Horizontal Line Scans Research Articles

Optical Coherence Tomography-Derived Measurements of the Optic Nerve Head Structure of Aboriginal and Torres Strait Islander Children.

This study demonstrated significant differences in optic nerve head characteristics in Aboriginal and Torres Strait Islander children compared with non-Indigenous children, which has implications for glaucoma risk and diagnosis in Aboriginal and Torres Strait Islander populations. The purpose of this study was to examine the optic nerve head (ONH) characteristics of visually normal Aboriginal and Torres Strait Islander children and non-Indigenous Australian children. Spectral domain optical coherence tomography imaging was performed on the right eye of 95 Aboriginal and Torres Strait Islander children and 149 non-Indigenous Australian children (5-18 years). Horizontal and vertical line scans, centered on the ONH, were analyzed to determine the dimensions of the ONH (Bruch membrane opening diameter), optic cup diameter, Bruch membrane opening minimum rim width, and the peripapillary retinal nerve fiber layer thickness. The vertical but not horizontal Bruch membrane opening diameter of Aboriginal and Torres Strait Islander children was significantly larger than non-Indigenous children (mean difference: 0.09mm, P = 0.001). The horizontal (mean difference: 0.12mm, P = 0.003) and vertical cup diameter (mean difference: 0.16mm, P < 0.001) were also significantly larger in Aboriginal and Torres Strait Islander children, as were the horizontal and vertical cup-to-disc ratios (both P < 0.01). Aboriginal and Torres Strait Islander children also had a significantly thinner Bruch membrane opening minimum rim width in the superior, nasal, and temporal meridians (all P < 0.001). Peripapillary retinal nerve fiber layer thickness did not differ between groups. Differences exist in the ONH structure between Aboriginal and Torres Strait Islander children and non-Indigenous children, which may have implications for the detection and monitoring of ocular disease in this population and highlights the need to extend this research to the adult population.

Genetic Diagnosis for 64 Patients with Inherited Retinal Disease.

The overlapping genetic and clinical spectrum in inherited retinal degeneration (IRD) creates challenges for accurate diagnoses. The goal of this work was to determine the genetic diagnosis and clinical features for patients diagnosed with an IRD. After signing informed consent, peripheral blood or saliva was collected from 64 patients diagnosed with an IRD. Genetic testing was performed on each patient in a Clinical Laboratory Improvement Amendments of 1988 (CLIA) certified laboratory. Mutations were verified with Sanger sequencing and segregation analysis when possible. Visual acuity was measured with a traditional Snellen chart and converted to a logarithm of minimal angle of resolution (logMAR). Fundus images of dilated eyes were acquired with the Optos® camera (Dunfermline, UK). Horizontal line scans were obtained with spectral-domain optical coherence tomography (SDOCT; Spectralis, Heidelberg, Germany). Genetic testing combined with segregation analysis resolved molecular and clinical diagnoses for 75% of patients. Ten novel mutations were found and unique genotype phenotype associations were made for the genes RP2 and CEP83. Collective knowledge is thereby expanded of the genetic basis and phenotypic correlation in IRD.

Measurement of Foveal Retinal Thickness in Myopic Patients Using Different Display Modes on Optical Coherence Tomography: A Retrospective, Cross-Sectional Study.

The aim of this work is to investigate the differences in the measurement of foveal retinal thickness in myopic patients between two display modes (1:1 pixel and 1:1 micron) on optical coherence tomography (OCT). Horizontal OCT line scan through the central fovea was used for manual measurement of foveal retinal thickness under the two display modes, and the values were compared using Wilcoxon signed-rank test. Correlations between the OCT image tilting angle (OCT ITA) and differences in OCT measurement were analyzed by Spearman's test. 127 participants with a median age of 28years, a median spherical equivalent (SE) of - 8.5 D, and a median axial length (AL) of 27.04mm. There were significant differences between the two display modes, with a median absolute difference (median relative difference) of 13.33μm (2.75%) for the central foveal thickness (CFT), 5.33μm (1.28%) for the Henle fiber and outer nuclear layer thickness (HFL + ONL), 3μm (6.47%) for the external limiting membrane to ellipsoid zone distance (ELM-EZ), and 4μm (8.77%) for the ellipsoid zone to retinal pigment epithelium distance (EZ-RPE) (all p < 0.05). The differences in foveal retinal thickness between the two display modes were significantly correlated with the OCT ITA (r = 0.732 for CFT, 0.561 for HFL + ONL, 0.642 for ELM-EZ, and 0.471 for EZ-RPE, all p < 0.05). Disparities between the two display modes were found in the manual measurement of foveal retinal thickness and correlated to the OCT ITA.

