Retinal Vein Cannulation Research Articles

Robotising vitreoretinal surgeries.

The use of robotic surgery in ophthalmology has been shown to offer many potential advantages to current surgical techniques. Vitreoretinal surgery requires complex manoeuvres and high precision, and this is an area that exceeds manual human dexterity in certain surgical situations. With the advent of advanced therapeutics such as subretinal gene therapy, precise delivery and minimising trauma is imperative to optimize outcomes. There are multiple robotic systems in place for ophthalmology in pre-clinical and clinical use, and the Preceyes Robotic Surgical System (Preceyes BV) has also gained the CE mark and is commercially available for use. Recent in-vivo and in-human surgeries have been performed successfully with robotics systems. This includes membrane peeling, subretinal injections of therapeutics, and retinal vein cannulation. There is huge potential to integrate robotic surgery into mainstream clinical practice. In this review, we summarize the existing systems, and clinical implementation so far, and highlight the future clinical applications for robotic surgery in vitreo-retina.

Evaluation of an Active Disturbance Rejection Controller for Ophthalmic Robots with Piezo-Driven Injector.

Retinal vein cannulation involves puncturing an occluded vessel on the micron scale. Even single millinewton force can cause permanent damage. An ophthalmic robot with a piezo-driven injector is precise enough to perform this delicate procedure, but the uncertain viscoelastic characteristics of the vessel make it difficult to achieve the desired contact force without harming the retina. The paper utilizes a viscoelastic contact model to explain the mechanical characteristics of retinal blood vessels to address this issue. The uncertainty in the viscoelastic properties is considered an internal disturbance of the contact model, and an active disturbance rejection controller is then proposed to precisely control the contact force. The experimental results show that this method can precisely adjust the contact force at the millinewton level even when the viscoelastic parameters vary significantly (up to 403.8%). The root mean square (RMS) and maximum value of steady-state error are 0.32 mN and 0.41 mN. The response time is below 2.51 s with no obvious overshoot.

A Data-Driven Model with Hysteresis Compensation for I2RIS Robot.

Retinal microsurgery is a high-precision surgery performed on a delicate tissue requiring the skill of highly trained surgeons. Given the restricted range of instrument motion in the confined intraocular space, snake-like robots may prove to be a promising technology to provide surgeons with greater flexibility, dexterity, and positioning accuracy during retinal procedures such as retinal vein cannulation and epiretinal membrane peeling. Kinematics modeling of these robots is an essential step toward accurate position control. Unlike conventional manipulators, modeling these robots does not follow a straightforward method due to their complex mechanical structure and actuation mechanisms. The hysteresis problem can especially impact the positioning accuracy significantly in wire-driven snake-like robots. In this paper, we propose a data-driven kinematics model using a probabilistic Gaussian mixture model (GMM) and Gaussian mixture regression (GMR) approach with a hysteresis compensation algorithm. Experimental results on the two-degree-of-freedom (DOF) integrated robotic intraocular snake (I2RIS) show that the proposed model with the hysteresis compensation can predict the snake tip bending angle for pitch and yaw with 0.45° and 0.39° root mean square error (RMSE), respectively. This results in overall 60% and 70% improvements of accuracy for yaw and pitch over the same model without the hysteresis compensation.

Cooperative vs. Teleoperation Control of the Steady Hand Eye Robot with Adaptive Sclera Force Control: A Comparative Study.

