Insertion force in manual and robotic corneal suturing

A Mechanical Evaluation of a Robot-Assisted Cutting Cornea Based on Force Response

The aim of this paper is to propose laws of trephine operation based on a robot-assisted cutting cornea in order to obtain better microsurgical effects for keratoplasty. Using a trephine robot integrated with a microforce sensor and a handheld trephine manipulator, robotic and manual experiments were performed, with porcine corneas as the test subjects. The effect of trephine operational parameters on the results reflected by the biomechanical response is discussed, and the parameters include linear velocity, rotating angle, and angular velocity. Using probability density functions, the distributions of the manual operational parameters show some randomness, and there is a large fluctuation in the trephine force during the experiments. The biomechanical response shows regular trends in the robotic experiments even under different parameters, and compared to manual trephination, the robot may perform the operation of trephine cornea cutting more stably. Under different operational parameters, the cutting force shows different trends, and the optimal initial parameters that result in better trephine effects can be obtained based on the trends. Based on this derived law, the operational parameters can be set in robotic trephination, and surgeons can also be specially trained to achieve a better microsurgical result.

Sensor-Embedded Automatic Grasping Forceps for Precise Corneal Suture in Penetrating Keratoplasty

In penetrating keratoplasty (PKP), the proper corneal suture placement is very important for successful transplantation and restoring functional vision. Generating sutures with accurate depth is difficult for the surgeon because of the tissue’s softness, lack of depth information, and hand tremors. In this paper, an automatic cornea grasping device is proposed, which detects when the device reaches the target suture depth. When the device reaches the target depth, the device rapidly grasps the cornea to prevent error induced by human hand tremors. In the paper, the performance of the proposed sensor, the actuator, and the device are experimentally verified with ex vivo experiment. The result showed that the proposed device could enhance the accuracy and precision of the corneal suture depth.

Analysis and Evaluation of a Robotic Trephination in Penetrating Keratoplasty

It is difficult to achieve a stably delicate operation in manual microsurgery, and the aim of this paper is to evaluate the robotic trephination that can open a promising perspective for the development of robotic microsurgical system for keratoplasty. A robot for corneal trephination integrating a force/torque sensor is designed based on manual trephine action. The manual experiments and the robotic experiments about penetrating trephination are performed in porcine eyes. The expected values of operational parameters that are references to the robotic trephination are obtained from the manual experiments using probability density functions (PDFs), including linear velocity, angular velocity, and rotating angle. Considering the meanings of the forces/torques, the results of the manual and robotic experiments such as trephine forces/torques and photomicrographs are compared to evaluate the effectiveness of robotic trephination. The manual trephination shows some randomness and this leads to large fluctuations in the trephine forces/torques during the surgery, but the robot may improve overall outcome of the graft, as it is able to carry out the operation stably and produce a uniform cutting margin. There is potential to improve the biomechanical properties in the delicate microsurgery by using the trephine robot and such devices can assist the surgeon to achieve a consistently high-quality result.

Study of insertion force and deformation for suturing with precurved NiTi guidewire

This research presents an experimental study evaluating stomach suturing using a precurved nickel-titanium (NiTi) guidewire for an endoscopic minimally invasive obesity treatment. Precise path planning is critical for accurate and effective suturing. A position measurement system utilizing a hand-held magnetic sensor was used to measure the shape of a precurved guidewire and to determine the radius of curvature before and after suturing. Ex vivo stomach suturing experiments using four different guidewire tip designs varying the radius of curvature and bevel angles were conducted. The changes in radius of curvature and suturing force during suturing were measured. A model was developed to predict the guidewire radius of curvature based on the measured suturing force. Results show that a small bevel angle and a large radius of curvature reduce the suturing force and the combination of small bevel angle and small radius of curvature can maintain the shape of guidewire for accurate suturing.