Quantitative retinal vascular calibre changes in diabetes and retinopathy: the Singapore Malay eye study

Macular Microvascular Perfusion Status in Hypertensive Patients with Chronic Kidney Disease

To compare retinal microvascular perfusion between the eyes of hypertensive patients with and without chronic kidney disease (CKD), the vessel density (VD) and fractal dimension (FD) of the superficial (SVP) and deep retinal vascular plexus (DVP) were analyzed on 6 × 6 mm fovea-centered optical coherence tomography angiography (OCTA) images of patients with hypertension. The retina was divided into an inner ring (IR) and outer ring (OR) according to the Early Treatment of Diabetic Retinopathy Study grid. The glomerular filtration rate (GFR) was determined and CKD was diagnosed (GFR < 60 mL/min/1.73 m2). Ninety-six eyes from 52 patients with hypertension were included in this analysis. Twenty patients (n = 37 eyes) were diagnosed with CKD. The mean age was 69 ± 11.7 years and 60.4 ± 9.2 years in the CKD group and in the control group, respectively. The univariate model revealed a significant difference in VD between patients without and with CKD in the superficial IR (0.36 ± 0.03 vs. 0.34 ± 0.04, p = 0.03), the superficial OR (0.35 ± 0.02 vs. 0.33 ± 0.04, p = 0.02), the deep OR (0.24 ± 0.01 vs. 0.23 ± 0.02, p = 0.003), and the FD in the SVP (1.87 ± 0.01 vs. 1.86 ± 0.02, p = 0.02) and DVP (1.83 ± 0.01 vs. 1.82 ± 0.01, p = 0.006). After adjusting for age and sex, these differences did not remain statistically significant. Similar results were observed for the FD in the SVP and DVP. In our cohort, patients with hypertension and CKD did not differ from patients without CKD in regard to microvascular perfusion status in the macular area as assessed using OCTA.

Retinal microvascular associations with cardiometabolic risk factors differ by diabetes status: results from the UK Biobank

AIMS/HYPOTHESIS

The aim of the study was to examine the association of retinal vessel morphometry with BP, body composition and biochemistry, and to determine whether these associations differ by diabetes status.

METHODS

The UK Biobank ocular assessment included 68,550 participants aged 40-70 years who underwent non-mydriatic retinal photography, BP and body composition measurements, and haematological analysis. A fully automated image analysis program provided measurements of retinal vessel diameter and tortuosity. The associations between retinal vessel morphology and cardiometabolic risk factors by diabetes status were examined using multilevel linear regression, to provide absolute differences in vessel diameter and percentage differences in tortuosity (allowing for within-person clustering).

RESULTS

A total of 50,233 participants (a reduction from 68,550) were included in these analyses. Overall, those with diabetes had significantly more tortuous venules and wider arteriolar diameters compared with those without. Associations between venular tortuosity and cardiometabolic risk factors differed according to diabetes status (p interaction <0.01) for total fat mass index, HbA_1c, C-reactive protein, white cell count and granulocyte count. For example, a unit rise in white cell count was associated with a 0.18% increase (95% CI 0.05, 0.32%) in venular tortuosity for those without diabetes and a 1.48% increase (95% CI 0.90, 2.07%) among those with diabetes. For arteriolar diameter, significant interactions were evident for systolic BP, diastolic BP, mean arterial pressure (MAP) and LDL-cholesterol. For example, a 10 mmHg rise in systolic BP was associated with a -0.92 μm difference (95% CI -0.96 to -0.88 μm) in arteriolar diameter for those without diabetes, and a -0.58 μm difference (95% CI -0.76 to -0.41 μm) among those with diabetes. No interactions were observed for arteriolar tortuosity or venular diameters.

CONCLUSIONS/INTERPRETATION

We provide clear evidence of the modifying effect of diabetes on cardiometabolic risk factor associations with retinal microvascular architecture. These observations suggest the occurrence of preclinical disease processes, and may be a sign of impaired autoregulation due to hyperglycaemia, which has been suggested to play a pivotal role in the development of diabetes-related microvascular complications.

DATA AVAILABILITY

The data supporting the results reported here are available through the UK Biobank ( https://www.ukbiobank.ac.uk/enable-your-research/apply-for-access ).

Application of the Full-Width-at-Half-Maximum Image Segmentation Method to Analyse Retinal Vascular Changes in Patients with Diabetic Retinopathy

This study used spectral domain optical coherence tomography (SD-OCT) and full-width-at-half-maximum image segmentation to investigate the morphological changes of retinal blood vessels in patients with diabetic retinopathy (DR). Seventy-five patients with type 2 diabetes mellitus (T2DM) without DR and 65 patients with DR were studied. Vascular images of superior temporal region B of the retina were obtained by SD-OCT. The edges of retinal vessels were identified by the full-width-at-half-maximum image segmentation method. The lumen diameter, wall thickness (WT), wall cross-sectional area (WCSA), and wall-to-lumen ratio (WLR) were investigated. We found that, compared with the no diabetic retinopathy (NDR) group, patients in the DR group had an increased retinal arteriolar lumen diameter (RALD), retinal arteriolar outer diameter (RAOD), and WT (128.80 μm versus 104.88 μm; 147.01 μm versus 135.60 μm; 18.29 μm versus 15.26 μm, $P<0.05$ , respectively). The retinal venular lumen diameter (RVLD), retinal venular outer diameter (RVOD), and venular WT in the DR group were also increased (146.17 μm versus 133.66 μm; 180.20 μm versus 156.43 μm; 17.01 μm versus 11.38 μm, $P<0.05$ , respectively). The morphological changes in retinal vessels were significantly correlated with DR stage. In conclusion, in diabetic patients with DR, both retinal arteries and veins are widened and exhibit increased vascular thickness.

