Article
The active subretinal implant: 10 years of development to clinical application
Das aktive subretinale Implantat: 10 Jahre Entwicklung bis zur klinischen Anwendung
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Authors
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E. Zrenner
- University Eye Hospital, Tuebingen, Germany
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D. Besch
- University Eye Hospital, Tuebingen, Germany
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K. U. Bartz-Schmidt
- University Eye Hospital, Tuebingen, Germany
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F. Gekeler
- University Eye Hospital, Tuebingen, Germany
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V.-P. Gabel
- University Eye Clinic, Regensburg, Germany
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C. Kuttenkeuler
- University Eye Hospital, Tuebingen, Germany
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H. Sachs
- University Eye Clinic, Regensburg, Germany
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H. Sailer
- Retina Implant GmbH, Reutlingen, Germany
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B. Wilhelm
- STC Autonomous Nervous System and Safety Studies, Ofterdingen, Germany
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R. Wilke
- University Eye Hospital, Tuebingen, Germany
| Published: | September 18, 2006 |
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Outline
Text
Objective
1) Presentation of essentials of a 10-year development: technology, biostability, biocompatibility, and surgical techniques of subretinal multielectrode arrays.
2) Assessment of function of subretinal implants consisting of a chip (3x3x0.1mm, 1500 microphotodiodes, amplifiers and electrodes of 50x50 micrometers, spaced 70 micrometers) and a 4x4 array of identical electrodes, spaced 280 micrometers, for direct stimulation (DS), chronically implanted next to the foveal rim of 2 blind RP patients.
Methods
Chip and DS array are positioned on a small subretinal polimide foil powered via a subretinal transchoroidal, retroauricular transdermal line ending in a radio-controlled, battery-driven receiver box (surgical details Sachs et al., ARVO 2006). According to the study plan, the implant was removed in one patient after 4 weeks. The other patient decided to keep the implant. The charge injection delivered by 16 DS electrodes was simultaneous or successive in order to present temporal or spatial patterns.
Results
Here, the results of chronic implantation and subretinal stimulation are reported in patients. The implants were well-tolerated without adverse events. OCTs showed stable attachment of the retina (see Kuttenkeuler et al., ARVO 2006). Patients reported small, yellowish or greyish phosphenes for individual electrode stimulation. They were able to differentiate spatial patterns such as lines, angles or bright squares. Simultaneous stimulation of four electrodes in a line or a row was reported as "bright yellowish rod with round corners, the size of a match, with four slight indentations on both sides." The patient was able to clearly distinguish horizontal from vertical lines and to correctly describe the alignment and direction of dot movement if three or four neighboring electrodes were switched on sequentially at one-second intervals. Electrical thresholds assessed by chronaxy measurements of each individual electrode and perceptual correlates remained relatively stable (see Wilke et al., ARVO 2006).
Conclusions
Chronic subretinal stimulation via small electrodes with a distance of approximately 1° allows the discrimination of patterns consisting of small, bright, steadily appearing dots that can be individually discriminated as well as combined into lines and figures, reliably repeated over weeks via a well-tolerated, still intact subretinal micro-electrode array in blind RP-patients.
Supported by BMBF 01KP0008 and Retina Implant GmbH
