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Purpose: Thyroid-associated ophthalmopathy (TAO) may result in increased metabolism and abnormalities in microcirculation. The fractal dimension (Df) of retinal vessels has been shown to be related to the pathology of a number of ophthalmic disorders, but it hasn't been investigated in TAO. Methods: We analyzed 1078 participants aged 18 to 72 (548 healthy volunteers and 530 TAO). Images were captured using a non-mydriatic 45-degree fundus camera. Baseline retinal characteristics, such as vessel width, tortuosity, and Df were measured using semiautomated software from fundus images. The average retinal parameters were compared between the two groups. The receiver operation curve (ROC) was used to assess the diagnostic efficacy of various retinal vascular parameters for TAO. Results: Despite controlling for potential confounding variables, Df, vessel width, and tortuosity significantly increased in TAO compared to healthy volunteers. Compared to active TAO, patients in the inactive phase had a larger retinal venous caliber (p < 0.05), but there was no difference in Df or arterial caliber. Moderate and severe cases had a higher Df compared with mild cases (EUGOGO guidelines). The area under the ROC for Df, tortuosity, and vascular caliber in the diagnosis of TAO was 0.904 (95% CI: 0.884–0.924), 0.638 (95% CI: 0.598–0.679), and 0.617 (95% CI: 0.576–0.658), respectively. Conclusions: Due to its accessibility, affordability, and non-invasive nature, retinal vascular Df may serve as a surrogate marker for TAO and might be used to identify severe cases. With relatively high diagnostic performance, the Df is of some utility for the detection of TAO. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiaotong University (Medical Science) is the property of Journal of Shanghai Jiaotong University (Medical Science) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abnormal changes in the retinal vessel width usually indicate the presence of certain diseases. This paper presents a novel model to measure the width of retinal vessels. This method firstly employs cubic spline fitting to determine the vessel cross‐sectional direction at the center point of a vessel profile, then uses the extended edge‐searching mode to detect vessel edge points along the vessel cross‐sectional direction, and finally obtains the width value by calculating the distance between the edge point and the center point. The method can accurately locate vessel edge points and successfully solve the problem of central light reflex in blood vessels. Experimental analyses on a publicly available database show that the proposed approach has excellent performance in accuracy with other existing measurement techniques. It provides an effective idea for analyzing morphological changes in blood vessels and can be extended to obtain the shape features of other objects. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Computer-Aided Design & Computer Graphics / Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hyperglycemia in early postnatal life of preterm infants with incompletely vascularized retinas is associated with increased risk of potentially blinding neovascular retinopathy of prematurity (ROP). Neovascular ROP (Phase II ROP) is a compensatory but ultimately pathological response to the suppression of physiological postnatal retinal vascular development (Phase I ROP). Hyperglycemia in neonatal mice which suppresses physiological retinal vascular growth is associated with decreased expression of systemic and retinal fibroblast growth factor 21 (FGF21). FGF21 administration promoted and FGF21 deficiency suppressed the physiological retinal vessel growth. FGF21 increased serum adiponectin (APN) levels and loss of APN abolished FGF21 promotion of physiological retinal vascular development. Blocking mitochondrial fatty acid oxidation also abolished FGF21 protection against delayed physiological retinal vessel growth. Clinically, preterm infants developing severe neovascular ROP (versus non-severe ROP) had a lower total lipid intake with more parenteral and less enteral during the first 4 weeks of life. Our data suggest that increasing FGF21 levels in the presence of adequate enteral lipids may help prevent Phase I retinopathy (and therefore prevent neovascular disease). [ABSTRACT FROM AUTHOR]

The state of retinal vessels in fundus images is a reliable biomarker for many diseases, and the accurate segmentation of retinal vessels is important for the diagnosis of related diseases. To address the problem of many layers and high complexity of deep learningbased vascular segmentation network, this paper proposes a lightweight encoderdecoder network NAUNet by reasonably reducing the number of network layers. By introducing the DropBlock regularization strategy, the local semantic information can be discarded more effectively to motivate the network to learn more robust and effective features. Efficient attention module uses appropriate crosschannel interaction to capture richer global information. In the skip connection part, the nested connection strategy is adopted to effectively fuse the feature maps gathered from the intermediate decoder and the original feature maps from the encoder, which makes up for the semantic gap caused by direct simple connection. In addition, data augmentation is performed on the original image to improve the robustness and prevent the overfitting problem caused by insufficient data. A mixed loss function is proposed to solve the problem of class imbalance in vascular images. Finally, NAUNet was tested and achieved F1 scores of 80.92%/81.25%/74.86% and AUC values of 0.9831/0.9849/0.9841 on the DRIVE, STARE and CHASE_DB1 datasets, respectively.The number of parameters for the proposed method was only 2.66 M. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Computer-Aided Design & Computer Graphics / Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It has been proven that the deformability of red blood cells (RBC) is reduced owing to changes in mechanical properties, such as diabetes mellitus and hypertension. To probe the effects of RBC morphological and physical parameters on the flow field in bifurcated arterioles, three types of RBC models with various degrees of biconcave shapes were built based on the in vitro experimental data. The dynamic behaviors of the RBCs in shear flow were simulated to validate the feasibility of the finite element-Arbitrary Lagrangian–Eulerian method with a moving mesh. The influences of the shear rate and viscosity ratios on RBC motions were investigated. The motion of RBCs in arteriolar bifurcations was further simulated. Abnormal variations in the morphological and physical parameters of RBCs may lead to diminished tank-tread motion and enhanced tumbling motion in shear flow. Moreover, abnormal RBC variations can result in slower RBC motion at the bifurcation with a longer transmit time and greater flow resistance, which may further cause inadequate local oxygen supply. These findings would provide useful insights into the microvascular complications in diabetes mellitus. [ABSTRACT FROM AUTHOR]

The retina is one of the most metabolically active tissues in the human body. The retinal vessels provide blood to the inner retinal neurons. The retinal blood vessels are affected by diseases such as Hypertensive retinopathy and Diabetic retinopathy. The early diagnosis prevents the patients from blindness and fatality in some cases. Thus, examining the retinal blood vessels becomes an important work of an ophthalmologist. Thus, automated retinal blood vessel segmentation aids the ophthalmologist and makes their work easier. In this paper, a supervised Convolutional Neural Network (CNN) is suggested that enhances the performance of retinal blood vessel segmentation. Three publicly available datasets are used: STARE, DRIVE, and CHASE_DB1. A novel model, 'Staircase-Net,' is proposed, which has a series of up-sampling and down-sampling processes for feature extraction (extracting the thick and thin blood vessel features, respectively). The images in the datasets undergo a series of transformations in the preprocessing steps. The evaluation metrics considered are specificity, accuracy, sensitivity, and area under the curve. Finally, the proposed model results are compared with the state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