Repeatability of Choroidal Thickness Measurements in Healthy Subjects using RTVue XR Optical Coherence Tomography.

To determine the intrasession, intraobserver, interobserver, and repeatability of choroidal thickness measurements in the healthy subjects imaged on enhanced depth imaging system of RTVue XR spectral domain optical coherence tomography (OCT). In this prospective, cross-sectional study, seventy eyes of 70 healthy volunteers with no known ocular disease were imaged using high-density scanning protocol of RTVue XR OCT. In a single imaging session, three sequential 12 mm macular-enhanced depth horizontal line scans were obtained through the fovea. Two experienced examiners measured the subfoveal choroidal thickness (SFCT), choroidal thickness at 500 μm nasally and temporally from the fovea in all the eyes, using the manual calipers provided in the software. The graders were masked to each other's measurement readings. The coefficient of repeatability (CR) and intraclass correlation coefficient (ICC) were used to measure the reliability within graders. Intergrader variability was assessed using Bland-Altman method and 95% limits of agreement (LoA). Intragrader CR for grader one was 4.11 μm (95% confidence interval [CI], -2.84-11.06) for SFCT and 5.73 μm (95% CI, -3.71-15.16) for the grader two. Intragrader ICC of grader one ranged from 0.996 for SFCT to 0.994 for temporal choroidal thickness. Intragrader ICC of grader two ranged from 0.993 for temporal choroidal thickness to 0.991 for SFCT. Intergrader CR ranged from 5.24 μm (95% CI, -4.66-15.15) for SFCT to 5.89 μm (95% CI, -7.27-19.04) for temporal choroidal thickness. Intergrader 95% LoA for SFCT, nasal and temporal choroidal thickness were, -15.84-12.15 μm, -15.99-17.7 μm, and - 19.12-15.57 μm, respectively. Choroidal thickness measurements can be quantified with good repeatability using RTVue XR OCT, which would be useful in patients with chorioretinal diseases.

3D LIDAR based on FPCB mirror

This paper presents the first 3D LIDAR (light detection and ranging) constructed from two 1D FPCB (flexible printed circuit board) oscillation mirrors and one single-point LIDAR with a very low total cost of ∼$150 (assuming no additional angle sensor used). One FPCB mirror is for vertical scanning and the other is for horizontal scanning. The low cost is realized because of the low cost 1D FPCB mirror (a few dollars), as well as the widely available and relatively easy to make single-point LIDAR (<$100 cost for mass production). The 3D LIDAR can be used to obtain 3D map for navigation and obstacle avoidance of AGVs (automated guidance vehicles) subject to low speed and low acceleration. The FPCB mirror in this paper evolves from FPCB micromirrors previously developed but has a large aperture (20 × 20 mm). The achieved performance is: horizontal and vertical FOV (field of view) of 38° and 24°, respectively, 12.5 or 25 horizontal scanning lines, refreshing rate of 2, 4 or 8 fps (frames per second), 0.2∼20 m detection distance for low reflectivity object, and 1, 250∼5,000 points/frame when using the standard single-point LIDAR (TF03). If using a customized single-point LIDAR, the distance would be increased to 50∼80 m with 10 times more points/frame. The 3D LIDAR is suitable for AGV's navigation and obstacle avoidance. Modeling, prototyping and testing are presented.

