Hypertensive retinopathy signs as risk indicators of cardiovascular morbidity and mortality

Ocular biomarkers: useful incidental findings by deep learning algorithms in fundus photographs

BACKGROUND/OBJECTIVES

Artificial intelligence can assist with ocular image analysis for screening and diagnosis, but it is not yet capable of autonomous full-spectrum screening. Hypothetically, false-positive results may have unrealized screening potential arising from signals persisting despite training and/or ambiguous signals such as from biomarker overlap or high comorbidity. The study aimed to explore the potential to detect clinically useful incidental ocular biomarkers by screening fundus photographs of hypertensive adults using diabetic deep learning algorithms.

SUBJECTS/METHODS

Patients referred for treatment-resistant hypertension were imaged at a hospital unit in Perth, Australia, between 2016 and 2022. The same 45° colour fundus photograph selected for each of the 433 participants imaged was processed by three deep learning algorithms. Two expert retinal specialists graded all false-positive results for diabetic retinopathy in non-diabetic participants.

RESULTS

Of the 29 non-diabetic participants misclassified as positive for diabetic retinopathy, 28 (97%) had clinically useful retinal biomarkers. The models designed to screen for fewer diseases captured more incidental disease. All three algorithms showed a positive correlation between severity of hypertensive retinopathy and misclassified diabetic retinopathy.

CONCLUSIONS

The results suggest that diabetic deep learning models may be responsive to hypertensive and other clinically useful retinal biomarkers within an at-risk, hypertensive cohort. Observing that models trained for fewer diseases captured more incidental pathology increases confidence in signalling hypotheses aligned with using self-supervised learning to develop autonomous comprehensive screening. Meanwhile, non-referable and false-positive outputs of other deep learning screening models could be explored for immediate clinical use in other populations.

Retinal microcirculation: A window into systemic circulation and metabolic disease

The retinal microcirculation system constitutes a unique terminal vessel bed of the systemic circulation, and its perfusion status is directly associated with the neural function of the retina. This vascular network, essential for nourishing various layers of the retina, comprises two primary microcirculation systems: the retinal microcirculation and the choroidal microcirculation, with each system supplying blood to distinct retinal layers and maintaining the associated neural function. The blood flow of those capillaries is regulated via different mechanisms. However, a range of internal and external factors can disrupt the normal architecture and blood flow within the retinal microcirculation, leading to several retinal pathologies, including diabetic retinopathy, macular edema, and vascular occlusions. Metabolic disturbances such as hyperglycemia, hypertension, and dyslipidemia are known to modify retinal microcirculation through various pathways. These alterations are observable in chronic metabolic conditions like diabetes, coronary artery disease, and cerebral microvascular disease due to advances in non-invasive or minimally invasive retinal imaging techniques. Thus, examination of the retinal microcirculation can provide insights into the progression of numerous chronic metabolic disorders. This review discusses the anatomy, physiology and pathophysiology of the retinal microvascular system, with a particular emphasis on the connections between retinal microcirculation and systemic circulation in both healthy states and in the context of prevalent chronic metabolic diseases.

Retinal Findings and Cardiovascular Risk: Prognostic Conditions, Novel Biomarkers, and Emerging Image Analysis Techniques

Many retinal diseases and imaging findings have pathophysiologic underpinnings in the function of the cardiovascular system. Myriad retinal conditions, new imaging biomarkers, and novel image analysis techniques have been investigated for their association with future cardiovascular risk or utility in cardiovascular risk prognostication. An intensive literature search was performed to identify relevant articles indexed in PubMed, Scopus, and Google Scholar for a targeted narrative review. This review investigates the literature on specific retinal disease states, such as retinal arterial and venous occlusions and cotton wool spots, that portend significantly increased risk of future cardiovascular events, such as stroke or myocardial infarction, and the implications for personalized patient counseling. Furthermore, conditions diagnosed primarily through retinal bioimaging, such as paracentral acute middle maculopathy and the newly discovered entity known as a retinal ischemic perivascular lesion, may be associated with future incident cardiovascular morbidity and are also discussed. As ever-more-sophisticated imaging biomarkers and analysis techniques are developed, the review concludes with a focused analysis of optical coherence tomography and optical coherence tomography angiography biomarkers under investigation for potential value in prognostication and personalized therapy in cardiovascular disease.

Upregulated miR-194-5p suppresses retinal microvascular endothelial cell dysfunction and mitigates the symptoms of hypertensive retinopathy in mice by targeting SOX17 and VEGF signaling

BACKGROUND

Hypertensive retinopathy (HR) is a retinal disease that may lead to vision loss and blindness. Sex-determining region Y (SRY)-box (SOX) family transcription factors have been reported to be involved in HR development. In this study, the role and upstream mechanism of SRY-box transcription factor 17 (SOX17) in HR pathogenesis were investigated.

METHODS

SOX17 and miR-194-5p levels in Angiotensin II (Ang II)-stimulated human retinal microvascular endothelial cells (HRMECs) and retinas of mice were detected by RT-qPCR. SOX17 protein level as well as levels of tight junction proteins and vascular endothelial growth factor (VEGF) signaling-associated proteins were quantified by western blotting. Tube formation assays were performed to evaluate angiogenesis in HRMECs. The structure of mouse retinal tissues was observed by H&E staining. The interaction between miR-194-5p and SOX17 was confirmed by a luciferase reporter assay.

RESULTS

SOX17 was upregulated in HRMECs treated with Ang II. SOX17 knockdown inhibited angiogenesis in Ang II-stimulated HRMECs and increased tight junction protein levels. Mechanically, SOX17 was targeted by miR-194-5p. Moreover, miR-194-5p upregulation restrained angiogenesis and increased tight junction protein levels in Ang II-treated HRMECs, and the effect was reversed by SOX17 overexpression. MiR-194-5p elevation inactivated VEGF signaling via targeting SOX17. miR-194-5p alleviated pathological symptoms of HR in Ang II-treated mice, and its expression was negatively correlated with SOX17 expression in the retinas of model mice.

CONCLUSIONS

MiR-194-5p upregulation suppressed Ang II-stimulated HRMEC dysfunction and mitigates the symptoms of HR in mice by regulating the SOX17/VEGF signaling.

Segmentation of retinal vessels based on MRANet

The segmentation of retinal vessel takes a crucial part in computer-aided diagnosis of diseases and eye disorders. However, the insufficient segmentation of the capillary vessels and weak anti-noise interference ability make such task more difficult. To solve this problem, we proposed a multi-scale residual attention network (MRANet) which is based on U-Net network. Firstly, to collect useful information about the blood vessels more effectively, we proposed a multi-level feature fusion block (MLF block). Then, different weights of each fused feature are learned by using attention blocks, which can retain more useful feature information while reducing the interference of redundant features. Thirdly, multi-scale residual connection block (MSR block) is constructed, which can better extract the image features. Finally, we use the DropBlock layer in the network to reduce the network parameters and alleviate network overfitting. Experiments show that based on DRIVE, the accuracy rate and the AUC performance value of our network are 0.9698 and 0.9899 respectively, and based on CHASE_DB1 dataset, they are 0.9755 and 0.9893 respectively. Our network has a better segmentation effect compared with other methods, which can ensure the continuity and completeness of blood vessel segmentation.

Hypertensive Retinopathy and All-Cause Mortality in Older Adults of Amerindian Ancestry. A Population-based Longitudinal Prospective Study

Introduction

Hypertensive retinopathy (HTRP) predicts all-cause mortality in Asian and Caucasian populations. However, little is known about HTRP impact in other ethnic groups.

Aim

We sought to estimate the mortality risk according to HTRP severity in older adults of Amerindian ancestry living in rural Ecuador.

Methods

This prospective study enrolled individuals aged ≥ 60 years with baseline blood pressure ≥ 120/≥ 80 mmHg from the ongoing Atahualpa Project cohort who received retinal photographs (for HTRP grading) and a brain MRI. We ascertained all-cause mortality after a mean of 5.2 ± 1.2 years of follow-up. Cox-proportional hazards models adjusted for demographics, cardiovascular risk factors, neuroimaging signatures of cerebral small vessel disease, blood pressure determinations during follow-up and incident strokes, were obtained to estimate mortality risk according to HTRP severity.

