Surgical robotic system for ophthalmic surgery and its control

Abstract

A surgical robotic system for use in an ophthalmic surgical procedure is provided. The system includes a surgical arm (080) including a movable arm portion (082), the surgical arm (080) including an instrument connector for attaching a surgical instrument (119) having a longitudinal axis. The movable arm portion (082) has at least one degree of freedom that allows longitudinal movement of the surgical instrument (119) along its longitudinal axis toward or away from an ophthalmic surgical target (123). The system includes a sensor (030), a user interface (020), an actuator (060), and a processor subsystem (040). The processor subsystem (040) is configured to acquire sensor data (032) from the sensor (030) at an initial position of the surgical instrument (119), determine an initial distance between the surgical instrument (119) and the surgical target (123), acquire data indicative of a target position of the surgical instrument (119), determine a displacement distance, output a sensory perceptible representation of the displacement distance, receive a confirmation signal from a user, and upon receiving the confirmation signal, control the actuator (060) to actuate the movable arm portion (082) to cause a single movement of the surgical instrument (119) over the displacement distance.

Description

[Technical field]

[0001] The present invention relates to a surgical robotic system for use in ophthalmic surgical procedures. The present invention further relates to a method for controlling a surgical robotic system during use in an ophthalmic surgical procedure, and to a computer program product including instructions for causing a processor system to carry out the method. [Background technology]

[0002] Ophthalmic surgical procedures increasingly involve the use of surgical robotic systems. Such surgical robotic systems do not operate fully autonomously, but are typically at least partially under the control of a human operator, for example to control the movement of a surgical instrument attached to a surgical arm of the surgical robotic system. Thus, the surgical robotic system may assist the human operator in performing the surgical procedure.

[0003] Robotic assistance can improve the precision of surgical instrument movement. Ophthalmic surgery requires particularly high precision, given the complexity and size of the tissues and structures found in and around the eye. However, robotic systems provide such precision in absolute coordinates, not relative to the tissue. For example, tissue fluctuations or movements reduce the precision provided by robotic assistance. Furthermore, the surgeon operating the robot has only a limited view of the surgical field through a microscope. Depth perception, in particular, becomes difficult.

[0004] There are existing surgical robotic systems that include a movable arm section, which may comprise a surgical arm including an instrument connector for attaching a surgical instrument. Thus, the surgical instrument may be positioned by the surgical arm. To control the movement of the surgical instrument, a human machine interface may be provided for receiving positioning commands from a human operator. An actuator may be provided for actuating the movable arm section to cause the movement of the surgical instrument according to the positioning commands provided by the human operator. An example of this approach may be found in the field of teleoperation, where a human operator may operate a master device, e.g., a motion controller, to provide positioning commands to a slave device, e.g., the aforementioned surgical arm.

[0005] However, such systems do not reliably provide the level of precision required for ophthalmic surgical procedures, and typically mitigate the challenge by processing position commands received from the user, such as to reduce the effects of hand tremors.

[0006] US Patent Publication No. 20190110682(A1) introduces the use of an optical coherence tomography (OCT) sensor in a vitreoretinal surgical application to detect when a surgical injector penetrates a desired tissue layer of the eye. The OCT sensor is used to scan the surgical target. Instructions are received from a user, for example to identify the tissue layer to receive injection or to confirm automatic injection. Summary of the Invention [Problem to be solved by the invention]

[0007] A challenge with fully automating the movement of a surgical instrument toward a surgical target is that such movement may be based on noisy or otherwise unreliable sensor data. Users (typically surgeons) have historically had concerns about adopting fully automated procedures for this reason. For example, if the surgical target is in a subretinal position, movement of the eye or surgical instrument may cause the sensor measurements indicating the location of the surgical target to become less reliable, or introduce the risk of the surgical instrument puncturing an unintended tissue or organ if the sensor is partially or completely obscured, for example, by tissue debris. [Means for solving the problem]

[0008] One objective of the present invention is to provide a surgical robotic system and / or a method of controlling a surgical robotic system that allows a user to control the displacement of a surgical instrument while still maintaining the advantages of automatic movement, including reduced effects of hand tremor or shaking. Giving the user control over the displacement of the surgical instrument also addresses inherent user concerns about employing automated procedures. This combination of automatic movement and user control over instrument displacement improves the reliability of the surgical robotic system.

[0009] A first aspect of the present invention is a surgical robotic system for use in an ophthalmic surgical procedure, comprising: - a surgical arm including a movable arm portion including an instrument connector for attaching a surgical instrument having a longitudinal axis, the movable arm portion having at least one degree of freedom to permit longitudinal movement of the surgical instrument along the longitudinal axis of the surgical instrument toward or away from the ophthalmic surgical target; - a sensor configured to acquire sensor data indicative of a distance between a surgical instrument and a surgical target; - Receive user input from the user and provide the user with a sense Perceived Possible N a user interface configured to output an output; - an actuator constructed and arranged to actuate the moveable arm to cause longitudinal movement of the surgical instrument; a processor subsystem, - acquiring sensor data from a sensor at an initial position of the surgical instrument and determining an initial distance between the surgical instrument and the surgical target based on the sensor data; - obtaining data indicative of a target position of a surgical instrument relative to a surgical target; - determining a displacement distance of the surgical instrument based on the sensor data and the target position; - Sense of the determined displacement distance via the user interface Perceived Possible N Print the expression, - receiving a confirmation signal from the user via the user interface; - upon receiving the confirmation signal, controlling the actuator to actuate the moveable arm to effect a single movement of the surgical instrument along the longitudinal axis over the determined displacement distance. a processor subsystem configured to The present invention provides a surgical robotic system comprising:

[0010] In a further aspect of the invention, there is provided a computer-implemented method for controlling a surgical robotic system during use in an ophthalmic surgical procedure, the surgical robotic system including a surgical arm including a movable arm portion including an instrument connector for attaching a surgical instrument having a longitudinal axis, the movable arm portion having at least one degree of freedom to enable longitudinal movement of the surgical instrument along the longitudinal axis of the surgical instrument towards or away from the ophthalmic surgical target, the surgical robotic system further including an actuator constructed and arranged to actuate the movable arm portion to effect the longitudinal movement of the surgical instrument, the method comprising: - acquiring sensor data indicative of a distance between the surgical instrument and a surgical target at an initial position of the surgical instrument; - determining an initial distance between the surgical instrument in an initial position and the surgical target based on the sensor data; - obtaining data indicative of a target position of a surgical instrument relative to a surgical target; - determining a displacement distance of the surgical instrument based on the sensor data and the target position; - Sense of Displacement Distance Perceived Possible N outputting the representation to a user; and - receiving a confirmation signal from the user; - upon receiving a confirmation signal, controlling the actuator to actuate the moveable arm to cause a unitary movement of the surgical instrument along the longitudinal axis over a displacement distance; A computer-implemented method is provided, comprising:

[0011] In a further aspect of the invention, a computer program product is provided comprising instructions for causing a processor system to perform a method.

[0012] The above aspects of the invention include a surgical robotic system including a surgical arm. The surgical arm includes a movable arm section, the movable arm section including an instrument connector for attaching a surgical instrument. The surgical instrument typically has a longitudinal axis passing through the tip of the surgical instrument. The movable arm section has at least one degree-of-freedom (DoF) that allows longitudinal movement of the surgical instrument along the longitudinal axis of the surgical instrument toward a surgical target. The surgical target may be, for example, a tissue layer, or a surface of such a layer, such as a surface of an epiretinal layer. It is noted that the movable arm section may have only one DoF aligned with the longitudinal axis of the surgical instrument to allow said longitudinal movement. However, the movable arm section may also have multiple DoFs that allow said longitudinal movement, but each DoF does not have to be individually aligned with the longitudinal axis. It is noted that surgical arms having the functionality described in this paragraph are known per se from the field of medical robotics and are also known as instrument manipulators, robotic arms, surgical robot slave devices etc.

[0013] The user interface receives user input, such as positioning commands, from a user and provides sensory input to the user. Perceived Possible N A drive mechanism is provided for driving the surgical instrument and for outputting an output. Further, an actuator is provided for actuating the moveable arm to cause longitudinal movement of the surgical instrument. Another term for actuator is a drive mechanism. Further, a sensor is provided for acquiring sensor data indicative of a distance between the surgical instrument, e.g., a tip of the surgical instrument, and a surgical target.

[0014] A processor subsystem is provided for controlling the actuator to actuate the movable arm to move the surgical instrument along the longitudinal axis. At an initial position of the surgical instrument, the processor subsystem may obtain sensor data from the sensor and determine an initial distance between the surgical instrument and the surgical target. The processor subsystem may obtain data indicative of a target position of the surgical instrument relative to the surgical target. For example, the data indicative of the target position may be obtained from a user in the form of a user input, or may be automatically determined based on sensing of a particular anatomical structure, or the like. The target position may be the position of the surgical target, or another position, for example, between the surgical target and the initial position of the surgical instrument. The processor subsystem may determine a displacement distance of the surgical instrument based on the sensor data and the target position. For example, the displacement distance may be a distance that the surgical instrument travels in a single initial movement. The processor subsystem may determine a displacement distance based on the determined displacement sense. Perceived Possible N You may output the expression. Perceived Possible NThe representation may be, for example, an audio output indicating the determined displacement distance, an audio output indicating, for example, proximity, a graphical output such as an overlay on the image of the interior of the eye with the determined displacement distance, or a text output such as a visual output of a number representing the determined displacement distance, tactile feedback, etc. Thus, the user may confirm the determined displacement distance, and the processor subsystem may receive a confirmation signal via the user interface. The confirmation signal may be any type of user input indicating that the user has confirmed the determined displacement distance, including a voice command, for example, clicking a button on a graphical user interface, etc. Once the confirmation signal is received, the processor subsystem may control the actuator to actuate the movable arm portion to cause a single movement of the surgical instrument along the longitudinal axis over the determined displacement distance. That is, the user confirms the distance the surgical instrument will travel. Here, the term "single movement" may also be considered to be a single fluid movement with no pause or pause interrupting the movement. The term "longitudinal movement towards or away from the surgical target" refers to a forward movement of the surgical instrument or a backward movement of the surgical instrument.

