JPS63283621A - Non-contact type tonometer - Google Patents

Abstract

PURPOSE:To take-in clean air having no scattered tear mixed therein to inject the same, by providing a valve having an air suction port lower in air inflow resistance than an air jet nozzle to a compression chamber and providing an air suction port to the housing of a tonometer. CONSTITUTION:A rotary solenoid 1 rotates and a piston 4 advances to a position 4a to inject the air in a compression chamber 6 to the cornea Ec of an eye E to be examined from a nozzle 8 and, when the piston 4 begins to return to the original position, the compression chamber 6 becomes negative pressure. Hereupon, an one-way valve 10 is pushed by atmospheric pressure and overcomes the force of a return spring 11 to open. When the one-way valve 10 is opened, the open air is automatically sucked in the compression chamber 6 from an air suction port 12 lower in air inflow resistance than the nozzle 8. By this method, air reduced in the mixing with a tear can be injected at the time of the next injection of air.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a non-woven fabric that deforms the cornea by blowing air onto the cornea of the eye to be examined, and optically detects the deformation to measure intraocular pressure. This invention relates to a contact tonometer.

[Prior Art] In this type of conventional tonometer, an air pulse is injected onto the cornea of the eye to be examined from the axial direction of the device, and the intraocular pressure is measured based on the time taken until the cornea is applanated. Generally, as illustrated in FIG. 4, this air pulse injection mechanism rotates a rotary solenoid l by a certain angle to advance a piston 4 to a position 4a via an arm 2 and a piston rod 3, thereby causing the piston 4 in the cylinder 5 to move forward. Air is compressed in a compression chamber 6, and air pulses are ejected from a nozzle 8 provided at the center of an objective lens 7 toward the cornea Ec of the eye E to be examined.

After the air is injected, when the piston 4 returns from the position 4a to its original position, external air is automatically sucked through the nozzle 8 and used for the next injection. Note that 9 is a transparent plate that covers a portion corresponding to the optical axis of the compression chamber 6 and allows the light beam to pass during detection.

In this way, in the conventional device, since the air sucked in from the nozzle 8 is injected, there is a high possibility that the dust sucked in with the air may be blown onto the cornea Ec and damage the cornea Ec. Moreover, when the air pulse is ejected, the tears in the eye E to be examined are scattered, and the scattered tears are sucked into the compression chamber 6 from the nozzle 8 and sprayed onto the eyes of the next patient. There are also hygiene issues.

[Object of the invention] The object of the present invention is to improve the drawbacks of the conventional example, to introduce clean air that is not mixed with scattered tears, etc.
An object of the present invention is to provide a non-contact tonometer capable of spraying.

[4I of the Invention] The gist of the present invention for achieving the above-mentioned object is a non-contact method in which air in a cylinder is compressed by a piston, and compressed air is injected from a compression chamber communicating with the cylinder to the eye to be examined through a nozzle. In the type tonometer, the compression chamber is provided with a valve that opens when the inside of the compression chamber becomes negative pressure, and the air inflow resistance of the air intake port opened and closed by the valve is expressed as the air inflow resistance of the nozzle. This is a non-contact tonometer characterized by being smaller than the previous model.

[Embodiments of the Invention] The present invention will be described in detail based on embodiments illustrated in FIGS. 1 to 3.

FIG. 1 shows an air pulse injection mechanism of a non-contact tonometer according to the present invention, and the same reference numerals as in FIG. 4 represent members having the same functions.

In this embodiment, a one-way valve 10 is attached to the wall of the compression chamber 6, and the one-way valve 10 opens due to the pressure difference with the outside atmospheric pressure when the inside becomes negative pressure. This one-way valve lO is normally operated in a direction to close the air intake port 11 by a return spring 11.

Furthermore, the air inflow resistance of the air intake port 12 that is opened and closed by the one-way valve lO is sufficiently smaller than that of the nozzle 8.