Results

Analysis included 236 participants (mean age 69.3 ± 7.3 years). HTRP Grade 2 or higher was determined in 42 (18%) individuals. Fifty participants (21%) died during the follow-up, resulting in an overall unadjusted crude mortality rate of 4.1 per 100 person-years. Mortality rate in subjects with HTRP Grade 2 or higher was 7.2 and in those with no HTRP or Grade 1 only was 3.4 per 100 person-years. An adjusted Cox-proportional hazard model showed that individuals with HTRP Grade 2 or higher maintained a greater than two-fold mortality risk (HR 2.08; 95% C.I. 1.04–4.15; p = 0.038) when compared to those with no HTRP or Grade 1 only.

Conclusion

Study results show that HTRP severity predicts mortality in this population of older adults.

[Ophthalmological manifestations of post-COVID-19 syndrome]

The review presents data on damage to the organ of vision in patients recovered from the new coronavirus infection reflecting on the results obtained by various researchers from examining patients with varying severity of the disease, both during the active stage and after recovery. Possible ways of transmission of the infectious agent into the organ of vision were analyzed. The most common ocular manifestation of COVID-19 is conjunctivitis, while lesions of the retina and optic nerve were noted less often. The article also outlines the strategy for treatment and describes infection prevention measures for doctors and patients.

Role of pattern electroretinogram in assessment of retinal dysfunction in hypertensive patients

BACKGROUND

Hypertension is a major health problem in both developing and developed countries. Hypertension causes retinal structural and functional impairment within the ganglion cell layer. Pattern electroretinogram (PERG) offers an objective simple tool for assessment of retinal ganglion cell function.Aim of the work: To assess retinal dysfunction in hypertensive patients with or without signs of retinopathy using PERG.

MATERIALS AND METHODS

This is a case control study, including ninety-eight eyes. Twenty-eight eyes of healthy subjects served as a control group (group I) and seventy eyes of patients with systemic hypertension, who were further subdivided into group II including 39 eyes of hypertensive patients with normal fundus and group III including 31 eyes of patients with signs of hypertensive retinopathy. All subjects were subjected to ophthalmological examination and electrophysiological assessment using PERG.

RESULTS

PERG implicit times were significantly prolonged and amplitudes were significantly reduced in patients with established hypertensive retinopathy. PERG abnormalities were detected in 96.8% of hypertensive retinopathy patients and 79.5% of hypertensive patients with normal fundus.

CONCLUSIONS

PERG can objectively assess retinal dysfunction in hypertensive patients and may be considered a promising tool for early detection of hypertensive retinopathy.

Hypertensive Retinopathy and the Risk of Stroke Among Hypertensive Adults in China

Purpose

This study aimed to investigate the association between hypertensive retinopathy and the risk of first stroke, examine possible effect modifiers in hypertensive patients, and test the appropriateness of the Keith-Wagener-Barker (KWB) classification for predicting stroke risk.

Methods

In total, 9793 hypertensive participants (3727 males and 6066 females) without stroke history from the China Stroke Primary Prevention Trial were included in this study. The primary outcome was first stroke.

Results

Over a median follow-up of 4.4 years, 592 participants experienced their first stroke (509 ischemic, 77 hemorrhagic, and six unclassifiable strokes). In total, 5590 participants were diagnosed with grade 1 retinopathy (57.08%), 1466 with grade 2 retinopathy (14.97%), 231 with grade 3 retinopathy (2.36%), and three with grade 4 retinopathy (0.03%). Grades 1 and 2 were merged and classified as mild retinopathy, and grades 3 and 4 were merged and classified as severe retinopathy. There was a significant positive association between hypertensive retinopathy and the risk of first stroke and first ischemic stroke, and no effect modifiers were found. The hazard ratios (HRs) for first stroke were as follows: mild versus no retinopathy, 1.26 (95% confidence interval [CI], 1.01-1.58, P = 0.040), and severe versus no retinopathy, 2.40 (95% CI, 1.49-3.84, P < 0.001). The HRs for ischemic stroke were as follows: severe versus no retinopathy, 2.35 (95% CI, 1.41-3.90, P = 0.001), and nonsignificantly increased HRs for mild versus no retinopathy, 1.26 (95% CI, 0.99-1.60, P = 0.057).

Conclusions

There was a significant positive association between hypertensive retinopathy and the risk of first stroke in patients with hypertension, indicating that hypertensive retinopathy may be a predictor of the risk of stroke. A simplified two-grade classification system based on the KWB classification is recommended for predicting stroke risk.

Retinal vascular findings in patients with COVID-19

Purpose:

The purpose of this study was to compare the retinal vascular caliber of COVID-19 patients with that of healthy subjects.

Methods:

This was a prospective case–control study. Forty-six patients who had COVID-19 were successfully treated, and 38 age- and gender-matched healthy subjects were enrolled in this study. Fundus photography was taken using fundus fluorescein angiography (FA; Visucam 500; Carl Zeiss Meditec, Jena, Germany). Retinal vascular caliber was analyzed with IVAN, a semi-automated retinal vascular analyzer (Nicole J. Ferrier, College of Engineering, Fundus Photography Reading Center, University of Wisconsin, Madison, WI, USA). Central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and artery–vein ratio (AVR) were compared between groups.

Results:

The mean age was 37.8 ± 9.5 years in the COVID-19 group (n = 46) and 40 ± 8 years in the control group (n = 38) (p = 0.45). The mean CRAE was 181.56 ± 6.40 in the COVID-19 group and 171.29 ± 15.06 in the control group (p = 0.006). The mean CRVE was 226.34 ± 23.83 in the COVID-19 group and 210.94 ± 22.22 in the control group (p = 0.044). AVR was 0.81 ± 0.09 in the COVID-19 group and 0.82 ± 0.13 in the control group (p = 0.712).

Conclusion:

Patients who had COVID-19 have vasodilation in the retinal vascular structure after recovery. As they may be at risk of retinal vascular disease, COVID-19 patients must be followed after recovery.

Retinal Vascular Signs and Cerebrovascular Diseases

BACKGROUND

Cerebrovascular disease (CeVD), including stroke, is a leading cause of death globally. The retina is an extension of the cerebrum, sharing embryological and vascular pathways. The association between different retinal signs and CeVD has been extensively evaluated. In this review, we summarize recent studies which have examined this association.

EVIDENCE ACQUISITION

We searched 6 databases through July 2019 for studies evaluating the link between retinal vascular signs and diseases with CeVD. CeVD was classified into 2 groups: clinical CeVD (including clinical stroke, silent cerebral infarction, cerebral hemorrhage, and stroke mortality), and sub-clinical CeVD (including MRI-defined lacunar infarct and white matter lesions [WMLs]). Retinal vascular signs were classified into 3 groups: classic hypertensive retinopathy (including retinal microaneurysms, retinal microhemorrhage, focal/generalized arteriolar narrowing, cotton-wool spots, and arteriovenous nicking), clinical retinal diseases (including diabetic retinopathy [DR], age-related macular degeneration [AMD], retinal vein occlusion, retinal artery occlusion [RAO], and retinal emboli), and retinal vascular imaging measures (including retinal vessel diameter and geometry). We also examined emerging retinal vascular imaging measures and the use of artificial intelligence (AI) deep learning (DL) techniques.

RESULTS

Hypertensive retinopathy signs were consistently associated with clinical CeVD and subclinical CeVD subtypes including subclinical cerebral large artery infarction, lacunar infarction, and WMLs. Some clinical retinal diseases such as DR, retinal arterial and venous occlusion, and transient monocular vision loss are consistently associated with clinical CeVD. There is an increased risk of recurrent stroke immediately after RAO. Less consistent associations are seen with AMD. Retinal vascular imaging using computer assisted, semi-automated software to measure retinal vascular caliber and other parameters (tortuosity, fractal dimension, and branching angle) has shown strong associations to clinical and subclinical CeVD. Other new retinal vascular imaging techniques (dynamic retinal vessel analysis, adaptive optics, and optical coherence tomography angiography) are emerging technologies in this field. Application of AI-DL is expected to detect subclinical retinal changes and discrete retinal features in predicting systemic conditions including CeVD.

