JP7068869B2 - Tear layer thickness measuring device and method - Google Patents

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 measuring tear layer structure and evaporative rate, 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 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 device for "improvement" (paragraph 0005) is described.

International Publication No. WO2015-132788 Japanese Patent Application No. 2016-185076 Japanese Patent Application No. 2016-185077

However, in the prior art, since the tear film is spherical, the correction is performed on the premise that the shape of the cornea is a sphere having a predetermined radius of curvature. However, there are individual differences in the curvature of the cornea, and there is also a deviation from the spherical shape, so that an error may occur in the measurement result.
In view of the above points, the present invention makes the incident angle of the light applied to the tear film variable, and makes the measured light incident along the normal of the measurement site based on the measurement result of the corneal shape. The purpose is to measure the thickness of the tear film more accurately regardless of the shape of the cornea to be inspected.

According to the first solution of the present invention
It is a tear layer thickness measuring device.
It has a light source, a detection unit, a control processing unit, and a luminous flux direction changing member whose reflection direction is controlled by the control processing unit, and scans the anterior segment of the eye to be inspected to collect tears on the cornea. An image collection unit that collects the images to be represented, and
A distribution information acquisition unit that acquires distribution information of tear thickness based on the image collected by the image collection unit, and a distribution information acquisition unit.
A display control unit that displays a distribution image of the thickness of tears acquired by the distribution information acquisition unit on the display unit, and a display control unit.
Equipped with
The light source emits light having a predetermined wavelength in the visible to near-infrared wavelength range under the control of the control processing unit.
The light beam direction changing member has a reflection direction determined by the control of the control reflection unit, reflects light from the light source, and irradiates the cornea.
The detection unit detects the reflected light from the cornea via the luminous flux direction changing member, and then detects the reflected light.
The control processing unit obtains an image of tears on the cornea based on the signal detected by the detection unit, and outputs the image to the distribution information acquisition unit.
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 layer in the tear layer thickness measuring device.
The tear film thickness measuring device is
It has a light source, a detection unit, a control processing unit, and a luminous flux direction changing member whose reflection direction is controlled by the control processing unit, and scans the anterior segment of the eye to be inspected to collect tears on the cornea. An image collection unit that collects the images to be represented, and
A distribution information acquisition unit that acquires distribution information of tear thickness based on the image collected by the image collection unit, and a distribution information acquisition unit.
A display control unit that displays a distribution image of the thickness of tears acquired by the distribution information acquisition unit on the display unit, and a display control unit.
Equipped with
The light source emits light having a predetermined wavelength in the visible to near-infrared wavelength range under the control of the control processing unit.
The light beam direction changing member has a reflection direction determined by the control of the control reflection unit, reflects light from the light source, and irradiates the cornea.
The detection unit detects the reflected light from the cornea via the luminous flux direction changing member, and then detects the reflected light.
The control processing unit obtains an image of tears on the cornea based on the signal detected by the detection unit, and outputs the image to the distribution information acquisition unit.
A method for measuring the thickness of the tear film is provided.

According to the present invention, the thickness of the tear film can be measured more accurately by making it possible to individually set the incident angle and the focus position of the light applied to the tear film.

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. The schematic diagram for demonstrating another structure of an image acquisition part. The schematic diagram for demonstrating the other structure of the image acquisition part. A flowchart showing an operation for creating tear thickness distribution information.

An exemplary embodiment of the 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, images may be collected by scanning one-dimensionally or two-dimensionally. 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 shooting the anterior segment of the eye at a predetermined time interval. It may be the obtained still image group.
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 between the front surface reflection and the back surface reflection of the tear film layer (for example, an oil layer).

The ophthalmologic examination apparatus of the embodiment may have 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 has 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 prepared.

The function of collecting (time-series) images is realized by, for example, a known configuration for providing the function of a slit lamp microscope, a known configuration for providing the function of an OCT apparatus, and the like (image collecting unit). ..

The configuration of the slit lamp microscope includes, for example, an illumination optical system that projects illumination light onto the eye to be inspected, and a photographing optical system that detects the return light of the illumination light from the anterior segment of the eye with an image sensor. The illumination optical system can project slit light and includes a mechanism for changing the slit width. Further, a mechanism for changing the relative positions of the illumination optical system and the photographing optical system (relative orientations of both optical axes) is provided. Further, a data processing system for processing an image obtained by an image sensor and a control system for performing various controls are provided.