HiddenGazeStereo: Hiding Gaze-Contingent Disparity Remapping for 2D-Compatible Natural 3D Viewing

Stereoscopic 3D displays (S3D), the most popular consumer display devices for 3D presentation, have a few problems that degrade the natural visual experience, such as unnatural relationships between eye vergence and accommodation, and severe image blurring (ghost) for viewers without stereo glasses. To simultaneously solve these problems, we combine gaze-contingent disparity remapping with Hidden Stereo in a manner that mutually compensates for their respective shortcomings. Gaze-contingent disparity remapping can reduce the vergence-accommodation conflict by shifting the disparity distribution around the gaze position to be centered on the display plane. Hidden Stereo can synthesize 2D-compatible 3D stereo images that do not produce any ghosting artifacts when the images for the two eyes are linearly fused. Thus, by using our new gaze-contingent display, while one viewer with glasses enjoys natural 3D content, many other glassless viewers enjoy clear 2D content. To enable real-time synthesis, we accelerate Hidden Stereo conversion by limiting the processing to each horizontal scanline. Through a user study using a variety of 3D scenes, we demonstrate that Hidden Stereo can effectively hide disparity information to glassless viewers despite the dynamic disparity manipulations. Moreover, we show that our method can alleviate the limitation of Hidden Stereo—the narrow reproducible disparity range—by manipulating the disparity so that the depth information around the gaze position is maximally preserved.

Comparison between Widefield Optical Coherence Tomography Devices in Eyes with High Myopia.

Background: To compare four different optical coherence tomography (OCT) devices for visualization of retinal and subretinal layers in highly myopic eyes. Methods: In this prospective, observational, cross-sectional study, consecutive patients with high myopia and control subjects were imaged by four OCT devices: Spectralis OCT2, PlexElite 2.0 100 kHz, PlexElite 2.0 200 kHz and the Canon Xephilio OCT-S1. The acquisition protocol for comparison consisted of single vertical and horizontal line scans centered on the fovea. Comparison between the devices in the extent of visible retina, presence of conjugate image or mirror artifacts, visibility of the sclerochoroidal interface and retrobulbar tissue. Results: 30 eyes with high myopia and 30 control subjects were analyzed. The visualized RPE length was significantly different between the OCT devices with Xephilio OCT-S1 imaging the largest extent (p < 0.0001). The proportion of eyes with conjugate image artifact was significantly higher with the Spectralis OCT (p < 0.0001), and lower with the PlexElite 200 kHz (p < 0.0001). No difference in visibility of the sclerochoroidal interface was noted among instruments. The retrobulbar tissue was visible in a higher proportion of eyes using swept-source PlexElite 100 kHz and 200 kHz (p < 0.007) compared to the other devices. Conclusions: In highly myopic eyes, the four OCT devices demonstrated significant differences in the extent of the retina imaged, in the prevalence of conjugate image artifact, and in the visualization of the retrobulbar tissue.

Assessing Ganglion Cell Layer Topography in Human Albinism Using Optical Coherence Tomography.

PurposeTo test whether ganglion cell layer (GCL) and inner plexiform layer (IPL) topography is altered in albinism.MethodsOptical coherence tomography scans were analyzed in 30 participants with albinism and 25 control participants. Horizontal and vertical line scans were acquired at the fovea, then strip registered and averaged. The Duke Optical Coherence Tomography Retinal Analysis Program was used to automatically segment the combined GCL and IPL and total retinal thickness, followed by program-assisted manual segmentation of the boundary between the GCL and IPL. Layer thickness and area under the curve (AUC) were calculated within 2.5 mm of the fovea. Nasal-temporal and superior-inferior asymmetry were calculated as an AUC ratio in each quadrant.ResultsGCL and IPL topography varied between participants. The summed AUC in all quadrants was similar between groups for both the GCL (P = 0.84) and IPL (P = 0.08). Both groups showed nasal-temporal asymmetry in the GCL, but only participants with albinism had nasal-temporal asymmetry in the IPL. Nasal-temporal asymmetry was greater in albinism for both the GCL (P < 0.0001) and the IPL (P = 0.0006). The GCL usually comprised a greater percentage of the combined GCL and IPL in controls than in albinism.ConclusionsThe GCL and IPL have greater structural variability than previously reported. GCL and IPL topography are significantly altered in albinism, which suggests differences in the spatial distribution of retinal ganglion cells. This finding provides insight into foveal development and structure-function relationships in foveal hypoplasia.

