Retinal Venular Caliber Research Articles

Vascular risk factors are associated with retinal arteriolar narrowing and venular widening in children and adolescents with type 1 diabetes.

The aim of the study was to describe the relationship of retinal arteriolar and venular calibre with vascular risk factors in children and adolescents with type 1 diabetes. In this hospital-based cross-sectional study, the medical files of 483 children and adolescents with type 1 diabetes were audited to collect retinal images and relevant clinical data. Retinal vascular calibre was measured using standardised protocols. After multivariable adjustments, a vascular risk profile that included: older age, higher serum creatinine, higher systolic blood pressure (SBP), higher body mass index (BMI), abnormal estimated glomerular filtration rate (eGFR), lower high-density lipoproteins (HDL) cholesterol, longer duration of diabetes and higher serum sodium was associated with narrower central retinal artery equivalent (CRAE) (95% CI=-4.10/-0.76, p=0.004). A specific risk profile, including higher total cholesterol level, higher BMI, lower physical activity level, higher HbA1c, higher triglyceride levels, female gender and lower socio-economic status, was associated with wider central retinal vein equivalent (CRVE) (95% CI=1.14/5.62, p=0.003). In summary, these findings support evidence that cardiovascular disease may have its origins early in life. Prospective and/or intervention studies are required to confirm whether the observed associations are involved in the causal pathway for retinal vascular calibre.

Influence of Maternal Gestational Hypertensive Disorders on Microvasculature in School-Age Children: The Generation R Study.

Gestational hypertensive disorders may lead to vascular changes in the offspring. We examined the associations of maternal blood pressure development and hypertensive disorders during pregnancy with microvasculature adaptations in the offspring in childhood. This study was performed as part of the Generation R Study in Rotterdam, the Netherlands (2002-2012), among 3,748 pregnant mothers and their children for whom information was available on maternal blood pressure in different periods of pregnancy and gestational hypertensive disorders. Childhood retinal arteriolar and venular calibers were assessed at the age of 6 years. We found that higher maternal systolic and diastolic blood pressures in early pregnancy were associated with childhood retinal arteriolar narrowing (P < 0.05). Higher maternal systolic blood pressure in late pregnancy, but not in middle pregnancy, was associated with childhood narrower retinal venular caliber (standard deviation score per standardized residual increase in systolic blood pressure: -0.05; 95% confidence interval: -0.08, -0.01). Paternal blood pressure was not associated with childhood retinal vessel calibers. Children of mothers with gestational hypertensive disorders tended to have narrower retinal arteriolar caliber (standard deviation score: -0.13, 95% confidence interval: -0.27, 0.01). Our results suggest that higher maternal blood pressure during pregnancy is associated with persistent microvasculature adaptations in their children. Further studies are needed to replicate these observations.

ED 04-4 RETINAL ARTERIOLAR STRUCTURE AS A MAKER OF VASCULAR HEALTH

Abstract The vasculature in the retina can be viewed directly and non-invasively in vivo, offers a unique perspective of the human microvasculature, and therefore the ability to understand early changes, processes, pathways and consequences of hypertension. In the past 15 years, advances in high resolution digital retinal photography and automated or semi-automated computer image software have been applied to measure and quantify a variety of retinal microvascular parameter, including retinal arteriolar and venular caliber, tortuosity, branching patterns and fractal dimensions. Clinical and epidemiological studies show that hypertension is strongly associated with many of these retinal microvascular changes. Concurrently, these retinal parameters are associated with a range of systemic conditions, including subclinical target organ damage (e.g., silent cerebral infarctions, myocardial perfusion, vascular remodelling, left ventricular hypertrophy and microalbuminuria) as well as clinical outcomes (e.g., clinical stroke, myocardial infarction, congestive heart failure, chronic kidney disease, cardiovascular mortality). Furthermore, some of the retinal measures are seen in children at risk of hypertension (e.g., higher BMI or low birth weight) and normotensive patients before they subsequently develop hypertension, suggesting that retinal microvascular changes may reflect the vascular remodelling processes in early hypertension. There are increasing data from genome-wide association studies that indicate genetic influence on retinal vascular caliber, possibly providing new genetic markers of systemic vascular diseases. Retinal vascular imaging provides the opportunity to interrogate early, subclinical microcirculatory effects associated with elevated blood pressure, and thus new insights into the pathogenesis and vascular consequences of hypertension.