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) It 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 apparatus of the embodiment include, for example, 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 working 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 ophthalmologic examination device will be described. In this embodiment, an ophthalmologic examination apparatus having a function (image collecting unit) for collecting (time series) images will be described.

FIG. 1 shows an example of the configuration of the ophthalmologic examination device of the present embodiment. The ophthalmologic examination apparatus 1 collects (time-series) images by repeatedly photographing the eye to be inspected, and analyzes each of the plurality of images included in the (time-series) images to identify 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 the thickness distribution of tears (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 apparatus 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" is, 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)) , FPGA (Field Protocol 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>
The image collecting unit 30 collects one or more images representing tears on the cornea by photographing the anterior eye portion of the eye to be inspected. Further, images may be collected by scanning one-dimensionally or two-dimensionally. 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 schematic diagram for explaining the configuration of the image acquisition unit. The image collecting unit 30 includes an optical system, a drive system, a control system, and a processing system for executing shooting. For example, the image collecting unit 30 includes a wideband wavelength sweeping light source 31, a half mirror 32, a galvano mirror 33, a photodiode 34, a control processing unit 35, a lens, and the like.
The broadband wavelength sweep light source 31 may have wavelength selectivity by combining, for example, a white light source containing near-infrared radiation with a spectroscope (spectrometer) 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 in or externally attached to the wideband wavelength sweep light source 31.
The control processing unit 35 controls the wideband wavelength sweep light source 31 and the galvano mirror 33, detects a signal from the photodiode 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 light from the broadband wavelength sweep light source 31 is reflected by the galvano mirror 33 and irradiates the cornea. The wideband wavelength sweep light source 31 detects the reflected light from the cornea through the galvano mirror 33 and the half mirror 32 by a detector 34 such as a photodiode, and the distribution information acquisition unit 44 measures the thickness of the tear film on the cornea. To. For example, the image collecting unit 30 can obtain the distribution of the reflectance for each wavelength by irradiating the same portion on the cornea with light of a plurality of wavelengths and detecting the amount of the reflected light, and the distribution information acquisition unit 30. With 44, the thickness of the tear film at the irradiation site can be measured. Further, the image collecting unit 30 scans the luminous flux on the cornea with the galvano mirror 33, and the distribution information acquisition unit 44 can obtain a plurality of sites on the cornea or a one-dimensional or two-dimensional tear film layer.

FIG. 4 shows a schematic diagram for explaining another configuration of the image acquisition unit.
The galvano mirror 33 can be scanned one-dimensionally or two-dimensionally. The galvano mirror 33 is provided with a drive mechanism that moves back and forth with respect to the eye to be inspected, in addition to changing the direction by rotation, so that the light is incident on the tear film by changing the direction of incidence of the measured light on the eye to be inspected. Can be done. In this case, light can be incident from the normal direction of the eye to be inspected or the spherical surface of the cornea.
In addition to the galvano mirror (galvano scanner) 33, an appropriate reflection direction variable member such as a reflection direction variable mirror can be used.

Further, FIG. 5 shows a schematic diagram for explaining still another configuration of the image acquisition unit. (Here, the reference numeral 33 is referred to as a scanner.)
The light from the wavelength sweep type light source 31 passes through the lens and the half mirror 32, is reflected by the mirror, and reaches the scanner 33. The scanner 33 can change the angle of the reflected light beam such as a galvano mirror, and is two-dimensional by combining two scanners (mirrors) that change in the paper surface (y-axis) and in the plane perpendicular to the paper surface (X-axis). Allows in-plane scanning. The light reflected by the mirror of the scanner 33 at an arbitrary angle passes through the dichroic mirror and the objective lens and is applied to the cornea to be inspected. Here, the positions of the centers of curvature of the scanner 33 and the cornea to be inspected are arranged so as to be substantially conjugate, so that the light rays deflected by the scanner 33 are incident along the normal line of the cornea. Light rays incident along the normal line of the cornea (perpendicular to the surface of the cornea) are reflected by the cornea (interface of tears) and returned to the scanner 33 through the objective lens. The light flux reflected by the scanner 33 is reflected by the mirror and the half mirror, and is focused on the diaphragm by the lens. The luminous flux transmitted through the diaphragm is detected by the PD (photodiode) 34. Here, the light source, the corneal surface, and the diaphragm are arranged in a conjugate.

