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Jeeun Kang, Zeng Fan, Adarsha Malla, Maged Harraz, James Spicer, Peter L Gehlbach, Emad Boctor; An Epiretinal Photoacoustic Stimulation Approach for Retinal Stimulation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4973.
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© ARVO (1962-2015); The Authors (2016-present)
There are several attempts to provide apply electrical or ultrasound approaches to the . Here we update our progress in a novel epiretinal photoacoustic stimulation (ePAS) approach for novel bionic eye solution.
The laser excitation in our ePAS system was performed by a 1064-nm fiber-coupled laser with 1mJ energy per pulse (VPFL-ISP-VPOD-30, Spectra-Physics, United States). The membrane potential change was monitored for 5 min for the neurons dyed with membrane potential sensitive fluorescent dye, i.e., DiBAC4(3). The ePAS was performed for 20 seconds at 60-second point with different pulse durations (100, 150, and 200 nsec) to change PA pressure. Otherwise, the sham group was designed to have same protocol excepting the ePAS procedure. The membrane potential change was normalized with a read of each case at 10 seconds. In this presentation, we further investigate the optimal ePAS layers: India rubber and Palladium-silicone nanocomposite (Pd-Si) layers. The acoustic power density and temperature for each non-photonic stimulation were quantified by the calibrated hydrophone (HGL-1000, ONDA, US) and real-time infrared thermographic camera (Flir ONE, FLIR Systems, Inc., US).
In vitro results confirm thatthe fractional change in membrane potential in the ePAS group was significantly different from that of a sham group. The maximum fractional changes in membrane potential with 100, 150, and 200 nsec pulse widths were 1.45 ± 0.09, 1.36 ± 0.04, and 1.15 ± 0.03, respectively; while those in the sham group stayed at baseline levels, i.e., 1.02 ± 0.01. Acoustic measurements indicate that the proposed Pd-Si layer is able to produce significantly-higher acoustic power than an India rubber layer using the same amount of laser energy: 3.5W/cm2vs. 1.8W/cm2at 100ns pulse width. Morover, the normalized thermal change confirms more rapid thermal release in a Pd-Si layer than in an India rubber layer This suggests a faster framerate in any resulting bionic eye device: The half temperature level in Pd-Si and India rubber layers were obtained at 7.5 sec and 13.5 sec after the identical laser excitations, respectively. For 25% and 12.5% levels, a Pd-Si layer also provided approximately double the thermal dissipation rate as India rubber: 17.5 vs. 30.5 sec at 25% level; 26.5 vs. 56.5 sec at 12.5% level.
We present preliminary results and suggest advantages of a Pd-Si layer approach to artificial vision.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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