CONCLUSIONS

There is extensive and increasing evidence that a range of retinal vascular signs and disease are closely linked to CeVD, including subclinical and clinical CeVD. New technology including AI-DL will allow further translation to clinical utilization.

A Global and Local Enhanced Residual U-Net for Accurate Retinal Vessel Segmentation

Retinal vessel segmentation is a critical procedure towards the accurate visualization, diagnosis, early treatment, and surgery planning of ocular diseases. Recent deep learning-based approaches have achieved impressive performance in retinal vessel segmentation. However, they usually apply global image pre-processing and take the whole retinal images as input during network training, which have two drawbacks for accurate retinal vessel segmentation. First, these methods lack the utilization of the local patch information. Second, they overlook the geometric constraint that retina only occurs in a specific area within the whole image or the extracted patch. As a consequence, these global-based methods suffer in handling details, such as recognizing the small thin vessels, discriminating the optic disk, etc. To address these drawbacks, this study proposes a Global and Local enhanced residual U-nEt (GLUE) for accurate retinal vessel segmentation, which benefits from both the globally and locally enhanced information inside the retinal region. Experimental results on two benchmark datasets demonstrate the effectiveness of the proposed method, which consistently improves the segmentation accuracy over a conventional U-Net and achieves competitive performance compared to the state-of-the-art.

Could aortic arch calcification help in detection of hypertensive retinopathy?

OBJECTIVE

Hypertension-induced end-organ damage is one of the important determinants of morbidity and mortality in patients with hypertension. All types of hypertension-induced end-organ damages start with vascular damage. Vascular calcification is a marker of vascular damage and aortic arch calcification (AAC) is one of the easily identifiable types of vascular calcification. We hypothesized that AAC predicts retinopathy in hypertensive patients.

METHODS

Consecutive hypertensive patients without diabetes mellitus were included. Chest radiography in the posterior-anterior was used to assess the presence of AAC. All patients underwent ophthalmologic examination for retinopathy.

RESULTS

We included 495 hypertensive patients in this study. Of these, 306 (62%) had hypertensive retinopathy. Patients with hypertensive retinopathy had significantly higher prevalence of AAC as compared to the patients without hypertensive retinopathy (88% vs. 22%, P < 0.001). We found a strong and positive correlation between hypertensive retinopathy and AAC grades (r = 639, P < 0.001). Receiver operator characteristics curve analysis yielded a strong predictive ability of AAC for the presence of hypertensive retinopathy [area under curve = 0.814, 95% confidence interval (CI): 0.775-0.853, P < 0.0001]. In multivariate logistic regression analysis, presence of AAC [odds ratio (OR) 13.128; CI: 7.894-21.832] and serum glucose levels (OR 1.020; CI: 1.003-1.037) were strongly and independently associated with hypertensive retinopathy.

CONCLUSION

Presence of AAC on chest radiograph is strongly and independently associated with retinopathy in nondiabetic hypertensive patients. This simple, inexpensive and widely available tool may help in early detection of retinopathy in patients with hypertension.

Dysregulation of miR-637 Is Involved in the Development of Retinopathy in Hypertension Patients and Serves a Regulatory Role in Retinol Endothelial Cell Proliferation

BACKGROUND

MicroRNAs play an important role in the proliferation and migration of retinal endothelial cells in patients with hypertension and hypertensive retinopathy (HR). This study aimed to investigate the clinical value of miR-637 in HR and its role in retinal endothelial cell proliferation and migration.

METHODS

A total of 126 subjects were recruited for the study, including 42 patients with hypertension (male/female 25/17), 42 healthy individuals (male/female 20/22), and 42 cases with HR (male/female 20/22). Except SBP and DBP, there was no significant difference in other indexes among the three groups. Quantitative real-time PCR was used to detect the expression of miR-637. The receiver operating curve (ROC) was used for diagnosis value analysis. Logistic regression analysis was used to evaluate the relationship between miR-637 and HR. CCK-8 and Transwell were used to detect the effect of miR-637 on the proliferation and migration of human umbilical vein endothelial cells.

RESULTS

Compared with hypertensive patients, HR patients had the lowest expression of miR-637. The area under the curve of miR-637 detected by the ROC curve method is 0.892, which has the ability to distinguish hypertension and HR patients. Logistic regression analysis showed that miR-637 was an independent influencing factor in HR. Cell experiment results showed that overexpression of miR-637 significantly inhibited cell proliferation and migration, while downregulation of miR-637 had the opposite effect. Luciferase analysis showed that STAT3 was the target gene of miR-637.

CONCLUSION

Our data indicate that miR-637 is a potential noninvasive marker for patients with HR. The action of miR-637 on STAT3 may inhibit the proliferation and migration of retinal endothelial cells, providing a possible target for the treatment of HR.

Unsupervised sorting of retinal vessels using locally consistent Gaussian mixtures

BACKGROUND AND OBJECTIVES

Retinal blood vessels classification into arterioles and venules is a major task for biomarker identification. Especially, clustering of retinal blood vessels is a challenging task due to factors affecting the images such as contrast variability, non-uniform illumination etc. Hence, a high performance automatic retinal vessel classification system is highly prized. In this paper, we propose a novel unsupervised methodology to classify retinal vessels extracted from fundus camera images into arterioles and venules.

METHODS

The proposed method utilises the homomorphic filtering (HF) to preprocess the input image for non-uniform illumination and denoising. In the next step, an unsupervised multiscale line operator segmentation technique is used to segment the retinal vasculature before extracting the discriminating features. Finally, the Locally Consistent Gaussian Mixture Model (LCGMM) is utilised for unsupervised sorting of retinal vessels.

RESULTS

The performance of the proposed unsupervised method was assessed using three publicly accessible databases: INSPIRE-AVR, VICAVR, and MESSIDOR. The proposed framework achieved 90.14%,90.3% and 93.8% classification rate in zone B for the three datasets respectively.

CONCLUSIONS

The proposed clustering framework provided high classification rate as compared to conventional Gaussian mixture model using Expectation-Maximisation (GMM-EM) approach, thus have a great capability to enhance computer assisted diagnosis and research in field of biomarker discovery.

An effective technique for diabetic retinopathy using hybrid machine learning technique

Diabetic retinopathy (DR) stays as an eye issue that has continuously developed in individuals who experienced diabetes. The complexities in diabetes cause harm to the vein at the back of the retina. In outrageous cases, DR could swift apparition disaster or visual impairment. This genuine impact had the option to charge through convenient treatment and early recognition. As of late, this issue has been spreading quickly, particularly in the working region, which in the end constrained the interest of an analysis of this disease from the most prompt stage. Therefore, that are castoff to protect the progressions of this disorder, revealing of the retinal blood vessels (RBVs) play a foremost role. The growth of an abnormal vessel leads to the development steps of DR, where it can be well known by extracting the RBV. The recognition of the BV for DR by developing an automatic approach is a major aim of our research study. In the proposed method, there are two major steps: one is segmentation and the second one is classification of affected retinal BV. The proposed method uses the Kinetic Gas Molecule Optimization based on centroid initialization used for the Fuzzy C-means Clustering. In the classification step, those segmented images are given as input to hybrid techniques such as a convolution neural network with bidirectional-long short-term memory (CNN with Bi-LSTM). The learning degree of Bi-LSTM is revised by using the self-attention mechanism for refining the classification accuracy. The trial consequences disclosed that the mixture algorithm achieved higher accuracy, specificity, and sensitivity than existing techniques.

Six-year incidence and systemic associations of retinopathy in a multi-ethnic Asian population without diabetes

PURPOSE

We described the 6-year incidence and changes of retinopathy, and their associated risk factors in a multi-ethnic Asian population without diabetes.

