Cone packing density in the living human retina decreases as a function of age within the foveal center with the largest difference being found at our most central measurement site. At all ages, the retina showed meridional difference in cone densities, with cone photoreceptor packing density decreasing faster with increasing eccentricity in the vertical dimensions than in the horizontal dimensions.

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Purpose To investigate the retinal microvasculature at the fovea and peripheral retina in humans using the adaptive optics scanning laser ophthalmoscope (AOSLO). To examine the association of foveal avascular zone (FAZ) and foveal pit morphology. Methods Retinal imaging of the foveal capillary network was performed on 11 subjects (15 eyes; age range 20–54) with an AOSLO. Standard deviation maps of the AOSLO images were generated from ~10–30 frames, producing high resolution maps delineating the complete capillary distribution of the retina. Foveal pit morphology was investigated in the same subjects by using a spectral domain optical coherence tomography (SDOCT). In an additional subject, only a relatively large retinal vasculature map was obtained using AOSLO. Results A well demarcated FAZ was seen in 11 subjects tested with foveal capillary imaging. There was considerable individual variation in the size and shape of the FAZ. The mean FAZ area and mean FAZ effective diameter were 0.33mm2 and 622μm, respectively. Foveal thickness was found to be negatively correlated with the FAZ effective diameter. Conclusions The structure of the capillary network could be evaluated in the fovea and parafovea using our approach. We find that a smaller FAZ is associated with a narrower foveal pit opening and a thicker fovea.

The cardiac cycle influences the blood flow velocity profiles systematically in retinal arteries but not in veins. Parabolic flow was not found in even the largest vessels studied, and deviations from parabolic flow increased in smaller vessels. The measurements are sensitive enough to measure the dual-humped blood velocity profile at a vein confluence.

We have developed a new, unified implementation of the adaptive optics scanning laser ophthalmoscope (AOSLO) incorporating a wide-field line-scanning ophthalmoscope (LSO) and a closed-loop optical retinal tracker. AOSLO raster scans are deflected by the integrated tracking mirrors so that direct AOSLO stabilization is automatic during tracking. The wide-field imager and large-spherical-mirror optical interface design, as well as a large-stroke deformable mirror (DM), enable the AOSLO image field to be corrected at any retinal coordinates of interest in a field of >25 deg. AO performance was assessed by imaging individuals with a range of refractive errors. In most subjects, image contrast was measurable at spatial frequencies close to the diffraction limit. Closed-loop optical (hardware) tracking performance was assessed by comparing sequential image series with and without stabilization. Though usually better than 10 μm rms, or 0.03 deg, tracking does not yet stabilize to single cone precision but significantly improves average image quality and increases the number of frames that can be successfully aligned by software-based post-processing methods. The new optical interface allows the high-resolution imaging field to be placed anywhere within the wide field without requiring the subject to re-fixate, enabling easier retinal navigation and faster, more efficient AOSLO montage capture and stitching.