Giant cell arteritis (GCA) is a potential sight-threatening disease. Although it is associated with polymyalgia rheumatica (PMR), visual loss is not common in PMR. A retinal oximeter can be used to conduct a direct, non-invasive, in vivo assessment of the vascular system. In a cross-sectional study, we measured the retinal oxygen saturation and retinal vessel calibers in GCA patients, PMR patients, and control participants. Twenty GCA patients (38 eyes), 19 PMR patients (33 eyes), and 12 controls (20 eyes) were investigated. Images were analyzed using Oxymap Analyzer software 2.5.0 (Oxymap ehf., Reykjavik, Iceland). Groups were compared using an age- and sex-adjusted linear mixed model regression. The median (IQR) age for GCA patients was 69.0 (66.5–76.5) years, for PMR 69.0 (67.0–72.0) years, and for the controls 75.5 (71.5–81.0) years, respectively. As compared to the controls (115.3 µm), the retinal arterioles were significantly wider in patients with GCA (124.4 µm; p = 0.023) and PMR (124.8 µm; p = 0.049). No difference was found in the retinal venular caliber or vascular oxygen saturation. These results indicate that GCA and PMR patients differ similarly in the retinal arteriolar diameter compared to controls. Further studies are needed in order to clarify the underlying inflammatory mechanisms in retinal arteriolar vessels and if these parameters can be used to predict clinical outcomes. [ABSTRACT FROM AUTHOR]

There is a gap in understanding the effect of the essential ω-3 and ω-6 long-chain polyunsaturated fatty acids (LCPUFA) on Phase I retinopathy of prematurity (ROP), which precipitates proliferative ROP. Postnatal hyperglycemia contributes to Phase I ROP by delaying retinal vascularization. In mouse neonates with hyperglycemia-associated Phase I retinopathy, dietary ω-3 (vs. ω-6 LCPUFA) supplementation promoted retinal vessel development. However, ω-6 (vs. ω-3 LCPUFA) was also developmentally essential, promoting neuronal growth and metabolism as suggested by a strong metabolic shift in almost all types of retinal neuronal and glial cells identified with single-cell transcriptomics. Loss of adiponectin (APN) in mice (mimicking the low APN levels in Phase I ROP) decreased LCPUFA levels (including ω-3 and ω-6) in retinas under normoglycemic and hyperglycemic conditions. ω-3 (vs. ω-6) LCPUFA activated the APN pathway by increasing the circulating APN levels and inducing expression of the retinal APN receptor. Our findings suggested that both ω-3 and ω-6 LCPUFA are crucial in protecting against retinal neurovascular dysfunction in a Phase I ROP model; adequate ω-6 LCPUFA levels must be maintained in addition to ω-3 supplementation to prevent retinopathy. Activation of the APN pathway may further enhance the ω-3 and ω-6 LCPUFA's protection against ROP. [ABSTRACT FROM AUTHOR]

The aim of this prospective study was to compare retinal vascular diameter measurements taken from standard fundus images and adaptive optics (AO) images. We analysed retinal images of twenty healthy subjects with 45-degree funduscopic colour photographs (CR-2 Canon fundus camera, Canon™) and adaptive optics (AO) fundus images (rtx1 camera, Imagine Eyes®). Diameters were measured using three software applications: the VAMPIRE (Vessel Assessment and Measurement Platform for Images of the REtina) annotation tool, IVAN (Interactive Vessel ANalyzer) for funduscopic colour photographs, and AO_Detect_Artery™ for AO images. For the arterial diameters, the mean difference between AO_Detect_Artery™ and IVAN was 9.1 µm (−27.4 to 9.2 µm, p = 0.005) and the measurements were significantly correlated (r = 0.79). The mean difference between AO_Detect_Artery™ and VAMPIRE annotation tool was 3.8 µm (−34.4 to 26.8 µm, p = 0.16) and the measurements were poorly correlated (r = 0.12). For the venous diameters, the mean difference between the AO_Detect_Artery™ and IVAN was 3.9 µm (−40.9 to 41.9 µm, p = 0.35) and the measurements were highly correlated (r = 0.83). The mean difference between the AO_Detect_Artery™ and VAMPIRE annotation tool was 0.4 µm (−17.44 to 25.3 µm, p = 0.91) and the correlations were moderate (r = 0.41). We found that the VAMPIRE annotation tool, an entirely manual software, is accurate for the measurement of arterial and venular diameters, but the correlation with AO measurements is poor. On the contrary, IVAN, a semi-automatic software tool, presents slightly greater differences with AO imaging, but the correlation is stronger. Data from arteries should be considered with caution, since IVAN seems to significantly under-estimate arterial diameters. [ABSTRACT FROM AUTHOR]

The effective segmentation of retinal blood vessels is essential for the medical diagnosis of ophthalmology diseases. In this paper, a novel approach is presented to segment retinal vessels accurately and efficiently. Firstly, we propose a simple simplified pulse coupled neural network utilizing the similarity of adjacent neurons to acquire the basic structure of blood vessels. Then we apply a line connector to solve the problem of broken vessels occurring in the segmentation, in order to present a complete structure of the blood vessels and improve the accuracy of vessel identification. Experimental analyses on two publicly available databases show that the proposed methods with or without the line connector outperform the most existing methods in terms of average accuracy and have a fast response time. It is of great importance for medical diagnosis with high accuracy and short time consumption. Our methods are practicable either for retinal vessel segmentation, or for other applications of clinical research. [ABSTRACT FROM AUTHOR]

Many network designs in recent years have offered deeper layered solutions. However, models that achieve high-performance results with fewer layers are preferred due to causing less processing load for the system. The U-Net authors succeeded in efficiently creating a model with fewer layers. However, the U-Net architecture also requires improvement to become more efficient. For this purpose, we offer a novel encoder-decoder architecture based on the U-Net and the LU-Net. Furthermore, we propose using a reduced number of up-sampling operations, which were utilized together with the down-sampling operations intensively in the encoder section in our previous research, in the encoder part. The proposed architecture was evaluated on the IOSTAR dataset for the segmentation of retinal vessels. The preprocessing and data augmentation processes were applied to the images before training. The U-Net, LU-Net, and the proposed model were evaluated by using the accuracy, sensitivity, specificity, Dice, and Jaccard metrics. The proposed model achieved performance metric values such as an accuracy of 97.29%, a sensitivity of 81.10%, a specificity of 98.94%, a Dice coefficient of 84.66%, and a Jaccard coefficient of 73.41%. The proposed model obtained improved results compared with the other models, especially for test samples. [ABSTRACT FROM AUTHOR]

