Patent Publication Number: US-2022233245-A1

Title: Medical control device and medical observation system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Application No. 2021-011862, filed on Jan. 28, 2021, the contents of which are incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to a medical control device and a medical observation system. 
     A medical observation system has been known which is used for eye surgery such as cataract surgery (see, for example, WO 2017/065018 A). 
     According to a medical observation system described in WO 2017/065018 A, a captured image obtained by capturing an image of a subject eye with an imaging device is displayed in a display device. Then, a doctor performs surgery while confirming the captured image displayed in the display device. 
     SUMMARY 
     In the meantime, examples of a situation where a center position of the subject eye in the screen of the display device moves include: a first case where pressure is applied to the subject eye by the doctor performing a specific procedure, and a second case where a patient changes his/her posture or the patient moves his/her line of sight. 
     Here, in the first case, when the specific procedure is finished, no more pressure is applied to the subject eye and the center position of the subject eye in the screen returns to the original position. Thus, in the first case, the doctor operates the medical observation system to change the imaging field of view, which eliminates the need to change the center position of the subject eye in the screen. On the other hand, in the second case, the doctor operates the medical observation system to change the imaging field of view, which involves complicated work of changing the center position of the subject eye in the screen to an appropriate position. 
     There is a need for a technique that eliminates the need for the complicated work to improve convenience. 
     According to one aspect of the present disclosure, there is provided a medical control device including: determination circuitry configured to determine whether or not a specific surgical tool is included in a captured image based on an image signal generated by an imaging device configured to capture an image of a subject eye; image generation circuitry configured to generate an image for display based on the image signal; and a state controller configured to control, in a case where the determination circuitry determines that the specific surgical tool is not included in the captured image, operation of the image generation circuitry or an imaging field of view by the imaging device so as to maintain a state of the subject eye in the image for display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for explanation of a configuration of a medical observation system according to an embodiment; 
         FIG. 2  is a diagram for explanation of a configuration of a medical observation system according to an embodiment; 
         FIG. 3A  is a diagram for explanation of a surgical tool used for cataract surgery; 
         FIG. 3B  is a diagram for explanation of a surgical tool used for cataract surgery; 
         FIG. 3C  is a diagram for explanation of a surgical tool used for cataract surgery; 
         FIG. 3D  is a diagram for explanation of a surgical tool used for cataract surgery; 
         FIG. 3E  is a diagram for explanation of a surgical tool used for cataract surgery; 
         FIG. 4  is a flowchart depicting operation of a control device; 
         FIG. 5  is a diagram for explanation of a change in imaging field of view in a case where a specific surgical tool is included in a captured image; 
         FIG. 6  is a diagram for explanation of a change in imaging field of view in a case where no specific surgical tool is included in a captured image; and 
         FIG. 7  is a diagram for explanation of Step S 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, modes for carrying out the present disclosure (embodiments below) will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Further, the same parts are denoted by the same reference signs when the drawings are described. 
     Schematic Configuration of Medical Observation System 
       FIGS. 1 and 2  are diagrams for explanation of a configuration of a medical observation system  1  according to an embodiment. Specifically,  FIG. 1  is a diagram illustrating an external configuration of the medical observation system  1 .  FIG. 2  is a block diagram illustrating a configuration of the medical observation system  1 . 
     The medical observation system  1  is a system used for surgery on an eye of a patient who lies on a patient bed BD ( FIG. 1 ), the eye being hereinafter referred to as a “subject eye”. As illustrated in  FIG. 1  or  FIG. 2 , the medical observation system  1  includes a surgical microscope  2 , a display device  3 , an input device  4 , and a control device  5 . 
     The surgical microscope  2  captures an image of the subject eye under the control of the control device  5 . As illustrated in  FIG. 1  or  FIG. 2 , the surgical microscope  2  includes a light source device  21  ( FIG. 2 ), a microscope unit  22 , a base unit  23  ( FIG. 1 ), a supporting unit  24  ( FIG. 1 ), and a driving unit  25  ( FIG. 2 ). 
