The right eye of a 31-year-old woman (axial length, 23.89 mm; spherical equivalent refraction −1.00 D). A, The scanning laser ophthalmoscope (SLO) image with the superimposed Adaptive Optics (AO) retinal montage. The horizontal AO montage subtends an area of 3.67×1.46 mm. B, The optical coherence tomography (OCT) images corresponding to the 3 horizontal raster lines passing through the foveal pit (yellow triangle), showing a normal appearance of the retinal tissue. In C, the photoreceptor mosaic of the parafoveal region. The yellow squares indicate the 50×50 μm fixed windows used to estimate cone density. Eccentricity was computed as the distance between the center of each window and the foveal center. We made sure not to perform cone photoreceptors counting on regions with vessels or defects in the image quality: an underestimation of density may indeed occur when regions of missing data (e.g., blood vessels or dark areas likely due to defects in the image quality) are present into the sampling window.

A, The cone photoreceptor mosaic along the temporal meridian of the parafoveal region in the left eye of 1 subject (32-year-old woman). The Adaptive Optics (AO) montage includes an area between 0.19 mm and 1.7 mm eccentricities temporally from the foveal center. Differences in the reflectance across adjacent cone photoreceptors are often observed when imaging the photoreceptor layer. Although the origin of the cell-to-cell variability in cone reflectance remains unclear, it has been mainly related to the cell biology, including the cone outer segment pigment density. In B, C, D, and E, high-magnification images (45×90 μm) of the photoreceptor layer taken at increasing eccentricities from the foveal center: 280 μm, 560 μm, 1250 μm, and 1600 μm, respectively. Eccentricity dependent changes in cone morphology and packing are evidenced: cones are more densely packed close to the fovea and the intercone distance widens at increasing eccentricities (scale bar, 10 μm). F, A detail of the inset in E: rods could be faintly visualized as round cells (asterisks) surrounding the larger cones, as also recently shown by Dubra et al using an AO-SLO (Biomed Opt Expr 2011;2:1864). N = nasal; T = temporal.