Retinal microvascular remodeling associates with adverse events in continuous-flow left ventricular assist device supported patients

BACKGROUND

Continuous-flow left ventricular assist device (cfLVAD) use is effective in supporting patients with end-stage heart failure (ESHF). Reduced flow pulsatility within the systemic circulation in cfLVAD-supported patients may lead to alterations within the microcirculation. Temporal changes in microvasculature in relation to adverse events in cfLVAD supported patients has not been studied. We aimed to profile changes within retinal microvasculature and its association with adverse events.

METHODS

Retinal photography was performed using Topcon TRC-NW8 non-mydriatic fundus camera in cfLVAD supported patients and ESHF control patients. Retinal measurements including arteriolar and venular caliber, fractal dimension, branching angle, and vessel tortuosity were evaluated using a validated semi-automated program. Demographic and adverse event data were documented.

RESULTS

172 images were recorded from 48 patients (n=29 cfLVAD, n=19 ESHF, mean age 54.2 ± 11.9 years). There were significant trends in retinal arteriolar caliber (B = -0.53 µm, 95% CI: -0.96 - -0.10, p = 0.016) and retinal fractal dimension parameters (B = 0.014, 95% CI: 0.001 - 0.002, p = 0.016) in linear mixed model regressions. Amongst cfLVAD patients, there was a significant association between the incidence of gastrointestinal bleeding and stepwise increases in retinal arteriolar-venular caliber ratio (HR: 3.03, 95% CI: 2.06 - 4.45, p = 0.005), a measure of arteriolar narrowing.

CONCLUSIONS

We have observed for the first time that alterations in retinal microvasculature in cfLVAD-supported patients may be associated with gastrointestinal bleeding. While understanding these temporal changes may predict future adverse events in cfLVAD-supported patients, further multi-center studies are required to confirm the associations observed.

Increased retinal venule diameter as a prognostic indicator for recurrent cerebrovascular events: a prospective observational study

Microvasculature of the retina is considered an alternative marker of cerebral vascular risk in healthy populations. However, the ability of retinal vasculature changes, specifically focusing on retinal vessel diameter, to predict the recurrence of cerebrovascular events in patients with ischemic stroke has not been determined comprehensively. While previous studies have shown a link between retinal vessel diameter and recurrent cerebrovascular events, they have not incorporated this information into a predictive model. Therefore, this study aimed to investigate the relationship between retinal vessel diameter and subsequent cerebrovascular events in patients with acute ischemic stroke. Additionally, we sought to establish a predictive model by combining retinal veessel diameter with traditional risk factors. We performed a prospective observational study of 141 patients with acute ischemic stroke who were admitted to the First Affiliated Hospital of Jinan University. All of these patients underwent digital retinal imaging within 72 hours of admission and were followed up for 3 years. We found that, after adjusting for related risk factors, patients with acute ischemic stroke with mean arteriolar diameter within 0.5-1.0 disc diameters of the disc margin (MAD0.5-1.0DD) of ≥ 74.14 μm and mean venular diameter within 0.5-1.0 disc diameters of the disc margin (MVD0.5-1.0DD) of ≥ 83.91 μm tended to experience recurrent cerebrovascular events. We established three multivariate Cox proportional hazard regression models: model 1 included traditional risk factors, model 2 added MAD0.5-1.0DD to model 1, and model 3 added MVD0.5-1.0DD to model 1. Model 3 had the greatest potential to predict subsequent cerebrovascular events, followed by model 2, and finally model 1. These findings indicate that combining retinal venular or arteriolar diameter with traditional risk factors could improve the prediction of recurrent cerebrovascular events in patients with acute ischemic stroke, and that retinal imaging could be a useful and non-invasive method for identifying high-risk patients who require closer monitoring and more aggressive management.

A narrative review of retinal vascular parameters and the applications (Part II): Diagnosis in stroke

The retina, as an external extension of the diencephalon, can be directly, noninvasively observed by ocular fundus photography. Therefore, it offers a convenient and feasible mode to study nervous system diseases. Caliber, tortuosity, and fractal dimension, as three commonly used retinal vascular parameters, are not only the reflection of structural changes in the retinal microcirculation but also capture the branching pattern or density changes of the retinal microvascular network. Therefore, it contributes to better reflecting the subclinical pathological changes (e.g., lacunar stroke and small cerebral vascular disease) and predicting the risk of incident stroke and recurrent stroke.

Relationship between Brachial-Ankle Pulse Wave Velocity and Fundus Arteriolar Area Calculated Using a Deep-Learning Algorithm

PURPOSE

Retinal vessels reflect alterations related to hypertension and arteriosclerosis in the physical status. Previously, we had reported a deep-learning algorithm for automatically detecting retinal vessels and measuring the total retinal vascular area in fundus photographs (VAFP). Herein, we investigated the relationship between VAFP and brachial-ankle pulse wave velocity (baPWV), which is the gold standard for arterial stiffness assessment in clinical practice.

METHODS

Retinal photographs (n = 696) obtained from 372 individuals who visited the Keijinkai Maruyama Clinic for regular health checkups were used to analyze VAFP. Additionally, the baPWV was measured for each patient. Automatic retinal-vessel segmentation was performed using our deep-learning algorithm, and the total arteriolar area (AA) and total venular area (VA) were measured. Correlations between baPWV and several parameters, including AA and VA, were assessed.

RESULTS

The baPWV was negatively correlated with AA (R = -0.40, n = 696, P < 2.2e-16) and VA (R = -0.36, n = 696, P < 2.2e-16). Independent variables (AA, sex, age, and systolic blood pressure) selected using the stepwise method showed a significant correlation with baPWV. The estimated baPWV, calculated using a regression equation with variables including AA, showed a better correlation with the measured baPWV (R = 0.70, n = 696, P < 2.2e-16) than the estimated value without AA (R = 0.68, n = 696, P < 2.2e-16).

CONCLUSIONS

AA and VA were significantly correlated with baPWV. Moreover, baPWV estimated using AA correlated well with the actual baPWV. VAFP may serve as an alternative biomarker for evaluating systemic arterial stiffness.

Retinal Microvascular Changes in Subtypes of Ischemic Stroke

Aims: Retinal microvasculature shares prominent similarities with the brain vasculature. We aimed to assess the association between retinal microvasculature and subtypes of ischemic stroke. Method: We consecutively enrolled ischemic stroke patients within 7 days of onset, who met the criteria of subtype of atherothrombosis (AT), small artery disease (SAD), or cardioembolism (CE) according to a modified version of the Trial of Org 10172 in Acute Stroke Treatment (NEW-TOAST). Digital fundus photographs were taken within 72 h of hospital admission using a digital camera (Topcon TRC-50DX), and fundus photographs were semi-automatically measured by software (Canvus 14 and NeuroLucida) for retinal vasculature parameters. Results: A total of 141 patients were enrolled, including 72 with AT, 54 with SAD, and 15 with CE. AT subtype patients had the widest mean venular diameter within 0.5-1.0 disk diameter (MVD0.5-1.0DD) followed by SAD and CE subtypes (86.37 ± 13.49 vs. 83.55 ± 11.54 vs. 77.90 ± 8.50, respectively, P = 0.047); CE subtype patients had the highest mean arteriovenous ratio within 0.5-1.0 disk diameter (MAVR0.5-1.0DD) followed by the AT and SAD subtype groups (0.97 ± 0.03 vs. 0.89 ± 0.99 vs. 0.89 ± 0.11, respectively, P = 0.010); SAD subtype patients were found with the highest mean venular tortuosity within 0.0-2.0 disk diameter (MVT0.0-2.0DD) followed by the AT and CE subtypes (1.0294 ± 0.0081 vs. 1.0259 ± 0.0084 vs. 1.0243 ± 0.0066, respectively, P = 0.024). After adjusting for clinic characteristics, MVD0.5-1.0DD was significantly different among AT, SAD, and CE subtypes (P = 0.033). By receiver operating characteristic curve analysis, MVD0.5-1.0DD predicted the AT subtype (area 0.690, 95% confidence interval, 0.566-0.815), with a cutoff value of 82.23 μm (sensitivity 61.1%, specificity 73.3%). Conclusion: Retinal MVD0.5-1.0DD (>82.23 μm) might be associated with the AT stroke subtype; however, we need large-scale prospective studies in future to explore the underlying mechanism and causal explanation for this finding.

