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D.Y. Tso, Y. Kwon, R. Kardon, P. Soliz, H. Li, M. Abramoff, M. Zarella; Signal Sources Observed With Intrinsic Signal Optical Imaging Of Retina. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3495.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To better characterize the sources of functionally correlated intrinsic optical signals in the intact retina. Methods: Cat retinal images in the near–infrared (NIR, 700–900nm) were collected in vivo, while a visible (550nm) stimulus generated by a computer–driven LCD was delivered to the retina. Simultaneous ERG/PERG recordings were performed to be able to correlate the strength and characteristics of the intrinsic optical signals with an independent measure of retinal activity. Results: A series of checkerboard stimuli of increasing extents elicited a corresponding increase in area of activation. The imaged retinal response exhibited an optimal spatial frequency tuning, and weaker responses to very low spatial frequencies. Such tuning changed with retinal position (eccentricity). The strength of the PERG signal generally corresponded to the strength of the functional optical signals. The PERG signal gradually diminished with increasing spatial frequency in tandem with a decrease in optical signal strength. Multiple intrinsic signals were observed, depending on retinal location, that differed in amplitude and sign. Particularly striking was the presence of a slow, positive (increase in reflectance) optical signal that was often spatially offset to the region of the negative reflectance signal. This spatially asymmetric signal pattern may reflect the layout of the underlying retinal circulation. Conclusions: These findings suggest that a significant component of the observed signal originates from sources that have strong center–surround spatial properties. Multiple signals have been observed that may arise from the retinal circulation. Further studies will be required to more completely determine the sources of the observed optical signals. Figures: Figs 1–4, a sequence of stimuli of increasing spatial extents. Figs 5–6, responses to horizontal and vertical bar stimuli showing positive (white) and negative (black) reflectance signals. Note their spatially asymmetry. View OriginalDownload SlideView OriginalDownload Slide
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