The relationship between retinal arteriolar and venular calibers is genetically mediated, and each is associated with risk of cardiovascular disease

Fine-mapping of retinal vascular complexity loci identifies Notch regulation as a shared mechanism with myocardial infarction outcomes

There is increasing evidence that the complexity of the retinal vasculature measured as fractal dimension, Df, might offer earlier insights into the progression of coronary artery disease (CAD) before traditional biomarkers can be detected. This association could be partly explained by a common genetic basis; however, the genetic component of Df is poorly understood. We present a genome-wide association study (GWAS) of 38,000 individuals with white British ancestry from the UK Biobank aimed to comprehensively study the genetic component of Df and analyse its relationship with CAD. We replicated 5 Df loci and found 4 additional loci with suggestive significance (P < 1e-05) to contribute to Df variation, which previously were reported in retinal tortuosity and complexity, hypertension, and CAD studies. Significant negative genetic correlation estimates support the inverse relationship between Df and CAD, and between Df and myocardial infarction (MI), one of CAD's fatal outcomes. Fine-mapping of Df loci revealed Notch signalling regulatory variants supporting a shared mechanism with MI outcomes. We developed a predictive model for MI incident cases, recorded over a 10-year period following clinical and ophthalmic evaluation, combining clinical information, Df, and a CAD polygenic risk score. Internal cross-validation demonstrated a considerable improvement in the area under the curve (AUC) of our predictive model (AUC = 0.770 ± 0.001) when comparing with an established risk model, SCORE, (AUC = 0.741 ± 0.002) and extensions thereof leveraging the PRS (AUC = 0.728 ± 0.001). This evidences that Df provides risk information beyond demographic, lifestyle, and genetic risk factors. Our findings shed new light on the genetic basis of Df, unveiling a common control with MI, and highlighting the benefits of its application in individualised MI risk prediction.

Progression of retinopathy and incidence of cardiovascular disease: findings from the Chronic Renal Insufficiency Cohort Study

PURPOSE

Chronic kidney disease (CKD) patients often develop cardiovascular disease (CVD) and retinopathy. The purpose of this study was to assess the association between progression of retinopathy and concurrent incidence of CVD events in participants with CKD.

DESIGN

We assessed 1051 out of 1936 participants in the Chronic Renal Insufficiency Cohort Study that were invited to have fundus photographs obtained at two timepoints separated by 3.5 years, on average.

METHODS

Using standard protocols, presence and severity of retinopathy (diabetic, hypertensive or other) and vessel diameter calibre were assessed at a retinal image reading centre by trained graders masked to study participants' information. Participants with a self-reported history of CVD were excluded. Incident CVD events were physician adjudicated using medical records and standardised criteria. Kidney function and proteinuria measurements along with CVD risk factors were obtained at study visits.

RESULTS

Worsening of retinopathy by two or more steps in the EDTRS retinopathy grading scale was observed in 9.8% of participants, and was associated with increased risk of incidence of any CVD in analysis adjusting for other CVD and CKD risk factors (OR 2.56, 95% CI 1.25 to 5.22, p<0.01). After imputation of missing data, these values were OR=1.66 (0.87 to 3.16), p=0.12.

CONCLUSION

Progression of retinopathy is associated with higher incidence of CVD events, and retinal-vascular pathology may be indicative of macrovascular disease even after adjustment for kidney diseases and CVD risk factors. Assessment of retinal morphology may provide important information when assessing CVD in patients with CKD.

Retinal microvasculature: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe distributions and concordance of retinal microvasculature measurements in a population-based sample of Australian parent-child dyads at child age 11-12 years.

DESIGN

Cross-sectional Child Health CheckPoint study, between waves 6 and 7 of the national population-based Longitudinal Study of Australian Children (LSAC).

SETTING

Assessment centres in seven Australian cities, February 2015-March 2016.

PARTICIPANTS

Of the 1874 participating families, 1288 children (51% girls) and 1264 parents (87% mothers, mean age 43.7) were analysed. Diabetic participants and non-biological pairs were excluded from concordance analyses.

OUTCOME MEASURES

Retinal photographs were taken by non-mydriatic fundus camera. Trained graders scored vascular calibre using semi-automated software, yielding estimates of central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) and arteriolar-venular ratio (AVR). Pearson's correlation coefficients and multivariable linear regression models assessed parent-child concordance. Survey weights and methods accounted for LSAC's complex sampling, stratification and clustering within postcodes.