Anterior segment optical coherence tomography scanning protocols and corneal thickness repeatability

PurposeTo examine the influence of anterior segment optical coherence tomography imaging protocols on the intraobserver and intrasession repeatability of epithelial, stromal, and total corneal thickness measurements. MethodsRepeated anterior segment optical coherence tomography (AS-OCT) images (Spectralis, Heidelberg) were obtained from 15 adults using single 8.3 mm wide horizontal line scans with an average of 2, 10, 20, 30, 50 and 100 B-scans. Volumetric scans consisting of nine 8.3 mm horizontal line scans encompassing a 1.3 mm vertical region were also captured (with 20 B-scans per line scan). Single point thickness measures (at the normal to the tangent of the anterior corneal surface) were compared with thickness measures averaged over the central 6 mm. The impact of B-scan averaging and intraobserver variability were examined for single line scans. For volumetric scans, the impact of the number of line scans upon intraobserver and intrasession variability were calculated. ResultsIntraobserver repeatability did not vary significantly as a function of the number of averaged B-scans per line scan, but was lowest for 20–30 averaged B scans. For volumetric scans, increasing the number of line scans did increase scan duration (p < 0.001), with minimal impact upon the average scan quality index (p = 0.06). Averaging more than 3 line scans did not significantly improve intraobserver or intrasession repeatability for either single point or average thickness measurements. ConclusionAS-OCT volumetric scans with 3 lines each consisting of 20 B-scans with measurements averaged over a central 6 mm of the cornea provide highly repeatable measures of epithelial, stromal and total corneal thickness (95 % LoA ≤ ±3.2 μm for intraobserver repeatability and ≤ ±3.7 μm for intrasession repeatability). This scanning protocol can provide reliable information when monitoring subtle changes in corneal thickness.

Foveal Structural Analysis of Amblyopic Eyes with Two Types of Fixation Behavior by Spectral-Domain Optical Coherence Tomography.

We used spectral-domain optical coherence tomography (SD-OCT) to compare the foveal and parafoveal structures of 19 subjects aged 16-58 years (8 men, 11 women): 6 amblyopic patients with eccentric fixation, 5 amblyopic patients with central fixation, and 8 visually normal controls. We obtained foveal horizontal line scans using SD-OCT on all of the patients and controls. The total and layer thicknesses at foveal areas were analyzed. The mean (SD) ages of individuals in the eccentric fixation, central fixation, and control groups were 43.0 (13.9), 42.2 (16.3), and 38.5 (15.5) years, respectively. We observed no significant differences in the foveal or parafoveal retinal thicknesses at 500 and 1,500 μm from the foveal center among the 3 groups or between the amblyopic and fellow eyes. No significant differences were observed in the thickness of the ganglion cell complex layer or outer retinal layer at 500 and 1,500 μm from the foveal center among the three groups or between the two eyes. Overall, our SD-OCT analyses revealed no characteristic structural change in foveal regions in amblyopic eyes irrespective of the fixation behavior.

Monitoring retinal changes with optical coherence tomography predicts neuronal loss in experimental autoimmune encephalomyelitis