The broadband wavelength sweep type light source 31 includes continuous or discrete wavelengths at least 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 spectroscope or a color filter. It is assumed that PD34 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 PD34 may be known by calibration or the like. The cornea of the eye to be inspected and the light receiving part of the camera are optically coupled to each other, and an image of the cornea is formed on the light receiving part of the camera.

The optical system from the light source 31 to the PD 34 is housed in a housing, and the corneal apex of the eye to be inspected coincides with the optical axis of the objective lens (X, Y direction) and is constant from the objective lens to the corneal apex (Z direction). ) Align. 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 the measurement (auto start). Alternatively, the measurement may be started by pressing the measurement switch by the operator (manual start).
Further, the blink may be monitored by the camera 34 and the measurement may be started by using this as a trigger.

When the measurement is started, first, the angle of the scanner 33 is adjusted to the angle (0 °) at which the measurement light irradiates the corneal membrane along the optical axis of the objective lens, and the wideband wavelength sweep type light source 31 has a specific substantially single wavelength ( The wavelength range is narrow) is applied to the lens to be examined, and the reflected light is received by the PD34. The wavelength is swept (changed) to obtain the amount of light at each wavelength. The amount of light received by the PD34 acquired at each wavelength is multiplied by the spectral sensitivity of the PD34 at each wavelength to obtain a reflectance distribution for each wavelength of the cornea. By performing spectral analysis on the obtained spectral distribution, the thickness of each of the oil and fat layer, the aqueous layer, and the mucin layer of tears can be obtained.

By changing the angle of the scanner 33 and performing the same processing 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 tear thickness distribution can be obtained. .. Since there is a correlation between the angle of the scanner 33 and the part on the cornea, the reflectance at each wavelength at each part is recorded. Therefore, by combining the obtained signals, a color image of the cornea (the cornea is captured by a color camera). It is possible to reproduce the image when observed).

When observing the time-series change of the tear film continuously, the first measurement (arbitrary 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.
At each angle of the scanner 33 (each part on the cortex), the wavelength of the light source is changed to three wavelengths of R (near 600 nm), G (near 500 nm), and B (near 400 nm), and the reflected light amount data is superimposed on each. Therefore, a color image can be obtained, and by acquiring and comparing the color images in time series, it is possible to know the relative change over time of the tear film. 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 for a wide wavelength range. On the other hand, for the second and subsequent measurements, it is only necessary to acquire three images (RGB) for one measurement, so the measurement time can be significantly shortened, and the change in tear film thickness at short time intervals can be seen. 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, since it has almost the same configuration as the SLO, it can be easily achieved by sharing most of the parts with the multifunction device with the SLO.

(Corneal curvature error correction)
In order to efficiently acquire the corneal reflex of the incident light beam, it is desirable that the light beam is incident perpendicular to each part of the cornea. In addition, it is necessary to keep the corneal surface and the diaphragm conjugate in order to obtain high-resolution tear layer thickness data. It is 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 with a larger (loose) radius of curvature from the center to the periphery. Is. In addition, the corneal astigmatism may deviate from the spherical surface such as the eye or keratoconus. When the alignment is completed so that the cornea is coupled to the ideal r7.7 sphere by the Z alignment signal, the scanner and the center of the cornea (r7.7 mm) are configured to be conjugated. (The reverse is also possible). However, if the radius of curvature of the cornea deviates from 7.7 mm, the relationship between the apex of the cornea and the center of curvature of the cornea is broken, and one of them is displaced from the expected position. Therefore, it becomes difficult to obtain the optimum result.

(Purachido method)
A purachido plate having a plurality of concentric translucent portions is arranged on a light-shielding plate around the objective lens. The purachido plate is illuminated by a light source (near-infrared LED, etc.) 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 multi-ring virtual image due to the curvature of the cornea. The image of the virtual image is reflected by a dichroic mirror and imaged by a camera, 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. Highly accurate tear layer thickness can be obtained by correcting the obtained corneal shape for the tear layer thickness data.

(OCT method)
The device has an anterior ocular OCT device capable of acquiring an anterior 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.

Further, 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 eye portion (cornea or the like), and collects a (time series) image consisting of a series of front images (front image group). The front image collecting unit has, for example, a configuration similar to that of 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 distribution information of the thickness of the tear fluid by analyzing each of the plurality of images included in the (time series) image.

