Retinal arteriolar dilation predicts retinopathy in adolescents with type 1 diabetes

Three-Year Follow-Up Study Investigating Changes in Retinal Vascular Morphology and the Relationship with Diabetic Retinopathy in Children with Type 1 Diabetes Mellitus

INTRODUCTION

This study aimed to investigate changes in retinal microvascular morphology and associated factors, and their relationship with diabetic retinopathy (DR) in children with type 1 diabetes mellitus (T1DM).

METHODS

Thirty-eight children enrolled in this 3-year follow-up study underwent complete ophthalmic examinations including fundus photography. Retinal vascular parameters were measured automatically and compared between baseline and follow-up. Multiple linear regression was used to investigate factors affecting changes in vascular parameters. Binary logistic regression was used to analyze the relationship between retinal microvascular morphology and DR.

RESULTS

The caliber of all retinal vessels (within 1-1.5 papillary diameter [PD] from the center of the optic disc, p = 0.030; 1.5-2 PD, p = 0.003), arterioles, and venules (1.5-2 PD, p = 0.001) was narrower in nearly all regions in the follow-up group compared with the baseline group. Vascular tortuosity increased in the central part of the retina and decreased in the periphery. The density (1-1.5 PD, p = 0.030) and fractal dimension (p = 0.037) of retinal vessels were increased at the end of the follow-up compared with baseline. Retinal vascular caliber was independently correlated with DR (odds ratio 0.793 [95% confidence interval 0.633-0.993]; p = 0.044).

CONCLUSION

Retinal microvascular morphology in children with T1DM varied with the disease course. Narrower retinal vessels may be an independent risk factor for DR. Results of this study emphasized the importance of regular follow-up of fundus vascular morphology for the detection of early DR in children with T1DM.

Review and comparison of retinal vessel calibre and geometry software and their application to diabetes, cardiovascular disease, and dementia

Developments in retinal imaging technologies have enabled the quantitative evaluation of the retinal vasculature. Changes in retinal calibre and/or geometry have been reported in systemic vascular diseases, including diabetes mellitus (DM), cardiovascular disease (CVD), and more recently in neurodegenerative diseases, such as dementia. Several retinal vessel analysis softwares exist, some being disease-specific, others for a broader context. In the research setting, retinal vasculature analysis using semi-automated software has identified associations between retinal vessel calibre and geometry and the presence of or risk of DM and its chronic complications, and of CVD and dementia, including in the general population. In this article, we review and compare the most widely used semi-automated retinal vessel analysis softwares and their associations with ocular imaging findings in common systemic diseases, including DM and its chronic complications, CVD, and dementia. We also provide original data comparing retinal calibre grading in people with Type 1 DM using two softwares, with good concordance.

Retinal microvasculature and risk of spontaneous abortion in multiethnic Southeast Asian women

OBJECTIVE

To better understand the underlying pathogenesis of spontaneous abortion that affects 10%-20% of recognized pregnancies. We used retinal imaging to study the role of systemic microvasculature and the risk of spontaneous abortion.

DESIGN

A prospective multiethnic preconception cohort study conducted in Singapore.

SETTING

Hospital-based.

PATIENT(S)

A total of 1,032 Southeast Asian women who intended to conceive naturally were screened at study entry, among which 480 women spontaneously conceived within the 12-month observation period. After excluding 24 women who were lost to follow-up, we calculated the spontaneous abortion rate among 456 women. Further, we included 379 women for the final association analysis because 63 women did not undergo preconception retinal imaging examination and 14 had other types of pregnancy loss instead of spontaneous abortion.

INTERVENTION(S)

Trained photographers performed retinal examination using a 45-degree nonmydriatic retinal camera at study entry during the preconception screening. Using a semiautomated, computer-based program, we assessed quantitative retinal microvascular measurements, including caliber, fractal dimension, curvature tortuosity, and branching angle. Clinical research coordinators collected information on sociodemographic status, menstrual characteristics, and lifestyle, and assessed blood pressure and anthropometry at study entry.

MAIN OUTCOME MEASURE(S)

We performed a modified Poisson regression model to estimate the relative risk (RR) and 95% confidence interval (CI) for each retinal microvascular feature and its association with spontaneous abortion after adjusting for major confounders such as maternal prepregnancy, body mass index, and previous pregnancy loss history.