RESULTS

Mean (SD) of CRAE and CRVE were larger in children (159.5 (11.8) and 231.1 (16.5) μm, respectively) than parents (151.5 (14.0) and 220.6 (19.0) μm), yielding similar AVR (children 0.69 (0.05), parents 0.69 (0.06)). Correlation coefficients for parent-child pairs were 0.22 (95% CI 0.16 to 0.27) for CRAE, 0.23 (95% CI 0.17 to 0.28) for CRVE and 0.18 (95% CI 0.13 to 0.24) for AVR. Mother-child and father-child values were similar (0.20 and 0.32 for CRAE, 0.22 and 0.29 for CRVE, respectively). Relationships attenuated slightly on adjustment for age, sex, blood pressure, diabetes and body mass index. Percentiles and concordance are presented for the whole sample and by sex.

CONCLUSIONS

Arteriolar and venular calibre were similar to previously documented measures in midlife adult and late childhood populations. Population parent-child concordance values align with moderate polygenic heritability reported in smaller studies.

Determinants of retinal microvascular features and their relationships in two European populations

Supplemental Digital Content is available in the text

Objectives:

To examine factors influencing retinal vasculature in two environmentally contrasted, cross-sectional studies of adult participants of European descent and to estimate the extent and specificity of genetic contributions to each retinal vasculature feature.

Methods:

Retinal images from 1088 participants in the Orkney Complex Disease Study and 387 in the CROATIA-Korčula study, taken using the same nonmydriatic camera system and graded by the same person, were evaluated. Using general linear models, we estimated the influence of an extensive range of systemic risk factors, calculated retinal traits heritabilities and genetic correlations.

Main results:

Systemic covariates explained little (<4%) of the variation in vessel tortuosity, substantially more (>10%, up to 31.7%) of the variation in vessel width and monofractal dimension. Suggestive not well trodden associations of biological interest included that of urate, tissue plasminogen activator and cardiac PR interval with arteriolar narrowing, that of carotid intima–media thickness with less-tortuous arterioles and of cardiac QT interval with more tortuous venules. The genetic underpinning of tortuosity is largely distinct from that of the other retinal vascular features, whereas that of fractal dimension and vessel width greatly overlaps. The previously recognized influence of ocular axial length on vessel widths was high and can be expected to lead to artefactual genetic associations [genetic correlation with central retinal arteriolar equivalent: −0.53 (standard error 0.11)]. The significant genetic correlation between SBP and central retinal arteriolar equivalent, −0.53 (standard error 0.22) (after adjusting for age, sex and axial length of the eye), augurs more favourably for the discovery of genetic variants relevant to vascular physiology.

An improved arteriovenous classification method for the early diagnostics of various diseases in retinal image

(BACKGROUND AND OBJECTIVES)

Retinal artery and vein classification is an important task for the automatic computer-aided diagnosis of various eye diseases and systemic diseases. This paper presents an improved supervised artery and vein classification method in retinal image.

(METHODS)

Intra-image regularization and inter-subject normalization is applied to reduce the differences in feature space. Novel features, including first-order and second-order texture features, are utilized to capture the discriminating characteristics of arteries and veins.

(RESULTS)

The proposed method was tested on the DRIVE dataset and achieved an overall accuracy of 0.923.

(CONCLUSION)

This retinal artery and vein classification algorithm serves as a potentially important tool for the early diagnosis of various diseases, including diabetic retinopathy and cardiovascular diseases.

Hypertension and the eye

PURPOSE OF REVIEW

Hypertension is the primary risk factor for cardiovascular disease and mortality that consists a major public health issue worldwide. Hypertension triggers a series of pathophysiological ocular modifications affecting significantly the retinal, choroidal, and optic nerve circulations that result in a range of ocular effects.The retina is the only place in the body where microvasculature can be directly inspected, providing valuable information on hypertension related systemic risks.The aim of this review is to provide an update on latest advances regarding the detection and significance of hypertension related eye signs.