METHODS

We included 4374 participants with non-diabetes from a population-based cohort, the Singapore Epidemiology of Eye Disease Study, with gradable retinal photographs at baseline and 6-year follow-up visit. Retinopathy was assessed according to the modified Airlie House classification system.

RESULTS

Over the 6-year period, the cumulative rates were 2.5% (106/4279) for retinopathy incidence, 1.0% (1/95) for retinopathy progression and 68.4% (65/95) for retinopathy regression. In multivariable analysis, higher diastolic blood pressure (DBP) (risk ratio (RR)=1.02; 95% CI: 1.00 to 1.04; per 10 mm Hg increase in DBP) and wider retinal arteriolar calibre (RR=1.36; 95% CI: 1.13 to 1.63; per SD increase in central retinal artery equivalent) were associated with higher risk of incident retinopathy, while higher level of high-density lipoprotein (HDL) was associated with lower risk of incident retinopathy (RR=0.56; 95% CI: 0.32 to 0.99; per mmol/L increase in HDL). Compared with Chinese, Malays were more likely to have retinopathy regression (RR=1.63; 95% CI: 1.20 to 2.22), while overweight (RR=0.47; 95% CI: 0.26 to 0.84) and higher glycosylated haemoglobin (HbA1c) level (RR=0.58; 95% CI: 0.37 to 0.93; per per cent increase in HbA1c) were associated with lower likelihood of retinopathy regression.

CONCLUSION

Risk of developing retinopathy in Asians without diabetes is generally low. However, regression of retinopathy over time is common, suggesting that these retinopathy signs may reflect subclinical reversible microvascular dysfunction. Several metabolic risk factors are associated with incidence or regression of retinopathy, suggesting that good metabolic control may still be important in the management of non-diabetic retinopathy.

Retinal vascular tortuosity: Mechanisms and measurements

Retinal vessel tortuosity has been used in the diagnosis and management of different clinical situations. Notwithstanding, basic concepts, standards and tools of measurement, reliable normative data and clinical applications have many gaps or points of divergence. In this review we discuss triggering causes of retinal vessel tortuosity and resources used to assess and quantify it, as well as current limitations.

Retinal findings in patients with COVID-19: Results from the SERPICO-19 study

BACKGROUND

Coronavirus disease 2019 (COVID-19) has been associated to microvascular alterations. We screened the fundus of patients with COVID-19 to detect alterations of the retina and its vasculature and to assess possible correlations with clinical parameters.

METHODS

Cross-sectional study. The presence of retinal alterations in patients with COVID-19 and subjects unexposed to the virus was assessed using fundus photographs and their prevalence was compared. Mean arteries diameter (MAD) and mean veins diameter (MVD) were compared between patients and unexposed subjects with multiple linear regression including age, sex, ethnicity, body mass index, smoking/alcohol consumption, hypertension, hyperlipidaemia, diabetes as covariates. The influence of clinical/lab parameters on retinal findings was tested in COVID-19 patients.

FINDINGS

54 patients and 133 unexposed subjects were enrolled. Retinal findings in COVID-19 included: haemorrhages (9·25%), cotton wools spots (7·4%), dilated veins (27·7%), tortuous vessels (12·9%). Both MAD and MVD were higher in COVID-19 patients compared to unexposed subjects (98·3 ± 15·3 µm vs 91·9 ± 11·7 µm, p = 0.006 and 138·5 ± 21·5 µm vs 123·2 ± 13·0 µm, p<0.0001, respectively). In multiple regression accounting for covariates MVD was positively associated with COVID-19 both in severe (coefficient 30·3, CI95% 18·1-42·4) and non-severe (coefficient 10·3, CI95% 1·6-19·0) cases compared to unexposed subjects. In COVID-19 patients MVD was negatively correlated with the time from symptoms onset (coefficient -1·0, CI 95% -1·89 to -0·20) and positively correlated with disease severity (coefficient 22·0, CI 95% 5·2-38·9).

INTERPRETATION

COVID-19 can affect the retina. Retinal veins diameter seems directly correlated with the disease severity. Its assessment could have possible applications in the management of COVID-19.

FUNDING

None.

Genetic Deep Convolutional Autoencoder Applied for Generative Continuous Arterial Blood Pressure via Photoplethysmography

Hypertension affects a huge number of people around the world. It also has a great contribution to cardiovascular- and renal-related diseases. This study investigates the ability of a deep convolutional autoencoder (DCAE) to generate continuous arterial blood pressure (ABP) by only utilizing photoplethysmography (PPG). A total of 18 patients are utilized. LeNet-5- and U-Net-based DCAEs, respectively abbreviated LDCAE and UDCAE, are compared to the MP60 IntelliVue Patient Monitor, as the gold standard. Moreover, in order to investigate the data generalization, the cross-validation (CV) method is conducted. The results show that the UDCAE provides superior results in producing the systolic blood pressure (SBP) estimation. Meanwhile, the LDCAE gives a slightly better result for the diastolic blood pressure (DBP) prediction. Finally, the genetic algorithm-based optimization deep convolutional autoencoder (GDCAE) is further administered to optimize the ensemble of the CV models. The results reveal that the GDCAE is superior to either the LDCAE or UDCAE. In conclusion, this study exhibits that systolic blood pressure (SBP) and diastolic blood pressure (DBP) can also be accurately achieved by only utilizing a single PPG signal.

Investigating the Role of PPARβ/δ in Retinal Vascular Remodeling Using Pparβ/δ-Deficient Mice

Peroxisome proliferator-activated receptor (PPAR)β/δ is a member of the nuclear receptor superfamily of transcription factors, which plays fundamental roles in cell proliferation and differentiation, inflammation, adipogenesis, and energy homeostasis. Previous studies demonstrated a reduced choroidal neovascularization (CNV) in Pparβ/δ-deficient mice. However, PPARβ/δ's role in physiological blood vessel formation and vessel remodeling in the retina has yet to be established. Our study showed that PPARβ/δ is specifically required for disordered blood vessel formation in the retina. We further demonstrated an increased arteriovenous crossover and wider venous caliber in Pparβ/δ-haplodeficient mice. In summary, these results indicated a critical role of PPARβ/δ in pathological angiogenesis and blood vessel remodeling in the retina.

Systemic hypertension associated retinal microvascular changes can be detected with optical coherence tomography angiography

A major complication of hypertension is microvascular damage and capillary rarefaction is a known complication of hypertensive end-organ damage which confers a higher risk of systemic disease such as stroke and cardiovascular events. Our aim was to study the effect of hypertension on the retinal microvasculature using non-invasive optical coherence tomography angiography (OCTA). We performed a case-control study of 94 eyes of 94 participants with systemic hypertension and 46 normal control eyes from the Singapore Chinese Eye Study using a standardized protocol to collect data on past medical history of hypertension, including the number and type of hypertensive medications and assessed mean arterial pressure. Retinal vascular parameters were measured in all eyes using OCTA. In the multivariate analysis adjusting for confounders, compared to controls, eyes of hypertensive patients showed a decrease in the macular vessel density at the level of the superficial [OR 0.02; 95% CI, 0 to 0.64; P 0.027] and deep venous plexuses [OR 0.03; 95% CI, 0 to 0.41; P 0.009] and an increase in the deep foveal avascular zone. This shows that hypertension is associated with reduced retinal vessel density and an increased foveal avascular zone, especially in the deep venous plexus, as seen on OCTA and there is a potential role in using OCTA as a clinical tool to monitor hypertensive damage and identifying at risk patients

Role of multifocal electroretinogram in assessment of early retinal dysfunction in hypertensive patients

PURPOSE

To investigate localized retinal dysfunction in hypertensive patients using multifocal electroretinogram (mfERG) and to assess its sensitivity as an early predictor for the development of retinopathy in hypertensive patients.

METHODS

Ninety-eight eyes were included in this case-control study. Twenty-eight eyes of healthy subjects served as a control group (group I). Seventy eyes belonged to patients with systemic hypertension assigned into two groups; group II including 39 eyes of hypertensive patients with normal fundus and group III including 31 eyes of patients with signs of hypertensive retinopathy. All participants were subjected to complete ophthalmic and electrophysiological examination using mfERG. N1 and P1 wave amplitudes and implicit times from the central hexagon and four concentric rings across the visual field were analyzed.

