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Takeshi Morimoto, Hiroyuki Kanda, Tomomitsu Miyoshi, Yoko Hirohara, Toshifumi Mihashi, Yoshiyuki Kitaguchi, Kohji Nishida, Takashi Fujikado; Evaluation Of Retinal Reflectance Changes Elicited By Transcorneal Electrical Stimulation In Cat Eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3073.
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Transcorneal electrical stimulation (TES) is clinically applied for the treatment of optic neuropathies (Fujikado, 2006) and retinitis pigmentosa, (Schatz, 2011). However the excited retinal area by TES has not been well determined because 2-dimensional measurement of retinal function was difficult by electrophysiological methods under the noisy circumstances by electrical stimulation.Imaging of the retina by reflectance changes (RCs) is an established technique to investigate how retina is activated by electrical current (Okawa, 2007). In the present study, we evaluated RCs elicited by TES in cat eyes.
Eight eyes of 8 cats were studied under general anesthesia. Biphasic electrical pulses were delivered transcornealy for 5 ms. Fundus images observed with near-infrared light (800-880 nm) were recorded every 25 ms for 26 s, beginning 2 s before and ending 20 s after the electrical stimulation. To improve the signal-to-noise ratio, the images of ten consecutive recordings were averaged for 100 times. Two-dimensional topographic maps of the RCs were constructed by subtracting images before the stimulation from those after the stimulation.We evaluated the change of RCs to various stimulation parameters of TES (current intensity, pulse duration, frequency, stimulation time).
After TES, RCs were observed at the optic disc, retinal arteries, and retinal veins. The two-dimensional maps of the RCs elicited by TES were changed according to the stimulation parameters. The intensity of RCs significantly increased as the increase of current intensity, pulse duration and stimulation time (P < 0.05, each). The maximum RCs were also obtained when the stimulus frequency was set at 20 or 30 Hz (P<0.001).
These results showed that RCs were changed according to the stimulation parameters. RCs showed how retinal tissues were stimulated by TES, and retinal blood flow was induced in relation to the activation of retinal neurons.
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