RESULT(S)

We reported a spontaneous abortion rate of 13.4% (61 out of 456). Among all retinal microvascular features, retinal arteriolar caliber, retinal arteriolar, and venular curvature tortuosity were associated with a high risk of incident spontaneous abortion. In the regression model, per SD increase in retinal curvature tortuosity was associated with a 25%-34% increased risk of incident spontaneous abortion (arteriolar: unadjusted RR, 1.29 [95% CI, 1.06-1.56] and adjusted RR, 1.26 [1.04-1.53]; venule: unadjusted RR, 1.30 [1.08-1.55] and adjusted RR, 1.34 [1.09-1.64]).

CONCLUSION(S)

Our prospective cohort observed an increased risk of spontaneous abortion among Asian women with more tortuous retinal vessels assessed during the preconception phase. Our results indicate a role of vascular inflammatory and oxidative stress in the pathogenesis of spontaneous abortion.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, NCT03531658.

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.

Fenofibrate, which reduces risk of sight-threatening diabetic retinopathy in type 2 diabetes, is associated with early narrowing of retinal venules: a FIELD trial substudy

Retinal vessel calibre metrics were evaluated at baseline and 2 years in a FIELD substudy (n = 208). Central retinal venule calibre was significantly reduced by fenofibrate and unchanged by placebo. Arteriole metrics did not change. Larger studies relating retinal vessel calibre to future diabetes complications and response to therapy are merited.

Retinal neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy

In diabetes mellitus (DM) patients retinal complications were typically considered part of a vascular process. Recent research suggests that retinal degeneration in DM might also be caused by a neuropathy that could precede microvascular alterations. The present work reviews the currently available bibliography about neurodegeneration in patients with type 2 DM (DM2) without diabetic retinopathy (DR). In patients with non-severe, early DM2 without DR and good metabolic control visual function parameters show early abnormalities that precede clinical DR (in which we diagnose with a conventional ophthalmological examination). Using optical coherence tomography (OCT) technology, a reduction in macular and peripapillary thickness has been observed in different studies. Recent researches suggest that systemic complications (especially ischaemia) and a possible microvascular alteration eventually contributes to retinal neurodegeneration, which opens the door to new studies that include new techniques for evaluating the microvascularization of the retinal layers.

The application of arterio-venous ratio (AVR) cut-off values in clinic to stratify cardiovascular risk in patients

INTRODUCTION

Cardiovascular risk calculators are a useful tool for identifying at-risk individuals. There are standardised methods for assessing the retinal microcirculation which alters as a consequence of cardiovascular disease (CVD). This study aimed to explore if a standardised retinal vessel assessment conducted in primary optometric care reflects current cardiovascular risk, as measured using two validated CVD risk calculators (QRISK 2; Mayo Clinic).

METHODS

A total of 120 subjects were included in the analyses. Following a routine eye examination, participants had disc-centred retinal photographs and systemic blood pressure taken. Retinal vessel parameters (central retinal artery and vein equivalent and arterio-venous ratio (AVR)) were calculated using semi-automated software. Participants were then grouped into AVR quintiles as defined by the Atherosclerosis Risk in Communities Study (ARIC). Cardiovascular risk was calculated with the validated QRISK and Mayo Clinic health calculators.

RESULTS

Systolic blood pressure was significantly greater in those with an AVR value falling in the lowest quintile compared to the highest quintile (150.65 mmHg vs. 132.21 mmHg [p = 0.001]). Similarly, CVD risk was significantly higher in those with the lowest AVR compared to the highest (QRISK: 14.28% vs. 9.87% [p = 0.05]; MAYO risk: 36.35% vs. 19.21% [p = 0.01]). Chi squared analyses showed a significant difference in the number of hypertensives in the lowest AVR quintile compared to those in the highest [p = 0.02].

CONCLUSION

Whilst the ARIC population is not directly comparable to the population used to develop the QRISK calculator, it has been shown that its application could help to identify at risk individuals using retinal vessel analyses.

Baseline extended zone retinal vascular calibres associate with sensory nerve abnormalities in adolescents with type 1 diabetes: A prospective longitudinal study

OBJECTIVE

The relationship between retinal vascular calibres (RVCs) and diabetic neuropathy is unclear. We investigated associations between RVCs and sensory nerve abnormality in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

In a prospective longitudinal study of 889 adolescents with type 1 diabetes with baseline mean (±SD) age 14.1 ± 1.5 years and HbA_1c IFCC 69.4 ± 14.1 mmol/mol (8.6 ± 1.3%), RVCs were assessed from baseline retinal photographs: 'central zone' calibres, summarized as central retinal arteriolar (CRAE) and venular equivalents (CRVE) and 'extended zone' calibres: mean width of arterioles (MWa) and venules (MWv). Sensory nerve abnormality was defined as at least one abnormal sensory quantitative testing from two thermal and two vibration threshold tests measured at foot every 1-2 years. Associations between baseline RVC and sensory nerve function were examined using generalized estimating equations and cumulative risk by Cox regression analyses.

