The retina is an attractive source of biomarkers since it shares many features with the brain. Thickness differences in 10 retinal layers between 19 patients with mild Alzheimer’s disease (AD) and a control group of 24 volunteers were investigated. Retinal layers were automatically segmented and their thickness at each scanned point was measured, corrected for tilt and spatially normalized. When the mean thickness of entire layers was compared between patients and controls, only the outer segment layer of patients showed statistically significant thinning. However, when the layers were compared point-by point, patients showed statistically significant thinning in irregular regions ...

An algorithm for the simulation of two-dimensional spectral domain optical coherence tomography images based on Maxwell’s equations is presented. A recently developed and modified time-harmonic numerical solution of Maxwell’s equations is used to obtain scattered far fields for many wave numbers contained in the calculated spectrum. The interferometer setup with its lenses is included rigorously with Fresnel integrals and the Debye-Wolf integral. The implemented model is validated with an existing FDTD algorithm by comparing simulated tomograms of single and multiple cylindrical scatterers for perpendicular and parallel polarisation of the incident light. Tomograms are presented for different realisations of ...

Optical coherence tomography (OCT) is a cross-sectional, micrometre-scale imaging modality with widespread clinical application. Typical OCT systems sacrifice lateral resolution to achieve long depths of focus for bulk tissue imaging, and therefore tend to have better axial than lateral resolution. Such anisotropic resolution can obscure fine ultrastructural features. Furthermore, conventional OCT suffers from refraction-induced image distortions. Here, we introduce optical coherence refraction tomography (OCRT), which extends the superior axial resolution to the lateral dimension, synthesizing undistorted cross-sectional image reconstructions from multiple conventional images acquired with angular diversity. In correcting refraction-induced distortions to register the OCT images, OCRT also achieves spatially ...

Purpose To explore the impact of macular ischaemia on vision in diabetic macular oedema (DMO) by analysing the correlations between visual acuity and macular microvascular parameters using optical coherence tomography angiography (OCTA). Methods OCTA was performed in 81 eyes of 48 patients with DMO, and 3 × 3-mm 2 en face OCTA images of the superficial capillary plexus and deep capillary plexus in the central macula were retrospectively collected. Microvascular parameters including the number of microaneurysms, area of foveal avascular zone (FAZ), acircularity index of FAZ, vessel density, skeleton density, vessel density index and fractal dimension were measured. Central retinal thickness ...

Purpose To determine the intensity of corneal pigmented arc in orthokeratology (ortho-k)-treated children, and its correlation with key epithelial thickness measurements obtained by anterior segment optical coherence tomography (AS-OCT). Methods This study is a retrospective case series. Medical records of children who received ortho-k treatment for myopia control in our hospital were reviewed. Intensity of ortho-k-associated pigmented arc and its correlation with key epithelial thickness parameters in the central 7-mm-diameter zone obtained by AS-OCT was examined. The subjects were further divided into apparent and unapparent pigmented arc groups for severity comparison. Results The mean age of children was 11 ...

This study aimed to characterise the distribution of choroidal thickness (CT) in diabetic retinopathy eyes, inside and outside of the vascular arcade, as well as at the fovea, using spectral-domain optical coherence tomography (OCT). Forty-nine healthy eyes, 80 diabetic retinopathy (DR) eyes (59 non-proliferative diabetic retinopathy (NPDR) eyes and 21 proliferative diabetic retinopathy (PDR) eyes) were examined with OCT to obtain nine horizontal lines (far superotemporal, near superotemporal, central, near inferotemporal, far inferotemporal, far superonasal, near superonasal, near inferonasal, far inferonasal) inside and outside of the vascular arcade. Nine points were chosen in 0.5-mm intervals to calculate CT, which ...

Joint high-resolution multimodal photoacoustic microscopy (PAM) and optical coherence tomography (OCT) was developed to improve the efficiency for visualizing newly developed retinal neovascularization (RNV) and to monitor the dynamic changes of retinal vein occlusion (RVO) in living rabbits. The RNV and RVO models were created in New Zealand rabbits by Rose Bengal laser-induced RVO. Dual modalities imaging equipment, including color fundus photography, fluorescein angiography (FA), OCT, and PAM, was used to image and assess the changes of retinal vasculature. In vivo experimental results exhibited that not only the treatment boundaries and the position of the occluded vasculature but also the ...

Knowledge of optical properties, such as the refractive index (RI), of biological tissues is important in optical imaging, as they influence the distribution and propagation of light in tissue. To accurately study the response of cancerous cells to drugs, optimised imaging protocols are required. This study uses a simple custom-built spectral domain optical coherence tomography (OCT) system to conduct RI measurements of multicellular spheroids, three-dimensional (3D) in-vitro culture systems, of the cell line HCT116. The spheroid RIs are compared to study the effect of growth over time. To improve confocal microscopy imaging protocols, two immersion media (glycerol and ScaleView-A2) matching ...