RESULTS

mfERG amplitudes were significantly reduced in hypertensive group with retinopathy than in controls. N1 amplitude was significantly reduced in the most eccentric ring in eyes of hypertensive patients with normal fundus.

CONCLUSION

mfERG is a sensitive objective tool for assessment of retinal dysfunction in hypertensive patients. mfERG amplitude is a promising predictor for early development of retinopathy in systemic hypertension.

Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping

The retinal volumetric flow rate contains useful information not only for ophthalmology but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood flow rate in real-time by the implementation of the algorithms in a graphics processing unit (GPU). The additive character of the flow at the furcations is proven using a microfluidic device with controlled flow rates as well as in the retinal veins bifurcations imaged in the optic disc area of five healthy volunteers. We show values of blood flow rates calculated for retinal capillaries and vessels with diameters in the range of 12-150 µm. The potential of quantitative measurement of retinal blood flow volume includes noninvasive detection of carotid artery stenosis or occlusion, measuring vascular reactivity and evaluation of vessel wall stiffness.

Prevalence and risk profile of retinopathy in non-diabetic subjects: National Health and Nutrition Examination Survey 2005 to 2008

IMPORTANCE

Recent US national population-based data on the prevalence of retinopathy in non-diabetic participants is limited.

BACKGROUND

To assess the prevalence and risk factors of retinopathy in a representative US population without diabetes.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

A total of 4354 non-diabetic participants 40 years and older with valid fundus photographs in the 2005 to 2008 National Health and Nutrition Examination Survey.

METHODS

Diabetes mellitus was defined as glycosylated haemoglobin (HbA1c) ≥6.5%, physician diagnosis of diabetes mellitus or use of diabetic medication. Retinopathy level was based on the Modified Airlie House adaptation from the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. Risk profile was assessed from standardized interviews, clinical examinations and laboratory measurements.

MAIN OUTCOME MEASURES

Prevalence and risk profile of retinopathy in non-diabetic participants.

RESULTS

The overall weighted prevalence of retinopathy was 6.7% (n = 341). Among them, 98.2% (n = 331) had signs of minimal-to-mild non-proliferative retinopathy (ETDRS level 14-31) while only 1.8% (n = 10) had moderate-to-severe non-proliferative retinopathy (ETDRS level 41-51). After adjusting for multiple covariates, retinopathy signs in non-diabetic participants were associated with male gender (odds ratio [OR] 1.54; 95% confidence interval [CI] 1.22-1.93), systolic blood pressure (OR per 10 mmHg increase 1.11; 95% CI 1.03-1.19), HbA1c (OR per % increase 1.43; 95% CI 1.01-2.05) and history of stroke (OR 2.39; 95% CI 1.14-5.04).

CONCLUSIONS AND RELEVANCE

Consistent with previous studies, signs of retinopathy are common in US persons without diabetes. Risk factors for retinopathy signs include gender, blood pressure, HbA1c and history of stroke.

Selective inhibition of histone deacetylase 8 improves vascular hypertrophy, relaxation, and inflammation in angiotensin II hypertensive mice

Background

The dysregulation of histone deacetylase (HDAC) protein expression or its enzyme activity is implicated in a variety of diseases. Cardiac HDAC6 and HDAC8 enzyme activity induced by deoxycorticosterone acetate (DOCA) hypertension was attenuated by sodium valproate, a pan-HDAC inhibitor. However, the HDAC6-selective inhibitor, tubastatin A, did not attenuate angiotensin II-induced hypertension. The purpose of this study was to investigate whether PCI34051, an HDAC8-selective inhibitor, can modulate angiotensin II-induced hypertension and its regulatory mechanism.

Methods

An angiotensin II-regulated mouse model was used in this study. Animals received vehicle or PCI34051 (3 mg·kg - ¹·day- ¹) via intraperitoneal injection. Systolic blood pressure was measured by the tail-cuff method. Blood vessel thickness was measured following hematoxylin and eosin staining, VCAM-1 immunohistochemistry was performed in the aortas, and mRNA expression of renin-angiotensin system components, inflammation markers, and NADPH oxidase (Nox) was determined by RT-PCR. The effect of PCI34051 on vasorelaxation was studied in rat aortic rings, and its effect on nitric oxide (NO) production was determined using DAF-FM DA, a fluorescent dye, in human umbilical vascular endothelial cells (HUVECs).

Results

PCI34051 administration reduced systolic blood pressure via downregulation of angiotensin II receptor type 1 (AT1) mRNA expression. PCI34051 treatment attenuated vascular hypertrophy by decreasing E2F3 and GATA6 mRNA expression. Vascular relaxation after PCI34051 treatment was more dependent on vascular endothelial cells and it was blocked by an NO synthase (NOS) inhibitor. In addition, NO production increased in HUVECs after PCI34051 treatment; this was decreased by the NOS inhibitor. The expression of inflammatory molecules and adhesion molecules VCAM-1 and ICAM-1 decreased in the aortas of angiotensin II-infused mice after PCI34051 administration. However, PCI34051 did not affect Nox or its regulatory subunits.

Conclusions

PCI34051 lowered high blood pressure through modulation of arterial remodeling, vasoconstriction, and inflammation in an angiotensin II-induced hypertension model. We suggest that HDAC8 could be a potential therapeutic target for hypertension.

Eye Drop Instillation of the Rac1 Modulator CNF1 Attenuates Retinal Gliosis and Ameliorates Visual Performance in a Rat Model of Hypertensive Retinopathy

In hypertensive retinopathy, the retinal damage due to high blood pressure is accompanied by increased expression of Glial Fibrillary Acidic Protein (GFAP), which indicates a role of neuroinflammatory processes in such a retinopathy. Proteins belonging to the Rho GTPase family, particularly Rac1, are involved in the activation of Müller glia and in the progression of photoreceptor degeneration, and may thus represent a novel candidate for therapeutic intervention following central nervous system inflammation. In this paper, we have observed that topical administration as eye drops of Cytotoxic Necrotizing Factor 1 (CNF1), a Rho GTPase modulator, surprisingly improves electrophysiological and behavioral visual performances in aged spontaneously hypertensive rats. Furthermore, such functional improvement is accompanied by a reduction of Rac1 activity and retinal GFAP expression. Our results suggest that Rac1 inhibition through CNF1 topical administration may represent a new strategy to target retinal gliosis.

Hypertensive retinopathy and associated factors among nondiabetic chronic kidney disease patients seen at a tertiary hospital in Tanzania: a cross-sectional study

Background: Hypertensive retinopathy is a known marker of cardiovascular disease, and among unselected patients with chronic kidney disease (CKD) more severe retinopathy has been associated with lower estimated glomerular filtration rate (eGFR). This association has, however, not been widely studied among nondiabetic hypertensive patients with CKD, especially in sub-Saharan Africa. We aimed to determine the prevalence and severity of hypertensive retinopathy and its relationship with eGFR among nondiabetic CKD patients seen at Muhimbili National Hospital in Dar es Salaam, Tanzania. Methods: A hospital-based cross-sectional study was conducted among nondiabetic CKD adult (≥18 years) patients with hypertension. A structured questionnaire was used to record patients' demographic characteristics and their cardiovascular risk profile. eGFR was calculated using the Modification of Diet in the Renal Disease (MDRD) equation and only patients with CKD stage 3 or more were enrolled in the study. Grading of retinopathy was done using the Keith-Wagener classification. Results: In total, 224 patients fulfilled the inclusion criteria and were enrolled. Their mean age was 45.8±14.1 years, and 59.4% were men. The proportions of patients with stage 3, 4, and 5 CKD were 21.4%, 19.6%, and 58.9%, respectively. Hypertensive retinopathy was present in 157 (70.1%) patients and the proportions with grade I, grade II, grade III, and grade IV retinopathy were 17.9%, 18.8%, 19.6%, and 13.8%, respectively. The severity of retinopathy increased with decreasing levels of eGFR, and in multivariate logistic regression analysis, factors found to be independently associated with ≥grade II hypertensive retinopathy were more severe CKD, higher hypertension grades, and alcohol use, all p<0.05. Conclusion: The prevalence of hypertensive retinopathy is high among nondiabetic CKD patients seen at a tertiary hospital in Tanzania and is independently associated with CKD severity. Retinopathy grade can be used as a marker of CKD severity among these patients.