Association of Retinal Microvascular Signs with Incident Atrial Fibrillation: The Multi-Ethnic Study of Atherosclerosis

PURPOSE

Microvascular diseases may contribute to the occurrence of atrial fibrillation (AF). Retinal microvascular signs that are similar to other microvasculature in the body and can be visualized directly via ophthalmoscopy may provide insights into such a relationship.

DESIGN

Prospective, longitudinal, multiethnic study.

PARTICIPANTS

We examined the association between retinal microvascular signs and incident AF in 4994 participants 47 to 86 years of age and free of prior AF who underwent fundus photography from 2002 through 2004 and were followed up through 2015 in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

Retinal microvascular signs evaluated include central retinal arteriolar equivalent and central retinal venular equivalent (CRVE) and presence of any retinopathy signs (e.g., retinal microaneurysms or hemorrhages). A multivariate Cox regression analysis was used to determine the relationship while adjusting for traditional risk factors, alcohol intake, body mass index, diabetes status, chronic kidney disease status, hemoglobin A1c level, C-reactive protein level, medications, and prevalent cardiovascular diseases or heart failure.

MAIN OUTCOME AND MEASURES

Incident AF events were identified using 12-lead electrocardiographic findings, hospital discharge records, and Medicare claims data.

RESULTS

During a median follow-up of 14.1 years, 643 AF events were identified. No association was found between any retinal microvascular signs and incident AF except for retinal focal arteriolar narrowing (hazard ratio, 1.75; 95% confidence interval, 1.06-2.87) in the overall population. However, in the subgroup analyses by gender, wider CRVE was associated with a higher risk of incident AF in women, but not in men (hazard ratio for every 10-μm increase in CRVE, 1.08 [95% confidence interval, 1.01-1.15] and 0.97 [95% confidence interval, 0.92-1.03], respectively; P = 0.041 for interaction).

CONCLUSIONS

No consistent pattern of association was found between retinal microvascular signs and incident AF. We observed an association in women, but not in men, of wider retinal venular calibers with incidence of AF. The reasons for a possible interaction are incompletely understood.

Measurement of normal retinal vascular pulse wave attenuation using modified photoplethysmography

Pulse wave attenuation characteristics reflect compliance and resistance properties of the vessel wall as well as initial pulse generation factors. Recently, it has become possible to measure and map the retinal vessel wall pulse wave amplitudes. Predictable pulse wave amplitude distribution may allow inferences to be made concerning vascular compliance and resistance. Twenty-eight eyes from sixteen subjects (8 male and 8 female) were examined using modified retinal photoplethysmography with simultaneous ophthalmodynamometry. This allowed the assessment of vessel wall pulsation amplitudes under a dynamic range of intraocular pressures. Pulse amplitudes were calculated using harmonic regression analysis. The pulse wave attenuation was measured under different ranges of ophthalmodynamometric force (ODF) as a function of distance along the vessel (VDist), which in turn was calculated in disc diameters (DD) from the center of the optic disc. A linear mixed-effects model with randomized slopes and intercepts was used to estimate the correlations between the logarithmically transformed harmonic regression wave amplitude (HRWa) and the Fourier trigonometric coefficients with the predictors (VDist and ODF). The retinal venous harmonic regression wave attenuation (coefficient value±standard error) -0.40±0.065/DD, (p-value < 0.00001, 95% confidence interval (CI) -0.53 to -0.27), which was approximately twice that of the arterial -0.17±0.048/DD, (p-value < 0.0004, 95% CI = -0.27 to -0.08). There was a positive correlation between attenuation of the harmonic regression wave and ophthalmodynamometric force in both vascular systems. The attenuation of all but the sine coefficient of the second Fourier harmonic (bn2) achieved statistical significance in the correlation with VDist. The cosine coefficient of the first Fourier harmonic an1 was the only coefficient to achieve statistical significance in the correlation with the predictors VDist and ODF in both vascular systems. The an1 coefficient value in the correlation with VDist was -3.79±0.78 and -1.269±0.37 (p < 0.0006), while this coefficient value in the correlation with ODF was 0.026±0.0099 and 0.009±0.04 (p < 0.01) in both the retinal veins and arteries respectively. The predictable attenuation characteristics in normal subjects suggest that this technique may allow the non-invasive quantification of retinal vascular compliance and other hemodynamic parameters.

Central arterial stiffness and retinal vessel calibers: the Atherosclerosis Risk in Communities Study-Neurocognitive Study

BACKGROUND

The retinal microvasculature provides a window to the cerebral vasculature and enables examination of changes in retinal caliber that may mimic those occurring in cerebrovascular disease. The association of central arterial stiffness and retinal vessel caliber in a population sample is not fully understood.

METHODS

In 1706 older adults (mean age 76.3, 58.1% women) from the population-based Atherosclerosis Risk in Communities Study, we examined the cross-sectional association of central arterial stiffness [carotid-femoral pulse wave velocity (cfPWV)] with retinal vessel calibers [central retinal arteriolar equivalent (CRAE) and central retinal vein equivalent (CRVE)]. We estimated the association of cfPWV with CRAE narrowing (<25th percentile) and CRVE widening (>75th percentile) after adjustment for age, sex, race-field center, BMI, smoking, and type 2 diabetes. We tested for effect modification by sex, hypertension, and type 2 diabetes.

RESULTS

Carotid-femoral PWV (m/s) was not associated with the odds of CRAE narrowing [odds ratio (OR): 0.99; 95% CI: 0.95-1.03]. The association of cfPWV with CRVE widening was stronger in those without hypertension (OR: 1.10; 95% CI: 1.01-1.20) versus those with hypertension (OR: 1.01 95% CI: 0.96-1.05) and slightly stronger in those with type 2 diabetes (OR: 1.07; 95% CI: 1.00-1.14) versus without type 2 diabetes (OR: 1.01; 95% CI: 0.96-1.06).

CONCLUSIONS

In older adults, cfPWV was associated with wider retinal venular caliber, particularly in individuals without hypertension. Central arterial stiffening may be associated with cerebral microvascular changes, as exhibited in its retinal vasculature component.

Quantitative Retinal Vascular Changes in Obstructive Sleep Apnea

PURPOSE

To examine the relationship between both static and dynamic retinal vascular caliber and the severity of obstructive sleep apnea (OSA).

DESIGN

Prospective cross-sectional study.

METHODS

Adult patients undergoing diagnostic polysomnography studies at a private Australian university teaching hospital were recruited. OSA severity was defined by the apnea-hypopnea index (AHI): severe >30, moderate >15-30, mild 5-15, and controls <5. Of 115 patients recruited (73 male; mean age 58 ± 13 years), there were 41 severe, 35 moderate, and 25 mild OSA patients and 14 controls. Static retinal vascular caliber was measured as the average diameter of retinal arterioles (CRAE) and venules (CRVE), and summarized as the arteriovenous ratio (AVR). Dynamic retinal vascular caliber was evaluated as the average pulsation amplitude of retinal arterioles (SRAP) and venules (SRVP). Comparisons across groups were performed using multivariate linear regression analysis. All results were adjusted for age, body mass index, and mean arterial pressure.

RESULTS

Increasing AHI was significantly associated with decreasing AVR (P = .008) and CRAE (P = .016). A significant relationship was demonstrated between increasing AHI and attenuated retinal vascular pulsation amplitude (arterioles P = .028; venules P < .0001).