Retinal vessel diameters and function in cardiovascular risk and disease

In the last two decades evidence has gradually accumulated suggesting that the eye may be a unique window for cardiovascular risk stratification based on the assessment of subclinical damage of retinal microvascular structure and function. This can be facilitated by non-invasive analysis of static retinal vessel diameters and dynamic recording of flicker light-induced and endothelial function-related dilation of both retinal arterioles and venules. Recent new findings have made retinal microvascular biomarkers strong candidates for clinical implementation as reliable risk predictors. Beyond a review of the current evidence and state of research, the article aims to discuss the methodological benefits and pitfalls and to identify research gaps and future directions. Above all, the potential use for screening and treatment monitoring of cardiovascular disease risk are highlighted. The article provides fundamental comprehension of retinal vessel imaging by explaining anatomical and physiological essentials of the retinal microcirculation leading to a detailed description of the methodological approach. This allows for better understanding of the underlying retinal microvascular pathology associated with the prevalence and development of cardiovascular disease. A body of new evidence is presented on the clinical validity and predictive value of retinal vessel diameters and function for incidence cardiovascular disease and outcome. Findings in children indicate the potential for utility in childhood cardiovascular disease prevention, and the efficacy of exercise interventions highlight the treatment sensitivity of retinal microvascular biomarkers. Finally, coming from the availability of normative data, solutions for diagnostic challenges are discussed and conceptual steps towards clinical implementation are put into perspective.

A stronger association of diabetes mellitus with impaired hyperaemia using a novel ECG-gated device compared with peripheral arterial tonometry

PURPOSE

Impaired digital reactive hyperaemia and flicker-stimulated retinal vascular response are commonly reported risk markers of cardiovascular disease. This is the first study to determine the correlation of these risk markers with diabetes mellitus by comparing our novel flicker-modulated ECG-gated fundoscope with the EndoPAT2000 system.

METHODS

In total, 119 controls and 120 participants with diabetes mellitus partook in this cross-sectional study. The EndoPAT2000 system assessed digital reactive hyperaemia under fasting conditions. A mydriatic ECG-gated fundoscope with a novel flicker module acquired digital retinal images of the left eye before, during and after flicker stimulation. An inhouse semi-automated software measured retinal vessel diameters using a validated protocol with two observers repeating measurements in a subset of 10 controls and 10 participants with diabetes mellitus. Intra- and inter-observer reliability analyses occurred by the interclass correlation coefficient. A receiver operating characteristic curve established associations of variables with diabetes mellitus.

RESULTS

Diabetes mellitus was more strongly associated with flicker-stimulated retinal arteriolar calibre change from baseline (AUC 0.81, 95% CI 0.75-0.87, p < 0.0001) than reactive hyperaemia index. Median flicker-stimulated arteriolar calibre change from baseline (controls: 2.74%, IQR 1.07 vs diabetes mellitus: 1.64%, IQR 1.25, p < 0.0001) and reactive hyperaemia index (controls: 1.87, IQR 0.81 vs diabetes mellitus: 1.60, IQR 0.81, p = 0.003) were lower in diabetes mellitus than controls. Intra- and inter-observer reliability coefficients were high from 0.87 to 0.93.

CONCLUSIONS

Impaired flicker-stimulated retinal arteriolar calibre change from baseline is more highly correlated with diabetes mellitus in this study than a reduced reactive hyperaemia index.

[Retinal vascular network: Changes with aging and systemic vascular disease (cardiac and cerebral)]

For over 10 years, the description of the retinal microvascular network has benefited from the development of new imaging techniques. Automated retinal image analysis software, as well as OCT angiography (OCT-A), are able to highlight subtle, early changes in the retinal vascular network thanks to a large amount of microvascular quantitative data. The challenge of current research is to demonstrate the association between these microvascular changes, the systemic vascular aging process, and cerebrovascular and cardiovascular disease. Indeed, a pathophysiological continuum exists between retinal microvascular changes and systemic vascular diseases. In the Montrachet study, we found that a suboptimal retinal vascular network, as identified by the Singapore I Vessel Assessment (SIVA) software, was significantly associated with treated diabetes and an increased risk of cardiovascular mortality. In addition, we supplemented our research on the retinal vascular network with the use of OCT-A. In the EYE-MI study, we showed the potential role of quantitative characterization of the retinal microvascular network by OCT-A in order to assess the cardiovascular risk profile of patients with a history of myocardial infarction. A high AHA (American Heart Association) risk score was associated with low retinal vascular density independently of hemodynamic changes. Thus, a better understanding of the association between the retinal microvasculature and macrovascular disease might make its use conceivable for early identification of at-risk patients and to suggest a personalized program of preventative care. The retinal vascular network could therefore represent an indicator of systemic vascular disease as well as an interesting predictive biomarker for vascular events.

Retinal arteriolar calibre and venular fractal dimension predict progression of proliferative diabetic retinopathy 6 months after panretinal photocoagulation: a prospective, clinical interventional study

Objective

We examined the hypothesis that baseline retinal vascular geometry in patients with proliferative diabetic retinopathy (PDR) predicts disease activity 6 months after panretinal photocoagulation (PRP).

Methods and analysis

We included 47 eyes from 40 patients with treatment-naïve PDR in a 6-month prospective study. Diagnosis of PDR and disease activity was evaluated by wide-field fluorescein angiography (Optomap, Optos, Dunfermline, Scotland, UK). At baseline and 6-month follow-up, the retinal vessel geometry was measured on optic disc centred images using semiautomated software Vessel Assessment and Measurement Platform for Images of the Retina (VAMPIRE, Dundee, Scotland).

