Patent Publication Number: US-2023154010-A1

Title: Image processing method, image processing device, and program

Description:
TECHNICAL FIELD 
     The present invention relates to an image processing method, an image processing device, and a program. 
     BACKGROUND ART 
     U.S. Pat. No. 7,445,337 discloses generating a fundus image in which a periphery of a fundus region (circular shape) is infilled in black as a background color, and displaying the fundus image on a display. Sometimes trouble such as mis-detection occurs when performing image processing of such a fundus image having an infilled periphery. 
     SUMMARY OF INVENTION 
     An image processing method of a first aspect of the technology disclosed herein includes a processor acquiring a first fundus image of an examined eye including a foreground area and a background area other than the foreground area, and the processor generating a second fundus image by performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
     An image processing device of a second aspect of the technology disclosed herein includes a memory, and a processor coupled to the memory. The processor acquires a first fundus image of an examined eye including a foreground area and a background area other than the foreground area, and generates a second fundus image by performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
     A program of a third aspect of the technology disclosed herein causes a computer to execute processing including acquiring a first fundus image of an examined eye including a foreground area and a background area other than the foreground area, and generating a second fundus image by performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram of an ophthalmic system  100 . 
         FIG.  2    is a schematic configuration diagram illustrating an overall configuration of an ophthalmic device  110 . 
         FIG.  3    is a diagram illustrating a UWF RG color fundus image UWFGP obtained by imaging a fundus of an examined eye  12  with an ophthalmic device  110 , and a fundus image (fundus camera image) FCGQ obtained by imaging the fundus of the examined eye  12  with a non-illustrated fundus camera. 
         FIG.  4    is a block diagram of configuration of an electrical system of a server  140 . 
         FIG.  5    is a block diagram illustrating functionality of a CPU  262  of a server  140 . 
         FIG.  6    is a flowchart illustrating an image processing program. 
         FIG.  7    is a flowchart of a retinal blood vessel removal processing program of step  300  of  FIG.  6   . 
         FIG.  8    is a flowchart illustrating a background infill processing program of step  302  of  FIG.  6   . 
         FIG.  9    is a flowchart illustrating a processing program to extract blood vessels of step  306  of  FIG.  6   . 
         FIG.  10 A  is a diagram illustrating a choroidal vascular image G 1 . 
         FIG.  10 B  is a diagram illustrating a background processing complete image G 2 . 
         FIG.  10 C  is a diagram illustrating a blood vessel emphasis image G 3 . 
         FIG.  10 D  is a diagram illustrating a blood vessel extraction image G 4 . 
         FIG.  11 A  is a diagram illustrating a choroidal vascular image G 1  obtained with related technology. 
         FIG.  11 B  is a diagram illustrating a blood vessel emphasis image G 7  obtained with related technology. 
         FIG.  11 C  is a diagram illustrating a threshold value image G 8  obtained with related technology. 
         FIG.  11 D  is a diagram illustrating a blood vessel extraction image G 9  obtained with conventional technology. 
         FIG.  12    is a diagram illustrating a foreground area FG, a background area BG, and a boundary BD in a choroidal vascular image G 1 . 
         FIG.  13 A  is a diagram of a Modified Example 1 of background infill processing and illustrates a way in which a pixel value of each of the pixels of the background area BG is transformed into a value of a pixel of the foreground area FG nearest in distance to the respective pixel. 
         FIG.  13 B  is a diagram schematically illustrating a foreground area FG and a background area BG in a choroidal vascular image G 1 . 
         FIG.  13 C  is a diagram of a Modified Example 2 of background infill processing and illustrates transforming a pixel value of each of the pixels of the background area BG using a value larger than the value of the respective pixel by a specific value. 
         FIG.  13 D  is a diagram of a Modified Example 3 of background infill processing and illustrates transforming a pixel value of each of the pixels of the background area BG using a value smaller than a value a pixel of the foreground area FG nearest in distance to the respective pixel by a specific value. 
         FIG.  13 E  is a diagram of a Modified Example 4 of background infill processing and illustrates transforming a pixel value of each of the pixels of the background area BG to an average value of all pixels of the foreground area FG. 
         FIG.  13 F  is a diagram of a Modified Example 5 of background infill processing and illustrates transforming a pixel value of each of the pixels of the background area BG so as to be gradually greater as a distance from a center CP of the foreground area FG increases. 
         FIG.  13 G  is a diagram of a Modified Example 6 of background infill processing and illustrates transforming a pixel value of each of the pixels of the background area BG so as to be gradually smaller as a distance from a center CP of the foreground area FG increases. 
         FIG.  14    is a diagram illustrating an examination screen  400 A. 
         FIG.  15    is a diagram illustrating an examination screen  400 B. 
         FIG.  16    is a diagram illustrating a combined image G 14  obtained by overlaying a blood vessel extraction image G 4  on an original fundus image (UWF RG color fundus image UWFGP). 
         FIG.  17    is a diagram illustrating emphasizing blood vessels by applying a frame to blood vessels bt. 
         FIG.  18    is a diagram illustrating a blurred image Gb obtained by blurring a blood vessel emphasis image G 3 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Detailed explanation follows regarding a first exemplary embodiment of the present invention, with reference to the drawings. 
     Explanation follows regarding a configuration of an ophthalmic system  100 , with reference to  FIG.  1   . As illustrated in  FIG.  1   , the ophthalmic system  100  includes an ophthalmic device  110 , an eye axial length measurement device  120 , a management server device (referred to hereafter as “server”)  140 , and an image display device (referred to hereafter as “viewer”)  150 . The ophthalmic device  110  acquires an image of the fundus. The eye axial length measurement device  120  measures the axial length of the eye of a patient. The server  140  stores fundus images that were obtained by imaging the fundus of patients using the ophthalmic device  110  in association with patient IDs. The viewer  150  displays medical information such as fundus images acquired from the server  140 . 
     The server  140  is an example of an “image processing device” of technology disclosed herein. 
     The ophthalmic device  110 , the eye axial length measurement device  120 , the server  140 , and the viewer  150  are connected together through a network  130 . 
     Next, explanation follows regarding a configuration of the ophthalmic device  110 , with reference to  FIG.  2   . 
     For ease of explanation, scanning laser ophthalmoscope is abbreviated to SLO. Optical coherence tomography is also abbreviated to OCT. 
     With the ophthalmic device  110  installed on a horizontal plane and a horizontal direction taken as an X direction, a direction perpendicular to the horizontal plane is denoted a Y direction, and a direction connecting the center of the pupil at the anterior eye portion of the examined eye  12  and the center of the eyeball is denoted a Z direction. The X direction, the Y direction, and the Z direction are thus mutually perpendicular directions. 
     The ophthalmic device  110  includes an imaging device  14  and a control device  16 . The imaging device  14  is provided with an SLO unit  18 , an OCT unit  20 , and an imaging optical system  19 , and acquires a fundus image of the fundus of the examined eye  12 . Two-dimensional fundus images that have been acquired by the SLO unit  18  are referred to hereafter as SLO images. Tomographic images, face-on images (en-face images) and the like of the retina created based on OCT data acquired by the OCT unit  20  are referred to hereafter as OCT images. 
     The control device  16  includes a computer provided with a Central Processing Unit (CPU)  16 A, Random Access Memory (RAM)  16 B, Read-Only Memory (ROM)  16 C, and an input/output (I/O) port  16 D. 
     The control device  16  is provided with an input/display device  16 E connected to the CPU  16 A through the I/O port  16 D. The input/display device  16 E includes a graphical user interface to display images of the examined eye  12  and to receive various instructions from a user. An example of the graphical user interface is a touch panel display. 