BackgroundRetinal optical coherence tomography (OCT) is a clinical and research tool in multiple sclerosis, where it has shown significant retinal nerve fiber (RNFL) and ganglion cell (RGC) layer thinning, while postmortem studies have reported RGC loss. Although retinal pathology in experimental autoimmune encephalomyelitis (EAE) has been described, comparative OCT studies among EAE models are scarce. Furthermore, the best practices for the implementation of OCT in the EAE lab, especially with afoveate animals like rodents, remain undefined. We aimed to describe the dynamics of retinal injury in different mouse EAE models and outline the optimal experimental conditions, scan protocols, and analysis methods, comparing these to histology to confirm the pathological underpinnings.MethodsUsing spectral-domain OCT, we analyzed the test-retest and the inter-rater reliability of volume, peripapillary, and combined horizontal and vertical line scans. We then monitored the thickness of the retinal layers in different EAE models: in wild-type (WT) C57Bl/6J mice immunized with myelin oligodendrocyte glycoprotein peptide (MOG35–55) or with bovine myelin basic protein (MBP), in TCR2D2 mice immunized with MOG35–55, and in SJL/J mice immunized with myelin proteolipid lipoprotein (PLP139–151). Strain-matched control mice were sham-immunized. RGC density was counted on retinal flatmounts at the end of each experiment.ResultsVolume scans centered on the optic disc showed the best reliability. Retinal changes during EAE were localized in the inner retinal layers (IRLs, the combination of the RNFL and the ganglion cell plus the inner plexiform layers). In WT, MOG35–55 EAE, progressive thinning of IRL started rapidly after EAE onset, with 1/3 of total loss occurring during the initial 2 months. IRL thinning was associated with the degree of RGC loss and the severity of EAE. Sham-immunized SJL/J mice showed progressive IRL atrophy, which was accentuated in PLP-immunized mice. MOG35–55-immunized TCR2D2 mice showed severe EAE and retinal thinning. MBP immunization led to very mild disease without significant retinopathy.ConclusionsRetinal neuroaxonal damage develops quickly during EAE. Changes in retinal thickness mirror neuronal loss and clinical severity. Monitoring of the IRL thickness after immunization against MOG35–55 in C57Bl/6J mice seems the most convenient model to study retinal neurodegeneration in EAE.

Sensor-Based Optimization of Terrestrial Laser Scanning Measurement Setup on GPU

A novel formulation of the set cover problem is presented to find the optimal placement of the scan stations in a terrestrial laser scanning survey. The problem is formulated in 2-D by including sensor-based constraints such as coverage and overlap. The coverage constraint ensures a minimum density of horizontal scan lines on the ground. The overlap constraint enables automatic scan alignment and registration. The optimization problem takes into account both environment occlusions and a maximum allowed incidence angle of the laser beams. The adopted laser model includes fixed parameters such as laser height, angular resolution, field of view, and minimum and maximum sensor range. The sensor placement problem is solved using a numerical approach implemented on graphics processing unit (GPU). Thanks to the GPU acceleration, experiments have been performed in large-scale environments with internal structures.

Choroidal Hyperreflective Foci: A Novel Spectral Domain Optical Coherence Tomography Biomarker in Eyes With Diabetic Macular Edema.

Purpose:The aim of this study was to examine the hyperreflective dots seen in choroid on spectral domain optical coherence tomography (SDOCT) in eyes with diabetic macular edema (DME) and correlate it with visual acuity.Design:Consecutive, cross-sectional case series of patients with DME between January 2017 and December 2017.Methods:Eyes with DME having central foveal thickness ≥250 μm were included. SDOCT was performed using Spectralis system (Heidelberg Engineering, Germany). Hyperreflective choroidal foci (HCF) were defined as well-circumscribed dots within choroid having reflectivity equal to or higher than adjacent retinal pigment epithelium. HCF were counted manually within 1500 μm of fovea using a horizontal line scan by a blinded observer. Eyes were divided in 3 groups: group A (no HCF), group B (1–10 HCF), and group C (>10 HCF).Results:One hundred nineteen eyes of 60 DME patients were included. Sixty (50.4%) eyes were in group A, whereas 42 (33.6%) and 17 (14.2%) eyes belonged to group B and group C, respectively. The mean logMAR best corrected visual acuity was significantly lower in group B (0.76 ± 0.79) and C (1.2 ± 0.78) as compared with group A (0.22 ± 0.49) (P = 0.001). Mean central foveal thickness in group A (300.4 ± 122.4 μm) was significantly lower than group B (455.52 ± 209.1 μm) and group C (529.4 ± 196.4 μm) with P value of 0.001.Conclusions:The present study describes HCF as novel prognostic SDOCT biomarker in DME whose presence denotes poor visual acuity. Further longitudinal studies are required to substantiate our findings.