[0015] Determining the displacement distance of the surgical instrument allows a user (e.g., a surgeon) to maintain control over the placement and advancement of the surgical instrument while performing the movement in an automated manner when performing surgery in or on the eye. Since the measurements are based on sensor data, there is a risk that the sensor data may be too noisy to provide a reliable measurement. This may result in an inappropriate distance being calculated. Having the user approve the determined displacement distance before a single movement of the surgical instrument is performed provides the user with the opportunity to prevent the movement of the surgical instrument in case the sensor data is inappropriate or inaccurate. That is, the user is asked to confirm the next step of the movement of the surgical instrument before said movement is performed. The determined displacement distance is communicated to the user and the user is requested to confirm the determined displacement distance. Doing so allows the user to disapprove the determined displacement distance if it is inappropriate. This allows the user to maintain control over the procedure while the movement of the surgical instrument itself is performed in an automated manner, reducing or eliminating the risks associated with manual injection, such as trembling or shaking of the hand. Additionally, the displacement distance traveled by the surgical instrument in a single movement is determined after sensor data indicative of the distance measurements is acquired, and the sensor data is preferably acquired while the surgical instrument is stationary, which may improve the reliability of the sensor measurements, especially if the sensor data is acquired while the surgical instrument is in a stationary position.

[0016] Optionally, the processor subsystem may obtain the latest sensor data from the sensor upon completing a single movement of the surgical instrument, determine a remaining distance between the surgical instrument and the surgical target based on the latest sensor data, determine whether the target position has been reached based on the determined remaining distance, and if not, control the actuator to correct the depth of the surgical instrument based on the determined remaining distance. Thus, any movement of the eye or structures within the eye due to, for example, changes in intraocular pressure, breathing, patient movement, or reactions to the movement of the surgical instrument that may move the target position and / or the surgical target may be taken into account. Furthermore, the latest sensor data may provide a more reliable measurement, such as when an initial measurement is partially or completely obscured, for example, by tissue debris or other structures or tissues within or around the eye. The latest sensor data may be obtained while the surgical instrument is in a different position that may be closer to the surgical target, which may have less noise.

[0017] Optionally, the processor subsystem determines a correction displacement distance to reach the target position from the determined remaining distance to the surgical target, and displays, via a user interface, a sense of the correction displacement distance. Perceived Possible N The representation may be output and a further confirmation signal may be received from the user via the user interface, and upon receipt of the further confirmation signal, the actuator may be controlled in a displacement-based control mode to correct the depth of the surgical instrument by controlling the actuator to actuate the movable arm to cause a further single movement of the surgical instrument along the longitudinal axis over a corrective displacement distance. In this correction procedure, the latest sensor data is acquired before the surgical instrument moves to correct its position. The corrective displacement distance is then determined after the latest sensor data is acquired. The user is again asked to confirm the determined corrective displacement distance, thus providing a further opportunity to ensure that the distance the surgical instrument moves is reasonable. This therefore increases the safety and reliability of the further steps of movement of the surgical instrument.

[0018] Optionally, the processor subsystem may control the actuator in a limited closed-loop control mode that uses the most recent sensor data to correct the surgical instrument depth, the limited closed-loop control mode being limited by at least one of a predefined duration of use of the limited closed-loop control mode, a predefined maximum correction displacement distance, requiring the certainty score to remain above a certainty score threshold during the correction (the certainty score represents the certainty of the determined remaining distance), and requiring continuous user input during the correction and ceasing the movement of the surgical instrument upon detecting that the continuous user input has ended. Thus, in this mode, the level of automation of the system is controlled by the factors mentioned above, thereby preventing a fully automated system that users may not readily adopt, while still providing the benefits of moving an automated process. For example, the requirement that the certainty score be above a threshold allows the movement of the surgical instrument to be automated when the sensor data is sufficiently reliable, and prevents automatic movement when the sensor data is unreliable, which may lead to overshooting or not reaching the target position. Requiring continuous user input during the correction may ensure that the user is involved and paying attention. Time or displacement limitations may similarly limit the extent to which a surgical robotic system is automated. For example, the automatic movement of a surgical instrument may stop after some amount of time or after some displacement, and then resume, for example, with updated sensor data. This limited level of automation of the system may thus improve patient safety during a surgical procedure.

[0019] Optionally, the processor subsystem may calculate a certainty score representing the certainty of the determined distance between the surgical instrument and the surgical target, and adapt the control of the actuator according to the calculated certainty score. The certainty score may be based on at least one of an estimate of the measurement noise of the sensor, a detection of the presence of dynamic motion of the surgical target, a comparison of the sensor data with a model representative of a reference of the sensor data, and a comparison between the estimated surgical target position and a predicted surgical target position, the predicted surgical target position being based on the instrument movement measured by the at least one position sensor. For example, if the certainty score is high, the speed of the surgical instrument may be increased, and if the certainty score is low, the speed of the surgical instrument may be decreased. In this way, the procedure may proceed more quickly when the sensor data is more reliable (e.g., high certainty score), thereby reducing the duration of the surgical procedure (and therefore the patient's discomfort over time), and the surgical instrument may move more slowly when the sensor data is less reliable, preventing the surgical instrument from extending beyond the surgical target. The use of a certainty score and adapting the control of the actuator according to the certainty score can enable a user (e.g., a surgeon) to decide when more manual control is needed to ensure patient safety and surgical precision and when a more automated approach can be utilized, potentially speeding up the procedure and reducing patient discomfort.

[0020] Optionally, the processor subsystem may repeatedly calculate the certainty score and may execute an abort procedure if the calculated certainty score falls below a certainty score threshold. The abort procedure may include at least one of retracting the surgical instrument, pausing the movement of the surgical instrument, and switching from controlling the actuator in a limited closed-loop control mode to controlling the actuator with a motion controller-based control model, and the processor subsystem may control the actuator according to position control commands received from the user via the motion controller. Repeatedly calculating the certainty score may prevent progression of the movement of the surgical instrument when the sensor data is too noisy or unreliable, thereby reducing the risk of unintended movement of the surgical instrument and damage to structures in or on the eye.

[0021] Optionally, the processor subsystem may select a control mode from a set of control modes based on the calculated certainty score, the set of control modes including at least two of a motion controller based control mode, a displacement based control mode, and a limited closed loop control mode. In the motion controller based control mode, the processor subsystem may control the actuator according to position control commands received from a user via a motion controller of a user interface. In the displacement based control mode, the processor subsystem may determine a correction displacement distance to reach the target position from the determined remaining distance to the surgical target, and may provide a sense of the correction displacement distance via the user interface. Perceived Possible Nand configured to output the representation, receive a further confirmation signal from the user via the user interface, and upon receiving the further confirmation signal, control the actuator to actuate the movable arm portion to cause a further single movement of the surgical instrument along the longitudinal axis over the correction displacement distance. In the limited closed-loop control mode, the processor subsystem may be limited by at least one of a predefined duration of use of the limited closed-loop control mode, a predefined maximum correction displacement distance, requiring the certainty score to remain above a certainty score threshold during the correction (the certainty score representing the certainty of the determined remaining distance), and requiring continuous user input during the correction, and ceasing the movement of the surgical instrument upon detecting that the continuous user input has ended. Using the certainty score to select the control mode may ensure a greater degree of automation in some cases, e.g., when the certainty score is high, while a greater involvement of user input is required, e.g., when the certainty score is low.

[0022] Optionally, the processor subsystem, prior to receiving a confirmation signal from the user, transmits, via a user interface, a sense of the calculated certainty score. Perceived Possible N You may output the expression. Sense of certainty score Perceived Possible N Providing a representation to the user indicates a level of confidence associated with the sensor reading and allows the user to either confirm or overrule the progression of the procedure. For example, if the confidence score indicates a low degree of confidence, the user may decide not to proceed with the single movement of the surgical instrument, and / or decide to update the sensor data again, etc.

[0023] Optionally, the sensor includes at least one of an optical coherence tomography (OCT) sensor configured to optically couple to an optical fiber attached to or embedded in the surgical instrument, intraoperative optical coherence tomography (iOCT) via a microscope, a stereo camera via a microscope, an optical interferometer sensor embedded in the surgical instrument, a time-of-flight sensor embedded in the surgical instrument, and an ultrasonic sensor embedded in the surgical instrument.

[0024] Optionally, the processor subsystem is further configured to obtain sensor data indicative of a distance between a first layer of ocular tissue and a second layer of ocular tissue, the surgical target being between the first layer and the second layer, and correcting the position of the surgical instrument such that the surgical instrument is between the first layer and the second layer. By determining the surgical instrument and the distance from each of the first and second layers, respectively, the system may determine whether the surgical instrument is between the two layers, which may improve positioning of the surgical instrument.

[0025] Optionally, the processor subsystem may acquire sensor data indicative of a distance between a first layer of ocular tissue and a second layer of ocular tissue, the surgical target being between the first layer and the second layer, and the data indicative of a target position of the surgical instrument relative to the surgical target including data indicative of a distance between the first layer and the second layer. Determining the distance between the layers of tissue can improve accuracy of positioning of the surgical instrument.

[0026] Those skilled in the art will appreciate that two or more of the above-described embodiments, implementations and / or aspects of the invention may be combined in any manner deemed useful.

[0027] Modifications and modifications of methods and / or computer program products corresponding to the described modifications and modifications of surgical robotic systems may be implemented by those skilled in the art based on this specification.

[0028] The invention is defined in the independent claims or clauses. Advantageous but optional embodiments are defined in the dependent claims or clauses.

