JPH0288036A - Non-contact tonometer - Google Patents

Abstract

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

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a non-contact type eye that deforms the cornea by spraying a compressed fluid onto the eye to be examined, and measures the intraocular pressure of the eye to be examined based on the deformed state. It is related to pressure gauges.

[Prior Art] Conventionally, this type of non-contact tonometer typically uses compressed air as the compressed fluid. For example,
As disclosed in Japanese Patent Publication No. 38437 and Japanese Patent Publication No. 61-321, air in a compression chamber is gradually compressed by a piston driven by a solenoid, and this compressed air is injected into the cornea of the eye to be examined through a nozzle. However, the pressure inside the compression chamber is measured when the cornea becomes applanated, and then the power to the solenoid is turned off.

In addition, this type of non-contact tonometer has a measurement range of up to 100 mm in order to be able to measure even severely elevated intraocular pressure.
It is set to about mmHg.

However, since most of the normal eyes to be examined have intraocular pressures of up to about 30 mmHg, by providing multiple measurement ranges, for example, two levels, compressed fluid with a pressure higher than necessary is injected onto the cornea. Devices that avoid causing excessive discomfort to the examiner have also been developed in recent years.

[Problems to be Solved by the Invention] However, in the conventional example, when measuring in a lower measurement range, if the eye to be examined has high intraocular pressure that exceeds the above range, a certain amount of corneal deformation naturally occurs. cannot be obtained and cannot be measured. Here, it is difficult to distinguish whether the cause of the inability to measure is due to overrange, or whether it is due to malalignment caused by the subject's eye moving or blinking during measurement. be.

[Object of the Invention] The object of the present invention is to solve the above-mentioned problems, and to make it possible to distinguish whether the cause of the same measurement error is an alignment error or an overrange error, so that the examiner can It is an object of the present invention to provide a non-contact tonometer that enables more accurate treatment.

[Summary of the invention] The gist of the present invention is to achieve the above objects.

a fluid ejecting means for spraying a fluid that is pressurized over time onto the cornea of the subject's eye; a deformation detecting means for detecting that the cornea is in a predetermined deformed state due to the fluid; and a display means for displaying the measurement results; an alignment detection means for determining the degree of coincidence between the fluid ejection direction and the corneal measurement site; and an alignment detection means for determining the degree of coincidence between the fluid ejection direction and the corneal measurement site; control means that determines that the eye to be examined is outside the measurement range if the alignment state detected by the eye remains at a predetermined level or higher, and determines that the alignment is poor if the alignment state is below the predetermined level. This is a non-contact tonometer characterized by:

[Embodiment 1 of the invention The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows a first embodiment, in which a piston 3 driven by a solenoid 1 via a crank 2 enters a compression chamber 4 to compress the air in the compression chamber 4, and the compressed air is sent to a nozzle 5. It is designed to spray onto the cornea Ec of the eye E to be examined. Also.

A pressure sensor 6 is provided within the compression chamber 4 .

A concave mirror 7 is provided in front of the nozzle 5.
is a concave dichroic mirror that reflects visible light and transmits near-infrared light, and is configured to form an image of the front end of the eye E on the bottom of the eye E. Further, in a portion corresponding to the optical path behind the nozzle 5, a transmission window 8 made of a transparent material is provided.
．． 9 is provided, and the nozzle 5 is attached to the center of the transmission window 8. On the optical path behind the transparent window 9,
Dichroic mirror 10 that transmits visible light and reflects near-infrared light
, lenses 11, 12, and optical sensors 13 are arranged in sequence. On the optical axis of the reflection side of the dichroic mirror 10, a lens 14 and an infrared light source 15 for alignment of an infrared light emitting diode or the like are arranged. Further, a light source 16 and a lens 17 are provided in an oblique direction of the eye E, and the light source 16
The reflected light from the anterior segment of the eye E can be detected by the lens 18 and the optical sensor 19. Furthermore, the output of the optical sensor 13 is transmitted through an amplifier 20 to A
The output of the A/D converter 21 is connected to the interface 22. Further, the output of the pressure sensor 6 is transmitted through an amplifier 23 and an A/D converter 24,
The output of the optical sensor 19 is connected to the interface 22 via an amplifier 25 and an A/D converter 26, respectively.

Further, the output of the interface 22 is connected to the solenoid 1 and the display 27, and the interface 22 is configured to exchange signals with an MPU (microprocessor unit) 28.

The light beam emitted from the infrared light source 15 passes through the lens 14, which transmits visible light.
The light is focused near the exit of the nozzle 5 via a dichroic mirror 10 that reflects near-infrared light.

Thereafter, the light beam diverges again, is reflected by the cornea Ec of the eye E, passes through the concave glaucroic mirror 17 that reflects visible light and transmits near-infrared light, and the transmission window 8°9, and passes through the lens 11.12. The light is focused on the optical sensor 13. The output of the optical sensor 13 is digitized by an A/D converter 21 via an amplifier 20.

That is, the amount of misalignment between the direction of the nozzle 5 and the optical axis L1 of the eye E to be examined is detected based on the light reception level of the corneal reflection image of the infrared light source 15.