RESULTS

During a median study follow-up of 6.2 [IQR 3.7-10.4] years, sensory nerve abnormality was found in 27% of adolescents. Narrower extended zone calibre quartiles but not CRAE or CRVE quartiles were independently associated with sensory nerve abnormality: MWa (Q1 vs. Q2-4: OR 1.35 (95% CI 1.02, 1.61) and MWv (Q1 vs. Q2-4: 1.31 (1.03, 1.7)), after adjusting for HbA_1c , duration and blood pressure. Similarly, in Cox regression, the narrowest quartiles were associated with sensory nerve abnormality: MWa hazard ratio (HR) 1.5 (1.3, 1.8) and MWv 1.6 (1.4, 1.9).

CONCLUSIONS

Narrower extended zone retinal calibres were associated with sensory nerve abnormality in adolescents with type 1 diabetes and may present useful biomarkers to understand the pathophysiology of neuropathy.

Update in the epidemiology, risk factors, screening, and treatment of diabetic retinopathy

Despite progress in the treatment of diabetic macular edema and diabetic retinopathy, the rate of lower fundus examination due to limitations of medical resources delays the diagnosis and treatment of diabetic retinopathy. Therefore, implementation of automated diabetic retinopathy screening program and the identification of more specific and sensitive biomarkers are important for facilitating the earlier detection of diabetic macular edema and diabetic retinopathy to decrease the prevalence of poor vision and blindness.

Imaging the eye and its relevance to diabetes care

Diabetes is a major cause of vision loss globally, yet this devastating complication is largely preventable. Early detection and treatment of diabetic retinopathy necessitates screening. Ocular imaging is widely used clinically, both for the screening and management of diabetic retinopathy. Common eye conditions, such as glaucoma, cataracts and retinal vessel thrombosis, and signs of systemic conditions, such as hypertension, are frequently revealed. As well as imaging by a skilled clinician during an eye examination, non-ophthalmic clinicians, such as general practitioners, endocrinologists, nurses and trained health workers, can also can carry out diabetic eye screening. This process usually comprises local imaging with remote grading, mostly human grading. However, grading incorporating artificial intelligence is emerging. In a clinical research context, retinal vasculature analyses using semi-automated software in many populations have identified associations between retinal vessel geometry, such as vessel caliber, and the risk of diabetic retinopathy and other chronic complications of type 1 and type 2 diabetes. Similarly, evaluation of corneal nerves by corneal confocal microscopy is revealing diabetes-related abnormalities, and associations with and predictive power for other chronic diabetes complications. As yet, the value of retinal vessel geometry and corneal confocal microscopy measures at an individual level is uncertain. In this article, targeting non-ocular clinicians and researchers, we review existent and emerging ocular imaging and grading tools, including artificial intelligence, and their associations between ocular imaging findings and diabetes and its chronic complications.

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.

Retinal Vascular Caliber Association with Nonperfusion and Diabetic Retinopathy Severity Depends on Vascular Caliber Measurement Location

PURPOSE

To evaluate the association of retinal nonperfusion and diabetic retinopathy (DR) severity with location of vascular caliber measurement using ultrawide field (UWF) imaging.

DESIGN

Retrospective image review.

PARTICIPANTS

Adults with diabetes mellitus.

METHODS

All images from subjects with same-day UWF fluorescein angiography (FA) and color imaging were evaluated. Predominantly peripheral lesions (PPL) and DR severity were graded from UWF color images. Nonperfusion was quantified using UWF-FA in defined retinal regions [posterior pole (PP), mid-periphery (MP), far-periphery (FP)]. Retinal vessel calibers were measured at an optic disc centered inner and outer zone.

MAIN OUTCOME MEASURES

Nonperfusion index (NPI) in the PP, MP and FP. Mean arteriole and venule diameter in the inner and outer zones.

