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D.R. Williams, H. Hofer, J. Carroll, M. Neitz, J. Neitz; Organization of the Human Trichromatic Cone Mosaic . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1909.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The numerosity and organization of the three classes of cones in the human trichromatic mosaic is important for color and spatial vision. While the organization of S cones has long been known, it has become possible only recently to distinguish L and M cones in the human retina. Roorda and Williams (1999) used adaptive optics to determine the numbers and arrangements of cones in 2 human subjects finding L:M of 1:1 and 4:1, and all three cone classes randomly arranged. Here we determine the organization of L, M, and S cones in the retinas of 8 new subjects and use the flicker photometric electroretinogram (ERG) to estimate the range and distribution of L:M ratio in the population. Methods: L, M, and S cone locations were determined in ~0.5 degree patches of retina at ~ 1 deg eccentricity with spatially localized retinal densitometry made possible by imaging the retina with the Rochester Adaptive Optics Ophthalmoscope. L:M ratio was estimated using the ERG over a ~70 deg field in the same subjects as well as an additional 82 color normal subjects. Results: S cones made up 4.6-6.6 % of all the cones in each mosaic in accordance with previous estimates for this retinal eccentricity. ERG estimates of cone ratio were highly correlated with those from adaptive optics indicating the validity of the ERG technique for determining relative L/M cone numerosity. L:M ratio among color-normals varied from 1:3 to 16:1, with an average of 2:1. The range was larger than suggested by previous psychophysical evidence. In accordance with the results of Roorda and Williams, L and M cones were not found to be evenly dispersed and in all mosaics patches of all L or all M cones were evident, consistent with a random assignment rule. Conclusions: Unlike S cones, there are large individual differences in the L and M cone submosaics. The high correlation of cone ratios obtained with adaptive optics and those estimated by the ERG over a large retinal field indicates that this variability is not simply local retinal variability but represents true individual differences in the organization of the cone mosaic.
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