Changes In Retinal Vasculature Research Articles

Multimodal In Vivo Imaging of Retinal and Choroidal Vascular Occlusion.

Photoacoustic microscopy (PAM) is an emerging retinal imaging technique that can provide high spatial resolution and high contrast of chorioretinal vessels. PAM is compatible with optical coherence tomography (OCT) and fluorescence imaging, allowing for development of a multimodal imaging system that combines these imaging modalities into one. This study presents a non-invasive, label-free in vivo imaging of retinal and choroidal vascular occlusion using multimodal imaging system, including PAM and OCT. Both retinal vein occlusion (RVO) and choroidal vascular occlusion (CVO) were clearly identified selectively using a spectroscopic PAM imaging. RVO and CVO were created in six rabbits using laser photocoagulation. The dynamic changes of retinal vasculature were observed and evaluated using color fundus photography, fluorescein angiography, OCT, and PAM. The position of RVO and CVO were imaged with different wavelengths ranging from 532 to 600 nm. The data shows that occluded vessels were clearly distinguished from the surrounding retinal vessels on the PAM images. This advanced imaging system is a promising technique for imaging retinal ischemia in preclinical disease models.

Sleep and eye disease: A review.

There is a growing body of literature on the effects of sleep disorders, in particular obstructive sleep apnoea (OSA), on ocular health, with consistent evidence of an increased risk of floppy eyelid syndrome, non‐arteritic anterior ischaemic optic neuropathy, diabetic macular oedema, and other retinal vasculature changes in individuals with OSA. However, reports on OSA's associations with glaucoma, papilloedema, diabetic retinopathy, central serous chorioretinopathy, and keratoconus have been conflicting, while links between OSA and age‐related macular degeneration have only been described fairly recently. Despite numerous suggestions that OSA treatment may reduce risk of these eye diseases, well‐designed studies to support these claims are lacking. In particular, the ocular hypertensive effects of continuous positive airway pressure (CPAP) therapy for OSA requires further investigation into its potential impact on glaucoma risk and management. Reports of ocular surface complications secondary to leaking CPAP masks highlights the importance of ensuring good mask fit. Poor sleep habits have also been linked with increased myopia risk; however, the evidence on this association remains weak.

DAVS-NET: Dense Aggregation Vessel Segmentation Network for retinal vasculature detection in fundus images.

In this era, deep learning-based medical image analysis has become a reliable source in assisting medical practitioners for various retinal disease diagnosis like hypertension, diabetic retinopathy (DR), arteriosclerosis glaucoma, and macular edema etc. Among these retinal diseases, DR can lead to vision detachment in diabetic patients which cause swelling of these retinal blood vessels or even can create new vessels. This creation or the new vessels and swelling can be analyzed as biomarker for screening and analysis of DR. Deep learning-based semantic segmentation of these vessels can be an effective tool to detect changes in retinal vasculature for diagnostic purposes. This segmentation task becomes challenging because of the low-quality retinal images with different image acquisition conditions, and intensity variations. Existing retinal blood vessels segmentation methods require a large number of trainable parameters for training of their networks. This paper introduces a novel Dense Aggregation Vessel Segmentation Network (DAVS-Net), which can achieve high segmentation performance with only a few trainable parameters. For faster convergence, this network uses an encoder-decoder framework in which edge information is transferred from the first layers of the encoder to the last layer of the decoder. Performance of the proposed network is evaluated on publicly available retinal blood vessels datasets of DRIVE, CHASE_DB1, and STARE. Proposed method achieved state-of-the-art segmentation accuracy using a few number of trainable parameters.