The Cone Photoreceptor Mosaic in Aniridia: Within-Family Phenotype–Genotype Discordance

Investigate invivo cone photoreceptor structure in familial aniridia caused by deletion in the PAX6 gene to elucidate the complexity of between-individual variation in retinal phenotype. Descriptive case-control study. Eight persons with congenital aniridia (40-66 yrs) from 1 family and 33 normal control participants (14-69 yrs), including 7 unaffected family members (14-53 yrs). DNA was isolated from saliva samples and used in polymerase chain reaction analysis to amplify and sequence exons and intron or exon junctions of the PAX6 gene. High-resolution retinal images were acquired with OCT and adaptive optics scanning light ophthalmoscopy. Cone density (CD; in cones per square millimeter) and mosaic regularity were estimated along nasal-temporal meridians within the central 0° to 5° eccentricity. Horizontal spectral-domain OCT line scans were segmented to analyze the severity of foveal hypoplasia (FH) and to measure retinal layer thicknesses. Within-family variability in macular retinal layer thicknesses, cone photoreceptor density, and mosaic regularity in aniridia compared with normal control participants. DNA sequencing revealed a known PAX6 mutation (IV2-2delA). Those with aniridia showed variable iris phenotype ranging from almost normal appearance to no iris. Four participants with aniridia demonstrated FH grade 2, 2 demonstrated grade 3 FH, and 1 demonstrated grade 4 FH. Visual acuity ranged from 0.20 to 0.86 logarithm of the minimum angle of resolution. Adaptive optics scanning light ophthalmoscopy images were acquired from 5 family members with aniridia. Foveal CD varied between 19 899 and 55 128 cones/mm2 with overlap between the foveal hypoplasia grades. Cone density was 3 standard deviations (SDs) or more less than the normal mean within 0.5°, 2 SDs less than the normal mean at 0.5° to 4°, and more than 1 SD less than the normal mean at 5° retinal eccentricity. The results showed considerable variability in foveal development within a family carrying the same PAX6 mutation. This, together with the structural and functional variability within each grade of foveal hypoplasia, underlines the importance of advancing knowledge about retinal cellular phenotype in aniridia.

Evaluation of a workflow to derive terrestrial light detection and ranging fracture statistics of a tight gas sandstone reservoir analog

Understanding natural fracture networks in the subsurface is highly challenging, as direct one-dimensional borehole data are unable to reflect their spatial complexity, and three-dimensional seismic data are limited in spatial resolution to resolve individual meter-scale fractures. Here, we present a prototype workflow for automated fracture detection along horizontal scan lines using terrestrial light detection and ranging (t-LIDAR). Data are derived from a kilometer-scale Pennsylvanian (locally upper Carboniferous) reservoir outcrop analog in the Lower Saxony Basin, northwestern Germany. The workflow allows the t-LIDAR data to be integrated into conventional reservoir-modeling software for characterizing natural fracture networks with regard to orientation and spatial distribution. The analysis outlines the lateral reorientation of fractures from a west–southwest/east–northeast strike, near a normal fault with approximately 600 m (∼1970 ft) displacement, toward an east–west strike away from the fault. Fracture corridors, 10–20 m (33–66 ft) wide, are present in unfaulted rocks with an average fracture density of 3.4–3.9 m−1 (11.2–12.8 ft−1). A reservoir-scale digital outcrop model was constructed as a basis for data integration. The fracture detection and analysis serve as input for a stochastically modeled discrete fracture network, demonstrating the transferability of the derived data into standard hydrocarbon exploration-and-production-industry approaches. The presented t-LIDAR workflow provides a powerful tool for quantitative spatial analysis of outcrop analogs, in terms of natural fracture network characterization, and enriches classical outcrop investigation techniques. This study may contribute to a better application of outcrop analog data to naturally fractured reservoirs in the subsurface, reducing uncertainties in the characterization of this reservoir type at depth.

Interaction of High Al2O3 Refractories with Alkaline Salts Containing Potassium and Sodium in Biomass and Waste Combustion

Utilization of challenging fuels, such as biomass residues and waste-derived fuels, may lead to problems with refractory corrosion. Alkalis and chlorine in such fuels can lead to the formation of low melting deposits and slags on the refractory lining of boilers during combustion. This may cause excessive wear, possibly limiting the service lifetime of the refractories. In this work, the attack of alkali salts to high alumina refractories was studied. The refractory was exposed to four pure salts (K2CO3, K2SO4, Na2CO3, and Na2SO4) and one synthetic ash (K2CO3–KCl). The refractory was exposed to the salts at 700, 800, and 900 °C for 168 h. The penetration of potassium into the refractory was determined from horizontal line scan analyses of the sample cross section using scanning electron microscopy with energy-dispersive X-ray analysis. Detailed information on alkali infiltration was obtained by using the Xphase spectral imaging software. Additionally, X-ray diffraction analyses were made on cross sections...

