JPH0542109A - Contactless type tonometer - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the burden on the subject during intraocular pressure measurement while maintaining high measurement accuracy. A non-contact tonometer is provided with a fluid discharge stopping means for stopping discharge of fluid from the fluid discharging means before the amount of received light exceeds a peak.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention discharges a fluid to the corneal surface of an examinee to applanate the corneal surface, and measures the intraocular pressure of the eye to be inspected based on the fluid discharge pressure during the applanation. The present invention relates to a contact tonometer.

[0002]

2. Description of the Related Art Conventionally, as a non-contact tonometer, a fluid is discharged onto the corneal surface of a subject to applanate the corneal surface, and the intraocular pressure of the eye to be examined is measured based on the fluid discharge pressure during the applanation. It is known to measure.

In this non-contact tonometer, the cornea is irradiated with light and air is blown onto the cornea while detecting the light reflected by the cornea. When air is blown from the air blowing nozzle onto the corneal surface, the corneal surface is removed. When the amount of reflected light from the cornea is increased by applanation and part of the cornea becomes flat, the amount of reflected light reflected by the cornea shows a peak, and when air is continuously blown,
The corneal surface is depressed and the amount of reflected light is reduced again.

The stop of blowing air is stopped when the light amount level falls below a predetermined signal level in the reduced state after the peak. The intraocular pressure of the subject is measured based on the air blowing pressure at which the peak pressure is exhibited.

[0005]

However, since the conventional non-contact tonometer stops blowing air when the level of the amount of light reflected by the cornea falls below a predetermined level in the post-peak decreasing level, There is a problem that the fluid is continuously discharged from the flat state of the cornea until it is further recessed, which imposes a heavy burden on the subject.

[0006]

It is an object of the present invention to provide a non-contact tonometer which maintains the high measurement accuracy and has a small burden on the subject when measuring the tonometry. And

[0007]

In order to solve the above-mentioned problems, the present invention provides a fluid discharge means that is driven in accordance with the completion of alignment of the eye to be examined with respect to the apparatus main body and discharges fluid toward the cornea of the eye to be examined. A corneal deformation detection means for projecting corneal deformation detection light toward the cornea and detecting the deformation of the cornea due to the discharge of the fluid based on a change in the amount of reflected light of the corneal deformation detection light reflected by the cornea; A fluid discharge stopping means for stopping discharge of the fluid before the light amount level of the reflected light of the corneal deformation detection light reaches a peak.

[0008]

According to the non-contact tonometer according to the present invention, the fluid discharge stopping means stops the discharge of the fluid before the light amount of the reflected light of the corneal deformation detection light reflected by the cornea reaches a peak. Without being depressed, the burden on the subject is reduced.
Moreover, since the applanation signal suddenly rises when the amount of received light increases, this means that the discharge pressure when the fluid discharge is stopped and the fluid discharge pressure when it reaches a peak are very similar.
It is possible to maintain the measurement accuracy of intraocular pressure.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-contact tonometer according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of the non-contact tonometer of this embodiment, in which 1 is an eye to be inspected by a subject. The non-contact tonometer of this embodiment includes a fluid ejecting means 2 for ejecting air (fluid) onto the corneal surface 1a, an alignment illumination optical system (not shown) for adjusting alignment of the corneal surface 1a, and air blowing. Applanation detecting means 3 (corneal deformation detecting means) for detecting the applanation state of the corneal surface 1a which is deformed by, and the fluid discharge stopping means 4 for stopping the air blowing of the fluid discharging means 2.
And a fluid ejection circuit (5) for urging fluid ejection means (2) to eject fluid. Alignment illumination optical system, fluid discharge means 2
As the applanation detection means 3, a known one is used. The applanation detection means 3 photoelectrically converts the amount of alignment light reflected by the cornea 1 and outputs it to the fluid discharge stopping means 4.

The fluid discharge stopping means 4 comprises a reference value generating circuit 6
A comparator 7, a flip-flop circuit 8, and an AND circuit 9.