A surgeon's physiological hand tremor can significantly impact the outcome of delicate and precise retinal surgery, such as retinal vein cannulation (RVC) and epiretinal membrane peeling. Robot-assisted eye surgery technology provides ophthalmologists with advanced capabilities such as hand tremor cancellation, hand motion scaling, and safety constraints that enable them to perform these otherwise challenging and high-risk surgeries with high precision and safety. Steady-Hand Eye Robot (SHER) with cooperative control mode can filter out surgeon's hand tremor, yet another important safety feature, that is, minimizing the contact force between the surgical instrument and sclera surface for avoiding tissue damage cannot be met in this control mode. Also, other capabilities, such as hand motion scaling and haptic feedback, require a teleoperation control framework. In this work, for the first time, we implemented a teleoperation control mode incorporated with an adaptive sclera force control algorithm using a PHANTOM Omni haptic device and a force-sensing surgical instrument equipped with Fiber Bragg Grating (FBG) sensors attached to the SHER 2.1 end-effector. This adaptive sclera force control algorithm allows the robot to dynamically minimize the tool-sclera contact force. Moreover, for the first time, we compared the performance of the proposed adaptive teleoperation mode with the cooperative mode by conducting a vessel-following experiment inside an eye phantom under a microscope.

Liquid-Driven Microinjection System for Precise Fundus Injection.

Microinjection is usually applied to the treatment of some retinal disorders, such as retinal vein cannulation and displaced submacular hemorrhage. Currently, the microinjection procedure is usually performed by using the viscous fluid control of a standard vitrectomy system, which applies a fixed air pressure through foot pedal activation. The injection process with the fixed pressure is uncontrollable and lacks feedback, the high flow rate of the injected drug may cause damage to the fundus tissue. In this paper, a liquid-driven microinjection system with a flow sensor is designed and developed specifically for fundus injection. In addition, a PID sliding mode control (SMC) method is proposed to achieve precise injection in the injection system. The experimental results of fundus simulation injection demonstrate that the microinjection system meets the requirements of fundus injection and reduces the impact of the injection process on the fundus tissue.

Artificial Intelligence, Digital Imaging, and Robotics Technologies for Surgical Vitreoretinal Diseases

ObjectiveTo review recent technological advancement in imaging, surgical visualization, robotics technology and the use of artificial intelligence in surgical vitreoretinal (VR) diseases. BackgroundTechnological advancements in imaging enhance both pre-operative and intra-operative management of surgical VR diseases. Widefield imaging in fundal photography and optical coherence tomography (OCT) can improve assessment of peripheral retinal disorders like retinal detachments, degeneration, and tumors. OCT angiography provides a rapid and non-invasive imaging of the retinal and choroidal vasculature. Surgical visualization has also improved with intraoperative OCT providing a detailed real-time assessment of retinal layers to guide surgical decisions. Heads-up display and head-mounted display utilize three-dimensional technology to provide surgeons with enhanced visual guidance and improved ergonomics during surgery. Intraocular robotics technology allows for greater surgical precision and is shown to be useful in retinal vein cannulation and subretinal drug delivery. In addition, deep learning techniques leverages on diverse data including widefield retinal photography and OCT for better predictive accuracy in classification, segmentation, and prognostication of many surgical VR diseases. ConclusionThis review article summarized the latest updates in these areas and highlights the importance of continuous innovation and improvement in technology within the field. These advancements have the potential to reshape management of surgical VR diseases in the very near future and to ultimately improve patient care.

A Micro‐3‐Degree‐of‐Freedom Force Sensor for Intraocular Dexterous Surgical Robots

The continuum manipulator improves the intraocular robot flexibility during retinal surgery. Herein, a micro‐3‐degree of freedom (DOF) force sensor with a length of only 3.8 mm that can adjust the puncture angle during retinal vein cannulation (RVC) is proposed. Taking advantage of 3D printing technology, the optical fiber and injection line are embedded in the nitinol tube with flexible hinges to achieve integration of the force sensing and injection functions. A new fiber Bragg grating (FBG) configuration method and linear decoupling algorithm are also proposed herein. Static calibration experiments demonstrate excellent resolution of the force sensor, of less than 0.072 mN for transverse force and 0.738 mN for the axial force in the range from −20 to 20 mN. The proposed sensor is installed on a newly developed actuator, and an ex vivo experiment is performed on pig cadaver eyes. The interaction forces at each stage of the RVC are recorded in detail for the first time, further confirming the feasibility and effectiveness of the developed sensor for monitoring the RVC interaction forces.

