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T. Fujikado, Y. Okawa, T. Miyoshi, Y. Hirohara, T. Mihashi, Y. Tano; Contribution of Retinal Ganglion Cells to Intrinsic Signals in Retinal Optical Imaging by Trans-Corneal Electrical Stimulation or by Light Stimulation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2003. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Three eyes of three cats were studied under general anesthesia. For TcES, the electrical current was applied from the fixed frame with rectangular, train of 20 paired biphasic pulses. For LS, 4 cycles/degree black and white squares alternating at 8 Hz were projected as a vertical bar for 4 sec. Fundus images in the near-infrared (800-880nm) were obtained in every 25msec between 2 seconds before and 20 seconds after stimulation. Two-dimensional topography of reflectance change (RC) was constructed by subtracting images before stimulation from those after stimulation. Experiments were carried out before and after TTX (5mM, 20ul) injection intravitreally.
RC was observed at OD by TcES (-0.45% at 1.0mA) and both at OD (-0.25%), and light-stimulated retina (LSR, -0.75%) by LS. After TTX application, the RC at OD disappeared almost completely by TcES and LS but those at LSR by LS reduced only 15-20%.
The blockage of RGC activity by TTX extinguished the RC at optic disc, suggesting that the intrinsic signal at optic disc may represent the activity of RGCs and could be used to evaluate the RGCs functionally.
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