Comparison of quantitative measurement of macular vessel density before and after inferior oblique muscle–weakening surgery: An optical coherence tomography angiography study

To investigate hemodynamic changes in retinal and choroidal vasculature after surgical inferior oblique (IO) weakening through optical coherence tomography angiography (OCTA). The medical records of patients who underwent unilateral IO-weakening surgery at a single institution were retrospectively reviewed. Patients who had OCTA measurements before surgery and on postoperative days 7 and 30 were included. Vessel density was determined for the superficial capillary plexus (SCP), deep capillary plexus (DCP), the choriocapillaris (CCP) and the foveal avascular zone (FAZ). The study included 72 eyes of 36 patients. Fellow eyes were used as a control group. The preoperative and postoperative week 1 and month 1 mean central vessel densities of the SCP were 20.48%±3.52%, 20.68%±3.83%, and 23.56%±5.65%, respectively, in the operated eye; those of the DCP were 16.72%±3.33%, 16.08%±4.65%, and 20.85%±7.09%, respectively. The mean FAZ areas were 341.29±88.04μm2, 341.30±98.25μm2, and 316.02±74.61μm2, respectively. We detected no significant changes in SCP, DCP, and FAZ in the postoperative period. The mean central vessel density of the CCP increased significantly from the preoperative level of 54.06%±2.86% to 55.55%±2.63% at postoperative week 1, but there was no significant difference between baseline and postoperative month 1 (P=0.001 and P=0.515, resp.). IO muscle surgery does not seem to cause alterations in retinal hemodynamics, although it can transiently increase the central vessel density of the CCP during the early postoperative period.

Microvascular Breakdown Due to Retinal Neurodegeneration in Ataxias.

Neurodegenerative ataxias are devastating disorders of the cerebellum and spinal cord, accompanied by death of retinal ganglion cells, leading to relentlessly progressive decline of motor coordination and permanent disability. Retinal microvascular affection has not yet been determined. The aim of this study is to assess whether retinal microvascular alterations occur and, if so, whether they are concurrent with or follow cell death in the retina in neurodegenerative diseases. This study involves the cross-sectional observational study of 43 patients with ataxia and 43 controls enrolled from August 1, 2018, to September 30, 2020. The extent of ataxia was determined by the Scale for the Assessment and Rating of Ataxia. Changes in retinal vasculature were examined by optical coherence tomography angiography (OCT-A) and retinal cell and fiber density by OCT in ataxias concurrently. When comparing the ataxia cohort with healthy subjects, ataxia patients exhibited reduced vessel density in the radial peripapillary capillary (RPC) network (P=0.005), capillary density inside the optic nerve head (cdONH) (P < 0.001), nasal superficial vascular plexus (P=0.03) as well as reduced ganglion cell layer (GCL) volume (P=0.04), and temporal peripapillary retinal nerve fiber layer thickness (P=0.04). Mixed effect analysis modeling laterality confirmed these findings. These findings demonstrate a distinct pattern of concurrent changes in vessel density of the retinal superficial vascular complex, encompassing the superficial vascular plexus, RPC network and cdONH, and retinal GCL volume, providing new insights into the ongoing degeneration in ataxias. Our findings may have relevance for design of novel therapeutic approaches for ataxias and possibly other neurodegenerative diseases.

NEGATIVE VESSEL REMODELING IN STARGARDT DISEASE QUANTIFIED WITH VOLUME-RENDERED OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

To quantify retinal vasculature changes in Stargardt disease1 (STGD1) with volume-rendered optical coherence tomography angiography. Optical coherence tomography angiography volumes from healthy subjects and two subgroups of patients with STGD1 with the presence/absence of definitely decreased autofluorescence areas were compared. Optical coherence tomography angiography vessel surface area and vessel volume were measured in central zones (Z) of 1-, 2-, and 3-mm diameter. Twenty nine eyes of 15 patients with STGD1 (20/9 eyes with/without definitely decreased autofluorescence) and 30 eyes of 15 controls contributed data. An enlarged foveal avascular zone was found in patients with STGD1 without and even more with definitely decreased autofluorescence associated with a vessel rarefication in central and also paracentral zones with unnoticeable autofluorescence. Vessel surface area and vessel volume were reduced in both STGD1 subgroups for all zones (P < 0.0001). Stargardt disease 1 eyes when compared to without definitely decreased autofluorescence showed reduced vessel surface area and vessel volume in Z2+3 (both P < 0.05). Volume rendering of optical coherence tomography angiography in STGD1 shows a reduced retinal flow in the central macula. This is most likely secondary to loss of neurosensory tissue with disease progression and therefore not likely be favorably influenced by gene transfer and retinal pigment epithelial transplantation. Retinal blood flow assessed by 3D volume-rendered optical coherence tomography angiography could serve as surrogate marker for vascular changes of the central retina.