[0029] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 shows a schematic diagram of a surgical robotic system. [Diagram 2] 1 shows a surgical instrument passing through a trocar during minimally invasive surgery. The surgical instrument has four degrees of freedom (DoF). [Diagram 3] FIG. 2 shows a joint diagram illustrating the motion characteristics of a movable arm portion of a surgical arm used in minimally invasive surgery. [Figure 4] A joint diagram showing the motion characteristics of a motion controller is shown. [Diagram 5] 1 illustrates an intraocular surgical instrument according to one embodiment of the present invention. [Figure 6A] 1 illustrates a surgical instrument in an initial position within the eye according to one embodiment of the present invention. [Figure 6B] 1 illustrates a surgical instrument after a single movement of the surgical instrument has been performed, according to one embodiment of the present invention. [Figure 7A] 2 illustrates a schematic diagram of a method for selecting a control mode according to an embodiment of the present invention; [Figure 7B] 4 illustrates a schematic of a method for selecting a control mode using a certainty score, according to an embodiment of the present invention; [Figure 8A] 4 illustrates thresholds for selecting a control mode, according to one embodiment of the present invention. [Figure 8B] 1 illustrates thresholds for selecting a control mode and / or triggering an abort procedure, according to one embodiment of the present invention. [Figure 9] 2 illustrates a schematic diagram of a method for triggering an abort procedure according to an embodiment of the present invention; [Figure 10A] 1 illustrates a surgical target between two layers of tissue prior to injection, according to one embodiment of the present invention. [Figure 10B] 1 shows a concave retina before injection, according to one embodiment of the present invention. [Figure 10C] 1 illustrates a surgical target between two layers of tissue during injection, according to one embodiment of the present invention. [Figure 11] 1 illustrates generally a method for controlling a surgical robotic system during use in an ophthalmic surgical procedure. [Figure 12] 1 illustrates a computer program product including instructions for causing a processor system to perform a method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] It should be noted that items having the same reference numbers in different figures have the same structural features and the same functions, or are the same signals. Where the function and / or structure of such items have been explained, there is no need to repeat the explanation in the detailed description.

[0032] List of Reference Numbers The following list of reference numbers is provided to aid in interpretation of the drawings and is not to be construed as limiting the claims or sections. 020 User Interface 022 User Input 030 Sensor 032 Sensor Data 040 Processor Subsystem 042 Activation Command 060 Actuator 062 Surgical Arm Operation 080 Surgical Arm 082 Movable arm part 100 Surgical Robot System 101 e → 1. Axes of the Cartesian coordinate system 102 e → y , the axes of the Cartesian coordinate system 103 e → z , the axes of the Cartesian coordinate system 104 e → x , an axis of a coordinate system fixed to the tip of the instrument, perpendicular to the longitudinal axis of the instrument 105 e → y , an axis of a coordinate system fixed to the tip of the instrument, perpendicular to the longitudinal axis of the instrument 106 e → z , an axis of a Cartesian coordinate system aligned with the instrument longitudinal axis 107 φ, rotation of a surgical instrument that displaces its tip laterally 108 ψ, rotation of a surgical instrument to laterally displace its tip 109 z, the longitudinal translation (along its longitudinal axis) of the surgical instrument, or the direction of penetration or advancement 110 θ, rotation of the surgical instrument about its longitudinal axis 111 Φ, rotational freedom of the movable arm 112 Ψ, rotational degree of freedom of the movable arm 113 Z, translational degree of freedom of the movable arm 114 Θ, rotational freedom of the movable arm 115Φ m , rotational degrees of freedom of the motion controller 116 Ψ m , rotational degrees of freedom of the motion controller 117 Zetas m , the translational degree of freedom of the motion controller 118 Θ m , rotational degrees of freedom of the motion controller 119 Surgical instruments 121 Distance Sensor 122 Surgical instrument tip 123 Surgical Target 124 Trocar 125 Remote Motion Center (RCM) 126 Buttons on the Motion Controller Gripper 127 Light Beam 200 eyes 210 Retina 220 First Layer of Organization 230 Second Layer of Organization 240 Bleb How to select the 700 control mode 710 Calculate the certainty score 720 Compare the certainty score to a first threshold 730 Decision Block 740 Selecting the Motion Controller-Based Control Mode 744 Compare the certainty score to a second threshold 746 Decision Block 750 Selecting the Displacement-Based Control Mode 760 Selecting the limit closed loop control mode 810 Motion controller-based control mode 820 Displacement-based control mode 830 Limited closed loop control mode 840 Suspension Procedure How to trigger a 900 abort procedure 910 Calculate the certainty score 920 Compare the certainty score to a threshold 940a Continue moving surgical instruments 940b Continuing ophthalmic surgical procedures 950 Implementing the interruption procedure 1100 Method for controlling a surgical robotic system 1110 Get sensor data 1120 Determine the initial distance 1130 Acquire target location for surgical target 1140 Determine the Displacement Distance 1150 Output the displacement distance 1160 Receive user confirmation 1170 Actuate a movable arm to move in a single motion 1150 Non-transient program code 1160 Computer-readable medium

[0033] FIG. 1 illustrates a schematic of a surgical robotic system 100 for use in a surgical procedure. The surgical robotic system 100 includes a surgical arm 080. The surgical arm 080 includes a movable arm portion 082, which includes an instrument connector 119 for attaching a surgical instrument. FIG. 1 illustrates the surgical instrument 119 attached to the instrument connector (for simplicity, the instrument connector is not shown separately in FIG. 1). The movable arm portion 082 has at least one degree of freedom (DoF) that allows longitudinal movement of the surgical instrument toward a surgical target. Here, longitudinal movement refers to movement of the surgical instrument 119 along its longitudinal axis (for simplicity, the longitudinal axis is not shown separately in FIG. 1).

[0034] The surgical robotic system 100 further includes a user interface 020 for receiving input from a user. The user input 022 may include positioning commands from a human operator, e.g., a surgeon or healthcare provider, a confirmation input indicating an instruction to continue a procedure or step of a procedure, and / or input information, e.g., indicative of operational parameters and / or an indication of a surgical target location, for controlling longitudinal movement of the surgical instrument. Examples of user interfaces include, but are not limited to, a keyboard, a mouse, a touch-sensitive surface, a joystick, a foot pedal, a microphone, a gesture recognition system, and the like. The user interface may use any suitable input modality, such as touch, push actions, voice commands, eye movements, gesture recognition, and the like.

[0035] The surgical robotic system 100 further includes an actuator 060 configured and arranged to actuate the movable arm portion 060 to effect longitudinal movement of the surgical instrument. The actuator 060 may be any suitable actuator, for example, from the field of surgical robotics or more generally. In particular, the actuator may be one of a plurality of actuators that together provide actuation of the movable arm portion 060 along at least one DoF. That is, the surgical robotic system 100 may include a plurality of actuators, for example, to provide actuation along a plurality of DoFs. It will be understood that any reference to a configuration of the actuator 080 may therefore be understood as a reference to a (coupled) configuration of such a plurality of actuators. FIG. 1 illustrates the actuation of the surgical arm 080 diagrammatically, i.e., as a dashed line 062. It should be noted that, although shown separately from the surgical arm 080, the actuator 060 may be built into or attached to the surgical arm 080.

[0036] The surgical robotic system 100 further includes a sensor 030 configured and arranged to acquire sensor data 032 indicative of a distance between the surgical instrument 119 and the surgical target. The sensor 030 may include at least one of an optical coherence tomography (OCT) sensor configured to optically couple to an optical fiber attached to or embedded in the surgical instrument 119, an intraoperative optical coherence tomography (iOCT) via a microscope, a stereo camera via a microscope, an optical interferometer sensor embedded in or attached to the surgical instrument 119, a time-of-flight sensor embedded in or attached to the surgical instrument 119, and an ultrasonic sensor embedded in or attached to the surgical instrument 119. The surgical instrument may be an irrigation / aspiration instrument for irrigating or aspirating fluids at a desired target location, a photocoagulation instrument for applying optical energy at a desired distance from the target, a vitrectomy instrument for cutting and aspirating vitreous or other fluids at a desired distance from the target, a tissue manipulation instrument that needs to be precisely positioned at a first interface of tissues, etc. In some embodiments, the surgical robotic system 100 may include, for example, a stereo camera and / or a microscope configured to provide iOCT. In some embodiments, the microscope may be communicatively coupled to the surgical robotic system 100. In some embodiments, the sensor data 032 may include an A-scan, which includes line measurements and is defined as intensity as a function of distance, a B-scan that forms a two-dimensional image, a C-scan, for example, with multiple B-scans, etc. Distance may be derived from any of these scan types using, for example, image analysis. In some embodiments, the sensor 030 may include an optical sensor and the sensor data 032 may include diffuse reflectance. In some embodiments, the sensor 030 may include a stereo camera and the sensor data 032 may include two two-dimensional images to obtain a depth map.

[0037] The surgical robot system 100 further includes a processor subsystem 040 configured to control the actuator to actuate the movable arm portion to move the surgical instrument 119 along the longitudinal axis. When the surgical instrument 119 is in the initial position, the processor subsystem 040 may acquire sensor data 032 from the sensor 030. The sensor data 032 may be indicative of a distance between the surgical instrument 119, for example, a tip 122 (shown in FIG. 2) of the surgical instrument 119, and a surgical target 123 (shown in FIG. 2). In other words, the sensor data 032 may be used to determine a distance between the surgical instrument and the surgical target. In some embodiments, the sensor data 032 is acquired while the surgical instrument is stationary to improve the reliability of the measurements. In some embodiments, the sensor 030 may be configured to acquire sensor data 032 indicative of a distance between multiple layers of eye tissue. That is, the sensor 030 may be configured to determine a distance between the surgical instrument and a first layer of tissue and a distance between the surgical instrument and a second layer of tissue.