     The control device  16  is also provided with an image processing device  16 G connected to the I/O port  16 D. The image processing device  16 G generates images of the examined eye  12  based on data acquired by the imaging device  14 . The control device  16  is also provided with a communication interface (I/F)  16 F connected to the I/O port  16 D. The ophthalmic device  110  is connected to the eye axial length measurement device  120 , the server  140 , and the viewer  150  through the communication interface (I/F)  16 F and the network  130 . 
     Although the control device  16  of the ophthalmic device  110  is provided with the input/display device  16 E as illustrated in  FIG.  2   , the technology disclosed herein is not limited thereto. For example, a configuration may adopted in which the control device  16  of the ophthalmic device  110  is not provided with the input/display device  16 E, and instead a separate input/display device is provided that is physically independent of the ophthalmic device  110 . In such cases, the display device is provided with an image processing processor unit that operates under the control of the CPU  16 A in the control device  16 . Such an image processing processor unit may display SLO images and the like based on an image signal output as an instruction by the CPU  16 A. 
     The imaging device  14  operates under the control of the CPU  16 A of the control device  16 . The imaging device  14  includes the SLO unit  18 , the imaging optical system  19 , and the OCT unit  20 . The imaging optical system  19  includes a first optical scanner  22 , a second optical scanner  24 , and a wide-angle optical system  30 . 
     The first optical scanner  22  scans light emitted from the SLO unit  18  two dimensionally in the X direction and the Y direction. The second optical scanner  24  scans light emitted from the OCT unit  20  two dimensionally in the X direction and the Y direction. As long as the first optical scanner  22  and the second optical scanner  24  are optical elements capable of deflecting light beams, they may be configured by any out of, for example, polygon mirrors, mirror galvanometers, or the like. A combination thereof may also be employed. 
     The wide-angle optical system  30  includes an objective optical system (not illustrated in  FIG.  2   ) provided with a common optical system  28 , and a combining section  26  that combines light from the SLO unit  18  with light from the OCT unit  20 . 
     The objective optical system of the common optical system  28  may be a reflection optical system employing a concave mirror such as an elliptical mirror, a refraction optical system employing a wide-angle lens, or may be a reflection-refraction optical system employing a combination of a concave mirror and a lens. Employing a wide-angle optical system that utilizes an elliptical mirror, wide-angle lens, or the like enables imaging to be performed not only of a central portion of the fundus where the optic nerve head and macular are present, but also of the retina at a peripheral portion of the fundus where an equatorial portion of the eyeball and vortex veins are present. 
     For a system including an elliptical mirror, a configuration may be adopted that utilizes an elliptical mirror system as disclosed in International Publication (WO) Nos. 2016/103484 or 2016/103489. The disclosures of WO Nos. 2016/103484 and 2016/103489 are incorporated in their entirety by reference herein. 
     Observation of the fundus over a wide field of view (FOV)  12 A is implemented by employing the wide-angle optical system  30 . The FOV  12 A refers to a range capable of being imaged by the imaging device  14 . The FOV  12 A may be expressed as a viewing angle. In the present exemplary embodiment the viewing angle may be defined in terms of an internal illumination angle and an external illumination angle. The external illumination angle is the angle of illumination by a light beam shone from the ophthalmic device  110  toward the examined eye  12 , and is an angle of illumination defined with respect to a pupil  27 . The internal illumination angle is the angle of illumination of a light beam shone onto the fundus, and is an angle of illumination defined with respect to an eyeball center O. A correspondence relationship exists between the external illumination angle and the internal illumination angle. For example, an external illumination angle of 120° is equivalent to an internal illumination angle of approximately 160°. The internal illumination angle in the present exemplary embodiment is 200°. 
     An angle of 200° for the internal illumination angle is an example of a “specific value” of technology disclosed herein. 
     SLO fundus images obtained by imaging at an imaging angle having an internal illumination angle of 160° or greater are referred to as UWF-SLO fundus images. UWF is an abbreviation of ultra-wide field. Obviously an SLO image that is not UWF can be acquired by imaging the fundus at an imaging angle that is an internal illumination angle of less than 160°. 
     An SLO system is realized by the control device  16 , the SLO unit  18 , and the imaging optical system  19  as illustrated in  FIG.  2   . The SLO system is provided with the wide-angle optical system  30 , enabling fundus imaging over the wide FOV  12 A. 
     The SLO unit  18  is provided with plural light sources such as, for example, a blue (B) light source  40 , a green (G) light source  42 , a red (R) light source  44 , an infrared (for example near infrared) (IR) light source  46 , and optical systems  48 ,  50 ,  52 ,  54 ,  56  to guide the light from the light sources  40 ,  42 ,  44 ,  46  onto a single optical path using reflection or transmission. The optical systems  48 ,  50 ,  56  are configured by mirrors, and the optical systems  52 ,  54  are configured by beam splitters. B light is reflected by the optical system  48 , is transmitted through the optical system  50 , and is reflected by the optical system  54 . G light is reflected by the optical systems  50 ,  54 , R light is transmitted through the optical systems  52 ,  54 , and IR light is reflected by the optical systems  56 ,  52 . The respective lights are thereby guided onto a single optical path. 
     The SLO unit  18  is configured so as to be capable of switching between the light source or the combination of light sources employed for emitting laser light of different wavelengths, such as a mode in which G light, R light and B light are emitted, a mode in which infrared light is emitted, etc. Although the example in  FIG.  2    includes four light sources, i.e. the B light source  40 , the G light source  42 , the R light source  44 , and the IR light source  46 , the technology disclosed herein is not limited thereto. For example, the SLO unit  18  may, furthermore, also include a white light source, in a configuration in which light is emitted in various modes, such as a mode in which white light is emitted alone. 
     Light introduced to the imaging optical system  19  from the SLO unit  18  is scanned in the X direction and the Y direction by the first optical scanner  22 . The scanning light passes through the wide-angle optical system  30  and the pupil  27  and is shone onto the posterior eye portion of the examined eye  12 . Reflected light that has been reflected by the fundus passes through the wide-angle optical system  30  and the first optical scanner  22  and is introduced into the SLO unit  18 . 
     The SLO unit  18  is provided with a beam splitter  64  that, from out of the light coming from the posterior eye portion (e.g. fundus) of the examined eye  12 , reflects the B light therein and transmits light other than B light therein, and a beam splitter  58  that, from out of the light transmitted by the beam splitter  64 , reflects the G light therein and transmits light other than G light therein. The SLO unit  18  is further provided with a beam splitter  60  that, from out of the light transmitted through the beam splitter  58 , reflects R light therein and transmits light other than R light therein. The SLO unit  18  is further provided with a beam splitter  62  that reflects IR light from out of the light transmitted through the beam splitter  60 . 
     The SLO unit  18  is provided with plural light detectors corresponding to the plural light sources. The SLO unit  18  includes a B light detector  70  for detecting B light reflected by the beam splitter  64 , and a G light detector  72  for detecting G light reflected by the beam splitter  58 . The SLO unit  18  also includes an R light detector  74  for detecting R light reflected by the beam splitter  60  and an IR light detector  76  for detecting IR light reflected by the beam splitter  62 . 
     Light that has passed through the wide-angle optical system  30  and the first optical scanner  22  and been introduced into the SLO unit  18  (i.e. reflected light that has been reflected by the fundus) is reflected by the beam splitter  64  and photo-detected by the B light detector  70  when B light, and is transmitted through the beam splitter  64  and reflected by the beam splitter  58  and photo-detected by the G light detector  72  when G light. When R light, the incident light is transmitted through the beam splitters  64 ,  58 , reflected by the beam splitter  60 , and photo-detected by the R light detector  74 . When IR light, the incident light is transmitted through the beam splitters  64 ,  58 ,  60 , reflected by the beam splitter  62 , and photo-detected by the IR light detector  76 . The image processing device  16 G that operates under the control of the CPU  16 A employs signals detected by the B light detector  70 , the G light detector  72 , the R light detector  74 , and the IR light detector  76  to generate UWF-SLO images. 
