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Thomas Edwards, Charles L Cottriall, James D Ramsden, Matthew Simunovic, Kanmin Xue, Eberhart Zrenner, Robert E MacLaren; Sub-retinal implantation of the Retinal Implant Alpha AMS chip using integrated intra-operative optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4268.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the safety and efficacy of a subretinal electronic implant in end-stage retinitis pigmentosa
The Retina Implant Alpha AMS (Retina Implant AG, Reutlingen, Germany) was implanted into six participants in an ongoing prospective clinical trial sponsored by the University of Oxford. Inclusion criteria included vague non-localizing or no light perception in the implanted eye and prior normal distance and reading vision. Functional outcome measures included monitor and table-based tests. Surgical implantation guided by an optical coherence tomography (OCT) enabled operating microscope (Carl Zeiss Cambridge, UK) was also assessed.
All six participants underwent subretinal implantation with follow up periods ranging from 1-12 months. Use of an OCT microscope facilitated sub-macular chip implantation in P6 with enhanced accuracy. The OCT guidance identified the subretinal plane and guarded against chip advancement into the choroid or retina. Light perception, temporal resolution and light localization was improved by the implant in all but one participant (P4) in whom the chip was not functioning optimally. The best grating acuity recorded for P1, P2, P3, P5 and P6 was 3.3, 1.0, 0.1, 0.33 and 0.1 cycles/degree respectively. The best-recorded number of high contrast (white on black) objects correctly located on a table was 3.2 and 0.5 with implant on vs off respectively (mean value; max. 4). Similarly, for high contrast tableware the number of items located was 3.2 and 0.7 for implant on vs off respectively (mean value; max. 4). Overall, grey-scale discrimination was greater with the implant on vs off for five participants. All but P4 reported a subjective improvement in activities of daily living. The implant was removed from P3 after three months due to damage to the laminate insulation during a surgical revision, with a resulting loss of function. A retinal detachment occurred in the implant eye of P2 at 9 months, but reattachment surgery was performed without disturbing chip position.
The Retina Implant Alpha AMS improved visual performance in 5 out of 6 participants and has exhibited sustained functional longevity. Although implantation surgery remains challenging, new developments such as OCT microscope guidance add further refinements to the surgical technique.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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