For a fluorescence contrast image using a fluorescent dye such as fluorescein, distribution information can be created by estimating the thickness of the tear fluid based on the fluorescence intensity (pixel value) as in the conventional case. Further, as in the conventional case, it is also possible to create distribution information by estimating the thickness of the tear fluid based on the interference pattern between the front surface reflection and the back surface reflection of the tear film layer (for example, the oil layer).

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. When a (time-series) image is obtained and segmentation is applied to each of the plurality of three-dimensional images contained therein, the tear thickness distribution information corresponding to each three-dimensional image is acquired.

The distribution information acquisition unit 44 obtains the thickness of the tear film at each measurement point within the scan range 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.

By such treatment, for example, the distance between the front surface (boundary between the oil layer and the air) and the back surface (the boundary between the oil layer and the liquid layer) of the oil layer and the front surface of the liquid layer (the boundary with the liquid layer of the oil 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 thickness at each measurement point is calculated, for example, by counting the number of pixels corresponding to the tear film along a predetermined measurement direction, and the number of pixels obtained by the process and the distance (unit) corresponding to the pixel pitch. Includes the process of multiplying the distance).

Here, the direction for counting the number of pixels (the measurement direction) is arbitrary, and for example, the A-line direction in scanning or the normal direction at each position on the corneal surface can be applied as the measurement direction. The process of specifying the normal direction at each position of the corneal surface includes, for example, approximation of the curved surface of the corneal surface, specification of the tangent plane at each position, and specification of the normal of each tangent plane.

The distribution information acquisition unit 44 can also apply a process (flattening) for flattening a specified predetermined region (for example, the surface of the cornea) to a three-dimensional image. Flattening makes it easier to calculate the thickness. Further, by displaying the flattened image, the thickness distribution can be easily grasped.

The distribution information acquisition unit 44 can also specify the tear destruction region based on the acquired tear 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 for an ophthalmic device 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 eye portion (cornea or the like). 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. For example, the front image acquisition unit 60 may include an optical system of a slit lamp microscope, an optical system of a fundus camera, and the like.

In the second example, the front image acquisition unit 60 may include a configuration for acquiring a front image of the anterior eye portion of the eye to be inspected from an external device. For example, the front image acquisition unit 60 may include a communication device for transmitting / receiving data via a communication line such as a LAN, the Internet, or a dedicated line. In this case, the front image acquisition unit 60 may acquire, for example, the front image of the anterior segment of the eye to be inspected stored in the electronic medical record system or the image archiving system using the patient ID, DICOM tag, or the like as a search query. can.

Registration can be performed between the image collected by the image collecting unit 30 and the front image acquired by the front image acquisition unit 60. Registration is performed, for example, by detecting a characteristic site (cornea apex, pupil, pupil center, pupil center of gravity, iris, iris center, iris center of gravity, etc.) from both images, and using both images as a reference. It can be done through the process of alignment.

Similarly, various maps such as a tear thickness distribution map, a fracture area distribution map, and an evaluation result distribution map can be registered with the front image acquired by the front image acquisition unit 60. This registration is performed using, for example, the result of registration between the three-dimensional image on which the map is based and the front image.

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

(S3: Create tear thickness distribution information)
(For details, refer to FIG. 6 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. 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 more images showing tears on the cornea are collected. Further, images may be collected by scanning one-dimensionally or two-dimensionally.

The display control unit 11 can display the collected images 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 the time-series images are collected, one or more three-dimensional images included in the time-series images can be rendered, and the obtained one or more rendered images 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 images are collected, the blink 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).

Subsequently, 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 solution.

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

The timing for acquiring the front image may be arbitrary. For example, the front image of the anterior eye portion can be acquired by accessing the electronic medical record system or the like before or after step S3, or by photographing the anterior eye portion. Alternatively, the front image of the anterior eye portion 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 thickness distribution information created in step S3, and the tear 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 an image process for synthesizing the tear thickness distribution image and the front image, and a control for displaying the composite image formed by the image processing. In another example, the composite display includes a control of superimposing the tear thickness distribution image and the front image 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 a tear thickness distribution image based on one or more three-dimensional images included therein and a front image can be displayed on the display device 2. When displaying a plurality of composite images, it is possible to arrange them according to the time series. 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 by a plurality of still images or moving images. Just do it.