[0038] The processor subsystem 040 may be configured to obtain data indicative of a target position of the surgical instrument relative to the surgical target. The position of the surgical target itself may be determined from sensor data, for example from internal or external sensors, but alternatively or additionally may also be determined by user input. The data indicative of the target position may typically be obtained from user input, but alternatively or additionally may also be determined automatically. In general, the target position may be a relative position with respect to the surgical target. In some embodiments, the target position may be defined as a one-dimensional position on a line from the surgical instrument to the surgical target. That is, the target position may be defined as a longitudinal position. Such a target position may also be referred to as a "depth", for example if the target position is longitudinally beyond the surgical target, or as a "proximity", for example if the target position is longitudinally in front of the surgical target. In some embodiments, the target position may be defined as a specified distance from the surgical target. Whether the target position is longitudinally beyond or in front of the surgical target may be indicated by a symbol of the specified distance. The target location may also have any other dimensions, such as a three-dimensional location in a polar or Cartesian coordinate system. In some embodiments, the user may be requested to input the target location graphically, for example by providing an input on a graphical user interface, from which the processor subsystem 040 may then determine the target location numerically. In other embodiments, the user may be requested to input the target location directly in numerical form, for example by providing a numerical input indicating a distance relative to the surgical target. In some embodiments, where the surgical target is a layer of tissue, the target location may be provided as a relative position or depth from the layer of tissue. The layer of tissue may be, for example, a layer of vitreous tissue or a layer of retinal tissue.

[0039] The processor subsystem 040 may be configured to determine a displacement distance of the surgical instrument based on the sensor data and the target position. For example, the displacement distance may be a function of the difference between the initial position and the target position. In some embodiments, the displacement distance may be a partial distance between the initial position of the surgical instrument and the target position. In other embodiments, the displacement distance may be a total distance between the initial position of the surgical instrument and the target position.

[0040] The processor subsystem 040 may communicate via the user interface 020 the sense of the determined displacement distance. Perceived Possible N The sensor may be configured to output a representation of the determined displacement distance. Perceived Possible N The representation may include a graphical representation of the determined displacement distance, e.g., visually overlaid on an image of the surgical field, an audio output, e.g., via a speaker of the user interface 020, and / or a visual numerical output, e.g., on a display of the user interface 020. Perceived Possible N The representation may be rounded to a specified level of precision.

[0041] The processor subsystem 040 may be configured to receive a confirmation signal from a user via the user interface. The confirmation signal may be received as audio input, for example, via a microphone of the user interface 020, touch or click input, for example, on a graphical user interface of the user interface 020, input to a motion controller, foot pedal input, gesture-based input, for example, via a camera of the user interface 020, etc. The user interface 020 may be configured to receive one or more types of inputs of the confirmation signal.

[0042] Upon receiving the confirmation signal, the processor subsystem 040 may be configured to control the actuator to actuate the movable arm to cause a single movement of the surgical instrument along the longitudinal axis over the determined displacement distance. That is, once the user confirms the determined displacement distance, the surgical instrument is moved over the determined displacement distance in a single uninterrupted movement. The single movement of the surgical instrument may be referred to as a continuous movement or an uninterrupted movement. In some embodiments, the surgical instrument may move towards the surgical target only if the user confirms the determined displacement distance.

[0043] In some embodiments, the surgical robotic system 100 may be configured to perform a correction procedure. Upon completing a single movement of the surgical instrument, the processor subsystem 040 may be configured to obtain the latest sensor data 032 from the sensor 030 and determine the remaining distance between the surgical instrument and the surgical target based on the latest sensor data 030. In other words, after the surgical instrument moves the determined displacement distance to the second position, the latest sensor data is obtained while the surgical instrument is at the second position. In some embodiments, the latest sensor data is obtained while the surgical instrument is stationary to improve the reliability of the measurements. The processor subsystem 040 may be configured to determine whether the target position has been reached based on the determined remaining distance. If the processor subsystem 040 determines that the surgical instrument has not reached the target position, the processor subsystem 040 may control the actuator to correct the depth of the surgical instrument based on the determined remaining distance. In some cases, movement of the surgical instrument and / or eye, such as changes in intraocular pressure or patient movement, may displace the target position. In some cases, the initial sensor measurements may be slightly inaccurate, leading to an inaccurate displacement distance, ultimately resulting in the surgical instrument moving either too short or too long, either not reaching the target location or overshooting the target location, In such cases, the depth, e.g., position, of the surgical instrument may be corrected based on the determined remaining distance.

[0044] The processor subsystem 040 may control the actuator in one or more control modes, for example based on the certainty score, as described in detail with reference to Figures 7-9. In some embodiments, the control modes, as described with reference to Figures 7-9, may be manually selected.

[0045] 2 shows a surgical instrument 119 passing through a trocar 124 during minimally invasive surgery. For example, for vitreoretinal surgery, the trocar 124 may be placed on the sclera. Rotation around and translation within the trocar may be possible in four degrees of freedom, e.g., rotation φ 107, rotation ψ 108, rotation θ 110, and translation z 109, to approach or penetrate a surgical target 123. Also shown is the tip 122 of the surgical instrument 119 and the three axes 104-106 of a coordinate system fixed to the instrument tip 122,

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[0046] The surgical robot system 100 may be used in ophthalmic surgical procedures, such as minimally invasive surgical procedures as described above. FIG. 3 shows a joint diagram illustrating the kinematic characteristics of a movable arm section of a surgical arm for use in ophthalmic surgical procedures, particularly minimally invasive surgery. In the example of FIG. 3, the surgical robot system includes a surgical arm that includes movable arm sections having DoFs Φ 111, Ψ 112, Ζ 113, and Θ 114 that enable respective instrument motions 107-110 and cause movement of a surgical instrument tip 122. The DoFs may be arranged such that there is a point on the surgical instrument that does not move in space, referred to as the remote center of motion (RCM) 125. By moving the base of the surgical arm, the movable arm section may be arranged such that its RCM 125 may be placed on a trocar. Each actuation unit may be arranged to cause movement in all four degrees of freedom 111-114.

[0047] The surgical robotic system may further include a user interface for receiving user input, such as positioning commands, from a human operator, e.g., a surgeon or healthcare provider. In some embodiments, the user interface may include or consist of a motion controller, such as a joystick. In some embodiments, the motion controller may be an external device with which the user interface or processor subsystem 040 is configured to interface. In some embodiments, the motion controller may be included in the surgical robotic system, e.g., as a further component configured to interface with the processor subsystem 040 and / or the user interface 020. FIG. 4 shows a joint diagram illustrating the kinematic characteristics of such a motion controller. Here, the motion controller is configured to operate in a DoF Φ m 115, Psi m 116, Z m 117 and Θ m118. A user may provide user input, such as a positioning command, by, for example, grasping the gripper portion of the motion controller, pressing a button 126, and moving the gripper portion of the motion controller in 3D space.

[0048] 5 illustrates a surgical instrument 119 within an eye 200, according to one embodiment of the present invention. The tip 122 of the surgical instrument 119 is also shown enlarged.

[0049] As depicted on the left hand side of Figure 5, a surgical instrument 119 is shown inserted into the eye 200. As shown in this figure, the surgical instrument 119 may access the retina 210, however, this is by way of example only and the invention is not limited thereto. In some embodiments, the surgical instrument 119 may access another region, structure or tissue layer of the eye.

[0050] The tip 122 of the surgical instrument 119 is shown enlarged on the right hand side of FIG. 5. In this example, the surgical target 123 is located at the retina. The surgical instrument may be an irrigation / aspiration instrument for irrigating or aspirating fluid at a desired target location, a photocoagulation instrument for applying light energy at a desired distance from the target, a vitrectomy instrument for cutting and aspirating vitreous or other fluids at a desired distance from the target, a tissue manipulation instrument that needs to be precisely positioned at the first interface of tissues, etc. The tip 122 of the surgical instrument 119 may be an injection lumen. A sensor or sensor component 121, such as an optical fiber, may be built into or attached to the surgical instrument 119. In some embodiments, the sensor 030 may include an optical fiber (as shown) configured to acquire sensor data 032 indicative of a distance D between the surface of the retina 210 and the tip 122 of the surgical instrument 119. The optical fiber 121 may be recessed from the tip 122 of the surgical instrument 119. In some embodiments, the sensor 030 may be configured to determine the distance between the end of the optical fiber 121 and the surface of the retina 210, and then subtract an offset corresponding to the distance the optical fiber 121 is recessed from the tip 122 of the surgical instrument 119 to obtain the distance D. In some embodiments, the distance D may be determined using the light beam 127. Because the optical fiber 121 is recessed from the tip 122 of the surgical instrument 119, it is advantageously possible to obtain sensor data while the tip 122 of the surgical instrument 119 is piercing or penetrating a tissue layer.

[0051] The distance D between the surface of the retina 210 and the tip 122 of the surgical instrument 119 may be used to determine the distance between the tip 122 of the surgical instrument 119 and the surgical target 123. For example, the surgical target 123 may be a layer of the retina 210 of a known depth or a surface thereof, and the distance between the tip of the surgical instrument and the surgical target 123 may be determined by adding the known depth of the surgical target 123 to the distance D between the tip 122 of the surgical instrument 119 and the surface of the retina 210.

[0052] In some embodiments, the target location may correspond to a surface of the retina 210. More generally, the target location may be determined based on the location or detection of a structure or tissue layer, such as the surface of the retina 210.

[0053] The above examples have primarily referred to the distance between the tip 122 of the surgical instrument 119 and, for example, the surface of the retina 210. However, it should be understood that the invention is not so limited. In some embodiments, the distance may be measured from another portion of the surgical instrument 119 instead of or in addition to the tip 122. For example, the distance may be determined relative to the position of an optical fiber, a marker on the surgical instrument 119, etc.