Diurnal variation of choriocapillaris vessel flow density in normal subjects measured using optical coherence tomography angiography

BackgroundVessel flow density (VFD) may provide important information regarding perfusion status. Diurnal variation in VFD of choriocapillaris has not been reported in literature. In the index study, optical coherence tomography angiography (OCTA) was used to assess the diurnal variation of the VFD in the choriocapillaris of subjects with no known ocular disease.MethodsFifty eyes with no known ocular disease (25 subjects) were included. OCTA images were acquired using AngioVue (Optovue, Fremont, CA, USA) at two different time points on a single day: 9:00 AM and 6:00 PM. Macular cube scan protocol (3 × 3 mm) centered on the fovea was used. Automatic segmentation of the retinal layers and choriocapillaris was performed using ReVue software, which was also used to measure the choriocapillaris VFD. Horizontal line scan passing through fovea was obtained by the device at both time points to measure the subfoveal choroidal thickness (CT). Linear measurement tool of software was used to measure subfoveal CT according to a standardized reproducible method. Wilcoxon signed-rank test was used to assess the differences in choriocapillaris VFD and subfoveal CT at the two time points. Correlation between change in choriocapillaris VFD and subfoveal CT at the two time points was assessed using the Pearson correlation coefficient (r).ResultsThe mean age of the subjects was 31.96 ± 11.23 years. Choriocapillaris VFD was significantly higher at 9:00 AM compared to 6:00 PM (P < 0.0001) with mean choriocapillaris VFD of 68.74 ± 4.80% at 9:00 AM and 67.57 ± 5.41% at 6:00 PM, with a mean diurnal amplitude of 1.17%. Mean subfoveal CT was 287.74 ± 61.51 µm at 9:00 AM and 270.06 ± 60.73 µm at 6:00 PM. Subfoveal CT was also significantly higher at 9:00 AM compared to 6:00 PM (P < 0.0001) with a mean diurnal amplitude of 17.68 µm. Change in choriocapillaris VFD correlated with change in subfoveal CT (r = 0.87, P < 0.001).ConclusionOCTA demonstrated significant diurnal change in choriocapillaris VFD in subjects without any ocular disease with VFD being higher in the morning and lower in the evening. Decrease in choriocapillaris VFD in the evening correlated with a reduction in subfoveal CT.

Measurable Range of Subfoveal Choroidal Thickness With Conventional Spectral Domain Optical Coherence Tomography.

PurposeWe investigate the measurable range of subfoveal choroidal thickness (SFCT) with conventional spectral domain optical coherence tomography (SD-OCT) in normal healthy eyes.MethodsAll subjects underwent an SD-OCT horizontal line scan centered at the fovea with standard and enhanced depth imaging (EDI) techniques. Two independent observers manually measured SFCT on standard and EDI-OCT images, if two choroidal borders were identified. The rate of successful measurement with standard OCT was evaluated. Inter- and intraclass correlation coefficients and Bland-Altman plots were used for analysis.ResultsOCT images of 724 normal healthy eyes from 374 subjects were evaluated. Although the inner choroidal border was identified on all OCT images, the outer choroidal border was identified on 378 of 724 (52.2%) conventional OCT images. Mean SFCT of all study eyes measured by EDI-OCT images was 292.6 ± 94.0. The number of successful measurements with conventional OCT was 100%, 87.5%, 48.1%, 33.0%, and 0%, in the SFCT ranges of <241, 241–280, 281–320, 321–360, and >360 μm, respectively. The accumulated rate of successful measurement with conventional OCT was 100%, 96.4%, and 82.2% in the SFCT ranges of ≤240, ≤280, and ≤320 μm, respectively. Two protocols showed good inter-correlation of SFCT, when SFCT were measurable in both scans.ConclusionsSFCT can be measured by conventional OCT in eyes with thin choroid, and the measured value shows high agreement with those measured by EDI-OCT. In such eyes, conventional OCT can be used potentially to evaluate the retina and choroid.Translational RelevanceIn eyes with a thin choroid, conventional OCT can be used potentially to evaluate the retina and choroid with high agreement with EDI-OCT.