Vascular Interstitial Cells in Retinal Arteriolar Annuli Are Altered During Hypertension

Purpose

It has been suggested that arteriolar annuli localized in retinal arterioles regulate retinal blood flow acting as sphincters. Here, the morphology and protein expression profile of arteriolar annuli have been analyzed under physiologic conditions in the retina of wild-type, β-actin-Egfp, and Nestin-gfp transgenic mice. Additionally, to study the effect of hypertension, the KAP transgenic mouse has been used.

Methods

Cellular architecture has been studied using digested whole mount retinas and transmission electron microscopy. The profile of protein expression has been analyzed on paraffin sections and whole mount retinas by immunofluorescence and histochemistry.

Results

The ultrastructural analysis of arteriolar annuli showed a different cell population found between endothelial and muscle cells that matched most of the morphologic criteria established to define interstitial Cajal cells. The profile of protein expression of these vascular interstitial cells (VICs) was similar to that of interstitial Cajal cells and different from the endothelial and smooth muscle cells, because they expressed β-actin, nestin, and CD44, but they did not express CD31 and α-SMA or scarcely express F-actin. Furthermore, VICs share with pericytes the expression of NG2 and platelet-derived growth factor receptor beta (PDGFR-β). The high expression of Ano1 and high activity of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase observed in VICs was diminished during hypertensive retinopathy suggesting that these cells might play a role on the motility of arteriolar annuli and that this function is altered during hypertension.

Conclusions

A novel type of VICs has been described in the arteriolar annuli of mouse retina. Remarkably, these cells undergo important molecular modifications during hypertensive retinopathy and might thus be a therapeutic target against this disease.

Risk factors for hypertensive retinopathy in a Chinese population with hypertension: The Beijing Eye study

Hypertensive retinopathy (HRP) is a clinical feature and systemic manifestation of hypertension. There have been few reports on the risk factors for hypertensive retinopathy in China. The aim of the present study was to describe risk factors associated with HRP in a population-based sample of Chinese patients with hypertension in Beijing. The clinical data of 228 hypertensive patients was retrospectively studied, including 112 patients with retinopathy for the HRP group and 116 patients without retinopathy for the NO-HRP group. Basic clinical data and plasma clinical indicators of the two groups were compared. Logistic regression models were used to assess risk factors associated with HRP. Duration of hypertension, smoking habits, family history of hypertension, plasma level of endothelin-1 (ET-1) and systolic and diastolic blood pressure were significantly increased in the HRP group compared with the NO-HRP group (P<0.05). No significant differences were identified between the two groups for other factors. Logistic regression models indicated that hypertension duration (P<0.001, 95% CI: 0.962-0.988) and ET-1 level (P<0.001, 95% CI: 1.144-1.278) were significantly associated with HRP. The diagnostic threshold of ET-1 to diagnosis HRP was 43.5 ng/l. Of the factors studied, longer hypertension duration and elevated ET-1 level were identified to be risk factors for HRP in patients with hypertension from Beijing. Detecting the plasma level of ET-1 in patients with hypertension may be a useful diagnostic indicator for HRP.

Retinal imaging to identify target organ damage in older Africans: A pilot study

By 2030, sub-Saharan Africa is forecast to see the steepest rise in the number of people with hypertension of any world region. Hypertensive retinopathy is known to be a common complication of hypertension in developed countries and some studies suggest it is associated with the presence of other hypertension-related end-organ damage (EOD) such as stroke and cardiovascular disease. In Tanzania hypertension is relatively more common than in other parts of sub-Saharan Africa, especially in the older population; however, the prevalence of hypertensive retinopathy and its association with EOD remain unknown. The authors conducted a cross-sectional study of elderly, community-dwelling, rural Tanzanians to determine the prevalence of hypertensive retinopathy and its association with hypertension and other forms of EOD. Hypertensive retinopathy was diagnosed based on retinal imaging. In a cohort of 61 patients with gradable images, the authors found the overall prevalence of hypertensive retinopathy to be 64% (n = 39), which was strongly associated with hypertension (X² [1] = 4.207, P = .004), with a significant trend towards more severe retinopathy with more severe hypertension (r = .377, P = .003). The authors did not find hypertensive retinopathy to be associated with other forms of EOD. Hypertensive retinopathy is highly prevalent in this population and is associated in most but not all cases with hypertension. These findings do not suggest that it could be used as a screening tool for EOD, but it is important to identify and educate patients with retinopathy about possible complications of the condition.

Microalbuminuria and Retinopathy among Hypertensive Nondiabetic Patients at a Large Public Outpatient Clinic in Southwestern Uganda

BACKGROUND

Routine testing of microalbuminuria and retinopathy is not done among patients with high blood pressure in resource-limited settings. We determined the prevalence of microalbuminuria and retinopathy and their risk factors among hypertensive patients at a large hospital in western Uganda.

METHODS

We consecutively recruited nondiabetic patients with hypertension at the outpatients' clinic over a period of 3 months. Spot urine samples were tested for urine albumin. Direct fundoscopy was done to assess retinal vasculature and optic disc for signs of hypertensive retinopathy. Logistic regression was done with retinopathy and microalbuminuria as primary outcomes.

RESULTS

We enrolled 334 patients and, of these, 208 (62.3%) were females, with median age of 55 years (range: 25-90). The prevalence of microalbuminuria was 59.3% (95% CI: 50.1-72.2) and that of retinopathy was 66.8% (95% CI: 58.6-76.5). The independent correlates of retinopathy and microalbuminuria were systolic blood pressure (SBP) > 140 mmHg (OR = 2.76, 95% CI: 1.29-5.93) and treatment with beta-blockers (OR = 2.16, 95% CI: 1.05-4.44). Use of ACEIs was unrelated to the study outcomes.

CONCLUSION

The prevalence of retinopathy and microalbuminuria is high. Clinicians should aim for better control of blood pressure and routinely perform fundoscopy and urine albumin, especially for patients with poorly controlled blood pressure.

The immunoproteasome subunit LMP10 mediates angiotensin II-induced retinopathy in mice

Inflammation has been implicated in a variety of retinal diseases. The immunoproteasome plays a critical role in controlling inflammatory responses, but whether activation of immunoproteasome contributes to angiotensin II (Ang II)-induced retinopathy remains unclear. Hypertensive retinopathy (HR) was induced by infusion of Ang II (3000 ng/kg/min) in wild-type (WT) and immunoproteasome subunit LMP10 knockout (KO) mice for 3 weeks. Changes in retinal morphology, vascular permeability, superoxide production and inflammation were examined by pathological staining. Our results showed that immunoproteasome subunit LMP10 expression and its trypsin-like activity were significantly upregulated in the retinas and serum of Ang II-infused mice and in the serum from patients with hypertensive retinopathy. Moreover, Ang II-infused WT mice showed an increase in the central retinal thickness, vascular permeability, reactive oxygen species (ROS) production and inflammation compared with saline controls, and these effects were significantly attenuated in LMP10 KO mice, but were aggravated in mice intravitreally injected with rAAV2-LMP10. Interestingly, administration of IKKβ specific inhibitor IMD-0354 remarkably blocked an Ang II-induced increase in vascular permeability, oxidative stress and inflammation during retinopathy. Mechanistically, Ang II-induced upregulation of LMP10 promoted PTEN degradation and activation of AKT/IKK signaling, which induced IkBα phosphorylation and subsequent degradation ultimately leading to activation of NF-kB target genes in retinopathy. Therefore, this study provided novel evidence demonstrating that LMP10 is a positive regulator of NF-kB signaling, which contributes to Ang II-induced retinopathy. Strategies for inhibiting LMP10 or IKKβ activity in the eye could serve as a novel therapeutic target for treating hypertensive retinopathy.