Force and Velocity Based Puncture Detection in Robot Assisted Retinal Vein Cannulation: In-Vivo Study.

Retinal vein cannulation is a technically demanding surgical procedure and its feasibility may rely on using advanced surgical robots equipped with force-sensing microneedles. Reliable detection of the moment of venous puncture is important, to either alert or prevent the clinician from double puncturing the vessel and damaging the retinal surface beneath. This paper reports the first in-vivo retinal vein cannulation trial on rabbit eyes, using sensorized metal needles, and investigates puncture detection. We utilized total of four indices including two previously demonstrated ones and two new indices, based on the velocity and force of the needle tip and the correlation between the needle-tissue and tool-sclera interaction forces. We also studied the effect of detection timespan on the performance of detecting actual punctures. The new indices, when used in conjunction with the previous algorithm, improved the detection rate form 75% to 92%, but slightly increased the number of false detections from 37 to 43. Increasing the detection window improved the detection performance, at the cost of adding to the delay. The current algorithm can supplement the surgeons' visual feedback and surgical judgment. To achieve automatic puncture detection, more measurements and further analysis are required. Subsequent in-vivo studies in other animals, such as pigs with their more human like eye anatomy, are required, before clinical trials. The study provides promising results and the criteria developed may serve as guidelines for further investigation into puncture detection in in-vivo retinal vein cannulation.

Improved Integrated Robotic Intraocular Snake: Analyses of the Kinematics and Drive Mechanism of the Dexterous Distal Unit.

Retinal surgery can be performed only by surgeons possessing advanced surgical skills because of the small, confined intraocular space, and the restricted free motion of the instruments in contact with the sclera. Snake-like robots may be essential for use in retinal surgery to overcome this problem. Such robots can approach the target site from suitable directions and operate on delicate tissues during retinal vein cannulation, epiretinal membrane peeling, and so on. We propose an improved integrated robotic intraocular snake (I2RIS), which is a new version of our previous IRIS. This study focused on the analyses of the kinematics and drive mechanism of the dexterous distal unit. This unit consists of small elements with reduced contact stress achieved by changing wire-hole positions. The kinematic analysis of the dexterous distal unit shows that it is possible to control the bending angle and direction of the unit by using two pairs of drive wires. The proposed drive mechanism includes a new pull-and-release wire mechanism in which the drive pulley is mounted at a right angle relative to the actuation direction (also, relative to the conventional direction). Analysis of the drive mechanism shows that compared to the previous drive mechanism, the proposed mechanism is simpler and easier to assemble and yields higher accuracy and resolution. Furthermore, considering clinical use, the instrument of the I2RIS is detachable from the motor unit easily for cleaning, sterilization, and attachment of various surgical tools. Analyses of the kinematics and drive mechanism and the basic functions of the proposed mechanism were verified experimentally on actual-size prototypes of the instrument and motor units.

This issue of Acta Feb 2021

This issue of Acta Feb 2021

Automated Retinal Vein Cannulation on Silicone Phantoms Using Optical-Coherence-Tomography-Guided Robotic Manipulations.

Retinal vein occlusion is one of the most common causes of vision loss, occurring when a blood clot or other obstruction occludes a retinal vein. A potential remedy for retinal vein occlusion is retinal vein cannulation, a surgical procedure that involves infusing the occluded vein with a fibrinolytic drug to restore blood flow through the vascular lumen. This work presents an image-guided robotic system capable of performing automated cannulation on silicone retinal vein phantoms. The system is integrated with an optical coherence tomography probe and camera to provide visual feedback to guide the robotic system. Through automation, the developed system targets a vein phantom to within 20 μm and automatically cannulates and infuses the vascular lumen with dyed water. The system was evaluated through 30 experimental trials and shown to be capable of performing automated cannulation of retinal vein phantoms with no reported cases of failure.

