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Christoph J. Kernstock, Soeren Danz, Katarina Stingl, Dorothea Besch, Assen Koitschev, Karl U. Bartz-Schmidt, Eberhart Zrenner; 3D-Visualisation Of Power Supply Cable Of Subretinal Electronic Implants During Eye Movement. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1341.
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Due to eye movements, power supply cables of retinal implants are exposed to mechanical stress over time. Cable positions during eye movement are assessed to estimate the stress that acts on the cable in order to provide data essential for designing durability tests of the cable.
A subretinal chip (Alpha IMS, Retina Implant AG Reutlingen Germany) was implanted with a powersupply cable running from an equatorial connection point at the sclera to the orbital rim and further to a retroauricular subdermal coil. CT scans were performed with a Siemens Sensation 16 Computer Tomograph in 4 viewing directions (upper-temporal/upper-nasal/lower-temporal/lower-nasal) with 0.75mm interval. Volumetric and multiplanar reconstructions (MPR) were created, the viewing plane was aligned to the cable path for measurement of the bending angles.
Comparison of the 4 viewing directions in frontal, cranial and nasal virtual camera positions and in MPRs showed intraorbital bending angles of 60/133/110/162 degrees and 62/95/77/126 degrees around the orbital rim in upper-temporal/upper-nasal/lower-temporal/lower-nasal viewing direction respectively.
The maximum bending angles were found in upper-temporal, opposed to a maximal elongated cable position in the lower-nasal viewing direction. Volumetric computer tomography examinations in different viewing positions allow in-vivo estimation of forces acting on intraorbital cables of electronic retinal implants and provide valuable information for designing long-term durability test.
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