Review of the association between retinal microvascular characteristics and eye disease

Computerized retinal imaging technologies enable the static and dynamic measurement of a range of retinal microvascular parameters. Large population-based studies have reported associations between these microvascular indices and various ophthalmic diseases including diabetes, age-related macular degeneration, retinal artery embolism, retinal vein occlusion, glaucoma and non-glaucomatous optic neuropathies. Increasingly, sophisticated imaging and analysis techniques have the potential to provide relevant clinical information regarding disease risk and progression; however, further studies are required to verify associations and strengthen the predictive power of these techniques. We summarize the current state of knowledge regarding retinal microvascular characteristics and eye disease.

Retinal and Cortical Blood Flow Dynamics Following Systemic Blood-Neural Barrier Disruption

To consider whether imaging retinal vasculature may be used as a marker for cortical vessels, we compared fluorescein angiography flow dynamics before and after pharmacological disruption of blood-neural barriers. Sodium fluorescein (1%, 200 μl/kg) was intravenously delivered in anesthetized adult Long Evans rats (n = 44, brain = 18, retina = 26). In the brain cohort, a cranial window was created to allow direct visualization of surface cortical vessels. Video fluorescein angiography was captured using a rodent retinal camera at 30 frames/second and fluorescence intensity profiles were evaluated for the time to reach 50% brightness (half-rise), 50% decay (half-fall), and the plateau level of remnant fluorescence (offset, %). Cortical vessels fluoresced earlier (artery half-rise: 5.6 ± 0.2 s) and decayed faster (half-fall: 10.3 ± 0.2 s) compared to retinal vasculature. Cortical vessels also had a considerably higher offset, particularly in the capillaries/extravascular space (41.4 ± 2.7%) whereas pigment in the retina reduces such residual fluorescence. In a sub-cohort of animals, sodium deoxycholate (DOC, 0.06 M dissolved in sterile saline, 1 mL) was delivered intravenously to cause simultaneous disruption of the blood-brain and blood-retinal barriers. A separate group received saline as vehicle control. Fluorescein angiography was re-measured at 6 and 24 h after drug infusion and evaluated by comparing flow dynamics to the upper quartile (75%) of the control group. Retinal vasculature was more sensitive to DOC-induced disruption with a higher fluorescence offset at 6 h (47.3 ± 10.6%). A delayed effect was seen in cortical vessels with a higher offset evident only at 24 h (65.6 ± 10.1%). Here we have developed a method to quantitatively compare fluorescein angiography dynamics in the retina and superficial cortical vessels. Our results show that systemic disruption of blood-neural barriers causes vascular leakage in both tissues but earlier in the retina suggesting that pharmacological blood-neural barrier disruption may be detected earlier in the eye than in cortical vasculature.

Relationship between retinal vessel diameters and retinopathy in the Inter99 Eye Study

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Non-invasive imaging of the eye can throw light on systemic disease processes.

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Retinopathy and cardiovascular disease share many associated risk factors.

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Wider retinal vessel diameters are associated with retinopathy.

Purpose

To examine the association between retinal vessel diameters and retinopathy in participants with and without type 2 diabetes in a Danish population-based cohort.

Methods

The study included 878 persons aged 30 to 60 years from the Inter99 Eye Study. Retinopathy was defined as a presence of one or more retinal hemorrhages or one or more microaneurysms. Vessel diameters were expressed as central retinal artery equivalent diameter (CRAE) and central retinal vein equivalent diameter (CRVE). Multiple linear regression analyses were performed.

Results

Among participants with diabetes, CRAE was 6.3 µm (CI 95%: 1.0 to 11.6, p = 0.020) wider and CRVE was 7.9 µm (CI 95%: 0.7 to 15.2, p = 0.030) wider in those with retinopathy compared to those without retinopathy, after adjusting for age, gender, HbA1c, blood pressure, smoking, serum total and HDL cholesterol. In all participants, CRAE increased with presence of retinopathy (p = 0.005) and with smoking (p = 0.001), and CRAE decreased with hypertension (p < 0.001), high HDL cholesterol (p = 0.016) and age (p < 0.001). Central retinal vein equivalent diameter increased with presence of retinopathy (p = 0.022) and with smoking (p < 0.001), and decreased with higher HDL cholesterol (p < 0.001) and age (p = 0.015). Female gender was associated with wider CRVE (p = 0.029).

Conclusions

Wider retinal vessel diameters were associated with the presence of retinopathy in participants with diabetes, but not in participants without diabetes. The associations between retinal vessel diameters and known retinopathy risk factors were confirmed. These results suggest that information obtained by non-invasive imaging of the interior of the eye can contribute to a better understanding of systemic disease processes.

Retinal biomarkers provide "insight" into cortical pharmacology and disease

The retina is an easily accessible out-pouching of the central nervous system (CNS) and thus lends itself to being a biomarker of the brain. More specifically, the presence of neuronal, vascular and blood-neural barrier parallels in the eye and brain coupled with fast and inexpensive methods to quantify retinal changes make ocular biomarkers an attractive option. This includes its utility as a biomarker for a number of cerebrovascular diseases as well as a drug pharmacology and safety biomarker for the CNS. It is a rapidly emerging field, with some areas well established, such as stroke risk and multiple sclerosis, whereas others are still in development (Alzheimer's, Parkinson's, psychological disease and cortical diabetic dysfunction). The current applications and future potential of retinal biomarkers, including potential ways to improve their sensitivity and specificity are discussed. This review summarises the existing literature and provides a perspective on the strength of current retinal biomarkers and their future potential.

Neuro-Ophthalmology of Space Flight

BACKGROUND

To describe the history, clinical findings, and possible pathogenic etiologies of the constellation of neuro-ophthalmic findings discovered in astronauts after long-duration space flight and to discuss the terrestrial implications of such findings.

EVIDENCE ACQUISITION

Retrospective review of published observational, longitudinal examination of neuro-ophthalmic findings in astronauts after long-duration space flight; analysis of postflight questionnaires regarding in-flight vision changes in approximately 300 additional astronauts; and hypothesis generating for developing possible future countermeasures and potential implications for neuro-ophthalmic disorders on Earth. Astronauts with neuro-ophthalmic findings, which were not present at the start of a space flight mission and only seen on return from long-duration space missions to the International Space Station, will be discussed.

RESULTS

After 6 months of space flight, 7 astronauts had ophthalmic findings consisting of optic disc edema in 5, globe flattening in 5, choroidal folds in 5, cotton-wool spots in 3, nerve fiber layer thickening detected by optical coherence tomography in 6, and decreased near vision in 6. Five of 7 astronauts with near vision complaints had a hyperopic shift ≥+0.50 diopters (D) between pre-/post-mission spherical equivalent refraction in 1 or both eyes (range, +0.50 to +1.75 D). These 5 astronauts showed globe flattening on magnetic resonance imaging. A total of 6 lumbar punctures have been performed to date (4 in the originally described cohort) and documented opening pressures of 18, 22, 21, 21.5, 28, and 28.5 cm H2O. These were performed at 8, 66, 19, 7, 12, and 57 days after mission, respectively. The 300 postflight questionnaires documented that approximately 29% and 60% of astronauts on short-duration and long-duration missions, respectively, experienced a degradation in distant and near visual acuity. Some of these vision changes remain unresolved for years after flight. Several possible pathogenic mechanisms, as well as potential countermeasures and discussion of possible terrestrial implications, are described.

CONCLUSIONS

We previously hypothesized that the optic nerve and ocular changes that we described in astronauts may be the result of orbital and cranial cephalad fluid shifts brought about by prolonged microgravity exposure. The findings we reported previously and continue to see in astronauts may represent parts of a spectrum of ocular and cerebral responses to extended microgravity exposure. Future investigations hopefully will lead to countermeasures that can be used to eliminate or lessen the magnitude of these potentially harmful findings before long-duration space flight including the possibility of a manned mission to Mars.

