JP2020195886A - Tear film thickness measurement apparatus and method - Google Patents

Abstract

To provide a tear film thickness measurement apparatus and method that are configured to irradiate a tear film of a subject's eye with light while varying a wavelength of a wide-band light source to measure the thickness of the tear film.SOLUTION: A wide-band wavelength sweeping light source 31 selectively emits, to an image collection unit 30, light having a specific wavelength in a wavelength range, for example, from a visible wavelength to a near-infrared wavelength includes. A half mirror 32 irradiates a cornea with light. A light flux with which the cornea is irradiated has a light flux diameter covering a measurement range. A black-and-white camera 34 images reflected light from a tear film on the cornea after penetrating the half mirror 32. The image collection unit 30 includes a control processing unit 35 that varies a wavelength of the wide-band wavelength sweeping light source 31 to obtain a spectral reflection distribution at each pixel of the black-and-white camera 34. By using the spectral reflection distribution, a distribution information acquisition unit 44 can measure the thickness of the tear film.SELECTED DRAWING: Figure 2

Description

The present invention relates to a tear film thickness measuring device and method.

For example, Patent Document 1 states, "In a system and method for performing tear layer structure measurement and evaporation rate measurement, a broadband light source illuminates the tear layer, and a spectrometer is at least one point of the tear layer. Each spectrum of reflected light from is measured. ”(See summary).
Further, Patent Document 1 states, "In the processing unit coupled to the camera and the spectrometer, the color obtained by the camera at at least one point measured by the spectrometer matches the color of the spectrometer at the same point. As such, the color of each point of the calibrated camera determines the thickness of the lipid at each point. ”(See summary).
Further, Patent Document 2 describes an ophthalmologic examination device for improving the reliability of dry eye type evaluation (paragraph 0004), and Patent Document 3 describes "accuracy and accuracy of tear examination". An ophthalmologic examination apparatus for "improving" (paragraph 0005) is described.

International Publication No. 2015-132788 Japanese Patent Application No. 2016-185076 Japanese Patent Application No. 2016-185077

However, in the prior art, it is not described to change the wavelength and measure the thickness of the tear film.
In view of the above points, it is an object of the present invention to provide a tear film thickness measuring device and method for measuring the thickness of the tear film by irradiating the tear film of the eye to be inspected by changing the wavelength of the broadband light source. And.

According to the first solution of the present invention
It is a tear layer thickness measuring device.
A light source unit, a reflected signal collecting unit having a light receiving element and receiving reflected light from the anterior segment of the eye to be inspected, and a reflected signal collecting unit.
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
Display control unit and
Front image acquisition unit, which acquires the front image of the cornea,
With
The light source unit has a wide wavelength range and irradiates the cornea with light having a predetermined wavelength pattern.
The display control unit includes a distribution image of the thickness of the tear liquid acquired by the tear layer thickness information acquisition unit and a front image acquired by the front image acquisition unit by the reflected light from the received tear layer. Display the composite image of
A tear film thickness measuring device is provided.

According to the second solution of the present invention
It is a method for measuring the thickness of the tear film in the tear film thickness measuring device.
The tear film thickness measuring device.
A light source unit, a reflected signal collecting unit having a light receiving element and receiving reflected light from the anterior segment of the eye to be inspected, and a reflected signal collecting unit.
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
Display control unit and
Front image acquisition unit, which acquires the front image of the cornea,
With
The light source unit has a wide wavelength range and irradiates the cornea with light having a predetermined wavelength pattern.
The display control unit includes a distribution image of the thickness of the tear liquid acquired by the tear layer thickness information acquisition unit and a front image acquired by the front image acquisition unit by the reflected light from the received tear layer. Display the composite image of
A method for measuring the thickness of the tear film is provided.

According to the present invention, it is possible to provide a tear film thickness measuring device and a method for measuring the thickness of the tear film by irradiating the tear film of the eye to be inspected by changing the wavelength of the broadband light source.

The schematic which shows the structure of the ophthalmologic examination apparatus. The schematic diagram for demonstrating the structure of the image acquisition part. A flowchart showing the operation of the ophthalmologic examination device. A flowchart showing an operation for creating tear thickness distribution information.

An exemplary embodiment of the present invention will be described with reference to the drawings. In addition, the description contents of the document cited in this specification and other known techniques can be incorporated into the embodiment. (See, for example, Patent Document 2 and Patent Document 3).

The ophthalmologic examination device (tear layer thickness measuring device) of the embodiment measures the thickness of the tear layer on the cornea of the eye to be inspected.

The ophthalmologic examination apparatus of the present embodiment can measure the thickness of the tear film, which is a thin film on the cornea, by irradiating the cornea with the measurement light and obtaining the reflected light. The ophthalmologic examination apparatus of the present embodiment collects one or more images showing tears on the cornea by photographing the anterior segment of the eye to be inspected. Further, the image may be collected by scanning in one dimension or two dimensions. You may also collect time series images.
The time-series image includes a group of images acquired at different times, and typically, a group of frames obtained by shooting a moving image at a predetermined frame rate, or a group of images obtained by repeatedly photographing the anterior segment at a predetermined time interval. It may be the obtained still image group. The time-series image is an image acquired by an arbitrary modality, and may be typically a group of front images or a group of OCT images.
Hereinafter, a time-series image will be mainly described as an example, but the present invention and / or the present embodiment can be applied to one or more images as described above in addition to the time-series image.

The front image may be an image showing an interference pattern due to front reflection and back reflection of a tear film layer (for example, an oil layer).

The ophthalmologic examination apparatus of the embodiment may include a function of photographing the eye to be inspected (a function of collecting (time series) images). In addition to or in place of this function, the ophthalmologic examination apparatus of the embodiment includes a function of acquiring (time series) images from another device, a recording medium, or the like (a function of accepting (time series) images). You may be.

