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Artificial Vision with Wirelessly Powered
Subretinal Electronic Implant Alpha IMS

The publication “Artificial Vision with Wirelessly Powered Subretinal Electronic Implant Alpha IMS” by Stingl K. et al. Proceedings of Royal Society B (2013), published online Feb 20, 2013, describes the functional results in 9 patients, blind from retinitis pigmentosa, who have received a subretinal electronic implant Alpha IMS (Retina Implant AG) in the first monocentre phase of a clinical trial at the Center of Ophthalmology in Tübingen, Germany. The design of the device and the clinical trial is based on a previous pilot study (E. Zrenner et al. Proc. Biol. Sci. 2011, 278: 1489-97). The recent publication describes several novel findings, seen in individual patients:

  • wireless subretinal implant Alpha-IMS with 1,500 pixels providing a visual field of 11 to 15 deg extension
  • shown to help blind RP patients, in their daily life, when freely moving, recognizing door handles, signs, trees etc.
  • useful visual experiences including recognition of facial expressions, letter reading, object recognition and localisation, e.g. cutlery and drinking glasses, vision at night, such as lanterns, shopping windows, car lights.
  • the perceived image is described as a slightly flickering black-and-white image, in shades of grey similar to luminance distribution in natural vision
  • visual acuity could be measured with standardized Landolt C-rings and achieved 0.01 and 0.037 (reproducible) in two subjects
  • grating acuity was successfully measured in most of the subjects and reached up to 3.3 cycles per degree
  • motion perception via the implant reached up to 35 degrees per second (corresponds to a velocity of 22km/h in 10 meters distance)
  • standardized tests of activities of daily living significantly improved with the chip for objects identification, localization and recognition.
  • cosmetically the implant is unproblematic, as all parts are located inside the body, including a power cable underneath the skin that leads to an implanted coil behind the ear. Power is transmitted from a small battery pack, which is carried in the pocket, and an inductive transmitter coil is magnetically attached behind the ear, above the skin.
  • it is the only retina implant worldwide, so far, where the image receiver is positioned inside the eye, moving with the eye, therefore allowing continuous refreshment of images by natural eye movement and gaze, aiding object localization and identification.

The ongoing study became multicentre in 2012 with 16 more patients successfully receiving an implant in Oxford, London, Tübingen, Hong Kong and other centres, with similar results. Not every patient benefits equally as the state of disease is quite variable but all but one patient reported perception of light and most can localize objects. Observation time is up to 15 months so far. Preparations have been made to extend the study to the United States.

Publication

Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS. Stingl K, Bartz-Schmidt KU, Besch D, Braun A, Bruckmann A, Gekeler F, Greppmaier U, Hipp S, Hörtdörfer G, Kernstock C, Koitschev A, Kusnyerik A, Sachs H, Schatz A, Stingl KT, Peters T, Wilhelm B, Zrenner E. Proc Biol Sci. 2013 Feb 20;280(1757):20130077. Print 2013.

http://rspb.royalsocietypublishing.org/content/280/1757/20130077

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