We evaluated regression of iris neovascularization (INV) using en-face anterior-segment optical coherence tomography angiography (AS-OCTA) after anti-vascular endothelial growth factor (VEGF) therapy. Seven consecutive eyes with INV were examined before and after anti-VEGF therapy, and all AS-OCTA scans were obtained using a swept-source OCTA system with an anterior-segment lens adapter. Slit-lamp microscopy photography and anterior indocyanine green angiography also were performed. Quantitative analyses of the vascular density, vascular lacunarity, and fractal dimension on AS-OCTA images were performed. AS-OCTA visualized the INV as signals around the pupillary margin, which corresponded to the vasculature confirmed by slit-lamp microscopy. After anti-VEGF drug injection ...

The aim of this study was the assessment of the relationship between cigarette smoking and optic nerve and macular vessel density measured by optical coherence tomography angiography. We examined 30 eyes from 30 healthy habitual smokers. The examination was performed using a high-speed and high-resolution spectral-domain optical coherence tomography RTVue XR Avanti with AngioVue (Optovue, Fremont, CA, USA) with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, vascular density in the area of the optic nerve head (4.5*4.5 mm) and vascular density with the foveal avascular zone in the central macula (3.0*3.0 mm ...

Objectives To investigate vascular density analysis in the superficial (SCP) and deep capillary plexus (DCP), foveal avascular zone (FAZ), peripapillary vascular density analysis (PPCVD), and peripapillary retinal nerve fiber thickness analysis (PPRNFL) using optical coherence tomography angiography (OCTA) in pregnant women with preeclampsia and to compare the obtained values with healthy pregnant and nonpregnant healthy individuals. Methods A total of 98 pregnant women (55 had preeclampsia, 43 were healthy pregnant women) and 38 healthy nonpregnant women of reproductive age were included in the study. The patients were divided into three groups. Group 1 consisted of pregnant women with preeclampsia, group ...

The aim of this study was to assess the central macular imaging captured with an optical biometer based on full-eye-length Swept-Source OCT (SS-OCT) scan as a screening strategy for identifying macular diseases in patients scheduled for cataract surgery. 1,114 eyes of 749 consecutive patients underwent a biometrical examination with IOLMaster 700 SS-OCT technology (Carl Zeiss) and conventional Spectral-Domain OCT (SD-OCT) (Spectralis OCT, Heidelberg) device analysis on the same day. Seven examiners graded the scans individually in a full-masked mode. Twenty-five eyes were excluded for media opacities. Among the 1,089 included eyes, statistical analysis revealed a mean Kendall’s ...

n this study we developed a deep learning (DL) algorithm that detects errors in retinal never fibre layer (RNFL) segmentation on spectral-domain optical coherence tomography (SDOCT) B-scans using human grades as the reference standard. A dataset of 25,250 SDOCT B-scans reviewed for segmentation errors by human graders was randomly divided into validation plus training (50%) and test (50%) sets. The performance of the DL algorithm was evaluated in the test sample by outputting a probability of having a segmentation error for each B-scan. The ability of the algorithm to detect segmentation errors was evaluated with the area under the ...

Optical-coherence-tomography (OCT) is a non-destructive tool for biofilm imaging, not requiring staining, and used to measure biofilm thickness and putative comparison of biofilm structure based on signal intensity distributions in OCT-images. Quantitative comparison of biofilm signal intensities in OCT-images, is difficult due to the auto-scaling applied in OCT-instruments to ensure optimal quality of individual images. Here, we developed a method to eliminate the influence of auto-scaling in order to allow quantitative comparison of biofilm densities in different images. Auto- and re-scaled signal intensities could be qualitatively interpreted in line with biofilm characteristics for single and multi-species biofilms of different strains ...

The cold pressor test (CPT) induces a cardiovascular response, which may affect ocular blood flow and neuronal function. This study assessed whether optical coherence tomography angiography (OCT-A) can be used to evaluate CPT-induced changes in healthy eyes and in eyes with primary open-angle glaucoma (POAG). Twenty-two healthy subjects and 23 subjects with POAG and retinal fibre layer defects in only one hemifield were included in this study. The CPT was performed by submerging a subject’s hand in cold water (0–4 °C) for 1 minute. The results showed that baseline peripapillary and macular vessel density (VD) measurements were significantly ...

Purpose To describe the foveal characteristics of children with a history of retinopathy of prematurity (ROP) using optical coherence tomography angiography (OCTA). Methods All eyes were examined by OCTA (RTVue AVANTI, Optovue Inc, Fremont, CA) with a scan of 3 × 3 mm cantered on the fovea. The size of the foveal avascular zone (FAZ), central retinal thickness (CRT), and foveal bulge were measured. Results Forty-eight eyes of 26 children with a history of ROP and a mean age of 8.8 years with a range of 4–16 years (ROP group) were studied. Sixty-six eyes of 36 children without any ...

