JPH0277231A - non-contact tonometer - 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 [Field of Industrial Application] The present invention relates to a non-contact tonometer that deforms the cornea of an eye to be examined by, for example, blowing air onto it and detects the deformation photoelectrically. It is something.

[Prior Art] A conventional tonometer of this type is known from Japanese Patent Publication No. 54-38431 and Japanese Patent Publication No. 58-6112, and as shown in FIG. Air is passed through the nozzle 2a of the objective lens 2 to the cornea Ec of the eye E to be examined.
sprayed as an air stream. It is common to detect applanation of the cornea by including a corneal deformation detection system that projects light obliquely onto the cornea Ec and receives the corneal reflected light obliquely. That is, light from a light source 3 such as a light emitting diode is projected onto the cornea Ec of the eye E from an oblique direction through a projection optical system 4, and the reflected light is received by a photoelectric light receiving element 6 from an oblique direction through a light receiving optical system 5. I have to. Note that 7 is a finder optical system.

Furthermore, in Japanese Patent Application Laid-open No. 49-130092, FIG.
), it is disclosed that a corneal deformation detection system is provided that projects light onto the cornea Ec from the optical axis direction and receives the corneal reflected light in the optical axis direction. That is, the light emitted from the light source 3a irradiates the cornea Ec through the lens 7a and the objective lens 2 so as to go to the focal point of the cornea Ec,
The light reflected by the cornea Ec is received by the photoelectric light receiving element 6a via the lens 7a and the objective lens 2.

However, in this Japanese Patent Application Laid-Open No. 49-130092, the light source 3a and the photoelectric light receiving element 6a have an angle fiEc before deformation.
Since there is a conjugate relationship with respect to the optical system having the reflecting surface, it is not possible to accurately recognize the deformation of the cornea Ec.

[Objective of the Invention] The object of the present invention is to solve the above-mentioned problems, to accurately detect corneal deformation to improve measurement accuracy, and to obtain the intraocular pressure at a time when the corneal deformation is small, thereby improving the measurement accuracy of the subject's eye. An object of the present invention is to provide a non-contact tonometer that uses compressed fluid to alleviate [1].

[Summary of the Invention] The gist of the present invention for achieving the above object is to provide a corneal deformation system that sprays compressed fluid at a temporally variable pressure onto the cornea of the eye to be examined from a nozzle facing the eye to be examined, and a light source to the eye to be examined. a deformation detection system that irradiates a light flux from the cornea and receives the corneal reflected light with a photoelectric light receiving element, and when the cornea is deformed to a certain curvature before applanation, the light source and the light receiving element communicate with each other through corneal reflection. A non-contact device characterized in that the light source and the light receiving element are arranged at positions that are optically substantially conjugate, and the intraocular pressure value is determined by detecting that the cornea has deformed to the certain curvature before applanation. It is a tonometer.

[Embodiments of the Invention] The present invention will be described in detail based on embodiments illustrated in FIGS. 1 to 8.

In the first embodiment shown in FIG. 1, the air in the air compression chamber 11 is pushed out by a piston 12 so that the pressure becomes variable over time, and a nozzle 13 attached to an objective lens 13 is used.
A is sprayed onto the cornea Ec of the eye E to be examined. The light beam from the light source 14 is condensed by the lens 15, further reflected in the direction of the eye E through the light splitting member 16, passes through the window 17 and the nozzle 13a of the objective lens 13, and is projected onto the cornea Ec. has been done. In addition, corneal E
The reflected light beam from C passes through the lens portion around the nozzle 13a of the objective lens 13 and is received by the photoelectric light receiving element 18, and this photoelectric light receiving element 18 has a cornea Ec with a constant curvature 1, for example, a radius of curvature r. It is arranged at a position where the reflected light from the corner 1liEc is focused when the angle becomes 15 mm.

In the configuration shown in FIG.
a, and is blown onto the cornea Ec as an air stream.