Results

At baseline, mean age and duration of diabetes was 51.6 and 21.4 years, and 62.5% were men. Seventeen eyes (36.2%) had progression of PDR during follow-up. At baseline, we found higher retinal arteriolar calibre (31.3±0.8 vs 28.8±0.8 pixels, p=0.02) and venous fractal dimension (F_D) (1.257±0.011 vs 1.222±0.011, p=0.02) in eyes with progression of PDR as compared with eyes with non-progression. In a multiple logistic regression model, both higher retinal arteriolar calibre (OR 1.34, 95% CI, 1.09 to 1.64, p<0.01) and venular F_D (OR 1.15, 95% CI, 1.04 to 1.27, p<0.01) predicted progression of PDR. Venular calibre was seen to increase from baseline to month six regardless of disease progression (non-progression 45.0±0.7 vs 52.7±1.8 pixels, p<0.01; progression 46.2±0.8 vs 51.0±1.7 pixels, p<0.01).

Conclusion

Our prospective study showed that arteriolar calibre and venular F_D at baseline were predictive of disease activity 6 months after PRP treatment in patients with treatment-naïve PDR.

Correlations between Retinal Arterial Morphometric Parameters and Neurodegeneration in Patients with Type 2 Diabetes Mellitus with No or Mild Diabetic Retinopathy

Background and Objectives: In patients with diabetes mellitus (DM), the neural retina is starting to degenerate before the development of vascular lesions. Our purpose was to investigate the correlation between the retinal arterial morphometric parameters and structural neurodegeneration in patients with type 2 DM with no or mild diabetic retinopathy (DR). Materials and Methods: This is a prospective study including 53 eyes of patients with type 2 DM and 32 eyes of healthy controls. Based on SD-OCT (spectral domain—optical coherence tomography) images, using a micro-densitometry method, we measured the outer and luminal diameter of retinal arteries and calculated the AWT (arterial wall thickness), WLR (wall-to-lumen ratio), and WCSA (wall cross-sectional area). GCL (ganglion cell layer) and RNFL (retinal nerve fiber layer) thickness were analyzed in correlation with the retinal arterial morphometric parameters mentioned above. Results: GCL was thinner in the inner quadrants in the NDR (no DR) group compared to controls (p < 0.05). RAOD (retinal artery outer diameter), RALD (retinal artery lumen diameter), AWT, WLR, and WCSA were similar between groups. A regression model considering age, gender, duration of DM, and HbA1C was carried out. Central GCL thickness was correlated positively with RAOD (coefficient 0.360 per µm, p = 0.011), RALD (coefficient 0.283 per µm, p = 0.050), AWT (coefficient 0.304 per µm, p = 0.029), and WCSA (coefficient 3.90 per µm, p = 0.005). Duration of DM was positively correlated with WCSA (coefficient 0.311 per one year duration of diabetes, p = 0.043). Conclusions: Significant GCL thinning in the inner quadrants preceded the morphological retinal arterial morphometric changes, supporting the neurodegeneration as primary pathogenic mechanism in DR.

Retinal microvascular signs and risk of diabetic kidney disease in asian and white populations

The objective was to examine prospectively the association between retinal microvascular signs and development of diabetic kidney disease (DKD) in Asian and White populations. We analysed two population-based cohorts, composing of 1,221 Asians (SEED) and 703 White (WESDR) adults with diabetes. Retinal microvascular signs at baseline included vascular caliber (arteriolar—CRAE, and venular—CRVE) and diabetic retinopathy (DR). Incident cases of DKD were identified after ~ 6-year. Incident cases were defined based on eGFR in SEED and proteinuria or history of renal dialysis in WESDR. The incidence of DKD were 11.8% in SEED and 14.0% in WESDR. Wider CRAE in SEED (OR = 1.58 [1.02, 2.45]) and wider CRVE (OR = 1.69 [1.02, 2.80)) in WESDR were associated with increased risk of DKD. Presence of DR was associated with an increased risk of DKD in both cohorts (SEED: OR = 1.91 [1.21, 3.01] in SEED, WESDR: OR = 1.99 [1.18, 3.35]). Adding DR and retinal vascular calibers in the model beyond traditional risk factors led to an improvement of predictive performance of DKD risk between 1.1 and 2.4%; and improved classification (NRI 3 between 9%). Microvascular changes in the retina are longitudinally associated with risk of DKD.

A deep-learning system for the assessment of cardiovascular disease risk via the measurement of retinal-vessel calibre

Retinal blood vessels provide information on the risk of cardiovascular disease (CVD). Here, we report the development and validation of deep-learning models for the automated measurement of retinal-vessel calibre in retinal photographs, using diverse multiethnic multicountry datasets that comprise more than 70,000 images. Retinal-vessel calibre measured by the models and by expert human graders showed high agreement, with overall intraclass correlation coefficients of between 0.82 and 0.95. The models performed comparably to or better than expert graders in associations between measurements of retinal-vessel calibre and CVD risk factors, including blood pressure, body-mass index, total cholesterol and glycated-haemoglobin levels. In retrospectively measured prospective datasets from a population-based study, baseline measurements performed by the deep-learning system were associated with incident CVD. Our findings motivate the development of clinically applicable explainable end-to-end deep-learning systems for the prediction of CVD on the basis of the features of retinal vessels in retinal photographs.

Type 2 diabetes and HbA1c are independently associated with wider retinal arterioles: the Maastricht study

AIMS/HYPOTHESIS

Retinal microvascular diameters are biomarkers of cardio-metabolic risk. However, the association of (pre)diabetes with retinal microvascular diameters remains unclear. We aimed to investigate the association of prediabetes (impaired fasting glucose or impaired glucose tolerance) and type 2 diabetes with retinal microvascular diameters in a predominantly white population.

