Article CT Assessment of Intraorbital Cable Movement of Electronic Subretinal Prosthesis in Three Diferent Surgical Approaches Hanna Faber 1 , Ulrike Ernemann 2 , Helmut Sachs 3 , Florian Gekeler 4 , Søren Danz 7 , Assen Koitschev 8 , Dorothea Besch 1 , Karl-Ulrich Bartz-Schmidt 1 , Eberhart Zrenner 1,5,6 , Katarina Stingl 1,9,* , and Christoph Kernstock 1,* 1 University Eye Hospital, Center for Ophthalmology, University of Tuebingen, Tuebingen, Germany 2 Department of Diagnostic and Interventional Neuroradiology, Radiological Clinic, University of Tuebingen, Tuebingen, Germany 3 Ophthalmology Clinic, Städtisches Klinikum Dresden Friedrichstadt, Dresden, Germany 4 Ophthalmology Clinic, Klinikum Stuttgart, Stuttgart, Germany 5 Institute for Ophthalmic Research, Center for Ophthalmology, University of Tuebingen, Tuebingen, Germany 6 Werner Reichardt Centre for Integrative Neuroscience, University of Tuebingen, Tuebingen, Germany 7 Radiologische Praxis Hofbauer Danz Fischer, Sindelfngen, Germany 8 Clinic for Ear, Nose and Throat Disorders, Plastic Surgery, Klinikum Stuttgart, Stuttgart, Germany 9 Center of Rare Eye Diseases, University of Tuebingen, Tuebingen, Germany Correspondence: Eberhart Zrenner, Institute for Ophthalmic Research, Center for Ophthalmology, University of Tuebingen, Elfriede-Aulhorn-Str. 7, D-72076, Tuebingen, Germany. e-mail: ezrenner@uni-tuebingen.de Received: June 29, 2020 Accepted: February 3, 2021 Published: July 15, 2021 Keywords: electronic retinal implant; retina chip; computer tomography; cable movement; retinitis pigmentosa Citation: Faber H, Ernemann U, Sachs H, Gekeler F, Danz S, Koitschev A, Besch D, Bartz-Schmidt K-U, Zrenner E, Stingl K, Kernstock C. CT assessment of intraorbital cable movement of electronic subretinal prosthesis in three diferent surgical approaches. Transl Vis Sci Technol. 2021;10(8):16, https://doi.org/10.1167/tvst.10.8.16 Purpose: Electronic retinal implants restore some visual perception in patients blind from retinitis pigmentosa. Eye movements cause mechanical stress in intraorbital power supply cables leading to cable breaks. By using computer tomography (CT) scans at the extreme positions of the four cardinal gaze directions, this study determined in vivo, which of three surgical routing techniques results in minimal bending radius variation and favors durability. Methods: Nine patients received the frst-generation subretinal implant Alpha IMS (Retina Implant AG, Reutlingen, Germany) in one eye. Three techniques for intraor- bital cable routing were used (straight cable route (A), parabulbar loop (B), and encir- cling band (C)), each in three patients. All patients underwent computer tomography of the orbital region. The bending radius of the intraorbital cable was measured with the DICOM viewer Osirix v4.1.2 (Pixmeo SARL, Bernex, Switzerland) and served as indicator for mechanical stress. Results: Average bending radius variation was 87% for method A, 11% for method B, and 16% for method C. Methods A and B (P = 0.005) and methods A and C (P = 0.007) difered signifcantly, while method B and C showed no statistical diference (P = 0.07). Conclusions: Compared to straight routes, arcuated cable routes signifcantly reduce cable movement and bending. Due to an easier surgical procedure, a parabulbar loop is the preferred method to minimize bending radius variation and prolong survival time of electronic subretinal implants. Translational Relevance: CT analysis of cable bending of implanted medical devices allows to determine which surgical routing technique favors durability in vivo. Introduction One in 4000 of the world population sufers from retinitis pigmentosa (RP), a major cause of visual disability and blindness in middle-aged people. 1 Initially, the neuronal degeneration is limited to the frst neuron of the visual system (the photorecep- tor), whereas many of the second neurons (bipolar cells) and third neurons (ganglion cells) still operate for a long time during the course of disease. 2 One way to partially restore visual function is the use of a Copyright 2021 The Authors tvst.arvojournals.org | ISSN: 2164-2591 1 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Downloaded from tvst.arvojournals.org on 07/21/2021