CONCLUSIONS

Increasing OSA severity is independently associated with retinal arteriolar narrowing and attenuated vascular pulsation amplitude. The retinal vasculature is easily imaged, and may be a surrogate biomarker of cerebral and systemic vascular risk in patients with OSA requiring further comprehensive investigation.

The Association of Haptoglobin Gene Variants and Retinopathy in Type 2 Diabetic Patients: A Meta-Analysis

AIMS/INTRODUCTION

To collectively evaluate the association between haptoglobin (Hp) gene variants and diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM).

METHODS

A comprehensive literature review was performed for eligible studies. After inclusion and exclusion selection as well as quality assessment, those studies meeting quality standards were included. In this study, diabetic patients with retinopathy were selected as the case group and those ones without DR were treated as the control group. The recessive model, allele model, additive model, heterozygote model, and homozygote model were utilized to investigate the association of three Hp gene variants and DR. Subgroup analysis on different severity of DR including nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) was also conducted.

RESULTS

Six trials from different regions were finally included. A total of 1145 subjects containing 564 T2DM patients with retinopathy were included. The recessive model, allele model, additive model, and homozygote model results showed that Hp gene variants were not associated with DR, NPDR, and PDR. However, the heterozygote model indicated the association of Hp gene variants with DR.

CONCLUSIONS

No association was found between the Hp gene variants and PDR and NPDR. More studies are required to verify these findings.

Relationship of retinal vascular caliber variation with intracranial arterial stenosis

BACKGROUND & PURPOSE

To investigate the associations of retinal vessel parameters with intracranial arterial stenosis (ICAS) assessed by Transcranial Doppler ultrasonography.

METHOD

Data on transcranial Doppler ultrasonography and quantitative retinal vessel parameters from 627 participants in a health screening program were included in this study. ICAS was defined as >50% intracranial arterial stenosis (ICAS) based on criteria modified from the stroke outcomes and neuroimaging of intracranial atherosclerosis (SONIA) trial assessed by transcranial Doppler (TCD) ultrasonography. A semi-automated computer-assisted program (Singapore I Vessel Assessment) was used to measure the retinal vascular parameters from the photographs. Multivariate analysis was performed to identify which retinal vessel parameters were associated with increased risk of ICAS.

RESULTS

Among 627 participants, 24 (3.8%) had ICAS diagnosed by TCD. Subjects with ICAS had eyes with wider mean central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) in comparison to subjects without ICAS. Men (odds ratio [OR]:13.1, 95% confidence interval: 3.13-33.33) and a large standard deviation of mean arterial width (STDWa) were associated with ICAS (first vs. third tertile: OR ratio: 14.04, 95% confidence interval: 1.71-115.32; first vs. third tertile: OR ratio: 22.1, 95% confidence interval: 2.56-190.97) after adjusting for possible confounders.

CONCLUSION

A large variation in retinal arteriolar diameter is associated with ICAS. This study suggests the possible relationship between retina vessel and early changes within the cerebrovascular network.

Sex-Specific Association of Obstructive Sleep Apnea With Retinal Microvascular Signs: The Multi-Ethnic Study of Atherosclerosis

Background

Obstructive sleep apnea (OSA) is a common condition affecting more men than women. The relationship of OSA with microvascular disease is unclear, complicated by possible sex difference. Assessment of the relationship of OSA with retinal microvascular signs in men and women may provide insights into such a relationship.

Methods and Results

We examined the sex‐specific cross‐sectional association of OSA severity with retinal vascular calibers in 1808 participants, and with specific retinopathy signs in 1831 participants from a sample of 2060 participants aged 54 to 93 years who underwent successful polysomnography in the Multi‐Ethnic Study of Atherosclerosis, 2010–2012. OSA severity was defined by the apnea–hypopnea index (events/h) as none (<5), mild (5–14.9), moderate (15–29.9), and severe (≥30). As compared to no OSA, moderate/severe OSA in men was associated with retinal arteriolar narrowing (odds ratio [OR] and 95% CI for the narrowest quartile: 1.65 [1.00–2.71]) and retinal venular widening (1.80 [1.07–3.04] for the widest quartile), but not in women (odds ratio: 1.10 [0.67–1.81] and 0.91 [0.58–1.43], respectively) after adjusting for age, race/ethnicity, body mass index, pack‐years of cigarette smoking, alcohol intake, hypertension duration, diabetes mellitus duration, HbA1c levels, lipid profile, micro‐/macroalbuminuria, estimated glomerular filtration rate, β‐blockers use, antihypertensive therapy, and lipid‐lowering therapy. In contrast, severe OSA was associated with retinal microaneurysms in women, but not in men (odds ratio: 3.22 [1.16–8.97] and 0.59 [0.27–1.30], respectively).

Conclusions

The associations of OSA severity with retinal microvascular signs may differ by sex. Whether these findings were related to sex differences in OSA exposure needs further investigation.

Current Challenges in Diabetic Retinopathy: Are We Really Doing Better?

Management of diabetic complications has been a worldwide major global health issue for decades. Recent studies from many parts of the world indicate improvement in this area. However, it is unknown if such an improvement is being realized in Koreans. Although there is limited information regarding diabetic retinopathy management among Koreans, recent epidemiologic studies have indicated improved screening rates and less frequent visual impairment among type 2 diabetics. Moreover, results achieved with new diagnostic and treatment modalities aimed to improve diabetic retinopathy management are encouraging for both physicians and patients.

Ambulatory Aortic Stiffness Is Associated With Narrow Retinal Arteriolar Caliber in Hypertensives: The SAFAR Study

BACKGROUND

Arterial stiffness measured under static conditions reclassifies significantly cardiovascular (CV) risk and associates with narrower retinal arterioles. However, arterial stiffness exhibits circadian variation, thus single static stiffness recordings do not correspond to the "usual" 24 hr, awake, and asleep average arterial stiffness. We aimed to test the hypothesis that ambulatory 24 hr, awake, and asleep aortic (a) pulse wave velocity (PWV) associate with retinal vessel calibers, independently of confounders and of static arterial stiffness, in hypertensive individuals free from diabetes and CV disease.

METHODS

Digital retinal images were obtained (181 individuals, age: 53.9±10.7 years, 55.2% men) and retinal vessel calibers were measured with validated software to determine central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively); ambulatory (24 hr, awake, asleep) and static office aPWV were estimated by Mobil-O-Graph; and static office carotid to femoral (cf) PWV by SphygmoCor.

RESULTS

Regression analysis performed in 320 gradable retinal images showed that, after adjustment for confounders: (i) ambulatory aPWV was significantly associated with narrower retinal arterioles but not with venules; (ii) asleep aPWV had stronger associations with CRAE than awake aPWV; (iii) both ambulatory aPWV and cfPWV were associated mutually independently with narrower retinal arterioles; aPWV introduction in the model of cfPWV, improved model's R2 (P = 0.012). Similar discriminatory ability of 24 hr aPWV and of cfPWV to detect the presence of retinal arteriolar narrowing was found.

CONCLUSION

Ambulatory aPWV, estimated by an operator-independent method, provides additional information to cfPWV regarding the associations of arterial stiffness with the retinal vessel calibers.

Noninvasive assessment of arterial compliance of human cerebral arteries with short inversion time arterial spin labeling

A noninvasive method of assessing cerebral arterial compliance (AC) is introduced in which arterial spin labeling (ASL) is used to measure changes in arterial blood volume (aBV) occurring within the cardiac cycle. Short inversion time pulsed ASL (PASL) was performed in healthy volunteers with inversion times ranging from 250 to 850 ms. A model of the arterial input function was used to obtain the cerebral aBV. Results indicate that aBV depends on the cardiac phase of the arteries in the imaging volume. Cerebral AC, estimated from aBV and brachial blood pressure measured noninvasively in systole and diastole, was assessed in the flow territories of the basal cerebral arteries originating from the circle of Willis: right and left middle cerebral arteries (RMCA and LMCA), right and left posterior cerebral arteries (RPCA and LPCA), and the anterior cerebral artery (ACA). Group average AC values calculated for the RMCA, LMCA, ACA, RPCA, and LPCA were 0.56%±0.2%, 0.50%±0.3%, 0.4%±0.2%, 1.1%±0.5%, and 1.1%±0.3% per mm Hg, respectively. The current experiment has shown the feasibility of measuring AC of cerebral arteries with short inversion time PASL.