METHODS

In a population-based cohort study with oversampling of type 2 diabetes (N = 2876; n = 1630 normal glucose metabolism [NGM], n = 433 prediabetes and n = 813 type 2 diabetes, 51.2% men, aged 59.8 ± 8.2 years; 98.6% white), we determined retinal microvascular diameters (measurement unit as measured by retinal health information and notification system [RHINO] software) and glucose metabolism status (using OGTT). Associations were assessed with multivariable regression analyses adjusted for age, sex, waist circumference, smoking, systolic blood pressure, lipid profile and the use of lipid-modifying and/or antihypertensive medication.

RESULTS

Multivariable regression analyses showed a significant association for type 2 diabetes but not for prediabetes with arteriolar width (vs NGM; prediabetes: β = 0.62 [95%CI -1.58, 2.83]; type 2 diabetes: 2.89 [0.69, 5.08]; measurement unit); however, there was a linear trend for the arteriolar width across glucose metabolism status (p for trend = 0.013). The association with wider venules was not statistically significant (prediabetes: 2.40 [-1.03, 5.84]; type 2 diabetes: 2.87 [-0.55, 6.29], p for trend = 0.083; measurement unit). Higher HbA_1c levels were associated with wider retinal arterioles (standardised β = 0.043 [95% CI 0.00002, 0.085]; p = 0.050) but the association with wider venules did not reach statistical significance (0.037 [-0.006, 0.080]; p = 0.092) after adjustment for potential confounders.

CONCLUSIONS/INTERPRETATION

Type 2 diabetes, higher levels of HbA_1c and, possibly, prediabetes, are independently associated with wider retinal arterioles in a predominantly white population. These findings indicate that microvascular dysfunction is an early phenomenon in impaired glucose metabolism.

An Automated Grading System for Detection of Vision-Threatening Referable Diabetic Retinopathy on the Basis of Color Fundus Photographs

OBJECTIVE

The goal of this study was to describe the development and validation of an artificial intelligence-based, deep learning algorithm (DLA) for the detection of referable diabetic retinopathy (DR).

RESEARCH DESIGN AND METHODS

A DLA using a convolutional neural network was developed for automated detection of vision-threatening referable DR (preproliferative DR or worse, diabetic macular edema, or both). The DLA was tested by using a set of 106,244 nonstereoscopic retinal images. A panel of ophthalmologists graded DR severity in retinal photographs included in the development and internal validation data sets (n = 71,043); a reference standard grading was assigned once three graders achieved consistent grading outcomes. For external validation, we tested our DLA using 35,201 images of 14,520 eyes (904 eyes with any DR; 401 eyes with vision-threatening referable DR) from population-based cohorts of Malays, Caucasian Australians, and Indigenous Australians.

RESULTS

Among the 71,043 retinal images in the training and validation data sets, 12,329 showed vision-threatening referable DR. In the internal validation data set, the area under the curve (AUC), sensitivity, and specificity of the DLA for vision-threatening referable DR were 0.989, 97.0%, and 91.4%, respectively. Testing against the independent, multiethnic data set achieved an AUC, sensitivity, and specificity of 0.955, 92.5%, and 98.5%, respectively. Among false-positive cases, 85.6% were due to a misclassification of mild or moderate DR. Undetected intraretinal microvascular abnormalities accounted for 77.3% of all false-negative cases.

CONCLUSIONS

This artificial intelligence-based DLA can be used with high accuracy in the detection of vision-threatening referable DR in retinal images. This technology offers potential to increase the efficiency and accessibility of DR screening programs.

Characteristics of the retinal microvasculature in association with cardiovascular risk markers in children with overweight, obesity and morbid obesity

To aim of this study was to evaluate characteristics of the retinal microvasculature, but particularly potential associations with classic and novel (endothelial function and low-grade inflammation)markers for cardiovascular risk, in a cohort of children with overweight and (morbid) obesity. Central retinal arteriolar equivalent(CRAE) and central retinal venular equivalent(CRVE) were assessed. CRAE was significantly lower and AVR significantly higher in children with morbid obesity than in children with overweight and normal weight(p < 0.01). CRVE did not differ significantly between the four weight categories. A multiple linear regression model with CRAE as dependent variable showed that only DBP z-score(β = −2.848,p = 0.029) and plasma glucose concentrations(β = 6.029,p = 0.019) contributed significantly to the variation in CRAE. Remarkably, despite a correlation between CRAE and circulating concentrations of the adhesion molecules VCAM-1 or ICAM-1, markers for inflammation and endothelial function did not contribute to the variation in CRAE. This is the first study showing in population of children with overweight and obesity that the retinal arteriolar microvasculature, but not venular diameter is aberrant, with increasing BMI z-score. CRAE was significantly associated with several cardiovascular risk markers, and multiple linear regression showed that a higher diastolic blood pressure z-score and lower fasting plasma glucose concentrations significantly contributed to the variance in CRAE.

Microvascular Dysfunction and Hyperglycemia: A Vicious Cycle With Widespread Consequences

Microvascular and metabolic physiology are tightly linked. This Perspective reviews evidence that 1) the relationship between hyperglycemia and microvascular dysfunction (MVD) is bidirectional and constitutes a vicious cycle; 2) MVD in diabetes affects many, if not all, organs, which may play a role in diabetes-associated comorbidities such as depression and cognitive impairment; and 3) MVD precedes, and contributes to, hyperglycemia in type 2 diabetes (T2D) through impairment of insulin-mediated glucose disposal and, possibly, insulin secretion. Obesity and adverse early-life exposures are important drivers of MVD. MVD can be improved through weight loss (in obesity) and through exercise. Pharmacological interventions to improve MVD are an active area of investigation.

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

PURPOSE

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.

METHODS

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.

RESULTS

Patients with BCR had smaller retinal venular calibres central retinal venular equivalent (CRVE) than controls (211.3 versus 227.9 μm, 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 213.8 μm, 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.

CONCLUSION

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.