RESULTS

Two hundred eighty-five eyes of 193 patients (24.9% mild nonproliferative DR [NPDR], 22.8% moderate NPDR, 37.5% severe NPDR and 14.7% proliferative DR [PDR]) were reviewed. No significant associations between inner zone arteriolar diameter and retinal NPI overall or in any retinal region. In the outer zone, eyes with thinnest arteriolar calibers (quartile 1) were associated with a 1.7- to 2.4-fold nonperfusion increase across all retinal regions compared to the remaining eyes (P = 0.002 [PP] to 0.048 [FP]). In the outer zone, the percentage of eyes in the thinnest quartile of retinal arteriolar diameter increased with worsening DR severity (mild NPDR: 10% vs PDR: 31%, P = 0.007). This association was not observed when measured within the inner zone (P = 0.129). All venular caliber associations were not statistically significant when corrected for potentially confounding factors. Thinner outer zone retinal arteriolar caliber (quartile 1) was more common in eyes with PPL compared to eyes without PPL (34.1% vs 20.8%, P = 0.017) as were thicker outer venular calibers (quartile 4) (33% vs 21.3%, P = 0.036). Presence of PPL was associated with thinner outer zone arteriolar caliber (109.7 ± 26.5μm vs 123.0 ± 29.5μm, P = 0.001).

CONCLUSIONS

The association of vascular caliber with nonperfusion and DR severity differs based upon the retinal location at which vascular caliber is measured. Peripheral arterial narrowing is associated with increasing nonperfusion, worsening DR severity and presence of PPL. In contrast, inner zone retinal arteriolar caliber is not associated with these findings.

Blended Multi-Modal Deep ConvNet Features for Diabetic Retinopathy Severity Prediction

Diabetic Retinopathy (DR) is one of the major causes of visual impairment and blindness across the world. It is usually found in patients who suffer from diabetes for a long period. The major focus of this work is to derive optimal representation of retinal images that further helps to improve the performance of DR recognition models. To extract optimal representation, features extracted from multiple pre-trained ConvNet models are blended using proposed multi-modal fusion module. These final representations are used to train a Deep Neural Network (DNN) used for DR identification and severity level prediction. As each ConvNet extracts different features, fusing them using 1D pooling and cross pooling leads to better representation than using features extracted from a single ConvNet. Experimental studies on benchmark Kaggle APTOS 2019 contest dataset reveals that the model trained on proposed blended feature representations is superior to the existing methods. In addition, we notice that cross average pooling based fusion of features from Xception and VGG16 is the most appropriate for DR recognition. With the proposed model, we achieve an accuracy of 97.41%, and a kappa statistic of 94.82 for DR identification and an accuracy of 81.7% and a kappa statistic of 71.1% for severity level prediction. Another interesting observation is that DNN with dropout at input layer converges more quickly when trained using blended features, compared to the same model trained using uni-modal deep features.

Associations between cannabis use and retinal vessel diameter in young adults

Cannabis appears to have vascular effects that may have implications for cerebrovascular function, but no studies have directly visualized the microvasculature in living cannabis users. The current study used retinal imaging, a tool taken from ophthalmology, to visualize the small retinal microvessels in cannabis users. We compared retinal arteriolar (small arteries) and venular (small veins) diameters in 55 frequent cannabis users and 51 comparison individuals with a mean age of 19.25 years (SD = 2.43). Results indicated that mean arteriolar diameter was statistically significantly wider for cannabis users (M = 157.98, SE = 1.42) than for comparison individuals (M = 153.56, SE = 1.46; F(1,103) = 4.67, p = .033), even after controlling for a variety of covariates and after excluding from analyses cannabis users who had used cannabis in the past 24 h. There was no statistically significant difference in retinal venular diameter between cannabis users and comparison individuals. Findings suggest that frequent cannabis use is associated with wider retinal arterioles, which might represent a residual vasodilatory effect of recent cannabis use or impaired autoregulation resulting from chronic cannabis use. Retinal imaging is a non-invasive, cost-effective tool for visualizing the microvasculature in living individuals and can be combined, in future research, with neuroimaging and other measures of retinal vascular function to better understand the acute and longer-term effects of cannabis use on the microvasculature.

Ability of Swept source OCT technology to detect neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy

PURPOSE

To evaluate neurodegeneration in patients with type 2 Diabetes Mellitus (DM2) without diabetic retinopathy, and to assess the possible role of chronic systemic ischaemia and disease duration in retinal changes.

STUDY DESIGN

Observational cross sectional study.

METHODS

Sixty eyes of 60 patients with DM2 without signs of diabetic retinopathy (DR), and 60 eyes of 60 healthy controls underwent retinal (ganglion cell layer (GCL), and retinal nerve fiber layer (RNFL) and choroidal evaluation using Swept source Optical coherence tomography, which allows high quality analysis of the different retinal layers and the choroidal plexus. Comparison between patients with presence/absence of systemic vascular complications and different disease duration time was performed.