RECENT FINDINGS

It's been shown that measurable retinal microvascular changes may precede progression of systemic microvascular disease.Last years, there are emerging advances in the field retinal imaging and computer software analysis that have enabled the objective and accurate assessment of retinal vascular caliber, while in association with latest epidemiological studies several other retinal vascular features have been recognized, such as vascular length-to-diameter ratio, and wall-to-lumen ratio that may also be associated to hypertension.Additionally, recent genetic studies have provided some insight to vascular pathophysiological processes having correlated new chromosome's loci to hypertensive retinopathy signs.

SUMMARY

Assessment of hypertensive retinopathy signs may convey additional prognostic information on the risk of end-organ damage and may alert for urgent systemic management or even preventive systemic therapies. Further development of retinal vascular imaging and computerized system may provide a significant tool to improve the diagnosis, prognosis, and management of hypertension in clinical practice.

Retinopathy and the risk of cardiovascular disease in patients with chronic kidney disease (from the Chronic Renal Insufficiency Cohort study)

Patients with chronic kidney disease (CKD) experience other diseases such as cardiovascular disease (CVD) and retinopathy. The purpose of this study was to assess whether retinopathy predicts future CVD events in a subgroup of the participants of the Chronic Renal Insufficiency Cohort (CRIC) study. In this ancillary investigation, 2,605 participants of the CRIC study were invited to participate, and nonmydriatic fundus photographs were obtained in 1,936 subjects. Using standard protocols, presence and severity of retinopathy (diabetic, hypertensive, or other) and vessel diameter caliber were assessed at a central photograph reading center by trained graders masked to study participant's information. Patients with a self-reported history of cardiovascular disease were excluded. Incident CVD events were adjudicated using medical records. Kidney function measurements, traditional and nontraditional risk factors, for CVD were obtained. Presence and severity of retinopathy were associated with increased risk of development of any CVD in this population of CKD patients, and these associations persisted after adjustment for traditional risk factors for CVD. We also found a direct relation between increased venular diameter and risk of development of CVD; however, the relation was not statistically significant after adjustment for traditional risk factors. In conclusion, the presence of retinopathy was associated with future CVD events, suggesting that retinovascular pathology may be indicative of macrovascular disease even after adjustment for renal dysfunction and traditional CVD risk factors. Assessment of retinal morphology may be valuable in assessing risk of CVD in patients with CKD, both clinically and in research settings.

Retinal microvessels reflect familial vulnerability to psychotic symptoms: A comparison of twins discordant for psychotic symptoms and controls

Mounting evidence suggests that individuals with schizophrenia have an underlying vulnerability to cardiovascular disease, and a recent study suggested that this vulnerability might be reflected in the retinal microvasculature. The purpose of this study was to test the hypothesis that the retinal microvessels reflect familial vulnerability to psychotic symptoms. Participants were 531 adolescent and young adult twins who took part in the Brisbane Longitudinal Twin Study and the Twins Eye Study in Tasmania. The twins had photographs taken of their retina when they were adolescents or young adults (M age=20.6 years), and retinal vessel diameter was assessed using computer software. The twins completed an assessment of psychosis symptoms approximately six years later. We compared retinal venular diameters of individuals with one or more symptoms of psychosis (n=45), their unaffected co-twins (n=24), and controls (n=462). Individuals with one or more symptoms of psychosis had wider venules (standardized mean=0.29) than controls (standardized mean=-0.04; p=.03), and unaffected co-twins had venular diameters that were intermediate (standardized mean=0.13) between the two groups, suggesting that wide venules may represent a proxy marker of familial vulnerability to psychosis symptoms. Consistent with previous work, there were no differences in arteriolar diameter between individuals with and without symptoms of psychosis. Findings suggest that wide retinal venules may serve as a proxy marker of familial liability to psychosis symptoms. The pathophysiological mechanisms linking psychosis and cardiovascular disease may be operative from early in life, possibly at the level of the microvasculature.

Genetic variation in retinal vascular patterning predicts variation in pial collateral extent and stroke severity