Effect of physical activity on mortality risk among Americans with retinopathy

Background: Previous work demonstrates that retinopathy is associated with increased mortality risk, with physical activity inversely associated with retinopathy and all-cause mortality. However, no study has evaluated the effects of physical activity on mortality among those with existing retinopathy, which was this study’s purpose.

Methods: Data from the 2005-2006 National Health and Nutrition Examination Survey were utilized, with follow-up through 2011. Retinopathy was objectively-measured using the Canon Non-Mydriatic Retinal Camera CR6-45NM. Physical activity was objectively-measured via up to 7 days of accelerometry assessment.

Results: Six-hundred and seventy one adults (40-85 years) with complete data on the study variables constituted the analytic sample. During the follow-up period, 91 deaths occurred. In the sample, 35 886 person-months occurred with a mortality incidence rate of 2.5 deaths per1000 person-months. Among participants with mild retinopathy, those who met physical activity guidelines at baseline had a 63% reduced risk of all-cause mortality (HR _adjusted = 0.37; 95% CI:0.18-0.75; P = 0.007). Notably, physical activity was not associated with mortality risk among those with moderate/severe retinopathy (HR _adjusted = 0.371.72; 95% CI: 0.62-4.76; P = 0.27).

Conclusion: Physical activity is associated with reduced mortality risk among those with mild retinopathy, but not among those with moderate/severe retinopathy.

Retinal vascular changes in hypertensive patients in Ibadan, Sub-Saharan Africa

BACKGROUND

Earlier studies in Nigeria reported the rarity of retinal vascular changes in hypertensives. The aim of this study was to describe the various retinal vascular changes in the hypertensive patients of Nigeria.

PATIENTS AND METHODS

Nine hundred and three hypertensive patients were studied. This study was approved by the ethical and research committee of the University of Ibadan and University College Hospital, Ibadan, Nigeria. Blood pressure and anthropometric measurements were measured. Cardiac echocardiography was performed on 156 patients. All patients had dilated fundoscopy and fundus photography using the Kowa portable fundus camera and an Apple iPhone with 20 D lens. Statistical analysis was done with Statistical Packages for the Social Sciences (Version 21).

RESULTS

The mean age of patients was 57 years with a male:female ratio of 1. No retinopathy was found in 556 (61.5%) patients. In all, 175 (19.4%) patients had features of hypertensive retinopathy. Retinal vascular occlusion was a significant finding in 121 patients (13.4%), of which branch retinal vein occlusion, 43 (4.7%), and central retinal vein occlusion, 30 (3.3%), were the most prominent ones in cases. Hemicentral retinal vein occlusion, 26 (2.9%), and central retinal artery occlusion, 17 (1.9%), were significant presentations. Other findings included nonarteritic anterior ischemic optic neuropathy in five (0.6%) patients, hypertensive choroidopathy in seven (0.8%) patients, and hemorrhagic choroidal detachment in five (0.6%) patients. Left ventricular (LV) geometry was abnormal in 85 (55.5%) patients. Concentric remodeling, eccentric hypertrophy, and concentric hypertrophy were observed in 43 (27.6%), 26 (17.2%), and 15 (9.7%) patients, respectively. LV hypertrophy was found in 42 (27%) patients, while 60 (39%) patients had increased relative wall thickness. In this study, bivariate analysis showed a correlation between LV relative wall thickness and severity of retinopathy in both eyes (Spearman's coefficient 0.6; P=0.0004).

CONCLUSION

Hypertensive retinal vascular changes are not rare in Ibadan.

N-Terminal Pro-B–Type Natriuretic Peptide Is Related to Retinal Microvascular Damage

Objective—

N-terminal pro-B–type natriuretic peptide (NT-proBNP) is a marker of cardiac dysfunction and has been linked to various indices of large vessel disease. However, it remains unclear whether NT-proBNP also relates to microvascular damage. In a community-dwelling population, we studied the association between NT-proBNP and retinal microvascular damage.

Approach and Results—

From the population-based Rotterdam Study, we included 8437 participants (mean age 64.1 years and 59% women) without a history of cardiovascular disease, with NT-proBNP data and gradable retinal images. NT-proBNP serum levels were measured using an immunoassay. Retinopathy signs, that is, exudates, microaneurysms, cotton wool spots, and dot/blot hemorrhages, present on fundus photographs were graded in the total study population; retinal vascular calibers, that is, arteriolar and venular calibers, were semiautomatically measured in a subsample (n=2763) of the study population. We conducted cross-sectional analyses on the association between NT-proBNP and retinal microvascular damage using logistic and linear regression models, adjusting for age, sex, and cardiovascular risk factors. We found that NT-proBNP was associated with the presence of retinopathy (adjusted odds ratio [95% confidence interval] per SD increase in natural log-transformed NT-proBNP: 1.14 [1.03–1.27]). We also found that higher NT-proBNP was associated with narrower arteriolar calibers (adjusted mean difference in arteriolar caliber per SD increase in natural log-transformed NT-proBNP: −0.89 µm [−1.54 to −0.24]). This association remained unchanged after excluding participants with retinopathy signs.

Conclusions—

In participants free of clinical cardiovascular disease, higher levels of NT-proBNP are associated with retinal microvascular damage, suggesting a potential role for NT-proBNP as marker for small vessel disease.

Mortality in Older Persons with Retinopathy and Concomitant Health Conditions: The Age, Gene/Environment Susceptibility-Reykjavik Study

PURPOSE

To assess the impact of retinopathy on mortality in older persons with concomitant health conditions.

DESIGN

Population-based prospective cohort study.

PARTICIPANTS

A total of 4966 individuals aged 67 to 96 years (43.2% were male) from the Age, Gene/Environment Susceptibility-Reykjavik Study (AGES-RS).

METHODS

Retinopathy was evaluated from digital fundus images (2002-2006) using the modified Airlie House adaptation of the Early Treatment Diabetic Retinopathy Study protocol. Mortality was assessed through September 2013 (cause of death assigned through 2009). Cox proportional hazards regression models, with age as the time scale, estimated the association between retinopathy and death while controlling for risk factors and the presence of concomitant health conditions.

MAIN OUTCOME MEASURES

Mortality from all causes and cardiovascular disease (CVD).

RESULTS

Among the 4966 participants, 503 (10.1%) had diabetes and 614 (12.4%) had retinopathy at baseline. A subset of these (136 [2.7%]) had both diabetes and retinopathy. After a median follow-up of 8.6 years, 1763 persons died, 276 (45.0%) with retinopathy and 1487 (34.2%) without retinopathy, of whom 76 and 162 persons, respectively, also had diabetes. There were 366 deaths from CVD through 2009, 72 (11.7%) in persons with retinopathy and 294 (6.8%) in those without retinopathy. In multivariable analyses, retinopathy was significantly associated with all-cause mortality (hazard ratio [HR], 1.26; 95% confidence interval [CI], 1.10-1.43; P < 0.01) and CVD-related mortality (HR, 1.57; 95% CI, 1.20-2.06; P < 0.01). Findings were more striking in men: all-cause HR, 1.33 (95% CI, 1.11-1.60) and CVD HR, 1.81 (95% CI, 1.25-2.63). Risk of mortality was further increased among those with retinopathy concomitant with microalbuminuria (all-cause HR, 1.70; 95% CI, 1.03-2.23, and CVD HR, 2.04; 95% CI, 1.27-3.28) and those with retinopathy, microalbuminuria, and diabetes (all-cause HR, 2.01; 95% CI, 1.22-3.31, and CVD HR, 5.24; 95% CI, 1.91-14.42). History of clinical stroke increased the risk of CVD-related mortality among persons with retinopathy (HR, 3.30; 95% CI, 2.05-5.32), particularly those with retinopathy and diabetes (HR, 5.38; 95% CI, 1.80-16.06).

CONCLUSIONS

Even minimal retinopathy was a significant predictor of increased mortality in older persons, particularly men, irrespective of diabetes status. Persons with retinopathy may warrant closer clinical management of general health.