RESULTS

Macular GCL and RNFL were reduced in patients compared to controls (p < 0.001). In the peripapillary area, a reduction of the RNFL (p < 0.001) was observed in patients with DM2. There were no significant changes observed in the choroidal plexus of these patients. Patients with systemic ischaemia presented significant thinning of the choroid and further reduction of the temporal RNFL (p = 0.014) and GCL (p = 0.016) thickness. The GCL and the choroid were also thinner in patients with longer disease duration.

CONCLUSIONS

Patients with early DM2 present retinal neurodegeneration prior to the appearance of clinically observable vascular retinal changes. In these patients chronic systemic ischaemia caused reduction of the choroidal plexus and further damage to the retinal layers, adding new information on systemic chronic ischaemia and retinal neurodegeneration in patients with DM2 without DR.

Optical coherence tomography angiography reveals progressive worsening of retinal vascular geometry in diabetic retinopathy and improved geometry after panretinal photocoagulation

Purpose

To quantify vessel tortuosity and fractal dimension of the superficial capillary plexus (SCP) of the macula in different stages of diabetic retinopathy (DR), and following panretinal photocoagulation (PRP) using optical coherence tomography angiography (OCTA).

Methods

75 eyes of 75 subjects were divided into five groups; healthy controls, diabetes with no clinical DR, non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR) and patients who received PRP for PDR (PDR+PRP).For vessel tortuosity, SCP slabs from 3x3 mm macular OCTA scans were processed using imageJ (NIH, USA), where large perifoveal vessels were traced and their length was measured with tortuosity calculated as the ratio between the actual length and the straight Euclidean length. For fractal dimension, SCP slabs were processed and imported to Fractalyse (ThéMA, France), where box-counting analyses produced fractal dimension values.

Results

We found a significant difference in vessel tortuosity and fractal dimension between the five groups (one-way ANOVA, p < 0.001both). NPDR and PDR had significantly more tortuous vessels and lower fractal dimension compared to healthy controls (Tukey HSD: p = 0.02, 0.015,0.015 and <0.001, respectively). Fractal dimension was also significantly lower in NPDR and PDR compared to eyes with no clinical DR (p <0.001 both), and in PDR compared to NPDR (p = 0.014). Following PRP, vessel tortuosity was significantly lower and fractal dimension was higher in PDR+PRP compared to PDR (p = 0.001 and 0.031, respectively).

Conclusions

We used macular OCTA scans to demonstrate significantly higher perifoveal large vessel tortuosity, and lower fractal dimension in NPDR and PDR compared to healthy controls. Vessel tortuosity shows more dramatic normalization than fractal dimension and could be explored as a sensitive marker for successful PRP.

Topical Treatment With Brimonidine and Somatostatin Causes Retinal Vascular Dilation in Patients With Early Diabetic Retinopathy From the EUROCONDOR

Purpose

Structural retinal microvascular changes have been identified as risk markers of diabetic retinopathy (DR). In order to estimate the retinal response of neuroprotective eye drops, we aimed to evaluate the effect of topical retinal neuroprotection on retinal microvascular changes in early DR.

Methods

Patients with type 2 diabetes with no or early DR were randomized 1:1:1 to topical treatment with placebo, brimonidine, or somatostatin in a 96-week prospective, phase II to III, European multicenter trial. Retinal vascular calibers were measured semiautomatically in digital fundus images by certified graders at baseline and follow-up and summarized as central retinal arteriolar and venular equivalent (CRAE and CRVE).

Results

Of 449 patients originally included, 297 completed the study with gradable retinal images. Median age and duration of diabetes was 64.5 and 9.9 years, and 65.7% were male. At baseline, Early Treatment Diabetic Retinopathy Study levels were 10 (no DR, 42.8%), 20 (minimal DR, 28.3%), and 35 (mild DR, 29.0%), and CRAE and CRVE did not differ between groups. As opposed to patients with no or minimal DR at baseline, patients with mild DR in the active groups developed a larger retinal arteriolar (brimonidine: +6.2 μm, P = 0.006; somatostatin: +7.2 μm, P = 0.006) and venular (brimonidine: +13.9 μm, P = 0.01; somatostatin: +14.3 μm, P = 0.0001) caliber in contrast to those in the placebo group.

Conclusions

Topical treatment with brimonidine and somatostatin causes retinal arteriolar and venular dilation in patients with type 2 diabetes and preexisting early DR. Upcoming studies should elaborate on the potential of these findings in arresting early DR.