The Impact of Macronutrients on Retinal Microvasculature among Singapore Pregnant Women during the Mid-Late Gestation.

BackgroundImbalanced macronutrient intakes can induce impairment of endothelial and vascular function, and further lead to metabolic and cardiovascular disease. However, little is known about the influence of such diets on endothelial and vascular dysfunction in pregnant women, even though high-fat diet is a known risk for pregnancy complications such as gestational diabetes and pre-eclampsia.ObjectiveWe aimed to assess the association between maternal macronutrient intakes (protein, fat and carbohydrates), dietary quality and retinal microvascular changes in a multi-ethnic Asian mother-offspring cohort.MethodsPregnant women (n = 614) with singleton pregnancies were recruited during their first trimester from June 2009 to Sep 2010. Maternal diet quality and macronutrient intakes, expressed as a percentage of total energy during pregnancy, were ascertained using 24 hr recalls and 3 d food diaries at 26–28 weeks gestation. Retinal examination was completed at the same clinic visit. Dietary quality was assessed and scored using the Health Eating Index in Asian Pregnant women (HEI-AP), while macronutrients intakes ware expressed as percentages of total energy and further log transformed for analysis. Associations were examined cross-sectionally by substitution models with the use of multiple linear regression.ResultsIn adjusted model, each 20 points decrease in HEI-AP score was associated with a significant increase of 1.70 μm (p<0.05) in retinal venular calibre. Each 0.1 log increase in percentage of total fat intake was associated with a significant increment of 1.84 μm (p<0.05) in retinal venular caliber. Additionally, each 0.1 log increase in percentage of mono-unsaturated fat intake was associated with an increment of 1.84 μm (p<0.01) in retinal venular caliber.ConclusionsIn this cross-sectional study, we found that women with higher fat and lower protein intakes, and lower diet quality tended to have wider retinal venular caliber, which is suggestive of suboptimal microvasculature.

Retinal microvasculature and white matter microstructure: The Rotterdam Study.

To investigate whether retinal microvascular damage is related to normal-appearing white matter microstructure on diffusion tensor MRI. We included 2,436 participants (age ≥45 years) from the population-based Rotterdam Study (2005-2009) who had gradable retinal images and brain MRI scans. Retinal arteriolar and venular calibers were measured semiautomatically on fundus photographs. White matter microstructure was assessed using diffusion tensor MRI. We used linear regression models to investigate the associations of retinal vascular calibers with markers of normal-appearing white matter microstructure, adjusting for age, sex, the fellow vascular caliber, and additionally for structural MRI markers and cardiovascular risk factors. Narrower arterioles and wider venules were associated with poor white matter microstructure: adjusted difference in fractional anisotropy per SD decrease in arteriolar caliber -0.061 (95% confidence interval -0.106 to -0.016), increase in venular caliber -0.054 (-0.096 to -0.011), adjusted difference in mean diffusivity per SD decrease in arteriolar caliber 0.048 (0.007-0.088), and increase in venular caliber 0.047 (0.008-0.085). The associations for venules were more prominent in women. Retinal vascular calibers are related to normal-appearing white matter microstructure. This suggests that microvascular damage in the white matter is more widespread than visually detectable as white matter lesions.

Assessment of retinal vascular calibres as a biomarker of disease activity in birdshot chorioretinopathy.