[0054] FIG. 6A shows the surgical instrument 119 in an initial position within the eye 200, according to an embodiment of the present invention. As in FIG. 5, the surgical instrument 119 is shown approaching a point along the surface of the retina 210. It is reiterated here that this surgical target selection is merely exemplary. The methods and systems disclosed herein apply equally regardless of the surgical target selection. FIG. 6A shows the surgical instrument 119 in an initial position, at a distance D(initial) from the surgical target 123. While in the initial position, the distance D(initial) may be determined, for example, using a sensor 030 coupled to, attached to, or embedded in the surgical instrument 119, as shown in FIG. 5. Preferably, the sensor measurement is taken while the surgical instrument 119 is stationary. Once the distance between the surgical instrument 119, for example the tip 122 of the surgical instrument 119, and the surgical target 123 is known, a displacement distance may be determined. The displacement distance is the distance the surgical instrument 119 is configured to move, and may be defined as the distance between the surgical instrument 119 and the target location. The displacement distance may be the (e.g., total) distance to the surgical target 123, or the displacement distance may be less than the distance to the surgical target 123. For example, if the surgical target 123 is located in a particularly complex and / or delicate portion of the eye 200, or if it is difficult to read the position of the surgical target 123 using a sensor, it may be advantageous to first move the surgical instrument 119 a first distance to a next position where more reliable sensor data may be obtained. Selecting a displacement distance that is less than the initial distance between the surgical instrument 119 and the surgical target 123 may be further advantageous if movement of the eye 200 or patient is likely to occur during instrument movement, e.g., if structures within the eye 200 and / or the surgical target 123 are likely to move as a result of the movement of the surgical instrument.

[0055] The displacement distance may be determined by obtaining a user input indicating a target location of the surgical instrument, such as, for example, on a graphical user interface, an input specifying a target depth or even indicating a specific target location. In some embodiments, the target location may correspond to a surgical target, and the user may simply indicate that the target location is the location of the surgical target. In some embodiments, the displacement distance may be determined using a predefined setting, such as a defined offset from the surgical target. Such an offset may be, for example, 2 mm in front of the surgical target. In some embodiments, the displacement distance may be determined automatically, for example, based on detection of one or more anatomical structures, tissue layers, etc., or based on noise in the sensor data. For example, if the sensor data is noisy, a shorter displacement distance may be determined. In some embodiments, the displacement distance may be determined automatically, for example, based on an initial distance, such as to cover a predefined portion of the initial distance.

[0056] Once the displacement distance is determined, the surgical robotic system 100 may be configured to output a sensory perceptible indication of the determined displacement distance. The user is requested to confirm the determined displacement distance before the surgical instrument 119 may be moved. Requiring user confirmation of the determined displacement distance allows the user to be assured that the value determined by the system 100 is valid. That is, risks associated with moving the surgical instrument over an inappropriate (e.g., too far or unnecessarily short) distance may be mitigated, since inaccurate or noisy sensor data or detections may result in an inaccurate displacement distance. This step also directly involves the user in moving the surgical instrument 119, eliminating some of the discomfort typically associated with automation in this field, without incurring risks associated with hand tremors, vibrations, etc.

[0057] User confirmation may be provided, for example, by clicking a button on a mouse or motion controller, such as in a graphical user interface, pressing a foot pedal, verbal confirmation using a microphone and voice recognition, gesture recognition of a gesture captured using a camera configured for gesture capture, or any combination thereof, etc. Some or all of these user interaction means may be incorporated into or used through the user interface.

[0058] Upon acquisition of the user confirmation signal, the surgical instrument 119 may be moved the determined displacement distance in a single movement. That is, the movement of the surgical instrument 119 over the determined displacement distance may be without pauses or interruptions. The new position of the surgical instrument 119 is shown in FIG. 6B. In some embodiments, the movement of the surgical instrument 119 over the determined displacement distance may be performed at a constant velocity or constant acceleration, or the velocity or acceleration of the surgical instrument 119 may be non-linear.

[0059] In some embodiments, aspects of the movement of the surgical instrument 119, such as speed, acceleration, etc., may be adapted based on the certainty score. The certainty score may represent the certainty of the determined distance between the surgical instrument and the surgical target and / or the certainty of the acquired sensor data 032. The certainty score may also be referred to as a confidence score, which represents the reliability of the determined distance and / or the sensor data 032, or a reliability score, which indicates the reliability of the measurement or calculation, for example, of the determined distance or the acquired sensor data. In other words, the certainty score is a quantifiable measure of the accuracy and reliability of the measurement. That is, the certainty score may represent the certainty of the initial distance between the surgical instrument 119 and the surgical target (e.g., before moving the surgical instrument 119), or the certainty of the determined displacement distance between the surgical instrument 119 and the target position (e.g., before moving the surgical instrument 119). For example, the certainty score may be low due to measurement noise, measurement artifacts, and / or the sensor being at least partially occluded, for example, by debris in the eye. The certainty score may be calculated based on at least one of noise associated with the acquired sensor data, motion of the surgical target, a comparison of the sensor data to a reference model, and a comparison of the estimated surgical target position to a predicted position of the surgical target.

[0060] The predicted surgical target location may be based on instrument movement within robot coordinates as measured by at least one robot position sensor. In some embodiments, the robot 080 may include suitable position sensors and may be used to determine instrument movement.

[0061] Any known statistical method for determining certainty may be used in calculating the certainty score based on one or more of the above considerations, and may be the output of a template matching algorithm, a Kalman filter, a Bayes filter, and / or a machine learning algorithm.

[0062] When the certainty score is high, the surgical instrument 119 may be controlled to move, for example, at a faster speed than when the certainty score is low. Moreover, when an initial certainty score is calculated, the target location may be determined, at least in part, based on the certainty score. For example, when the initial certainty score is low, e.g., below a threshold, the displacement distance may be shorter than when the initial certainty score is high (e.g., above a threshold). The certainty score may also be used to select a control mode, as will be further elucidated with reference to FIG. 6B.

[0063] In some embodiments, the certainty score may be calculated prior to a single movement of the surgical instrument 119. That is, a sensory perceptible indication of the determined displacement distance as well as a sensory perceptible indication of the certainty score may be output to the user prior to the user providing a confirmation signal. In this manner, the user may or may not confirm the determined displacement distance while also taking into account the associated certainty score. In some embodiments, the determined displacement may be limited as a result of the certainty score. For example, if the certainty score is low, e.g., below a threshold, the determined displacement distance may be shortened to prevent the surgical instrument 119 from reaching a potentially dangerous or uncertain area.

[0064] FIG. 6B illustrates the surgical instrument after a single movement of the surgical instrument 119 has been performed, according to one embodiment of the present invention.

[0065] In some embodiments, the target position may have shifted due to, for example, movement of fluids or structures within the eye during a single movement of the surgical instrument 119. In such a case, a correction procedure may be performed to correct the position of the surgical instrument 119. That is, the sensor 030 may be configured to obtain updated sensor data 030' indicating the distance between the surgical instrument 119 at a current position (e.g., the position of the surgical instrument 119 after a single movement has been performed) and the surgical target 123. The processor subsystem 040 of the surgical robotic system 100 may then be configured to determine the remaining distance D(remaining) between the surgical instrument 119 and the surgical target 123.

[0066] The processor subsystem 040 may then be configured to determine whether the target location has been reached based on the determined remaining distance. If the remaining distance between the surgical instrument 119 and the surgical target 123 is determined to be the same or approximately the same as the distance between the target location and the surgical target, the processor subsystem 040 may determine that the target location has indeed been reached. If the remaining distance does not match the distance between the target location and the surgical target, for example, if the remaining distance does not fall within a predetermined margin, the processor subsystem 040 may determine that the target location has not been reached. Not reaching the target location may include, for example, passing the target location or not reaching the target location.

[0067] If the processor subsystem 040 determines that the target location has not been reached, it moves the surgical instrument to correct the depth of the surgical instrument. That is, the processor subsystem 040 may determine a correction distance from the target location based on the determined remaining distance to the surgical target. The correction distance may be the same as the determined remaining distance, for example, if the target location corresponds to the surgical target, but this need not be the case. In some embodiments, the target location may be closer to the surgical instrument 119 than the surgical target 123, and the remaining distance between the surgical instrument 119 and the surgical target 123 may not correspond to the correction distance. In such a case, the correction distance may be determined based on the remaining distance. For example, the target location may be a distance Y from the surgical target 123, and the remaining distance D(remaining) between the surgical target 123 and the surgical instrument 119 may be Y+Δz, e.g., D(remaining)=Y+Δz, and therefore the correction distance may be determined to be Δz. That is, the remaining distance may be considered as the sum of the distance between the target location and the surgical target and the correction distance. If the target location has been passed, the correction distance may be negative, indicating that the surgical instrument 119 should be retracted a distance Δz. The correction process may be repeated, as necessary, until the target location is reached.

[0068] However, if the processor subsystem 040 determines that the target location has been reached, it can be determined that the surgical instrument 119 is properly positioned at the target location.

[0069] The compensation procedure may be performed in a control mode selected from a displacement-based control mode, a limited closed-loop control mode, and a motion controller-based control mode. However, in some embodiments, the surgical robotic system 100 may be configured with only one or two of these control modes. For example, in some embodiments, the system 100 may be configured to select only two of these three modes.

[0070] Displacement-Based Control Mode The displacement-based control mode is similar to the level of automation and control provided during the initial movement of the surgical instrument 119: a displacement distance is determined (e.g., based on data indicative of the target position), a sensory perceptible indication of the determined displacement distance is output to the user, and the user is requested to confirm the determined displacement distance before movement of the surgical instrument can occur. That is, in the displacement-based control mode, a displacement distance is determined, this distance is proposed to and approved by the user (typically a surgeon), and then the movement is automatically performed.

[0071] If the displacement-based control mode is selected for the correction procedure, a correction distance (also referred to as a correction displacement distance) is determined, as described above. A sensory perceptible indication of the correction distance is output to a user, and a further confirmation signal is received from the user indicating confirmation of the determined correction distance. Upon receipt of the further confirmation signal from the user, the surgical instrument 119 is moved over the correction distance in one (e.g., continuous) movement. That is, the actuator 060 may be controlled to actuate the movable arm portion 082 to effect a further single movement of the surgical instrument 119 along the longitudinal axis over the correction displacement distance.