In the embodiment shown in FIG. 1, after the rotary lens l rotates and the piston 4 advances to the position 4a, and the air in the compression chamber 6 is injected from the nozzle 8 to the cornea Ec of the eye E,
When the piston 4 begins to return to its original position, the pressure inside the compression chamber 6 becomes negative. The one-way valve lO is then pushed by atmospheric pressure, overcomes the force of the return spring 11, and opens. When the one-way valve lO opens, external air is automatically sucked into the compression chamber 6 through the air suction port 12, which has a lower air inflow resistance than the nozzle 8. In this way, the next air injection can be performed with air that is less contaminated with tears.

Note that it is desirable that the one-way valve lO be installed at a location far from the nozzle 8;
This is because the nearby air contains scattered tears from the eye E to be examined and contains a lot of dust. On the other hand, since the air far away from the nozzle has fewer tears, if the one-way valve IO is installed near the nozzle 8, clean air with less tears can be inhaled.

FIG. 2 shows another embodiment of the present invention. In this case, internal negative pressure is detected by a pressure sensing element 13 provided in the compression chamber 6 or cylinder 5, and is outputted via a controller 14 and a linear solenoid 15. An example of opening the directional valve 10 is shown. Note that 16 is a mounting base for the linear solenoid 15.

After the piston 4 enters the position 4a and injects compressed air from the nozzle 8, when the pressure inside the compression chamber 6 becomes negative while the piston 4 returns to its original position, the pressure sensing element 13 detects this negative pressure. A signal is sent to the controller 14, and the controller 14 uses the signal to cause a current to flow through the straight solenoid 15, thereby opening a one-way valve IO directly connected to the straight solenoid 15. When the one-way valve 10 opens, the inside of the compression chamber 6 communicates with outside air through the air intake port 12t, so that outside air is sucked into the negative pressure cylinder 5.

FIG. 3 shows still another embodiment, in which a filter 17 is attached near the air intake port 12 so that the filter 17 can remove dust and the like from the introduced air. In the case of FIG. 3, a filter 17 is added to the embodiment shown in FIG. 1, but it goes without saying that such a filter 17 can also be added to the embodiment shown in FIG. It is also possible to install the one-way valve 10 and the air intake port 12 on the piston 4, but in order to reduce the piston weight and increase the piston speed, it is better to install them on the cylinder 5 or compression chamber 6 side. It is.

[Effects of the Invention] As explained above, the non-contact tonometer according to the present invention has a valve in the compression chamber that has an air inlet having a smaller air inflow resistance than an air injection nozzle, so that airborne particles from the subject's eye can be prevented. Tears can be prevented from being sucked in from the air injection nozzle. Further, by providing this valve with an air inlet in a tonometer housing with little dust, it becomes possible to take in and inject clean air.

[Brief explanation of the drawing]

Drawings 1 to 3 show examples of the non-contact tonometer according to the present invention, and Figs.
FIG. 4 is a sectional view of the second and third embodiments, and FIG. 4 is a sectional view of the conventional example. Symbol l is rotary linenoid, 4 is piston, 5 is cylinder, 6 is compression chamber, 8 is nozzle, lO is one-way valve, ll
12 is a return spring, 12 is an air intake port, 13 is a pressure detection element, 14 is a control controller, 15 is a linear solenoid, 1
7 is an air filter. Patent applicant Canon Co., Ltd. Drawings Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. In a non-contact tonometer in which air in a cylinder is compressed by a piston and the compressed air is injected from a compression chamber communicating with the cylinder to the subject's eye through a nozzle, the inside of the compression chamber is negative. A non-contact device characterized in that the compression chamber is provided with a valve that opens when the pressure is increased, and the air inflow resistance of the air intake port that is opened and closed by the valve is smaller than the air inflow resistance of the nozzle. type tonometer. 2. The non-contact tonometer according to claim 1, wherein the valve is opened at atmospheric pressure by a pressure difference between the inside and outside of the compression chamber. 3. The non-contact tonometer according to claim 1, wherein the valve detects negative pressure by a pressure detection element provided in the compression chamber and is opened by a solenoid. 4. The non-contact tonometer according to claim 1, comprising an air filter that cleans the air introduced from the valve.