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Eberhart Zrenner, Karl-Ulrich Bartz-Schmidt, Caroline Chee, Florian Gekeler, Timothy L Jackson, Robert MacLaren, Janos Nemeth, Helmut Sachs, Katarina Stingl, David Wong, SUBRET Study Group; Visual outcome in 26 blind retinitis pigmentosa patients after implantation of subretinal Alpha-IMS devices. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5967.
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To assess the 12-month visual and safety outcomes following implantation of a 1500-pixel subretinal implant in patients blind from retinitis pigmentosa (RP).
Alpha-IMS subretinal implants (Retina Implant AG, Reutlingen, Germany) were positioned beneath the foveal region of 14 male and 12 female RP-patients (mean age 53.2 ± 8.2). Each of the 1500 subfoveal photodiodes within a 11° by 11° field controls an amplifier that, depending on the strength of the light, emits currents to stimulate overlying bipolar cells. Power and control signals are supplied inductively via a subdermal, retroauricular coil from which a subdermal cable leads to the eyeball. Function was tested by 4 procedures - 1: Monitor-based standardized tests for light perception, light localization, movement detection, grating acuity and visual acuity with Landolt C-rings (2- or 4 alternative-force-choice-tests); 2: Detection, localization and identification of objects placed on a table; 3: Reading letters; 4: Visual experiences during outdoor and daily-life activities.
1: Implant-mediated light perception was possible for 22 (85%) patients; light localization for 15 (58%); movement detection (up to 35 cycles/degree) for 6 (23%); measurable grating acuity (up to 3.3 cycles/degree) for 14 (54%); and measurable visual acuity (up to 20/546) for 4 (18%). 2: On a visual ability scale from 0 (worst) to 4 (best) for 4 white geometric figures presented on a black table, patients averaged 3.12 ± 0.31 for detection, 2.94 ± 0.3 for localization and 1.06 ± 0.28 for identification at month 2 which was significantly better (p< 0.012) than with chip power switched off. Similar results were obtained with activities of daily living. Losses of approximately 1-1.5 units occured over 9-12 months. 3: Four patients (18%) could read letters 4-8 cm in size. 4: Twelve patients (46%) reported useful visual experiences including recognition of details and 7 patients (27%) could localize objects in daily life without details. 5: Besides two treatable serious adverse events there were no safety concerns.
The Alpha-MS implant has a CE mark for commercial use in Europe. Psychophysical testing and self-reported outcomes show restoration of useful vision in a majority of patients. Subretinal implantation surgery is safe and a multicenter study is continuing with a slightly modified implant to establish long term durability.
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