FIG. 6 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. Mol. Opt. Soc. Am. A / Vol. 15, No. 1 / January 1998, pp.268-275

The tear layer 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 the light and the optical path length. here,
Optical path length = distance for light to reciprocate 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 layer (note that the refractive index of the tear film is assumed to be unknown for each individual, so a predetermined value / fixed 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 is 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 (in this example, 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, " 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 at an appropriate predetermined position may be used as a reference, not limited to the central portion of the cornea.

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 (wavelength range is narrow). Light is applied to at least the central part of the cornea of the eye to be inspected, and this reflected image is captured 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 pixel in 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 Layer thickness calculation by spectral 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 the analysis method, for example, analysis by curve fitting method (method for finding 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.
As the tear film thickness, 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 fluid layer. ..
S104 Color image correlation calculation The distribution information acquisition unit 44 obtains the correlation between the color and the 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 photographed 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 Wide-range corneal imaging with light Next, the distribution information acquisition unit 44 performs the same processing on each pixel for the parts other than the apex of the cornea, so that the tear film layer is obtained from the spectral distribution of the pixels corresponding to each part. 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 set to R (near 600 nm) and G (near 500 nm). A color image can be obtained by changing the wavelengths to 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. 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 B Wide-range corneal imaging with 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 corneal membrane (when the corneal membrane is observed with a color camera) is obtained by superimposing the images according to 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 to (convert).
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 layer can be shown by creating a pseudo color thickness map in which the thickness of the tear layer 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. Further, by switching the image for each time to the same part on the screen and displaying it, it can be presented as a pseudo moving image. Further, the portion 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 each 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 carried out, 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, it takes time to always acquire three (RGB) images to obtain one layer thickness map, and it is conceivable that 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, in the second layer thickness map, the second R image (R2) is acquired, and the already acquired first G image (G1) and B image (B1) are obtained. 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).
In this way, if only one color image is updated and a map is continuously created, 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 of the eye")
Since the image of the anterior eye portion 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 in FIG. 3 is omitted, and in the process of “displaying a composite image of the tear thickness distribution image and the front image” in step S5 in FIG. 3, the distribution information acquisition unit 44 performs step S108 in FIG. The layer thickness map obtained in step S110 of FIG. 4 may be superimposed and displayed on the anterior eye portion image obtained in.

As described above, in the present embodiment, the thickness of the tear film is measured more accurately by turning the reflection direction variable mirror at a predetermined angle and changing the incident angle of the light applied to the tear film. Can be done. Further, by turning the variable reflection direction mirror by a predetermined angle and moving it back and forth, for example, light can be incident from the normal direction of the tear film which is a spherical surface, and the thickness of the tear film can be measured more accurately. Can be done.
Further, in FIGS. 2 to 5 and the like of the present embodiment, an example in which the light reflection direction is variable by a reflection direction variable member such as a galvano mirror (or scanner) 33 is shown, but the present invention is not limited to this. As a device configuration for transmitting light, a light transmission direction variable member may be used instead of the galvano mirror (or scanner) 33. As described above, the direction of the light flux can be controlled by using an appropriate light flux direction changing member such as a member for changing the reflection direction or a member for changing the transmission direction.

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.

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 (9)

