JP3359712B2 - Non-contact tonometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact tonometer for measuring the intraocular pressure of a subject's eye by blowing a compressed gas to the subject's eye to deform the cornea and detecting the deformed state.

[0002]

2. Description of the Related Art A mechanism as shown in FIG. 4 is known as a mechanism for injecting a compressed gas of a non-contact type tonometer of this kind. The piston 2 in the cylinder 1 is pushed up by a drive mechanism (not shown) at the start of the measurement. The side wall of the air compression chamber 3 communicating with the cylinder 1 is constituted by a perforated glass 5 holding a nozzle 4 and a rear window 6 made of a transparent plate. The rear window 6 is on the axis L of the nozzle 4, and behind the rear window 6, an optical system group 7 such as an observation optical system, a position adjustment optical system, a fixation optical system, and a measurement optical system is arranged. Pass through the rear window 6. When the measurement is started, the piston 2 moves to a position shown by a dotted line in the cylinder 1, whereby the air in the cylinder 1 is compressed in the air compression chamber 3 and is blown from the nozzle 4 to the cornea Ec of the eye to be examined. After the air injection, the piston 2 returns to the initial position, and at this time, air for the next measurement is sucked from the nozzle 4.

[0003]

When the piston 2 returns to the initial position in the above apparatus, the pressure in the air compression chamber 3 is reduced. With the decompression in the air compression chamber 3, part of secretions such as tears scattered by blowing compressed air to the cornea Ec to be examined easily flows from the nozzle 4 into the air compression chamber 3. The tears and the like that have flowed in the nozzle 4 in the air compression chamber 3
May be attached to the inside of the rear window 6 positioned on the axis L, and the transmittance of the position adjustment light beam, the measurement light beam, and the like passing through the rear window 6 may be reduced, which may hinder the measurement. Although dirt such as tears also adheres to the front of the perforated glass 5, this is a place that can be seen by the inspector, and it is easy to determine whether or not to perform cleaning. On the other hand, since the rear window 6 is inside the apparatus and is hardly touched by the inspector, dirt is easily left behind, and the inspector may not notice until a measurement error such as an alignment error occurs. As means for detecting dirt on the optical system,
It is also known that a lens cap with a mirror is placed in front of the nozzle to return the luminous flux from the optical system into the device and to detect dirt etc., but it takes time to attach and remove the lens cap. In addition, it is troublesome to inspect for dirt while the measurement is being performed for a long time, and the mirror surface of the removed lens cap must be kept clean. The present invention has been devised in view of the above-described drawbacks, without bothering the inspector,
An object of the present invention is to provide a non-contact tonometer capable of detecting the degree of contamination of an optical element at the rear of an air compression chamber.

[0004]

Means for Solving the Problems In order to solve the above problems, the present invention has the following features. (1) In a non-contact tonometer for holding a nozzle and having a perforated glass forming a side wall and a rear window provided on a rear portion thereof and blowing a compressed gas from the compression chamber to a subject's eye through the nozzle, Without passing through the perforated glass, the center of the axis of the nozzle is centered on the inner diameter of the nozzle.
Light emitting means for emitting measurement light toward the corresponding portion of the rear window, light amount detection means for detecting the light amount level of the measurement light transmitted through the rear window, and light amount level detected by the light amount detection means And a detecting means for detecting the dirt on the rear window by comparing with a predetermined light amount level.

[0005]

[0006]

[0007]

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of the vicinity of the air compression chamber of the present embodiment. It should be noted that the same members as those in FIG. 4 described above are denoted by the same reference numerals, and description thereof will be omitted. Numeral 11 denotes an infrared light emitting diode having a lens at the tip and having a high directivity, which is embedded in the cylinder 1 so as to transmit the light flux near the intersection of the axis L of the nozzle 4 and the rear window 6 so as to transmit the light. I have. Reference numeral 12 denotes a light receiving element for detecting the amount of light,
Are arranged on the light emitting axis M of the light emitting diode 11 passing through the light emitting diode 11. The tears or the like flowing from the nozzle 4 are concentrated around the axis L in a range corresponding to the inner diameter of the nozzle 4 and the rear window 6.
Therefore, the light receiving element 12 is disposed at a position where at least the transmitted light flux in the range is received. Note that the positions of the infrared light emitting diode 11 and the light receiving element 12 may be reversed. Each time the measurement of the intraocular pressure is completed and the piston 2 returns to the initial position, the infrared light emitting diode 11 and the light receiving element 12 operate to automatically detect the contamination of the rear window 6.

FIG. 2 is a block diagram of a control system for light amount detection. Reference numeral 21 denotes a detection circuit that processes a light amount signal obtained by the light receiving element 12, and reference numeral 22 denotes a microcomputer that controls the entire apparatus. Reference numeral 23 denotes a display for displaying a warning that the rear window 6 needs to be cleaned. Light receiving element 12
Is input to the microcomputer 22 via the detection circuit 21. FIG. 3 is a diagram showing an output waveform of the light amount obtained by the light receiving element 12, wherein a denotes a state in which the rear window 6 is not stained, and the light amount level is I1. In the state b, the output of the light receiving element 12 is reduced due to the contamination of the rear window 6, and the light amount is reduced to the light amount level I2 at which the measurement error of the optical system group 7 occurs. By comparing the light amount level of the output waveform obtained from the light receiving element 12 with I1 and I2, the degree of contamination of the rear window 6 can be known.
Here, before the light amount level decreases to I2, a light amount level I0 serving as a criterion for notifying the inspector of the timing of cleaning the rear window 6 is set and stored in the microcomputer 22. The microcomputer 22 includes the light receiving element 1
2 is compared with I0, and if it is determined to be less than I0, a signal is sent to the display 23, and
3 issues a warning that the rear window 6 is dirty and needs to be cleaned.

The above embodiment can be variously modified.
For example, the optical element portion corresponding to the rear window 6 according to the embodiment of the present invention, proposed by the present applicant in Japanese Patent Application No. 5-128355 (name of the invention, "non-contact tonometer"), is detachable from the compression chamber 3. By adding the function, the cleaning is facilitated and a more advantageous device can be obtained.

[0011]

According to the present invention, the degree of contamination of the optical element at the rear of the air compression chamber can be automatically detected without any trouble of the inspector , and the cleaning time can be notified.
it can.

[Brief description of the drawings]

FIG. 1 is a side sectional view of the vicinity of an air compression chamber of the present embodiment.

FIG. 2 is a control block diagram of a light amount detection of the present embodiment.

FIG. 3 is a diagram showing an output waveform of a light amount obtained by a light receiving element 12.

FIG. 4 is a side sectional view showing the vicinity of an air compression chamber of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Air compression chamber 4 Nozzle 5 Perforated glass 6 Rear window 7 Optical system group 11 Infrared light emitting diode 12 Light receiving element

Claims (1)

(57) [Claims] 1. A non-contact tonometer for holding a nozzle and having a perforated glass forming a side wall and a rear window provided at a rear portion, and blowing a compressed gas from the compression chamber to the eye to be examined through the nozzle. In the above, without passing through the perforated glass , inside the nozzle around the axis of the nozzle
Light emitting means for emitting measurement light toward the rear window of a portion corresponding to a diameter, light quantity detection means for detecting the light level of the measurement light transmitted through the rear window, and light quantity detected by the light quantity detection means Detecting means for comparing the light amount level with a predetermined light amount level to detect dirt on the rear window.