Dietary patterns and retinal vascular calibre in children and adolescents with type 1 diabetes

PURPOSE

To examine the association between dietary patterns and retinal vascular calibre in children and adolescents with type 1 diabetes.

METHODS

A hospital-based cross-sectional study of 83 children and adolescents with type 1 diabetes was conducted over an 8-month period. Dietary patterns were extracted using principal components analysis from completed food frequency questionnaires. Retinal vascular calibre was measured by a trained grader using a standardized protocol and later summarized as central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) using a semi-automated computer program.

RESULTS

Three major dietary patterns were identified as follows: (1) processed foods, (2) plant-based foods and (3) vegetable/fish avoidance pattern. The processed pattern had high component loadings for processed meats and high fat takeaway foods. The plant-based pattern had high component loadings for a number of fruits including, but not limited to, pineapple, grapes oranges and mangos as well as a smaller number of vegetables, including beans and leeks. The vegetable and fish avoidance pattern had high inverse component loadings for canned and fresh fish as well as a number of vegetables including, but not limited to, pumpkin, green beans, broccoli, sweet potato and cabbage. Adjusted regression analysis revealed the 'vegetable/fish avoidance' dietary pattern was associated with a wider CRVE (ExpB = 3.67, 95% CI = 0.11/7.24, p = 0.039). After multivariable adjustments, a vascular risk profile that included: older age, higher BMI, higher systolic blood pressure, greater gestational age, longer screen viewing time, lower maternal education level, lower physical activity levels and lower high-density lipoproteins concentrations were more likely to display narrower CRAE (ExpB = -2.43, 95% CI = -4.92/0.06, p = 0.041).

CONCLUSIONS

This study provides the first evidence for a diet-calibre relationship in children and adolescents with type 1 diabetes. This outcome has potential public health implications, as promotion of healthy eating patterns in children and adolescents might attenuate changes in microvasculature that have been related to an increased risk of microvascular disease, such as retinopathy, in adulthood. Additional studies are warranted to explore and validate this novel finding.

Physical Activity, Sedentary Behaviors, and Retinal Vascular Caliber in Children and Adolescents With Type 1 Diabetes

PURPOSE

The aim of this study was to investigate associations of physical activity and sedentary behaviors with retinal vascular caliber in children and adolescents with type 1 diabetes.

DESIGN

This was a hospital-based cross-sectional study.

METHODS

A study of 122 children and adolescents with type 1 diabetes was conducted over an 8-month period. Self-reported physical activity time and time spent watching TV or playing computer or video games were obtained using interviewer-administered questionnaires. Retinal vascular caliber was measured by a trained grader using a standardized protocol and later summarized as central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) using a semiautomated computer program.

RESULTS

After adjusting for confounders (age, sex, ethnicity, body mass index, systolic blood pressure, HbA1c, maternal smoking status, age at which cow's milk was introduced, and CRVE/CRAE, respectively), narrower CRAE was independently related to more time spent playing computer/video games [ExpB = -3.85; 95% confidence interval (CI), -6.41 to -1.29; P = 0.004], whereas wider CRVE was independently related to lower physical activity level (ExpB = -1.08; 95% CI, -2.01 to -0.15; P = 0.03) and more time spent playing computer/video games (ExpB = 4.72; 95% CI, 0.52-8.92; P = 0.02). Television viewing time was not associated with retinal vascular caliber after adjustment.

CONCLUSIONS

The results of this study suggest that physical activity and sedentary behaviors in the form of "screen viewing time" are associated with retinal vessel caliber early in life. These results suggest that retinal vascular caliber may provide prognostic information beyond current traditional cardiovascular risk factors. Future longitudinal and interventional studies are warranted to evaluate the relevance of these observations.

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

AIMS

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).

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Changes in retinal microvascular diameter in patients with diabetes

BACKGROUND AND OBJECTIVES

Diabetic retinopathy is the main microvascular complication in diabetes mellitus and needs to be diagnosed early to prevent severe sight-threatening retinopathy. The purpose of this study was to quantify the retinal microvasculature pattern and analyze the influence of blood glucose level and the duration of diabetes mellitus on the retinal microvasculature.

METHODS

Two groups were analyzed: patients with diabetes (N=26) and patients without diabetes, ie, controls (N=26). A quantitative semiautomated method analyzed retinal microvasculature. The diameters of arterioles and venules were measured. The total numbers of arterioles and venules were counted. The ratio of arteriole diameter to venule diameter was calculated. The retinal microvasculature pattern was related to clinical and biochemical parameters.

RESULTS

Patients with diabetes exhibited larger venule diameters in the upper temporal quadrant of the retina compared to the lower temporal quadrant (124.85±38.03 µm vs 102.92±15.69 µm; P<0.01). Patients with diabetes for 5 or more years had larger venule diameters in the upper temporal quadrant than patients without diabetes (141.62±44.44 vs 112.58±32.11 µm; P<0.05). The degree of venodilation in the upper temporal quadrant was positively correlated with blood glucose level and the estimated duration of diabetes mellitus.

INTERPRETATION AND CONCLUSION

The employed quantitative method demonstrated that patients with diabetes exhibited venule dilation in the upper temporal quadrant, and the duration of diabetes mellitus was positively correlated with blood glucose level. Therefore, the early assessment of retinal microvascular changes is possible prior to the onset of diabetic retinopathy.