It is a tear layer thickness measuring device.
It has a light source, a detection unit, a control processing unit, and a luminous flux direction changing member whose traveling direction of light rays is controlled by the control processing unit. An image collection unit that collects images representing liquids,
A distribution information acquisition unit that acquires distribution information of tear thickness based on the image collected by the image collection unit, and a distribution information acquisition unit.
A display control unit that displays a distribution image of the thickness of tears acquired by the distribution information acquisition unit on the display unit, and a display control unit.
Equipped with
The light source emits light having a predetermined wavelength in the visible to near-infrared wavelength range under the control of the control processing unit.
The light beam direction changing member is configured so that the reflection direction is determined and the distance to the eye to be inspected is variably driven, and the distance and angle to the eye to be inspected are controlled by the control processing unit. Then, the angle of incidence of the measured light on the eye to be inspected is adjusted, the light from the light source is reflected, and the cornea is irradiated.
The detection unit detects the reflected light from the cornea via the luminous flux direction changing member, and then detects the reflected light.
The control processing unit obtains an image of tears on the cornea based on the signal detected by the detection unit, and outputs the image to the distribution information acquisition unit .
The image collecting unit irradiates the same site on the cornea with light of a plurality of wavelengths and detects the amount of reflected light, and the distribution information acquisition unit obtains a reflectance distribution for each wavelength and irradiates the irradiation site. A tear film thickness measuring device characterized by measuring the thickness of the tear film.
The tear film thickness measuring device according to claim 1 .
The control processing unit further controls the light flux direction changing member to cause the incident angle of the measured light to be incident on the tear film in the normal direction with respect to the surface of the eye to be inspected or the cornea. Tear layer thickness measuring device.
The tear film thickness measuring device according to claim 1 or 2 .
The image collecting unit is a tear film thickness measuring device, characterized in that the luminous flux direction changing member scans a light beam on the cornea to obtain a tear film thickness at a plurality of sites on the cornea.
The tear film thickness measuring device according to any one of claims 1 to 3 .
The image 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 distribution information acquisition unit obtains a spectral reflection spectrum by obtaining a reflectance at at least each wavelength in the central part of the cortex from an image captured by the image collecting unit, and analyzes the obtained spectral reflection spectrum to analyze the tear film. Find the thickness value, find the correlation between color and layer thickness,
The distribution information acquisition unit changes the wavelength of the light source to R, G, and B, superimposes the captured corneal images, obtains a color image, and based on the correlation between the color and the layer thickness, each of the color images. Converts the color of the area to the layer thickness,
The distribution information acquisition unit creates a map of the layer thickness of each portion 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 claim 4 .
At the first timing in the time series
The image collecting unit sets the colors of the light source to R, G, and B, photographs a predetermined measurement range, respectively, and acquires an R image, a G image, and a B image.
The distribution 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 in the time series
The image 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 distribution information acquisition unit superimposes an image newly taken with any one light source color and an image of the other two light source colors already taken at a predetermined ratio, thereby performing a second method. Get a color image of the timing corneum,
A tear film thickness measuring device characterized by this.
The tear film thickness measuring device according to any one of claims 1 to 5 .
The light source is characterized by having a broadband wavelength sweep light source, or a white light source containing near-infrared radiation, and a light source having a grating, an LVF (Linear Variable Filter), or another spectrometer and having wavelength selectivity. Tear layer thickness measuring device.
The tear film thickness measuring device according to any one of claims 1 to 6 .
A front image acquisition unit for acquiring the front image of the cornea is further provided.
The display control unit is characterized in that a composite image of a distribution image of the thickness of tears acquired by the distribution information acquisition unit and a front image acquired by the front image acquisition unit is displayed on the display unit. Tear layer thickness measuring device.
The tear film thickness measuring device according to any one of claims 1 to 7 .
The distribution information acquisition unit is a tear film layer thickness measuring device, further characterized by identifying a tear film destruction region based on the distribution information.
It is a method for measuring the thickness of the tear layer in the tear layer thickness measuring device.
The tear film thickness measuring device is
It has a light source, a detection unit, a control processing unit, and a luminous flux direction changing member whose traveling direction of light rays is controlled by the control processing unit. An image collection unit that collects images representing liquids,
A distribution information acquisition unit that acquires distribution information of tear thickness based on the image collected by the image collection unit, and a distribution information acquisition unit.
A display control unit that displays a distribution image of the thickness of tears acquired by the distribution information acquisition unit on the display unit, and a display control unit.
Equipped with
The light source emits light having a predetermined wavelength in the visible to near-infrared wavelength range under the control of the control processing unit.
The light beam direction changing member is configured so that the reflection direction is determined and the distance to the eye to be inspected is variably driven, and the distance and angle to the eye to be inspected are controlled by the control processing unit. Then, the angle of incidence of the measured light on the eye to be inspected is adjusted, the light from the light source is reflected, and the cornea is irradiated.
The detection unit detects the reflected light from the cornea via the luminous flux direction changing member, and then detects the reflected light.
The control processing unit obtains an image of tears on the cornea based on the signal detected by the detection unit, and outputs the image to the distribution information acquisition unit .
The image collecting unit irradiates the same site on the cornea with light of a plurality of wavelengths and detects the amount of reflected light, and the distribution information acquisition unit obtains a reflectance distribution for each wavelength and irradiates the irradiation site. A method for measuring the thickness of the tear film, which comprises measuring the thickness of the tear film.

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