JPH0767836A - Ophthalmologic measuring instrument - Google Patents

Abstract

PURPOSE:To exactly execute the measurement irrespective of a background noise caused by other light than a scattered light from a cell in the anterior chamber, in the pohthalmolgic measuring instrument for executing a scan by irradiating the inside of the anterior chamber of an eye to be examined a with a laser light, photodetecting a scattered light from of the inside of the anterior chamber to a photodetector and analyzing a scattered light signal. CONSTITUTION:From time series data of intensity of a scattered light signal, magnitude of a background noise is calculated (S1), and in accordance with its magnitude, a threshold is set (S2). Moreover, a difference value of the time series data of the scattered light signal is derived (S3), and whether this difference value satisfies a prescribed condition or not is decided (S5), and when it is satisfied, whether the intensity of the scattered light signal is higher than a value obtained by adding the threshold to the background noise value or not is decided (S6). As a result, when it is larger, its scattered light signal is recognized to be the scattered light signal from a cell and the number of cells is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ophthalmologic measuring apparatus. The present invention relates to an ophthalmologic measuring device that performs a predetermined ophthalmic measurement by analyzing a signal.

[0002]

2. Description of the Related Art As an apparatus of this type, for example, by irradiating the inside of the anterior chamber of a subject eye with laser light for scanning, and receiving scattered light from the inside of the anterior chamber in a light receiving element and analyzing the scattered light signal. An ophthalmologic measuring device is known in which the cell number density or the like is measured to quantitatively determine the degree of inflammation in the anterior chamber water.

The configuration of such an ophthalmologic measuring apparatus is shown in FIG. In the configuration of FIG. 3, the laser light emitted from the laser light source 1 is magnified and collimated by the lenses 2 and 3, two-dimensionally scanned by the galvano mirrors 4 and 5, and the lens 6 causes the eyeball 14 of the eye to be inspected. It is collected in the anterior chamber.

The scattered light from the protein molecules and cells in the anterior chamber irradiated with the laser light is condensed by the lens 7 and made into a parallel light beam, and then the optical path is divided by the half mirror 8, one of which is the lens 13 Is imaged by the examiner and observed. The other side is imaged by the lens 9 on the light receiving mask 10 for limiting the field of view, and the scattered light passing through the light receiving mask 10 is received by the photomultiplier tube 11 and converted into an electric signal. Further, the electric signal is digitized by a photon counting method or the like, and analyzed by the arithmetic processing unit 12 composed of a microcomputer.

At this time, the galvanometer mirror 4 contributes to horizontal scanning of the laser beam in the anterior chamber, and the galvanometer mirror 5 contributes to vertical scanning. Each galvanometer mirror is controlled by the signals shown in FIG. That is, horizontal scanning is stopped while the laser beam is being scanned vertically for measurement, and horizontal scanning is performed after the measurement associated with one vertical scanning is completed, during which the laser beam is moved in the vertical direction. The position is returned to the initial state. The control beam shown in FIG. 4 causes the laser beam to perform the scanning shown in FIG. FIG. 5 shows a scanning state when observed from the optical axis direction. In FIG. 5, the scan shown by the solid line is at the time of measurement, and the scan shown by the broken line is at the time of returning to the initial state in the vertical direction.

When such laser beam scanning is performed, in the optical system shown in FIG. 3, from the direction perpendicular to the optical axis of the laser beam and parallel to the horizontal scanning direction of the laser beam. By observing and limiting the visual field in the optical axis direction by the light-receiving mask, it is possible to define a three-dimensional measurement range.

Now, when the measurement range of the optical system shown in FIG. 3 is set in the anterior chamber of the eyeball, the protein molecules and cells in the anterior chamber are irradiated with laser light and emit scattered light. When this scattered light is received by the optical system shown in FIG. 3, the time series data of the scattered light intensity shown in FIG. 6 is obtained. Here, the scattered light from a cell having a diameter much larger than that of a protein molecule such as albumin or globulin is generated as a spike-like scattered light as shown in FIG. 6 when the laser beam is spatially scanned. To be detected. Therefore, the number of cells can be obtained by analyzing this spike-shaped signal.

Conventionally, in order to analyze the spike-like signal detected in this way, as shown in FIG. 7, the difference value of the time series data of the scattered light intensity is obtained, and the difference value is predetermined. Only signals that were judged to be greater than or equal to the difference value were regarded as scattered light signals from cells.