Fundus photography as a convenient tool to study microvascular responses to cardiovascular disease risk factors in epidemiological studies

The microcirculation consists of blood vessels with diameters less than 150 µm. It makes up a large part of the circulatory system and plays an important role in maintaining cardiovascular health. The retina is a tissue that lines the interior of the eye and it is the only tissue that allows for a non-invasive analysis of the microvasculature. Nowadays, high-quality fundus images can be acquired using digital cameras. Retinal images can be collected in 5 min or less, even without dilatation of the pupils. This unobtrusive and fast procedure for visualizing the microcirculation is attractive to apply in epidemiological studies and to monitor cardiovascular health from early age up to old age. Systemic diseases that affect the circulation can result in progressive morphological changes in the retinal vasculature. For example, changes in the vessel calibers of retinal arteries and veins have been associated with hypertension, atherosclerosis, and increased risk of stroke and myocardial infarction. The vessel widths are derived using image analysis software and the width of the six largest arteries and veins are summarized in the Central Retinal Arteriolar Equivalent (CRAE) and the Central Retinal Venular Equivalent (CRVE). The latter features have been shown useful to study the impact of modifiable lifestyle and environmental cardiovascular disease risk factors. The procedures to acquire fundus images and the analysis steps to obtain CRAE and CRVE are described. Coefficients of variation of repeated measures of CRAE and CRVE are less than 2% and within-rater reliability is very high. Using a panel study, the rapid response of the retinal vessel calibers to short-term changes in particulate air pollution, a known risk factor for cardiovascular mortality and morbidity, is reported. In conclusion, retinal imaging is proposed as a convenient and instrumental tool for epidemiological studies to study microvascular responses to cardiovascular disease risk factors.

Retinal microvascular responses to short-term changes in particulate air pollution in healthy adults

BACKGROUND

Microcirculation plays an important role in the physiology of cardiovascular health. Air pollution is an independent risk factor for the development and progression of cardiovascular diseases, but the number of studies on the relation between air pollution and the microcirculation is limited.

OBJECTIVES

We examined the relationship between short-term changes in air pollution and microvascular changes.

METHODS

We measured retinal microvasculature using fundus image analysis in a panel of 84 healthy adults (52% female), 22-63 years of age, during January-May 2012. Blood vessels were measured as central retinal arteriolar/venular equivalent (CRAE/CRVE), with a median of 2 measurements (range, 1-3). We used monitoring data on particulate air pollution (PM10) and black carbon (BC). Mixed-effect models were used to estimate associations between CRAE/CRVE and exposure to PM10 and BC using various exposure windows.

RESULTS

CRAE and CRVE were associated with PM10 and BC concentrations, averaged over the 24 hr before the retinal examinations. Each 10-µg/m3 increase in PM10 was associated with a 0.93-µm decrease (95% CI: -1.42, -0.45; p = 0.0003) in CRAE and a 0.86-µm decrease (95% CI: -1.42, -0.30; p = 0.004) in CRVE after adjusting for individual characteristics and time varying conditions such as ambient temperature. Each 1-µg/m3 increase in BC was associated with a 1.84-µm decrease (95% CI: -3.18, -0.51; p < 0.001) in CRAE.

CONCLUSIONS

Our findings suggest that the retinal microvasculature responds to short-term changes in air pollution levels. These results support a mechanistic pathway through which air pollution can act as a trigger of cardiovascular events at least in part through effects on the microvasculature.

Retinal microvascular signs and risk of stroke: the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND PURPOSE

Small-vessel disease contributes to the pathophysiology of stroke, and retinal microvascular signs have been linked to the risk of stroke. We examined the relationship of retinal signs with incident stroke in a multiethnic cohort.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective cohort study that enrolled participants without clinical cardiovascular diseases from 6 US communities between 2000 and 2002. Of the participants, 4849 (71.2%) had fundus photography performed in 2002 to 2004. Retinopathy and retinal vessel caliber were assessed from retinal images. Stroke risk factors including high-sensitivity C-reactive protein, carotid artery intima-media thickness, and coronary artery calcium were measured using standardized protocols. Incident stroke was confirmed from medical record review and death certificates.

RESULTS

After 6 years of follow-up, there were 62 incident strokes. Narrower retinal arteriolar caliber was associated with increased risk of stroke after adjusting for conventional cardiovascular risk factors (adjusted incidence rate ratio, 2.83; 95% CI, 1.34-5.95; P=0.006; adjusted hazard ratio, 3.01; 95% CI, 1.29-6.99; P=0.011). Retinopathy in persons without diabetes was associated with increased risk of stroke (adjusted adjusted incidence rate ratio, 2.96; 95% CI, 1.50-5.84; P=0.002; adjusted hazard ratio, 3.07; 95% CI, 1.17-8.09; P=0.023). These associations remained significant after adjusting for high-sensitivity C-reactive protein, carotid intima-media thickness, or coronary artery calcium.

CONCLUSIONS

Narrower retinal arteriolar caliber and retinopathy in nondiabetic persons were associated with increased risk of stroke in this relatively healthy multiethnic cohort independent of traditional risk factors and measures of atherosclerosis. The association between narrower retinal arteriolar caliber and stroke warrants further investigation.

Comparison of retinal vasodilator and constrictor responses in type 2 diabetes

PURPOSE

The retinal blood vessels provide a unique way to directly examine the human microvasculature, which is frequently damaged in individuals with diabetes. Previous studies have demonstrated that retinal flickering light-induced vasodilation and hyperoxia-induced vasoconstriction may operate by enhancing or reducing similar vasoregulatory factor(s), but a comparison between these two provocative stimuli in individuals with diabetes has not been studied. The purpose of the study was to examine the association between retinal flickering light-induced vasodilation and retinal hyperoxia-induced vasoconstriction in type 2 diabetic subjects and in healthy controls.

METHODS

Twenty men and women with type 2 diabetes and 10 men and women without diabetes between 21 and 75 years of age were recruited. Changes in retinal artery and vein diameters to flickering light and during hyperoxia (100% oxygen) stimuli were measured on the same visit using a noninvasive retinal imaging device (Dynamic Vessel Analyzer, Imedos Inc., Germany).

RESULTS

Compared with controls, diabetic subjects had impaired arterial vasodilator and vasoconstrictor responses to both flickering light and hyperoxia, respectively (both p<0.001). Merging both groups, an inverse correlation (r=-0.56; p=0.003) between the retinal artery's responses to flickering light-induced vasodilation and hyperoxia-induced vasoconstriction was demonstrated independent of glucose or insulin levels.

CONCLUSION

This suggests that both responses are attenuated to a similar degree in diabetic subjects and that the attenuation to both stimuli can be observed in retinal arteries and veins. This would suggest that similar vasoregulatory factor(s) might in part help to explain the retinal diameter responses between the two stimuli. One suggested common vasoregulator of vascular tone is nitric oxide; however, other factor(s) may be involved, which contribute to this association and require further research.

