JPH02177934A - Ophthalmologic measuring instrument - Google Patents

Abstract

PURPOSE:To decrease a noise and to improve measuring accuracy by arranging an avalanche photodiode array at the conjugate point of an in-eye prescribed point in a light receiving part and conducting a scattered light from the in-eye prescribed point to the avalanche photodiode array. CONSTITUTION:A laser beam source 4 is lit up, and a laser beam is converged through a lens 5 to a measuring point P of a front chamber 30a. The light scattered at the measuring point P passes through a lens 6, a part of it is directed in the direction of an examiner 13 by a beam splitter 7, and observed through a lens 8, prisms 9 and 10, a visual field diaphragm 11 and a lens 12 by the examiner 13. The scattered light from the measuring point P to be divided by the beam splitter 7 is simultaneously made incident through a lens 14 and an interference filter F on the avalanche photodiode array 15. The scattered light by a cornea, an iris and a crystal lens is measured as a background (noise) through the avalanche photodiode array 15, and by subtracting it from a scattered light intensity from the inside of the front chamber irradiated with the laser beam, the measuring accuracy is further improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an ophthalmological measurement device, and more specifically, to an ophthalmological measuring device, and more specifically, to irradiating a laser beam through an optical system to a predetermined point in the anterior chamber of the eye. It is used in an ophthalmological measurement device that detects scattered light to measure ophthalmological diseases.

[Prior Art] Measurement of anterior chamber protein concentration is extremely important in determining intraocular inflammation, ie, blood chamber. Conventionally, visual judgment by grading using a slit lamp microscope has been widely used, while photometry has been used as a quantitative method.

In addition, in conventional visual judgment, there is a problem that the judgment criteria differs depending on individual differences and the data lacks credibility.
Ophthalmological measurements are carried out by irradiating laser light into the eye and receiving scattered light from it via a photoelectric conversion element and quantifying it.

[Problems to be Solved by the Invention] However, in such an ophthalmological measurement method, when measuring laser scattered light, the reflected and scattered light from the cornea, iris, crystalline lens, or artificial lens after cataract surgery is the same as the laser scattered light. Moreover, since the noise enters the measurement point in the anterior chamber as noise, measurement accuracy deteriorates, and there is a problem that reproducibility of measurement values cannot be obtained.

In order to reduce noise caused by reflected and scattered light entering such measurement points, the device described in JP-A-63-135128 provides a mask in front of the photoelectric conversion element and directs the laser beam through a slit in the mask. By scanning beyond the slit width and subtracting the signal obtained when passing through a part other than the slit width (which becomes a noise signal) from the signal obtained when passing through the slit width (effective signal + noise signal), the corneal , background (noise) from the crystalline lens, etc. is removed.

In another example, background (noise) is removed by moving a mask to measure the amount of light above and below the laser beam and subtracting it from the scattered light from the laser beam.

Using this method, it is possible to remove unnecessary scattered light and reflected light included in the signal from the photoelectric conversion element, as well as noise caused by the dark current of the photoelectric conversion element, increasing resolution and improving measurement accuracy. can be done.

However, in the former case, a laser beam scanning means is required, and in the latter case, a mask moving means is required, which complicates the apparatus and increases cost. Furthermore, the presence of moving parts leads to deterioration in the reproducibility of data obtained from the measuring device, resulting in the problem that good data or highly accurate data cannot be obtained.

Therefore, the present invention has been made to solve these problems, and provides an ophthalmological measuring device that reduces noise due to reflected and scattered light entering the measurement point in a simple manner and improves measurement accuracy. The purpose is to

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention,
In an ophthalmological measurement device that performs ophthalmological measurements by receiving the scattered light of a laser beam irradiated to a predetermined point within the eye via a photoelectric conversion element and processing the signal from the photoelectric conversion element, the light from the laser light source is transferred into the eye. A laser projecting section that focuses the light on a predetermined point, an observation section that observes the state of the laser beam projection, and a light receiving section that guides the scattered light from the intraocular predetermined point to the charging conversion element. an avalancia photodiode array is disposed at a conjugate point of the predetermined intraocular point, the scattered light from the intraocular predetermined point is guided to the avalanche photodiode array, and the output signal is processed to perform ophthalmological measurements. Adopted.