Global Assessment of Retinal Arteriolar, Venular and Capillary Microcirculations Using Fundus Photographs and Optical Coherence Tomography Angiography in Diabetic Retinopathy

Retinal arterioles, venules and capillaries are differentially affected in diabetes, and studying vascular alterations may provide information on pathogenesis of diabetic retinopathy (DR). We conducted a cross-sectional study on 49 diabetic patients, who underwent fundus photography and optical coherence tomographic angiography (OCT-A). Fundus photographs were analysed using semi-automated software for arteriolar and venular parameters, including central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE) and fractal dimension (FD). Capillary parameters were measured using OCT-A, including capillary density index (CDI) and capillary FD of superficial (SVP) and deep (DVP) vascular plexuses. Severe DR was defined as severe non-proliferative DR and proliferative DR. We found that eyes with severe DR had narrower CRAE and sparser SVP CDI than eyes without. In logistic regression analysis, capillary parameters were more associated with severe DR than arteriolar or venular parameters. However, combining arteriolar, venular and capillary parameters provided the strongest association with severe DR. In linear regression analysis, eyes with poorer visual acuity had lower CRAE and FD of arterioles, venules, and DVP capillaries. We concluded that the retinal microvasculature is globally affected in severe DR, reflecting widespread microvascular impairment in perfusion. Arteriolar, venular and capillary parameters provide complementary information in assessment of DR.

Neurodegeneration in Patients with Type 2 Diabetes Mellitus without Diabetic Retinopathy

Purpose

To evaluate neurodegeneration in patients with type 2 diabetes mellitus (DM2) without diabetic retinopathy and to assess the possible role of systemic vascular complications in retinal changes.

Methods

Sixty eyes of 60 patients with DM2 and without any signs of diabetic retinopathy and 60 eyes of 60 healthy controls underwent retinal evaluation using Spectralis optical coherence tomography. Macular ganglion cell layer (GCL) and retinal nerve fiber layer (RNFL) were evaluated. Peripapillary RNFL thickness was assessed using Glaucoma and Axonal Analytics applications. Comparison between patients with the presence/absence of systemic vascular complications and different disease duration was made.

Results

Macular GCL was reduced in patients compared to controls (p < 0.001). Differences in the macular RNFL thickness were only observed in the outer inferior sector (p=0.033). A reduction in the peripapillary RNFL (average, inferior, and inferotemporal thickness, p < 0.05 for all three) was observed in patients using both applications. Patients with chronic systemic vascular complications presented a reduction in the temporal RNFL (p=0.019) compared to patients without complications. The superotemporal RNFL thickness was thinner in patients with longer disease duration.

Conclusions

Patients with type 2 DM without diabetic retinopathy and good metabolic control present neurodegeneration affecting neurons in the macular area and axons in different sectors of the optic disc. Systemic vascular complications contributed to further axonal damage in these patients, suggesting a possible role of subclinical ischaemia to retinal neurodegeneration in type 2 DM.

Hemoglobin A1c and retinal arteriolar narrowing in children with type 1 diabetes: the diagnostics of early atherosclerosis risk in kids study

BACKGROUND/OBJECTIVE

Microvascular alterations play a key role in the development of diabetes complications. Retinal vessel analysis is a unique method to examine microvascular changes in brain-derived vessels.

METHODS

Sixty-seven pediatric and adolescent type 1 diabetes patients and 58 healthy control persons (mean age 12.4 ± 2.9 years) underwent non-mydriatic retinal photography of both eyes. Central retinal arteriolar and central retinal venular (CRVE) diameter equivalents as well as the arteriolar-to-venular ratio were calculated using a semiautomated software. All anthropometric and laboratory parameters were measured according to standardized procedures for children.

RESULTS

Retinal vessel diameter did not differ between type 1 diabetic children and healthy controls. However, there was an independent association of higher hemoglobin A1c (HbA1c) levels with arteriolar narrowing. Arteriolar narrowing of 5.4 μm was observed with each percent increase in HbA1c. Longer duration of diabetes was associated with wider retinal arterioles. CRVE was not associated with diabetes duration or HbA1c.

CONCLUSIONS

Microvascular arteriolar alterations are already present in childhood and may indicate subclinical atherosclerosis and increased risk of diabetes complications later in life. Future research will have to investigate the potential use of retinal vessel diameters for treatment monitoring and guidance of therapy in children.