Birdshot chorioretinopathy (BCR) is a potentially blinding ocular disorder involving the retinal vasculature and choroid without any systemic manifestations. The objective of the study was to describe vascular calibre changes in BCR and analyse the possibility of this optical biomarker for staging and monitoring disease activity in BCR. This retrospective case-control study at a tertiary referral eye centre in the UK included 33 eyes from 21 patients with BCR and equal number of eyes from control subjects. Diagnosis of BCR was confirmed on fundus fluorescein and indocyanine green angiography. Vascular calibres were measured using validated semiautomated software. Patients with BCR had smaller retinal venular calibres central retinal venular equivalent (CRVE) than controls (211.3 versus 227.9μm, p=0.008). After adjusting for variables, the difference between the two groups for CRVE at baseline was statistically significant based on two different analysis methods. Central retinal venular equivalent (CRVE) was lower at the 6-month follow-up visit (206.2 versus 213.8μm, p-value=0.03), and arteriole-to-venule ratio was larger (0.74 versus 0.71, p=0.04) in subjects with BCR. Arteriolar calibre (CRAE) remained the same. This study provides novel insight into the pattern of vascular involvement in BCR. There was significant difference in the CRVE in patients with BCR. More studies are needed to correlate this data with visual function and treatment outcome and to validate the findings.

Chronic kidney disease and the severity of coronary artery disease and retinal microvasculature changes: a cross-sectional study.

Prior studies have suggested the association between incidence of coronary artery disease (CAD) with chronic kidney disease (CKD) and poor glomerular filtration function. However to the best of our knowledge, few studies have specifically assessed this relationship based on the severity of CAD as quantified using Extent and Gensini scores. Between June 2009 and January 2012, data were collected from 1,680 participants as part of the Australian Heart Eye Study (AHES) cohort. Coronary angiograms were scored according to Gensini (severity) and Extent scores. Retinal vessel calibres were measured using validated semi-automated software. Potential confounders were adjusted for using multivariate analysis. There were no significant associations found between CKD status with Extent and Gensini scores for CAD severity, both unadjusted and when adjusted for confounding factors. In unadjusted analyses, a significant association between CKD and narrower retinal arteriolar diameter was observed (P=0.0072). After multivariate adjustment, the association between CKD and retinal arteriolar diameter was attenuated and was no longer significant (P=0.1466). No associations were observed between retinal venular calibre and prevalent CKD. The present study demonstrated no independent associations between CKD and CAD severity. These results warrant validation by future large, prospective longitudinal studies.

N-Terminal Pro-B-Type Natriuretic Peptide Is Related to Retinal Microvascular Damage: The Rotterdam Study.

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. 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. 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.

New aspect for systemic effects of COPD: eye findings.

Chronic obstructive pulmonary disease (COPD) has multisystemic implications and comorbidities. Hypoxia and systemic inflammation are thought to involve oculary structures. In this study, our aim is to evaluate retinal nerve fiber and choroidal thickness and retinal vessel diameter using the spectral-domain optical coherence tomography (SD-OCT) in COPD subjects. Forty-three subjects diagnosed with COPD according to the Global Initiative for Chronic Obstructive Lung Disease criteria at the Pulmonology Department of Pamukkale University were enrolled in the study. All subjects underwent respiratory function testing and a carbon monoxide diffusion test. To determine hypoxic state, arterial blood gas analysis was performed. The control group consisted of 31 subjects with comparable age and gender distribution. All participants underwent a standard ophthalmic examination including visual acuity assessment, biomicroscopy, air-puff tonometry, indirect retinoscopy, and SD-OCT measurements. The mean subfoveal choroidal thickness (SFCT), foveal thickness, and retinal arteriolar caliber were found to be similar in both groups, while the mean retinal venular caliber value was markedly higher in the COPD group. The mean peripapillary retinal nerve fiber layer (RNFL) thickness was 100.2±11.8 µm in the COPD group and 105.6 ± 8.1 µm in the control group (P = .03). The inferior quadrant RNFL was significantly thinner in the COPD group. The results of this study showed increasing diameter of the retinal veins, thinning of the RNFL, and SFCT may be associated to chronic inflammation and hypoxia in subjects with COPD. Future guidelines may include ocular findings to the present systemic manifestations of COPD.