[Function] In this configuration, the avalancia photodiode array is placed at the conjugate point of a predetermined intraocular point within the light receiving section, and the scattered light from the intraocular predetermined point is guided to the avalancia photodiode array. , without scanning the laser beam or moving the mask, the scattered light from the cornea, iris, crystalline lens, etc. is measured as background (noise) through an avalanche photodiode array, and this is used as the background (noise) when the laser beam is irradiated. The measurement accuracy can be further improved by subtracting it from the intensity of scattered light from within the anterior chamber.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

1 and 2 show a schematic configuration of an ophthalmological measuring device according to the present invention. In the figure, the reference numeral 1 indicates a laser projecting section, and the laser projecting section 1 is equipped with helium neon light. A laser light source 4 made of , argon, etc. and a condenser lens 5 are housed. The light from the laser light source 4 is focused through the condensing lens 5 to a point P in the anterior chamber 30a of the eye 30 to be examined.

The laser projector 1 is also provided with a slit light source (not shown), and the light from this light source is focused on the anterior chamber 30a as a slit image through the slit, illuminating the surrounding area. It functions to easily confirm the position of the point image.

A part of the laser scattered light from the measurement point P in the eye chamber 30a is incident on the avalanche photodiode array 15 via the lens 6 of the light receiving section 3, the beam splitter, the lens 14, and the interference filter F. The interference filter F is a narrow band filter that allows only laser light to pass through.
In addition, the avalancia photodiode array 15 has a third
As shown in the figure, it is a photodiode array in which a plurality of avalanche photodiodes APDI to APD6 are arranged in an array, and are arranged at a conjugate position of a condensing point P. This avalancia photodiode APDI~A
The PD 6 generates an output signal according to the amount of incident light, and is placed at a conjugate position of the condensing point P so that about 1/3 of the avalanche photodiode is irradiated with the focused laser beam 4a. be done.

The output from the avalancia photodiode array 15 is connected to the counter 1 via the amplifier 17 and to the control unit 20.
8 and avalancia photodiode APDI
~The intensity of the scattered light detected by the APD 6 is counted as the number of pulses per unit time. This counter 1
The count value of 8, that is, the number of sampling times and the total number of pulses, is stored in a predetermined memory cell set in the memory cell 19 for each unit time. This operation is performed for each avalanche photodiode APDI to APD6 to create a map of the intensity distribution on the memory 19. The controller 20 performs calculations based on the measurement data stored in the memory 19, and the anterior chamber meat protein concentration is measured.

The observation unit 2 is for observing the state of laser beam projection, and includes a lens 6 and a beam splitter 7 (6 and 7).
is observed by the examiner 13 via the lens 8, the prism 9.10, the field stop 11, and the lens 12 (common with the light receiving section 3).

Next, the operation of the device configured as described above will be explained.

In the measurement, first, the laser light source 4 is turned on, and the laser light is focused through the lens 5 on the measurement point P of the anterior chamber 30a. The light scattered at the measurement point P passes through the lens 6,
A part of it is directed toward the examiner 13 by a beam splitter, and includes a lens 8, a prism 9, 10, and a field diaphragm 11.
, is observed by the examiner 13 through the lens 12.

Further, the scattered light from the measurement point P divided by the beam splitter is simultaneously incident on the avalanche photodiode array 5 via the lens 14 and the interference filter F.

This avalancia photodiode APDI~APD6
generate respective output signals depending on the amount of incident light (intensity of scattered light from within the eye). The scattered light intensity detected by the avalanche photodiodes APDI to APD6 is counted by a counter 18 as the number of pulses per unit time. The count value by this counter 18,
That is, the number of sampling times and the total number of pulses are stored in a predetermined memory cell set in the memory 19 for each unit time, and are stored in a predetermined memory cell set in the memory 19 for each unit time.
A map of intensity distribution is created on the memory 19 for each PD6.