Retinal Vessel Analysis as a Tool to Quantify Risk of Diabetic Retinopathy

Diabetic retinopathy remains a leading cause of visual impairment and blindness worldwide. Identifying high-risk asymptomatic individuals who will likely develop the sight-threatening forms of diabetic retinopathy is an important clinical goal as it allows early, targeted implementation of preventive strategies to reduce their risk of vision loss. However, diabetic retinopathy is not a linear disease. Predicting the risk of diabetic retinopathy is challenging, and the current approach simply based on an assessment of traditional risk factors lacks precision. Retinal vessel analysis may offer a novel and noninvasive tool to improve risk prediction for diabetic retinopathy. With the use of this technology, studies have shown that a spectrum of structural alterations in the retinal vasculature can now be reliably quantified. In particular, variations in retinal vessel caliber have been consistently associated with the risks of retinopathy development and progression and shown to have prognostic predictive value above and beyond the conventional risk factors. Despite the promising results, there remain several unresolved issues that need to be addressed before the research findings on retinal vessel analysis are translated into clinical application. Coupling with standard clinical assessment, the additional information obtained from this technology could potentially guide clinical decision making, patient prognostication, and possibly monitor therapeutic response.

Childhood Vascular Risk Factors and Retinal Vessel Caliber

PURPOSE

Variations in retinal vessel caliber have been associated with risk of ocular and systemic vascular diseases in adults. In this study, we examined the relationships between childhood vascular risk factors and retinal vessel caliber in young healthy adolescents.

DESIGN

This was a cross-sectional study of 1225 adolescents recruited from 3 community-based schools in Singapore.

METHODS

Blood pressure and anthropometry measurements were obtained through standardized examinations. Birth weight was ascertained from health records completed by medical personnel soon after birth. Retinal vessel caliber was measured from retinal photographs using a semiautomated computer-based program following a validated standardized protocol.

RESULTS

After adjusting for age, sex, and other relevant factors, each SD increase in blood pressure levels (systolic or diastolic) was associated with narrower arteriolar caliber (1.61 μm; P < 0.001); each SD increase in body mass index was associated with narrower arteriolar caliber (1.49 μm; P < 0.001) and wider venular caliber (2.68 μm; P < 0.001), and each SD decrease in birth weight was associated with narrower arteriolar caliber (1.31 μm; P = 0.001).

CONCLUSIONS

Young adolescents with elevated blood pressure, obesity, or low birth weight have changes in retinal vessel caliber that are associated with ocular and systemic vascular diseases in adulthood. These findings provide evidence of possible adverse effects of childhood vascular risk factors on the retinal microvasculature early in life.

The relationship between aortic stiffness and changes in retinal microvessels among Asian ischemic stroke patients

Large-artery stiffness is a risk factor for stroke, including cerebral small-vessel disease. Retinal microvascular changes are thought to mirror those in cerebral microvessels. We investigated the relationship between aortic stiffness and retinal microvascular changes in Asian ischemic stroke patients. We studied 145 acute ischemic stroke patients in Singapore who had aortic stiffness measurements using carotid-femoral pulse wave velocity (cPWV). Retinal photographs were assessed for retinal microvessel caliber and qualitative signs of focal arteriolar narrowing, arteriovenous nicking and enhanced arteriolar light reflex. Aortic stiffening was associated with retinal arteriolar changes. Retinal arteriolar caliber decreased with increasing cPWV (r=-0.207, P=0.014). After adjusting for age, gender, hypertension, diabetes, mean arterial pressure and small-vessel stroke subtype, patients within the highest cPWV quartile were more likely to have generalized retinal arteriolar narrowing defined as lowest caliber tertile (odds ratio (OR) 6.84, 95% confidence interval (CI) 1.45-32.30), focal arteriolar narrowing (OR 13.85, CI 1.82-105.67), arteriovenous nicking (OR 5.08, CI 1.12-23.00) and enhanced arteriolar light reflex (OR 3.83, CI 0.89-16.48), compared with those within the lowest quartile. In ischemic stroke patients, aortic stiffening is associated with retinal arteriolar luminal narrowing as well as features of retinal arteriolosclerosis.

[Retinal vascular signs: a window to the heart?]

There is increasing recognition that coronary microvascular dysfunction also plays an important role in coronary heart disease. Little is known about this aspect of coronary heart disease due to difficulties in studying the coronary microcirculation directly. The retina is a unique site where the microcirculation can be imaged directly, providing an opportunity to study in vivo the structure and pathology of the human circulation and the possibility of detecting changes in microvasculature relating to the development of cardiovascular disease. This review covers the recent progress in research linking retinal vascular signs to coronary heart disease, and finds accumulating evidence that retinal vascular signs may provide a window into the health of the coronary microvasculature. The most widely studied signs, arteriolar narrowing, and more recently, venular dilation, are likely associated with increased risk of coronary heart disease in women, independent of traditional risk factors. Attempts to improve coronary heart disease risk prediction by incorporating retinal vessel calibre size into risk prediction scores complementing traditional algorithms such as the Framingham risk scores have so far been disappointing. Research is ongoing into the predictive utility of other retinal vascular signs. Retinal photography provides long-lasting records that enable monitoring of longitudinal changes in these retinal signs and vascular health. Full English text available fromwww.revespcardiol.org.

Retinopathy signs in people without diabetes: the multi-ethnic study of atherosclerosis

OBJECTIVE

To describe the prevalence of retinopathy and associations with cardiovascular risk factors in persons without diabetes in 4 racial/ethnic groups (white, black, Hispanic, and Chinese).

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

We included 6176 subjects aged 45-84 years without diabetes, selected from 6 United States communities.

METHODS

Fundus images were taken using 45° digital camera through dark-adapted pupils and were graded for retinopathy as defined by the Early Treatment Diabetic Retinopathy Study severity scale: microaneurysms, hemorrhages, cotton wool spots, intraretinal microvascular abnormalities, hard exudates, venous beading, and new vessels.

MAIN OUTCOME MEASURES

Retinopathy and the association with cardiovascular risk factors.

RESULTS

Prevalence rates of retinopathy in persons without diabetes were 12.5% overall, varying from 11.9% (white), 13.9% (black), 12.6% (Hispanic), to 17.2% (Chinese). Hypertension was strongly associated with retinopathy (odds ratio [OR], 1.47; 95% confidence interval [CI], 1.23-1.75). After adjusting for age, gender, race, and other parameters, smoking (OR, 1.50; 95% CI, 1.09-2.06) and increased internal carotid intima media thickness (OR, 1.22; 95% CI, 1.05-1.41) were associated with retinopathy. A range of serum inflammatory factors were examined, but none were found to be significant.

CONCLUSIONS

Retinopathy in persons without diabetes is common, varies with race/ethnicity, and associated with cardiovascular risk factors, including hypertension, smoking, and carotid artery intima media thickness.

Is diabetic retinopathy related to subclinical cardiovascular disease?

OBJECTIVE

Persons with diabetic retinopathy (DR) have an increased risk of clinical cardiovascular events. This study aimed to determine whether DR is associated with a range of measures of subclinical cardiovascular disease (CVD) in persons without clinical CVD.

DESIGN

Population-based, cross-sectional epidemiologic study.

PARTICIPANTS

Nine hundred twenty-seven persons with diabetes without clinical CVD in the Multi-Ethnic Study of Atherosclerosis.

METHODS

Diabetic retinopathy was ascertained from retinal photographs according to modification of the Airlie House Classification system. Vision-threatening DR (VTDR) was defined as severe nonproliferative DR, proliferative DR, or clinically significant macular edema. Subclinical CVD measures were assessed and defined as follows: high coronary artery calcium (CAC) score, defined as CAC score of 400 or more; low ankle-brachial index (ABI), defined as ABI of less than 0.9; high ABI, defined as ABI of 1.4 or more; high carotid intima-media thickness (IMT), defined as highest 25% of IMT; and carotid stenosis, defined as more than 25% stenosis or presence of carotid plaque.

MAIN OUTCOME MEASURES

Associations between DR and subclinical CVD measures.

RESULTS

The prevalence of DR and VTDR in this sample was 30.0% and 7.2%, respectively, and VTDR was associated with a high CAC score (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.15-4.73), low ABI (OR, 2.54; 95% CI, 1.08-5.99), and high ABI (OR, 12.6; 95% CI, 1.14-140.6) after adjusting for risk factors including hemoglobin A1c level and duration of diabetes. The association between VTDR and high CAC score remained significant after further adjustment for hypoglycemic, antihypertensive, and cholesterol-lowering medications. Diabetic retinopathy was not significantly associated with measures of carotid artery disease.