Inter-Relationships Between Retinal Vascular Caliber, Retinal Nerve Fiber Layer Thickness, and Glaucoma: A Mediation Analysis Approach.

The purpose of this study was to explore the interrelationships among retinal vascular caliber, retinal nerve fiber layer (RNFL), and glaucoma; in particular, whether the relationship between narrower retinal vascular caliber and glaucoma is mediated by thinning of RNFL. A total of 9407 participants, including 253 glaucoma and 195 primary open-angle glaucoma (POAG) cases from the Singapore Epidemiology of Eye Diseases Study were included in this study. All participants underwent standardized examinations. Glaucoma was defined according to International Society for Geographical and Epidemiologic Ophthalmology criteria. Logistic regression analyses were used to determine the total direct effects of retinal vascular calibers on glaucoma. Regression-based mediation analyses were used to evaluate the indirect effects of retinal vascular caliber on glaucoma through RNFL thinning. After we adjusted for relevant covariates, narrower retinal arteriolar caliber (per standard deviation [SD], 15.1-μm decrease) was associated with glaucoma (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.06-1.38) and POAG (OR, 1.23; 95% CI, 1.06-1.43). Similarly, narrower retinal venular caliber (per SD, 21.6μm decrease) was associated with glaucoma (OR, 1.51; 95% CI, 1.32-1.73) and POAG (OR, 1.64; 95% CI, 1.41-1.91). In addition, there were significant indirect effects of retinal vascular narrowing on glaucoma through thinning of RNFL (all P < 0.001), with mediated proportion of 36.9% and 12.9% in retinal arteriole- and venule-related analysis, respectively. Mediation analyses indicated that the effect of retinal vascular narrowing on glaucoma was partially the result of thinning of RNFL. These findings provide additional mechanistic insights linking retinal vascular narrowing and glaucoma.

32 Gestational hypertensive disorders and retinal microcirculation: The Generation R Study

Introduction Gestational hypertensive disorders (GHD), such as gestational hypertension (GH) and pre-eclampsia (PE), are risk factors for cardiovascular disease (CVD) in later life. Although the exact underlying mechanisms are not clear, changes in the microcirculation have also been proposed as a potential pathway in the development of CVD. Objective We examined whether a history of GHD is related to the maternal status of the microcirculation after pregnancy, as visualized by retinal imaging. Methods This study was embedded in the Generation R Study, a population-based prospective cohort study. Data on pregnancy, including GHD, and retinal vessel calibers six years after pregnancy were available for 3391 women. Retinal arteriolar and venular calibers were measured unilaterally from digitalized retinal photographs. Results Women with a history of PE had smaller retinal arteriolar calibers than women with a normotensive pregnancy (age-adjusted difference: −0.49SDS; 95% confidence interval (CI) −0.74, −0.25)). Additional adjustment for retinal venular caliber, ethnicity, educational level, smoking and pre-pregnancy BMI did not alter these results. After including mean arterial blood pressure at the time of retinal imaging, the association attenuated (−0.22SDS; 95% CI −0.43, −0.01), but remained significant. For women with a history of GH similar trends were observed, which disappeared after including mean arterial blood pressure at the time of retinal imaging in the model (−0.001SDS; 95% CI −0.14, 0.14). With respect to retinal venular calibers, we did not observe consistent trends for women with a history of PE. However, in women with a history of GH we observed larger venular calibers (multi-variable adjusted 0.16SDS; 95% CI 0.01, 0.31) than in women with a previous normotensive pregnancy. Conclusions Women with a history of GHD show an altered state of the microcirculation as reflected by smaller retinal arteriolar vessel calibers and larger retinal venular calibers six years after index pregnancy. These microvascular changes may contribute to the development of CVD in later life.