     The UWF-SLO image (sometimes referred to as a UWF fundus image or an original fundus image as described later) encompasses a UWF-SLO image (green fundus image) obtained by imaging the fundus in green, and a UWF-SLO image (red fundus image) obtained by imaging the fundus in red. The UWF-SLO image further encompasses a UWF-SLO image (blue fundus image) obtained by imaging the fundus in blue, and a UWF-SLO image (IR fundus image) obtained by imaging the fundus in IR. 
     The control device  16  also controls the light sources  40 ,  42 ,  44  so as to emit light at the same time. A green fundus image, a red fundus image, and a blue fundus image are obtained with mutually corresponding positions by imaging the fundus of the examined eye  12  at the same time with the B light, G light, and R light. An RGB color fundus image is obtained from the green fundus image, the red fundus image, and the blue fundus image. The control device  16  obtains a green fundus image and a red fundus image with mutually corresponding positions by controlling the light sources  42 ,  44  so as to emit light at the same time and by imaging the fundus of the examined eye  12  at the same time with the G light and R light. A RG color fundus image is obtained from the green fundus image and the red fundus image. 
     Specific examples of the UWF-SLO image include a blue fundus image, a green fundus image, a red fundus image, an IR fundus image, an RGB color fundus image, and an RG color fundus image. The image data for the respective UWF-SLO images are transmitted from the ophthalmic device  110  to the server  140  through the communication interface (I/F)  16 F, together with patient information input through the input/display device  16 E. The image data of the respective UWF-SLO images and the patient information are stored associated with each other in a storage device  254 . The patient information includes, for example, patient ID, name, age, visual acuity, right eye/left eye discriminator, and the like. The patient information is input by an operator through the input/display device  16 E. 
     An OCT system is realized by the control device  16 , the OCT unit  20 , and the imaging optical system  19  illustrated in  FIG.  2   . The OCT system is provided with the wide-angle optical system  30 . This enables fundus imaging to be performed over the wide FOV  12 A similarly to when imaging the SLO fundus images as described above. The OCT unit  20  includes a light source  20 A, a sensor (detector)  20 B, a first light coupler  20 C, a reference optical system  20 D, a collimator lens  20 E, and a second light coupler  20 F. 
     Light emitted from the light source  20 A is split by the first light coupler  20 C. After one part of the split light has been collimated by the collimator lens  20 E into parallel light to serve as measurement light, the parallel light is introduced into the imaging optical system  19 . The measurement light is scanned in the X direction and the Y direction by the second optical scanner  24 . The scanning light is shone onto the fundus through the wide-angle optical system  30  and the pupil  27 . Measurement light that has been reflected by the fundus passes through the wide-angle optical system  30  and the second optical scanner  24  so as to be introduced into the OCT unit  20 . The measurement light then passes through the collimator lens  20 E and the first light coupler  20 C before being incident to the second light coupler  20 F. 
     The other part of the light emitted from the light source  20 A and split by the first light coupler  20 C is introduced into the reference optical system  20 D as reference light, and is made incident to the second light coupler  20 F through the reference optical system  20 D. 
     The respective lights that are incident to the second light coupler  20 F, namely the measurement light reflected by the fundus and the reference light, interfere with each other in the second light coupler  20 F so as to generate interference light. The interference light is photo-detected by the sensor  20 B. The image processing device  16 G operating under the control of the CPU  16 A generates OCT images, such as tomographic images and en-face images, based on OCT data detected by the sensor  20 B. 
     OCT fundus images obtained by imaging at an imaging angle having an internal illumination angle of 160° or greater are referred to as UWF-OCT images. Obviously OCT data can be acquired at an imaging angle having an internal illumination angle of less than 160°. 
     The image data of the UWF-OCT images is transmitted, together with the patient information, from the ophthalmic device  110  to the server  140  though the communication interface (I/F)  16 F. The image data of the UWF-OCT images and the patient information are stored associated with each other in the storage device  254 . 
     Note that although in the present exemplary embodiment an example is given in which the light source  20 A is a swept-source OCT (SS-OCT), the light source  20 A may be configured from various types of OCT system, such as a spectral-domain OCT (SD-OCT) or a time-domain OCT (TD-OCT) system. 
     Next, explanation follows regarding the eye axial length measurement device  120 . The eye axial length measurement device  120  has two modes, i.e. a first mode and a second mode, for measuring eye axial length, this being the length of an examined eye  12  in an eye axial direction. In the first mode, light from a non-illustrated light source is guided into the examined eye  12 . Interference light between light reflected from the fundus and light reflected from the cornea is photo-detected, and the eye axial length is measured based on an interference signal representing the photo-detected interference light. The second mode is a mode to measure the eye axial length by employing non-illustrated ultrasound waves. 
     The eye axial length measurement device  120  transmits the eye axial length as measured using either the first mode or the second mode to the server  140 . The eye axial length may be measured using both the first mode and the second mode, and in such cases, an average of the eye axial lengths as measured using the two modes is transmitted to the server  140  as the eye axial length. The server  140  stores the eye axial length of the patients in association with patient ID. 
       FIG.  3    illustrates an RG color fundus image UWFGP, and a fundus image FCGQ (fundus camera image) obtained by imaging a fundus of an examined eye  12  using a non-illustrated fundus camera. The RG color fundus image UWFGP is an image obtained by imaging the fundus at an imaging angle having an external illumination angle of 100°. The fundus image FCGQ (fundus camera image) is an image obtained by imaging the fundus at an imaging angle having an external illumination angle of 35°. Thus, as illustrated in  FIG.  3   , the fundus image FCGQ (fundus camera image) is a fundus image of an area that is part of the fundus region corresponding to the RG color fundus image UWFGP. 
     A UWF-SLO image such as the RG color fundus image UWFGP illustrated in  FIG.  3    is an image having an area at the periphery of the image that is black due to light reflected from the fundus not arriving. Thus the UWF-SLO image includes a black area where light reflected from the fundus does not arrive (a background area, described later), and a part area of the fundus where light reflected from the fundus does arrive (a foreground area, described later). There are large differences between pixel values of each area at a boundary between the black area where light reflected from the fundus does not arrive and the part area of the fundus where light reflected from the fundus does arrive, and so the boundary is clear. 
     In contrast thereto, in the fundus image FCGQ (fundus camera image), a part area of the fundus where light reflected from the fundus does arrive (a foreground area, described later) is surrounded by flare, and a boundary between the foreground area needed for diagnosis and the background area not needed for diagnosis is not clear. Thus hitherto a specific mask image has been overlaid on the periphery of the foreground area, or pixel values of a specific area of the periphery of the foreground area have been overwritten with black pixel values. This makes a clear boundary between the black area where light reflected from the fundus does not arrive and the part area of the fundus where light reflected from the fundus does arrive. 
     Explanation follows regarding a configuration of an electrical system of the server  140 , with reference to  FIG.  4   . As illustrated in  FIG.  4   , the server  140  is provided with a computer body  252 . The computer body  252  includes a CPU  262 , RAM  266 , ROM  264 , and an input/output (I/O) port  268  connected together by a bus  270 . The storage device  254 , a display  256 , a mouse  255 M, a keyboard  255 K, and a communication interface (I/F)  258  are connected to the input/output (I/O) port  268 . The storage device  254  is, for example, configured by non-volatile memory. The input/output (I/O) port  268  is connected to the network  130  through the communication interface (I/F)  258 . The server  140  is thus capable of communicating with the ophthalmic device  110  and the viewer  150 . The storage device  254  is stored with an image processing program, described later. Note that the image processing program may be stored in the ROM  264 . 
     The image processing program is an example of a “program” of technology disclosed herein. The storage device  254  and the ROM  264  are examples of “memory” and “computer readable storage medium” of technology disclosed herein. The CPU  262  is an example of a “processor” of technology disclosed herein. 