(Image collection department)

The function of accepting (time series) images is, for example, from other devices (image archiving system, slit lamp microscope, OCT device, etc.) via a communication line such as a local area network (LAN), the Internet, or a dedicated line (time). (Series) This is realized by a communication device for receiving images, a data reader for reading data from a recording medium, and the like (image reception unit).

The processing functions (calculation function, data processing function, image processing function, control function, etc.) in the ophthalmic examination device of the embodiment include hardware such as a processor and a storage device, and a calculation program, an image processing program, a control program, and the like. It is realized by collaborating with software. A part of the hardware may be provided in an external device capable of communicating with the ophthalmologic examination device. Also, at least a portion of the software may be pre-stored in an ophthalmologic examination device and / or may be pre-stored in an external device.

<First Embodiment>
<Constitution>
An exemplary embodiment of an ophthalmic examination device will be described. In this embodiment, an ophthalmologic examination apparatus provided with a function (image collecting unit) for collecting (time series) images will be described.

An example of the configuration of the ophthalmic examination apparatus of this embodiment is shown in FIG. The ophthalmologic examination apparatus 1 collects (time-series) images by repeatedly photographing the eye to be inspected, analyzes each of the plurality of images included in the (time-series) images, and identifies the tear fluid destruction region.

The ophthalmologic examination apparatus 1 can display a (time series) image and information obtained from the image on the display device 2. (Time series) An example of information obtained from an image is a tear thickness distribution (thickness map). The display device 2 may be a part of the ophthalmologic examination device 1 or may be an external device connected to the ophthalmologic examination device 1.

The ophthalmologic examination device 1 includes a control unit 10, a storage unit 20, an image collection unit 30, a data processing unit 40, and an operation unit 50.

<Control unit 10>
The control unit 10 controls each unit of the ophthalmologic examination device 1. The control unit 10 includes a processor. The "processor" includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (for example, a SPLD (Simple Program Program)). , FPGA (Field Programmable Gate Array)) and the like. The control unit 10 can realize the function according to the embodiment by reading and executing a program stored in a storage circuit or a storage device (storage unit 20, an external device, etc.), for example.

Further, the control unit 10 may include a communication device for transmitting / receiving data via a communication line such as a LAN, the Internet, or a dedicated line.

<Display control unit 11>
The control unit 10 includes a display control unit 11. The display control unit 11 executes control for displaying information on the display device 2. The display control unit 11 can perform processing (generation, processing, composition, etc.) related to the information displayed on the display device 2. The process may be executed by linking the display control unit 11 with other elements (other elements of the control unit 10, data processing unit 40, etc.).

<Memory unit 20>
Various information is stored in the storage unit 20.

<Image collection unit 30 (reflection signal collection unit)>
The image collecting unit 30 collects one or more images representing tears on the cornea by photographing the anterior segment of the eye to be inspected. Further, the image may be collected by scanning in one dimension or two dimensions. You may also collect time series images. The image collecting unit 30 can collect (time-series) images showing the dynamics of tears on the cornea by repeatedly photographing the eye to be inspected.

FIG. 2 shows a configuration diagram of the image collecting unit 30. The image collecting unit 30 includes an optical system, a driving system, a control system, and a processing system for executing shooting. For example, the image acquisition unit 30 includes a wideband wavelength sweep light source 31, a half mirror 32, a platid ring 33, a camera 34, a control processing unit 35, a lens, and the like.
The wideband wavelength sweep light source 31 may have wavelength selectivity by combining, for example, a white light source containing near-infrared radiation with a spectroscope such as a grating or an LVF (Linear Variable Filter). Examples of the white light source include a halogen lamp, a xenon lamp, and a supercontinuum light source. A light source driver (not shown) can be built into the wideband wavelength sweep light source 31 or can be externally attached.
The control processing unit 35 controls the wideband wavelength sweep light source 31 and the platid ring 33, detects a signal from the camera 34, and collects an image.
The image collecting unit 30 selectively emits light having a specific wavelength in the visible to near-infrared wavelength range, for example, from the wideband wavelength sweep light source 31. The cornea is irradiated with light by the half mirror 32. The luminous flux applied to the cornea has a luminous flux diameter that covers the measurement range.

The reflected light from the tear film on the cornea passes through the half mirror 32 and is imaged by the camera 34. The image collecting unit 30 obtains a spectral reflection distribution in each pixel of the camera 34 by changing the wavelength of the broadband wavelength sweeping light source 31 by the control processing unit 35, thereby obtaining distribution information acquisition unit (tear layer thickness information acquisition). Part) 44 can measure the thickness of the tear film.
The image collecting unit 30 arranges a placido (kerato) ring 33 at a position facing the eye to be inspected, captures a ring image projected on the cornea of the eye to be inspected with a camera 34, measures the shape (curvature) of the cornea, and acquires distribution information. In 44, it is also possible to correct the measurement result of the tear film thickness from the amount of deviation from the obtained reference value of corneal curvature (for example, R7.7).
An appropriate optical system may be used instead of the half mirror.
In addition, the camera 34 can use an appropriate two-dimensional detection device such as a two-dimensional CCD image sensor or another form of (two-dimensional) image sensor, for example, a two-dimensional CMOS (Complementary Metal Oxide Sensor) image sensor. Is.

