Purchase this article with an account.
Richard Smith, Georges Goetz, Keith Mathieson, James Loudin, Daniel Palanker, Alexander Sher; On Resolution of Photovoltaic Subretinal Prosthetics. Invest. Ophthalmol. Vis. Sci. 2013;54(15):347.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To characterize the spatial extent of retinal stimulation by a subretinal photovoltaic prosthetic device. This device aims to fulfill the role of missing photoreceptors by electrically stimulating inner retinal neurons surviving during retinal degeneration. High spatial resolution is essential for creating a useful visual perception in the blind patient. Here, we examine the spread of retinal response to local stimulation by a photovoltaic subretinal implant activated by pulsed near-IR (880nm) light illumination.
The response of retinal ganglion cells (RGCs) to such stimulation was examined in-vitro with a multielectrode array, using rat retinas with degenerate photoreceptors, from the Royal College of Surgeons strain. The retina was placed ganglion cell side down on a multielectrode array, and 140 micron-sized photodiode pixels were placed on top of it. Individual pixels were illuminated with spots of NIR light and the network-mediated responses of RGCs at various distances around the illuminated pixels were recorded. The spread of the retinal response was measured as a function of the intensity and duration of the IR pulses. The results were compared with the response of RGCs to visible light stimulation with spots of the same size in a wild type (WT) rat retina.
The number of network-mediated spikes elicited in RGCs in response to NIR pulses decreased with increasing distance from the illuminated pixel, and the spread of activation increased with increasing irradiance. On average, the number of elicited spikes decreased to 50% of its maximum at distances of 170-400 microns, for irradiances of 10-20 mW/mm2 with 8ms pulse duration. This range is comparable with the 200 micron spread of response to visible light stimulation in the WT retina. We also characterized the retinal responses to two pixels stimulated simultaneously and compared that to the normal retinal response to two spots of light with different distances between them.
The spread of the retinal response to local photovoltaic stimulation in degenerate retina is comparable to the one elicited by visible light stimulus in the healthy retina. This result suggests that the surviving retinal circuitry retains sufficient localization of the processing of visual information, raising hope of restoration of reasonably high visual acuity using subretinal photovoltaic arrays.
This PDF is available to Subscribers Only