Aim Previous data suggest the existence of retinal vascular changes and impaired autoregulation in the very early stages of diabetic retinopathy (DR). We compared the retinal plexuses between patients with type 1 diabetes (T1D) without DR and a demographically similar healthy cohort, using optical coherence tomography angiography (OCT-A). Methods Patients with T1D and no signs of DR were prospectively recruited from an outpatient clinic. Using OCT-A (AngioVue ® ), the parafoveal superficial (SCP) and deep (DPC) capillary plexus as well as the foveal avascular zone (FAZ) and perimeter were gathered. Mean comparison tests and linear regression analysis were used as statistical tests ...

Purpose To analyze the quantitative and qualitative early changes of choroidal neovascularization (CNV) associated with chronic central serous chorioretinopathy (CSC) after treatment using optical coherence tomography-angiography (OCT-A). Methods Charts of consecutive patients with diagnosis of chronic CSC complicated by CNV were retrospectively reviewed. Included patients were divided in photodynamic therapy (PDT) or aflibercept group on the basis of the treatment received (half-fluence PDT or aflibercept 2.0 mg/0.05 ml intravitreal injection). Main outcome measures included the changes between baseline and 1-month follow-up in CNV vessel density (VD) and area on OCT-A images after thresholding and binarization. Results A ...

The recent clinical adoption of optical coherence tomography (OCT) angiography (OCTA) has enabled non-invasive, volumetric visualization of ocular vasculature at micron-scale resolutions. Initially limited to 3 mm × 3 mm and 6 mm × 6 mm fields-of-view (FOV), commercial OCTA systems now offer 12 mm × 12 mm, or larger, imaging fields. While larger FOVs promise a more complete visualization of retinal disease, they also introduce new challenges to the accurate and reliable interpretation of OCTA data. In particular, because of vignetting, wide-field imaging increases occurrence of low-OCT-signal artifacts, which leads to thresholding and/or segmentation artifacts, complicating OCTA analysis. This study presents ...

This study evaluated age-related changes in the superficial and deep retinal capillary plexus (SCP and DCP, respectively) and in the foveal avascular zone (FAZ). SCP and DCP perfusion density (PD) were measured in optical coherence tomography angiography (OCTA) macular scans of 145 eyes of 145 healthy Japanese subjects, and findings were compared with SCP FAZ and clinical data. We found that age was negatively correlated with SCP and DCP PD (r = −0.17, P  = 0.04 and r = −0.20, P  = 0.02, respectively) and positively correlated with FAZ area (r = 0.18, P  = 0.03). SCP and DCP PD ...

Our study evaluated the diagnostic capability of flow density (FD) in OCT angiography (OCTA) for diabetic retinopathy (DR) detection in diabetic patients. We studied 93 eyes of 68 diabetic patients who underwent OCTA (36 and 57 eyes without and with DR, respectively). Retinal capillary FD of a 2.6 × 2.6 mm 2 area and four divided areas at the superficial (SCP) and deep capillary plexus (DCP) were measured. Predictions were evaluated using the area under the receiver operating characteristic curve (AUC). The diagnostic capabilities of the FDs in discriminating between eyes without DR and eyes with total or early ...

The authors evaluated the proportion of choroidal neovascularization (CNV) detected by spectral-domain optical coherence tomography angiography (OCTA) in eyes with chronic central serous chorioretinopathy (CSC) (more than 3 months) with previous treatment via half-dose photodynamic therapy (PDT). All patients were followed up with at least twelve months. Macular angiograms were obtained using spectral-domain OCT (SD-OCT, RTVue XR; Optovue). CNV was defined as flow in the outer retinal slab between the outer plexiform layer and Bruch’s membrane. Clinical characteristics were compared between CNV and non-CNV groups. Seventy eyes of 61 patients (51 male and 10 female) were included. The average ...

Optical-coherence tomography (OCT) is a technique that employs light in order to measure the internal structure of semitransparent, e.g. biological, samples. It is based on the interference pattern of low-coherence light. Quantum-OCT (QOCT), instead, employs the correlation properties of entangled photon pairs, for example, generated by the process of spontaneous parametric downconversion (SPDC). The usual QOCT scheme uses photon pairs characterised by a joint-spectral amplitude with strict spectral anti-correlations. It has been shown that, in contrast with its classical counterpart, QOCT provides resolution enhancement and dispersion cancellation. In this paper, we revisit the theory of QOCT and extend the ...

Objective To evaluate the morphologic and functional outcomes of different optical coherence tomography (OCT) patterns of myopic foveoschisis after vitrectomy with Inner Limiting Membrane (ILM) peeling. Methods In this prospective non-randomised study, 62 consecutive eyes with Myopic Foveoschisis were categorised into three groups according to OCT pattern: retinoschisis type (Rt) Group (23/62), foveal detachment type (FDt) Group (20/62) and macular hole type (MHt) Group (19/62). All patients underwent 25-Gauge vitrectomy and ILM peeling. Air or gas tamponade was used. All patients were observed at month 1, 2, 4 and 6 after surgery. Main outcomes measures: surgical success ...