To identify various retinal pathologies like diabetic retinopathy, hypertension, glaucoma, arteriosclerosis fundus vasculature plays important role. To assist specialists for the determination of diseases it is essential to extract the retinal vasculature. This paper represents a method to segment the retinal vasculature. This paper contains four parts: first part is preprocessing which prepare funds images to extract vessels. Secondly an image enhancement includes bottom-hat transform followed by filtering. In third stage K-means is used to acquire binary segmented image; and lastly wrongly selected and detached group of pixels removed in postprocessing step. Online available databases STARE and DRIVE are used to test the method. [ABSTRACT FROM AUTHOR]

Retinal artery–vein (AV) classification is a prerequisite for quantitative analysis of retinal vessels, which provides a biomarker for neurologic, cardiac, and systemic diseases, as well as ocular diseases. Although convolutional neural networks have presented remarkable performance on AV classification, it often comes with a topological error, like an abrupt class flipping on the same vessel segment or a weakness for thin vessels due to their indistinct appearances. In this paper, we present a new method for AV classification where the underlying vessel topology is estimated to give consistent prediction along the actual vessel structure. We cast the vessel topology estimation as iterative vascular connectivity prediction, which is implemented as deep-learning-based pairwise classification. In consequence, a whole vessel graph is separated into sub-trees, and each of them is classified as an artery or vein in whole via a voting scheme. The effectiveness and efficiency of the proposed method is validated by conducting experiments on two retinal image datasets acquired using different imaging techniques called DRIVE and IOSTAR. [ABSTRACT FROM AUTHOR]

The tortuosity changes of curvilinear anatomical organs such as nerve fibers or vessels have a close relationship with a number of diseases. Therefore, the automatic estimation and representation of the tortuosity is desired in medical image for such organs. In this paper, an automated framework for tortuosity estimation is proposed for corneal nerve and retinal vessel images. First, the weighted local phase tensor-based enhancement method is employed and the curvilinear structure is extracted from raw image. For each curvilinear structure with a different position and orientation, the curvature is measured by the exponential curvature estimation in the 3D space. Then, the tortuosity of an image is calculated as the weighted average of all the curvilinear structures. Our proposed framework has been evaluated on two corneal nerve fiber datasets and one retinal vessel dataset. Experiments on three curvilinear organ datasets demonstrate that our proposed tortuosity estimation method achieves a promising performance compared with other state-of-the-art methods in terms of accuracy and generality. In our nerve fiber dataset, the method achieved overall accuray of 0.820, and 0.734, 0.881 for sensitivity and specificity, respectively. The proposed method also achieved Spearman correlation scores 0.945 and 0.868 correlated with tortuosity grading ground truth for arteries and veins in the retinal vessel dataset. Furthermore, the manual labeled 403 corneal nerve fiber images with different levels of tortuosity, and all of them are also released for public access for further research. [ABSTRACT FROM AUTHOR]

Purpose of Review: The aim of this study to is report the findings of a systemic review and meta-analysis of the literature on the association between retinal vascular caliber and cardiovascular diseases. Recent Findings: The caliber of retinal vessels has been recognized as an important biomarker for risk stratification in various cardiovascular diseases, such as coronary artery disease, heart failure, stroke, and mortality. Summary: Non-invasively quantifying retinal vasculature may be useful in screening individuals who are at risk of cardiovascular disease. Further evaluating the role of retinal vessel anatomy and incorporating it into a scoring system on risk of cardiovascular diseases are needed in future studies. [ABSTRACT FROM AUTHOR]

Retinal blood vessel extraction is considered to be the indispensable action for the diagnostic purpose of many retinal diseases. In this work, a parallel fully convolved neural network–based architecture is proposed for the retinal blood vessel segmentation. Also, the network performance improvement is studied by applying different levels of preprocessed images. The proposed method is experimented on DRIVE (Digital Retinal Images for Vessel Extraction) and STARE (STructured Analysis of the Retina) which are the widely accepted public database for this research area. The proposed work attains high accuracy, sensitivity, and specificity of about 96.37%, 86.53%, and 98.18% respectively. Data independence is also proved by testing abnormal STARE images with DRIVE trained model. The proposed architecture shows better result in the vessel extraction irrespective of vessel thickness. The obtained results show that the proposed work outperforms most of the existing segmentation methodologies, and it can be implemented as the real time application tool since the entire work is carried out on CPU. The proposed work is executed with low-cost computation; at the same time, it takes less than 2 s per image for vessel extraction. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Natural Science) is the property of Dongbei Daxue Xuebao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: To characterize the phenotype of retinal vessels using central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), tortuosity and fractal dimension (FD) in primary open‐angle glaucoma (POAG) subjects. Methods: This prospective case–control multicentre study included 61 POAG subjects and 61 controls matched for age, systemic hypertension and body mass index. Fundus images of the right eye were acquired using a non‐mydriatic camera. Central retinal artery equivalent (CRAE), CRVE, arteriole‐to‐venule ratio, FD and tortuosity of the vascular network were measured using VAMPIRE software (Vessel Assessment and Measurement Platform for Images of the Retina). Primary open‐angle glaucoma (POAG) patients underwent 24.2 sita‐standard visual field and peri‐papillary optical coherence tomography (OCT) examinations. Data were expressed as median and interquartile range (75–25th percentiles). Results: The control group was comparable to the POAG group for sex ratio, refraction and intraocular pressure. The mean CRAE and the mean CRVE were significantly lower in the POAG group than in the control group [150.5 (137.9; 157.1) μm versus 161.3 (154.0; 168.4) μm and 204.8 (190.1; 218.1) μm versus 233.5 (222.3; 246.9) μm, respectively; p < 0.001] and for fractal parameters as well. No significant difference was found for tortuosity between the two groups. There was a significant correlation between CRAE and retinal nerve fibre layer (RNFL) thickness (r = 0.27; p = 0.03). VAMPIRE parameters were not correlated with visual field indices. Conclusion: Primary open‐angle glaucoma (POAG) was associated with a narrowing of arterial and venous retinal vessels, a higher arteriole‐to‐venule ratio and lower values of FD. The relationship between CRAE and RNFL thickness needs further investigation. [ABSTRACT FROM AUTHOR]