Characterization of Fatty Acid Binding Protein 7 (FABP7) in the Murine Retina

To characterize the mouse retina lacking fatty acid binding protein (FABP7-/-). Immunohistochemistry (IHC) was performed in 8-week-old mice to localize FABP7 in the retina. Retinal thickness was measured using image-guided spectral-domain optical coherence topography images. Electroretinography was carried out to assess retinal function. Fundus photography and fundus fluorescein angiography were performed on FABP7-/- and littermate wild-type (WT) mice, and retinal vascular changes were calculated using Singapore I Vessel Assessment (SIVA) analysis. Blood glucose levels were measured in the 8-week-old WT and FABP7-/- mice. In addition, retina was processed for trypsin digestion and retinal flat mounts for isolectin staining. Transcript levels of FABP7, VEGF, GFAP, and Na+K+ATPase were quantified using real-time PCR, and protein expression was analyzed by IHC and Western blot. Fatty acid binding protein 7 is expressed in the inner nuclear layer, outer plexiform layer, and photoreceptor inner segments. No significant difference in retinal thickness and ERG responses was observed between FABP7-deficient and WT retinas. FABP7-/- mice have significantly decreased retinal venular caliber retinal arteriolar fractal dimension compared with WT littermates. FABP7-/- mice showed significant increased areas of fluorescein leakage in the retina. FABP7-/- mice exhibited elevated high blood glucose levels compared with WT mice. Trypsin digested FABP7-/- mice retina showed increased acellular strands and endothelial cell drop outs, and reduced microvasculature branching compared with WT retina. FABP7-/- mice retina also have increased GFAP and VEGF expression. Fatty acid binding protein 7 is expressed in the retina and might play an important role in maintaining retinal vasculature.

Retinal Microvascular Calibers Are Associated With Enlarged Perivascular Spaces in the Brain.

Perivascular enlargement in the brain is a putative imaging marker for microvascular brain damage, but this link has not yet been confirmed using direct in vivo visualization of small vessels. We investigated the relation between microvascular calibers on retinal imaging and enlarged perivascular spaces (ePVSs) on brain magnetic resonance imaging. We included 704 participants from the Rotterdam study. Retinal arteriolar and venular calibers were measured semiautomatically on fundus photographs. ePVSs were counted in the centrum semiovale, basal ganglia, hippocampus, and mesencephalon, using a standardized rating method. We determined the association between retinal microvascular calibers and ePVSs with negative binomial regression models, adjusting for age, sex, the other vascular caliber, structural brain magnetic resonance imaging markers, and cardiovascular risk factors. Both narrower arteriolar and wider venular calibers were associated with more ePVSs in the centrum semiovale and hippocampal region. Rate ratios (95% confidence interval) for arterioles in the centrum semiovale and hippocampus were 1.07 (1.01-1.14) and 1.13 (1.04-1.22), respectively, and for venules 1.08 (1.01-1.16) and 1.09 (1.00-1.18), respectively. These associations were independent from other brain magnetic resonance imaging markers and cardiovascular risk factors. Retinal microvascular calibers are related to ePVSs, confirming the putative link between microvascular damage and ePVSs.

Assessing the Causality between Blood Pressure and Retinal Vascular Caliber through Mendelian Randomisation.

We aimed to determine the association between blood pressure (BP) and retinal vascular caliber changes that were free from confounders and reverse causation by using Mendelian randomisation. A total of 6528 participants from a multi-ethnic cohort (Chinese, Malays, and Indians) in Singapore were included in this study. Retinal arteriolar and venular caliber was measured by a semi-automated computer program. Genotyping was done using Illumina 610-quad chips. Meta-analysis of association between BP, and retinal arteriolar and venular caliber across three ethnic groups was performed both in conventional linear regression and Mendelian randomisation framework with a genetic risk score of BP as an instrumental variable. In multiple linear regression models, each 10 mm Hg increase in systolic BP, diastolic BP, and mean arterial BP (MAP) was associated with significant decreases in retinal arteriolar caliber of a 1.4, 3.0, and 2.6 μm, and significant decreases in retinal venular caliber of a 0.6, 0.7, and 0.9 μm, respectively. In a Mendelian randomisation model, only associations between DBP and MAP and retinal arteriolar narrowing remained yet its significance was greatly reduced. Our data showed weak evidence of a causal relationship between elevated BP and retinal arteriolar narrowing.

