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Thijs H C M Meenink, Marc D de Smet, Gerrit Naus, Maarten Beelen, Maarten Steinbuch; Micrometer-precision penetration motion in robot-assisted vitreoretinal surgery. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2323.
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Precision is a major requirement in vitreoretinal surgery. Instrument positioning inside the eye involves 4 degrees of freedom; axial instrument rotation, instrument penetration motion and two rotations around the entry point of the eye. Both for safety and for procedure efficacy, the most important motion in vitreoretinal surgery is the instrument penetration motion. For different tasks, different motion profiles are desirable, ranging from slowly approaching the retina, e.g., for membrane peeling, to fast puncturing motions over a short distance, e.g., for subretinal or intravenous injections. The human hand precision of experienced vitreoretinal surgeons typically is in the order of 100µm [Riviere, 1997]. Both to enable treatment of manually untreatable indications and to improve existing surgical tasks, a higher precision would be beneficial. The purpose of this study is to evaluate positional precision of a vitreoretinal instrument using the PRECEYES Surgical System [Meenink, 2012] versus freehand motion.
A phantom eye model with a simulated retinal surface was used to determine the positioning and the penetration precision. The surgeon was asked to touch the surface of a paper grid at several locations and to penetrate repeatedly to the same depth at pre-specified locations. Freehand and robot-assisted performance were compared. Robotic assistance was adjusted to filter tremor and automatically execute small, predefined motion profiles. After positioning the instrument above the target area, an incremental penetration motion was automated upon user request using a foot pedal.
Manual penetration precision of 203µm was achieved compared to an automated penetration precision of 19µm. Automated penetration results in a 10 times more reproducible result compared to manual penetration. The precision improvement in X and Y direction is less substantial: a manual X and Y precision of 64μm was achieved compared to an automated X and Y precision of 24μm.
For vitreoretinal instrument manipulation, the penetration precision is an important component required for surgical success. However, this motion is typically difficult to manually execute with high precision. A 10 times higher precision can be achieved by semi-automatic execution of a penetrating motion using robot assistance. This can significantly benefit specific vitreoretinal tasks such as subretinal and intravenous injections.
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