Novel Method for Automated Analysis of Retinal Images: Results in Subjects with Hypertensive Retinopathy and CADASIL

Morphological analysis of the retinal vessels by fundoscopy provides noninvasive means for detecting and staging systemic microvascular damage. However, full exploitation of fundoscopy in clinical settings is limited by paucity of quantitative, objective information obtainable through the observer-driven evaluations currently employed in routine practice. Here, we report on the development of a semiautomated, computer-based method to assess retinal vessel morphology. The method allows simultaneous and operator-independent quantitative assessment of arteriole-to-venule ratio, tortuosity index, and mean fractal dimension. The method was implemented in two conditions known for being associated with retinal vessel changes: hypertensive retinopathy and Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL). The results showed that our approach is effective in detecting and quantifying the retinal vessel abnormalities. Arteriole-to-venule ratio, tortuosity index, and mean fractal dimension were altered in the subjects with hypertensive retinopathy or CADASIL with respect to age- and gender-matched controls. The interrater reliability was excellent for all the three indices (intraclass correlation coefficient ≥ 85%). The method represents simple and highly reproducible means for discriminating pathological conditions characterized by morphological changes of retinal vessels. The advantages of our method include simultaneous and operator-independent assessment of different parameters and improved reliability of the measurements.

The clinical implications of recent studies on the structure and function of the retinal microvasculature in diabetes

The retinal blood vessels provide the opportunity to study early structural and functional changes in the microvasculature prior to clinically significant microvascular and macrovascular complications of diabetes. Advances in digital retinal photography and computerised assessment of the retinal vasculature have provided more objective and precise measurements of retinal vascular changes. Clinic- and population-based studies have reported that these quantitatively measured retinal vascular changes (e.g. retinal arteriolar narrowing and venular widening) are associated with preclinical structural changes in other microvascular systems (e.g. infarct in the cerebral microcirculation), as well as diabetes and diabetic complications, suggesting that they are markers of early microvascular dysfunction. In addition, there are new retinal imaging techniques to further assess alterations in retinal vascular function (e.g. flicker-induced vasodilatory response, blood flow and oxygen saturation) in diabetes and complications that result from the effects of chronic hyperglycaemia, inflammation and endothelial dysfunction. In this review, we summarise the latest findings on the relationships between quantitatively measured structural and functional retinal vascular changes with diabetes and diabetic complications. We also discuss clinical implications and future research to evaluate whether detection of retinal vascular changes has additional value beyond that achieved with methods currently used to stratify the risk of diabetes and its complications.

The association between retinal vascular geometry changes and diabetic retinopathy and their role in prediction of progression--an exploratory study

Background

The study describes the relationship of retinal vascular geometry (RVG) to severity of diabetic retinopathy (DR), and its predictive role for subsequent development of proliferative diabetic retinopathy (PDR).

Methods

The research project comprises of two stages. Firstly, a comparative study of diabetic patients with different grades of DR. (No DR: Minimal non-proliferative DR: Severe non-proliferative DR: PDR) (10:10: 12: 19). Analysed RVG features including vascular widths and branching angles were compared between patient cohorts. A preliminary statistical model for determination of the retinopathy grade of patients, using these features, is presented. Secondly, in a longitudinal predictive study, RVG features were analysed for diabetic patients with progressive DR over 7 years. RVG at baseline was examined to determine risk for subsequent PDR development.

Results

In the comparative study, increased DR severity was associated with gradual vascular dilatation (p = 0.000), and widening of the bifurcating angle (p = 0.000) with increase in smaller-child-vessel branching angle (p = 0.027). Type 2 diabetes and increased diabetes duration were associated with increased vascular width (p = <0.05 In the predictive study, at baseline, reduced small-child vascular width (OR = 0.73 (95% CI 0.58-0.92)), was predictive of future progression to PDR.

Conclusions

The study findings suggest that RVG alterations can act as novel markers indicative of progression of DR severity and establishment of PDR. RVG may also have a potential predictive role in determining the risk of future retinopathy progression.

Diabetes, Diabetic Retinopathy, and Retinal Vascular Alterations: A Systematic Review

The aim of this review is to summarize the available findings from previous research that has focused on retinal vascular caliber characteristics in diabetes and diabetic retinopathy and identify any gaps that exist in the current literature. A systematic Medline, EMBASE, and PubMed search of relevant articles was conducted with coverage up to the 30th of September, 2012. The search was not restricted by language but was limited to studies conducted in humans. The majority of articles conducted on children and adolescents with type 1 diabetes have reported that arterioles with larger caliber were present in the early stages of diabetic retinopathy (n = 5). Only a few studies conducted on older individuals with type 1 diabetes (n = 2) suggest that smaller retinal arteriolar caliber is associated with increased severity of diabetic retinopathy. Much stronger trends have been identified between venular caliber and older individuals with diabetes, with the vast majority of studies reporting that retinal venular dilation represents a later sign of severe diabetic retinopathy (n = 6), with only 1 study highlighting associations with incident diabetes (n = 1). Significant developments have occurred to better understand the relationship between retinal vascular caliber and the onset and progression of diabetes and diabetic retinopathy. Recent evidence suggests that retinal arteriolar dilation may be a possible risk factor in the early development diabetic retinopathy and retinal venules are dilated in persons with severe diabetic retinopathy. Despite this, the clinical significance of these findings requires further evaluation.

Kidney and eye diseases: common risk factors, etiological mechanisms, and pathways

Chronic kidney disease is an emerging health problem worldwide. The eye shares striking structural, developmental, and genetic pathways with the kidney, suggesting that kidney disease and ocular disease may be closely linked. A growing number of studies have found associations of chronic kidney disease with age-related macular degeneration, diabetic retinopathy, glaucoma, and cataract. In addition, retinal microvascular parameters have been shown to be predictive of chronic kidney disease. Chronic kidney disease shares common vascular risk factors including diabetes, hypertension, smoking, and obesity, and pathogenetic mechanisms including inflammation, oxidative stress, endothelial dysfunction, and microvascular dysfunction, with ocular diseases supporting the 'Common Soil Hypothesis.' In this review, we present major epidemiological evidence for these associations and explore underlying pathogenic mechanisms and common risk factors for kidney and ocular disease. Understanding the link between kidney and ocular disease can lead to the development of new treatment and screening strategies for both diseases.