Relationship of retinal vascular calibre and diabetic retinopathy in Chinese patients with type 2 diabetes mellitus: the Desheng Diabetic Eye Study.

To describe the relationship of retinal arteriolar and venular calibre with diabetic retinopathy (DR) and related risk factors, including glucose levels and other biomarkers in a Chinese population with type 2 diabetes mellitus (T2DM). A cross-sectional study. Patients with T2DM were recruited from a local community in urban Beijing. Seven fields 30° colour fundus photographs were taken and examined for the presence and severity of DR using a standardised grading system. Retinal vascular calibres were measured and expressed as average central retinal arteriolar and venular equivalent using a computer-based program. A total of 1340 patients with T2DM were included for analysis. Of these, 472 (35.22%) had DR. Wider retinal venular calibre, but not arteriolar calibre, was associated with increasing glucose and glycosylated haemoglobin A1c levels (p<0.006) and dyslipidaemia (p for trend <0.05). After adjusting for possible covariates, the higher quartile of retinal venular calibre was associated with higher prevalence of any DR (OR 2, 95% CI 1.36 to 2.95). Venular calibre increased from 224.33 μm in those without retinopathy to 231.21 μm in those with mild, 241.01 μm in those with moderate and 235.65 μm in those with severe retinopathy (p for trend <0.001). Arteriolar calibre was not associated with DR. In the current study, wider venular calibre, but not arteriolar calibre, was shown to be associated with development and increased severity of DR independently from other risk factors in a Chinese diabetic population.

Retinal nerve fiber layer thickness and retinal vessel calibers in children with thalassemia minor.

Objectives:Evaluation of the peripapillary retinal nerve fiber layer thickness, subfoveal choroidal thickness, and retinal vessel caliber measurements in children with thalassemia minor.Methods:In this cross-sectional and comparative study, 30 thalassemia minor patients and 36 controls were included. Heidelberg spectral domain optical coherence tomography was used for peripapillary retinal nerve fiber layer thickness, subfoveal choroidal thickness, and retinal vessel caliber measurements.Results:There was no statistically significant difference in retinal nerve fiber layer thickness and subfoveal choroidal thickness between the two groups (p > 0.05). There was no correlation between retinal nerve fiber layer thickness and hemoglobin values. Both the arterioral and venular calibers were higher in thalassemia minor group (p < 0.05).Conclusion:There is increased retinal arterioral and venular calibers in children with thalassemia minor compared with controls.

Association between Retinal Arteriolar and Venule Calibre with Prevalent Heart Failure: A Cross-Sectional Study.

BackgroundThere is evidence to suggest that microvascular disease, particularly diabetic retinopathy, plays a role in the pathogenesis of HF. However, whether changes in retinal vessel calibre predicts HF is unclear. The purpose of this study was to examine the association of retinal microvascular structure with prevalent heart failure (HF).MethodsThe Australian Heart Eye Study (AHES) is a cross-sectional study that surveyed 1680 participants who presented to a tertiary referral hospital for the evaluation of potential coronary artery disease by coronary angiography. Retinal vessel calibre was graded using retinal photography and participants’ self-reported echocardiography-confirmed HF was obtained via an extensive medical questionnaire.ResultsThere were 107 participants (8.1%) with prevalent self-reported HF. Persons with wider retinal arteriolar calibre (comparing highest versus lowest tertile or reference) were more likely to have prevalent HF (OR 3.5; 95% CI, 1.7–7.2) when adjusted for age and sex. After further adjustment for body mass index, hypertension, diabetes, smoking status, triglycerides and estimated glomerular filtration rate, this association remained significant (OR 4.5; 95% CI, 2.0–9.8). After further stratification, this association remained significant among participants with diabetes (OR 10.3; 95% CI, 2.7–39.3) but not in those without diabetes (OR 2.7; 95% CI, 0.9–7.5). The strength of this association was not dependent on the length of history of diabetes, or retinopathy status. There was no significant association between retinal venular calibre and prevalence of HF.ConclusionsWider retinal arteriolar diameter was significantly and independently associated with prevalent HF in participants of a cross-sectional study. This association was significant stronger among participants with diabetes compared to without diabetes. No association was found between retinal venule calibre with prevalent HF.

