JP3379719B2 - 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 the eye to be inspected by blowing compressed fluid onto the eye to deform the cornea and detecting the deformed state.

[0002]

2. Description of the Related Art In this type of non-contact tonometer, it is necessary to accurately align the tip of a nozzle for blowing compressed gas with the eye to be examined. The alignment was performed as follows, for example. Form a corneal reflection image by projecting a light beam onto the eye to be inspected, and while observing the position with the anterior segment of the eye to be inspected, move the device with respect to the eye to perform rough alignment, and The alignment state is detected by receiving the light flux with a photodetector. When the alignment is completed, the examiner presses the trigger switch or automatically shifts to the measurement. However, even if the alignment is performed accurately once, there may be a case where the alignment shift occurs during the measurement. For such a case, an apparatus has been proposed which monitors the alignment state during measurement and displays an error when an alignment deviation occurs. Since compressed gas is blown to the eye to be inspected during measurement and the eye to be inspected is deformed, it is not possible to adopt the same method as the determination of the alignment state before measurement, for example, when the normal time required for corneal deformation has elapsed. The amount of alignment light is measured, and it is determined whether or not an alignment deviation has occurred depending on whether or not the amount of light has a certain level.

[0003]

However, according to the method of previously setting the threshold value of the alignment light amount to be constant, the alignment light amount is uniformly set without reflecting the individual difference of the reflected light amount of the alignment. In the case of an optometry, there is a problem that it is judged as an alignment error and measurement data cannot be obtained.On the other hand, in the case of an eye to be inspected with a large amount of reflected light, it is possible to measure the correct alignment state even when there is an alignment error. There was a problem of being judged. The present invention has been devised in view of the drawbacks of the above conventional apparatus, and provides a non-contact tonometer that can accurately determine the quality of the measurement result even if there is individual difference in the alignment detection light amount of the patient's eye. This is a technical issue.

[0004]

In order to solve the above problems, the present invention is characterized by having the following configuration. (1) The alignment light beam is projected onto the eye to be examined,
The corneal reflected light of the luminous flux is received by the photodetector and
Element status is detected and the alignment completion signal is obtained.
And blow the gas toward the cornea of the eye
The non-contact tonometer for measuring the intraocular pressure of the eye by obtaining the pressure of the gas when deformed in alignment
Peak of received light received by the photodetector at completion
Based on the memory that stores the value and the peak value, the gas pressure
Setting of the measurement error threshold corresponding to the change stage of
Measuring means and the amount of light received by the photodetector after the start of measurement.
Monitor to check whether the measurement error falls below the threshold.
And a visual means .

(2) Alignment light flux is projected onto the eye to be examined.
Then, the cornea reflected light of the alignment light flux is detected by the photodetector.
Detects the alignment state by receiving light to complete the alignment.
After receiving the end signal, blow gas onto the cornea of the subject's eye,
By obtaining the pressure of the gas when it is deformed into a predetermined shape
In a non-contact tonometer that measures the intraocular pressure of the eye to be examined,
Light received by the photodetector at the completion of the license
A memory to store the peak value of the quantity and a gas from the beginning of the measurement.
Of the peak before and after the start of blowing the gas.
Setting the threshold of measurement error by changing the ratio to the measurement value
Set the amount of light received by the photodetector after the start of measurement
Detect and monitor whether it falls below the measurement error threshold
And a monitoring means .

[0006]

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an optical system and a control system of the apparatus of this embodiment. Reference numeral 1 denotes a piston, which is operated by a crank 2 driven by a solenoid (not shown),
The piston 1 reciprocates in the compression chamber 3. The compressed air is jetted from the nozzle 4 and deforms the cornea Co of the eye to be inspected.
Reference numeral 5 denotes a pressure sensor that detects the pressure inside the compression chamber 3.
Reference numerals 6 and 7 denote transparent glass plates, which hold the nozzle 4 and transmit observation light and alignment light, and also serve as side walls of the compression chamber. Reference numeral 8 denotes a glass plate provided on the back surface of the nozzle 4, which constitutes a rear wall of the compression chamber and transmits observation light and alignment light of the eye to be inspected. Reference numeral 9 denotes an alignment LED that emits near-infrared light. The alignment light emitted from the LED 9 is collimated by the collimating lens 10 and then reflected by the half mirror 11 in the optical axis direction. The alignment light reflected by the half mirror 11 passes through the glass plate 8, the nozzle 4 and the like, and is irradiated on the cornea Co of the eye to be inspected to form a cornea reflection image. The alignment light reflected by the cornea Co of the eye to be examined passes through the glass plates 6 and 7, the half mirrors 11 and 12, and the like, and a relay lens 13 and an imaging lens 14 form a cornea reflection image on the light receiving portion of the television camera 15. Image. The TV camera 15 also photographs the anterior segment of the eye to be inspected, and the TV monitor 16
To be used for alignment. The examiner can know the alignment state by observing the positional relationship between the anterior segment image of the eye to be inspected displayed on the television monitor 16 and the corneal reflection image with respect to the reticle (not shown) and the image formation state thereof.

The alignment light reflected by the half mirror 12 is condensed by a condenser lens 17, passes through a pinhole plate 18, and is received by a detector 19. The alignment state between the eye to be inspected and the device is detected by the amount of light received by the detector 19. Reference numeral 20 denotes an LED for detecting the corneal applanation, and the light emitted from the LED 20 is collimated by the collimating lens 21. The light reflected by the cornea Co is condensed by the condenser lens 22, passes through the pinhole plate 23, and is received by the detector 24. The optical system for detecting the corneal applanation is arranged so that the detector 24 detects the maximum light amount when the eye to be inspected is in a predetermined applanation state. Pressure sensor 5, alignment detector 19, and applanation detector 2
The signals of No. 4 are converted into digital signals by A / D converters 25, 26 and 27, respectively, and then the interface 28
Is sent to the CPU 29 via. The information processed by the CPU 29 is displayed on the television monitor 16 via the display circuit 30.