The broadband wavelength sweep type light source 31 includes at least continuous or discrete wavelengths in the visible light region to the near infrared region, and can selectively irradiate the eye to be inspected with light of individual wavelengths. Alternatively, light from a white light source such as an incandescent lamp, a xenon lamp, or a supercontunium light source can be used as substantially monochromatic light of individual wavelengths by using a spectrometer or a color filter. It is assumed that the camera 34 has sufficient sensitivity in each wavelength in the measurement wavelength range (visible to near infrared), and the characteristic of sensitivity (spectral sensitivity) for each wavelength is known. The spectral sensitivity of the camera 34 may be known by calibration or the like. The cornea of the eye to be inspected and the light receiving portion of the camera 34 are optically coupled to each other, and an image of the cornea is formed on the light receiving portion of the camera 34.

The luminous flux measured from the wideband wavelength sweep type light source 31 is reflected by the half mirror 32 toward the eye to be inspected through the lens system, and irradiates the opera to be inspected through the objective lens 33. The measured light beam reflected by the cornea to be inspected passes through the objective lens 33 and the half mirror 32 and forms a corneal image on the sensor of the camera 34. The optical system from the light source 31 to the camera 34 is housed in a housing, the corneal apex of the eye to be inspected coincides with the optical axis connecting the objective lens 33 to the camera 34 (X, Y directions), and the objective lens 33 to the corneal apex. Align to keep the value constant (Z direction). A known method is used as a method for detecting the alignment state. When the alignment states of X, Y and Z are within the permissible range, the alignment is completed and the control processing unit 35 issues a trigger signal to start measurement. (Auto start)
Alternatively, the measurement may be started by a trigger such as pressing the measurement switch by the operator. (Manual start)
Alternatively, the blink may be monitored by the camera 34 and the measurement may be started using this as a trigger.

When the measurement is started, the wideband wavelength sweep type light source 31 irradiates the cornea to be inspected with a specific substantially single wavelength (narrow wavelength range), and the reflected image is imaged by the camera 34. Sweep (change) wavelengths to acquire images at each wavelength. The reflectance distribution for each wavelength of the cornea is obtained by multiplying the luminance value of at least the pixels on the optical axis of each image acquired at each wavelength by the spectral sensitivity of a known camera at each wavelength. By performing spectral analysis on the obtained spectral distribution, it is possible to determine the thickness of each of the fat layer, the aqueous layer, and the mucin layer of tears. By performing the same processing for each pixel for a part other than the apex of the cornea, the tear film thickness can be obtained from the spectral distribution of the pixels corresponding to each part, and the distribution of the tear thickness can be obtained. Since images at each wavelength in visible light are recorded, it is possible to reproduce a color image of the cornea (an image when the corneum is observed with a color camera) by superimposing the images at each wavelength at a predetermined ratio. It will be possible. When observing the time-series change of the tear film continuously, the first measurement (any one measurement) is performed by the above method, the thickness (absolute value) of each tear film is obtained, and the subsequent measurements are for the first measurement. You just need to get a relative change. In this case, the change in color (interference color) at each site on the cornea with respect to the first time may be observed.

Here, since the observation camera 34 is a so-called black-and-white camera, it is not possible to directly observe the "color" on the cornea, but the wavelengths of the light sources are R (near 600 nm), G (near 500 nm), and B (near 400 nm). A color image can be obtained by superimposing the corneal images taken by changing to three wavelengths, and by acquiring and comparing the color images in time series, the relative change over time of the tear film can be known. be able to. Since the tear film thickness (absolute value) is obtained in the first measurement, the tear film thickness (absolute value) at each time can be obtained by comparing with this. It is possible to carry out the first measurement every time, but it takes time for one measurement because it is necessary to acquire the reflectance spectral distribution over a wide wavelength range. On the other hand, for the second and subsequent measurements, only three images (RGB) need to be acquired for each measurement, so the measurement time can be significantly shortened and the tear film thickness changes at short time intervals. Can be measured. R image, G image, B image are continuously acquired at equal intervals (R, G, B, R, G, B, R, G, B ...) and the obtained color image and the previous two images are combined. If a color image is obtained, it is not necessary to acquire three new images each time, and the measurement interval can be shortened.

The thickness distribution of the tear film can be shown by measuring the thickness of the tear film at each site on the obtained cornea, creating a pseudo-color thickness map in which the thickness is converted into color, and displaying it on the screen. .. By displaying the thickness map at each time side by side on the screen, it is possible to confirm the change over time. By switching the image for each hour to the same part on the screen and displaying it, it can be presented as a pseudo moving image. The portion less than the specified thickness may be emphasized and displayed, or the area of the portion may be obtained and displayed.
With this configuration, it is not necessary to arrange a dedicated spectrometer on the light receiving side, and the configuration is simplified. Further, since the half mirror that divides the optical path between the camera and the spectrometer is not required, the reflected light flux of the cornea can be efficiently received by the camera. Therefore, the luminous flux itself irradiating the cornea can be suppressed low, and the burden on the patient can be reduced.

(Corneal curvature error correction)
Since the cornea is a substantially spherical surface, it is necessary to consider the curvature of the cornea when measuring the thickness of the lacrimal layer in the peripheral area. It is basically configured as an average corneal radius of curvature (eg r7.7 mm). However, in reality, there are individual differences in the radius of curvature of the cornea, and it is distributed in the range of about r6 mm to 9 mm, and the actual cornea has an aspherical shape in which the radius of curvature becomes larger (loose) from the center to the periphery. Is. Furthermore, it may deviate from the spherical surface such as corneal astigmatism and keratoconus. When the analysis is performed as a spherical surface having a uniform radius of curvature for these, the detected tear layer thickness includes an error. Here, it is desirable to measure the shape of the cornea and correct the tear layer thickness measurement result.