     The light source device  21  supplies, under the control of the control device  5 , illumination light to illuminate the subject eye. 
     The microscope unit  22  corresponds to an imaging device according to the present disclosure. As illustrated in  FIG. 1  or  FIG. 2 , this microscope unit  22  includes an observation optical system  221  ( FIG. 2 ), an eyepiece  222 , and an imaging unit  223  ( FIG. 2 ). 
     The observation optical system  221  includes an objective lens  2211  ( FIG. 1 ,  FIG. 2 ), a lens unit  2212  ( FIG. 2 ), and a half mirror  2213  ( FIG. 2 ), and guides light reflected from the subject eye to the eyepiece  222  and the imaging unit  223 . To be specific, the light reflected from the subject eye enters the half mirror  2213  through the objective lens  2211  and the lens unit  2212 . The approximately half of the light that has entered the half mirror  2213  passes through the half mirror  2213  to enter the eyepiece  222 . On the other hand, the other half of the light that has entered the half mirror  2213  is reflected on the half mirror  2213  to enter the imaging unit  223 . 
     Here, the lens unit  2212  includes a zooming lens  2214  ( FIG. 2 ). 
     The zooming lens  2214  is formed by use of one or a plurality of lenses, and moves along an optical axis Ax ( FIG. 2 ) to adjust the angle of view. The optical axis Ax is an axis extending in the vertical direction of  FIG. 1 . Specifically, the optical axis Ax is the axis from the microscope unit  22  toward the subject eye, and corresponds to an observation optical axis according to the present disclosure. 
     The lens unit  2212  also includes an optical zooming mechanism (not illustrated) for moving the zooming lens  2214  along the optical axis Ax. 
     The eyepiece  222  condenses the light incident from the observation optical system  221  to form an optical image of the subject eye. This allows the surgeon who looks through the eyepiece  222  to observe the optical image of the subject eye. 
     The imaging unit  223  includes an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) that receives the light incident from the observation optical system  221  and converts the light into an electric signal. The imaging unit  223  then generates an image signal including the subject eye by image-capturing under the control of the control device  5 . 
     The base unit  23  is a base of the surgical microscope  2 , and is formed to be movable on a floor surface via casters  231  ( FIG. 1 ). 
     The supporting unit  24  extends from the base unit  23 , and supports the microscope unit  22  at a distal end thereof (end away from the base unit  23 ). As illustrated in  FIG. 1 , the supporting unit  24  includes an XY-stage  241 , an XY-moving unit  242 , and a Z-moving unit  243 . 
     The XY-stage  241  supports the XY-moving unit  242  so that the XY-moving unit  242  may move in the X-direction and in the Y-direction. Here, the X-direction and the Y-direction are along a plane orthogonal to the optical axis Ax and are orthogonal to each other. 
     The XY-moving unit  242  is a part movable in the X-direction and in the Y-direction with respect to the XY-stage  241 . The XY-moving unit  242  supports the Z-moving unit  243  so that the Z-moving unit  243  may move in the Z-direction. Here, the Z-direction is along the optical axis Ax (the vertical direction in  FIG. 1 ) and is orthogonal to the X-direction and the Y-direction. 
     The Z-moving unit  243  is a part movable in the Z-direction with respect to the XY-moving unit  242 . The Z-moving unit  243  supports the microscope unit  22 . 
     To be specific, the microscope unit  22  may be moved in the X-direction and in the Y-direction by operating the XY-moving unit  242 . Further, the microscope unit  22  may be moved in the Z-direction by operating the Z-moving unit  243 . 
     As illustrated in  FIG. 2 , the driving unit  25  includes an XY-driving unit  251 , a Z-driving unit  252 , and a lens driving unit  253 . 
     The XY-driving unit  251  is an actuator such as a motor, and under the control of the control device  5 , the XY-driving unit  251  operates the XY-moving unit  242  and moves the microscope unit  22  in the X-direction and in the Y-direction. 
     The Z-driving unit  252  is an actuator such as a motor, and under the control of the control device  5 , the Z-driving unit  252  operates the Z-moving unit  243  and moves the microscope unit  22  in the Z-direction. 
