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D.C. Gray, W. Merigan, B. Gee, R. Tumbar, F. Reinholz, T. Twieteyer, J. Porter, J. Wolfing, D. Williams; High–Resolution in vivo Imaging of Primate Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1805.
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© ARVO (1962-2015); The Authors (2016-present)
Though single photoreceptors can now be resolved in images of the primate retina in vivo, the transparent neurons in the inner retina have proven much more difficult to resolve. We show that the labeling of ganglion cells with rhodamine dextran allows imaging of individual primate ganglion cells in the living eye.
We injected the LGN of healthy monkeys with rhodamine dextran dye, which is retrogradely transported to retinal ganglion cells (Rodieck and Watanabe, 1993). The monkey was sedated and in vivo images were acquired with a custom built, high–resolution fluorescent scanning laser ophthalmoscope. An argon/krypton laser provided 530 nm excitation light for fluorescence imaging. Direct reflectance images could also be obtained simultaneously with light from an 830 nm laser diode.
Estimated resolution of 2 microns was achieved in reflectance and fluorescent images despite the small numerical aperture and higher order aberrations of the eye. Ganglion cells were resolved in individual frames. Extended light exposure with a small intense patch of light produced enhanced fluorescence ("fireworks") similar to that observed in vitro by Dacey et al. 2003.
In vivo imaging of primate ganglion cells may be useful in a number of future applications. For example, the phototoxicity of rhodamine can be exploited to create spatially localized lesions in individual classes of ganglion cell, allowing the visual significance of these classes of cells to be revealed in psychophysical experiments. The application of adaptive optics is expected to improve resolution and may permit distinguishing different retinal ganglion cell types in vivo.
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