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Eberhart Zrenner, A. Bruckmann, U. Greppmaier, G. Hoertdoerfer, C. Kernstock, I. Sliesoraityte, K. Stingl, B. Wilhelm; Improvement of Visual Orientation and Daily Skills Mediated by Subretinal Electronic Implant Alpha IMS in Previously Blind RP Patients. Invest. Ophthalmol. Vis. Sci. 2011;52(14):457.
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To investigate visual perception of previously blind retinitis pigmentosa (RP) patients using electronic subretinal implants with 1500 pixels and to compare performance with psychophysical lab tests.
The new Alpha IMS chip (Retina Implant AG) with its 1500 photodiodes, amplifiers and electrodes powered wirelessly via a subdermal coil was implanted subretinally in 5 retinitis pigmentosa patients. Patients adjusted gain and sensitivity themselves when using the implant indoors or outdoors on their own.
Spatial resolution can be achieved up to VA 21/1000 within a field of 11° by 11°, as already assessed by Landolt rings or grating tests in the previous pilot study (http://rspb.royalsocietypublishing.org/content/early/2010/11/01/rspb.2010.1747).A) Near vision: Localizing plates, cutlery and tableware in 4AFC mode, recognizing plates and their content, fruit in restaurants, bed in the hotel, facial characteristics of persons (teeth,nose, eyes, glasses), spontaneous reading of number of dots on dices, items on working desk.B) Far vision: Recognizing clouds, discerning smaller from larger persons or recognizing characteristics of clothes people are wearing; identifying the borders of cars by metallic reflections or walking along a white line.C) Spatial resolution: Resolving the position of clock hands, grid patterns up to approx. 0.33 - 0.44 cpd, reading letters 4 to 8 cm high, localizing and recognizing of square, diamond-shaped, round or rectangular objects presented at visual angles of 6° to 8°.D) Color vision: Although color vision is not possible, the subjects differentiated 7 to 10 shades of grey; they show increased sensitivity for infrared radiation, resulting in a shifted brightness perception.E) Motion: Seeing hand moving, recognizing walking direction of a white goose, circumvention of obstacles.F) Eye-hand coordination: Pointing at objects and moving them.
Subretinal implants using Alpha IMS technology allow continuous vision without headshaking. Patients with Alpha IMS implant can utilize shadows as well as parallax for object localization and visuomotor tasks in order to improve their orientation and mobility. Vision mediated by Alpha IMS device thereby can provide considerable support to blind RP patients in mastering tasks of daily life, indoors and outdoors.
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