CONCLUSIONS

In persons with diabetes without a history of clinical CVD, the presence of advanced-stage DR is associated with subclinical coronary artery disease. These findings emphasize the need to be careful about the use of anti-vascular endothelial growth factor for the treatment of DR.

Air Pollution and the microvasculature: a cross-sectional assessment of in vivo retinal images in the population-based multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Long- and short-term exposures to air pollution, especially fine particulate matter (PM(2.5)), have been linked to cardiovascular morbidity and mortality. One hypothesized mechanism for these associations involves microvascular effects. Retinal photography provides a novel, in vivo approach to examine the association of air pollution with changes in the human microvasculature.

METHODS AND FINDINGS

Chronic and acute associations between residential air pollution concentrations and retinal vessel diameters, expressed as central retinal arteriolar equivalents (CRAE) and central retinal venular equivalents (CRVE), were examined using digital retinal images taken in Multi-Ethnic Study of Atherosclerosis (MESA) participants between 2002 and 2003. Study participants (46 to 87 years of age) were without clinical cardiovascular disease at the baseline examination (2000-2002). Long-term outdoor concentrations of PM(2.5) were estimated at each participant's home for the 2 years preceding the clinical exam using a spatio-temporal model. Short-term concentrations were assigned using outdoor measurements on the day preceding the clinical exam. Residential proximity to roadways was also used as an indicator of long-term traffic exposures. All associations were examined using linear regression models adjusted for subject-specific age, sex, race/ethnicity, education, income, smoking status, alcohol use, physical activity, body mass index, family history of cardiovascular disease, diabetes status, serum cholesterol, glucose, blood pressure, emphysema, C-reactive protein, medication use, and fellow vessel diameter. Short-term associations were further controlled for weather and seasonality. Among the 4,607 participants with complete data, CRAE were found to be narrower among persons residing in regions with increased long- and short-term levels of PM(2.5). These relationships were observed in a joint exposure model with -0.8 µm (95% confidence interval [CI] -1.1 to -0.5) and -0.4 µm (95% CI -0.8 to 0.1) decreases in CRAE per interquartile increases in long- (3 µg/m(3)) and short-term (9 µg/m(3)) PM(2.5) levels, respectively. These reductions in CRAE are equivalent to 7- and 3-year increases in age in the same cohort. Similarly, living near a major road was also associated with a -0.7 µm decrease (95% CI -1.4 to 0.1) in CRAE. Although the chronic association with CRAE was largely influenced by differences in exposure between cities, this relationship was generally robust to control for city-level covariates and no significant differences were observed between cities. Wider CRVE were associated with living in areas of higher PM(2.5) concentrations, but these findings were less robust and not supported by the presence of consistent acute associations with PM(2.5).

CONCLUSIONS

Residing in regions with higher air pollution concentrations and experiencing daily increases in air pollution were each associated with narrower retinal arteriolar diameters in older individuals. These findings support the hypothesis that important vascular phenomena are associated with small increases in short-term or long-term air pollution exposures, even at current exposure levels, and further corroborate reported associations between air pollution and the development and exacerbation of clinical cardiovascular disease. Please see later in the article for the Editors' Summary.

Differences between hypertensive and atherosclerotic lesions in retinal arteries assessed by Scheie's classification in hypertensive patients following stroke

Scheie's classification regarding hypertensive and atherosclerotic lesions in retinal arteries is generally used to assess the severity of hypertensive retinopathy and the risks of cardiovascular events in hypertensive patients. However, the differences between these two types of retinal artery lesions have not been fully examined. Both arterial stiffness and aortic root diameter are increased in hypertensive patients. The aim of this study was to elucidate differences in the two types of lesions by comparing their relationships to arterial stiffness and aortic root diameter in hypertensive patients following stroke. Fifty-two hypertensive patients following stroke were divided into five stages according to Scheie's classification of hypertensive (H stage 0-4) and atherosclerotic (S stage 0-4) lesions by ophthalmologists. Arterial stiffness was measured as brachial-ankle pulse wave velocity (baPWV) using an automatic waveform analyzer. Aortic root diameter was measured using M-mode echocardiography. The H and S stages in retinal arteries correlated with each other (ρ = 0.443, p < 0.001). However, the S stage correlated with baPWV (ρ = 0.385, p = 0.005) and the aortic root diameter (ρ = 0.285, p = 0.043), while the H stage did not correlate with these parameters. Multiple stepwise regression analysis demonstrated that the aortic root diameter was independently associated with S stage (β = 0.373, p = 0.006), even though baPWV was independently associated with neither S stage nor H stage. In conclusion, hypertensive lesions (H stage) in retinal arteries are associated with atherosclerotic lesions (S stage) in retinal arteries. However, S stage may reflect arterial stiffening and aortic root dilatation better than H stage in hypertensive patients following stroke. This difference between H and S stages of Scheie's classification should be kept in mind when considering the association between retinal microcirculation and large vessel arteriosclerosis.

Prevalence and risk factors for epiretinal membranes in a multi-ethnic United States population

PURPOSE

To describe the prevalence of and risk factors for epiretinal membrane (ERM) in a multi-ethnic population and to evaluate possible racial or ethnic differences.

DESIGN

Cross-sectional study.

PARTICIPANTS

Participants of the Multi-Ethnic Study of Atherosclerosis (MESA), examined at the second visit of the MESA when retinal photography was performed.

METHODS

Data on 5960 participants aged 45 to 84 years from MESA, including white, black, Hispanic, and Chinese persons from 6 United States communities, were analyzed. Epiretinal membrane was assessed from digital nonstereoscopic fundus photographs and was defined as cellophane macular reflex (CMR) without retinal folds or preretinal macular fibrosis (PMF) with retinal folds. Risk factors were assessed from standardized interviews, clinical examinations, and laboratory investigations.

MAIN OUTCOME MEASURES

Epiretinal membrane prevalence by ethnic or racial group and risk factors associated with ERM.

RESULTS

The prevalence of any ERM was 28.9%, of which 25.1% were CMR cases and 3.8% were PMF cases. The prevalence of ERM was significantly higher in Chinese persons (39.0%), compared with Hispanic (29.3%), white (27.5%), or black (26.2%; P<0.001) persons. In multivariate models, increasing age (odds ratio [OR], 1.19; 95% confidence interval [CI], 1.06-1.34, per year increase in age), diabetes (OR, 1.92; 95% CI, 1.39-2.65), and hypercholesterolemia (OR, 1.33; 95% CI, 1.04-1.69) were significantly associated with CMR.

CONCLUSIONS

This study showed that ERM was significantly more common in Chinese persons compared with whites, blacks, and Hispanics. Risk factors for ERM were increasing age, presence of diabetes, and hypercholesterolemia.

Retinal microvascular abnormalities and risk of lacunar stroke: Atherosclerosis Risk in Communities Study

BACKGROUND AND PURPOSE

The retinal microvasculature reflects cumulative small-vessel damage from hypertension and other vascular processes. No study has prospectively examined retinal findings in relation to the incidence of clinical lacunar stroke in comparison with other ischemic stroke subtypes.

METHODS

In 10 496 adults initially free of stroke, we related retinal findings imaged during 1993 to 1995 with the incidence of hospitalized ischemic strokes through 2005.

