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J.M. Provis, E.E. Cornish, A.E. Hendrickson; Density Profiles and Spatial Order in the S-Cone Population of Fetal and Postnatal Human Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1647.
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Purpose: To investigate developmental changes in spatial density and order in the population of short-wavelength-sensitive photoreceptors (S-cones) of human retina. Methods: The region on the horizontal meridian extending between the optic disc and fovea was selected for study because there is relatively little growth in this region beyond 17 weeks’ gestation (WG). Seven retinal wholemounts between 17 WG and 6 weeks postnatal, and one adult retina, were immunolabeled using antibody to short-wavelength-sensitive opsin and imaged by confocal microscopy. Immunoreactive profiles were counted using Scion Image and numerical density estimated at regular intervals from sample areas 250x250 µm. S-cone density was plotted as a function of eccentricity. The Density Recovery Profile (1) was used to obtain measures of regularity and cell spacing. Results: At 17 and 18 WG peak S-cone density was at 1.7 - 2.8 mm eccentricity but in specimens 20 WG and older peak S-cone density was closer to the developing fovea at eccentricities less than 780 µm. Analysis of distribution patterns indicate that before 20 WG S-cone distribution does not differ significantly from a random distribution, throughout the entire sample area. At 20 WG and in older retinae the S-cone mosaic remains indistinguishable from a random distribution near the developing fovea but at eccentricities >0.5 mm is significantly different from a random distribution. Conclusion. Developmental changes in S-cone spatial density show displacement of the photoreceptor population towards the developing fovea. The findings suggest that early in development the S-cone mosaic is random and that spatial order in the S-cone population at eccentricities >0.5mm may result from distribution changes in the cone population, possibly associated with displacement. (1) Rodieck, R. W. (1991) Visual Neuroscience 2:95-111.
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