The detection of vessels is the first step towards an automatic diagnosis and in-depth study of retinal images to aid ophthalmologists. In this paper, a real-time algorithm based on fuzzy morphological techniques is introduced to segment vessels in retinal images. This framework provides a good trade-off between expressive power and computational requirements, since the information in the local neighbourhood is quickly processed by combining a series of fast procedures. Specifically, this method is based on the fuzzy black top-hat transform, which proves to be a simple yet very effective technique. The algorithm processes images of the DRIVE and STARE datasets, in average, in 37 and 57 ms, respectively. Thus, it can be employed while a patient is being examined, embedded into more complex systems or as a pre-screening method for large volumes of data. It outstands when it is compared with other state-of-the-art methodologies in terms of its real-time processing time and its competitive performance. [ABSTRACT FROM AUTHOR]

Objectives: The examination of retinal microvascular abnormalities through fundus photography is currently the best available non‐invasive technique for assessment of cerebral vascular status. Several studies in the last decade have reported higher incidences of adverse cerebrovascular events in Schizophrenia (SCZ) and bipolar disorder (BD). However, retinal microvasculature abnormalities in SCZ and BD have remained under‐explored, and no study has compared this aspect of SCZ and BD till date. Methods: Retinal Images of 100 SCZ patients, BD patients, and healthy volunteers each were acquired by trained individuals using a non‐mydriatic camera with a 40‐degree field of view. The retinal images were quantified using a valid semi‐automated method. The average of left and right eye diameters of the venules and arterioles passing through the extended zone between 0.5 and 2 disc diameters from the optic disc were calculated. Results: The groups differed significantly with respect to average diameters of both retinal venules (P < 0.001) and retinal arterioles (P < 0.001), after controlling for age and sex. Both SCZ and BD patients had significantly narrower arterioles and wider venules compared to HV. There were also significant differences between SCZ and BD patients; patients with BD had narrower arterioles and wider venules. Conclusion: Considering the affordability and easy accessibility of the investigative procedure, retinal microvascular examination could serve as a potential screening tool to identify individuals at risk for adverse cerebrovascular events. The findings of the current study also provide a strong rationale for further systematic examination of retinal vascular abnormalities in SCZ and BD. [ABSTRACT FROM AUTHOR]

Copyright of Application Research of Computers / Jisuanji Yingyong Yanjiu is the property of Application Research of Computers Edition and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Application Research of Computers / Jisuanji Yingyong Yanjiu is the property of Application Research of Computers Edition and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The aim of the present study was to investigate age‐specific normative retinal oxygen saturation values and explore the associated factors in healthy Chinese school‐aged children with different refractive statuses. Design: Population‐based observational cross‐sectional study. Methods: Children aged 7–19 years were enrolled. Each participant underwent a series of comprehensive ocular examinations, including axial length (AL), cycloplegic refraction and Oxymap T1 imagery following cycloplegia. The acquired oximetry images were measured, and the values of the retinal oxygen saturation parameters were calculated. The independent factors of the retinal oxygen saturation were analysed using multiple linear regression. The oxygen saturation of retinal arteries (SaO2) and veins (SvO2) as well as the differences between the arteries and veins (AVD) were measured as the main outcomes. Results: In total, 1461 participants were included in the study. The mean age of the participants was 12.1 ± 3.2 years, and 53.0% were boys. The mean SaO2, SvO2 and AVD values were 83.7 ± 6.4%, 50.1 ± 5.4% and 33.6 ± 5.4%, respectively, and the values increased with age. Girls had higher SvO2 and lower AVD than boys (p < 0.05). The Pearson correlation coefficients among spherical equivalent (SE) and SaO2, SvO2 and AVD were −0.372, −0.203 and −0.240, respectively (all p < 0.001), while the correlations between AL and SaO2, SvO2 and AVD were 0.276, 0.106 and 0.221, respectively (all p < 0.001). The myopia group had significantly higher SaO2, SvO2 and AVD than the emmetropia and hyperopia groups (p < 0.001), but the high myopia group had lower SaO2 and SvO2 than the moderate myopia group. When age, gender, body mass index (BMI), intraocular pressure (IOP) and axial length (AL) were included as factors in the multiple regression, older age was associated with higher SaO2, SvO2 and AVD, while longer AL was associated with higher SaO2 and AVD. Gender was an independent factor predicting SvO2, while gender and BMI were the independent factors predicting AVD. Age explained more variance than AL in SaO2, SvO2 and AVD. Conclusions: Our population‐based study provides age‐specific profiles of retinal oxygen saturation in Chinese children and adolescents. Older age and longer AL were important independent factors of increased retinal oxygen saturation. [ABSTRACT FROM AUTHOR]

Anemia is a disease that leads to low oxygen carrying capacity in the blood. Early detection of anemia is critical for the diagnosis and treatment of blood diseases. We find that retinal vessel optical coherence tomography (OCT) images of patients with anemia have abnormal performance because the internal material of the vessel absorbs light. In this study, an automatic anemia screening method based on retinal vessel OCT images is proposed. The method consists of seven steps, namely, denoising, region of interest (ROI) extraction, layer segmentation, vessel segmentation, feature extraction, feature dimensionality reduction, and classification. We propose gradient and threshold algorithm for ROI extraction and improve region growing algorithm based on adaptive seed point for vessel segmentation. We also conduct a statistical analysis of the correlation between hemoglobin concentration and intravascular brightness and vascular shadow in OCT images before feature extraction. Eighteen statistical features and 118 texture features are extracted for classification. This study is the first to use retinal vessel OCT images for anemia screening. Experimental results demonstrate the accuracy of the proposed method is 0.8358, which indicates that the method has clinical potential for anemia screening. Graphical abstract [ABSTRACT FROM AUTHOR]

Retinal vessel segmentation is a key step towards the accurate visualization, diagnosis, early treatment and surgery planning of ocular diseases. For the last two decades, a tremendous amount of research has been dedicated in developing automated methods for segmentation of blood vessels from retinal fundus images. Despite the fact, segmentation of retinal vessels still remains a challenging task due to the presence of abnormalities, varying size and shape of the vessels, non-uniform illumination and anatomical variability between subjects. In this paper, we carry out a systematic review of the most recent advancements in retinal vessel segmentation methods published in last five years. The objectives of this study are as follows: first, we discuss the most crucial preprocessing steps that are involved in accurate segmentation of vessels. Second, we review most recent state-of-the-art retinal vessel segmentation techniques which are classified into different categories based on their main principle. Third, we quantitatively analyse these methods in terms of its sensitivity, specificity, accuracy, area under the curve and discuss newly introduced performance metrics in current literature. Fourth, we discuss the advantages and limitations of the existing segmentation techniques. Finally, we provide an insight into active problems and possible future directions towards building successful computer-aided diagnostic system. [ABSTRACT FROM AUTHOR]