A prospective case-control study to investigate retinal microvascular changes in acute dengue infection

Dengue infection can affect the microcirculation by direct viral infection or activation of inflammation. We aimed to determine whether measured retinal vascular parameters were associated with acute dengue infection. Patients with acute dengue were recruited from Communicable Diseases Center, Singapore and age-gender-ethnicity matched healthy controls were selected from a population-based study. Retinal photographs were taken on recruitment and convalescence. A spectrum of quantitative retinal microvascular parameters (retinal vascular caliber, fractal dimension, tortuosity and branching angle) was measured using a semi-automated computer-based program. (Singapore I Vessel Assessment, version 3.0). We included 62 dengue patients and 127 controls. Dengue cases were more likely to have wider retinal arteriolar and venular calibers (158.3 μm vs 144.3 μm, p < 0.001; 227.7 μm vs 212.8 μm, p < 0.001; respectively), higher arteriolar and venular fractal dimensions (1.271 vs 1.249, p = 0.002; 1.268 vs. 1.230, p < 0.001, respectively), higher arteriolar and venular tortuosity (0.730 vs 0.546 [x104], p < 0.001; 0.849 vs 0.658 [x104], p < 0.001; respectively), compared to controls. Resolution of acute dengue coincided with decrease in retinal vascular calibers and venular fractal dimension. Dengue patients have altered microvascular network in the retina; these changes may reflect pathophysiological processes in the immune system.

Metabolic syndrome and retinal microvascular calibre in a high cardiovascular disease risk cohort

AimsTo investigate the independent associations between metabolic syndrome and retinal vessel calibre in a high cardiovascular risk cohort, and to determine whether these associations also exist in patients without diabetes,...

Low serum testosterone and increased diastolic ocular perfusion pressure: a risk for retinal microvasculature.

Low levels of testosterone in men and changes in retinal microvascular calibre are both associated with hypertension and cardiovascular disease risk. Sex hormones are also associated with blood flow in microvascular beds which might be a key intermediate mechanism in the development of hypertension. Whether a direct association between endogenous testosterone and retinal microvascular calibre exists is currently unknown. We aimed to determine whether testosterone is independently associated with ocular perfusion via a possible association with retinal vascular calibre or whether it plays only a secondary role via its effect on blood pressure in a bi-ethnic male cohort. A total of 72 black and 81 white men (28-68 years of age) from the follow-up phase of the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study were included in this sub-study. Ambulatory pulse pressure and intraocular perfusion pressures were obtained, while metabolic variables and testosterone were measured from fasting venous blood samples. Retinal vascular calibre was quantified from digital photographs using standardised protocols. The black men revealed a poorer cardiometabolic profile and higher pulsatile pressure (>50 mm Hg), intraocular pressure and diastolic ocular perfusion pressure than the white men (p≤0.05). Only in the white men was free testosterone positively associated with retinal calibre, i.e. arterio-venular ratio and central retinal arterial calibre and inversely with central retinal venular calibre. These associations were not found in the black men, independent of whether pulse pressure and ocular perfusion pressure were part of the model. These results suggest an independent, protective effect of testosterone on the retinal vasculature where an apparent vasodilatory response in the retinal resistance microvessels was observed in white men.