JPS6159138B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Intraocular pressure measurement is essential for early detection of glaucoma. The object of the present invention is to obtain a tonometer that can measure intraocular pressure in a non-contact manner.

Conventional tonometers of this type include the Schietz tonometer, which applies a constant pressure to the cornea to deform it, and estimates intraocular pressure from the amount of deformation; and the Sietstsu tonometer, which estimates intraocular pressure from the pressure when the cornea reaches a specific amount of deformation. There are Goldmann tonometers, tonometers that estimate intraocular pressure based on the time it takes for the cornea to reach a specific amount of deformation, etc.

However, since all tonometers bring the instrument into contact with the cornea, they have drawbacks such as corneal anesthesia, disinfection of the instrument, and long measurement time, which is also painful for the subject.

It is a known fact that when waves such as light and sound waves are reflected or absorbed, a pressure called radiation pressure is applied to the reflecting or absorbing surfaces. The present invention utilizes this physical phenomenon to eliminate the above-mentioned drawbacks, and involves emitting sound waves onto the cornea, reflecting the sound waves from the cornea, and detecting the amount of corneal deformation in a non-contact manner. This is a tonometer featuring:

The embodiments shown in the drawings will be described below. 1st
The figure is a diagram showing the principle of a tonometer embodying the present invention. The sound waves from the sound wave transmitter 24 are transmitted to the concave sound wave reflection plate 2.
6. The sound waves are focused on the cornea 1-a of the human eye 1 through the planar sound wave reflection plates 27 and 28. The cornea 1-a
The sound wave reflected from the sound wave transmitter 24 is received by the sound wave receiver 25 located very close to the sound wave transmitter 24 via the above-mentioned reflecting plates 26 to 28 . The above sound wave reflection plate 2
8 is made of a flat plate of acrylic, for example, and transmits the light beam 6 and reflects the sound wave beam 29. The light beam 6 enters the examiner's eye 5 through an observation optical system consisting of an objective lens 2, a relay lens 3, and an eyepiece 4, and is observed and aligned. 30 is an electric control processing circuit that controls the sonic wave transmitter 24 and processes the signal received by the sonic wave receiver 25; 31 is a display device such as an LED or a printer that displays the output contents of the circuit 30; .

FIG. 2 is a detailed diagram of the electrical control processing circuit 30, and FIGS. 3B to 3M are voltage waveform diagrams of each part of the circuit B to M. Next, the operation of the tonometer according to the embodiment will be explained based on FIGS. 2 and 3. The output from the oscillator 32, which produces the frequency of the sound wave, is transmitted to the clock pulse oscillator 3.
3 passes through the gate 34 only during the period when the clock pulse (FIG. 3-B) is outputted from the amplifier 36.
is amplified and drives the sound wave oscillator 24 to emit sound waves. This amplifier 36 is connected to the contact a of the switch 52.
The amplification factor can be changed by switching to side or side b, and normally the switch 52 is connected to the contact a side so that the sound wave is strong enough not to affect the cornea 1-a. The amplification factor has been suppressed to make it more accurate. (Figure 3-C-a).

The sound waves emitted from the sound wave oscillator 24 are focused on the cornea 1-a as described above, and the sound waves reflected from the cornea 1-a are transmitted to the sound wave receiver 2 after T ₁ hour (FIG. 3).
Received at 5. The output of this sonic wave receiver 25 is amplified by an amplifier 37 (D in FIG.
After that, it becomes a rectangular wave as shown in Fig. 3-E.

On the other hand, some of the sound waves emitted from the sound wave transmitter 24 are
It is reflected by the reflector plate 26 (Fig. 1) and received by the sound wave receiver 25 (Fig. 3-D c) after T ₀ time (Fig. 3), but this received signal is unnecessary and is removed. Should. For this purpose, the monostable multivibrator 41 is activated by the clock pulse,
A pulse with a time width t _ioh (Fig. 3- _F ) is generated, and the pulse is inverted by an inverter 42 to control the opening and closing of the gate circuit 43. Things should not be allowed to pass through the gate circuit 43,
The unnecessary received signals mentioned above are eliminated.