Numerical Simulation of Thrombolysis in Robot-Assisted Retinal Vein Cannulation

Robot-assisted retinal cannulation is an eye surgical procedure which can dissolve the obstruction by using robot to inject anticoagulant into occluded vessel. The current research on the critical parameters of cannulation for human is scarce because of the immature technology. Considering the influence of microneedle, this work investigated the effects of drug concentration, injection velocity, injection position, and size of clot on cannulation by theoretical analysis and finite element analysis. For finite element analysis, the multiphysics continuum model was established to demonstrate species transport and reaction which simulates the entire lytic process of the occlusive clot, and four cell zones were established to describe the generation of plasmin (PLS) with the addition of tissue-type plasminogen activator (tPA) and fibrinolysis of clot by importing subroutines into each cell zone under the conditions of constant clot size and variable size, respectively. The results imply that the most efficient value of tPA concentration is 50 nM, injection velocity is 60 mm/s for clot length of 0.1 mm, and the best position to insert the cannula is 0.5 mm in front of the thrombus. For different clot lengths of 0.1 mm to 0.6 mm, the optimal range of tPA concentration and injection velocity is from 20 nM to 70 nM and from 40 mm/s to 60 mm/s, respectively, and explores the reasonable injection position of 0.3 mm to 0.5 mm in front of clot in a vein of 100 μm. This conclusion can be used to perform robot-assisted cannulation surgery to improve fibrinolytic efficiency.

Force-based Safe Vein Cannulation in Robot-assisted Retinal Surgery: A Preliminary Study.

Retinal vein cannulation (RVC) is a potential treatment for retinal vein occlusion (RVO). Manual surgery has limitations in RVC due to extremely small vessels and instruments involved, as well as the presence of physiological hand tremor. Robot-assisted retinal surgery may be a better approach to smooth and accurate instrument manipulation during this procedure. Motion of the retina and cornea related to heartbeat may be associated with unexpected forces between the tool and eyeball. In this paper, we propose a force-based control strategy to automatically compensate for the movement of the retina maintaining the tip force and sclera force in a predetermined small range. A dual force-sensing tool is used to monitor the tip force, sclera force and tool insertion depth, which will be used to derive a desired joint velocity for the robot via a modified admittance controller. Then the tool is manipulated to compensate for the movement of the retina as well as reduce the tip force and sclera force. Quantitative experiments are conducted to verify the efficacy of the control strategy and a user study is also conducted by a retinal surgeon to demonstrate the advantages of our automatic compensation approach.

Improved Integrated Robotic Intraocular Snake.

Retinal surgery can be performed only by surgeons possessing advanced surgical skills because of the small, confined intraocular space, and the restricted free motion of instruments in contact with the sclera. Snake-like robots could be essential for use in retinal surgery to overcome this problem. Such robots can approach from suitable directions and operate delicate tissues when performing retinal vein cannulation, epiretinal membrane peeling and so on. In this study, we propose an improved integrated robotic intraocular snake (I2RIS), which is a new version of our previous IRIS. This update focuses on the dexterous distal unit design and the drive unit design. The proposed dexterous distal unit consists of small elements with reduced contact stress. The proposed drive unit includes a new wire drive mechanism where the drive pulley is mounted at a right angle relative to the actuation direction (also, relative to the conventional direction). A geometric analysis and mechanical design show that the proposed drive mechanism is simpler and easier to assemble and yields higher accuracy than the conventional drive mechanism. Furthermore, considering clinical use, the instrument of the I2RIS is detachable from the motor unit for cleaning, sterilization, and attachment of various surgical tools. Weighing merely 31.3 g, the proposed mechanism is only one third of the weight of the conventional IRIS. The basic functions and effectiveness of the proposed mechanism are verified by experiments on 5:1 scaled-up models of the dexterous distal unit and actual-size models of the instrument and motor units.

A Comparison of Manual and Robot Assisted Retinal Vein Cannulation in Chicken Chorioallantoic Membrane.