     The lens driving unit  253  is an actuator such as a motor, and under the control of the control device  5 , the lens driving unit  253  operates the optical zooming mechanism (not illustrated) to adjust the angle of view. 
     The display device  3  is formed by a display using liquid crystal, organic electro luminescence (EL), or the like, and under the control of the control device  5 , the display device  3  displays an image based on a video signal from the control device  5 . 
     The input device  4  is formed by use of an operational device such as a mouse, a keyboard, and a touch panel, and receives user operation from a user such as a surgeon. The input device  4  then outputs an operation signal according to the user operation to the control device  5 . 
     The control device  5  corresponds to a medical control device according to the present disclosure. The control device  5  collectively controls the operation of the surgical microscope  2  and the display device  3 . As illustrated in  FIG. 2 , the control device  5  includes a communication unit  51 , an image processing unit  52 , a control unit  53 , and a storage unit  54 . 
     The communication unit  51  is an interface for communication with the surgical microscope  2 , and receives an image signal generated by the imaging unit  223  and sends a control signal received from the control unit  53 . 
     The image processing unit  52  corresponds to an image generation unit according to the present disclosure. The image processing unit  52  performs image processing on the image signal received by the communication unit  51 , generates a video signal for display with which to display an image for display according to a captured image based on the image signal in the display device  3 , and outputs the video signal to the display device  3 . 
     Here, examples of the image processing include digital gain processing of multiplying the image signal (digital signal) received by the communication unit  51  by a digital gain for amplifying the digital signal, optical black subtraction processing, white balance (WB) adjustment processing, demosaic processing, color matrix calculation processing, gamma correction processing, YC conversion processing of generating a luminance signal and a color difference signal (Y, Cb/Cr signal), enlargement processing (electronic zoom), and the like. 
     The control unit  53  is implemented by, for example, a central processing unit (CPU), a field-programmable gate array (FPGA), and the like, controls the operation of the surgical microscope  2  and the display device  3 , and controls the entire operation of the control device  5 . The control unit  53  has functions of a determination unit and a state controller according to the present disclosure. The functions of the determination unit and the state controller are described in “operation of control device” later. Further, the control unit  53  may be configured, for example, as an IP converter having an image processing function. In such a case, the control unit  53  functions as an IP converter on the video source side that performs IP conversion on a video outputted from the surgical microscope  2  (video source) and sends the resultant over a network. The display device  3  is provided with an IP converter on the video output side that converts the video sent via the network into a format unique to the display device  3 , and outputs the resultant. The IP converter on the video source side functions as an encoder, and the IP converter on the video output side functions as a decoder. 
     The storage unit  54  stores programs executed by the control unit  53 , information necessary for the processing of the control unit  53 , and so on. 
     About Cataract Surgery 
     Before the operation of the control device  5  is described, a brief description of the cataract surgery is given. 
       FIGS. 3A to 3E  are diagrams for explanation of surgical tools used for cataract surgery. In  FIGS. 3A to 3E , the reference sign “ 100 ” indicates the subject eye. In addition, the reference sign “ 110 ” indicates the cornea. Further, the reference sign “ 120 ” indicates a pupil. 
     In the cataract surgery, the surgeon performs a port creation step, an anterior capsulotomy step, a hydrodissection step, a crystalline lens nucleus treatment step, and an intraocular lens insertion step in the stated order. 
     In the port creation step, a knife T 1  illustrated in  FIG. 3A  is used. The knife T 1  corresponds to a first surgical tool according to the present disclosure. In the port creation step, the surgeon incises a cornea  110  of the subject eye  100  ( FIG. 3A ) with the knife T 1  to define a port (incision). 
     The anterior capsulotomy step is called a continuous curvilinear capsulorrhexis (CCC) step. In the anterior capsulotomy step, tweezers T 2  with a pointed distal end illustrated in  FIG. 3B  are used. The tweezers T 2  correspond to a second surgical tool according to the present disclosure. In the anterior capsulotomy step, the surgeon inserts the tweezers T 2  through the port defined in the port creation step and incises the anterior portion of the crystalline lens, that is, the anterior capsule portion in a circular shape. 