Posterior Choroidal Stroma Reduces Accuracy of Automated Segmentation of Outer Choroidal Boundary in Swept Source Optical Coherence Tomography

To determine the influence of choroidal boundary morphology on the accuracy of automated measurements of subfoveal choroidal thickness (SFCT) in swept source optical coherence tomography (SSOCT). A retrospective image analysis of foveal-centered horizontal line scans from normal and diseased eyes using the Topcon DRI OCT-1 Atlantis SSOCT was conducted. Subfoveal choroid-scleral junction (CSJ) and retina-choroidal junction (RCJ) morphologies were graded by two observers. Automated SFCT (A-SFCT) was compared with manual SFCT (M-SFCT) measurements from Bruch's membrane to the posterior limits of choroidal vessel, hyperreflective stroma, and hyporeflective lamina fusca. Agreement in boundary grading was assessed by Cohen's kappa. A-SFCT and M-SFCT were compared using Bland-Altman analysis and paired t-tests. A total of 200 eyes of 100 patients with a mean (SD) age of 62 (18) years were included. The choroidal vessel, stromal, and lamina fusca boundaries were visible in 100%, 58%, and 38% of the eyes, respectively. Interobserver agreement in RCJ and CSJ grading was high (kappa = 0.974 and 0.851). Mean A-SFCT differed from M-SFCT by only 2 μm at posterior choroidal vessel boundary (P = 0.801). A-SFCT overestimated SFCT at the posterior vessel wall boundary by 17 μm (P = 0.026) and 23 μm (P = 0.001) in the presence of a visible posterior choroidal stroma and lamina fusca, respectively. Automated outer choroidal boundary segmentation tends to identify the posterior limit of the choroidal vessel. Agreement between A-SFCT and M-SFCT is reduced by the presence of posterior stromal layer and lamina fusca. A-SFCT should be interpreted with RCJ and CSJ boundary grading.

Ellipsoid Zone Change According to Glaucoma Stage Advancement

To compare retinal photoreceptor ellipsoid zone (EZ) intensity between normal eyes and those with different stages of glaucoma. Retrospective cross-sectional study. The study included 37 normal, 38 preperimetric glaucoma, 39 mild-to-moderate glaucoma (visual field [VF] mean deviation [MD]:-7.7 ± 2.0 dB), and 36 severe glaucoma eyes (VF MD:-17.8 ± 3.2 dB). The subjects underwent high-resolution horizontal and vertical line scans through the fovea by spectral-domain optical coherence tomography (SD-OCT). Image processing software was employed to quantify the intensity of the first and second hyperreflective bands corresponding with the external limiting membrane (ELM) and EZ. In order to account for the brightness variation among scans, the relative EZ intensity as the ratio of the second to first reflective band (EZ/ELM) was determined. The relative EZ intensity in severe glaucoma eyes was significantly lower than in mild-to-moderate glaucoma eyes (2.46 ± 0.38 vs 3.15 ± 0.43, P < .001); also, it was lower in mild-to-moderate than in preperimetric glaucoma eyes (3.15 ± 0.43 vs 3.86 ± 0.44, P < .001). However, the comparison between preperimetric glaucoma and normal eyes showed no significant difference (3.86 ± 0.44 vs 4.06 ± 0.40, P= .751). In 75 glaucomatous eyes with VF defect, there was a significant correlation between relative EZ intensity and VF MD (r= 0.83 and P < .001). According to SD-OCT, relative EZ intensity reduction occurs in the mild-to-moderate and severe glaucoma stages. These findings suggest, at least provisionally, that in the course of glaucoma progression, mitochondrial changes in the inner segments of photoreceptors occur. Further investigation is warranted to evaluate the potential clinical significance of EZ intensity reduction in glaucoma.