Objective Type 1 diabetes mellitus (T1 DM) is a major disease affecting a large number of young patients. In the recent years, retinal vascular imaging has provided an objective assessment of vascular health in patients with T1 DM. Our study aimed to review the current literature on retinal vascular parameters in young patients with T1 DM in order to understand the following: (i) How retinal vessels are affected in T1 DM (ii) How such vascular changes can be predictive of future diabetic microvascular complications Methods We performed a systematic review and extracted relevant data from 17 articles. Results We found significant correlations between retinal vessel changes and diabetes-related risk factors (eg, hypertension, hyperlipidemia, and obesity), diabetes-related features (eg, diabetes duration and glycemic control), and diabetes-related microvascular complications (eg, diabetic retinopathy, nephropathy, and neuropathy). Conclusion Our findings suggest that retinal microvasculature is associated with both disease severity and complications in young patients with T1 DM. [ABSTRACT FROM AUTHOR]

Purpose This study aimed to elucidate the relationship between visual field defects in the upper and lower hemifields and the corresponding oxygen saturation of the retinal vessels in patients with glaucoma. Methods Patients with glaucoma ( n = 44) exhibiting more than a 10 dB difference between the upper and lower total deviation ( TD) were enrolled in the study. After measuring the retinal vessel oxygen saturation by a non-invasive spectrophotometric retinal oximeter, the hemifields in one eye of each patient were divided into worse (worse TD) and better (better TD) hemifield areas. We additionally evaluated a separate group of 40 patients with glaucoma who exhibited less than a 5 dB difference between the upper and lower TD. Statistical analysis was performed using a Student's t-test. Results A higher mean venous saturation of oxygen (SaO2) was observed in the worse (59.0 ± 8.0%) hemifield compared to the better (55.4 ± 7.2%) hemifield (p < 0.01). The mean arteriovenous difference in the SaO2 was lower in the worse (44.4 ± 9.0%) hemifield compared to the better (48.6 ± 11.4%) hemifield (p = 0.02). However, when we evaluated the worse and better hemifields in the patients who had less than a 5 dB difference in the upper and lower hemifield TD, we found no statistically significant differences for either the retinal SaO2 in the venous vessels or the arteriovenous difference. Conclusions Advanced glaucomatous visual field defects were associated with increased SaO2 in the venous vessels and a decreased arteriovenous difference in the SaO2. The present results suggest there is a reduced retinal oxygen extraction in eyes with glaucomatous damage due to retinal ganglion cell loss. [ABSTRACT FROM AUTHOR]

A remarkable number of vitreoretinal surgeries are performed each year despite their difficulty. As a result, a high demand exists for a mock-up simulator of retinal vessels to simulate these surgeries. Thus, we propose an artificial retinal vessel model for simulating microcannulation surgery. Using laser lithography, polydimethylsiloxane molding, and hydraulic transfer techniques, we fabricated microchannels approximately ≃10 μm on a 24-mm-diameter curved surface structure that mimics the human eye. In the fabrication, the channel size and wall thickness were controlled to mimic a touch of retinal vessels, which gives important information for microcannulation. We succeeded in fabrication of the proposed model and liquid circulates within the microchannels of this model without leaking. Furthermore, we demonstrated a simulation of microcannulation and measurement of applied force to the model during the simulation using a force sensor placed at the bottom of the model. The results of such experiments are useful to quantitatively evaluate medical techniques. [ABSTRACT FROM AUTHOR]

Purpose: Although Arg-Gly-Asp (RGD) motif-containing disintegrins are associated with integrin inhibition and the activation of various biological processes, little is known about the role of RGD motif-containing disintegrin in vascular development and remodeling. We therefore investigated the role of RGD-containing disintegrin in vascular remodeling in oxygen-induced retinopathy (OIR) mouse model. Materials and methods: EGT022, an RGD-containing disintegrin originated from human a disintegrin and metalloproteinase 15 (ADAM15), was used to investigate the role of the disintegrin in vascular development in OIR mouse model. To analyze the functional effects of EGT022 on retinal vascular development, the immunohistochemistry on mouse retinas after fluorescein isothiocyanate (FITC) perfusion was conducted and the vessel integrity was examined using modified Mile’s permeability assay. Results: EGT022 was able to reduce overall retinopathy scores by 75%, indicating its efficacy in retinal microvessel maturation stimulation. Pericyte coverage was greatly stimulated by EGT022 treatment in OIR mouse model. EGT022 was also effective to significantly improve blood vessel integrity. Conclusions:RGD-containing disintegrin EGT022 stimulated vascular maturation in OIR mouse model. Experimental results suggest that EGT022 is useful for treatments to improve ischemia in nonproliferative diabetic retinopathy (NPDR), the early stage of diabetic retinopathy. [ABSTRACT FROM AUTHOR]

This study describes a new method for detecting retinal vasculature. This is a useful approach for ocular diseases diagnosis. In order to determine the accuracy of the proposed method, the output of the Canny, Gabor, Frangi and LoG filters was evaluated and compared to the results generated by a matched filter. The performance of this method is evaluated by measuring the diameter of the retinal vessel in images processed by the four classic techniques and matched filter. The vessel diameter values are compared to the values provided by the ground truth retinal images. In order to underline the accuracy of the matched filter, a qualitative assessment using the Pratt's figure of merit and percentage error rate was made. [ABSTRACT FROM AUTHOR]

This study describes a new method for detecting retinal vasculature. This is a useful approach for ocular diseases diagnosis. In order to determine the accuracy of the proposed method, the output of the Canny, Gabor, Frangi and LoG filters was evaluated and compared to the results generated by a matched filter. The performance of this method is evaluated by measuring the diameter of the retinal vessel in images processed by the four classic techniques and matched filter. The vessel diameter values are compared to the values provided by the ground truth retinal images. In order to underline the accuracy of the matched filter, a qualitative assessment using the Pratt's figure of merit and percentage error rate was made. [ABSTRACT FROM AUTHOR]