     In the hydrodissection step, a cannula T 3  illustrated in  FIG. 3C  is used. The cannula T 3  corresponds to a third surgical tool according to the present disclosure. In the hydrodissection step, the surgeon inserts the distal end of the cannula T 3  between the crystalline lens capsule (the skin surrounding the crystalline lens) and the crystalline lens cortex through the port defined in the port creation step, and makes perfusate flow. This separates the crystalline lens capsule and the crystalline lens cortex from each other. 
     In the crystalline lens nucleus treatment step, a suction tube T 4  illustrated in  FIG. 3D  is used. The suction tube T 4  corresponds to a fourth surgical tool according to the present disclosure. In the crystalline lens nucleus treatment step, the surgeon inserts the suction tube T 4  through the port defined in the port creation step. The surgeon also performs emulsification (pulverization) and aspiration of the nucleus of the crystalline lens through the suction tube T 4  by ultrasonic vibration called nucleus treatment, and also aspirates the cortex. 
     In the intraocular lens insertion step, a cartridge T 5  illustrated in  FIG. 3E  is used. The cartridge T 5  corresponds to a fifth surgical tool according to the present disclosure. In the intraocular lens insertion step, first, the surgeon places an intraocular lens in the cartridge T 5 . The surgeon also inserts the cartridge T 5  through the port defined in the port creation step, and pushes the intraocular lens out of the cartridge T 5  and inserts the same into the subject eye. 
     Operation of Control Device 
     The description goes on to the operation of the control device  5 . Hereinafter, the description is provided mainly of the functions of the determination unit of the control unit  53  and the state controller of the control unit  53  in the cataract surgery. 
       FIG. 4  is a flowchart depicting operation of the control device  5 .  FIGS. 5 to 7  are diagrams for explanation of the operation of the control device  5 . 
     First, the communication unit  51  acquires an image signal generated by the imaging unit  223  (Step S 1 ). Then, the image processing unit  52  performs image processing on the image signal. 
     After Step S 1 , the control unit  53  (determination unit) executes surgical tool detection processing of detecting the usage of a specific surgical tool T 0  (see  FIG. 5 ) among the knife T 1 , the tweezers T 2 , the cannula T 3 , the suction tube T 4 , and the cartridge T 5  (Step S 2 ). Note that surgical tools other than the exemplified surgical tools may also be detected in the surgical tool detection processing as long as the surgical tools are registered or learned before surgery. 
     In this embodiment, in Step S 2 , the control unit  53  (determination unit) uses a known method such as image recognition using pattern matching or artificial intelligence (AI) for example to determine whether or not the specific surgical tool T 0  is included in the captured image based on the image signal that has been subjected to the image processing by the image processing unit  52 . The specific surgical tool T 0  is at least one of the knife T 1 , the tweezers T 2 , the cannula T 3 , the suction tube T 4 , and the cartridge T 5 , and the specific surgical tool T 0  is set by user operation (setting input) to the input device  4  by the user, for example. The setting input may be, for example, selecting (mode selection) any one of the steps of the port creation step, the anterior capsulotomy step, the hydrodissection step, the crystalline lens nucleus treatment step, and the intraocular lens insertion step, and the selection of any one of the steps allows at least any one of the surgical tools corresponding to that any one of the steps to be set as the specific surgical tool T 0 . 
     Then, when determining that the specific surgical tool T 0  is included in the captured image after execution of the processing of Step S 2  (Step S 3 : Yes), the control device  5  returns to the processing of Step S 1 . 
       FIG. 5  is a diagram for explanation a change in imaging field of view in a case where the specific surgical tool T 0  is included in the captured image C 1 . Note that  FIG. 5  illustrates a state in which the enlargement processing is not performed by the image processing unit  52  (zoom magnification of 1×), and the entire image area of the captured image C 1  that has been subjected to the image processing by the image processing unit  52  is displayed in the screen of the display device  3  as an image for display. 