An Intelligent Information Management System for Retinal Image Storage and Recognition in Chronic Disease using Digital Signal and Image Processing

Retinal imaging plays a very significant role in the study of retinal vasculature changes indicative of chronic disease information related to vision. This study investigates the invulnerability of retinal image information in the disease information system and assesses the quantitative method of the morphological changes in the retinal vascular network. In this work, the medical digital image transmission protocol Digital Imaging &amp; Communications in Medicine (DICOM) version 3.0 and the retinal image Picture Archiving &amp; Communication System (PACS) were constructed in the laboratory using browser/server mode. Also, the DICOM-SR document was designed in this article using a list or hierarchy, and the retinal images to report the information of patients by using the Hypertext Transfer Protocol (HTTP) – based Web Access to DICOM Persistent Objects (WADO) approach. The results showed that the retinal image PACS system constructed in Browser/Server mode can effectively store and transmit DICOM images. When the imaging device is combined with the application program, special adapters are used to negotiate the transmission syntax. The message flow is decoded in the communication process, which can be connected with the realization to improve the efficiency of information collection. The proposed PACS system integrates the quantitative features of retina providing more meaningful research data for data mining in comparison to the traditional state of the art methods based on chronic disease management system. The diagnostic ability of the retinal imaging procedure using the DICOM images is justified by obtaining 98.51%, 98.04%, 99% and 99.01% of accuracy, sensitivity, specificity and precision values respectively.

A Systematic Review of Carotenoids in the Management of Diabetic Retinopathy.

Diabetic retinopathy, which was primarily regarded as a microvascular disease, is the leading cause of irreversible blindness worldwide. With obesity at epidemic proportions, diabetes-related ocular problems are exponentially increasing in the developed world. Oxidative stress due to hyperglycemic states and its associated inflammation is one of the pathological mechanisms which leads to depletion of endogenous antioxidants in retina in a diabetic patient. This contributes to a cascade of events that finally leads to retinal neurodegeneration and irreversible vision loss. The xanthophylls lutein and zeaxanthin are known to promote retinal health, improve visual function in retinal diseases such as age-related macular degeneration that has oxidative damage central in its etiopathogenesis. Thus, it can be hypothesized that dietary supplements with xanthophylls that are potent antioxidants may regenerate the compromised antioxidant capacity as a consequence of the diabetic state, therefore ultimately promoting retinal health and visual improvement. We performed a comprehensive literature review of the National Library of Medicine and Web of Science databases, resulting in 341 publications meeting search criteria, of which, 18 were found eligible for inclusion in this review. Lutein and zeaxanthin demonstrated significant protection against capillary cell degeneration and hyperglycemia-induced changes in retinal vasculature. Observational studies indicate that depletion of xanthophyll carotenoids in the macula may represent a novel feature of DR, specifically in patients with type 2 or poorly managed type 1 diabetes. Meanwhile, early interventional trials with dietary carotenoid supplementation show promise in improving their levels in serum and macular pigments concomitant with benefits in visual performance. These findings provide a strong molecular basis and a line of evidence that suggests carotenoid vitamin therapy may offer enhanced neuroprotective effects with therapeutic potential to function as an adjunct nutraceutical strategy for management of diabetic retinopathy.