Here, a method of recognizing a scattered light signal from cells by the difference method will be specifically described. Now, the scattered light intensity at time k is defined as I (k), and the difference value J (k) is defined as J (k) = I (k + m) -I (k). Here, m is a value determined from the characteristics of the scattered light signal from the cell and is a positive number. This difference value J
Only when (k) satisfied a predetermined condition, the signal was recognized as a signal from a cell.

The measurement accuracy of this measurement method and analysis method depends on the measurement volume. The measurement volume depends on the vertical and horizontal scanning distances of the laser light and the visual field area of the light-receiving mask. Therefore, in order to improve the measurement accuracy, it is necessary to increase the measurement volume, and for that purpose, it is necessary to expand the scanning range of the laser light and the view area of the light receiving mask.

[0011]

However, if the aperture area of the light-receiving mask for limiting the field of view is enlarged in order to expand the measurement volume, it becomes easy to receive reflected light or scattered light from the fundus or cornea irradiated with laser light. The background noise due to light other than the scattered light from the cells in the anterior chamber becomes large. When the photon counting method is used for photoelectric conversion using a photomultiplier tube, the output value fluctuates according to the Poisson distribution even if it receives light of constant intensity, so the magnitude of the fluctuation is , Proportional to the square root of the average output value.

Therefore, by increasing the opening area of the light-receiving mask, it becomes easier to receive the background light due to the reflection on the fundus and cornea. As a result, when the background noise increases, the fluctuation due to the photon counting method also increases. . Therefore, in the analysis method by the difference method described above, the probability that the increased fluctuation is mistakenly recognized as a signal from the cell increases, and the measurement accuracy deteriorates.
The measurement volume for measuring the degree of inflammation could not be increased beyond a certain level.

Further, in the time-series data of scattered light obtained by the above-mentioned measuring method, for example, when the protein concentration is measured, the signal from the cell becomes noise, and when the number of cells is large, the reliability of the measured value becomes high. Was missing.

Therefore, an object of the present invention is to provide an ophthalmologic measuring apparatus of this type, which is capable of performing accurate measurement regardless of the magnitude of the background noise and the number of cells in the anterior chamber. .

[0015]

In order to solve the above problems, according to the present invention, laser light is irradiated into the anterior chamber of the eye to be scanned, and scattered light from the anterior chamber is received by a light receiving element. In an ophthalmologic measuring device that performs a predetermined ophthalmic measurement by receiving and analyzing a scattered light signal, the intensity of the scattered light signal is a predetermined value of background noise due to light other than scattered light from cells in the anterior chamber. A configuration having an arithmetic processing unit that determines whether or not the scattered light signal is a scattered light signal from cells in the anterior chamber depending on whether or not the scattered light signal is larger than a value obtained by adding a threshold value is adopted.

[0016]

According to such a configuration, the influence of the fluctuation of the background noise can be eliminated by the judgment based on the background noise value and the threshold value, and the scattered light signal from the cell can be accurately judged without being erroneously recognized. .

[0017]

Embodiments of the present invention will be described below with reference to the drawings. The ophthalmologic measuring apparatus of the embodiment has the configuration shown in FIG. 3 described above, and the method of analyzing the optical signal in the arithmetic processing unit 12 including a microcomputer is different from the conventional method. The method of the analysis process will be described with reference to FIGS.

In FIG. 1 (a), when the cells are not suspended in the anterior chamber of the eye to be examined, the laser beam is scanned once in the anterior chamber by the optical system of the apparatus of FIG. The photon count values relating to the scattered light intensity obtained at times are shown in time series. The method until the time series data is obtained is the same as the conventional method.

In the case of FIG. 1 (a), since the cells are not suspended in the anterior chamber, scattered light from the cells is not received. Therefore, the light shown in FIG. 1 (a) is not received. The signal represents the intensity of light reflected from eye tissues such as the cornea, lens, and fundus of the eye, and scattered light from protein molecules in the anterior chamber, and serves as background noise in extracting the signal from cells.

