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T. Mihashi, Y. Hirohara, Y. Okawa, T. Miyoshi, T. Fujikado; Responses of Intrinsic Optical Imaging Differ With Various Optical and Electric Stimuli. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4184.
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To investigate metabolism of the retina in vivo and non-invasively, intrinsic optical imaging is a promising method. Previous studies have reported observations of the intrinsic signals in the retina stimulated optically and electrically (Tsunoda et al, IOVS, 2004; Abramoff et al IOVS, 2006, Bizheva et al, PNAS). We have developed a functional imaging fundus camera for measuring intrinsic optical signals and also developed the analysis program based on the independent component (IC) analysis to characterize the signal from the different kinds of stimulations.
Two eyes of two cats were studied under general anesthesia. We used three kinds of stimuli. A rectangular region of the retinal was optically stimulated by visible flickering light (8 Hz). A part of the retinal was stimulated by a suprachoroidal-transretinal stimulus (STS) (Kanda et al, IOVS, 2004). Biphasic pulse trains were applied with a frequency of 50 Hz. The retinal ganglion cell axons around the optic chiasm were stimulated by a train of monophasic pulses. The frequency of the train was 50 Hz. The retina was observed by a fundus camera (TRC-50lx, Topcon) with near infrared light. We recorded the retina for 2s before stimulus, then for 4s during stimulus and finally for 20s after stimulus. We repeated the recording 20 times and averaged those data to reduce unwanted noise. To find ICs from the series of the averaged images, we estimated statistical property of images. We obtained six ICs from one series of the images and manually chose typical pattern for each stimulation.
Spatial signal patterns to the stimuli in the retina were clearly observed in the signal components for the optical stimulus (a) and for the STS (b). All time courses reasonably corresponded well to the stimulus timing. The time course of the IC to the STS (b) was similar to the time course of light scattering found in in vitro electric stimulation study (Hulshof, J. Neurosci., 1996).
We observed unique spatial and temporal responses to the three kinds of stimulations using intrinsic optical imaging.
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