JPS6230768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intraocular pressure measurement device, and more particularly to an improvement in a device for non-contact measurement of intraocular pressure by air blowing.

Conventionally, a non-contact tonometer described in Japanese Patent Publication No. 54-38437 has been known.

This is a device that projects light obliquely onto the eye to be examined and detects the amount of light reflected from the cornea.The setting is made so that the amount of reflected light is maximized when the cornea is flattened, and airflow is blown onto the eye to be examined to flatten the cornea. The method is to know the spray pressure at which the eye is blown and convert it to intraocular pressure.

Here, the airflow pressure is set in advance as a function of time so that it forms a predetermined curve (mountain shape), the time interval until the cornea becomes flat is determined, and the conversion is performed in the order of time → airflow pressure → intraocular pressure. .

However, this conventional device instantly applies a high airflow pressure until the cornea of the affected eye is flattened, causing discomfort and fear.

In view of the above points, it is an object of the present invention to provide a device that can measure intraocular pressure at low airflow pressure without causing discomfort.

Note that the present invention is a non-contact intraocular pressure measuring device, which eliminates the trouble of corneal anesthesia and eliminates concerns about infection. In order to achieve the above object, the present invention is characterized in that the intraocular pressure is measured by blowing gas at a constant pressure and detecting a change in the reflection angle of the corneal projection light beam due to the deformation of the cornea.

Examples of the present invention will be shown below.

In FIG. 1, light emitted from a light source 1 that emits infrared light, etc. passes through a lens 2 and an aperture (not shown), becomes a narrow luminous flux, hits the cornea C of the eye to be examined, is reflected here, and passes through a lens 8 to the optical position. This leads to the detector 6. This optical position detector 6 is, for example, a so-called semiconductor optical position detector that detects the position of a light spot using the electric resistance of a semiconductor.

Here, the cornea of the eye to be examined receives light from the light source 1 and receives an air flow from the air nozzle 7.

When a constant pressure air stream is blown onto the cornea C from the air nozzle 7, the cornea deforms from C to C'.
Due to this deformation, the corneal reflected light flux changes from light flux 4 to light flux 5 and is deviated from position 4' to position 5' on position detector 6.

Here, the amount of corneal deformation is related to the pressure within the eyeball, that is, the intraocular pressure; the higher the intraocular pressure, the less deformation, and the lower the intraocular pressure, the greater the deformation.

Further, the angular change θ of the reflected light beam before and after the corneal deformation corresponds to the change in the position of the light spot on the optical position detector 6. Therefore, by applying a constant airflow pressure and measuring the change in angle of the corneal reflected light beam, that is, the change in the position of the light spot on the light position detector 6, the intraocular pressure can be determined. The light spot position change is related to the intraocular pressure, and this position change is calibrated as a measurement standard for the intraocular pressure. If the direction of the projected light flux is made equal to the airflow jetting direction of the air nozzle, even if the distance between the cornea C and the device deviates slightly, the position where the cornea's airflow hits and the position where the light flux hits will be kept at a constant distance. There is no error. In order to easily accomplish this, the light source 1 and lens 2 may be provided integrally with the air nozzle 7.

In addition, in detecting the reflected light, by providing the optical position detector 6 at the back focal position of the lens 8, the angle change θ of the reflected light flux and the change in the position of the light flux on the optical position detector 6 x
can be kept in a proportional relationship. That is, if the focal length of the lens 8 is x=θ.

Furthermore, if the light source 1 is provided at the focal position of the lens 2 and the optical position detector 6 is provided at the focal position of the lens 8, changes in the working distance from the eye to be examined will no longer affect measurement errors.

In the figure, the lens 8 and the optical position detector 6 are spatially provided in one predetermined direction, but a plurality of lenses may be provided, for example, at three locations every 120° in the circumferential direction, on the circumference centered on the eye axis to be examined. Also good. By measuring multiple locations,
It is expected that measurement accuracy will improve.

In this case, light source 1 and lens 2 are also lens 8,
A plurality of optical position detectors 6 are provided at corresponding predetermined positions.

Further, instead of providing a plurality of lenses 8, a single annular cylindrical lens may be provided. This annular cylindrical lens has refractive power in each meridian direction, and has no refractive power in a direction perpendicular to the meridian direction, that is, in the circumferential direction.

Figure 2 shows the change in the position of the reflected light beam when airflow is blown.

The horizontal axis shows time t, and the vertical axis shows light spot position x. Initially, the light spot was located at position 4', but as pressure was applied to the cornea of the subject's eye by the airflow, the light spot position gradually changed until it reached position 5', and then returned to its original position 4' due to the release of the airflow. Return to

As described above, according to the present invention, since the detection is performed not by the change in the amount of reflected light but by the change in the angle of the reflected light flux, it is possible to easily measure intraocular pressure with extremely high sensitivity and a small constant air flow pressure. It has no fear and is useful in the field of ophthalmology.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing temporal changes in the position of the optical position detector of the corneal reflected light flux due to air flow pressure. In the diagram, 1 is a light source, 2 is a lens, and 3 is the incident luminous flux,
4 and 5 are reflected light beams, 6 is an optical position detector, 7 is an air nozzle, 8 is a lens, and C and C' are the cornea of the eye to be examined.

Claims (1)

[Scope of Claims] 1. A means for blowing an airflow at a constant pressure onto the cornea of the eye to be examined; a means for projecting a light beam onto the cornea of the eye to be examined; and a means for detecting a change in the direction of reflection of light reflected from the cornea before and after blowing the airflow at a constant pressure. An intraocular pressure measuring device having a means for measuring intraocular pressure. 2. The intraocular pressure measuring device according to claim 1, wherein the corneal reflected light is detected by an optical position detector provided at a rear focal position through a lens. 3. The intraocular pressure measuring device according to claim 2, wherein the light beam projected onto the cornea of the eye to be examined is a parallel light beam. 4. The intraocular pressure measuring device according to claim 1, wherein the direction in which the airflow is blown and the direction in which the luminous flux is projected are the same. 5. The intraocular pressure measuring device according to claim 4, in which means for blowing airflow at a constant pressure and means for projecting a luminous flux are integrated. 6. The intraocular pressure measuring device according to claim 1, wherein a plurality of means for detecting changes in the direction of reflection of corneal reflected light are provided on a circumference centered on the axis of the eye to be examined.