(Platide method)
Around the objective lens, a plated plate having a plurality of concentric light-transmitting portions is arranged on a light-shielding plate. The platinum plate 33 is illuminated by a light source (near infrared LED or the like) arranged on the back surface (the surface opposite to the eye to be inspected), and becomes a concentric light source to illuminate the cornea to be inspected. The luminous flux reflected by the cornea produces a multiple ring-shaped virtual image due to the curvature of the cornea. The image of the virtual image is imaged by the camera 34, and the distribution of the corneal shape is obtained by a known method from the change in the size and shape of each ring image. By correcting the obtained corneal shape with respect to the tear film thickness data, a highly accurate tear film thickness can be obtained.

(OCT method)
The device has an anterior segment OCT device capable of acquiring an anterior segment tomographic layer (not shown). The OCT measurement light scans the anterior segment of the eye with a scanner through the objective lens. Scan methods include radiation scan and raster scan. A cross-sectional image of the anterior segment of the eye (including at least the surface of the cornea) is acquired, and the corneal shape is obtained by analyzing the cross-sectional image, and correction is performed in the same manner as in the Platide method.

In addition, the modality for collecting (time series) images may be arbitrary and may include a front image collecting unit.
The front image collecting unit is configured to acquire a front image of the anterior segment of the eye (cornea, etc.), and collects (time series) images composed of a series of front images (front image group). The front image collecting unit has, for example, the same configuration as a conventional digital slit lamp microscope.

<Data processing unit 40>
The data processing unit 40 performs various data processing. For example, the data processing unit 40 performs image processing and image analysis. The data processing unit 40 includes a distribution information acquisition unit 44.

<Distribution information acquisition unit 44>
The distribution information acquisition unit 44 acquires the distribution information of the thickness of the tear fluid by analyzing each of the plurality of images included in the (time series) image.

The distribution information acquisition unit 44 inputs the collected image from the image collection unit 30, and acquires the tear thickness distribution information based on the image.

The distribution information acquisition unit 44 obtains the thickness of the tear film at each measurement point based on the specified oil layer region and (at least one of) the liquid layer region. The thickness of the tear film may be, for example, any one of the thickness of the oil layer region, the thickness of the liquid layer region, and the thickness of the entire tear fluid. Here, the thickness of the liquid layer region may be the thickness of the liquid layer containing the mucin layer or the thickness of the liquid layer not containing the mucin layer. In the latter case, the thickness of the mucin layer can also be determined.
Alternatively, the thickness of the drug solution layer after instillation of artificial tears or drug solution may be determined.

By such treatment, for example, the distance between the front surface of the oil layer (the boundary between the oil layer and the air) and the back surface (the boundary between the oil layer and the liquid layer) and the front surface of the liquid layer (the boundary between the oil layer and the liquid layer) The distance between the surface and the back surface (the boundary between the liquid layer and the corneum) and the distance between the front surface of the oil layer and the back surface of the liquid layer are calculated.

The distribution information acquisition unit 44 can also specify the tear fluid destruction region based on the acquired tear fluid thickness distribution information. The fracture region is, for example, one of the region where the oil layer is destroyed (the region where the oil layer region is not detected) and the region where the liquid layer is destroyed (the region where the liquid layer region is not detected), or a combination of these regions. .. Neither the oil layer region nor the liquid layer region is detected in the region where the entire tear fluid is destroyed.

In a typical example, the distribution information acquisition unit 44 can specify a portion where the thickness of the oil layer region is equal to or less than a predetermined threshold value as a region where the oil layer is destroyed. Further, the distribution information acquisition unit 44 can specify a portion where the thickness of the liquid layer region is equal to or less than a predetermined threshold value as a region where the liquid layer is destroyed. Further, the distribution information acquisition unit 44 can specify a portion where the thickness of the tear fluid region (composite region of the oil layer region and the liquid layer region) is equal to or less than a predetermined threshold value as a region where the entire tear fluid layer is destroyed.

<Operation unit 50>
The operation unit 50 is used for the user to input an instruction to the ophthalmologic examination device 1. The operation unit 50 may include a known operation device used in an ophthalmic apparatus or a computer. For example, the operation unit 50 may include a mouse, a touch pad, a trackball, a keyboard, a pen tablet, an operation panel, a joystick, a button, a switch, and the like. Further, the operation unit 50 may include a touch panel. In this case, the control unit 10 can display the GUI for operating the ophthalmologic examination device 1 on the touch panel.

<Front image acquisition unit 60>
The front image acquisition unit 60 acquires a front image of the anterior segment of the eye (cornea, etc.). The process for acquiring the front image is optional. In the first example, the front image acquisition unit 60 may include a configuration for photographing the anterior eye portion.

<motion>
FIG. 3 shows a flowchart showing the operation of the ophthalmologic examination apparatus.
Some examples of actions that an exemplary ophthalmic examination device can perform will be described. The flow of processing executed in this example is shown in FIG. It is assumed that preparatory processing such as input of the patient ID and the like, alignment of the optical system with respect to the eye to be inspected, and setting of focus adjustment of the optical system has already been performed.

(S3: Create tear thickness distribution information)
(For details, refer to FIG. 4 and its explanation).
First, the image collecting unit 30 collects (time-series) images showing the dynamics of tears on the cornea by repeatedly photographing the eye to be inspected, as described in the above-mentioned "(Image collecting unit 30)" and the like. To do. Typically, at least one of fluorescence contrast imaging and interference imaging can be performed.
By photographing the anterior segment of the eye to be inspected, one or a plurality of images showing tears on the cornea are collected. Further, the image may be collected by scanning in one dimension or two dimensions.

The display control unit 11 can display the collected image on the display device 2. The displayed image is an image obtained by applying a desired rendering to a three-dimensional image, and may be, for example, a front image such as a projection image or a shadow gram, or a tomographic image such as a B scan image. It may be a pseudo three-dimensional image such as a volume rendered image.

