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A.Y. Chow, J.S. Pollack, K.H. Packo, R.A. Schuchard; The Artificial Silicon Retina Microchip for the Treatment of Retinitis Pigmentosa: 2 to 4 1/2 Year Update . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1140.
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Purpose: The long–term durability of an implanted subretinal Artificial Silicon Retina (ASR) microchip, its tolerance and its effectiveness in restoring visual function in 10 retinitis pigmentosa (RP) patients is reported. Methods: A photodiode–based 2 mm diameter ASR microchip which electrically stimulated contacting retina was implanted into the subretinal space 20 degrees from the macula in each of 10 RP patients and followed for 2 to 4 ½ years. Visual function changes were evaluated by ETDRS letters, grating acuity and automated visual fields. The ASR devices were also stimulated with infrared light to assess implant electrical activity as recorded by ERGs. Results: All patients tolerated the ASR microchip safely. One patient, who underwent subsequent phacoemulsification removal of a cataract in the implanted eye, developed a ½ mm superior migration of the implant and subretinal hemorrhage which resolved spontaneously and was thought to be caused by vibration of the implant from ultrasound energy. Implant electrical function was still demonstrated at 4 ½ years after implantation although with decreased electrical spike amplitude. Objective and subjective improvements in multiple areas of visual function have persisted for 4 1/2 years in the longest implanted subjects, although 1 of 3 in this group noted some diminution from the best improvement. Some patients in the latest group, implanted for 2 years, demonstrated still improving visual function compared to earlier patients who generally plateaued at 12 to 18 months. The greatest improvement has been in optotype and grating acuity, and in contrast perception. Conclusions: The subretinal ASR microchip is well tolerated in RP patients. High–powered ultrasound procedures in implanted eyes should be avoided. Persistent improvements of visual function in the retina both adjacent to and distant from the ASR implant continue to suggest a neurotrophic benefit of the ASR chip which in some RP patients may still be improving at 2 years postop.
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