Background This study investigated the long-term ophthalmological consequences of cyanotic congenital heart disease ( CHD). Design Cross-sectional study, tertiary referral setting. Participants Thirteen adults with cyanotic CHD (40 ± 4 years). Age- and sex-matched healthy controls underwent aspects of the protocol. Methods Cyanosed subjects had a full ophthalmic examination, visual fields, scanning laser ophthalmoscopy and optical coherence tomography to assess retinal nerve fibre layer ( RNFL), retinal photography and cerebral magnetic resonance imaging ( MRI). Main Outcome Measures RNFL thickness and quantitative analysis of retinal vessels with fractal dimension, branching and central retinal arterial equivalent ( CRAE) and central retinal venous equivalent ( CRVE). Results No abnormalities of anatomy, motility, intraocular pressure or anterior segments were detected apart from one subject who had bilateral cataracts. Corrected visual acuity was normal in all but one cyanosed subject. Clinical examination revealed dilated retinal vasculature in 12/13 cyanosed subjects and increased tortuosity in 8/13. In the setting of cyanosis, skeletonized retinal arterial and venous beds had higher fractal dimension and increased branching ( P ≤ 0.01, n = 11 for all); retinal vessels were dilated ( CRAE: 227 vs. 183, n = 11, P < 0.0001; CRVE: 254 vs. 221, n = 11, P = 0.01). Visual fields showed scotomas in two subjects associated with RNFL thinning. No disc oedema was detected. 6/13 subjects' RNFL thickness fell below the normal 95% confidence interval in at least one sector without explanatory cerebral pathology ( P < 0.0001, n = 13). Mean RNFL thickness correlated with MRI cerebral white matter volume (R = 0.67, P = 0.035). Conclusions Cyanosed subjects had vessel dilatation, increased branching and tortuosity. RNFL and visual field thresholds were reduced suggesting impaired neuro-ophthalmological functioning. [ABSTRACT FROM AUTHOR]

Purpose Evaluation of retinal vessels in cardiovascular disease traditionally relies upon funduscopy, but more recently digital photo analysis has expanded the spectrum. As spectral domain optical coherence tomography ( OCT) allows an in-vivo assessment of retinal tissue and its vessels on a histological scale, our study aimed at using this tool for the analysis of the retinal vasculature. Methods Circumferential peripapillary OCT scans (3D OCT-2000; Topcon Inc., Tokyo, Japan), with centration on the optic nerve head, were taken from 20 eyes (20 participants) with normal blood pressure and 20 eyes (20 participants) with arterial hypertension above 120 mmHg (mean blood pressure). The diameter of all vessels intersecting the scan line was measured in the OCT and used to calculate central vessel equivalents, and the A/V ratios were calculated. Bland-Altman analysis was performed to evaluate reliability. Correlation coefficients were determined for reliability of the method as well as with the individual mean arterial blood pressures. Results Forty eyes (40 participants) were included in the study. Mean arterial blood pressure was 96 ± 4 mmHg in the control group and 132 ± 7 mmHg in the hypertonic group. Mean A/V ratio as determined from OCT scans was 0.82 ± 0.13 (normotonic) versus 0.62 ± 0.11 (hypertonic). A Pearson's correlation coefficient of 0.67 (p < 0.001) was determined between A/V ratio and blood pressure. Conclusions Our results highlight the feasibility of retinal vessel measurements in spectral domain OCT. A relation between mean arterial blood pressure and OCT-based A/V ratio was established. Further research will elucidate influencing factors and provide a broader basis for therapeutic approaches. [ABSTRACT FROM AUTHOR]

The main part of the human eye is retina which includes blood vessels, optic disc and fovea. It's possible to segment the parts, when there is any problem in the segmented parts it can be investigating extensively. Here the first step is the extraction of the retinal vessels and then finding the problematic vessels by using the image processing techniques. Principal part analysis (PCA) is one of the techniques that can be applied to phase the blind spot. In this paper, the retinal vessel extraction, segmentation of optic disk and fovea central is victimization of PCA using the techniques canny edge detection, OD Localization Algorithm, fuzzy c-means segmentation. [ABSTRACT FROM AUTHOR]

Purpose Funduscopic assessment of the retinal vessels may be used to assess the health status of microcirculation and as a component in the evaluation of cardiovascular risk factors. Typically, the evaluation is restricted to morphological appreciation without strict quantification. Our purpose was to develop and validate a software tool for semi-automated quantitative analysis of retinal vasculature in nonmydriatic fundus photography. Methods matlab software was used to develop a semi-automated image recognition and analysis tool for the determination of the arterial-venous ( A/ V) ratio in the central vessel equivalent on 45° digital fundus photographs. Validity and reproducibility of the results were ascertained using nonmydriatic photographs of 50 eyes from 25 subjects recorded from a 3 DOCT device ( Topcon Corp.). Two hundred and thirty-three eyes of 121 healthy subjects were evaluated to define normative values. Results A software tool was developed using image thresholds for vessel recognition and vessel width calculation in a semi-automated three-step procedure: vessel recognition on the photograph and artery/vein designation, width measurement and calculation of central retinal vessel equivalents. Mean vessel recognition rate was 78%, vessel class designation rate 75% and reproducibility between 0.78 and 0.91. Mean A/ V ratio was 0.84. Application on a healthy norm cohort showed high congruence with prior published manual methods. Processing time per image was one minute. Conclusions Quantitative geometrical assessment of the retinal vasculature may be performed in a semi-automated manner using dedicated software tools. Yielding reproducible numerical data within a short time leap, this may contribute additional value to mere morphological estimates in the clinical evaluation of fundus photographs. [ABSTRACT FROM AUTHOR]

Purpose/aim: To identify retinal vascular features that precede the development of branch retinal vein occlusion (BRVO) by comparing case eyes and fellow eyes. Materials and methods: We identified 25 persons who attended an annual health screening program at Osaka Health Science Center, Osaka, Japan, and then developed BRVO in one eye between 1995 and 2009. We retrospectively reviewed retinal images of these subjects taken 1-5 years prior to the development of BRVO and compared the prevalence of retinal vascular features between case eyes and contralateral fellow eyes. Potential local retinal vascular features considered were (1) severe arterio-venous (AV) nicking, (2) a smaller angle at the crossing of the arteriole and venule, (3) double crossing, (4) crossing near venular bifurcation and (5) isolated retinopathy. The central retinal artery equivalent (CRAE), vein equivalent (CRVE) and AV ratio (CRAE divided by CRVE) were quantitatively estimated using a standardized imaging software (University of Wisconsin). Results: Compared to the fellow eye, severe AV nicking (39.1% versus 2.6%, <0.001), isolated retinopathy (47.8% versus 7.69%, p < 0.001) and a smaller angle at the crossing site (82.6% versus 46.2%, p = 0.005) were more prevalent in eyes with BRVO compared with fellow eyes. Case eyes had a significantly smaller AV ratio at 1-5 years prior to the development of BRVO compared with fellow eyes (0.68 versus 0.73, p = 0.03). Conclusions: In addition to severe AV nicking, a well-known sign linked to BRVO, this study identified two new potential retinal vascular features - isolated retinopathy and a smaller angle at the crossing site - associated with BRVO development. We also found that a discrepancy in the AV ratio between eyes (i.e. a smaller AV ratio than the fellow eye) can be a quantitative indicator of a higher BRVO risk. These findings warrant further validation in longitudinal studies. [ABSTRACT FROM AUTHOR]