The output of the flip-flop 44, which is inverted in response to a clock pulse, has a clock pulse width t due to a signal obtained by inverting the clock pulse by an inverter 45.
The pulse width corresponding to _w is removed and output from the gate circuit 46 (FIG. 3-J).

The output of this gate circuit 46 is a diode 47,
An integrating circuit consisting of a resistor 48 and a capacitor 49 integrates the time (T ₁ - T _w ) until the output (Fig. 3-G) comes out from the gate circuit 43, and integrates the time when the output comes out from the gate circuit 43. The value is held in the sample hold circuit 51 and shown in Figure 3-K.
It becomes V ₁ . The output from gate circuit 43 also inverts flip-flop 44. The output V ₁ of the sample and hold circuit 51 is stored in the first storage circuit 53 via a contact a of a switch 52' which is interlocked with the switch 52. The contents of sample and hold circuit 51 are reset when transistor 50 is turned on by a clock pulse.

Next, when the switches 52 and 52' are respectively switched to the contact b side, the amplification factor of the amplifier 36 increases, and the sound waves emitted from the sound wave transmitter 24 are
The cornea 1-a is deformed by the radiation pressure of this sound wave. Deformed cornea 1-
The sound waves reflected from a are received by the sound wave receiver 25 and amplified by the amplifier 37, as shown in FIG. 3-D. In this case, the time T ₂ (FIG. 3) from when the sound wave is transmitted to when it is received is longer than the time T ₁ in the case where the switch 52 is connected to contact a. The value obtained by multiplying 1/2 of this time difference, ie, 1/2 (T ₂ −T ₁ ) by the sound wave velocity becomes the amount of corneal deformation.

The output of the amplifier 37 is (T ₂
-T _w ) time and sampled and held in the sample-and-hold circuit 51 as shown in Fig. 3-K.
It becomes V ₂ . The output of the sample and hold circuit 51 passes through the contact b of the switch 52', and the value of V ₂ is stored in the second storage circuit 54.

Contents of the first and second memory circuits 53 and 54
V ₁ and V ₂ are differentially amplified by a differential amplifier 55, and this output is multiplied by the sound wave velocity in an arithmetic processing circuit 56 to calculate the amount of corneal deformation. This calculation result is displayed on the display 31. Furthermore, the radiation pressure on the cornea can be determined from the magnitude of the sound wave output.

Therefore, when outputting a sound wave with a constant intensity as shown in the figure, the intraocular pressure can be estimated based on the magnitude of the amount of deformation, and when changing the sound wave output, the sound wave output when a constant amount of deformation is obtained. Intraocular pressure can be estimated from The tonometer of the present invention can detect intraocular pressure in a non-contact manner, and does not have any of the disadvantages of the conventional contact-type tonometers.

Furthermore, compared to non-contact detection of intraocular pressure using air pulses, the pressure burden on the eye to be examined is reduced by repeating pressurization and negative pressure using sound waves, which are compression waves. Furthermore, when air pulses are used, it is difficult to use a focusing system, but according to the present invention, the corneal deformation efficiency can be improved by using a sonic focusing system.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the principle of the tonometer of the present invention, FIG. 2 is a block diagram of an electrical control processing circuit that forms the main part of the tonometer, and FIG. 3 is a voltage waveform diagram of each part of the circuit. 1 is the subject's eye, 1-a is the cornea, 2, 3, and 4 are lenses, 5 is the examiner's eye, 24 is a sound wave transmitter, 25 is a sound wave receiver, 26, 27, and 28 are sound wave reflectors, and 30
31 is an electric control processing circuit and a display device.

Claims (1)

[Scope of Claims] 1. A deforming means for deforming the cornea of the eye to be examined with a pressure that is constant or variable over time, and a detection means for detecting the amount of deformation of the cornea of the eye to be examined before the deformation, In a tonometer that calculates an intraocular pressure value from the amount of corneal deformation at the bottom or the pressure or time that causes a certain corneal deformation, the deforming means is characterized by comprising a sound wave focusing system that focuses sound waves on the cornea of the eye to be examined. tonometer. 2. The detection means detects the amount of deformation of the cornea of the eye to be examined by determining the time interval from the transmission of the sound wave to the reception via reflection of the cornea of the eye to be examined before and after the deformation of the cornea of the eye to be examined. tonometer.