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Toshifumi Mihashi, Yoko Hirohara, Hiroyuki Kanda, Takeshi Morimoto, Tomomitsu Miyoshi, James Stuart Wolffsohn, Takashi Fujikado; Spatial extent of optical imaging response to light stimulation in the retina of cats. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2105.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the spatial extent of the response to light stimulation in retinal optical imaging, we recorded response intensity changes to vertical gratings with seven spatial frequencies (SFs) and analyzed them using Fourier analysis.
Retinas of the left eyes of six cats were examined by a functional imaging fundus camera (TRC-50LX, Topcon) under general anesthesia. The retinal images were photographed (observation light 730-780 nm) at a 40 Hz for 2 seconds before, 4 seconds during, and after the white light stimulation. Vertical gratings of seven kinds of SFs from 0.05 to 3.46 cycles/degree (cpd) were flickered at 4 Hz. Differential images that before and after stimulation were analyzed to obtain the contrast of response intensity (RC) against stimulus contrast on the retina by the two-dimensional Fourier transform (FFT) (Hirohara, Experimental Eye Research, 2013). The retinal contrast was estimated by using the Aston compact wavefront sensor. We performed one-dimensional Fourier analysis on the contrast data to evaluate the assumed Gaussian spatial extent as a response function. We also measured cone electroretinograms (ERG) to the same light stimuli.
We found that the fitting of Gaussian function to the contrast data was adequate. The average and standard deviation of the sigma width of the spatial extent of the optical imaging response was 0.70 and 0.12 degrees. Comparing RC and cone ERG results, RCs decreased to one-tenth up to 0.8 degrees while cone ERGs did not decay up to the same spatial frequency.
Spatial extent of the response of the optical imaging was larger than average cone spacing of the cat retina (Goodchild, 1996, J . Comp. Neurol.). With the comparison of the optical imaging to the cone ERG, the optical imaging is related to the mechanism of the internal layer of the retina.
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