When time-series images are collected, one or more three-dimensional images included in the time-series images can be rendered, and one or more rendered images obtained thereby can be displayed on the display device 2. When displaying a plurality of rendered images, it is possible to arrange them in chronological order. It is also possible to switch and display a plurality of rendered images in chronological order.

Further, when the time series image is collected, the blinking image can be specified from the series of three-dimensional images constituting the time series image. Further, the last blink image or the next image in the series of blink images can be set as the image at the start of eyelid opening (the above-mentioned reference image).

The distribution information acquisition unit 44 creates tear thickness distribution information based on the collected images.

When the time-series images are collected, the distribution information acquisition unit 44 creates tear thickness distribution information from the segmentation results for each of the plurality of images included in the time-series images. As a result, a plurality of tear thickness distribution information corresponding to the plurality of images included in the time series image can be obtained. The plurality of tear thickness distribution information represents the time course of the tear thickness distribution, that is, the dynamics of the tear fluid.

(S4: Acquire a front image of the anterior segment of the eye)
Next, the front image acquisition unit 60 of the anterior segment of the eye, for example, by photographing the anterior segment of the eye, accessing an electronic medical record system or the like, or rendering the image collected in step S3. Get the front image.

The timing of acquiring the front image may be arbitrary. For example, the front image of the anterior segment can be acquired by accessing the electronic medical record system or the like or by photographing the anterior segment before or after step S3. Alternatively, the front image of the anterior segment can be acquired by rendering the image collected in step S3 at an arbitrary timing after step S3.

(S5: Display a composite image of the tear thickness distribution image and the front image)
Subsequently, the display control unit 11 (and the data processing unit 40) forms an image (tear thickness distribution image) based on the tear solution thickness distribution information created in step S3, and the tear solution thickness distribution image and the step. The front image acquired in S4 is combined and displayed on the display device 2. The tear thickness distribution image is, for example, a pseudo color map in which the thickness value of each point represented by the tear thickness distribution information is expressed in pseudo color.

In one example, the composite display of the tear thickness distribution image and the front image includes image processing for synthesizing the tear thickness distribution image and the front image, and control for displaying the composite image formed by the image processing. In another example, the composite display includes a control for displaying the tear thickness distribution image and the front image in an overlapping manner by using a layer display function or the like. A display image obtained by superimposing two (or more) images under display control in this way is also an example of a composite image. In the composite display, registration between the tear thickness distribution image and the front image can be performed. This registration is performed, for example, through the registration of the three-dimensional image on which the tear thickness distribution image is based and the front image.

When a plurality of images or time-series images are collected, a composite image of the tear thickness distribution image and the front image based on one or more three-dimensional images included in the images can be displayed on the display device 2. When displaying a plurality of composite images, it is possible to arrange them in chronological order. It is also possible to switch and display a plurality of composite images in chronological order.
(Time series image)
In order to acquire a time-series image in FIG. 3, for example, the processes of steps S3 and S4 are repeatedly executed for a predetermined number of times or time, and the acquired image (data) is stored in the storage unit 20 as a time-series image. It is stored as (data), and in step S5, the display control unit 11 (and the data processing unit 40) displays the time-series image (data) read from the storage unit 20 on the display device 2 as a plurality of still images or moving images. Just do it.

FIG. 4 shows a flowchart showing an operation for creating tear thickness distribution information. This flowchart shows an example of the detailed flowchart of step S3 of FIG.
Regarding the measurement of the thickness of the thin film / tear film, for example, a well-known or known method as described in the following Internet homepage or literature can be used.
-Https: // www. hamamatsu. com / jp / ja / technology / innovation / spectroscopy / index. html
-International Publication No. 2016/147782-Fogt et al. "Interferometric measurement of tear film thickness by use of spectral oscillations", J. et al. Opt. Soc. Am. A / Vol. 15, No. 1 / January 1998, pp.268-275

The tear film thickness measurement according to this embodiment will be described below.
Generally, when light (white light or the like) is incident on the tear film, multiple reflections occur inside the layer, and the phase difference of each multiple reflected light is determined by the wavelength of light and the optical path length. here,
Optical path length = distance that light reciprocates in the tear film x refractive index of tear fluid.
In this way, the color of the reflected light correlates with the thickness of the tear film (note that the refractive index of the tear fluid is assumed to be unknown for each individual, so a predetermined value / predetermined value is used. Will be used.) In general, the correlation between the color of light and the thickness of the tear film has a linear relationship, and the following equation can be given as an example.
2nd = (m + (1/2)) λ
Here, n: refractive index, d: thickness of tear film, m: integer, λ: wavelength (corresponding to color)

However, even if the "color" is known, the "film thickness" cannot be specified unless the spectral distribution is known. Therefore, if both the spectral distribution and the "color" in a certain region (at least the central part of the cornea such as the apex of the cornea) can be measured and the "layer thickness" can be obtained from the spectral distribution at this time, "layer thickness" can be obtained. The relationship between "color" and "layer thickness" can be obtained.
In the present embodiment, the relationship between "color" and "layer thickness" is obtained by measuring the spectral distribution (spectral reflection spectrum) at least in the central part of the cornea. Then, based on this relationship, the "layer thickness" is estimated from the "color" (obtained from the RGB color image) of other parts.
It should be noted that the spectral distribution (spectral reflection spectrum) measured not only at the central portion of the cornea but also at an appropriate predetermined position may be used as a reference.