     A processing section  208 , described later, of the server  140  (see also  FIG.  5   ) stores various data received from the ophthalmic device  110  in the storage device  254 . More specifically, the processing section  208  stores respective image data of the UWF-SLO images and image data of the UWF-OCT images in the storage device  254  associated with the patient information (such as the patient ID as described above). Moreover, in cases in which there is a pathological change in the examined eye of the patient and cases in which surgery has been performed on a pathological lesion, pathology information is input through the input/display device  16 E of the ophthalmic device  110  and transmitted to the server  140 . The pathology information is stored in the storage device  254  associated with the patient information. The pathology information includes information about the position of the pathological lesion, name of the pathological change, and name of the surgery and date/time of surgery etc. when surgery was performed on the pathological lesion. 
     The viewer  150  is provided with a computer equipped with a CPU, RAM, ROM and the like, and a display. The image processing program is installed in the ROM, and based on an instruction from a user, the computer controls the display so as to display the medical information such as fundus images acquired from the server  140 . 
     Next, description follows regarding various functions implemented by the CPU  262  of the server  140  executing the image processing program, with reference to  FIG.  5   . The image processing program includes a display control function, an image processing function (fundus image processing function, fundus vasculature analysis function), and a processing function. By the CPU  262  executing the image processing program including these various functions, the CPU  262  functions as a display control section  204 , an image processing section  206  (fundus image processing section  2060 , fundus vasculature analysis section  2062 ), and the processing section  208 , as illustrated in  FIG.  5   . 
     The fundus image processing section  2060  is an example of an “acquisition section” and a “generation section” of technology disclosed herein. 
     Detailed explanation now follows regarding image processing by the server  140 , with reference to  FIG.  6   . The image processing and an image processing method illustrated by the flowchart in  FIG.  6    is implemented by the CPU  262  of the server  140  executing the image processing program. 
     The image processing program starts when image data of a fundus image acquired by imaging the fundus of the examined eye  12  using the ophthalmic device  110  has been transmitted from the ophthalmic device  110  and received by the server  140 . 
     When the image processing program has started, at step  300  the fundus image processing section  2060  acquires the fundus image, and executes retinal blood vessel removal processing to remove the retinal blood vessels from the acquired fundus image, described in detail later (see  FIG.  7   ). A choroidal vascular image G 1  illustrated in  FIG.  10 A  is generated by the processing of step  300 . 
     The choroidal vascular image G 1  is an example of a “first fundus image” of technology disclosed herein. 
     At step  302  the fundus image processing section  2060  executes background infill processing to infill each of the pixels of a background area with pixel values of pixels of the image of a foreground area having the shortest distance to the respective pixel, described in detail later (see  FIG.  8   ). A background processing complete image G 2  illustrated in  FIG.  10 B  is generated by the background infill processing of step  302 . Note that in  FIG.  10 B  a range within the circular intermittent line is the fundus region. 
     The background infill processing of step  302  is an example of “background processing” of technology disclosed herein, the background processing complete image G 2  is an example of a “second fundus image” of technology disclosed herein. 
     Explanation follows regarding the foreground area and the background area. As illustrated in  FIG.  12   , a foreground area FG in the choroidal vascular image G 1  is determined by an arrival area of light from the fundus region of the examined eye  12 , and is a pixel area of brightness values based on the intensity of light reflected from the examined eye  12  (in other words, an area depicting the fundus, namely an area of a fundus image of the examined eye  12 ). In contrast thereto, a background area BG is an area outside the fundus region of the examined eye  12 , is a single color area, and is an image not based on light reflected from the examined eye  12 . More specifically, the background area BG is an area not depicting the fundus, namely is a part outside the fundus region of the examined eye  12 , and more precisely is a part including an area corresponding to pixels of the detectors  70 ,  72 ,  74 ,  76  where light reflected from the examined eye  12  does not arrive, a mask area, and parts of artefacts occurring due to vignetting, background reflections of the device, eyelid of the examined eye, and the like. Moreover, in cases in which the ophthalmic device  110  has a function to image an anterior eye portion area (cornea, iris, reticular formation, lens body, or the like), a specific area is the anterior eye portion area, and an anterior eye portion image of the examined eye is configured by the foreground area and the background area. Blood vessels appear in the reticular formation, and the technology disclosed herein enables the extraction of blood vessels of the reticular formation from the anterior eye portion image. 
     The fundus region of the examined eye  12  is an example of a “specific area of the examined eye” of technology disclosed herein. 
     At step  304  the fundus vasculature analysis section  2062  executes blood vessel emphasis processing on the background processing complete image G 2  so as to generate a blood vessel emphasis image G 3  illustrated in  FIG.  10 C . Contrast limited adaptive histogram equalization (CLAHE) may be employed as the blood vessel emphasis processing. Contrast limited adaptive histogram equalization (CLAHE) is a method of subdividing image data into plural areas, executing local histogram equalization on each of the subdivided areas, and adjusting the contrast by performing interpolation processing such as bilinear interpolation at boundaries between the respective areas. The blood vessel emphasis processing is not limited to contrast limited adaptive histogram equalization (CLAHE), and another method may be employed therefor. For example, unsharp mask processing (frequency processing), deconvolution processing, histogram equalization processing, haze removal processing, color correction processing, de-noise processing, or the like, or a combination processing thereof, may be employed. 
     At step  306 , the fundus image processing section  2060  generates a blood vessel extraction image (binarized image) G 4  illustrated in  FIG.  10 D  by extracting (specifically binarizing) blood vessels in the blood vessel emphasis image G 3 , described in detail later (see  FIG.  9   ). In such a binarized image, the pixels of the blood vessel area are white, and the pixels of other areas are black, and there is no discrimination between the fundus region and the background area. Thus a fundus region is detected in advance by image processing and stored. Then based on this stored fundus region, a line segment is displayed overlaid on the boundary of the fundus region of the generated blood vessel extraction image (binarized image) G 4 . By overlaying the line segment indicating this boundary a user is able to discriminate between the fundus region and the background area. 
     The blood vessel extraction image G 4  is an example of a “third fundus image” of technology disclosed herein. 
     Next with reference to  FIG.  7   , explanation follows regarding the retinal blood vessel removal processing of step  300  of  FIG.  6   . 
     At step  312  the fundus image processing section  2060  reads (acquires) image data of a first fundus image (red fundus image) from the image data of fundus images received from the ophthalmic device  110 . At step  314  the fundus image processing section  2060  reads (acquires) image data of a second fundus image (green fundus image) from the image data of fundus images received from the ophthalmic device  110 . 
     Explanation follows regarding information contained in the first fundus image (red fundus image) and the second fundus image (green fundus image). 
     The structure of an eye is one in which a vitreous body is covered by plural layers of differing structure. The plural layers include, from the vitreous body at the extreme inside to the outside, the retina, the choroid, and the sclera. R light passes through the retina and reaches the choroid. The first fundus image (red fundus image) therefore includes information relating to blood vessels present within the retina (retinal blood vessels) and information relating to blood vessels present within the choroid (choroidal blood vessels). In contrast thereto, G light only reaches as far as the retina. The second fundus image (green fundus image) accordingly only includes information relating to the blood vessels present within the retina (retinal blood vessels). 
     At step  316  the fundus image processing section  2060  performs black hat filter processing on the second fundus image (green fundus image) so as to extract the retinal blood vessels visible as thin black lines in the second fundus image (green fundus image). The black hat filter processing is filter processing to extract fine lines. 
     The black hat filter processing is processing to find a difference between image data of the second fundus image (green fundus image), and image data obtained by closing processing in which dilation processing is performed N times on the source image data followed by performing erosion processing N times (wherein N is an integer of 1 or more). In a fundus image the retinal blood vessels are imaged blacker than the periphery of the blood vessels because illumination light (not only G light but also R light or IR light) is absorbed by the retinal blood vessels. Thus the retinal blood vessels can be extracted by performing black hat filter processing on the fundus image. 