Retinal vein occlusion (RVO) is a vision threatening condition occurring in the central or the branch retinal veins. Risk factors include but are not limited to hypercoagulability, thrombus or other cause of low blood flow. Current clinically proven treatment options limit complications of vein occlusion without treating the causative occlusion. In recent years, a more direct approach called Retinal Vein Cannulation (RVC) has been explored both in animal and human eye models. Though RVC has demonstrated potential efficacy, it remains a challenging and risky procedure that demands precise needle manipulation to achieve safely. During RVC, a thin cannula (diameter 70-110 µm) is delicately inserted into a retinal vein. Its intraluminal position is maintained for up to 2 minutes while infusion of a therapeutic drug occurs. Because the tool-tissue interaction forces at the needle tip are well below human tactile perception, a robotic assistant combined with a force sensing microneedle could alleviate the challenges of RVC. In this paper we present a comparative study of manual and robot assisted retinal vein cannulation in chicken chorioallantoic membrane (CAM) using a force sensing microneedle tool. The results indicate that the average puncture force and average force during the infusion period are larger in manual mode than in robot assisted mode. Moreover, retinal vein cannulation was more stable during infusion, in robot assisted mode.

Towards Bimanual Vein Cannulation: Preliminary Study of a Bimanual Robotic System With a Dual Force Constraint Controller.

Retinal vein cannulation is a promising approach for treating retinal vein occlusion that involves injecting medicine into the occluded vessel to dissolve the clot. The approach remains largely unexploited clinically due to surgeon limitations in detecting interaction forces between surgical tools and retinal tissue. In this paper, a dual force constraint controller for robot-assisted retinal surgery was presented to keep the tool-to-vessel forces and tool-to-sclera forces below prescribed thresholds. A cannulation tool and forceps with dual force-sensing capability were developed and used to measure force information fed into the robot controller, which was implemented on existing Steady Hand Eye Robot platforms. The robotic system facilitates retinal vein cannulation by allowing a user to grasp the target vessel with the forceps and then enter the vessel with the cannula. The system was evaluated on an eye phantom. The results showed that, while the eyeball was subjected to rotational disturbances, the proposed controller actuates the robotic manipulators to maintain the average tool-to-vessel force at 10.9 mN and 13.1 mN and the average tool-to-sclera force at 38.1 mN and 41.2 mN for the cannula and the forcpes, respectively. Such small tool-to-tissue forces are acceptable to avoid retinal tissue injury. Additionally, two clinicians participated in a preliminary user study of the bimanual cannulation demonstrating that the operation time and tool-to-tissue forces are significantly decreased when using the bimanual robotic system as compared to freehand performance.

Electrical Bio-Impedance Proximity Sensing for Vitreo-Retinal Micro-Surgery

Retinal vein occlusion is a widespread eye vascular disease leading to vision loss because of clots obstructing a retinal vessel. Recent research investigated retinal vein cannulation, a promising treatment in which a microneedle injects a thrombolytic agent inside the clotted vessel. During this surgical procedure, the surgeon only relies on a microscope, looking through the patient eye's lens. Such visual feedback gives poor depth perception, with a risk to inject the agent underneath the retina. Such situation endangers the patient's eyesight and is to be avoided. This letter explores bio-impedance as a means to estimate the proximity between an insulated electrode and a retinal vessel. Experiments on five ex-vivo pig eyes showed that the impedance phase decreases as the electrode tip approaches the retinal vessel. Specific patterns in the impedance magnitude were detected. A dedicated algorithm showed 98 $\%$ sensitivity and 100 $\%$ specificity at a distance of 775 ± 275 μm away from the retinal vessels. Knowledge of the proximity can help the surgeon prevent damaging fragile retinal structures during retinal surgeries such as cannulation and scar tissue peeling. A minimally-invasive measurement principle of this technique is demonstrated on an ex-vivo pig head to show the feasibility of such technique in more realistic conditions.

Dual-Stiffness Force-Sensing Cannulation Tool for Retinal Microsurgery.