Each step will be described below.
S101 When the wavelength sweep measurement of the light source unit is started, the image acquisition unit 30 changes (sweeps) the wavelength of the light source 31 under the control of the control processing unit 35, and has a specific substantially single wavelength (narrow wavelength range). Light is applied to at least the central part of the wavelength of the eye to be examined, and this reflected image is imaged by the camera 34. The image collecting unit 30 sweeps (changes) the wavelength in step S101 by the control processing unit 35, outputs the image acquired at each wavelength to the distribution information acquisition unit 44, and stores it in the storage unit 20. The acquired image also includes images at three wavelengths of R (near 600 nm), G (near 500 nm), and B (near 400 nm).
S102 Acquiring the spectral reflection distribution of the central part of the cornea The distribution information acquisition unit 44 obtains the reflectance at least at each wavelength of the central part of the cornea from the image input from the image collecting unit 30. For example, the distribution information acquisition unit 44 obtains the reflectance distribution for each wavelength of the cornea by multiplying the luminance value of at least the central part of the cornea of each image acquired at each wavelength by the spectral sensitivity of a known camera at each wavelength. .. The distribution information acquisition unit 44 stores the obtained reflectance distribution in the storage unit 20.

-S103 Calculation of layer thickness by spectrum analysis The distribution information acquisition unit 44 analyzes the obtained spectral reflection spectrum to obtain the tear film thickness value. Since the spectral distribution from the tear film becomes a peculiar spectrum depending on the film thickness, the film thickness can be obtained by analyzing this spectrum. As an analysis method, for example, analysis by curve fitting method (method for obtaining the thickness that minimizes the difference between the measured value of the spectrum and the theoretical value (eg, the square of the difference, etc.)) or analysis by the fast Fourier transform (FFT). An appropriate analysis method such as the above can be used.
In addition to the thickness of the entire tear film layer, the distribution information acquisition unit 44 can appropriately determine the thickness of each of the oil and fat layer, the aqueous layer, the mucin layer, etc. of the tear fluid in addition to the thickness of the entire tear film layer. ..
S104 Color image correlation calculation The distribution information acquisition unit 44 obtains the correlation between color and layer thickness from the reflection spectrum. The distribution information acquisition unit 44 stores the data of the correlation between the color and the layer thickness in the storage unit 20.
For example, the "layer thickness" is obtained in step S103, and the "color" is obtained in steps S101 and S102 at three wavelengths of R (near 600 nm), G (near 500 nm), and B (near 400 nm). Therefore, it can be obtained by obtaining a color image by superimposing these captured corneal images. Thereby, for example, m of the above-mentioned formula “2nd = (m + (1/2)) λ” can be specified, and the correlation between the color (wavelength) and the layer thickness can be obtained.

-S105 R Light-based wide-area corneal imaging Next, the distribution information acquisition unit 44 performs the same processing on each pixel for parts other than the apex of the cornea, and from the spectral distribution of the pixels corresponding to each part, the tear film. The thickness can be obtained, and the distribution of the thickness of the tear fluid can be obtained. Here, since the camera 34 is not a color camera (for example, a so-called black-and-white camera), it is not possible to directly observe the "color" on the cortex, but the wavelengths of the light source 31 are R (near 600 nm) and G (near 500 nm). A color image can be obtained by changing the wavelengths to three wavelengths of B and B (near 400 nm) and superimposing the captured corneal images.
First, the image collecting unit 30 obtains an image of the entire cornea (measurement range) with the light source color of the light source 31 as R. The image collecting unit 30 outputs the obtained image to the distribution information acquisition unit 44 and stores it in the storage unit 20. To do.
S106 Wide-range corneal imaging with G light Next, the image collecting unit 30 obtains an image of the entire cornea (measurement range) with the light source color of the light source 31 as G. The image collecting unit 30 outputs the obtained image to the distribution information acquisition unit 44 and stores it in the storage unit 20.
S107 Wide-range corneal imaging with B light Next, the image collecting unit 30 obtains an image of the entire cornea (measurement range) with the light source color of the light source 31 as B. The image collecting unit 30 outputs the obtained image to the distribution information acquisition unit 44 and stores it in the storage unit 20.
S108 Color image creation using RGB images Next, the distribution information acquisition unit 44 refers to the storage unit 20, and from the R image, G image, and B image obtained by the image collection unit 30, a color image (color of each region). Is obtained and stored in the storage unit 20. Since the distribution information acquisition unit 44 records images at each wavelength in visible light, a color image of the cornea (when the corneum is observed with a color camera) is obtained by superimposing the images at each wavelength at a predetermined ratio. Image) can be reproduced.

S109 color image layer thickness conversion The distribution information acquisition unit 44 refers to the storage unit 20 and sets the “color” of each region of the color image to “layer thickness” based on the correlation between the color and the layer thickness obtained in step S104. Convert (convert) to.
S110 Layer thickness map display The distribution information acquisition unit 44 creates a “layer thickness” of each part in a map shape, and displays it on the display device 22 by the display control unit 11. For example, the thickness distribution of the tear film can be shown by creating a pseudo-color thickness map in which the thickness of the tear film at each site on the obtained cornea is converted into a color and displaying it on the screen. In addition, by displaying the thickness map at each time side by side on the screen, it is possible to confirm the change over time. In addition, it can be presented as a pseudo moving image by switching the image for each time to the same part on the screen and displaying it. Further, the portion having a thickness less than the specified thickness may be emphasized and displayed, or the area of the portion may be obtained and displayed.

The image collecting unit 30 and / or the distribution information acquisition unit 44 stores the acquired, output, and / or input images and data such as the correlation between the color and the layer thickness in the storage unit 20 at an appropriate timing. And / or can be read from the storage unit 20 and displayed on the display device 2 by the display control unit 11. Further, in steps S105, S106, and S107, the acquisition order of the R, G, and B images can be appropriately determined.