[0072] Limited closed loop control mode In the limited closed-loop control mode, control of the actuator 060 is more automated and requires less user involvement than control in the displacement-based control mode, i.e. - for a given duration using limited closed loop control mode, - a predetermined maximum correction displacement distance, - Requiring that the certainty score remain above the certainty score threshold during the correction; - Requiring continuous user input during the correction and ceasing movement of the surgical instrument when it is detected that the continuous user input has ended. may be limited by at least one of

[0073] In the limited closed-loop control mode, the movement of the surgical instrument 119 (e.g., actuation of an actuator) is determined automatically, for example, based on updates to sensor data and updates to a determined distance, for example, between the surgical instrument 119 and the surgical target 123. In other words, during movement of the surgical instrument 119, the sensor 030 may be configured to repeatedly obtain updated sensor data 032'' indicative of the distance between the surgical instrument 119 and the surgical target 123.

[0074] If the limited closed-loop control mode is time limited, the automatic movement control of the surgical instrument 119 may be disabled after a preset time. If the limited closed-loop control mode is displacement limited, the automatic movement control of the surgical instrument 119 may be disabled upon displacing the surgical instrument 119 a preset maximum corrective displacement distance.

[0075] If the limited closed-loop control mode depends on the certainty score, the processor 040 may be configured to repeatedly determine the certainty score as described above, for example, when updated sensor data 032'' is obtained, and compare the updating certainty score to a threshold certainty score. If the certainty score falls below the threshold certainty score, for example, when the updated sensor data 032'' is determined to be highly uncertain, the automatic control provided during the limited closed-loop control mode is disabled.

[0076] If the limited closed-loop control mode requires continuous actuation, while any user input is continuously detected, movement of the surgical instrument 119 may be automated until the user input is released. For example, the user may press a foot pedal to engage the limited closed-loop control mode, and movement of the surgical instrument 119 may be automatic until the user releases the foot pedal. In this example, a continuous user input of a foot pedal is described, but it will be recognized that this is merely exemplary. In some embodiments, continuous actuation may be provided by gaze detection, gesture capture, voice detection, or pressing of a trigger or similar button on a controller, or the like. For example, if voice detection is considered a user input indicating continuous actuation, the surgeon may be required to repeat a phrase at a predetermined frequency, such as once every 3 or 5 seconds.

[0077] Motion Controller Based Control Mode The motion controller-based control mode is the least automated control mode of the three control modes described herein and requires the most user involvement. In the motion controller-based control mode, the movement of the surgical instrument 119 (e.g., control of the actuator 060 that actuates the movable arm 082 to effect movement of the surgical instrument 119) is controlled by a user. The user may provide inputs, such as positioning commands, for example, via a motion controller or joystick, or similar inputs via the user interface 020. In the motion controller-based control mode, the user may control the movement of the surgical instrument 119, although effects such as hand tremors or vibrations may be reduced or even eliminated using solutions known in the art.

[0078] In some embodiments, the control mode used when correcting the position of the surgical tool 119 may be selected by the user or may be selected based on a calculated certainty score, the latter of which is described in further detail with reference to Figures 7A and 7B.

[0079] Returning now to Figures 6A and 6B, in some embodiments, upon determining that the target location has been reached, the process may be repeated. That is, the sensor 030 may obtain updated sensor data 032b indicating the distance between the surgical instrument 119 and the surgical target. The system 100 may further obtain data indicating a next target location that is different from the initial target location. For example, the user may indicate the next target location via a graphical user interface. The sensor data 032b obtained for the surgical instrument 119 in this current location may be more reliable than the original sensor data 030, allowing the user to more safely select a target location closer to the surgical target or to actually select the surgical target as the next target location. An updated displacement distance may then be determined based on the sensor data 032b and the next target location. Thereafter, a sensorily perceptible indication of the updated displacement distance may be output to the user, for example, via a user interface. Examples of sensorily perceptible outputs have already been provided with reference to Figures 1 and 5 and will not be repeated here for brevity. The user may again provide a further confirmation signal indicating confirmation of the updated displacement distance. Upon receipt of a further confirmation signal, the surgical instrument 119 may be moved in a single movement over the updated displacement distance.

[0080] This process may be repeated as necessary to reach the surgical target.

[0081] Throughout the above description, reference has been made to movement of the surgical instrument. It should be understood that the surgical instrument 119 is moved by controlling the actuator 060 to actuate the moveable arm 082, which effects movement of the surgical instrument 119.

[0082] 7A illustrates a method 700 of selecting a control mode, according to one embodiment of the present invention. In an operation entitled "Calculate Certainty Score," the processor subsystem 040 may calculate 710 a certainty score, which may be associated with sensor data acquired by the sensor and / or a distance determined based on the sensor data. For example, the certainty score may be calculated upon moving the surgical instrument 119 over a determined displacement distance when determining whether the surgical instrument 119 has reached the target location.

[0083] The processor subsystem 040 may then compare (720) the calculated certainty score to a first certainty score threshold in an operation entitled "Compare Certainty Score to First Threshold" of method 700. In some embodiments, the first certainty score threshold may be the only certainty score threshold. This is illustrated in FIG. 7A, currently being described. However, in other embodiments, there may be multiple certainty score thresholds, as will be elucidated with reference to FIGs. 7B, 8A, and 8B.

[0084] If it is determined in block 730 that the calculated certainty score is not higher than the first certainty score threshold, e.g., that the measurement or distance associated with the certainty score is uncertain or not sufficiently reliable, the method 700 proceeds to operation 740, entitled "Select Motion Controller Based Control Mode." That is, if the calculated certainty score is not higher than the first certainty score threshold, the actuator may be controlled using the motion controller based control mode described above. Thus, the user provides positioning commands to reduce the degree of automation associated with the movement of the surgical instrument 119. This may be due to noisy sensor data such that the system 100 cannot detect the surgical target with sufficient certainty or confidence.

[0085] If in block 730 the processor subsystem 040 determines that the calculated certainty score exceeds or meets the first certainty score threshold, the method may proceed to operation 750, entitled "Selecting a Displacement-Based Control Mode," or operation 760, entitled "Selecting a Limited Closed-Loop Control Mode." In some embodiments, the system 100, and in particular the actuator, may be configured to be controlled using one of two control modes when correcting the position of the surgical instrument 119. In some embodiments, the actuator 060 may be controlled in either a motion controller-based control mode or a displacement-based control mode. In other words, if the calculated certainty score is below the first certainty score threshold, the actuator 060 may be controlled in the motion controller-based control mode, and if the calculated certainty score is equal to or greater than the first certainty score threshold, the actuator 060 may be controlled in the displacement-based control mode. In some embodiments, the actuator 060 may be controlled in either a motion controller-based control mode or a limited closed-loop control mode. That is, if the calculated certainty score is below the first certainty score threshold, the actuator 060 may be controlled in a motion controller based control mode, and if the calculated certainty score is greater than or equal to the first certainty score threshold, the actuator 060 may be controlled in a limited closed loop control mode.

[0086] 7B, 8A and 8B, an embodiment will be described in which the actuator 060 can be controlled in either a motion controller based control mode, a displacement based control mode, or a limited closed loop control mode.

[0087] Figure 7B illustrates a schematic diagram of a variant 700' of the method 700 for selecting a control mode using a certainty score, according to an embodiment of the present invention. Figure 7B differs from Figure 7A in that a second certainty score threshold is used, which is higher than the first certainty score threshold. Operations 710, 720, 730 and 740 are the same as those described with respect to Figure 7A. For the sake of brevity, these operations will not be described again here, but only the differences between the method 700 of Figure 7A and the variant 700' of Figure 7B will be described.

[0088] If at block 730, the processor subsystem 040 determines that the calculated certainty score exceeds the first certainty score threshold, the method 700' proceeds to operation 744, entitled "Comparing Certainty Score to Second Threshold." At operation 744, the calculated certainty score is compared to a second certainty score threshold that is higher than the first certainty score threshold.

[0089] If in block 746 the processor subsystem 040 determines that the calculated certainty score exceeds the second certainty score threshold, the method 700' may proceed to operation 760, entitled "Select Limited Closed-Loop Control Mode", where the actuator 060 may be controlled using the limited closed-loop control mode described above.

[0090] If, at block 746, the processor subsystem 040 determines that the calculated certainty score does not exceed the second certainty score threshold, the method 700' may proceed to operation 750, entitled "Select Displacement-Based Control Mode," where the actuator 060 may be controlled using the displacement-based control mode described above.

[0091] These certainty score thresholds may be used to adapt the degree of automation of the movement of the surgical tool 119 based on the certainty associated with the sensor measurements and / or determined distances, as illustrated in FIG.

[0092] 8A, a motion controller based control mode 810 may be selected when the calculated certainty score falls below a first certainty score threshold CSThr1. If the calculated certainty score is above the first certainty score threshold CSThr1 but below a second certainty score threshold CSThr2, a displacement based control mode 820 is selected. If the calculated certainty score exceeds the second certainty score threshold CSThr2, a limited closed loop control mode 830 is selected. As mentioned above, the use of the second certainty score threshold is optional.

[0093] Although not shown, in some embodiments, the control mode for the actuator 060 may be selected from a displacement-based control mode and a limited closed-loop control mode. In other words, the first threshold CSThr1, and likewise operations 720 and 730, may be optional.

[0094] While in the above description the certainty score is used to select a control mode, in some embodiments a comparison of the certainty score to one or more thresholds may also or instead be used to control the actuator differently within the control mode, such as by controlling the maximum displacement or speed of movement of the surgical instrument 119. For example, the actuator may be operated in a limited closed loop control mode, but the maximum displacement of the surgical instrument 119 may be used and / or the speed of the surgical instrument 119 may be determined as a function of the certainty score based on the calculated certainty score. The function of the certainty score may be, for example, a step function (e.g., a first speed if the certainty score is below a first threshold, a second speed faster than the first speed if the certainty score is above the first threshold and optionally below a second threshold higher than the first threshold, and optionally a third speed faster than the second speed if the certainty score is above the second threshold, etc.) or a continuous function.

[0095] The certainty score may be used in a number of ways throughout an ophthalmic surgical procedure. To this end, Fig. 8B illustrates thresholds for selecting a control mode and / or for triggering an abort procedure, according to an embodiment of the present invention. The abort procedure itself is described in more detail with reference to Fig. 9.