Retinal vein cannulation is a promising treatment for retinal vein occlusion that involves the injection of an anticoagulant directly into the occluded vein to dissolve the blockage. However, excessive forces applied by the injection tool during the procedure, at either the scleral incision or injection site, can result in injury to the eye. Furthermore, the force required to puncture retinal veins (around 10 mN) is well below human sensing ability and an order of magnitude smaller than those that can be safely applied at the sclera (around 100 mN). Detection and management of tool-to-tissue forces on these different scales are some of the most challenging aspects of the cannulation procedure. This work describes the development of a sensorized cannulation tool capable of detecting both tool-to-vein puncture forces and tool-to-sclera contact forces. By combining two materials, nitinol alloy for the tool tip and stainless steel for the tool shaft, to achieve dual stiffness, the tool possesses a flexible tip to capture small vein puncture forces and a stiffer shaft to maintain straightness during use. Three segments of fiber Bragg grating sensors are calibrated to measure the transverse forces at both the tool tip and sclerotomy, as well as to determine the tool insertion depth within the eye. The results of the validation experiments show that the root mean square error of the measurements for the force at the tip, the force at the sclerotomy, and the tool position are 0.70 mN, 1.59 mN, and 0.69 mm, respectively.

Design and evaluation of a new bioelectrical impedance sensor for micro-surgery: application to retinal vein cannulation.

Nowadays, millions of people suffer from retinal vein occlusion, a blind-making eye disease. No curative treatment currently exists for this vascular disorder. However, a promising treatment consists in injecting a thrombolytic drug directly inside the affected retinal vessel. Successfully puncturing miniature vessels with diameters between 50 and 400[Formula: see text] remains a real challenge, amongst others due to human hand tremor, poor visualisation and depth perception. As a consequence, there is a significant risk of double-puncturing the targeted vessel. Sub-surfacic injection of thrombolytic agent could potentially lead to severe retinal damage. A new bio-impedance sensor has been developed to visually display the instant of vessel puncture. The physical working principle of the sensor has been analysed, and a representative electrical model has been derived. Based on this model, the main design parameters were derived to maximise the sensor sensitivity. A detailed characterisation and experimental validation of this concept were conducted. Stable, repeatable and robust impedance measurements were obtained. In an experimental campaign, 35 puncture attempts on ex vivo pig eyes vessels were conducted. A confusion matrix shows a detection accuracy of 80% if there is a puncture, a double puncture or no puncture. The 20% of inaccuracy most probably comes from the limitations of the employed eye model and the experimental conditions. The developed bio-impedance sensor has shown great promise to help in avoiding double punctures when cannulating retinal veins. Compared to other puncture detection methods, the proposed sensor is simple and therefore potentially more affordable. Future research will include validation in an in vivo situation involving vitreoretinal surgeons.

Combined OCT distance and FBG force sensing cannulation needle for retinal vein cannulation: in vivo animal validation.

Retinal vein cannulation is an experimental procedure during which a clot-dissolving drug is injected into an obstructed retinal vein. However, due to the fragility and minute size of retinal veins, such procedure is considered too risky to perform manually. With the aid of surgical robots, key limiting factors such as: unwanted eye rotations, hand tremor and instrument immobilization can be tackled. However, local instrument anatomy distance and force estimation remain unresolved issues. A reliable, real-time local interaction estimation between instrument tip and the retina could be a solution. This paper reports on the development of a combined force and distance sensing cannulation needle, and its experimental validation during in vivo animal trials. Two prototypes are reported, relying on force and distance measurements based on FBG and OCT A-scan fibres, respectively. Both instruments provide an 80[Formula: see text] needle tip and have outer shaft diameters of 0.6 and 2.3mm, respectively. Both prototypes were characterized and experimentally validated ex vivo. Then, paired with a previously developed surgical robot, in vivo experimental validation was performed. The first prototype successfully demonstrated the feasibility of using a combined force and distance sensing instrument in an in vivo setting. The results demonstrate the feasibility of deploying a combined sensing instrument in an in vivo setting. The performed study provides a foundation for further work on real-time local modelling of the surgical scene. This paper provides initial insights; however, additional processing remains necessary.