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Yoko Hirohara, Toshifumi mihashi, Hiroyuki Kanda, Takeshi Morimoto, Tomomitsu Miyoshi, Takashi Fujikado; Functional Imaging Of The Retina In Response To Grating Light Stimuli. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4474.
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Several groups have investigated the functional imaging of the retina in which reflectance change (RC) of infrared light is observed by white light stimuli. The origin of light-evoked retinal intrinsic signal is reportedly principally in outer retinal layer (Schallek J. IOVS 2009). In this study, we recorded the RC in response to the grating light stimuli with various spatial frequencies and investigated the relationship between RC and the spatial frequency.
The retina of the left eye of a cat was observed by a functional imaging fundus camera based on a mydriasis type fundus camera (TRC-50LX, Topcon) under general anesthesia. The wavelength of the observation light was 730-780nm. The retinal images were captured 10 frames per second by a high quality CCDs. We recorded the retina for 2 seconds before, 4 seconds during, and for 20 seconds after the white light stimulation. Vertical gratings were flickered at 4Hz. The angle of the total vertical gratings was 50 degrees. The spatial frequencies of the gratings were 0.22, 0.43, 0.86, 1.73, 3.46, 6.92 cycles/deg. The averaged images of 10 repeated measurements were used to analyze the RC. We compared the average RC of the simulated area and that of non-stimulated area.
The RC showed a grating pattern at upper part of the retina and the peak was observed around 2.5 seconds after the cessation of light stimuli. We analyzed the intensity contrast (IC) of the RC in this area and found that the IC decreased logarithmically with the increase of the spatial frequency.
The retinal activity decreased logarithmically with the increase of the spatial frequency of the grating light, which may reflect the result of the image degradation by optics of the eye.
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