PurposeThe foveal avascular zone (FAZ) is altered in numerous diseases. We assessed factors (axial length, segmentation method, age, sex) impacting FAZ measurements from optical coherence tomography (OCT) angiography images.MethodsWe recruited 116 Caucasian subjects without ocular disease, and acquired two 3 × 3 mm AngioVue scans per each right eye (232 total scans). In images of the superficial plexus, the FAZ was segmented using the AngioVue semiautomatic nonflow measurement tool and ImageJ manual segmentation. In images from the full retinal thickness, the FAZ was segmented using the AngioAnalytics automatic FAZ tool. Repeatability, reliability, and reproducibility were calculated for FAZ measurements (acircularity, area).ResultsFAZ area (mean ± SD) for manual segmentation was 0.257 ± 0.104 mm2, greater than both semiautomatic (0.231 ± 0.0939 mm2) and automatic (0.234 ± 0.0933 mm2) segmentation (P < 0.05). Not correcting for axial length introduced errors up to 31% in FAZ area. Manual area segmentation had better repeatability (0.022 mm2) than semiautomatic (0.046 mm2) or automatic (0.060 mm2). FAZ acircularity had better repeatability with automatic than manual segmentation (0.086 vs. 0.114). Reliability of all area measurements was excellent (intraclass correlation coefficient [ICC] = 0.994 manual, 0.969 semiautomatic, 0.948 automatic). Reliability of acircularity measurements was 0.879 for manual and 0.606 for automatic.ConclusionWe identified numerous factors affecting FAZ measurements. These errors confound comparisons across studies and studies examining factors that may correlate with FAZ measures.Translational RelevanceUsing FAZ measurements as biomarkers for disease progression requires assessing and controlling for different sources of error. Not correcting for ocular magnification can result in significant inaccuracy in FAZ measurements, while choice of segmentation method affects both repeatability and accuracy.

Purpose: We examine the interocular symmetry of foveal outer nuclear layer (ONL) thickness measurements in subjects with achromatopsia (ACHM). Methods: Images from 76 subjects with CNGA3-or CNGB3-associated ACHM and 42 control subjects were included in the study. Line or volume scans through the fovea of each eye were acquired using optical coherence tomography (OCT). Image quality was assessed for each image included in the analysis using a previously-described maximum tissue contrast index (mTCI) metric. Three foveal ONL thickness measurements were made by a single observer and interocular symmetry was assessed using the average of the three measurements for each eye. Results: Mean (6 standard deviation) foveal ONL thickness for subjects with ACHM was 79.7 6 18.3 lm (right eye) and 79.2 6 18.7 lm (left eye) compared to 112.9 6 15.2 (right eye) and 112.1 6 13.9 lm (left eye) for controls. Foveal ONL thickness did not differ between eyes for ACHM (P ¼ 0.636) or control subjects (P ¼ 0.434). No significant relationship between mTCI and observer repeatability was observed for either control (P ¼ 0.140) or ACHM (P ¼ 0.351) images. Conclusions: While foveal ONL thickness is reduced in ACHM compared to controls, the high interocular symmetry indicates that contralateral ONL measurements could be used as a negative control in early-phase monocular treatment trials. Translational Relevance: Foveal ONL thickness can be measured using OCT images over a wide range of image quality. The interocular symmetry of foveal ONL thickness in ACHM and control populations supports the use of the non-study eye as a control for clinical trial purposes.

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Purpose: This study proposes an optical coherence tomography angiography (OCTA) frame-averaging method and investigates the effects of the number of frames acquired and averaged on metrics quantifying the foveal avascular zone (FAZ), vessel morphology, and parafoveal intercapillary area (PICA). Methods: Ten OCTA frames were acquired for each of the 19 subjects without known retinal disease using the AngioVue OCTA system. For each subject, acquired frames were ranked by an image quality metric. A subset of frames was then registered and averaged. The effects of the number of frames acquired and averaged on FAZ segmentation and metrics of FAZ geometry, vessel morphology, and PICA were analyzed. Results: Frame averaging increased the accuracy of the automatically segmented FAZ region; for example, the absolute error in FAZ area decreased from 0.026 mm 2 (1 frame) to 0.005 mm 2 (5 frames). Averaging multiple frames exponentially decreased the estimated number of vessel endpoints and increased the average vessel length with a 32% decrease in number of endpoints and 14% increase in average vessel length when averaging five frames compared with one. Frame averaging also improved the precision of PICA estimates. Conclusions: Averaging multiple OCTA frames using the Optovue AngioVue system reduced error in FAZ segmentation and improved the robustness of OCTA vessel morphology and perfusion metrics. The study demonstrated limited benefit in acquiring and averaging more than five frames. Translational Relevance: Averaging multiple OCTA frames improved the robustness of OCTA foveal biomarkers with limited benefit when averaging more than five frames.

