We provide the first measures of foveal cone density as a function of axial length in living eyes and discuss the physical and visual implications of our findings. We used a new generation Adaptive Optics Scanning Laser Ophthalmoscope to image cones at and near the fovea in 28 eyes of 16 subjects. Cone density and other metrics were computed in units of visual angle and linear retinal units. The foveal cone mosaic in longer eyes is expanded at the fovea, but not in proportion to eye length. Despite retinal stretching (decrease in cones/mm2), myopes generally have a higher angular sampling density (increase in cones/deg2) in and around the fovea compared to emmetropes, offering the potential for better visual acuity. Reports of deficits in best-corrected foveal vision in myopes compared to emmetropes cannot be explained by increased spacing between photoreceptors caused by retinal stretching during myopic progression.

16 We provide the first measures of foveal cone density as a function of axial length in living eyes 17 and discuss the physical and visual implications of our findings. We used a new generation 18Adaptive Optics Scanning Laser Ophthalmoscope to image cones at and near the fovea in 28 19 eyes of 16 subjects. Cone density and other metrics were computed in units of visual angle and 20 linear retinal units. The foveal cone mosaic in longer eyes is expanded at the fovea, but not in 21proportion to eye length. Despite retinal stretching (decrease in cones/mm 2 ), myopes generally 22 have a higher angular sampling density (increase in cones/deg 2 ) in and around the fovea 23 compared to emmetropes, offering the potential for better visual acuity. Reports of deficits in 24 best-corrected foveal vision in myopes compared to emmetropes cannot be explained by 25 increased spacing between photoreceptors caused by retinal stretching during myopic 26 progression. 27 28 29 30

Citation: Foote KG, Rinella N, Tang J, et al. Cone structure persists beyond margins of short-wavelength autofluorescence in choroideremia. Invest Ophthalmol Vis Sci. 2019;60:4931-4942. https://doi.org/10.1167/ iovs.19-27979 PURPOSE. We studied the relationship between structure and function of the choriocapillaris (CC), retinal pigment epithelium (RPE), and photoreceptors in patients with choroideremia (CHM). METHODS.Six CHM patients (12 eyes) and four normal subjects (six eyes) were studied with fundus-guided microperimetry, confocal and nonconfocal adaptive optics scanning laser ophthalmoscopy (AOSLO), near-infrared and color fundus photos, short wavelength fundus autofluorescence (SW-AF), and swept-source optical coherence tomography (SS-OCT) and angiography (SS-OCTA) images. Cone spacing was represented using Z-scores (standard deviations from the mean at that eccentricity). CC flow voids were defined using a threshold of 1 SD below the normal mean. RESULTS.Cone spacing Z-scores were not significantly correlated with distance from the borders of preserved RPE, determined using either the SS-OCT or SW-AF scans. Cone spacing Z-scores were significantly correlated with CC flow voids and retinal sensitivity. Flow voids were abnormal in regions of preserved RPE and increased progressively from within À28 of the preserved area to þ28 beyond the border. Visual sensitivity decreased as CC flow voids increased approaching and beyond the border of preserved structure. CONCLUSIONS.In CHM, cone spacing Z-scores correlated with CC flow voids, and were negatively correlated with retinal sensitivity, suggesting cone degeneration accompanied reduced CC perfusion. Functional cones were found outside the presumed borders of preserved outer-retina/RPE as defined by SW-AF, but not outside the borders determined by SS-OCT. The use of SW-AF to identify the border of preserved structures may underestimate regions with cells that may be amenable to treatment.

Doppler optical coherence tomography (DOCT) combines the imaging capabilities of OCT with functional velocity imaging and is used routinely to study skin in-vivo. The skin provides a window to monitor diseases; it has been shown that changes in skin blood flow and structure are indicative of systemic disease change and representative of disease status. This study aims to aid understanding and interpretation of DOCT images of skin with respect to vessel diameter, depth and blood flow. We have constructed a tissue model using glass capillary tubes suspended at an angle of 20° to the horizontal in an Intralipid-filled tank. The Intralipid was diluted to levels which represented optimal tissue and blood flow scattering parameters. Intralipid was then pumped through the tubes to represent blood flow. The angled nature of the tubes allowed flow imaging at various depths. DOCT images were recorded using a swept-source OCT system with 1300 nm central wavelength and 6 µm axial resolution (OCMP1300SS, Thorlabs, Inc.). Data parameters extracted from images include velocity, penetration depth and their dependence on tube diameter, depth and flow. We have successfully demonstrated a tissue model that allows DOCT imaging of vessel diameter, depth and blood flow to be investigated.

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