Early atherosclerosis is associated with retinal microvascular changes in adolescents with type 1 diabetes

BACKGROUND/OBJECTIVE

Adolescents with type 1 diabetes have early macrovascular changes (increased intima-media thickness [IMT]) and early retinal changes that predict clinical disease in adulthood. We hypothesized that early changes in the macrovascular and retinal microvascular beds develop in parallel before retinopathy develops. We therefore aimed to investigate the relationship between changes in atherosclerosis (carotid and aortic IMT) and retinal vascular geometry cross-sectionally and longitudinally in adolescents with type 1 diabetes.

METHODS

Ninety adolescents with type 1 diabetes (41 boys, aged 13.6 ± 3.5 years) who were enrolled in a randomized controlled trial had evaluations at baseline; 41 randomized to placebo were also investigated at 12 months for carotid and aortic IMT using ultrasound and retinal vascular geometry was measured from retinal photographs.

RESULTS

There were significant associations between thicker mean/maximum carotid IMT and wider retinal arteriolar and venular calibers; for every 0.1 mm increase in mean carotid IMT, retinal arteriolar caliber increased by 7.90 μm (95% confidence interval [CI] 4.50, 11.30, P < 0.0001) and venular caliber by 9.61 μm (95% CI 4.16, 15.06, P = 0.0008). Increased mean aortic IMT was associated with increased arteriolar tortuosity (2.61, 95% CI 0.50, 4.71, P = 0.02).

CONCLUSIONS

The early changes of atherosclerosis are associated with retinal microvascular changes in adolescents with type 1 diabetes. This supports parallel adverse changes in the macro and microvascular circulations from early adolescence in type 1 diabetes, and highlights the importance of early intervention.

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.

Dynamic changes in retinal vessel diameter during acute hyperglycemia in type 1 diabetes

AIMS

To investigate changes in retinal vessel diameter during acute hyperglycemia in patients with type 1 diabetes.

METHODS

We conducted a study on 11 subjects with type 1 diabetes. Euglycemia was maintained for 3h followed by induction of hyperglycemia and simultaneous bolus of rapid acting insulin. Two fundus photos were captured during euglycemia and five fundus photos, blood glucose and blood pressure were taken every 30min for 2.5h post-prandial. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were measured over the study visit and examined using generalized linear mixed models.

RESULTS

In a multivariate mixed model, mean CRAE and CRVE were reduced at 90min post-prandial in both zones B and C. In repeated measures analysis, arterioles exhibited a significant association with change in vessel caliber per change in blood glucose. Inconsistent effects of blood pressure on vessel diameter were also measured.

CONCLUSIONS

We document a change in retinal vessel diameter during acute hyperglycemia in persons with type 1 diabetes. Larger controlled studies are required to further investigate this phenomenon and to more accurately assess if hyperglycemia has direct effects on retinal vessel diameter.

Retinal vascular imaging technology to monitor disease severity and complications in type 1 diabetes mellitus: A systematic review

OBJECTIVE

Type 1 diabetes mellitus (T1DM) is a major disease affecting a large number of young patients. In the recent years, retinal vascular imaging has provided an objective assessment of vascular health in patients with T1DM. Our study aimed to review the current literature on retinal vascular parameters in young patients with T1DM in order to understand the following: (i) How retinal vessels are affected in T1DM (ii) How such vascular changes can be predictive of future diabetic microvascular complications METHODS: We performed a systematic review and extracted relevant data from 17 articles.

RESULTS

We found significant correlations between retinal vessel changes and diabetes-related risk factors (eg, hypertension, hyperlipidemia, and obesity), diabetes-related features (eg, diabetes duration and glycemic control), and diabetes-related microvascular complications (eg, diabetic retinopathy, nephropathy, and neuropathy).

CONCLUSION

Our findings suggest that retinal microvasculature is associated with both disease severity and complications in young patients with T1DM.

Review of the association between retinal microvascular characteristics and eye disease

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

Retinal Oximetry and Vessel Diameter Measurements With a Commercially Available Scanning Laser Ophthalmoscope in Diabetic Retinopathy

Purpose

To test the hypothesis that retinal vascular diameter and hemoglobin oxygen saturation alterations, according to stages of diabetic retinopathy (DR), are discernible with a commercially available scanning laser ophthalmoscope (SLO).

Methods

One hundred eighty-one subjects with no diabetes (No DM), diabetes with no DR (No DR), nonproliferative DR (NPDR), or proliferative DR (PDR, all had photocoagulation) underwent imaging with an SLO with dual lasers (532 nm and 633 nm). Customized image analysis software determined the diameters of retinal arteries and veins (DA and DV) and central retinal artery and vein equivalents (CRAE and CRVE). Oxygen saturations of hemoglobin in arteries and veins (SO2A and SO2V) were estimated from optical densities of vessels on images at the two wavelengths. Statistical models were generated by adjusting for effects of sex, race, age, eye, and fundus pigmentation.