Here, as described above, when the photon counting method is used as a method for converting an optical signal into an electric signal, the observed photon counting value per unit time indicates that light of a constant intensity is received. Also fluctuates around the average value representing the constant intensity. Since the time-series data obtained by the measurement follows the Poisson distribution, the standard deviation is equal to the square root of the mean value. Therefore, the larger the average value regarding the strength, the larger the magnitude of the fluctuation. In this case, when trying to recognize a signal from a cell using the difference method as described in the conventional technique, the fluctuation of reflected light and scattered light from the eye tissue such as the fundus and the lens is mistakenly recognized as a signal from the cell. There is a possibility that it will end up.

In order to avoid this misidentification, FIG.
As shown in (a) and (b), a threshold value T larger than the magnitude of the fluctuation is set, the obtained signal becomes larger than the set threshold value T, and the difference method described in the prior art is used. A method of recognizing that a signal satisfying the condition is a signal from a cell is effective.

FIG. 2 shows a flow chart of the analysis processing of the arithmetic processing unit 12 which executes the analysis by such a method.

As shown in FIG. 2, in the analysis processing of the arithmetic processing unit 12, first, every time the difference data obtained from the time series data of the photon count value of the optical signal changes from a negative value to a positive value, The photon count value of the time series data corresponding to the address is stored, and the average value of all the values is calculated as the background noise B (step S
1).

Next, the fluctuation of this background noise B is

[0025]

[Equation 1]

Since it is a degree, it is a value that is sufficiently larger than this fluctuation.

[0027]

[Equation 2]

The threshold value T is variably set (step S2). When the signal strength distribution is approximated as a Gaussian distribution,

[0029]

[Equation 3]

The probability that a large fluctuation will appear as it exceeds 1.06% is 0.006% or less. This is no more than one in the total number of data used in this device. Therefore, as the threshold T

[0031]

[Equation 4]

It is sufficient to adopt

Next, the difference data J of the above-mentioned optical signal.
(K) is calculated (step S3).

Next, it is determined whether the ordinal number k of the sampling times of the data to be processed exceeds the total number N of data, that is, whether or not the processing of all data has been completed (step S
4) As a condition for recognizing that it is the data of the scattered light signal from the cell if not completed, (1) Difference data J
Does the value of (k) continuously take a positive value by a certain number or more, and (2) satisfies the condition that the added value of the difference data between them has a certain value or more? It is determined whether or not (step S5).

If the above condition is not satisfied, the ordinal number k is incremented (step S8), and the next difference data is judged (steps S4 and S5). It is determined whether the intensity I (k) is larger than the background noise B + the threshold T (step S6).

If it is not larger, the ordinal number k is incremented again (step S8) and the next difference data is judged (steps S4 and S5). If it is larger, the signal of the data is recognized as a signal from the cell. , The number of cells is incremented (step S7), the ordinal number k is incremented again (step S8), and the next data is processed (steps S4 to S7). When the analysis of all data is completed in this way, the process is completed. The cell number density in the anterior chamber can be measured from the number of cells counted as described above.

According to the above-described analysis processing, not only the judgment based on the difference value for the optical signal but also the judgment based on the background noise B + threshold value T is performed to eliminate the influence of the fluctuation of the background noise, Erroneous recognition of signals from cells due to the fluctuation disappears.

As described above, the fluctuation increases as the background noise increases. Therefore, the threshold value T is variably set according to the size of the background noise, but the background noise increases.
When the threshold value T increases, a counting phenomenon occurs in which the original signal from the cell cannot be recognized. Therefore, the measurement limit is determined by the balance between the counting frequency and the measurement accuracy.

In the configuration of the apparatus shown in FIG. 3, the arithmetic processing unit 12 analyzes the time-series data of the scattered light intensity by the scattered light signal from the photomultiplier tube 11 to determine the number of cells in the anterior chamber. Although ophthalmological measurements other than the cell number density can be performed by counting, the measurement can be accurately performed using the above-described analysis processing. For example, when measuring the protein concentration in the anterior chamber, even if the number of cells in the anterior chamber is large, the scattered light signal from the cells is obtained from the time-series data of the scattered light intensity obtained in the arithmetic processing unit 12 by the method described above. By making a determination, removing the component from the time-series data, and analyzing the remaining component again, it is possible to accurately remove the component of the signal from unnecessary cells and to accurately measure the protein concentration.