The Structural and Comparative Analysis of Intravitreal Dexamethasone Implant (Ozurdex) and Anti-VEGF Injection in Branched Retinal Vein Occlusion Patients by Optical Coherence Tomography Angiography Images Quantitation

ABSTRACT Background and Objective: To evaluate and compare the structural changes of retinal vasculature after intravitreal dexamethasone implant (Ozurdex) insertion and antivascular endothelial growth factor (anti-VEGF) injection in patients with branched retinal vein occlusion (BRVO) using optical coherence tomography angiography (OCTA). Study Design/Materials and Methods: We retrospectively analyzed 39 patients with unilateral BRVO. Subjects were divided into two groups according to treatment agent: Ozurdex (n = 18) and anti-VEGF (n = 21). Swept Source (SS) OCT and OCTA were performed and images were analyzed quantitatively using ImageJ (National Institutes of Health) software. Intravitreal implant and anti-VEGF injections were performed following a prn regimen. The specific anti-VEGF agent used was chosen among bevacizumab, ranibizumab and aflibercept. Results: Of the 39 patients (mean ± SD age, 70.0 ± 8.9 years [range, 48–89 years]; 20 men [51.0%]) with unilateral BRVO, in an independent two-sample t test, there was greater vascular reperfusion of the choriocapillaris slab in the intravitreal Ozurdex implant group than in the anti-VEGF group using the angiography mode (P = .013). Increased number of particles was more prominent in intravitreal anti-VEGF injection group than intravitreal Ozurdex implant group in outer retina slab of En-face mode (P = .039). There was no statistically significant difference between the 2 treatment groups in relation to the Early Treatment Diabetic Retinopathy Study (ETDRS) density map and other angiography slabs; and the superficial, deep, and outer retina. Conclusions: Results of a quantitative analysis of OCTA images using ImageJ software suggest that the intravitreal Ozurdex implant induced increased retinal vascular perfusion compared with anti-VEGF injection for the treatment of BRVO.

Optical Coherence Tomography Angiography for the Evaluation of Retinal Vasculature in Fabry Disease: Our Experience and Review of Current Knowledge.

Purpose: Optical coherence tomography angiography (OCTA) is a non-invasive and objective tool for the evaluation of the retinal microvascular changes in Fabry disease (FD). We investigated changes in retinal vasculature in FD patients, and the possible correlation with systemic parameters, by using OCTA, and reviewed the current status of literature.Methods: Thirteen FD patients (eight females, five males, mean age 49.85 ± 14.7 years) were compared with 13 age- and sex-matched healthy controls. OCTA 3 × 3 mm macular scans were performed in all subjects. We evaluated the vessel density and vessel perfusion in distinct macular areas (whole, inner, and outer) of both the superficial capillary plexus (SCP VD and SCP VP) and of the deep capillary plexus (DCP VD and DCP VP). We also evaluated the foveal avascular zone (FAZ) metrics (area, perimeter, and circularity), and correlation between systemic and OCTA parameters. A literature review on the current understanding of OCTA in FD is then presented.Results: FD patients showed significantly lower SCP VD values in the whole area (17.37 ± 2.08 mm−1 vs. 18.54 ± 1.21 mm−1; p-value 0.022), as well as in the outer area (17.46 ± 2.10 mm−1 vs. 19.08 ± 1.14 mm−1; p-value 0.002), but not in the inner. Even the DCP VD was significantly lower in all the imaged areas: whole (17.75 ± 3.93 mm−1 vs. 19.71 ± 1.20 mm−1; p-value 0.024), outer (18.25 ± 4.17 mm−1 vs. 20.33 ± 1.20 mm−1; p-value 0.023), and inner (19.54 ± 4.17 mm−1 vs. 21.96 ± 1.55 mm−1; p-value 0.011). There were no significant differences in vessel perfusion parameters (both SCP VP and DCP VP ones) and FAZ. No significant correlations were found between the OCTA parameters and systemic parameters (maximal left ventricular wall thickness and glomerular filtration rate) in FD patients.Conclusions: OCTA can be considered as a promising non-invasive tool, which enables a quantitative evaluation of retinal vascular involvement in FD, despite the varying data reported in literature. Our results support the use of OCTA as an objective tool to evaluate retinal vascular abnormalities in FD. The utility of OCTA in FD needs to be validated by longitudinal studies taking into account the overall progression of the disease.

