shown in FIG.

FIG. 3 is a schematic configuration diagram of an air flow blowing unit of the non-contact tonometer shown in FIG.

FIG. 4 is a diagram for explaining a main part of the non-contact tonometer shown in FIG.

5 is an explanatory diagram of an alignment state of the non-contact tonometer shown in FIG.

FIG. 6 is a light amount / pressure change curve diagram for explaining an example of intraocular pressure value measurement of the non-contact tonometer according to the present invention.

FIG. 7 is a light amount / pressure change curve diagram for explaining another example of the intraocular pressure value measurement of the non-contact tonometer according to the present invention.

FIG. 8 is an explanatory diagram showing a relationship between corneal deformation and a light amount change curve.

FIG. 9 is an explanatory diagram showing a relationship between a light amount change curve and a pressure change curve.

FIG. 10 is an explanatory diagram showing a light amount change curve having two peaks.

FIG. 11 is an explanatory diagram showing a gradual light amount change curve.

FIG. 12 is a diagram showing a light amount change curve having a fine disturbance at the peak.

[Explanation of symbols]

 C ... Cornea D ... Light amount change curve E ... Eye to be examined X ... Reflected light amount corresponding point (increasing side) Y ... Reflected light amount corresponding point (decreasing side) Z ... Reflected light amount corresponding centroid point IOP ... Intraocular pressure value 2 ... Alignment projection optical system (Cornea Deformation Detection Optical System) 5 ... Receiving Optical System (Cornea Deformation Detection Optical System) 9 ... Nozzle (Air Flow Blowing Means) 15a ... Pressure Sensor (Pressure Detection Means) 46 ... Arithmetic Circuit

Claims (1)

[Claims] 1. An air flow blowing unit that blows an air flow to the cornea of an eye to be inspected to deform the cornea, and a light flux is projected onto the cornea to detect a light amount change curve of a reflected light flux associated with the corneal deformation, thereby deforming the cornea. A corneal deformation detection optical system for detecting, a pressure detecting means provided in the air flow blowing means for sequentially detecting the pressure in the air flow blowing means, and the same reflected light amount level on the light amount increasing side and the light amount changing side of the light amount change curve. And calculate the position of the reflected light amount corresponding point and calculate the reflected light amount corresponding barycentric point for measuring the intraocular pressure value by integrating the reflected light amount level of the light amount change curve between the respective reflected light amount corresponding points. And a calculation circuit for calculating the intraocular pressure value based on the pressure value of the pressure detection means at the center of gravity corresponding to the reflected light amount.