(Time series processing)
After that, when the time series measurement is performed, the distribution information acquisition unit 44, the image acquisition unit 30, and the like perform loop processing in steps S105 and subsequent steps.
That is, when acquiring a time-series image, it is obtained by sequentially creating a layer thickness time-series map by repeating steps S105 and subsequent steps in FIG. 4 to obtain a color image. However, if three (RGB) images are always acquired to obtain one layer thickness map, it takes time, and the tear film may change during that time. Therefore, in the present embodiment, each image is acquired as follows. That is,
(I) The first layer thickness map is obtained from the first R image (R1), the first G image (G1), and the first B image (B1).
(Ii) Next, the second layer thickness map acquires the second R image (R2), and the first G image (G1) and the B image (B1) that have already been acquired are two. Obtained from the first R image (R2).
(Iii) Further, the third layer thickness map acquires the second G image (G2), and the already acquired first B image (B1) and second R image (R2). And obtained from the G image (G2).
If only one color image is updated and a map is continuously created in this way, the update process is reduced to 1/3 as compared with acquiring a three color image each time. The acquisition order of the R, G, and B images can be appropriately determined.

(Fig. 3, a modified example of "S4: Acquiring a frontal image of the anterior segment")
Since the image of the anterior segment of the eye has already been acquired as a color image in step S108 of FIG. 4, it is not necessary to reacquire it in step S4 of FIG. In this case, step S4 of FIG. 3 is omitted, and in the process of “displaying a composite image of the tear thickness distribution image and the front image” of step S5 of FIG. 3, the distribution information acquisition unit 44 performs step S108 of FIG. The layer thickness map obtained in step S110 of FIG. 4 may be superimposed and displayed on the anterior segment image obtained in.

As described above, the present embodiment is based on a new idea that, for example, the cornea is irradiated with the measurement light decomposed into color components on the light source side and detected by the camera. Therefore, since the spectroscope is not included in the configuration on the light receiving side, the configuration can be simple.

The configuration described above is only an example for preferably carrying out the present invention. Therefore, any modification (omission, substitution, addition, etc.) within the scope of the gist of the present invention can be appropriately applied.

(Configuration example)
The configuration examples of the present invention and / or the present embodiment are shown below.
[Configuration Example 1]
It is a tear layer thickness measuring device.
Reflected signal collection that has a light source unit, a light receiving element, a control processing unit, and an optical system, and collects a signal representing the tear film interface on the cornea by receiving the reflected light from the anterior segment of the eye to be inspected. Department and
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
A display control unit that displays information on the thickness of the tear layer acquired by the tear layer thickness information acquisition unit on the display unit.
With
The light source unit has a wide wavelength range under the control of the control processing unit, and irradiates the cornea with light having a wavelength pattern predetermined by the above optical system.
The image sensor receives the reflected light from the tear film through the optical system and receives it.
The control processing unit obtains an image of the tear film on the cornea from the signal received by the light receiving element, and outputs the image to the tear film thickness information acquisition unit.
Tear layer thickness measuring device.

[Configuration Example 2]
The tear film thickness measuring device according to the first configuration example.
The reflected signal collecting unit obtains a spectral reflection distribution in the light receiving element by changing the wavelength of the light source to a predetermined wavelength pattern.
The tear layer thickness information acquisition unit measures the thickness of the tear layer based on the spectral reflection distribution obtained by the light receiving element.
A tear film thickness measuring device characterized by this.

[Configuration Example 3]
The tear film thickness measuring device according to the configuration example 1 or 2.
The reflected signal collecting unit changes the wavelength of the light source, irradiates at least the central part of the cornea of the eye to be inspected, and images the reflected image.
The tear film thickness information acquisition unit obtains the reflectance at least at each wavelength in the central part of the cornea from the image captured by the reflection signal collection unit, obtains the spectral reflection spectrum, and analyzes the obtained spectral reflection spectrum. To find the tear layer thickness value, to find the correlation between color and layer thickness,
The tear film thickness information acquisition unit changes the wavelength of the light source to R, G, and B, and superimposes the captured corneal images to obtain a color image, and based on the correlation between the color and the layer thickness, the color is obtained. Convert the color of each area of the image to layer thickness,
The tear layer thickness information acquisition unit creates a layer thickness of each part in a map shape and displays it by the display control unit.
A tear film thickness measuring device characterized by this.

[Configuration Example 4]
The tear film thickness measuring device according to the configuration example 3.
At the first timing of the time series
The reflected signal collecting unit sets the color of the light source to R, G, and B, respectively, photographs a predetermined measurement range, and acquires an R image, a G image, and a B image.
The tear film thickness information acquisition unit obtains a color image of the cornea at the first timing by superimposing the R image, the G image, and the B image at a predetermined ratio.
At the second timing of the time series
The reflected signal collecting unit sets the color of the light source to any one of R, G, and B, captures each of the predetermined measurement ranges, and acquires an image.
The tear film thickness information acquisition unit superimposes an image newly taken with any one light source color and an image of two other light source colors already taken at a predetermined ratio. Obtain a color image of the cornea at the second timing,
A tear film thickness measuring device characterized by this.

[Configuration Example 5]
The tear film thickness measuring device according to any one of Configuration Examples 1 to 4.
It is placed in a position facing the eye to be inspected and further equipped with a placido ring.
The reflected signal collecting unit captures a ring image projected on the cornea of the eye to be inspected by the platid ring with the image sensor.
The tear layer thickness information acquisition unit measures the shape or curvature of the cornea based on the image obtained by the reflection signal collection unit, and the tear layer is obtained from the amount of deviation of the obtained corneal curvature from a predetermined reference value. Correct the thickness measurement result,
A tear film thickness measuring device characterized by this.

[Configuration Example 6]
The tear film thickness measuring device according to any one of Configuration Examples 1 to 5.
The light source is characterized by having a wideband wavelength sweep light source or a white light source containing near-infrared radiation and a grating, an LVF (Linear Variable Filter) or another spectrometer, and having wavelength selectivity. Tear layer thickness measuring device.