     For example, as illustrated in  FIG. 5 , in a case where the specific surgical tool T 0  is included in the captured image C 1 , the control unit  53  does not execute the processing of Steps S 4  and S 5  described later. To be specific, even if a center position P 2  of the subject eye  100  moves from a specific position P 1  in the captured image C 1  ( FIG. 5( b ) ), the imaging field of view does not change, and the center position P 2  remains deviated from the specific position P 1  ( FIG. 5( c ) ). Note that, in  FIG. 5 , the specific position P 1  is used as the center position of the captured image C 1  (the screen center of the display device  3 ); however, the specific position P 1  is not limited thereto, and may be other positions. The same applies to  FIGS. 6 and 7 . 
     On the other hand, when determining that no specific surgical tool T 0  is included in the captured image after execution of the processing of Step S 2  (Step S 3 : No), the control unit  53  executes the processing of Steps S 4  and S 5  in this order. 
       FIG. 6  is a diagram for explanation of a change in imaging field of view in a case where no specific surgical tool T 0  is included in the captured image C 1 . Note that  FIG. 6  illustrates a case where none of the surgical tools of the knife T 1 , the tweezers T 2 , the cannula T 3 , the suction tube T 4 , and the cartridge T 5  is included in the captured image C 1 . In addition, similarly to  FIG. 5 ,  FIG. 6  illustrates a state in which the enlargement processing is not performed by the image processing unit  52  (zoom magnification of 1×), and the entire image area of the captured image C 1  that has been subjected to the image processing by the image processing unit  52  is displayed in the screen of the display device  3  as an image for display. 
     For example, as illustrated in  FIG. 6 , in a case where no specific surgical tool T 0  is included in the captured image C 1 , the control unit  53  (state controller) executes the processing of Step S 4 . 
       FIG. 7  is a diagram for explanation of Step S 4 . Specifically,  FIG. 7  is a diagram corresponding to  FIG. 6( b ) . 
     Specifically, in Step S 4 , the control unit  53  (state controller) extracts at least one feature point from structural features in the subject eye  100  included in the captured image C 1 . For example, the control unit  53  (state controller) extracts at least one feature point based on at least one of the contour of the pupil  120 , the contour of an iris (the contour of the cornea  110 ), the pattern of the iris, and the shape of the blood vessel of sclera in the subject eye  100 . The control unit  53  (state controller) then recognizes the center position P 2  of the subject eye  100  based on that at least one feature point. Further, the control unit  53  (state controller) calculates the movement amount in the X-direction and the Y-direction of the microscope unit  22  and the movement direction thereof necessary to make sure that the center position P 2  is located at the specific position P 1  based on the positional relationship (deviation amount D 1  ( FIG. 7 ) and deviation direction D 2  ( FIG. 7 )) between the specific position P 1  in the captured image C 1  and the center position P 2  of the subject eye  100 . 
     After Step S 4 , the control unit  53  (state controller) executes the processing of Step S 5 . 
     Specifically, in Step S 5 , the control unit  53  (state controller) operates the XY-moving unit  242  through the XY-driving unit  251  to move the microscope unit  22  by the movement amount and in the movement direction calculated in Step S 4 . 
     As a result, in a case where the center position P 2  of the subject eye  100  moves from the specific position P 1  in the captured image C 1  ( FIG. 6( b ) ), the imaging field of view changes so as to maintain the state in which the center position P 2  is located at the specific position P 1  ( FIG. 6( c ) ). 
     The embodiment described above achieves the following effects. 
     The control device  5  according to the embodiment controls the imaging field of view so as to maintain the state of the subject eye  100  in the captured image C 1  (image for display) only in a case where it is determined that no specific surgical tool T 0  is included in the captured image C 1 . More specifically, only in such a case, the control device  5  controls the imaging field of view by moving the microscope unit  22  in the X-direction and the Y-direction, thereby maintains the state in which the center position P 2  of the subject eye  100  is located at the specific position P 1  in the captured image C 1 . 