PurposeTo present the case of a 37-year-old female with a foveal macrovessel.ObservationsThe patient had an incidental finding of congenital retinal macrovessel (CRM) in the left eye on optical coherence tomography (OCT). Visual acuity was normal, and slit lamp and dilated fundus examinations were otherwise unremarkable. OCT angiography (OCTA) imaging allowed for visualization of the depth profile of the vessel as well as the foveal avascular zone (FAZ). The FAZ and foveal pit were both smaller in the affected eye compared to the fellow eye.Conclusions and importanceWe describe findings of OCTA imaging in a patient with CRM. Previous reports have relied on examination using fluorescein angiography, which does not provide sufficient axial resolution to discern the different vascular plexuses. This report further characterizes how this rare condition can affect foveal morphology and retinal vasculature.

The cellular resolution provided by AOSLO affords the characterization of the photoreceptor mosaic in RPGR carriers with a TLR. Features revealed include reduced cone densities, increased cone inner segment diameters, and increased rod outer segment reflectivity.This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PurposeTo examine repeatability and reproducibility of ellipsoid zone (EZ) width measurements in patients with retinitis pigmentosa (RP) using a longitudinal reflectivity profile (LRP) analysis.MethodsWe examined Bioptigen optical coherence tomography (OCT) scans from 48 subjects with RP or Usher syndrome. Nominal scan lengths were 6, 7, or 10 mm, and the lateral scale of each scan was calculated using axial length measurements. LRPs were generated from OCT line scans, and the peak corresponding to EZ was manually identified using ImageJ. The locations at which the EZ peak disappeared were used to calculate EZ width. Each scan was analyzed twice by each of two observers, who were masked to their previous measurements and those of the other observer.ResultsOn average, horizontal width (HW) was significantly greater than vertical width (VW), and there was high interocular symmetry for both HW and VW. We observed excellent intraobserver repeatability with intraclass correlation coefficients (ICCs) ranging from 0.996 to 0.998 for HW and VW measurements. Interobserver reproducibility was also excellent for both HW (ICC = 0.989; 95% confidence interval [CI] = 0.983–0.995) and VW (ICC = 0.991; 95% CI = 0.985–0.996), with no significant bias observed between observers.ConclusionsEZ width can be measured using LRPs with excellent repeatability and reproducibility. Our observation of greater HW than VW is consistent with previous observations in RP, though the reason for this anisotropy remains unclear.Translational RelevanceWe describe repeatability and reproducibility of a method for measuring EZ width in patients with RP or Usher syndrome. This approach could facilitate measurement of retinal band thickness and/or intensity.

Cone Photoreceptors 18 19Precise: (21/35 Submitted separately as "Highlights" file) We examined the intraobserver 20 repeatability and interocular symmetry of foveal outer nuclear layer (ONL) thickness 21 measurements in patients with congenital achromatopsia. . CC-BY-NC 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/367813 doi: bioRxiv preprint first posted online Jul. 12, 2018; Purpose: To examine the intraobserver repeatability of foveal outer nuclear layer (ONL) 25 thickness measurements and evaluate interocular symmetry for patients with achromatopsia 26 (ACHM) and controls. 27Design: Cross-sectional study. 28 Subjects: Sixty-four patients with CNGA3-or CNGB3-associated ACHM and 38 patients 29 with normal vision were recruited for analysis. 30Methods: Horizontal line scans through the fovea of each eye were acquired using 31 optical coherence tomography. Three foveal ONL thickness measurements were made by a 32 single observer using custom software to analyze repeatability. Interocular symmetry was 33 assessed using the average of the three measurements for each eye.