     At step  318  the fundus image processing section  2060  removes the retinal blood vessels extracted at step  316  from the first fundus image (red fundus image) by performing in-painting processing thereon. More specifically, the retinal blood vessels are made to no longer stand out in the first fundus image (red fundus image). Even more precisely, the fundus image processing section  2060  identifies, in the first fundus image (red fundus image), each of the positions of the retinal blood vessels extracted from the second fundus image (green fundus image). The fundus image processing section  2060  then performs processing such that a difference between pixel values of pixels in the first fundus image (red fundus image) at the identified positions, and an average value of pixels at the periphery of these pixels, is within a specific range (for example, zero). The method of removing retinal blood vessels is not limited to the example described above, and general in-painting processing may be employed therefor. 
     The retinal blood vessels do not stand out in the first fundus image (red fundus image) where both the retinal blood vessels and the choroidal blood vessels are present, and the fundus image processing section  2060  is accordingly able to make the choroidal blood vessels stand out comparatively more in the first fundus image (red fundus image) as a result of the above. As illustrated in  FIG.  10 A , the choroidal vascular image G 1  is accordingly obtained in which only the choroidal blood vessels are visible as fundus blood vessels. Note that in  FIG.  10 A , the white line shapes are the choroidal blood vessels, and the white circular portion corresponds to the optic nerve head ONH, and the black circular portion corresponds to the macular M. 
     When the processing of step  318  has finished the retinal blood vessel removal processing of step  300  of  FIG.  5    is ended, and the image processing transitions to step  302  of  FIG.  6   . 
     Next, with reference to  FIG.  8    explanation follows to the background infill processing of step  302  of  FIG.  6   . 
     At step  332 , as illustrated in  FIG.  12   , the fundus image processing section  2060  extracts the foreground area FG, the background area BG, and a boundary BD between the foreground area FG and the background area BG in the choroidal vascular image G 1 . 
     More specifically, the fundus image processing section  2060  extracts as the background area BG parts where the pixel value is zero, extracts as the foreground area FG parts where the pixel value is non-zero, and extracts as the boundary BD boundary sections between the extracted background area BG and the extracted foreground area FG. 
     As described above, in the background area BG the light from the examined eye  12  does not arrive, resulting in a part where the pixel values are zero. However, sometimes areas such as artefacts due to vignetting, background reflections of the device, eyelid of the examined eye, and the like are recognized as background area. Moreover, there are also cases in which pixel values of pixels in the area of a detector where light reflected from the examined eye  12  does not enter are not zero due to the sensitivity of the detectors  70 ,  72 ,  74 ,  76 . The fundus image processing section  2060  may accordingly extract as the background area BG parts having a pixel value greater than a specific value greater than zero. 
     However, areas where light from the examined eye  12  arrives in the detection fields of the detectors  70 ,  72 ,  74 ,  76  are predetermined as paths for light of the optical elements of the imaging optical system  19 . The areas where light arrives from the examined eye  12  are the foreground area FG, the areas where light does not arrive from the examined eye  12  are the background area BG, and a boundary section between the background area BG and the foreground area FG may be extracted as the BD boundary as described above. 
     At step  334  the fundus image processing section  2060  sets a variable g to identify each of the pixels of the image in the background area BG to zero, and at step  336  the fundus image processing section  2060  increments variable g by one. 
     At step  338  the fundus image processing section  2060  detects a nearest pixel h of the foreground area FG having a closest distance to a pixel g of the background area BG image identified by variable g using relationships between the position of the pixel g and the positions of each of the pixels of the foreground area FG image. The fundus image processing section  2060  may, for example, calculate a distance between the position of the pixel g and the positions of each of the pixels of the foreground area FG image, and detect the pixel having the shortest distance as the pixel h. However, in the present exemplary embodiment the position of the pixel h is predetermined from the geometrical relationship between the position of the pixel g and the positions of each of the pixels of the foreground area FG image. 
     At step  340  the fundus image processing section  2060  sets a pixel value Vh different than the pixel value Vg for the pixel value Vg of the pixel g, for example, sets the pixel value Vh of the pixel h detected at step  338 . 
     At step  342  the fundus image processing section  2060  determines whether or not a pixel value different than the pixel value has been set for the pixel values of all the pixels in the image of the background area BG by determining whether or not the variable g is equal to a total number G of the pixels in the image of the background area BG. The background infill processing returns to step  336  in cases in which the variable g is determined not to be equal to the total number G, and the fundus image processing section  2060  executes the above processing (from step  336  to step  342 ). 
     When determined that the variable g is equal to the total number G at step  342 , this means that the pixel values of all of the pixels in the background area BG image have been converted into pixel values different than their respective pixel values, and so the background infill processing is ended. 
     The background processing complete image G 2  illustrated in  FIG.  10 B  is generated by the background infill processing of step  302  (steps  332  to  342  of  FIG.  8   ). 
     Note that, as described in detail later, when calculating a threshold value for binarizing the pixel values of the pixels in the foreground area FG image, the fundus image processing section  2060  extracts a specific number of pixels centered on the respective pixel and employs an average of the pixel values for these extracted pixels. Thus it suffices to identify just the pixels that may be extracted to calculate the threshold value from out of the pixels of the background area BG image as the variable g. In such cases the total number G may be the total number of pixels that may be extracted when calculating the threshold value. In such cases the pixels identified by the variable g are the pixels surrounding the foreground area FG from out of the pixels of the background area BG image. Note that in such cases, moreover, a pixel may be identified by the variable g that is any one or more pixel from out of the pixels surrounding the foreground area FG. 
     In the background infill processing of step  302  (steps  332  to  342  of  FIG.  8   ), pixel values of each of the pixels of the background area BG are sequentially converted to the pixel value of the nearest foreground area FG pixel having the closest distance to that respective pixel. The technology disclosed herein is not limited thereto. 
     MODIFIED EXAMPLES OF BACKGROUND INFILL PROCESSING OF STEP  302   
     Next, description follows regarding modified examples of the background infill processing of step  302 , with reference to  FIG.  13 A  to  FIG.  13 G . 
     Modified Example 1 of Background Infill Processing 
     As illustrated in  FIG.  13 A , for example, the fundus image processing section  2060  converts the pixel value of each of the pixels of the background area BG on a line L passing through a center of the choroidal vascular image G 1  to the pixel value of the nearest foreground area FG pixel closest to each of the respective pixels. More specifically, the fundus image processing section  2060  extracts the line L from a pixel LU at one corner of the choroidal vascular image G 1  and passing through the center thereof and passing through a pixel RD at another corner on the opposite side of the center. The fundus image processing section  2060  converts the pixel values of each of the pixels on the line L from the pixel LU at the one corner of the background area BG to the pixel of the background area BG adjacent to a nearest foreground area FG pixel P having the closest distance to the pixel LU, to a pixel value gp of the pixel P. The fundus image processing section  2060  converts the pixel values of each of the pixels on the line L from the pixel RD at the other corner of the background area BG to the pixel of the background area BG adjacent to a nearest foreground area FG pixel Q having the closest distance to the pixel RD, to a pixel value gq of the pixel Q. The fundus image processing section  2060  executes such pixel value conversion for all lines passing through the center of the choroidal vascular image G 1 . 
     Modified Example 2 of Background Infill Processing 
       FIG.  13 B  schematically illustrates a choroidal vascular image G 1  including a center position CP of the foreground area FG, the foreground area FG, and the background area BG surrounding the foreground area FG. More specifically the center position CP is indicated by the * mark. Light from the examined eye  12  arrives at each of the pixels of the foreground area FG image, and so they have pixel values according to the intensity of the arriving light, however, in  FIG.  13 B  the pixel values are schematically illustrated as smoothly increasing in the foreground area FG from the center position CP toward the outside. The pixel values of the background area BG are illustrated as being zero. 