Relative Postpartum Retinal Vasoconstriction Detected With Optical Coherence Tomography Angiography.

PurposeTo characterize changes in retinal perfusion during pregnancy and the postpartum period using optical coherence tomography angiography (OCTA).MethodsA nonmydriatic OCTA camera was used to image healthy women who were pregnant or in the postpartum period along with nonpregnant controls. Perfusion density (PD) and vessel length density (VLD) in the superficial capillary plexus (SCP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP) were evaluated.ResultsA total of 16, 15, and 13 eyes from nonpregnant, pregnant, and healthy postpartum subjects, respectively, were evaluated. When compared to controls, there were significant increases in ICP PD during the second and third trimester of pregnancy, along with significant decreases in both PD and VLD in SCP, ICP, and DCP up to 14 weeks postpartum.ConclusionsDuring pregnancy, vascular changes consistent with retinal vasodilation were noted in the ICP. During the postpartum period, changes in retinal vasculature suggest relative vasoconstriction involving all three layers when compared to both the pregnant and nonpregnant states.Translational RelevanceDetecting postpartum changes in retinal vasculature could offer important insights into postpartum physiology throughout the body.

The Relation between Body Mass Index and Retinal Photoreceptor Morphology and Microvascular Changes Measured with Adaptive Optics (rtx1) High-Resolution Imaging.

Background Overweight and obese patients are at risk for diabetes, cardiovascular disorders, and microvascular complications. The rtx1TM (Imagine Eyes, France) is a microscope that allows near histological visualizations of cones and retinal microcirculation. Objective This study analysed the cones and retinal microvascular changes in a group of 47 healthy women with different BMI values. Participants were divided into 2 groups: the BMI group (28 women with BMI >/25) and the control group (19 lean women with BMI <25). Results The lumen and diameter of retinal arteries were not significantly different between groups. There were significant differences in the thickness of arteriole walls. The WLR and WCSA values differed significantly between the control and BMI groups (for WLR 0.25 ± 0.03 vs. 0.29 ± 0.03, p < 0.001; for WCSA 4136.7 ± 1140.0 vs. 5217.3 ± 944.0, respectively, p < 0.001). In healthy eyes, cone density and morphology were not affected by weight. Conclusions Retinal image analysis with rtx1 offers a novel noninvasive measurement of early changes in retinal vasculature that are not detectable during routine clinical examination. Abnormalities of retinal arterioles found by rtx1™examination should be considered as a strong risk factor for cardiovascular changes resulting from overweight and obesity.

Diabetic vascular hyperpermeability: optical coherence tomography angiography and functional loss assessments of relationships among retinal vasculature changes

Our study assessed the influence of vascular permeability on vascular flow density (FD)-correlated retinal sensitivity (RS) in DR. In this cross-sectional, prospective, consecutive study, RS in the extrafoveal macula of DR patient was measured by microperimetry. FD was measured in the total, superficial, and deep capillary plexus layers (TCP, SCP, and DCP) by optical coherence tomography angiography. All measurement points were classified into four categories according to intensity of fluorescein leakage and FD, and the RS reduction was compared. A stratified analysis by retinal thickness (RT) was also performed. Fourteen eyes (14 patients) were enrolled. FDs at 207 RS measurement points were analyzable. For TCP, SCP and DCP, the leakage did not decrease RS at points where FD was maintained. The greater the leakage, the smaller the RS reduction at points with low FD in TCP (P = .020). Points with high leakage showed a significant smaller RS reduction than points with low leakage (P = .001 for TCP, P = .040 for SCP, and P = .046 for DCP) only in areas with low RT and low FD. Our results suggested that vascular hyperpermeability may inhibit the RS reduction in the non-edematous ischemic diabetic retina.