[0096] In addition to, or as an alternative to, one or more certainty score thresholds described with reference to Figures 7A, 7B and 8A, a certainty score threshold may be used to trigger an abort procedure. Such a certainty score threshold may be referred to as a certainty score limit threshold, an abort threshold, or simply a certainty score threshold. Throughout the following description, the term "abort threshold" is employed.

[0097] The interruption threshold AbThr may be used without further certainty score thresholds, such as the certainty score thresholds described with reference to Fig. 8A. That is, in some embodiments, the only certainty score threshold used is the interruption threshold AbThr. However, in some embodiments, the interruption threshold AbThr may be used in conjunction with at least one further certainty score threshold CSThr1, CSThr2 for selecting a control mode.

[0098] The calculated certainty score may be compared to an abort threshold AbThr when it is calculated, such as during a correction procedure, or in embodiments where the certainty score is calculated during movement of the surgical instrument 119. The abort threshold AbThr may be lower than the threshold CSThr1 used to select the control mode. If the calculated certainty score falls below the abort threshold AbThr, an abort procedure 840 may be triggered. In some embodiments, the motion controller-based control mode 810 may be selected if the calculated certainty score is between the abort threshold AbThr and the first certainty score threshold CSThr1.

[0099] FIG. 9 illustrates generally a method 900 for triggering an abort procedure, according to an embodiment of the present invention.

[0100] The method 900 may include calculating 910 a certainty score in an operation titled "Calculating a Certainty Score." Calculating the certainty score may occur at any time during the ophthalmic surgical procedure, such as during or prior to movement of the surgical instrument 119 when determining whether the surgical instrument 119 has reached a target location. In some embodiments, the certainty score may be calculated each time sensor data or updated sensor data is obtained.

[0101] The method may further include comparing 920 the calculated certainty score to a certainty score threshold, e.g., an abort threshold AbThr, in an operation entitled "Comparing Certainty Score to Threshold." If, in block 930, it is determined that the certainty score meets or exceeds the certainty score threshold, the method may continue 940a the movement of the surgical instrument, or may continue 940b the ophthalmic surgical procedure. In some embodiments, the method 900 may be repeated from operation 910, e.g., a new certainty score may be calculated, such as when the sensor data is being repeatedly updated during movement of the surgical instrument 119. The method 900 need not be repeated immediately.

[0102] If the certainty score falls below the certainty score threshold, the method may proceed to operation 950, entitled "Perform Abort Procedure."

[0103] Suspension Procedure The abort procedure 950 includes the following actions: - retracting the surgical instrument 119; - pausing the movement of the surgical instrument 119; and - Switching from controlling the actuator in a limited closed-loop control mode to controlling the actuator in a motion controller-based control mode may include one or more of:

[0104] In particular, pausing the movement of the surgical instrument 119 may be performed in combination with any of the other actions listed. In some embodiments, updated sensor data may be acquired after pausing the movement of the surgical instrument 119. In some cases, more reliable sensor data may be acquired while the surgical instrument 119 is stationary. In such cases, it may be possible to resume the ophthalmic surgical procedure if an improved certainty score is calculated as a result of the updated sensor data.

[0105] In some embodiments, the abort procedure may include first pausing movement of the surgical instrument 119, acquiring new sensor data, calculating a new certainty score, and comparing the new certainty score to a certainty score threshold. If the new certainty score does not yet meet the certainty score threshold, the surgical instrument 119 may be retracted.

[0106] In some embodiments, the surgical instrument 119 may be retracted immediately upon determining that the abort procedure has been triggered.

[0107] In some embodiments, the surgical instrument 119 may be partially retracted, e.g., a short distance, or may be fully retracted, such as to return the surgical instrument 119 to its original position.

[0108] In some embodiments, the control mode for controlling the actuator 060 may be switched if the certainty score falls below the interruption threshold AbThr. For example, if the actuator is controlled in a limited closed-loop control mode and the certainty score falls below the interruption threshold AbThr, the control mode of the actuator 060 may be switched to either a displacement-based control mode or a motion-controller-based control mode. If the actuator 060 is controlled in a displacement-based control mode and the certainty score falls below the interruption threshold AbThr, the control mode of the actuator 060 may be switched to a motion-controller-based control mode.

[0109] FIG. 10A shows a surgical target between two tissue layers before injection according to one embodiment of the present invention, FIG. 10B also shows a sunken retina before injection according to one embodiment of the present invention, and FIG. 10C shows a surgical target between two tissue layers during injection.

[0110] In some embodiments, the sensor 030 may be configured to obtain sensor data 032 indicative of distances between the surgical instrument 119 and multiple tissue layers. As shown in FIG. 10A, a distance sensor 121, such as an optical fiber, may be attached, integrated, or coupled to the surgical instrument 119 and may be a component of the sensor 030. That is, the sensor 030 may include the distance sensor 121. The sensor 030, e.g., the distance sensor 121, may be configured to determine a first distance D1 between the surgical instrument 119, e.g., the tip 122 of the surgical instrument 119, and a first tissue layer 220 in the eye, and a second distance D2 between the surgical instrument 119, e.g., the tip 122 of the surgical instrument 119, and a second tissue layer 230 in the eye. Although the arrows indicating the distances D1, D2 are shown at different angles in FIG. 10A, this is merely for ease of illustration and the distances between the surgical instrument 119 and each layer 220, 230 may be determined along the same axis.

[0111] In some embodiments, the surgical target 123 may be found to be between two tissue layers 220, 230 of the eye, for example by being an intermediate tissue layer. However, contacting a first tissue layer 220 of the eye and moving a surgical instrument 119, for example to press against the first tissue layer 220, may indent the retina 210 and displace or deform the surgical target 123, as illustrated in FIG. 10B. The pressure of the surgical instrument on the first layer 220 may cause an indentation of the retina 210, as illustrated in FIG. 10B. In such a case, the determination of the first distance D1 between the surgical instrument 119 and the first tissue layer 220, as well as the determination of the second distance D2 between the surgical instrument 119 and the second tissue layer 230, may be used to improve the determination of the location of the surgical target 123. Although not shown in FIG. 7B, while the surgical instrument 119 is in contact with and / or pressing against the tissue layer 220, the sensor 030, e.g., the distance sensor 121, may be configured to acquire sensor data indicating the distance D1 between the surgical instrument 119 and the first tissue layer 220 and the distance D2 between the surgical instrument 119 and the second tissue layer 230.

[0112] In some embodiments, the system 100 may detect when the surgical instrument 119 reaches the first layer 220. For example, a target position may be determined to correspond to the first layer 220. Once this position is reached, the actuator 060 may be controlled to retract the surgical instrument 119 a distance x before advancing the surgical instrument 119, preferably at a higher speed, for example by a distance 2x, to improve the puncture / displacement ratio and thereby reduce retinal depression. Thus, the resulting displacement of the surgical instrument 119 will be a distance of x from the starting position. That is, the penetration of the tissue layer may be performed by advancing the surgical instrument 119 at a higher speed, for example with a high-speed puncture motion. The speed used with the high-speed puncture motion may be preset or the maximum speed of the surgical instrument 119 may be used.

[0113] In some embodiments, as illustrated in FIG. 10C, a bleb 240 may be formed upon injection of fluid into the retina 210. During the injection, the position of the surgical instrument 119 may be corrected. That is, the center of the bleb 240 may be determined, for example, based on determining the distance between the surgical instrument 119 and each of the two layers 220 and 230, while the surgical instrument 119 is injecting fluid between these two layers 220 and 230. The surgical instrument 119 may be retracted or extended to the bleb center.

[0114] 11 generally illustrates a method 1100 of controlling a surgical robotic system during use in an ophthalmic surgical procedure, the surgical robotic system including a surgical arm, the surgical arm including a movable arm section, the movable arm section including an instrument connector for attachment of a surgical instrument having a longitudinal axis, the movable arm section having at least one degree of freedom enabling longitudinal movement of the surgical instrument along the longitudinal axis of the surgical instrument toward or away from the ophthalmic surgical target, the surgical robotic system further including an actuator configured and arranged to actuate the movable arm section to effect longitudinal movement of the surgical instrument. The method 1100 includes, in an operation titled "Acquire Sensor Data", acquiring 1110 sensor data indicative of a distance between the surgical instrument and the surgical target when the surgical instrument is in an initial position. The method 1100 further includes, in an operation titled "Determine Initial Distance", determining 1120 an initial distance between the surgical instrument in the initial position and the surgical target based on the sensor data. The method 1100 further includes acquiring 1130 data indicative of a target position of the surgical instrument relative to the surgical target in an operation titled "Acquire Target Position Relative to the Surgical Target". The method 1100 further includes determining 1140 a displacement distance for the surgical instrument based on the sensor data and the target position in an operation titled "Determine Displacement Distance". The method 1100 further includes outputting 1150 a sensorily perceptible indication of the displacement distance to a user in an operation titled "Output Displacement Distance". The method 1100 further includes receiving 1160 a confirmation signal from a user in an operation titled "Receive User Confirmation". The method 1100 further includes controlling 1170 an actuator to actuate a movable arm portion to effect a single movement of the surgical instrument along a longitudinal axis over the displacement distance in an operation titled "Actuate Movable Arm". It should be noted that the operations of the method 1100 need not be performed strictly sequentially. For example, operations 1120 and 1130 may be performed in a different order or substantially simultaneously. Similarly, operations 1110 and 1120 may be performed in a different order or substantially simultaneously.

[0115] The method according to the invention may be realized on a processor as a computer-implemented method, or in dedicated hardware, or a combination of both. Executable code for the method according to the invention may be stored in a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, online software, etc. Figure 12 shows a computer program product in the form of a computer-readable medium 1260 including non-transitory program code 1250 for causing a processor to perform the method according to the invention when said program code is executed by a processor.

[0116] In a preferred embodiment, the computer program comprises computer program code means adapted to perform all the steps of the method according to the invention when the computer program is executed by a processor. Preferably, the computer program is embodied on a computer readable medium.

