The individual differences in cone packing density and ONL + HFL thickness are consistent with aging changes, indicating that normative aging data are necessary for fine comparisons in the early stages of disease or response to treatment. Our finding of ONL + HFL thickness increasing with aging is inconsistent with the hypothesis that ONL measurements with SDOCT depend only on the number of functioning cones, since in our older group cones were fewer, but thickness was greater.

PurposeTo investigate distances from retinal capillaries to arterioles or venules noninvasively.MethodsAn adaptive optics scanning laser ophthalmoscope (AOSLO) and optical coherence tomography angiography (OCTA) imager acquired detailed maps of retinal vasculature. Using OCTA, we quantified the distance from the edge of an arteriole or venule to the middle of the nearest capillaries (periarteriole or perivenule capillary-free zones, respectively) within the superficial vascular plexus of 20 young healthy subjects with normal axial lengths. These distances were compared to AOSLO images for three subjects. We tested the relation between the peripheral capillary-free zones and FAZ horizontal, vertical, effective diameters, and asymmetry indices in the deep vascular plexus. We examined enlargement with OCTA of capillary-free zones in a type 2 diabetic patient.ResultsThe periarteriole capillary-free zone (67.2 ± 25.3 μm) was readily visible and larger than the perivenule capillary-free zone (42.7 ± 14.4 μm), F(1, 998) = 771, P < 0.0001. The distance from foveal center (P = 0.003) and diameter (P = 0.048) were predictive of perivenule capillary-free zone values. OCTA and AOSLO corresponded for arterioles. FAZ effective diameter was positively associated with asymmetry indices, r = 0.49, P = 0.028, but not peripheral capillary-free zones, although focal enlargements were found in a diabetic patient.ConclusionsFor normal retinas, periarteriole and perivenule capillary-free zones are readily visible with OCTA and AOSLO. Periarteriole capillary-free zones were larger, consistent with arterioles carrying oxygen rich blood that diffuses to support the retina.

Large individual differences in cone densities occur even in healthy, young adults with low refractive error. We investigated whether cone density follows a simple model that some individuals have more cones, or whether individuals differ in both number and distribution of cones. We quantified cones in the eyes of 36 healthy young adults with low refractive error using a custom adaptive optics scanning laser ophthalmoscope. The average cone density in the temporal meridian was, for the mean ± SD, 43216 ± 6039, 27466 ± 3496, 14996 ± 1563, and 12207 ± 1278 cones /mm2 for 270, 630, 1480, and 2070 microns from the foveal center. Cone densities at 630 microns retinal eccentricity were uncorrelated to those at 2070 microns, ruling out models with a constant or proportional relation of cone density to eccentricity. Subjects with high central macula cone densities had low peripheral cone densities. The cone density ratio (2070 : 630 microns) was negatively correlated with cone density at 630 microns, consistent with variations in the proportion of peripheral cones migrating towards the center. We modelled the total cones within a central radius of 7 deg, using the temporal data and our published cone densities for temporal, nasal, superior, and inferior meridians. We computed an average of 221,000 cones. The coefficient of variation was 0.0767 for total cones, but higher for samples near the fovea. Individual differences occur both in total cones and other developmental factors related to cone distribution.

Purpose To develop a simplified device that performs fundus perimetry techniques, such as fixation mapping and kinetic perimetry. Methods We added visual stimulation to a near infrared retinal imager, the Laser Scanning Digital Camera (LSDC). This device uses slit scanning illumination combined with a 2 dimensional CMOS detector, with continuous viewing of the retina. The CMOS read-out was synchronized with the slit scanning, thereby serving as a confocal aperture to reduce stray light in retinal images. Series of retinal images of 36 deg were automatically aligned to provide data for fixation maps and quantification of fixation stability. The LSDC and alignment techniques also provided fundus viewing with retinal location correction for scotoma mapping. Results First, fixation mapping was readily performed in patients with central scotoma or amblyopia. The automatic alignment algorithm allowed quantification of fixation stability in patients with macular pathologies that did not cause scotoma. Second, fixation stability was rapidly and quantitatively assessed by the automatic registration of a series of retina images. There was no significant difference in the fixation stability with automatic vs. manual alignment. Kinetic perimetry demonstrated that fundus imaging helped reduce the variability of perimetric data by identifying and preventing false positives due to eye motion. We found that the size of the blind spot was significantly larger for dark targets on brighter backgrounds than when the contrast was reversed (p < 0.045). This is consistent with incremental targets being detected partially or wholly due to scattered light falling on more sensitive retinal locations. Conclusions Fundus perimetry with the LSDC allows for a wide range of fixation and perimetry tasks.