The structural and comparative analysis of intravitreal dexamethasone implant (Ozurdex) and anti‐VEGF injection in branched retinal vein occlusion patients by optical coherence tomography angiography images quantitation

PurposeTo evaluate and compare the structural changes of retinal vasculature after intravitreal dexamethasone implant (Ozurdex) and anti‐vascular endothelial growth factor (anti‐VEGF) injection in branched retinal vein occlusion (BRVO) patients by optical coherence tomography angiography (OCTA) images quantitation.MethodsWe retrospectively analyzed thirty‐nine patients with unilateral BRVO. Subjects were divided into two groups according to treatment agent, Ozurdex (n = 18) and anti‐VEGF (n = 21). Swept Source (SS) OCT and OCTA were performed, and images were analyzed quantitatively by using ImageJ software. Intravitreal implant and injections were performed following a pro re nata (PRN) regimen. Anti‐VEGF agent was chosen between bevacizumab, ranibizumab and aflibercept.ResultsIn independent two‐sample t‐test, the vessel reperfusion was more significant in intravitreal Ozurdex implant group than anti‐VEGF injection group in choriocapillaris slab of angiography mode (p = 0.013). Positive change of particles number was more prominent in intravitreal anti‐VEGF injection group than intravitreal Ozurdex implant group in outer retina slab of En‐face mode (p = 0.039). ETDRS density map (p = 0.632) and other angiography slabs; superficial (p = 0.200), deep (p = 0.199) and outer retina (p = 0.210) showed no significant difference in two treatment groups.ConclusionsQuantitative analysis of OCTA images using ImageJ software showed that intravitreal Ozurdex implant seems to be better treatment than anti‐VAGF injection for BRVO in the aspect of retinal vascular reperfusion.

Contrast Enhancement of Fundus Images by Employing Modified PSO for Improving the Performance of Deep Learning Models

Computer-Aided diagnosis (CAD) is a widely used technique to detect and diagnose diseases like tumors, cancers, edemas, etc. Several critical retinal diseases like diabetic retinopathy (DR), hypertensive retinopathy (HR), Macular degeneration, retinitis pigmentosa (RP) are mainly analyzed based on the observation of fundus images. The raw fundus images are of inferior quality to represent the minor changes directly. To detect and analyze minor changes in retinal vasculature or to apply advanced disease detection algorithms, the fundus image should be enhanced enough to visibly present vessel touristy. The performance of deep learning models for diagnosing these critical diseases is highly dependent on accurate segmentation of images. Specifically, for retinal vessels segmentation, accurate segmentation of fundus images is highly challenging due to low vessel contrast, varying widths, branching, and the crossing of vessels. For contrast enhancement, various retinal-vessel segmentation methods apply image-contrast enhancement as a pre-processing step, which can introduce noise in an image and affect vessel detection. Recently, numerous studies applied Contrast Limited Adaptive Histogram Equalization (CLAHE) for contrast enhancement, but with the default values for the contextual region and clip limit. In this study, our aim is to improve the performance of both supervised and unsupervised machine learning models for retinal-vessel segmentation by applying modified particle swarm optimization (MPSO) for CLAHE parameter tuning, with a specific focus on optimizing the clip limit and contextual regions. We subsequently assessed the capabilities of the optimized version of CLAHE using standard evaluation metrics. We used the contrast enhanced images achieved using MPSO-based CLAHE for demonstrating its real impact on performance of deep learning model for semantic segmentation of retinal images. The achieved results proved positive impact on sensitivity of supervised machine learning models, which is highly important. By applying the proposed approach on the enhanced retinal images of the publicly available databases of {DRIVE and STARE}, we achieved a sensitivity, specificity and accuracy of {0.8315 and 0.8433}, {0.9750 and 0.9760} and {0.9620 and 0.9645}, respectively.