[0117] Throughout the above description, reference is made to various distances between the surgical instrument and the target location, surgical target, tissue layer, etc. These distances may each correspond to a distance between the tip of the surgical instrument and the target location, surgical target, tissue layer, etc. That is, the distances mentioned throughout this description may be taken from the tip of the surgical instrument, according to some embodiments.

[0118] It should be noted that the above-described embodiments are illustrative rather than limiting of the invention, and that those skilled in the art can design many alternative embodiments.

[0119] In a claim or clause, any reference signs placed between parentheses shall not be construed as limiting the claim or clause. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those listed in a claim or clause. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim or clause enumerating several means, several of these means may be embodied by one and the same hardware device. The mere fact that certain measures are recited in mutually different dependent claims or clauses does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. 1. A surgical robotic system (100) for use in an ophthalmic surgical procedure, comprising: a surgical arm (080) including a movable arm portion (082) including an instrument connector for attaching a surgical instrument (119) having a longitudinal axis, the movable arm portion (082) having at least one degree of freedom that allows longitudinal movement of the surgical instrument (119) along the longitudinal axis of the surgical instrument (119) towards or away from an ophthalmic surgical target (123); a sensor (030) configured to acquire sensor data (032) indicative of the distance between said surgical instrument (119) and said surgical target (123); a user interface (020) configured to receive user input from a user and to output a sensory perceptible output to said user; an actuator (060) constructed and arranged to actuate said movable arm (082) to effect said longitudinal movement of said surgical instrument (119); a processor subsystem (040), - acquiring sensor data (032) from the sensor (030) at an initial position of the surgical instrument (119) and determining an initial distance between the surgical instrument (119) and the surgical target (123) based on the sensor data (032); - obtaining data indicative of a target position of said surgical instrument (119) relative to said surgical target (123); - determining a displacement distance of said surgical instrument (119) advancing towards said surgical target (123) based on said sensor data (032) and said target position; - outputting, via said user interface (020), a sensory perceptible representation of said determined displacement distance, - requesting confirmation of said determined displacement distance from said user via said user interface (020); receiving, via said user interface (020), a confirmation signal indicating confirmation of said determined displacement distance from said user; upon receiving said confirmation signal, controlling said actuator (060) to actuate said moveable arm portion (082) to effect a single movement of said surgical instrument (119) along said longitudinal axis over said determined displacement distance; A processor subsystem (040) configured as follows: A surgical robot system (100).

2. The processor subsystem (040) further comprises: upon completing said single movement of said surgical instrument (119), obtaining updated sensor data (032') from said sensor (030) and determining, based on said updated sensor data (032'), a remaining distance between said surgical instrument (119) and said surgical target (123); determining whether the target location has been reached based on the determined remaining distance; If not, control the actuator (060) to correct the target position of the surgical instrument (119) based on the determined remaining distance.

2. The surgical robotic system (100) of claim 1, configured to:

3. The processor subsystem (040) - determining, from said determined remaining distance to said surgical target (123), a corrective displacement distance to reach said target position; - outputting, via said user interface (020), a sensory perceptible representation of said corrective displacement distance; - requesting confirmation of the determined corrective displacement distance from the user via the user interface (020), receiving a further confirmation signal from the user, via said user interface (020), indicating confirmation of said determined corrective displacement distance, upon receiving said further confirmation signal, controlling said actuator (060) to actuate said moveable arm portion (082) to cause a further single movement of said surgical instrument (119) along said longitudinal axis over said corrective displacement distance.

3. The surgical robot system of claim 2, further comprising: a actuator configured to control the actuator in a displacement-based control mode to correct the target position of the surgical instrument by a displacement-based control signal.

4. The processor subsystem (040) is configured to control the actuator (060) in a limited closed-loop control mode that uses updated sensor data (032) to correct the target position of the surgical instrument (119), and the automated movement control of the surgical instrument (119) in the limited closed-loop control mode comprises: - the preset time for using the limited closed-loop control mode has elapsed; a certainty score representative of the certainty of the determined remaining distance falls below a certainty score threshold; - User input is released, The surgical robot system of claim 2 , wherein the surgical robot system is disabled upon satisfaction of at least one of the following conditions:

5. The processor subsystem (040) further comprises: - calculating a certainty score representative of the certainty of the determined distance between said surgical instrument (119) and said surgical target (123); - modifying the manner of control of the actuators (060) depending on the calculated certainty score The surgical robot system (100) of any one of claims 2 to 4, configured as follows.

6. The surgical robot system (100) of claim 5, wherein the processor subsystem (040) is further configured to calculate the certainty score based on at least one of an estimate of measurement noise of the sensor (032) and detection of movement of the surgical target (123).

7. the processor subsystem (040) is configured to iteratively calculate the certainty score and to execute an abort procedure if the calculated certainty score falls below a certainty score threshold; The interruption procedure comprises: - retracting said surgical instrument (119); - pausing the movement of said surgical instrument (119); and - switching from controlling said actuator (060) in said limited closed-loop control mode to controlling said actuator (060) in a motion controller based control mode; and the processor subsystem (040) is configured to control the actuator (060) according to position control commands received from the user via a motion controller; A surgical robotic system (100) according to claim 5 when dependent on claim 4.

8. the processor subsystem (040) is further configured to select a control mode from a set of control modes based on the calculated certainty score, the set of control modes including at least two of a motion controller based control mode, a displacement based control mode, and a limited closed loop control mode; in the motion controller-based control mode, the processor subsystem (040) is configured to control the actuator (060) according to position control commands received from the user via a motion controller of the user interface (020); In said displacement-based control mode, said processor subsystem (040) - determining, from said determined remaining distance to said surgical target (123), a corrective displacement distance to reach said target position; - outputting, via said user interface (020), a sensory perceptible representation of said corrective displacement distance; - requesting confirmation of the determined corrective displacement distance from the user via the user interface (020), receiving a further confirmation signal from the user, via said user interface (020), indicating confirmation of said determined corrective displacement distance, upon receiving said further confirmation signal, controlling said actuator (060) to actuate said moveable arm portion (082) to cause a further single movement of said surgical instrument (119) along said longitudinal axis over said corrective displacement distance. It is structured as follows: In said limited closed loop control mode, said processor subsystem (040) - the preset time for using the limited closed-loop control mode has elapsed; a certainty score representative of the certainty of the determined remaining distance falls below a certainty score threshold; - User input is released, and disabling automatic movement control of the surgical instrument (119) when at least one of the following conditions is met: The surgical robotic system (100) of claim 5.

9. 6. The surgical robot system of claim 5, wherein the processor subsystem is further configured to output a sensory-perceptible representation of the calculated certainty score via the user interface prior to receiving the confirmation signal from the user.

10. The sensor (030) an optical coherence tomography (OCT) sensor configured to optically couple to an optical fiber attached to or embedded in said surgical instrument (119); - Microscope-assisted intraoperative optical coherence tomography (iOCT); - Stereo camera through a microscope, - an optical interferometric sensor integrated in or attached to said surgical instrument (119); - a time-of-flight sensor integrated in or attached to said surgical instrument (119), and - an ultrasonic sensor integrated in or attached to said surgical instrument (119); The surgical robot system (100) of any one of claims 1 to 4, comprising at least one of:

11. The processor subsystem (040) further comprises: acquiring sensor data (032) indicative of a distance between a first layer (220) of ocular tissue and a second layer (230) of said ocular tissue, said surgical target (123) being between said first layer (220) and said second layer (230); - correcting the position of the surgical tool (119) so that it is between the first layer (220) and the second layer (230); The surgical robot system (100) of any one of claims 1 to 4, configured as follows.

12. the processor subsystem (040) is further configured to acquire sensor data (032) indicative of a distance between a first layer (220) of ocular tissue and a second layer (230) of ocular tissue, the surgical target (123) being between the first layer (220) and the second layer (230); the data indicative of a target position of the surgical instrument (119) relative to the surgical target (123) includes data indicative of the distance between the first layer (220) and the second layer (230); A surgical robotic system (100) according to any one of claims 1 to 4.

13. 1. A computer program product (1250) comprising instructions for causing a processor system to execute a computer-implemented method (1100) for controlling a surgical robotic system (100) during use in an ophthalmic surgical procedure, the surgical robotic system (100) comprising a surgical arm (080) including a movable arm portion (082) including an instrument connector for attachment of a surgical instrument (119) having a longitudinal axis, the movable arm portion (082) including a surgical arm connector (112) for attaching a surgical instrument (119) having a longitudinal axis, the movable arm portion (082) including a surgical arm connector (112) for attaching a surgical instrument (119) having a longitudinal axis, the surgical arm connector (1 ... (082) includes a surgical arm (080) having at least one degree of freedom that enables longitudinal movement of the surgical instrument (119) along the longitudinal axis of the surgical instrument (119) toward or away from the ophthalmic surgical target (123), the surgical robotic system (100) further includes an actuator (060) configured and arranged to actuate the movable arm portion (082) to effect the longitudinal movement of the surgical instrument (119), the method comprising: - acquiring (1110) sensor data (032) indicative of the distance between the surgical tool (119) and the surgical target (123) at an initial position of the surgical tool; determining (1120) an initial distance between the surgical tool (119) in the initial position and the surgical target (123) based on said sensor data (032); - acquiring (1130) data indicative of a target position of said surgical instrument (119) relative to said surgical target (123); - determining (1140) a displacement distance of the surgical instrument (119) moving towards the surgical target (123) based on the sensor data (032) and the target position; - outputting (1150) a sensory perceptible representation of said displacement distance to a user; - requesting confirmation of the determined displacement distance from the user; receiving (1160) a confirmation signal from said user indicating confirmation of said determined displacement distance; upon receiving said confirmation signal, controlling (1170) said actuator (060) to actuate said movable arm portion (082) to effect a single movement of said surgical instrument (119) along said longitudinal axis over said displacement distance; A computer program (1250).

14. A computer-readable storage medium (1260) having recorded thereon the computer program (1250) described in claim 13.

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