RESULTS

During a median of 11.2 years of follow-up, 338 incident ischemic strokes occurred (66 lacunar, 192 nonlacunar thrombotic, and 80 cardioembolic). Generalized arteriolar narrowing as measured by the central retinal arteriole equivalent was associated with an increased incidence of lacunar stroke (multivariate-adjusted hazard ratio [HR] per 1-SD decrement of central retinal arteriole equivalent=1.67; 95% CI, 1.23-2.26) but was not associated with other ischemic stroke subtypes. Generalized venular widening as measured by the central retinal venule equivalent was also positively associated with only lacunar stroke (multivariate-adjusted HR per 1-SD increment=1.44; 95% CI, 1.09-1.91). Retinal microvascular abnormalities were positively associated with lacunar stroke incidence (HR for focal arteriolar narrowing=2.22; 95% CI, 1.11=4.48; for arteriovenous nicking, HR=2.38; 95% CI, 1.20-4.71), whereas retinopathy signs (microaneurysms, retinal hemorrhages, and others) were positively associated with nonlacunar thrombotic (HR=2.41; 95% CI, 1.47-3.95) and cardioembolic (HR=2.25; 95% CI, 1.09-4.65) stroke incidence.

CONCLUSIONS

A narrower central retinal arteriole equivalent, wider central retinal venule equivalent, focal arteriolar narrowing, and arteriovenous nicking were predictive of lacunar stroke. Retinal imaging is useful in understanding the pathophysiology and mechanisms of cerebral small-vessel disease.

Retinal vascular caliber and brachial flow-mediated dilation: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND AND PURPOSE

Retinal vascular caliber changes have been shown to predict stroke, but the underlying mechanism of this association is unknown. We examined the relationship between retinal vascular caliber with brachial flow-mediated dilation (FMD), a measure of systemic endothelial function.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) is a population-based study of persons 45 to 84 years of age residing in 6 US communities free of clinical cardiovascular disease at baseline. Brachial FMD data were collected at baseline (July 2000 to June 2002), and retinal vascular caliber was measured from digital retinal photographs at the second examination, immediately after the first (August 2002 to January 2004). Data were available for 2851 participants for analysis.

RESULTS

The mean brachial FMD was 4.39+/-2.79%. After adjusting for age and gender, brachial FMD was reduced in persons with wider retinal venular caliber (changes in FMD -0.25, 95% CI, -0.36, - 0.13; P<0.001, per SD increase in venular caliber). This relationship persists after adjusting for systolic blood pressure, serum total cholesterol, use of lipid-lowering and antihypertensive medication, body mass index, current smoking status, and hemoglobinA(1C) (-0.18; 95% CI -0.30, - 0.06; P=0.004, per SD increase in venular caliber). Brachial FMD was not associated with retinal arteriolar caliber.

CONCLUSIONS

Persons with wider retinal venules have reduced brachial FMD, independent of other vascular risk factors. This suggests that retinal venular caliber, previously shown to predict stroke, may be a marker of underlying systemic endothelial dysfunction.

Hepatocyte growth factor and retinal arteriolar diameter in Singapore Chinese

OBJECTIVE

To assess if natural genetic variation in hepatocyte growth factor (HGF) is associated with altered retinal vessel diameter.

DESIGN

Two-stage cohort study.

PARTICIPANTS AND CONTROLS

Discovery set (set 1, n = 682 children) and confirmatory set (set 2, n = 1293 adults).

METHODS

Children in the discovery set were genotyped for a panel of genetic markers within HGF. Markers that were found to be associated significantly with altered retinal vessel diameter then were genotyped in the confirmatory set.

MAIN OUTCOME MEASURES

Increased or decreased retinal vessel diameter.

RESULTS

In the discovery set (n = 682 Chinese children aged 7 to 12 years), the variant allele of 4 HGF single nucleotide polymorphisms (SNPs) demonstrated association with larger retinal arteriolar diameter. The effect of the variant allele seems to be strongest within a recessive model of inheritance (P(min) = 4.6x10(-3)) for all 4 SNPs. When these 4 SNPs were assessed in a confirmatory study comprising 1293 Chinese adults, successful replication was observed for one of them (HGF +63962; rs5745752); the variant allele was observed to correlate with significantly larger retinal arteriolar diameter, with its effect again strongest within a model of recessive inheritance (P = 0.049). Analyzed as a quantitative trait, recessive carriage at HGF +63962 resulted in on average a 3.5-microm increase in retinal arteriolar diameter among children and a 2.5-microm increase in adults (P = 7.0x10(-3), analysis of variance; P = 3.0x10(-3), Kruskal-Wallis test).

CONCLUSIONS

This study suggests that natural variation within HGF is involved in the control of retinal arteriolar diameter and may be important in the pathogenesis of microvascular disease in individuals of Chinese descent.

Retinal vessel diameters and risk of hypertension: the Multiethnic Study of Atherosclerosis

OBJECTIVE

To describe the prospective relationship of retinal vessel diameters with risk of hypertension in a multiethnic population-based cohort.

METHODS

The Multi-Ethnic Study of Atherosclerosis is a population-based study of subclinical cardiovascular disease among white, African-American, Hispanic, and Chinese American adults aged 45-84 years. Retinal vessel diameters were measured using a standardized imaging software at the second examination (considered baseline in this analysis) and summarized as the central retinal artery/vein equivalent. Presence of retinopathy and retinal focal arteriolar narrowing and arteriovenous nicking was assessed by trained graders. Incidence of hypertension was defined among participants at risk as systolic blood pressure at least 140 mmHg, diastolic blood pressure at least 90 mmHg, or use of an antihypertensive medication.

RESULTS

Of the initial 6237 participants at baseline, 2583 were at risk of hypertension. After 3.2 +/- 0.5 years of follow-up, 448 (17.3%) participants developed hypertension. After adjusting for age, sex, race/ethnicity, the average of mean arterial blood pressure in the first and second examination, and other vascular risk factors, persons with narrower retinal arteriolar diameter and wider venular diameter at baseline were more likely to develop hypertension [odds ratio per SD decrease in central retinal artery equivalent 1.20, 95% confidence intervals 1.02, 1.42; and odds ratio per SD increase in central retinal vein equivalent 1.18, 95% confidence interval 1.02, 1.37]. Persons with focal arteriolar narrowing were also more likely to develop hypertension (odds ratio 1.80, 95% confidence interval 1.09, 2.97).

CONCLUSION

Findings from this multiethnic population confirm that narrower retinal arteriolar diameter and wider venular diameter are associated with the development of hypertension independent of traditional risk factors.

Prediction of incident stroke events based on retinal vessel caliber: a systematic review and individual-participant meta-analysis

The caliber of the retinal vessels has been shown to be associated with stroke events. However, the consistency and magnitude of association, and the changes in predicted risk independent of traditional risk factors, are unclear. To determine the association between retinal vessel caliber and the risk of stroke events, the investigators combined individual data from 20,798 people, who were free of stroke at baseline, in 6 cohort studies identified from a search of the Medline (National Library of Medicine, Bethesda, Maryland) and EMBASE (Elsevier B.V., Amsterdam, the Netherlands) databases. During follow-up of 5-12 years, 945 (4.5%) incident stroke events were recorded. Wider retinal venular caliber predicted stroke (pooled hazard ratio = 1.15, 95% confidence interval: 1.05, 1.25 per 20-micron increase in caliber), but the caliber of retinal arterioles was not associated with stroke (pooled hazard ratio = 1.00, 95% confidence interval: 0.92, 1.08). There was weak evidence of heterogeneity in the hazard ratio for retinal venular caliber, which may be attributable to differences in follow-up strategies across studies. Inclusion of retinal venular caliber in prediction models containing traditional stroke risk factors reassigned 10.1% of people at intermediate risk into different, mostly lower, risk categories.

Microvascular lesions in the brain and retina: The age, gene/environment susceptibility-Reykjavik study

OBJECTIVE

To investigate whether the severity and location of cerebral white matter hyperintensities (WMHs) and brain infarcts are correlated with the signs of retinal microvascular abnormalities in the elderly.

METHODS

The study included 4,176 men and women (mean age, 76 years) who participated in the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study. Digital retinal images of both dilated eyes were taken and evaluated for the presence of retinal focal arteriolar signs (focal arteriolar narrowing and arteriovenous nicking) and retinopathy lesions (retinal blot hemorrhages and microaneurysms). Brain magnetic resonance imaging scans were acquired and evaluated for the presence and distribution of cerebral infarcts and WMHs. Logistic and multinomial logistic models were constructed to estimate the association of retinal microvascular signs to brain lesions.