Retinal Vasculature Changes after Bypass Surgery for Moyamoya Disease

A 48-year-old woman with slurred speech was diagnosed with Moyamoya disease. Digital subtraction angiography disclosed left ophthalmic artery originating from the internal carotid artery (Fig A, arrow), and supplied by orbital branches of the middle meningeal and facial artery (Fig A, arrowhead). Preoperative examinations showed normal superficial vascular complex (SVC) in the left eye (OS) on OCT angiography (Fig B). She underwent left extracranial-intracranial bypass from the superficial temporal artery to the middle cerebral artery.

Abstract 16948: A Comprehensive and High Accurate Pipeline for Mouse Retinal Vasculature Characterization

Rationale: Vascular morphological features reflect the vessel biological functions and analysis of these features is critical for understanding physiological and pathological process of vascular development and vascular diseases. Mouse retinal vasculature is a well-recognized and commonly used animal model for angiogenesis and microvascular remodeling. Thus, a powerful tool to analyze morphological changes of retinal vasculature is in urgent need. Objective: Develop a comprehensive and high accurate pipeline to analyze morphological changes of mouse retinal vasculature. Methods and Results: Retinas from postnatal mice at P2-P7 are harvested and retinal vasculatures are visualized by isolectin B4 whole mount staining. A comprehensive software, Vessel Tech, is developed to perform vessel segmentation, network reconstruction and analysis. Vessel Tech relies on recent advancements in the convolutional neural network and techniques from network data analysis to provide high accuracy vascular identification and comprehensive vascular morphological feature extraction. Compared with existing blood vessel analysis softwares, Vessel Tech shows great improvement in accuracy. Based on the reconstructed vessel network, various metrics of angiogenesis and micro-remodeling are extracted and statistically analyzed. Conclusions: We generated and verified a novel pipeline, named “Vessel Tech”, which could automatically process retinal vascular images, reconstruct vessel network with high accuracy and assay global and local vascular characteristics. The development of Vessel Tech provides a powerful tool to precisely study the physiological and pathological variations during vascular development and vascular diseases.

Effects of high-fat diet and Apoe deficiency on retinal structure and function in mice

To investigate the effects of a high-fat diet (HFD) and apolipoprotein E (Apoe) deficiency on retinal structure and function in mice. Apoe KO mice and wild-type C57BL/6J mice were given a low-fat diet (LFD) or a HFD for 32 weeks. Blood glucose, serum lipids, body weight and visceral fat weight were evaluated. Retinal sterol quantification was carried out by isotope dilution gas chromatography-mass spectrometry. The cholesterol metabolism related genes SCAP-SREBP expressions were detected by qRT-PCR. Retinal function was recorded using an electroretinogram. The thickness of each layer of the retina was measured by optical coherence tomography. Fundus fluorescein angiography was performed to detect retinal vasculature changes. Immunohistochemical staining was used to determine the expression of NF-κB, TNF-α and VEGFR2 in the retina among HFD, HFD Apoe−/−, LFD Apoe−/− and WT mice retinas. HFD feeding caused the mice to gain weight and develop hypercholesterinemia, while Apoe−/− abnormalities also affected blood lipid metabolism. Both HFD and Apoe deficiency elevated retinal cholesterol, especially in the HFD Apoe−/− mice. No up-regulated expression of SCAP-SREBP was observed as a negative regulator. Impaired retinal functions, thinning retinas and abnormal retinal vasculature were observed in the peripheral retinas of the HFD and Apoe−/− mice compared with those in the normal chow group, particularly in the HFD Apoe−/− mice. Moreover, the expression of NF-κB in the retinas of the HFD and Apoe−/− mice was increased, together with upregulated TNF-α mRNA levels and TNF-α expression in the layer of retinal ganglion cells of the peripheral retina. At the same time, the expression level of VEGFR2 was elevated in the intervention groups, most notably in HFD Apoe−/− mice. HFD or Apoe gene deletion had certain adverse effects on retinal function and structure, which were far below the combined factors and induced harm to the retina. Furthermore, HFD caused retinal ischemia and hypoxia. Additionally, Apoe abnormality increased susceptibility to ischemia. These changes upregulated NF-κB expression in ganglion cells and activated downstream TNF-α. Simultaneously, they activated VEGFR2, accelerating angiogenesis and vascular permeability. All of the aforementioned outcomes initiated inflammatory responses to trigger ganglion cell apoptosis and aggravate retinal neovascularization.