     In the Modified Example 2 of the background infill processing, as illustrated in  FIG.  13 C , the fundus image processing section  2060  converts the pixel values of each of the pixels of the background area BG image into a value gs (=0+α) that is greater than the respective pixel values by a specific value α. 
     Modified Example 3 of Background Infill Processing 
     At step  302  the pixels of the background area BG image are converted to pixel values of the nearest foreground area FG pixel having the closest distance to the respective pixel. In contrast thereto, in the Modified Example 3 of the background infill processing, as illustrated in  FIG.  13 D , the fundus image processing section  2060  converts the pixels of the background area BG image to a value gu (=gt−α) smaller than a pixel value gt of the nearest foreground area FG pixel by a specific value β. 
     Modified Example 4 of Background Infill Processing 
     In a Modified Example 4 of the background infill processing, as illustrated in  FIG.  13 E , the fundus image processing section  2060  converts the pixel value of each of the pixels of the background area BG to an average value gm of the pixel values for all the pixels of the foreground area FG. 
     Modified Example 5 of Background Infill Processing 
     In a Modified Example 5 of the background infill processing, as illustrated in  FIG.  13 F , the fundus image processing section  2060  detects changes to the pixel values from the center pixel CP to an edge portion of the foreground area FG. The fundus image processing section  2060  then applies a change in pixel values in the background area BG that is similar to the change in the pixel values in the foreground area FG. Namely, pixel values from the center pixel CP to the edge portion of the foreground area FG are exchanged for the pixel values from the innermost perimeter of the background area BG to the outermost perimeter thereof. 
     In the example of the fundus image schematically illustrated in  FIG.  13 F , the pixel values smoothly increase in the foreground area FG from the center position CP toward the outside. In the Modified Example 5 the fundus image processing section  2060  converts each of the pixels of the background area BG image to values that are gradually greater the longer the distance is from the center CP of the foreground area FG. 
     Modified Example 6 of Background Infill Processing 
     In the Modified Example 6 of the background infill processing, as illustrated in  FIG.  13 G , the fundus image processing section  2060  detects changes in pixel values from the center pixel CP to the edge portion of the foreground area FG. The fundus image processing section  2060  then applies changes in the background area BG that are the reverse of changes to the pixel values in the foreground area FG. Namely, pixel values from the edge portion of the foreground area FG to the center pixel CP are substituted for the pixel values from the innermost perimeter of the background area BG to the outermost perimeter thereof. 
     In the example of the fundus image schematically illustrated in  FIG.  13 G , the pixel values smoothly increase in the foreground area FG from the center position CP toward the outside. In the Modified Example 6 the fundus image processing section  2060  converts each of the pixels of the background area BG image to values that gradually decrease the longer the distance is from the center CP of the foreground area FG. 
     Moreover, the technology disclosed herein includes modifications to the content of the processing for Modified Example 1 to Modified Example 6 within a range not departing from the spirit of technology disclosed herein. 
     When the background infill processing has finished, the image processing proceeds to step  304  of  FIG.  6   , and at step  304  the blood vessel emphasis processing (for example CLAHE or the like) is executed as described above so as to generate the blood vessel emphasis image G 3  illustrated in  FIG.  10 C . 
     The blood vessel emphasis image G 3  is an example of an “image resulting from emphasizing blood vessels” of technology disclosed herein. 
     When the blood vessel emphasis processing of step  304  has finished the image processing proceeds to step  306  of  FIG.  6   . 
     Next, description follows regarding processing to extract blood vessels at step  306  of  FIG.  6   , with reference to  FIG.  9   . 
     At step  352  the fundus image processing section  2060  sets a variable m to identify each of the pixels of the foreground area FG image in the blood vessel emphasis image G 3  to zero, and at step  354  the fundus image processing section  2060  increments the variable m by one. 
     At step  356  the fundus image processing section  2060  extracts a specific number of pixels centered on a pixel m of the foreground area FG identified by variable m. For example, the specific number of pixels extracted are four pixels adjacent above, below, to the left, and to the right of the pixel m, or a total of eight pixels adjacent thereto above, below, to the left, and to the right, and in diagonal directions. There is no limit to the adjacent eight pixels, and pixels in the vicinity may be extracted from a wider range. 
     At step  358  the fundus image processing section  2060  computes an average value H of the pixel values for the specific number of pixels extracted at step  356 . At step  360  the fundus image processing section  2060  sets the average value H as a threshold value Vm for pixel m. At step  362  the fundus image processing section  2060  binarizes the pixel value of pixel m using the threshold value Vm (=H). 
     At step  364  the fundus image processing section  2060  determines whether or not the variable m is equal to the total pixel number M of the foreground area FG image. Not all of the pixels of the foreground area FG image have been binarized with the above threshold value unless the variable m is determined to be equal to the total pixel number M, and so the processing to extract the blood vessels returns to step  354 , and the fundus image processing section  2060  executes the above processing (steps  354  to  364 ). 
     In cases in which the variable m is equal to the total pixel number M, the pixel values of all of the pixels in the foreground area FG image have been binarized, and so at step  366  the fundus image processing section  2060  sets the pixel values of the background area BG in the blood vessel emphasis image G 3  to the same pixel value as their original respective pixel values. The blood vessel extraction image G 4  illustrated in  FIG.  10 D  is generated by the processing of step  366 . 
     The pixel values of the background area BG in the blood vessel emphasis image G 3  are an example of “second pixel values” of technology disclosed herein, and the original pixel values are an example of “first pixel values” and “third pixel values” of technology disclosed herein. 
     Note that in the technology disclosed herein there is no limitation to setting the pixel values of the background area BG in the blood vessel emphasis image G 3  to the same pixel value as their original respective pixel values, and the pixel values of the background area BG in the blood vessel emphasis image G 3  may be substituted with a pixel value that is different from the original pixel value. 
     After the blood vessel emphasis processing of step  304 , the processing to extract blood vessels of step  306  is executed. The image subjected to the blood vessels extraction processing is accordingly the blood vessel emphasis image G 3 . However, the technology disclosed herein is no limited thereto. For example, after the background infill processing of step  302  the blood vessel emphasis processing of step  304  may be omitted, and the processing to extract blood vessels of step  306  may be executed. In such cases the image subjected to the blood vessels extraction processing is the background processing complete image G 2 . 
     At step  306  the fundus vasculature analysis section  2062  may further execute choroid analysis processing. As the choroid analysis processing, the fundus image processing section  2060  executes, for example, vortex vein position detection processing and processing to analyze asymmetry in running directions of the choroidal vasculature. 
     The choroid analysis processing is an example of “analysis processing” of technology disclosed herein. 
     The execution timing of the choroid analysis processing may, for example, be between the processing of step  364  and the processing of step  366 , or may be after the processing of step  366 . 
     In cases in which the choroid analysis processing is executed between the processing of step  364  and the processing of step  366 , the image subjected to the choroid analysis processing is an image prior to setting the pixel values of the background area in the blood vessel emphasis image G 3  to their original pixel values. Note that in cases in which the blood vessel emphasis processing of step  304  is omitted, the choroid analysis processing is executed on the background processing complete image G 2 . 
     In contrast thereto, in cases in which the choroid analysis processing is executed after the processing of step  366 , the image subjected to the choroid analysis processing is the blood vessel extraction image G 4 . The subject image is an image in which only the choroidal blood vessels have been made visible. 
     The vortex veins are flow paths of blood flow flowing into the choroid, and there are from four to six vortex veins present toward the posterior pole of an equatorial portion of the eyeball. The vortex vein positions are detected based on the running direction of the choroidal blood vessels obtained by analyzing the subjected image. 