RESULTS

Controlling for demographic and major cardiovascular risk factors, we found that retinal focal arteriolar signs, but not retinopathy lesions, were significantly associated with an increasing load of subcortical and periventricular WMHs. The strongest association was found between retinal arteriolar signs and a heavier WMH load, specifically in the subcortical frontal lobe, and periventricular frontal and parietal caps. There was a tendency toward bilateral retinal focal arteriolar narrowing being more strongly associated with the heavier load of subcortical WMHs. Arteriovenous nicking was significantly associated with subcortical infarcts.

INTERPRETATION

In older adults, retinal focal arteriolar signs, but not retinopathy lesions, are correlated with the load of diffuse WMHs, particularly those located in the subcortical frontal lobe, and the periventricular frontal and parietal caps of the brain.

Differential response of peripheral arterial compliance-related indices to a vasoconstrictive stimulus

Peripheral arterial elastic properties are greatly affected by cardiovascular as well as other pathologies, and their assessment can provide useful diagnostic indicators. The photoplethysmographic technique can provide finger blood volume and pressure waveforms non-invasively, which can then be processed statically or beat-to-beat to characterize parameters of the vessel wall mechanics. We employ an occlusion-deflation protocol in 48 healthy volunteers to study peripheral artery compliance-related indices over positive and negative transmural pressure values as well as under the influence of a valid vasoconstrictor (cigarette smoking). We calculate beat-to-beat indices (compliance index CI, distensibility index DI, three viscoelastic model parameters (compliance C, viscosity R and inertia L), pressure-volume loop areas A and damping factor DF as well as symmetrical (C(max)) and asymmetrical (C(A)(max)) static compliance estimates, and their distributions over transmural pressure. All distributions are bell-shaped and centred on negative transmural pressure values. Distribution heights were significantly lower in the smoking group (w.r.t. the non-smoking group) for C, CI, DI and significantly higher in R and DF. The estimated volume signal time lag was also significantly lower in the smoking group. Left and right distribution widths were significantly different in all parameters/groups but DI (both groups), C(A)(max), A (smoking group) and L (non-smoking group), and positions of maxima/minima were significantly altered in C(A)(max), R and DF. C, DF and CI are seen to be most sensitive under this protocol, while C(max) and C(A)(max) are seen to be insensitive. These quantities provide complementary, time- and transmural pressure-dependent information about arterial wall mechanics, and the choice of index should depend on the physiological conditions at hand as well as relevant time resolution and transmural pressure range.

Increased aortic pulse wave velocity is associated with silent cerebral small-vessel disease in hypertensive patients

Aortic stiffness predicts an excess risk of stroke, supposedly via cerebral small-vessel disease. White matter hyperintensities, silent lacunar infarcts, and brain microbleeds, manifestations of cerebral small-vessel disease on neuroimaging, may precede overt cerebrovascular disease. Therefore, we assessed whether aortic stiffness is also related to such lesions. In 167 hypertensive patients (85 men) without a history of cardiovascular or cerebrovascular disease, a mean age of 51.8+/-13.1 years, and untreated office blood pressure levels of 169+/-25/104+/-12 mm Hg, we determined aortic pulse wave velocity and office and ambulatory 24-hour pulse pressure (off medication), as well as the volume of white matter hyperintensities and the presence of lacunar infarcts and microbleeds using brain MRI. Linear and logistic regression analyses were performed to assess the relationships between the arterial stiffness measures and brain lesions. Aortic stiffness and pulse pressure were significantly related to each of the brain lesions in univariate analyses (P<0.05). Multivariate analyses, adjusted for age, sex, brain volume, mean arterial pressure, and heart rate, showed that a higher pulse wave velocity was significantly associated with a greater volume of white matter hyperintensities (unstandardized regression coefficient: 0.041; 95% CI: 0.005 to 0.078; P<0.05) and the presence of lacunar infarcts (odds ratio [per SD increase in pulse wave velocity]: 1.78; 95% CI: 1.06 to 2.99; P<0.05) but not with microbleeds. The models for pulse pressure failed to reach statistical significance in multivariate analyses. In conclusion, aortic stiffness is independently associated with manifestations of cerebral small-vessel disease in hypertensive patients, linking systemic large- to cerebral small-artery disease.

Prevalence and risk factors of retinal arteriolar emboli: the Singapore Malay Eye Study

PURPOSE

To examine the prevalence and risk factors of retinal arteriolar emboli, a risk predictor of stroke, in an Asian population.

DESIGN

Population-based cross-sectional study.

METHODS

Retinal emboli were ascertained from retinal photographs obtained from both eyes of 3,265 Asian Malays, aged 40 to 80 years, according to a standardized protocol. Risk factors were assessed from detailed standardized interviews, clinical examinations, and laboratory investigations.

RESULTS

The overall prevalence of retinal emboli was 0.6% (95% confidence interval [CI], 0.58 to 0.62). A finding of retinal emboli was strongly associated with increasing age (P = .005, for trend), but age-stratified prevalence rates were still lower than those reported from previous population-based studies of White persons. After adjusting for age and gender, the presence of retinal emboli was associated with cigarette smoking (odds ratio [OR], 5.96; 95% CI, 1.75 to 20.32), elevated total cholesterol (OR, 5.21; 95% CI, 1.93 to 12.82), low-density lipoprotein cholesterol (OR, 2.98; 95% CI, 1.20 to 7.39), and self-reported history of angina (OR, 5.67; 95% CI, 1.62 to 19.91). These associations remained significant in multivariate analysis with additional adjustment for other risk factors.

CONCLUSIONS

Retinal emboli are less common in Asians than in similarly aged White persons, but are associated with similar cardiovascular risk factors.

Traditional and novel cardiovascular risk factors for retinal vein occlusion: the multiethnic study of atherosclerosis

PURPOSE

To describe the prevalence of retinal vein occlusion (RVO) and its association with cardiovascular, inflammatory, and hematologic risk factors in a multiethnic cohort.

METHODS

This was a population-based, cross-sectional study of 6147 participants (whites, blacks, Hispanics, Chinese) from six U.S. communities. RVO was defined from retinal photographs taken from both eyes according to a standardized protocol. Risk factors were assessed from interviews, examinations, and laboratory and radiologic investigations.

RESULTS

The prevalence of RVO was 1.1% (0.9% for branch RVO and 0.2% for central RVO) and was similar across different ethnic groups: 0.9% in whites, 1.2% in blacks, 1.2% in Hispanics, and 1.1% in Chinese (P = 0.76). Independent risk factors associated with RVO were hypertension (odds ratio [OR], 2.06; 95% confidence interval [CI], 1.18-3.59), older age (OR, 1.34; 95% CI, 1.00-1.81, per decade increase), less education (OR, 4.08; 95% CI, 2.20-7.54), hypertriglyceridemia (OR, 1.98; 95% CI, 1.10-3.56), renal dysfunction (OR, 1.85; 95% CI, 1.01-3.39), and the presence of retinal arteriovenous nicking (OR, 4.01; 95% CI, 2.06-7.81) and focal arteriolar narrowing (OR, 4.38; 95% CI, 1.44-13.34). RVO was not significantly associated with direct measures of subclinical atherosclerosis (e.g., carotid intima media thickness and coronary artery calcium scores) or markers of inflammation (e.g., C reactive protein, interleukin-6) and endothelial dysfunction (e.g., soluble intercellular adhesion molecule-1) or coagulation (e.g., D-dimer).

CONCLUSIONS

The prevalence of RVO is similar across different racial/ethnic groups. In the general population, RVO is associated with hypertension, dyslipidemia, and renal dysfunction, but not with atherosclerotic disease, systemic inflammation, and hematologic abnormalities.