As shown in FIG. 1, when a laser beam is irradiated to a measurement point P, scattered light BGI is generated when the laser beam passes through the cornea 30b of the eye 30 to be examined, and scattered light BGI is generated when the laser beam passes through the front surface of the crystalline lens 30c. Scattered light BG2 generated, crystalline lens 30c
Scattered light BG3 is generated when passing through the rear surface, becomes background (noise), is included in the effective component from the measurement point P, and is incident on the avalanche photodiode array 15. Scattered light based on the background (noise) component is incident on the avalancia photodiodes APDI, APD2, APD5, and APD6 shown in FIG. Scattered light consisting of the sum of (noise) is incident.

The signals from the avalanche photodiodes APD3 and APD4 include a signal component corresponding to the anterior chamber meat protein concentration and a noise component due to reflection and scattering, and the average value of the values in the memory 19 due to these components is set as X. The control unit 20 arithmetic unit calculates the avalanche photodiode APD from this value.
1. Subtract the background (average MY of noise components) from the signals from APD2, APD5, and APD6, extract only the effective signal component, and calculate the gray density in the anterior chamber.

In addition, in the case of a simple embodiment, three avalanche photodiodes APD1 to APD1 to APD1 as shown in FIG.
Use PD3. In this case, the subtraction circuit
Since D2-(APD1+APD3)/2 can be directly output, no memory is required, and it is possible to reduce the cost of the device and shorten the measurement time. Reducing the measurement time reduces the effects of eye blinks and visual fixation micromovements, and also reduces the burden on the subject, which contributes to accurate data measurement.

Furthermore, if the ophthalmological measuring device and the subject are not aligned, the output signals from the avalanche photodiodes APDI and APD3 are often not equal, so the avalanche photodiodes APDI
~APD3 is constantly monitored and measurement is performed when APDI and APD3 become approximately equal, thereby making it possible to reduce measurement errors due to misalignment.

In the embodiments described above, the avalanche photodiode array was a one-dimensional array, but it is of course possible to use a two-dimensional array for measurement, and in this case, the measurement accuracy can be further improved. becomes possible.

[Effects of the Invention] As explained above, according to the present invention, an avalanche photodiode array is arranged at the conjugate point of a predetermined intraocular point in the light receiving section, and scattered light from the intraocular predetermined point is transferred to the avalanche photodiode. Since the laser beam is guided to the array, the scattered light from the cornea, iris, crystalline lens, etc. is removed as background (noise) through the fixed avalanche photodiode array without scanning the laser beam or moving the mask. This can be measured and subtracted from the intensity of scattered light from within the anterior chamber where the laser light was irradiated,
It becomes possible to obtain an ophthalmological measuring device that is inexpensive, has few failures, has good measurement accuracy, and has improved data reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a horizontal sectional view showing the configuration of the ophthalmological measuring device of the present invention, and FIG. 2 is a vertical sectional view of the device shown in FIG.
30...APD4 is an explanatory diagram showing the configuration of a Balancia photodiode array. 1... Laser emitter 2... Observer 3... Light receiver 7... Beam splitter 15... Avalancia photodiode array ○°A
PD6 Completed/1/lO Error Figure 3 ○...APD2 Array configuration (2) Figure 4

Claims (1)

[Scope of Claims] 1) An ophthalmological measurement device that receives scattered light of a laser beam irradiated to a predetermined point within the eye via a photoelectric conversion element, processes signals from the photoelectric conversion element, and performs ophthalmological measurements, A laser projector that focuses light from a laser light source on a predetermined point within the eye, an observation section that observes the state of laser light projection, and a light receiver that guides scattered light from the predetermined point within the eye to a photoelectric conversion element. an avalancia photodiode array is arranged at a conjugate point of the intraocular predetermined point in the light receiving section, the scattered light from the intraocular predetermined point is guided to the avalansia photodiode array, and the output signal is processed. An ophthalmological measurement device characterized in that it performs ophthalmological measurement.