Background: Microvascular changes have been associated with the metabolic syndrome. Methods: We included 869 participants aged ≥40 years from the High-risk for Diabetes Changfeng Study, who had gradable fundus photographs. On digital photographs sum retinal arteriolar and venular calibers were measured with a semi-automated system. Metabolic syndrome was defined according to the International Diabetes Federation consensus. Results: A total of 286 (32.9%) participants was diagnosed with metabolic syndrome. Participants with narrower retinal arteriolar caliber were more often diagnosed with metabolic syndrome (odds ratio 1.78, 95% confidence interval 1.02-3.10; lowest vs highest quintile). Additionally adjusting for age, gender, education, smoking and weekly activity, and adding arteriolar and venular caliber simultaneously in the same models did not alter these associations. In the component analyses, participants with narrower retinal arteriolar caliber were more likely to have central obesity, dyslipidaemia or raised blood pressure, and less likely to have raised fasting plasma glucose. The association between wider venular caliber and metabolic syndrome was less pronounced and non-significant (odds ratio 1.34; 95% confidence interval 0.79-2.38; highest vs lowest quintile). Conclusion: Retinal arteriolar narrowing and, to a lesser extent, retinal venular dilatation were associated with metabolic syndrome in this Chinese population. These vascular changes, although small in magnitude, may still be important in the patho-physiological mechanisms involved in the metabolic syndrome. [ABSTRACT FROM AUTHOR]

This study was to investigate the effect of the absence of ganglion cells on the development of human retinal vasculature. Anencephaly (AnC) and age-matched control eyes derived from each three spontaneously aborted fetus (ranging from 15 to 20 weeks gestation) were subjected to immunofluorescence staining for HIF-1α, Thy-1 , glial fibrillary acidic protein (GFAP) and platelet/endothelial cell adhesion molecule (PECAM) and apoptosis assay. In developing mouse retina, Western blotting for hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) was performed. Under hypoxic condition (O < 1%), cellular proliferation and VEGF mRNA expression in astrocytes were measured. Apoptotic cells in AnC retina were primarily localized in the ganglion cell layer (GCL), whereas apoptotic cells in normal retina were distributed in the retinoblastic layer. With increase of apoptotic cells in GCL of AnC retina, HIF-1α expression were severely distinguished in avascular retina and GFAP expression in junctional area between avascular and vascular retina was much reduced, accompanied by decrease of PECAM expression compared to normal retina. In developing mouse retina, HIF-1α and VEGF expression were high in hypoxic retina of early stage with incomplete vascular development and then progressively decreased with regression to arborous pattern of matured vascular networks. In hypoxic condition, a significant increase in cellular proliferation and VEGF mRNA expression was observed in astrocytes. Therefore, our results suggest that vascular attenuation in AnC retina could be closely related to the absence of ganglion cells as the metabolic demander to induce retinal vascular development. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to compare retinal vessel anatomy of normal rhesus monkeys and humans and to provide a basis from a structural perspective for the use of rhesus monkey as an experimental model in future studies of retinal vessels. Methods: The retinas of six normal rhesus monkey eyes and eight human eyecups following corneal transplantation were obtained and stained using adenosine diphosphatase methods. The distributions, orders, layers of the retinal vessels and the perifoveal vascular ring were compared. Results: With adenosine diphosphatase staining, distinct retinal vessels were fully discernable from the first order surrounding the optic disc to the fifth order. There were no statistically significant differences between rhesus monkeys and humans in the percentages of vessels surrounding the optic disc at the equator and the peripheral region. Vascular networks in both species were arranged in several layers around the optic disc, two anastomotic layers at the equator and one sparse layer peripherally. Capillaries at the macular area were quite dense and an intact perifoveal vascular ring was observed. No differences were observed between rhesus monkeys and humans in the percentage area of the vessels and the area, perimeter and diameter of the perifoveal vascular ring. Conclusions: The distributions, orders, layers and the perifoveal vascular ring of the retinal vessels of rhesus monkey are quite similar to those of humans. The data suggest that from an anatomical perspective, the rhesus monkey is a good animal model for the study of human retinal vessels, particularly the macular capillaries. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether a topically instilled prostaglandin analogue inhibits endothelin-1 (ET-1)-induced vasoconstrictive effects in the posterior retina by its local effects, and the duration of the effect in normal rabbit eyes. Methods: Travoprost, a potent selective FP-agonist, or unoprostone, a prostone that also has a weak non-selective FP-agonistic activity, solution was instilled once, or once daily (travoprost) or twice daily (unoprostone) for 7 days in one randomly chosen Dutch rabbit eye, and vehicle in the contralateral eye. ET-1 was intravitreously injected in both eyes 30 min after a single instillation of a test drug or its vehicle, or just after, 30, 60, 90 or 180 min after the final instillation of a 7-day instillation, and fundus photographed before, 30 and 60 min after the injection to study whether difference was seen in the ET-1-induced constriction of retinal vessels between the drug- and vehicle-instilled eyes. The same experimental procedures were conducted with indomethacin pretreatment. Results: In the rabbit eyes where travoprost was instilled for 7 days, the ET-1-induced constriction of retinal vessels was significantly inhibited only on the drug-treated side, when ET-1 was injected 30 or 60 min after the final instillation ( P = 0.026–0.005), which was abolished by indomethacin pretreatment. A single instillation of travoprost or unoprostone and 7-day instillation of unoprostone showed no effect. Conclusions: After a 7-day instillation in normal rabbit eyes, topical travoprost suppressed ET-1-induced vasoconstrictive effects only in the ipsilateral posterior retina by its local effect; this effect was maintained at least for 30 min and mediated by endogenous prostaglandins. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study is to determine the relationship between retinal abnormalities and brain white matter hyper-intensities (WMH) in symptomatic patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL). Methods: Fifteen patients with CADASIL and fifteen age-matched healthy control individuals were enrolled in this study. Ophthalmological examinations were performed on all subjects and all patients with CADASIL underwent cerebral MRI scanning. Retinal artery abnormalities were graded according to the Keith-Wagener-Barker hypertensive retinopathy classification. WMH were classified as punctuate (Grade 1), nodular or early confluent (Grade 2) and diffusly confluent (Grade 3). Partial correlation was used to assess the relationship between retinal abnormalities and WMH, controlling for age. Results: Retinal arteriole narrowing existed in 15 cases and 2 controls, with Grade 2 and Grade 3 being the most common grading of retinal artery narrowing in patients with CADASIL. All patients had WMH on MRI, rated as Grade 1 in one patient, Grade 2 in five patients and Grade 3 in nine patients. The correlation coefficient of retinal arteriole narrowing and WMH was 0.546 ( P < 0.05). Conclusion: Retinal arteriole narrowing may be associated with the severity of the cerebral lesions in CADASIL. [ABSTRACT FROM AUTHOR]

