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S-C Pan, TM O'Hearn, JD Weiland, MS Humayun, SR Sadda; Electrical Stimulation of Normal and Retinal Degenerate (rd) Isolated Mouse Retina with 25 um Electrodes . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4461.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous studies using retinal ganglion cell recordings have found lower thresholds and latencies when isolated mouse retinas are stimulated on the ganglion cell side versus the photoreceptor side in normal retina, and higher thresholds and latencies for rd versus normal retina when the stimulus is delivered on the ganglion cell side. In an effort to reduce thresholds and further maximize stimulus parameters for a retinal prosthesis the effect of reducing the size of the stimulating electrode was studied in both normal and retinal degenerate (rd) isolated mouse retina. Methods:Fourteen retinas each were isolated from either normal or rd mice for stimulation. Electrical stimulation was delivered via two 25 mm macroelectrodes positioned at either the photoreceptor (PR) or ganglion cell (GGL) surface. A cathodic first, charge balanced, biphasic, square wave stimulus with a phase duration of 1ms and a 3ms interphase delay was used for all stimulation cycles. Recording of induced responses was performed using penetrating tungsten wire microelectrodes positioned in the ganglion cell layer. Results:No significant difference was observed in either threshold or latency between ganglion cell side stimulation in normal retina with 25 um electrodes, and similar stimulation with 125 um electrodes. Threshold and latency data were obtained for the other combinations of retina type, and side of stimulus delivery for comparison. Conclusion:Stimulation of the ganglion cell side of normal retina with an electrode of smaller diameter (25um vs. 125um) did not yield a reduction in stimulus thresholds, or a change in response latencies. Further manipulation of stimulus parameters is necessary in order to reduce stimulus thresholds, and create a more favorable prosthesis.
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