     Therefore, in a case where the specific surgical tool T 0  is the knife T 1  for example, even if the control of the imaging field of view is not executed, no more pressure from the knife T 1  to the subject eye  100  is applied after the creation of the port, and the center position P 2  of the subject eye  100  in the captured image C 1  returns to the original position. On the other hand, in a case where a patient changes his/her posture or the patient moves his/her line of sight, the control of the imaging field of view is automatically executed, which eliminates the need for the surgeon to perform complicated work of operating the medical observation system  1  (XY-moving unit  242 ) to change the imaging field of view. 
     Therefore, according to the control device  5  of the embodiment, the control of the imaging field of view is executed only when necessary, which improves convenience. 
     Further, the control device  5  according to the embodiment recognizes the center position of the subject eye  100  based on at least one of the contour of the pupil  120 , the contour of the cornea  110  (the contour of the iris), the pattern of the iris, and the shape of the blood vessel of the sclera in the subject eye  100  included in the captured image C 1 . Therefore, the control of the imaging field of view may be executed with high accuracy. 
     Further, the control device  5  according to the embodiment executes the control of the imaging field of view based on the positional relationship between the specific position P 1  in the captured image C 1  (the center position of the image for display) and the center position P 2  of the subject eye  100 . Therefore, the control of the imaging field of view may be executed with high accuracy by using simple calculation. 
     Other Embodiments 
     Although the embodiment for carrying out the present disclosure has been described so far, the present disclosure should not be limited only to the embodiment. 
     In the embodiment, the control unit  53  controls the imaging field of view to maintain the state in which the center position P 2  of the subject eye  100  is located at a specific position in the image for display (the specific position P 1  in the captured image C 1 ); however, the present disclosure is not limited thereto. 
     For example, the control unit  53  may control the operation of the image processing unit  52  to maintain the state in which the center position P 2  of the subject eye  100  is located at a specific position in the image for display. Specifically, the enlargement processing (electronic zoom) executed by the image processing unit  52  is processing of cutting out, from the captured image C 1 , a partial rectangular area (rectangular area according to a designated zoom magnification) of the entire image area in the captured image C 1  and enlarging the image of the rectangular area at the zoom magnification. The control unit  53  then controls the operation of the image processing unit  52  to change the cut-out position of the partial area, and maintains the state in which the center position P 2  of the subject eye  100  is located at a specific position in the image for display. In such a case also, as a method for recognizing the center position P 2  of the subject eye  100 , the method described in the first embodiment (method using the contour of the pupil  120  or the like) may be adopted. Further, as with the first embodiment, the control unit  53  changes the cut-out position of the partial area based on the positional relationship (the deviation amount D 1  and the deviation direction D 2 ) between the center position of the image for display and the center position P 2  of the subject eye  100 . 
     Further, for example, the control unit  53  may control the imaging field of view to maintain the state in which the subject eye  100  in the image for display has a specific size. Specifically, the control unit  53  operates the Z-moving unit  243  through the Z-driving unit  252  or moves the zooming lens  2214  along the optical axis Ax through the lens driving unit  253 , and thereby maintains the state in which the subject eye  100  in the image for display has a specific size. Further, the control unit  53  may control the operation of the image processing unit  52  to maintain the state in which the subject eye  100  in the image for display has a specific size. For example, in the enlargement processing (electronic zoom) executed by the image processing unit  52 , the state in which the subject eye  100  in the image for display has a specific size is maintained by changing the zoom magnification (magnification). As a result, for example, even in a situation where the size of the subject eye  100  in the image for display changes in response to a patient changing his/her posture, the size may be kept constant at all times. The surgeon thus may smoothly perform cataract surgery and the like while confirming the image for display. 
     Further, for example, as long as the surgical microscope  2  has a configuration in which the optical axis Ax may be inclined, the state in which the center position P 2  of the subject eye  100  is located at a specific position in the image for display may be maintained by inclining the optical axis Ax (controlling the imaging field of view). 
     In the embodiment described above, the cataract surgery is exemplified; however, the medical observation system  1  according to the present disclosure is of course applicable to other eye surgery such as vitreoretinal surgery. 
     Note that the following configurations also falls within the technical scope of the present disclosure. 