Association between retinal venular dilation and serous retinal detachment in diabetic macular edema

PURPOSE

To study the relationship between retinal vessel diameter and qualitative and quantitative evaluations on spectral-domain optical coherence tomography in patients with diabetic macular edema.

METHODS

One hundred and eight consecutive eyes of 80 patients, with clinically significant macular edema underwent optical coherence tomography and color fundus photography. The authors evaluated the retinal thickness of the Early Treatment Diabetic Retinopathy Study grid and foveal pathomorphologies including cystoid macular edema and serous retinal detachment on the optical coherence tomography images. The diameters of the superotemporal or inferotemporal retinal vessels originating from the optic disk were measured using a computer-assisted technique.

RESULTS

The mean diameters of the superotemporal and inferotemporal venules were larger in eyes with diabetic macular edema than in healthy eyes. The mean diameter of the temporal venules but not the arterioles was associated with perifoveal thickening in the inferior subfield in eyes with diabetic macular edema (P = 0.014). Although the retinal thickening in the central subfield was not correlated with the diameters of the retinal vessels, eyes with foveal serous retinal detachment had larger mean diameters of superotemporal and inferotemporal venules than those without serous retinal detachment (P < 0.001).

CONCLUSION

The mean diameters of the superotemporal and inferotemporal venules were significantly associated with foveal serous retinal detachment in diabetic macular edema.

Determinants of retinal venular diameter: the Beaver Dam Eye Study

OBJECTIVE

To describe how retinal venular diameter changes over time for an individual and to examine differences in these changes among people with different risk profiles.

DESIGN

Population-based cohort study.

PARTICIPANTS

A total of 4600 persons aged 43 to 86 years from the Beaver Dam Eye Study (BDES) who participated in at least 1 examination and had venular diameter measured in the right eye.

METHODS

Data from 4 examinations during a 15-year period were analyzed. Retinal venular diameter was measured from photographs at each examination by computer-assisted methods and summarized as the central retinal venular equivalent (CRVE). Associations of risk factors with concurrent CRVE measurements and changes in CRVE over time were determined using multivariate analyses.

MAIN OUTCOME MEASURES

Central retinal venular equivalent.

RESULTS

The CRVE tended to narrow with age. Mean CRVE was approximately 5 μm smaller (225 vs. 230 μm) for the average 70-year-old compared with the average 50-year-old, and was approximately 13 μm smaller (217 vs. 230 μm) for the average 85-year-old compared with the average 50-year-old. Male sex (beta estimate [β] = 5.24; 95% confidence interval [CI], 3.58-6.90), history of current cigarette smoking (β = 9.38; 95% CI, 8.26-10.49), and higher white blood cell (WBC) count (per 1000/μL: β = 0.95; 95% CI, 0.74-1.16) were independently associated with larger concurrent CRVE, whereas higher mean arterial blood pressure (per 5 mmHg: β = -0.36; 95% CI, -0.50 to -0.23) and higher serum high-density lipoprotein (HDL) cholesterol (per 10 mg/dl: β = 0.89; 95% CI, -1.15 to -0.63) were independently associated with smaller concurrent CRVE. History of cardiovascular disease (CVD) (β = -0.16; 95% CI, -0.26 to -0.06) and presence of chronic kidney disease (CKD) (β = -0.20; 95% CI, -0.34 to -0.05) were associated with a greater decrease in CRVE over time.

CONCLUSIONS

These data show that retinal venular diameter tends to narrow with age; concurrent venular diameter is independently associated with sex, blood pressure, serum HDL cholesterol, WBC count, and history of current cigarette smoking; and change in CRVE is independently associated with a history of CVD and presence of CKD. The different independent effects of these interrelated factors on CRVE highlight the complex relationship between CRVE and systemic diseases and conditions and the difficulty in determining specific causes of change in CRVE over time.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Retinal vascular geometry in Asian persons with diabetes and retinopathy

PURPOSE

Our purpose was to examine the relationship of retinal vascular parameters with diabetes and retinopathy in an older Asian population.

METHODS

Retinal photographs from participants of a population-based survey of Asian Malay persons aged 40-80 years were analyzed. Specific retinal vascular parameters (tortuosity, branching angle, fractal dimension, and caliber) were measured using a semiautomated computer-based program. Diabetes was defined as random plasma glucose ≥ 11.1 mmol/liter, the use of diabetes medication, or physician-diagnosed diabetes. Retinopathy signs were graded from photographs using the modified Airlie House classification system.

RESULTS

A total of 2735 persons were included in the study. Persons with diabetes (n = 594) were more likely to have straighter (less tortuous) arterioles and wider arteriolar and venular caliber than those without diabetes (n = 2141). Among subjects with diabetes, those with retinopathy had wider venular caliber than those without retinopathy (211.3 versus 204.9 mm, p = .001). Among nondiabetic subjects, however, those with retinopathy had more tortuous venules than those without retinopathy [5.19(×10(4)) versus 4.27(×10(4)), p < .001].

CONCLUSIONS

Retinal vascular parameters varied by diabetes and retinopathy status in this older Asian cohort. Our findings suggest that subtle alterations in retinal vascular architecture are influenced by diabetes.

Differential association of retinal arteriolar and venular caliber with diabetes and retinopathy

AIMS

To describe the relationship of retinal arteriolar and venular caliber with diabetes, retinopathy and hyperglycemia, in an Asian Indian population.

METHODS

This was a population-based cross-sectional study of 3400 (75.6% response rate) Singapore ethnic Indians aged 40-80 years. Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were obtained using a validated computer-assisted program. Diabetes mellitus was identified using standardized criteria. Diabetic retinopathy was graded based on the modified Airlie House Classification System.

