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T. Mihashi, Y. Hirohara, Y. Okawa, T. Miyoshi, T. Fujikado; Repeatability of Intrinsic Optical Imaging of the Retina’s Response to Optical and Electric Stimuli. Invest. Ophthalmol. Vis. Sci. 2008;49(13):894.
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© ARVO (1962-2015); The Authors (2016-present)
Intrinsic optical imaging (IOI) can be a useful clinical tool to screen the activity of retinal neurons. The use of the IOI of the retina was established by Tsunoda et al (IOVS, 2004) and Abramoff et al (IOVS, 2006). We investigated repeatability of the IOI of the animal retina because the precision should be known in future clinical applications.
Two eyes of two cats were studied under general anesthesia. We used two different kinds of stimuli. A rectangular region of the retinal was optically stimulated by visible flickering light (4 Hz). The retinal ganglion cell axons around the optic chiasm were stimulated by a train of monophasic electrical pulses. The frequency of the train was 50 Hz. The retina was observed by a fundus camera (TRC-50lx, Topcon) with near infrared light. Imaging was performed with a digital CCD camera at a frame rate of 40 frames per second. We recorded the retina for 2s before the stimulus, then for 4s during the stimulus and finally for 20s after the stimulus (Okawa, IOVS, 2007). We performed independent component (IC) analysis in which the program finds non-Gaussian components to separate the spatio-temporal signal pattern from noise. We obtained ten ICs for one analysis. Mean correlation coefficients (MCCs) of the time factor of ICs in the four measurements and analyses were calculated to investigate the similarity of the signal components between different two measurements.
The MCC of any two arbitrarily selected components between two different measurements for the light stimulation was 0.18 ± 0.17 (SD). The MCC of the two signal components was 0.85±0.05. This means that the time course of the signal components stood out among other components. We found the same degree of similarity in the stimulation of the chiasm The MCC of any two components was 0.19 ± 0.16. The MCC of the two signal components was 0.93±0.04.
We found good correlation between signals in the two measurements. The time courses of signals to the particular stimuli were often very similar. This suggests that the intrinsic optical imaging of the retina is a promising method for the clinic. We also found that the significant signal components can be selected from other components with the correlation coefficients of the time courses.
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