Next, the detection of the misalignment by the apparatus having the above-mentioned structure will be described. LED for alignment
The cornea reflection image of the alignment light emitted from 9 is received by the television camera 15 together with the anterior segment of the eye to be inspected, and the inspector
While observing the positional relationship between the anterior eye image of the eye to be inspected displayed on the television monitor 16 and the corneal reflection image with respect to the reticle (not shown) and its image formation state, the joystick (not shown) is operated to the eye to be inspected. Move the measurement unit and adjust the alignment. In addition, the alignment light condensed by the condenser lens 17 and passing through the pinhole plate 18 is detected by the detector 19
Is received and the amount of light is measured. When the amount of light above a predetermined level is obtained, the CPU issues an alignment completion signal, and the measurement automatically starts. The peak value of the amount of light detected by the detector 19 at the time of alignment is stored in the memory and is used as a reference for alignment quality determination. When the alignment is completed and the measurement is started, the piston 1 moves with acceleration by driving a solenoid (not shown), and compressed air is blown onto the cornea Co. The deformed state of the cornea is detected by the detector 24.

FIG. 2 is a diagram showing changes in the air pressure in the compression chamber and changes in the amount of light detected by the detector 24 over time during measurement, where a is a change in pressure for one cycle and the piston 1 is started. After a certain time, the pressure starts to rise. When the signal b from the detector 24 indicates a peak and it is detected that the eye to be inspected is in the applanation state, the drive of the solenoid is stopped,
After that, the air pressure also shows a peak value and then starts to decrease. The pressure value of the air pressure at the timing when the detector 24 detects that the eye to be inspected is in the applanation state is obtained, and the eye pressure is calculated based on this pressure value.

Detection of misalignment during the above measurement operation will be described. The peak value of the light amount detected by the detector 19 stored before the measurement operation and stored in the memory is set as follows in relation to the change in the air pressure in the compression chamber. In this embodiment, a value obtained by multiplying the peak light quantity at the time of initial alignment by a coefficient determined according to the stage of change of the air pressure in the compression chamber is determined as a threshold value for the alignment deviation determination, and a detector is used for this threshold value. It is monitored whether or not the detected light amount of 19 does not decrease. Assuming that the peak value of the amount of light received by the detector 19 during alignment is A1,
Since the change in the amount of light received by the detector 19 is relatively small even after the alignment shift occurs after the piston is started and before the pressure is started, A1 × 0.8 is set as the threshold value. The threshold value during the pressure change after the start of the pressure is affected by the corneal deformation and the detector 19
Since the fluctuation of the amount of received light of A is large, the value is A1 × 0.5. In this way, the misalignment during the measurement is detected, and when the misalignment occurs, the error is detected.
Etc. are displayed. In this way, the threshold value is set according to the individual difference in the reflection of each cornea and the stage of the measurement operation, so that the misalignment of alignment can be accurately detected. In the above example, the coefficient is set to be different before and during the pressure change in the compression chamber, but these settings can be changed in various ways.

[0012]

According to the present invention, A during measurement operation
Since it is possible to detect the deviation of the alignment according to the change in the amount of alignment light received by each patient's eye , the quality of the measurement result can be judged more fairly, and the measurement accuracy is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an optical system and a control system of an apparatus of this embodiment.

FIG. 2 is a diagram showing changes in air pressure in the compression chamber and changes in the amount of light detected by the detector over time during measurement.

[Explanation of symbols]

1 piston 3 compression chambers 4 nozzles 5 Pressure sensor 9 LED for alignment 15 TV camera 16 TV monitor 19 Alignment detector 20 LED 24 Applanation detector 29 CPU 30 Display circuit

Claims (2)

(57) [Claims] 1. An alignment light beam is projected onto an eye to be examined,
The photodetector receives the corneal reflected light of the alignment light beam.
Alignment complete signal
And then blow the gas toward the cornea of the eye to be examined,
The non-contact tonometer for measuring the intraocular pressure of the eye by obtaining the pressure of the gas when deformed into a shape, Alignment
Of the amount of light received by the photodetector when the
Based on the peak value and the memory that stores the peak value.
Set the threshold for measurement error corresponding to the stage of change in body pressure
Setting means and the amount of light received by the photodetector after the start of measurement
Is detected to monitor whether the measurement error falls below the threshold.
Noncontact tonometer characterized in that it comprises a monitoring unit, the that. 2. An alignment light beam is projected onto an eye to be inspected,
The photodetector receives the corneal reflected light of the alignment light beam.
Alignment complete signal
And then blow the gas toward the cornea of the eye to be examined,
Tested by obtaining the gas pressure when deformed into a shape
A non-contact tonometer that measures the intraocular pressure of the eye
Of the amount of light received by the photodetector when the
Memory that stores the peak value and blowing of gas from the start of measurement.
The peak value is reached before the start of the application and after the start of blowing the gas.
Setting procedure to set the threshold of measurement error with different ratio
And the amount of light received by the photodetector after starting measurement.
Monitor to check whether the measurement error falls below the threshold value.
Noncontact tonometer characterized in that it comprises a stage, a.