RESULTS

There were 980 (32.2%) participants with diabetes. Of these, 327 (33.4%) had diabetic retinopathy. After multivariate adjustment, diabetic persons had a wider CRAE (145.23μm vs 142.38μm, P<0.001). This relationship was stronger in persons without hyperlipidemia (P-interaction<0.1). Among diabetic participants, wider CRVE was related to increasing severity of retinopathy (P for trend<0.05) and this association may be altered by hypertensive status. Retinal arteriolar caliber widened with increasing glucose (P<0.001) and HbA1C (P<0.001) levels.

CONCLUSIONS

In Indian adults, wider retinal arteriolar caliber is associated with diabetes and hyperglycemia, while wider retinal venular caliber is associated with diabetic retinopathy. This is consistent with white populations and confirms the differential systemic association of retinal vascular caliber in Asian Indians.

Diabetic retinopathy

Diabetic retinopathy is a common and specific microvascular complication of diabetes, and remains the leading cause of preventable blindness in working-aged people. It is identified in a third of people with diabetes and associated with increased risk of life-threatening systemic vascular complications, including stroke, coronary heart disease, and heart failure. Optimum control of blood glucose, blood pressure, and possibly blood lipids remains the foundation for reduction of risk of retinopathy development and progression. Timely laser therapy is effective for preservation of sight in proliferative retinopathy and macular oedema, but its ability to reverse visual loss is poor. Vitrectomy surgery might occasionally be needed for advanced retinopathy. New therapies, such as intraocular injection of steroids and antivascular endothelial growth-factor agents, are less destructive to the retina than are older therapies, and could be useful in patients who respond poorly to conventional therapy. The outlook for future treatment modalities, such as inhibition of other angiogenic factors, regenerative therapy, and topical therapy, is promising.

Are myopic eyes less likely to have diabetic retinopathy?

PURPOSE

Eyes with myopia may be less likely to develop diabetic retinopathy (DR). The relationship between refractive error, ocular biometry, and DR therefore was investigated.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Persons with diabetes from the Singapore Malay Eye Study (SiMES).

METHODS

Diabetes mellitus was defined as random glucose of 11.1 mmol/l or more, use of diabetic medication, or a physician diagnosis of diabetes. Spherical equivalent refraction (SE) was assessed using an autokeratorefractometer and subjective refraction. Axial length (AL) and anterior chamber depth (ACD) were measured by IOLMaster (Carl Zeiss Meditec AG, Jena, Germany). Diabetic retinopathy was graded from retinal photographs.

MAIN OUTCOME MEASURES

Any DR was defined by characteristic lesions defined by the Early Treatment Diabetic Retinopathy Study (ETDRS); moderate DR by ETDRS retinopathy severity scores of 43 or higher; and vision-threatening retinopathy by severe nonproliferative retinopathy, proliferative DR, or clinically significant macular edema.

RESULTS

Of 3280 adult Malay participants (78.7% response), 629 persons with diabetes contributed to this analysis. In multivariate analyses adjusting for age, gender, education, height, cataract, hypertension, hemoglobin A1c, and other factors, eyes with myopic SE were less likely to have any DR (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.84-0.96; P = 0.002, per 1-diopter [D] decrease), moderate DR (OR, 0.83; 95% CI, 0.73-0.93; P = 0.001, per 1-D decrease), and vision-threatening DR (OR, 0.77; 95% CI, 0.67-0.88; P<0.001, per 1-D decrease). Eyes with longer AL were less likely to have any DR (OR, 0.86; 95% CI, 0.75-0.99; P = 0.041, per 1-mm increase), moderate DR (OR, 0.80; 95% CI, 0.62-1.05; P = 0.11, per 1-mm increase), and vision-threatening DR (OR, 0.63; 95% CI, 0.40-0.99; P = 0.044, per mm increase). Eyes with deeper ACD were less likely to have moderate DR (OR, 0.32; 95% CI, 0.16-0.64; P = 0.001, per 1-mm increase) and vision-threatening DR (OR, 0.14; 95% CI, 0.06-0.36; P = 0.001, per 1-mm increase).

CONCLUSIONS

Myopic refraction and longer AL are associated with a lower risk of DR, particularly vision-threatening retinopathy, without any evidence of a threshold.

Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians

PURPOSE

Current knowledge of ethnic variability in the epidemiology of major eye diseases in Asia is limited. This report summarizes the rationale and study design of the Singapore Indian Chinese Cohort (SICC) Eye Study, a population-based study of ethnic South Asian (Indians) and East Asian (Chinese) older adults in Singapore.

METHODS

The SICC examined a population-based cross-sectional sample of 3,300 ethnic Indians and 3,300 ethnic Chinese aged 40-80+ years residing in the South-Western part of Singapore.

RESULTS

From two lists of 12,000 names of each ethnic group provided by the Ministry of Home Affairs, age-stratified random sampling was used to select 6,350 names in each group, with a target sample size of 3,300. Invitations were sent to attend a central clinic using letters, telephone calls and home visits. Examination procedures included interviews, measurement of blood pressure, anthropometry, presenting and best-corrected visual acuity, subjective refraction, ocular biometry, Goldmann applanation tonometry, slit-lamp biomicroscopy, optic disc imaging and digital photography of the lens and retina, using a standardized protocol. Selected participants underwent gonioscopic examination, visual field testing, and anterior and posterior segment optical coherence tomography. Blood, tear, and urine samples were collected for biochemical analyses, and stored for genetic and proteomic studies.

CONCLUSIONS

In conjunction with the Singapore Malay Eye Study, the SICC study will permit an in-depth evaluation of the prevalence, risk factors, and impact of major eye diseases in Chinese, Indians and Malays, three distinct Asian ethnic groups, whose combined numbers represent half the world's population.