In the intraocular pressure measurement means, a piston 3 is driven by a rotary solenoid 1 via a crank 2 to compress air in a compression chamber 4, and the internal pressure is detected by a pressure sensor 6. The compressed air that has passed through the nozzle 5 is applied to the cornea E of the eye E to be examined.
A predetermined deformation of the cornea Ec, such as applanation, is detected when the maximum amount of light is incident on the optical sensor 19 that receives the luminous flux from the light source 15. For example, the light source 15 and the optical sensor 19 each have a lens. The output of the optical sensor 19 is provided at the focal position of 14.15.
/b converter 26 digitizes the data. Further, the output value of the pressure sensor 6 when the output of the optical sensor 19 is the maximum is also the output value of the amplifier 23. The intraocular pressure value is digitized by the A/D converter 24 and calculated by the MPU 28 using a conversion formula determined in advance based on the value at that time.

The MPU 28 has a program timer and defines a time-up time. That is, if a corneal deformation signal is not obtained from a predetermined optical sensor 19 even after the time-up period has elapsed since the start of energization of the solenoid 1, it is determined that measurement is impossible, and an error message is displayed on the display device 27.

Here, as mentioned above, there are two reasons for the inability to measure.
Two cases are possible. The first is when a corneal deformation signal cannot be obtained from the optical sensor 19 due to misalignment or blinking, and in this case, there is a high possibility that the measurement will be possible if the measurement is performed again. This is a case where the compressed air itself could not fundamentally cause corneal deformation due to high intraocular pressure, and in this case, even if the measurement is repeated, the same result will not occur.
As long as it is an eye, it cannot be measured. In this case, from the next measurement onwards, it is necessary to increase the energy given to solenoid 1 to create air with higher pressure. In other words, it is essential to distinguish between the two since it greatly affects the probability of success in the next measurement.

FIG. 2 is a graph diagram of two cases where measurement errors were determined as described above and one example of normal measurement. Figure 2 (a
) is a graph of the output of the pressure sensor 6 and time t, (b) is a graph of the output of the optical sensor 13 for alignment and time t, and (c) is a graph of the output of the optical sensor 19 for detecting corneal deformation and time t. FIG.

In each of these graphs, ts is the measurement start point, t
u indicates the time-up point, and it is assumed here that the air in the compression chamber 4 is compressed as shown in (a). Oa is Ob if there is an error that caused a 7 alignment shift during measurement.
is the case of Oherenzi Erano, and OC is the case of normal measurement. At the measurement start time ts, the output of the alignment light and the output of the deformation detection light are Oa, Ob, and Oc, with no significant difference.

However, when an alignment shift occurs during measurement as in Oa and the output of the alignment light rapidly decreases, the deformed light output also remains small until the time-up point tu. If the measurement range is originally inappropriate for the eye E as in Ob, even if the air in the compression chamber 4 is gradually compressed as shown in (a), the corneal deformation detection light is not emitted from the optical sensor 19. No output is obtained; however, in this case, unlike Oa, the output of the alignment light remains at a constant level. In the case of normal measurement, when the pressure is gradually increased, the cornea Ec is applanated when it reaches the pressure equivalent to the intraocular pressure, and the output of the corneal deformation detection light is as shown in (c). It will have a peak.

Along with this, the output of the alignment light decreases rapidly, but when the cornea returns to its original convex state, it similarly returns to its original output level.

As mentioned above, it is determined by the MPU 28 whether or not the measurement was performed correctly.
This can be determined by detecting the output level of the corneal deformation detection light, and if the output level is at the time t
If the level of the alignment light is still small even after reaching u, detect the level of the alignment light at that point and
If the level is smaller than a predetermined level Th, it is determined that the measurement error is due to misalignment, and if it is larger than the level ↑h, it is determined that the measurement error is due to overrange.

FIG. 3 shows a second embodiment, and the difference from FIG. 1 is that an energy switching circuit 2 is connected between the interface 22 and the solenoid 1.
9 is interposed. A specific example of this energy switching circuit 29 is described in detail in Japanese Patent Publication No. 62-69191, but the reason for the inability to measure is that the eye E to be examined has too high intraocular pressure, resulting in overrange. Controlling the energy switching circuit 29 by the output of the interface 22 so as to apply larger energy to the solenoid 1 when corneal deformation has not been caused;
The structure is such that a higher mold pressure can be measured at the next measurement.

[Effects of the Invention] As explained above, the non-contact tonometer according to the present invention determines whether the cause of the inability to measure is due to a defective 7 alignment or due to measuring the subject's eye outside the measurement range. This distinction has the effect of making the first measurement more reliable.

[Brief explanation of the drawing]

The drawings show an embodiment of the non-contact tonometer according to the present invention, and FIG. 1 is a block diagram of the first embodiment, and FIG. 2 shows the relationship between time and compression chamber pressure, alignment light output, and corneal deformation detection light output. The graph diagram and FIG. 3 are partial configuration diagrams of the second embodiment. Symbol l, 5 is an infrared light source, 3 is a piston, 4 is a compression chamber, 6
is a pressure sensor, 7 is a concave gicchroic mirror, 10 is a gicchroic mirror, 13.19 is an optical sensor, 16 is a light source, 21.24.26 is an A/D converter, 22 is an interface, 27 is a display 28 is an MPU, and 29 is an energy switching circuit. Figure 2 Figure 1

Claims (1)

[Claims] 1. A fluid ejecting means for spraying a fluid that is pressurized over time onto the cornea of the eye to be examined; a deformation detecting means for detecting that the cornea is in a predetermined deformed state due to the fluid; and a display means for displaying the measurement results. an alignment detection means for determining the degree of coincidence between the fluid ejection direction and the corneal measurement site; control means for determining that the eye to be examined is outside the measurement range if the alignment state detected by the alignment means is maintained at a predetermined level or higher; and for determining that the alignment is poor if the alignment state is below the predetermined level; A non-contact tonometer characterized by having.