The air pressure increases with time, and when the air pressure in the cornea Ec exceeds the intraocular pressure, the cornea Ec begins to deform, and the cornea E
Deform so that the radius of curvature of c becomes larger. The light flux emitted from the light source 14 and reflected at the angle [Ec is condensed on the light receiving surface of the photoelectric receiving element 18 when the cornea Ec reaches a certain curvature. The time when the signal of the light receiving element 18 becomes maximum is the time when the air pressure and the intraocular pressure are in equilibrium, and it is possible to measure the intraocular pressure of the eye E based on the air pressure at this point.

Note that instead of measuring for one hour, a pressure sensor 19 is provided inside the air compression chamber 11 as shown in FIG.
It is also possible to measure the intraocular pressure value from the output of the pressure sensor 19 when the signal reaches the maximum.

As for the constant curvature mentioned above, the radius of curvature of the normal cornea Ec is 7 to 8 mm, so if the curvature is set to about 10 to 20 mm, the initial stage of deformation can be detected compared to conventional applanation. Therefore, it is difficult to be affected by the hardness of the eyeball due to the elasticity of the cornea itself.

FIG. 2 shows a second embodiment, in which the same reference numerals as in FIG. 1 represent the same members. In this example, objective lens 1
A flat glass 20 having a nozzle 20a is provided at position 3, and a lens 21 disposed between the air compression chamber 11 and the light splitting member 16 functions as an objective lens.

Next, FIG. 3 shows a third embodiment, in which the positions of the light [14] and the photoelectric light receiving element 18 in the embodiment shown in FIG. 1 are interchanged. Similarly, FIG. 4 shows a fourth embodiment, in which the positions of the light source 14 and the photoelectric light receiving element 18 in the embodiment shown in FIG. 2 are interchanged.

In each of the above embodiments, it has been shown that a divergent light flux or a convergent light flux is used as the light flux for irradiating the eye E to be examined, but in the fifth embodiment shown in FIG. Using a parallel light flux, this parallel light flux is transmitted to the nozzle 13.
In FIG. 5, the light source 14 is located at the focal point of the lens 15, and the collimated beam exiting the lens 15 passes through the aperture 22 and enters the hole of the objective lens 13. It passes through the nozzle 13a.

FIG. 6 shows a sixth embodiment, in which the light emitted from the light source 14 forms an image at the focal position of the lens 21 through a lens 15° and an aperture 22°, and exits the lens 21 as a parallel light beam, and is emitted from the flat glass 20. It passes through the nozzle 20a provided in the.

FIG. 7 shows a seventh embodiment, in which the positions of the light source 14 and the photoelectric light receiving element 18 in the embodiment shown in FIG. 5 are interchanged. Similarly, FIG. 8 shows an eighth embodiment, in which the light source 14 and photoelectric light receiving element 1 in the embodiment shown in FIG.
The positions of 8 have been swapped.

[Effects of the Invention] As explained above, according to the non-contact tonometer according to the present invention, it is possible to accurately detect corneal deformation and improve measurement accuracy, and moreover, by determining the intraocular pressure at a time when corneal deformation is small. , the impact of the compressed fluid on the subject's eye can be alleviated.

[Brief explanation of the drawing]

1 to 8 are block diagrams of each embodiment of a non-contact tonometer according to the present invention, and FIGS. 9(a) and 9(b) are block diagrams of a conventional example. 11 is an air compression chamber, 12 is a piston, 13 is an objective lens, 13a, 20a are nozzles, 14 is a light source, 15.2
1 is a lens, 16 is a light splitting member. 18 is a photoelectric light receiving element, 19 is a pressure sensor, 20 is a flat glass, and 22 is an aperture. Bad times Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 Figure 9 (Q) (b,)

Claims (1)

[Claims] 1. A corneal deformation system that sprays compressed fluid at a temporally variable pressure onto the cornea of the eye to be examined from a nozzle facing the eye to be examined, and a modification that irradiates the eye to be examined with a light beam from a light source and receives the reflected light from the cornea with a photoelectric light receiving element. and a detection system, the light source and the light receiving element are positioned at a position where the light source and the light receiving element become optically approximately conjugate through corneal reflection when the cornea is deformed to a certain curvature before applanation. A non-contact tonometer, characterized in that the intraocular pressure value is determined by detecting that the cornea has deformed to the predetermined curvature before applanation.