The presence of a native collateral circulation in tissues lessens injury in occlusive vascular diseases. However, differences in genetic background cause wide variation in collateral number and diameter in mice, resulting in large variation in protection. Indirect estimates of collateral perfusion suggest that wide variation also exists in humans. Unfortunately, methods used to obtain these estimates are invasive and not widely available. We sought to determine whether differences in genetic background in mice result in variation in branch patterning of the retinal arterial circulation, and whether these differences predict strain-dependent differences in pial collateral extent and severity of ischemic stroke. Retinal patterning metrics, collateral extent, and infarct volume were obtained for 10 strains known to differ widely in collateral extent. Multivariate regression was conducted, and model performance was assessed using K-fold cross-validation. Twenty-one metrics varied with strain (p<0.01). Ten metrics (e.g., bifurcation angle, lacunarity, optimality) predicted collateral number and diameter across seven regression models, with the best model closely predicting (p<0.0001) number (±1.2-3.4 collaterals, K-fold R2=0.83-0.98), diameter (±1.2-1.9 μm, R2=0.73-0.88), and infarct volume (±5.1 mm3, R2=0.85-0.87). An analogous set of the most predictive metrics, obtained for the middle cerebral artery (MCA) tree in a subset of the above strains, also predicted (p<0.0001) collateral number (±3.3 collaterals, K-fold R2=0.78) and diameter (±1.6 μm, R2=0.86). Thus, differences in arterial branch patterning in the retina and the MCA trees are specified by genetic background and predict variation in collateral extent and stroke severity. If also true in human, and since genetic variation in cerebral collaterals extends to other tissues at least in mice, a similar "retinal predictor index" could serve as a non- or minimally invasive biomarker for collateral extent in brain and other tissues. This could aid prediction of severity of tissue injury in the event of an occlusive event or development of obstructive disease and in patient stratification for treatment options and clinical studies.

Microvascular abnormality in schizophrenia as shown by retinal imaging

OBJECTIVE

Retinal and cerebral microvessels are structurally and functionally homologous, but unlike cerebral microvessels, retinal microvessels can be noninvasively measured in vivo by retinal imaging. The authors tested the hypothesis that individuals with schizophrenia exhibit microvascular abnormality and evaluated the utility of retinal imaging as a tool for schizophrenia research.

METHOD

Participants were members of the Dunedin Study, a population-representative cohort followed from birth with 95% retention. Study members underwent retinal imaging at age 38. The authors assessed retinal arteriolar and venular caliber for all members of the cohort, including individuals who developed schizophrenia.

RESULTS

Study members who developed schizophrenia were distinguished by wider retinal venules, suggesting microvascular abnormality reflective of insufficient brain oxygen supply. Analyses that controlled for confounding health conditions suggested that wider retinal venules are not simply an artifact of co-occurring health problems in schizophrenia patients. Wider venules were also associated with a dimensional measure of adult psychosis symptoms and with psychosis symptoms reported in childhood.

CONCLUSIONS

The findings provide initial support for the hypothesis that individuals with schizophrenia show microvascular abnormality. Moreover, the results suggest that the same vascular mechanisms underlie subthreshold symptoms and clinical disorder and that these associations may begin early in life. These findings highlight the promise of retinal imaging as a tool for understanding the pathogenesis of schizophrenia.

Association between retinopathy and cardiovascular disease in patients with chronic kidney disease (from the Chronic Renal Insufficiency Cohort [CRIC] Study)

Patients with chronic kidney disease experience co-morbid illnesses, including cardiovascular disease (CVD) and retinopathy. The purpose of the present study was to assess the association between retinopathy and self-reported CVD in a subgroup of the participants in the Chronic Renal Insufficiency Cohort study. For this observational, ancillary investigation, 2,605 Chronic Renal Insufficiency Cohort participants were invited to participate in the present study, and nonmydriatic fundus photographs in both eyes were obtained for 1,936 subjects. The photographs were reviewed in a masked fashion at a central photograph reading center. The presence and severity of retinopathy (diabetic, hypertensive, or other) and vessel diameter caliber were assessed using standard protocols by trained graders who were masked to the information about the study participants. A history of self-reported CVD was obtained using a medical history questionnaire. Kidney function measurements and traditional and nontraditional risk factors for CVD were obtained from the Chronic Renal Insufficiency Cohort study. A greater severity of retinopathy was associated with a greater prevalence of any CVD, and this association persisted after adjustment for the traditional risk factors for CVD. The presence of vascular abnormalities usually associated with hypertension was also associated with increased prevalence of CVD. We found a direct relation between CVD prevalence and mean venular caliber. In conclusion, the presence of retinopathy was associated with CVD, suggesting that retinovascular pathology might indicate macrovascular disease, even after adjustment for renal dysfunction and traditional CVD risk factors. This would make the assessment of retinal morphology a valuable tool in CKD studies of CVD outcomes.