[Configuration Example 7]
The tear film thickness measuring device according to any one of Configuration Examples 1 to 6.
A front image acquisition unit for acquiring a front image of the cornea is further provided.
The display control unit causes the display unit to display a composite image of the tear distribution thickness distribution image acquired by the tear layer thickness information acquisition unit and the front image acquired by the front image acquisition unit. A featured tear layer thickness measuring device.

[Configuration Example 8]
The tear film thickness measuring device according to any one of Configuration Examples 1 to 7.
The tear film thickness information acquisition unit is a tear film thickness measuring device, further characterized in that a tear film destruction region is specified based on distribution information.

[Configuration Example 9]
The tear film thickness measuring device according to any one of Configuration Examples 1 to 8.
The tear film thickness measuring device is characterized in that the image sensor is an image sensor whose spectral sensitivity characteristics are known.

[Configuration Example 10]
It is a method for measuring the thickness of the tear film in the tear film thickness measuring device.
The tear film thickness measuring device is
Reflected signal collection that has a light source unit, a light receiving element, a control processing unit, and an optical system, and collects a signal representing the tear film interface on the cornea by receiving the reflected light from the anterior segment of the eye to be inspected. Department and
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
A display control unit that displays information on the thickness of the tear layer acquired by the tear layer thickness information acquisition unit on the display unit.
With
The light source unit has a wide wavelength range under the control of the control processing unit, and irradiates the cornea with light having a wavelength pattern predetermined by the above optical system.
The image sensor receives the reflected light from the tear film through the optical system and receives it.
The control processing unit obtains an image of the tear film on the cornea from the signal received by the light receiving element, and outputs the image to the tear film thickness information acquisition unit.
Tear layer thickness measurement method.

1 Ophthalmic examination device 2 Display device 10 Control unit 11 Display control unit 20 Storage unit 30 Image collection unit 40 Data processing unit 44 Distribution information acquisition unit 50 Operation unit

Claims (6)

It is a tear layer thickness measuring device.
A light source unit, a reflected signal collecting unit having a light receiving element and receiving reflected light from the anterior segment of the eye to be inspected, and a reflected signal collecting unit.
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
Display control unit and
Front image acquisition unit, which acquires the front image of the cornea,
With
The light source unit has a wide wavelength range and irradiates the cornea with light having a predetermined wavelength pattern.
The display control unit includes a distribution image of the thickness of the tear liquid acquired by the tear layer thickness information acquisition unit and a front image acquired by the front image acquisition unit by the reflected light from the received tear layer. Display the composite image of
Tear layer thickness measuring device.
The tear film thickness measuring device according to claim 1.
The reflected signal collecting unit obtains a spectral reflection distribution in the light receiving element by changing the wavelength of the light source to a predetermined wavelength pattern.
The tear layer thickness information acquisition unit measures the thickness of the tear layer based on the spectral reflection distribution obtained by the light receiving element.
A tear film thickness measuring device characterized by this.
The tear film thickness measuring device according to claim 1 or 2.
The reflected signal collecting unit changes the wavelength of the light source, irradiates at least the central part of the cornea of the eye to be inspected, and images the reflected image.
The tear film thickness information acquisition unit obtains the reflectance at least at each wavelength in the central part of the cornea from the image captured by the reflection signal collection unit, obtains the spectral reflection spectrum, and analyzes the obtained spectral reflection spectrum. To find the tear layer thickness value, to find the correlation between color and layer thickness,
The tear film thickness information acquisition unit changes the wavelength of the light source to R, G, and B, and superimposes the captured corneal images to obtain a color image, and based on the correlation between the color and the layer thickness, the color is obtained. Convert the color of each area of the image to layer thickness,
The tear layer thickness information acquisition unit creates a layer thickness of each part in a map shape and displays it by the display control unit.
A tear film thickness measuring device characterized by this.
The tear film thickness measuring device according to any one of claims 1 to 3.
It is placed in a position facing the eye to be inspected and further equipped with a placido ring.
The reflected signal collecting unit captures a ring image projected on the cornea of the eye to be inspected by the platid ring with the light receiving element.
The tear layer thickness information acquisition unit measures the shape or curvature of the cornea based on the image obtained by the reflection signal collection unit, and the tear layer is obtained from the amount of deviation of the obtained corneal curvature from a predetermined reference value. Correct the thickness measurement result,
A tear film thickness measuring device characterized by this.
The tear film thickness measuring device according to any one of claims 1 to 4.
The tear layer thickness information acquisition unit further sets the thickness of the liquid layer region, the oil layer region, or the combined region of the liquid layer region and the oil layer region below a predetermined threshold value, respectively. A tear film thickness measuring device, characterized in that it is specified as an oil layer region or a tear region destruction region.
It is a method for measuring the thickness of the tear film in the tear film thickness measuring device.
The tear film thickness measuring device.
A light source unit, a reflected signal collecting unit having a light receiving element and receiving reflected light from the anterior segment of the eye to be inspected, and a reflected signal collecting unit.
A tear layer thickness information acquisition unit that acquires information on the thickness of the tear layer based on the signal collected by the reflection signal collection unit, and a tear layer thickness information acquisition unit.
Display control unit and
Front image acquisition unit, which acquires the front image of the cornea,
With
The light source unit has a wide wavelength range and irradiates the cornea with light having a predetermined wavelength pattern.
The display control unit includes a distribution image of the thickness of the tear liquid acquired by the tear layer thickness information acquisition unit and a front image acquired by the front image acquisition unit by the reflected light from the received tear layer. Display the composite image of
Tear layer thickness measurement method.

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