     The fundus image analysis section  2060  sets a movement direction of each of the choroidal blood vessels (blood vessel running direction) in the subjected image. More specifically, first the fundus image analysis section  2060  executes the following processing on each pixel in the subjected image. Namely, for each pixel the fundus image analysis section  2060  sets an area (cell) having the respective pixel at the center, and creates a histogram of brightness gradient direction at each of the pixels in the cells. Next, the fundus image analysis section  2060  takes the gradient direction having the lowest count in the histogram of the cells as the movement direction for the pixels in each of the cells. This gradient direction corresponds to the blood vessel running direction. Note that the reason for taking the gradient direction having the lowest count as the blood vessel running direction is as follows. The brightness gradient is small in the blood vessel running direction, whereas the brightness gradient is large in other directions (for example, there is a large difference in brightness between blood vessel and non-blood vessel tissue). Thus creating a histogram of brightness gradient for each of the pixels results in a small count in the blood vessel running direction. The blood vessel running direction at each of the pixels in the subjected image is set by the processing described above. 
     The fundus image processing section  2060  sets an initial position for M (natural number)×N (natural number) (=L) individual hypothetical particles. More specifically, the fundus image processing section  2060  sets a total of L initial positions at uniform spacings on the subjected image, with M positions in the vertical direction, and N positions in the horizontal direction. 
     The fundus image processing section  2060  estimates the position of the vortex veins. More specifically, the fundus image analysis section  2060  performs the following processing for each of the L positions. Namely, the fundus image analysis section  2060  acquires a blood vessel running direction at an initial position (one of the L positions), moves the hypothetical particle by a specific distance along the acquired blood vessel running direction, then re-acquires the blood vessel running direction at the moved-to position, before then moving the hypothetical particle by the specific distance along this acquired blood vessel running direction. This moving by the specific distance along the blood vessel running direction is repeated for a pre-set number of movement times. The above processing is executed for all the L positions. Points where a fixed number of the hypothetical particles or greater have congregated at this point in time are taken as the position of a vortex vein. 
     The positional information of the vortex veins (number of vortex veins, coordinates on the subjected image, etc.) are stored in the storage device  254 . A method disclosed in Japanese Patent Application No. 2018-080273 and a method disclosed in WO No. PCT/JP2019/016652 may be employed as the method for detecting vortex veins. The disclosures of Patent Application No. 2018-080273 filed in Japan on Apr. 18, 2018 and WO No. PCT/JP2019/016652 filed internationally on Apr. 18, 2019 are incorporated in their entirety in the present specification by reference herein. 
     The processing section  208  stores at least the choroidal vascular image G 1  and the blood vessel extraction image G 4 , the choroid analysis data (respective data indicating vortex vein positions and the asymmetry of the running direction of the choroidal blood vessels and the like), together with patient information (patient ID, name, age, visual acuity, right eye/left eye discriminator, eye axial length, etc.), in the storage device  254  (see  FIG.  4   ). The processing section  208  may also save the RG color fundus image UWFGP (original fundus image) and an image of a processing process such as the background processing complete image G 2  and the blood vessel emphasis image G 3 . 
     Note that in the present exemplary embodiment the processing section  208  stores the RG color fundus image UWFGP (original fundus image), the choroidal vascular image G 1 , the background processing complete image G 2 , the blood vessel emphasis image G 3 , the blood vessel extraction image G 4 , and choroid analysis data, together with patient information, in the storage device  254  (see  FIG.  4   ). 
     Description follows regarding the display on the viewer  150  of the fundus image captured by the ophthalmic device  110  and a fundus camera and the fundus image from the image processing by the image processing program of  FIG.  6   . 
     When an ophthalmologist is examining the examined eye  12  of a patient, the patient ID is input to the viewer  150 . The viewer  150  input with the patient ID instructs the server  140  to transmit image data of each image (UWFGP, G 1  to G 4 , etc.) together with patient information corresponding to the patient ID. The viewer  150  that has received the image data of each image (UWFGP, G 1  to G 4  etc.), together with the patient information, generates an examination screen  400 A of the examined eye  12  of the patient, as illustrated in  FIG.  14   , and displays the examination screen  400 A on the display of the viewer  150 . 
       FIG.  14    illustrates the examination screen  400 A of the viewer  150 . The examination screen  400 A as illustrated in  FIG.  14    includes an information display area  402  and an image display area  404 A. 
     The information display area  402  includes a patient ID display field  4021  and a patient name display field  4022 . The information display area  402  also includes an age display field  4023  and a visual acuity display field  4024 . The information display area  402  also includes a right eye/left eye information display field  4025  and an eye axial length display field  4026 . The information display area  402  also includes a switch screen icon  4027 . The viewer  150  displays information corresponding to each of the display fields (from  4021  to  4026 ) based on the patient information received. 
     The image display area  404 A includes an original fundus image display field  4041 A, a blood vessel extraction image display field  4042 A, and a text display field  4043 . The viewer  150  displays images (RG color fundus image UWFGP (original fundus image), blood vessel extraction image G 4 ) corresponding to each display field ( 4041 A,  4042 A) based on the received image data. An imaging date (YYYY/MM/DD) when the images being displayed were acquired is also displayed in the image display area  404 A. 
     An examination memo input by a user (ophthalmologist) is displayed in the text display field  4043 . In addition, for example, text for analyzing the image being displayed such as “A choroidal vascular image is being displayed in the left side area. An image of extracted choroidal blood vessels is being displayed in the right side area”, may also be displayed. 
     When the switch screen icon  4027  is operated in a state in which the original fundus image UWFGP and the blood vessel extraction image G 4  are being displayed in the image display area  404 A, the examination screen  400 A is changed to an examination screen  400 B illustrated in  FIG.  15   . The content is similar in the examination screen  400 A and the examination screen  400 B, and so the same reference numerals are appended to parts with similar content, explanation thereof will be omitted, and explanation will be of the differing parts of the content alone. 
     As illustrated in  FIG.  15   , the examination screen  400 B includes a combined image display field  4041 B and a separate blood vessel extraction image display field  4042 B instead of the original fundus image display field  4041 A and the blood vessel extraction image display field  4042 A of  FIG.  14   . A combined image G 14  is displayed in the combined image display field  4041 B. A processing image G 15  is displayed in the blood vessel extraction image display field  4042 B. 
     The combined image G 14  is an image in which the blood vessel extraction image G 4  is overlaid on the RG color fundus image UWFGP (original fundus image), as illustrated in  FIG.  16   . A user is easily able to ascertain a state of the choroidal blood vessels on the RG color fundus image UWFGP (original fundus image) using the combined image G 14 . 
     The processing image G 15  is an image in which the boundary BG is displayed overlaid on the blood vessel extraction image G 4  by appending a frame (boundary line) indicating the boundary BD between the background area BG and the foreground area FG to the blood vessel extraction image G 4 . A user is able to easily discriminate between the fundus region and a background area using the processing image G 15  in which the boundary BD is displayed overlaid. 
     Note that the blood vessel extraction image G 4  in the blood vessel extraction image display field  4042 A of  FIG.  14   , and the processing image G 15  in the separate blood vessel extraction image display field  4042 B of  FIG.  15    may have further emphasis of the choroidal blood vessels by applying a frame f to the blood vessel bt as illustrated in  FIG.  17   . 
     Hitherto a blood vessel emphasis image G 7  as illustrated in  FIG.  11 B  was obtained from the choroidal vascular image G 1  illustrated in  FIG.  11 A , and each of the pixels of the foreground area image of the blood vessel emphasis image G 7  binarized using an average value of pixel values for a specific number of pixels centered on each respective pixel as the threshold value. The threshold value in such cases is a low value in a peripheral portion of the foreground area image as illustrated in  FIG.  11 C . This is because at the outside of pixels of the peripheral portion of the foreground area image there are pixels present in the background area image having pixel values of zero, and the zero values lower the value of the average value. This means that the threshold value for the peripheral portion of the blood vessel emphasis image G 7  is set low due to being influenced by the pixel values of the background area image (=0), and a frame (white portion) occurs in a peripheral portion of the foreground area in a blood vessel extraction image G 9  obtained by such binarization, as illustrated in  FIG.  11 D . Thus there is a concern that the frame occurring at the peripheral portion of the foreground area FB of blood vessel extraction image G 9  might be mistakenly extracted as a blood vessel, and the user (ophthalmologist) might be caused to recognize blood vessels as being present in a portion of the foreground area FB where there are not actually blood vessels present. 
