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Y. Kazato, G. Hanazono, W. Suzuki, M. Tanifuji, M. Yuzawa, K. Tsunoda; Topography of Rod, S-Cone, and ML-Cone Photoreceptors Bleaching in Posterior Pole of Macaques Measured by Modified Fundus Camera. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2749.
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© ARVO (1962-2015); The Authors (2016-present)
The densities of cone and rod photopigments have been measured quantitatively by measuring the reflectance changes of visible light in human retinas. The densities have been determined either during the bleaching process after dark-adaptation or during the regeneration process after a full bleach. This retinal densitometry technique has been used to map the function of human retinas either by a fundus camera (Kilbride 1983, Faulkner 1984) or by a SLO (Van Norren 1989, Elsner 1992). However, the region that can be assessed is very limited, viz., central 10 degrees or small localized areas in the peripheral retina, because of the limitations of the recording devices and procedures. We have successfully imaged the functional topography of S-cones, ML-cones, and rods over the posterior pole by a modified fundus camera in anesthetized macaque’s retina.
The ocular fundus of anesthetized rhesus monkeys was monitored by a modified fundus camera system which had been developed for intrinsic signal imaging (Tsunoda, IOVS: 2004 and Hanazono, IOVS: 2007, 2008). Following 40 min of dark-adaptation, the entire posterior pole was continuously illuminated by different wavelengths of visible light (wavelength, 445, 500, 535, 565, and 630 nm; recording period, 30 sec to 10 min) and the reflectance was measured by the same light with a CCD camera. The topographic changes in the bleaching were determined by calculating the difference in reflectance between the initial image and the bleached image. The mapping was done for 40 degrees of the posterior pole.
The time course of reflectance increase had a biphasic pattern when stimulated by short wavelength light (445 and 500 nm). During the initial phase, the reflectance increased only in the region surrounding the fovea, which corresponded to the location of rods. During the second phase, a large increase in reflectance was observed at the central region including the fovea. With 445 nm, the response in the second phase appeared to correspond to the S-cone distribution. With the longer wavelengths, a large increase in reflectance was observed at the fovea which corresponds with the ML-cone distribution.
By using different wavelengths of illuminating light and analyzing the two phases of bleaching separately, the distribution of bleaching of rods, S-cones, and ML-cones could be individually mapped for the whole posterior pole region.
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