The fluid ejection circuit 5 is operated by an alignment adjustment completion signal of an alignment adjusting means (not shown) related to the alignment illumination optical system, but may be manually operated.

The reference value generating circuit 6 generates a reference value of the detection signal of the applanation detecting means 3. With this reference value, the peak of the light intensity level when the air release was stopped immediately before the flattening of the part of the cornea becomes almost equal to the peak of the light intensity level when the part of the cornea is flattened. The value is set experimentally so that it does not interfere with. The reference value generated in the reference value generation circuit 6 is input to the comparator 7.

The comparator 7 receives the detection signal from the applanation detecting means 3 and the reference value from the reference value generating circuit 6, and performs a comparison calculation between the detection signal and the reference value. The signal transmitted from the comparator 7 to the flip-flop circuit 8 has a waveform as shown in FIG.

The flip-flop circuit 8 is initially set high by a reset and then becomes low when the signal from the comparator 7 rises, and this state is maintained until the next reset. The output signal from the flip-flop circuit 8 is input to the AND circuit 9.

The AND circuit 9 takes the logical sum of the signal from the fluid ejection circuit 5 and the signal from the flip-flop circuit 8. When the signal from the fluid ejection circuit 5 is on, the flip-flop circuit 8 is turned on. When the signal from is high, it is turned on and air is discharged from the fluid discharge means 2 to the corneal surface 1a. On the other hand, when the signal from the flip-prop circuit 8 becomes low, the output signal from the AND circuit 9 to the fluid discharging means 2 becomes low, and the blowing of air from the fluid discharging means 2 is stopped.

In the non-contact tonometer according to this embodiment,
As shown in FIG. 3, the applanation signal of the applanation detection means rises steeply when the corneal surface 1a is applanated by air blowing, and the fall of the applanation signal after the peak becomes gentle. The air blowing time (x) is the time obtained by subtracting the fluid blowing start time (Ts) from the time (Te) when the applanation signal rises above the reference level, but conventionally,
Since the fluid spraying time (x ') is the fluid spraying start time (Ts) from the falling time (Te') of the applanation signal below the reference level, the spraying time of the air space to the subject is It is much shorter than before. Therefore, the burden on the subject is reduced.

Moreover, due to the inertia of the air, the corneal surface is brought into an applanation state suitable for the measurement of intraocular pressure, and the pressure of the air when the detection signal reaches a peak and the pressure of the reference air are extremely close to each other. Therefore, even if the blowing of air is stopped at the level of the reference value before the detection signal rises and then exceeds the peak, the accuracy of intraocular pressure measurement can be sufficiently ensured.

[0019]

According to the non-contact tonometer according to the present invention, since the fluid discharge stopping means for stopping the discharge of the fluid from the fluid discharging means is provided at the increasing stage before the received light amount exceeds the peak, the peak is reduced. The discharge pressure of the indicated fluid can be detected, the measurement accuracy of the intraocular pressure can be maintained, and since the fluid is not discharged until the corneal surface is recessed, the burden on the subject is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a non-contact tonometer according to an embodiment of the present invention.

FIG. 2 is a timing chart of the present embodiment.

FIG. 3 is an explanatory diagram of a waveform of an applanation signal of the non-contact tonometer according to the present embodiment.

FIG. 4 is an explanatory diagram of a waveform of an applanation signal of a conventional non-contact tonometer.

Claims (1)

[Claims] 1. A fluid ejecting means that is driven when alignment of an eye to be inspected with respect to a device main body and emits a fluid toward a cornea of the eye to be inspected, and a corneal deformation detection light is projected toward the cornea to project the fluid. Corneal deformation detection means for detecting the deformation of the cornea due to the emission of the cornea based on the change in the amount of the reflected light of the corneal deformation detection light reflected by the cornea, and the light amount level of the reflected light of the corneal deformation detection light reaches a peak. A non-contact tonometer, characterized in that it further comprises a fluid discharge stopping means for stopping discharge of fluid.