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BACKGROUND: Subretinal cell transplantation is a challenging surgical maneuver. This paper describes the preliminary findings of a new tissue injector for subretinal implantation of an ultrathin non-absorbable substrate seeded with human embryonic stem cell-derived retinal pigment epithelium (hESC-RPE). METHODS: Ultrathin Parylene-C substrates measuring 3.5 mm × 6.0 mm seeded with hESC-RPE (implant referred to as CPCB-RPE1) were implanted into the subretinal space of 12 Yucatan minipigs. Animals were euthanized immediately after the procedure and underwent spectral domain optical coherence tomography (SD-OCT) and histological analysis to assess the subretinal placement of the implant. Evaluation of the hESC-RPE cells seeded on the substrate was carried out before and after implantation using standard cell counting techniques. RESULTS: The tissue injector delivered the CPCB-RPE1 implant through a 1.5 mm sclerotomy and a 1.0-1.5 mm retinectomy. SD-OCT scans and histological examination revealed that substrates were precisely placed in the subretinal space, and that the hESC-RPE cell monolayer continued to cover the surface of the substrate after the surgical procedure. CONCLUSION: This innovative tissue injector was able to efficiently deliver the implant in the subretinal space of Yucatan minipigs, preventing significant hESC-RPE cell loss, minimizing tissue trauma, surgical complications and postoperative inflammation.
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BACKGROUND: Peeling procedures in retinal surgery require micron-scale manipulation and control of sub-tactile forces. METHODS: Hybrid position/force control of an actuated handheld microsurgical instrument is presented as a means for simultaneously improving positioning accuracy and reducing forces to prevent avoidable trauma to tissue. The system response was evaluated, and membrane-peeling trials were performed by four test subjects in both artificial and animal models. RESULTS: Maximum force was reduced by 56% in both models compared with position control. No statistically significant effect on procedure duration was observed. CONCLUSIONS: A hybrid position/force control system has been implemented that successfully attenuates forces and minimizes unwanted excursions during microsurgical procedures such as membrane peeling. Results also suggest that improvements in safety using this technique may be attained without increasing the duration of the procedure.
Assuntos
Micromanipulação/instrumentação , Microcirurgia/instrumentação , Retina/cirurgia , Procedimentos Cirúrgicos Robóticos/instrumentação , Animais , ZigotoRESUMO
Vitreoretinal microsurgery requires precise hand-eye coordination to manipulate delicate structures within the eye on the order of tens of microns. To achieve these tasks, surgeons use tools of diameter 0.9 mm or less to access the eye's interior structures. The level of force required during these manipulations is often below the human tactile threshold, requiring the surgeon to rely on subtle visual cues or to apply larger forces above the tactile threshold for feedback. However, both of these methods can lead to tissue damage. Excursions can be made into tissues which are not felt by the surgeon, while larger forces have a higher chance of damaging tissue within the eye. To prevent damage to the retina and other anatomy, we present the implementation of hybrid position/force control operating in the sub-tactile force range for a handheld robotic system. This approach resulted in a 42% reduction in the mean force and 52% reduction in maximum force during peeling tasks.
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This paper presents the characterization and comparison of physiological tremor for pointing tasks in multiple environments, as a baseline for performance evaluation of microsurgical robotics. Previous studies have examined the characteristics of physiological tremor under laboratory settings as well as different operating conditions. However, different test methods make the comparison of results across trials and conditions difficult. Two vitroretinal microsurgeons were evaluated while performing a pointing task with no entry-point constraint, constrained by an artificial eye model, and constrained by a rabbit eye in vivo. For the three respective conditions the 3D RMS positioning error was 144 µm, 258 µm, and 285 µm, and maximum 3D error was 349 µm, 647 µm, and 696 µm. A spectral analysis was also performed, confirming a distinct peak near in the 6-12 Hz frequency range, characteristic of hand tremor during tasks in all three environments.
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This paper presents the first experimental results from human users of a new 6-degree-of-freedom handheld micromanipulator. This is the latest prototype of a fully-handheld system, known as "Micron," which performs active compensation of hand tremor for microsurgery. The manipulator is a miniature Gough-Stewart platform incorporating linear ultrasonic motors that provide a cylindrical workspace 4 mm long and 4 mm wide. In addition, the platform allows the possibility of imposing a remote center of motion for controlling motion not only at the tip but also at the entry point in the sclera of the eye. We demonstrate hand tremor reduction in both static and dynamic micromanipulation tasks on a rubber pad. The handheld performance is also evaluated in an artificial eye model while imposing a remote center of motion. In all cases, hand tremor is significantly reduced.
Assuntos
Microcirurgia/instrumentação , Amplitude de Movimento Articular , Olho Artificial , Humanos , Modelos Teóricos , Procedimentos Cirúrgicos Oftalmológicos/instrumentação , TremorRESUMO
An active handheld micromanipulator has been developed to cancel hand tremor during microsurgery. The micromanipulator is also applicable in optical coherence tomography to improve the quality of scanning and minimize surgical risks during the scans. The manipulator can maneuver the tool tip with six degrees of freedom within a cylindrical workspace 4 mm in diameter and 4 mm high. The imaging system is equipped with a 25-gauge Fourier-domain common-path OCT probe. This paper introduces the handheld OCT imaging system and techniques involved and presents stabilized OCT images of A-mode and M-mode scans in air and live rabbit eyes. We show the first demonstration of OCT imaging using the active handheld micromanipulator in vivo.