     To address this issue, in the present exemplary embodiment the background processing complete image G 2  (see  FIG.  10 B ) is generated in which pixel values are infilled based on the background area BG image and the foreground area FG image of the choroidal vascular image G 1  illustrated in  FIG.  10 A . Binarization from the background processing complete image G 2  is via the blood vessel emphasis processing, and so a frame (white portion) does not occur in the peripheral portion of the blood vessel extraction image G 4 , as illustrated in  FIG.  10 D . The present exemplary embodiment is accordingly able to prevent the boundary between the foreground area and the background area from affecting the results of analyzing the fundus image. The present exemplary embodiment is accordingly able to prevent the user (ophthalmologist) from recognizing choroidal blood vessels as being present in portions where blood vessel are not actually present in the blood vessel extraction image G 4  (namely in the background area, the outermost peripheral portion of the foreground area, and the like). 
     Binarization of the blood vessel emphasis image G 3  described above is performed for each of the pixels of the foreground area FG using the average value H of pixel values of the specific number of pixels centered on the respective pixel as the threshold value, however the technology disclosed herein is not limited thereto, and the following modified examples of binarization processing may be employed. 
     Modified Example 1 of Binarization Processing 
     By blurring the blood vessel emphasis image G 3  (for example by performing processing to remove low frequency components from the image), the fundus image processing section  2060  generates a blurred image Gb illustrated in  FIG.  18    and then uses pixel values of each of the pixels of the blurred image Gb as the threshold value for each of the pixels of the blood vessel emphasis image G 3  corresponding to the positions of each of the pixels of the blurred image Gb. An example of processing to blur the blood vessel emphasis image G 3  is convolution computation using a point spread function (PSF) filter. Filtering processing using a Gaussian filter, a low pass filter, and the like may also be used as the processing to blur the image. 
     Modified Example 2 of Binarization Processing 
     The fundus image processing section  2060  may employ a predetermined value as the threshold value for binarization processing. Note that the predetermined value is, for example, an average value of all the pixel values of the foreground area FG. 
     Modified Example 3 of Binarization Processing 
     A Modified Example 3 of binarization processing is an example in which step  302  of  FIG.  6    (steps  332  to  342 ) is omitted. In such cases the content of processing for step  356  of  FIG.  9    is as follows. 
     First the fundus image processing section  2060  extracts a specific number of pixels centered on a pixel m. 
     The fundus image processing section  2060  determines whether or not there is a pixel of the background area BG contained in the specific number of pixels extracted. 
     In cases in which determination is that there is a pixel of the background area BG contained in the specific number of pixels extracted, the fundus image processing section  2060  replaces the pixel of the background area BG with the following pixel, and sets pixels of the foreground area including the replacement pixel and the pixels initially extracted as the specific number of pixels centered on the pixel m. The pixel to replace the background area BG pixel is a pixel of the foreground area FG adjacent to the pixels of the foreground area FG contained in the specific number of pixels (a pixel of the foreground area image positioned at only a specific distance from each of the pixels). 
     However, when determined that there is no background area BG pixel contained in the specific number of pixels extracted, the fundus image processing section  2060  does not perform the pixel replacement described above, and sets the pixels initially extracted as the specific number of pixels centered on the pixel m. 
     In other words, in the Modified Example 3 of binarization processing the following image processing step is executed by the fundus image processing section  2060 . Acquisition is performed to acquire a fundus image including a foreground area that is an image portion of the examined eye and a background area to the image portion of the examined eye. Next, binarization is performed on the pixel values of each of the pixels of the foreground area image based on only the pixel values of pixels of the foreground area image positioned a specific distance from the respective pixel. 
     Other Modified Examples 
     In the exemplary embodiment described above, the pixel values of the background area are a value of black, i.e. zero, in the detectors  70 ,  72 ,  74 ,  76 , however technology disclosed herein is not limited thereto, and a configuration may be employed in which the pixel values of the background area are a value of white. 
     Although a fundus image (UWF-SLO image (for example, UWFGP (see  FIG.  3   )) is acquired by the ophthalmic device  110 , a fundus image (FCGQ (see  FIG.  3   )) may be acquired using a fundus camera. In cases in which a fundus image FCGQ is acquired using a fundus camera, the R component, the G component, and the B component of RGB space is employed in the image processing described above. Note that the a* component of L*a*b* space may be employed, or another component of another space may be employed. 
     In the technology disclosed herein, the image processing illustrated in  FIG.  6    is not limited to being executed by the server  140 , and may be executed by a separate computer connected to the ophthalmic device  110 , the viewer  150 , or the network  130 . 
     Moreover, although the ophthalmic device  110  includes functionality to image a region having an internal illumination angle of 200° with respect to a position of the eyeball center O of the examined eye  12  (an external illumination angle of 167° with respect to the pupil of the eyeball of the examined eye  12 ), there is no limitation to this angle. The internal illumination angle may be 200° or greater (an external illumination angle of from 167° to 180°). 
     Furthermore, a specification may be employed in which the internal illumination angle is less than 200° (the external illumination angle is less than 167°). The following angles of view may, for example, be employed: an internal illumination angle of about 180° (an external illumination angle of about 140°), an internal illumination angle of about 156° (an external illumination angle of about 120°), an internal illumination angle of about 144° (an external illumination angle of about 110°). These numerical values are merely examples. 
     Although explanation has been given in the examples described above regarding examples in which a computer is employed to implement image processing using a software configuration, the technology disclosed herein is not limited thereto. For example, instead of the image processing being executed by a software configuration employing a computer, the image processing may be executed solely by a hardware configuration such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). Alternatively, a configuration may be adopted in which some processing out of the image processing is executed by a software configuration, and the remaining processing is executed by a hardware configuration. 
     Such technology disclosed herein encompasses cases in which the image processing is implemented by a software configuration utilizing a computer, and also image processing implemented by a configuration that is not a software configuration utilizing a computer, and encompasses the following first technology and second technology. 
     First Technology 
     An image processing device including: 
     an acquisition section configured to acquire a first fundus image of an examined eye including a foreground area and a background area other than the foreground area; and 
     a generation section configured to generate a second fundus image by the processor performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
     The fundus image processing section  2060  of the exemplary embodiment described above is an example of an “acquisition section” and a “generation section” of the first technology above. 
     Second Technology 
     An image processing method including: 
     an acquisition section acquiring a first fundus image of an examined eye including a foreground area and a background area other than the foreground area; and 
     a generation section generating a second fundus image by the processor performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
     The following third technology is proposed from the content disclosed above. 
     Third Technology 
     A computer program product for image processing, the computer program product including a computer-readable storage medium that is not itself a transitory signal, with a program stored on the computer-readable storage medium, the program causing a computer to execute processing including: 
     acquiring a first fundus image of an examined eye including a foreground area and a background area other than the foreground area; and 
     generating a second fundus image by performing background processing to replace a first pixel value of a pixel configuring the background area with a second pixel value different from the first pixel value. 
     It must be understood that the image processing described above is merely an example thereof. Obviously redundant steps may be omitted, new steps may be added, and the processing sequence may be swapped around within a range not departing from the spirit of technology disclosed herein. 
     All publications, patent applications and technical standards mentioned in the present specification are incorporated by reference in the present specification to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.