[0040]

As is apparent from the above description, according to the present invention, the anterior chamber of the eye to be examined is irradiated with laser light for scanning, and the scattered light from the anterior chamber is received by the light receiving element. In an ophthalmologic measuring device that performs a predetermined ophthalmologic measurement by analyzing a scattered light signal, the intensity of the scattered light signal is a predetermined threshold value added to the value of background noise due to light other than scattered light from cells in the anterior chamber. Since the configuration has an arithmetic processing unit that determines whether or not the scattered light signal is a scattered light signal from cells in the anterior chamber depending on whether or not the value is larger than the above value, the influence of fluctuation of background noise is eliminated. However, the scattered light signal from the cells can be accurately determined without being erroneously recognized, and the ophthalmologic measurement related to the cells in the anterior chamber such as the cell number density can be accurately performed. In particular, by setting the threshold variably according to the magnitude of the background noise, it is possible to accurately perform the measurement regardless of the magnitude of the background noise.

Further, the background noise value and the threshold value are used for the determination, the difference value of the time-series data of the scattered light signal is determined, and it is determined whether or not the difference value satisfies a predetermined condition. By recognizing only the signal satisfying both the background noise value and the determination by the threshold value as the signal from the cell, the measurement can be performed more accurately.

In addition, ophthalmological measurements relating to cells other than the above cells,
For example, when measuring the protein concentration, etc., remove the components determined to be the signals of scattered light from cells from the time series data of the intensity of scattered light signals, and analyze the remaining components again The scattered light component of can be removed and accurate measurement can be performed.

[Brief description of drawings]

FIG. 1 is a signal waveform diagram showing a waveform of a scattered light signal when a scattered light from a cell in an anterior chamber of an eye to be examined is not received and when the scattered light signal is received in the ophthalmologic measuring apparatus according to the embodiment of the present invention. .

FIG. 2 is a flow chart of analysis processing of a scattered light signal in an arithmetic processing unit of the apparatus of the embodiment.

FIG. 3 is an explanatory diagram showing a configuration of an ophthalmologic measuring apparatus common to the embodiment and a conventional example.

FIG. 4 is a signal waveform diagram showing a control signal of a galvanometer mirror that scans a laser beam in the same apparatus.

FIG. 5 is an explanatory diagram showing a scanning state of the laser beam.

FIG. 6 is a signal waveform diagram of time-series data of scattered light intensity observed when a laser beam is scanned in the anterior chamber of the eye to be inspected by the ophthalmologic apparatus.

FIG. 7 is a graph showing difference data of time series data of the same scattered light intensity.

[Explanation of symbols]

 1 laser light source 2, 3, 6, 7, 9, 13 lens 4,5 galvanometer mirror 8 half mirror 10 light receiving mask 11 photomultiplier tube 12 arithmetic processing unit

Claims (5)

[Claims] 1. An ophthalmology in which a predetermined ophthalmologic measurement is performed by irradiating the inside of the anterior chamber of a subject eye with laser light for scanning, receiving scattered light from the inside of the anterior chamber by a light receiving element, and analyzing the scattered light signal. In the measuring device, whether or not the intensity of the scattered light signal is larger than a value obtained by adding a predetermined threshold to the value of background noise due to light other than scattered light from cells in the anterior chamber, the scattered light signal is An ophthalmologic measuring apparatus comprising arithmetic processing means for determining whether or not a scattered light signal from cells in a tuft. 2. The ophthalmologic measuring apparatus according to claim 1, wherein the arithmetic processing unit variably sets the threshold according to the magnitude of the background noise. 3. The arithmetic processing means makes a determination based on the background noise value and a threshold value, obtains a difference value of time-series data of the intensity of the scattered light signal, and determines whether the difference value satisfies a predetermined condition. The ophthalmologic measuring apparatus according to claim 1 or 2, wherein it is determined whether or not, and only a signal that satisfies both the determination and the determination based on the background noise value and the threshold is recognized as a signal from the cell. . 4. The arithmetic processing unit removes a component determined to be a scattered light signal from the cell from the time series data of the intensity of the scattered light signal, analyzes the remaining components again, and performs a predetermined ophthalmic measurement. The ophthalmologic measuring apparatus according to any one of claims 1 to 3, which is performed. 5. The arithmetic processing means counts the signals determined as scattered light signals from the cells in the anterior chamber to measure the cell number density in the anterior chamber. The ophthalmic measurement device according to any one of items 1 to 7.