Noninvasive temporal detection of early retinal vascular changes during diabetes

Diabetes associated complications, including diabetic retinopathy and loss of vision, are major health concerns. Detecting early retinal vascular changes during diabetes is not well documented, and only few studies have addressed this domain. The purpose of this study was to noninvasively evaluate temporal changes in retinal vasculature at very early stages of diabetes using fundus images from preclinical models of diabetes.Non-diabetic and Akita/+ male mice with different duration of diabetes were subjected to fundus imaging using a Micron III imaging system. The images were obtained from 4 weeks- (onset of diabetes), 8 weeks-, 16 weeks-, and 24 weeks-old male Akita/+ and non-diabetic mice. In total 104 fundus images were subjected to analysis for various feature extractions. A combination of Canny Edge Detector and Angiogenesis Analyzer plug-ins in ImageJ were utilized to quantify various retinal vascular changes in fundus images. Statistical analyses were conducted to determine significant differences in the various extracted features from fundus images of diabetic and non-diabetic animals. Our novel image analysis method led to extraction of over 20 features. These results indicated that some of these features were significantly changed with a short duration of diabetes, and others remained the same but changed after longer duration of diabetes. These patterns likely distinguish acute (protective) and chronic (damaging) associated changes with diabetes. We show that with a combination of various plugging one can extract over 20 features from retinal vasculature fundus images. These features change during diabetes, thus allowing the quantification of quality of retinal vascular architecture as biomarkers for disease progression. In addition, our method was able to identify unique differences among diabetic mice with different duration of diabetes. The ability to noninvasively detect temporal retinal vascular changes during diabetes could lead to identification of specific markers important in the development and progression of diabetes mediated-microvascular changes, evaluation of therapeutic interventions, and eventual reversal of these changes in order to stop or delay disease progression.

Functional and Structural Outcomes at the Foveal Avascular Zone with Optical Coherence Tomography Following Macula off Retinal Detachment Repair.

BackgroundVisual recovery following macula involving rhegmatogenous retinal detachment remains poorly understood. The aim of this work is to correlate the functional and the anatomical changes in retinal vasculature in the foveal avascular zone using optical coherence tomography angiography (OCTA) after successful retinal reattachment repair and correlate this data with retinal thickness and post-operative visual recovery.MethodsA prospective, comparative observational study of 28 eyes of 14 patients with 14 eyes undergoing macula off retinal detachment repair with pars plana vitrectomy, endo-laser and silicone oil-based tamponade compared with 14 fellow healthy eyes at 1, 6 and 12 weeks post-operative period. The study was conducted at the Research Institute of Ophthalmology, Giza, Egypt between February 2018 and August 2018.ResultsThe foveal avascular zone (FAZ) area in the patients group was not significantly different compared to the control group and was found to be negatively correlated with the central retinal thickness in both the study and control group. The superficial capillary plexus (SCP) area at the FAZ was significantly larger than the deep capillary plexus (DCP) area at the FAZ in both the study and control group over the follow-up period. The DCP area at the FAZ was significantly larger at the 3rd follow-up than the 1st follow-up. The SCP FAZ area was significantly larger than the DCP FAZ area in both the study and control group over the follow-up period. BCVA was found to be negatively correlated to the retinal thickness of the temporal 3 mm paracentral quadrant with no correlation with central foveal thickness (CFT) and the FAZ area.ConclusionOptical coherence tomography (OCT) and OCTA are valuable noninvasive imaging tools to monitor and predict the structural changes at the foveal avascular zone during the recovery phase after successful retinal reattachment involving macula.