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Henri Lorach, Yossi Mandel, Georges A Goetz, phililp huie, Roopa Dalal, Keith Mathieson, Xin Lei, Theodore Kamins, James Harris, Daniel V Palanker; Interaction between normal and prosthetic vision in a model of local retinal degeneration. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):756.
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To create a non-genetic model of local retinal degeneration in rats and assess the interactions of normal and prosthetic vision in such model.
Local retinal degeneration in Long Evans rats was induced by chronic separation of the retina from the pigment epithelium (RPE) using sub-retinal implant of 1mm in width and 30mm in thickness. Plastic disks were used for histological analysis, and photovoltaic arrays of the same size have been utilized to assess the interactions between normal and prosthetic vision. Each pixel of 70µm or 140µm in these arrays is composed of two or three photodiodes in series, which convert the near infrared (NIR) light into electrical pulses to stimulate the nearby retinal neurons. Prosthetic and visually evoked cortical activity was measured via transcranial screw electrodes above the visual cortex. Interaction of prosthetic and normal vision was assessed using a multifocal protocol with simultaneous activation of the implant using NIR radiation (915nm) and normal retina with visible light (532nm).
Photoreceptors above the subretinal implant degenerated over time, with 80% of the outer nuclear layer disappearing within a month, and the rest by 3 months. Cells in the inner nuclear layer and ganglion cell layer were preserved during the 1 year follow-up, although there were signs of rewiring and decrease in the size of the bipolar cell terminals, labeled with PKC, in the implanted area.<br /> Both prosthetic and normal visual stimulation produced cortical responses, which interact in a quasi-linear fashion. Retinal adaptation to bright ambient had no significant effect on prosthetic responses as opposed to the effect on visible light responses.
A subretinal implant induces highly reproducible local degeneration of the photoreceptors above it, with preservation of the inner retinal neurons but signs of synaptic plasticity. This non-genetic model of local loss of photoreceptors might be convenient for basic studies of the retinal degeneration and for development of therapeutic strategies in a wide variety of species with vascular retina. It allows investigating the interactions between the artificial sight (prosthetic, optogenetic or optopharmacological) and normal vision, which are important for patients preserving significant areas of normal retina, such as in Age Related Macular Degeneration.
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