Purpose: To assess retinal vessel diameter in adult Chinese with and without glaucoma. Methods: The population-based, cross-sectional study included 4439 of the 5324 subjects asked to participate (response rate 83.4%), all aged 40 years or older. This study was divided into a rural part (1973 subjects [44.4%]) and an urban part (2466 subjects [55.6%]). Colour optic disc and fundus photographs were morphometrically examined for 2418 subjects. The retinal vessel diameters were measured at the optic disc border and at a distance of 2 mm to the optic disc border. The main outcome measure was the retinal vessel diameter. Results: Diameters of the retinal arteries were significantly ( P < 0.001) the widest in the temporal inferior region, followed by the temporal superior region ( P < 0.001), the nasal superior region ( P < 0.001) and finally the nasal inferior region. Except for the nasal inferior vein, the same held true for the retinal veins. The sequence of the main four vessel trunks with respect to their diameters was not associated with age, gender or hyperopia versus myopia. The artery diameters showed a tendency to decrease in older age, while the vein diameters decreased across all age groups. Eyes with glaucomatous optic nerve damage showed significantly ( P < 0.001) thinner arteries while the retinal vein diameters were not different. Conclusions: Diameters of the retinal arterioles and veins are the widest in the temporal inferior arcade, followed by the temporal superior arcade, the nasal superior arcade and finally the nasal inferior arcade. Retinal artery diameters decrease with glaucoma, and retinal vein diameters decrease with age. [ABSTRACT FROM AUTHOR]

To correlate the ophthalmoscopic and histological findings on human retinal blood vessels of patients with sclerosis and hypertension, respectively. Ophthalmoscopy, light microscopy, and transmission and scanning electron microscopy with histochemical staining were performed on eyes obtained from patients with a malignant orbital tumor, with absolute glaucoma, or with hypertensive retinopathy. The retinal arteries in aged patients with ophthalmoscopic sclerotic blood vessels had walls in which the smooth muscle cells had been replaced by collagen fibers, proteoglycan filaments, and ruthenium red-positive materials. The venous blood columns were hidden by numerous swollen nerve fibers and extending Müller cell processes. In a patient with accelerated hypertensive retinopathy, some of the muscle cells in the arteriolar walls were edematous. Focal and generalized narrowing of the retinal arteries appeared to be caused by a true functional constriction of the smooth muscle cells in the walls. The ophthalmoscopic signs, such as reflection of the retinal arterial blood column and crossing phenomena, were supported by sclerotic manifestations clearly visible upon histological examination. There were some organic changes in the retinal arteries in a patient with accelerated hypertensive retinopathy, but the ophthalmoscopic narrowings appeared to result from a functional constriction of the smooth muscle cells in these vessels. [ABSTRACT FROM AUTHOR]

Background: There are some cases that reported central retinal vein occlusion accompanied by ciliary artery occlusion, however, combined branch retinal artery and vein occlusion is a rare condition that has been infrequently reported. We describe in this report one case of retinal vein occlusion and branch retinal artery occlusion occurring simultaneously. Case presentation: A 50 year-old woman presented with acute visual loss in her right eye. Fundus photography showed retinal ischemia and tortuous, dilated retinal veins in the right eye. With early phase fluorescein angiography, retinal arteries revealed areas absent of branches. Late phase fluorescein angiography demonstrated that areas absent of branches were still present. Conclusion: It is a rare case of branch retinal artery and vein occlusion. [ABSTRACT FROM AUTHOR]

Background and Objective: Accurate retinal vessel segmentation is often considered to be a reliable biomarker of diagnosis and screening of various diseases, including cardiovascular diseases, diabetic, and ophthalmologic diseases. Recently, deep learning (DL) algorithms have demonstrated high performance in segmenting retinal images that may enable fast and lifesaving diagnoses. To our knowledge, there is no systematic review of the current work in this research area. Therefore, we performed a systematic review with a meta-analysis of relevant studies to quantify the performance of the DL algorithms in retinal vessel segmentation. Methods: A systematic search on EMBASE, PubMed, Google Scholar, Scopus, and Web of Science was conducted for studies that were published between 1 January 2000 and 15 January 2020. We followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) procedure. The DL-based study design was mandatory for a study's inclusion. Two authors independently screened all titles and abstracts against predefined inclusion and exclusion criteria. We used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool for assessing the risk of bias and applicability. Results: Thirty-one studies were included in the systematic review; however, only 23 studies met the inclusion criteria for the meta-analysis. DL showed high performance for four publicly available databases, achieving an average area under the ROC of 0.96, 0.97, 0.96, and 0.94 on the DRIVE, STARE, CHASE_DB1, and HRF databases, respectively. The pooled sensitivity for the DRIVE, STARE, CHASE_DB1, and HRF databases was 0.77, 0.79, 0.78, and 0.81, respectively. Moreover, the pooled specificity of the DRIVE, STARE, CHASE_DB1, and HRF databases was 0.97, 0.97, 0.97, and 0.92, respectively. Conclusion: The findings of our study showed the DL algorithms had high sensitivity and specificity for segmenting the retinal vessels from digital fundus images. The future role of DL algorithms in retinal vessel segmentation is promising, especially for those countries with limited access to healthcare. More compressive studies and global efforts are mandatory for evaluating the cost-effectiveness of DL-based tools for retinal disease screening worldwide. [ABSTRACT FROM AUTHOR]