     (1) A medical control device including: a determination unit configured to determine whether or not a specific surgical tool is included in a captured image based on an image signal generated by an imaging device that captures an image of a subject eye; an image generation unit configured to generate an image for display based on the image signal; and a state controller configured to control, in a case where the determination unit determines that the specific surgical tool is not included in the captured image, operation of the image generation unit or an imaging field of view by the imaging device so as to maintain a state of the subject eye in the image for display. 
     (2) The medical control device according to (1), in which the state controller controls the imaging field of view to maintain a state in which a center position of the subject eye is located at a specific position in the image for display. 
     (3) The medical control device according to (2), in which the state controller recognizes the center position of the subject eye based on a structural feature of the subject eye included in the captured image. 
     (4) The medical control device according to (3), in which the structural feature of the subject eye is at least one of a contour of a pupil, a contour of an iris, a pattern of the iris, and a shape of a blood vessel of sclera in the subject eye. 
     (5) The medical control device according to any one of (2) to (4), in which the state controller controls the imaging field of view based on a positional relationship between a center position of the image for display and a center position of the subject eye included in the image for display. 
     (6) The medical control device according to any one of (2) to (5), in which the state controller moves, in the control of the imaging field of view, the imaging device in a plane orthogonal to an observation optical axis from the imaging device toward the subject eye. 
     (7) The medical control device according to (1), in which a state of the subject eye in the image for display is a size of the subject eye in the image for display. 
     (8) The medical control device according to (7), in which the state controller controls the imaging field of view to maintain a state in which the size of the subject eye in the image for display is a specific size. 
     (9) The medical control device according to (8), in which the state controller moves, in the control of the imaging field of view, the imaging device in a direction along an observation optical axis from the imaging device toward the subject eye. 
     (10) The medical control device according to (8), in which the state controller changes a magnification by a zooming lens included in the imaging device in the control of the imaging field of view. 
     (11) The medical control device according to (7), in which the image generation unit generates the image for display by cutting out and enlarging a partial area of the captured image, and the state controller controls a magnification of the partial area in the image generation unit to maintain a state in which the size of the subject eye in the image for display is a specific size. 
     (12) The medical control device according to (1), in which the state controller controls operation of the image generation unit to maintain a state in which a center position of the subject eye is located at a specific position in the image for display. 
     (13) The medical control device according to (12), in which the state controller recognizes a center position of the subject eye based on a structural feature of the subject eye included in the captured image. 
     (14) The medical control device according to (13), in which the structural feature of the subject eye is at least one of a contour of a pupil, a contour of an iris, a pattern of the iris, and a shape of a blood vessel of sclera in the subject eye. 
     (15) The medical control device according to any one of (12) to (14), in which the image generation unit cuts out a partial area of the captured image to generate the image for display, and the state controller controls operation of the image generation unit to change a cut-out position of the partial area. 
     (16) The medical control device according to (15), in which the state controller changes the cut-out position of the partial area based on a positional relationship between a center position of the image for display and a center position of the subject eye included in the image for display. 
     (17) The medical control device according to any one of (1) to (16), in which the specific surgical tool is a surgical tool used for cataract surgery, and is at least one of a first surgical tool used for creation of a port, a second surgical tool used for incision of an anterior capsule, a third surgical tool used for hydrodissection, a fourth surgical tool used for crystalline lens nucleus treatment, and a fifth surgical tool used for insertion of an intraocular lens. 
     (18) A medical observation system including: an imaging device configured to capture an image of a subject eye; and a medical control device configured to process an image signal generated by the imaging device, in which the medical control device includes a determination unit configured to determine whether or not a specific surgical tool is included in a captured image based on the image signal; an image generation unit configured to generate an image for display based on the image signal; and a state controller configured to control, in a case where the determination unit determines that the specific surgical tool is not included in the captured image, operation of the image generation unit or an imaging field of view by the imaging device so as to maintain a state of the subject eye in the image for display. 
     The medical control device and the medical observation system according to the present disclosure may improve convenience. 
     Although the disclosure has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.