Results

DA, CRAE, and CRVE were reduced in PDR compared to No DM (P ≤ 0.03). DV and CRVE were similar between No DM and No DR, but they were higher in NPDR than No DR (P ≤ 0.01). Effect of stage of disease on SO2A differed by race, being increased relative to No DM in NPDR and PDR in Hispanic participants only (P ≤ 0.02). Relative to No DM, SO2V was increased in NPDR and PDR (P ≤ 0.05).

Conclusions

Alterations in retinal vascular diameters and SO2 by diabetic retinopathy stage can be detected with a widely available SLO, and covariates such as race can influence the results.

Innovative technology shows impact of glycaemic control on peripheral retinal vessels in adolescents with type 1 diabetes

AIMS/HYPOTHESIS

Retinal imaging enables non-invasive microvasculature assessment; however, only central retinal vessels have been studied in type 1 diabetes. Peripheral smaller vessels have a major haemodynamic role and may differ from central vessels in their response to the diabetic milieu. We hypothesise that diabetes has a greater impact on peripheral retinal vessels vs central vessels.

METHODS

Retinal photographs from adolescents (n = 736; age 12-20 years) with type 1 diabetes were graded (Singapore I Vessel Assessment) with vessel calibres measured in the 'central zone' as central retinal arteriolar and venular equivalents (CRAE and CRVE, respectively) and the 'extended zone' as mean width of arterioles and venules (MWa and MWv, respectively). Multivariable linear regression was used to explore associations between vessel calibres and HbA_1c, diabetes duration, sex and BP.

RESULTS

Mean ± SD age was 14.1 ± 1.5 years, HbA_1c was 8.5 ± 1.3% (69.4 ± 14.1 mmol/mol) and median diabetes duration was 4.9 years (interquartile range 3.1-7.6 years). Wider MWa was associated with HbA_1c (β 0.01 [95% CI 0.004, 0.03]), longer diabetes duration (0.07 [0.02, 0.13]) and higher systolic BP (0.04 [0.02, 0.05]). MWv was associated with HbA_1c (0.02 [0.009, 0.03]) and higher systolic BP (0.04 [0.03, 0.06]). CRAE was associated with longer diabetes duration (0.93 [0.58, 1.28]) and higher systolic BP (-0.28 [-0.37, -0.19]). CRVE was associated with longer diabetes duration (0.91 [0.42, 1.41]) and higher systolic BP (-0.20 [-0.33, -0.07]). Girls had wider vessels (for all four calibre measurements).

CONCLUSIONS/INTERPRETATION

In adolescents with type 1 diabetes, higher HbA_1c is associated with adverse changes to peripheral smaller retinal vessels but not central vessels. The predictive value of retinal vascular imaging should be evaluated using longitudinal data.

Retinal vascular geometry and 6 year incidence and progression of diabetic retinopathy

AIMS/HYPOTHESIS

We aimed to examine prospectively the association between a range of retinal vascular geometric variables measured from retinal photographs and the 6 year incidence and progression of diabetic retinopathy.

METHODS

We conducted a prospective, population-based cohort study of Asian Malay individuals aged 40-80 years at baseline (n = 3280) who returned for a 6 year follow-up. Retinal vascular geometric variables (tortuosity, branching, fractal dimension, calibre) were measured from baseline retinal photographs using a computer-assisted program (Singapore I Vessel Assessment). Diabetic retinopathy was graded from baseline and follow-up photographs using the modified Airlie House classification system. Incidence of diabetic retinopathy was defined as a severity of ≥15 at follow-up among those without diabetic retinopathy at baseline. Incidence of referable diabetic retinopathy was defined as moderate or severe non-proliferative diabetic retinopathy, proliferative diabetic retinopathy or diabetic macular oedema at follow-up in participants who had had no or mild non-proliferative diabetic retinopathy at baseline. Progression of diabetic retinopathy was defined as an increase in severity of ≥2 steps at follow-up. Log-binomial models with an expectation-maximisation algorithm were used to estimate RR adjusting for age, sex, diabetes duration, HbA_1c level, BP, BMI, estimated GFR and total and HDL-cholesterol at baseline.

RESULTS

A total of 427 individuals with diabetes participated in the baseline and 6 year follow-up examinations. Of these, 19.2%, 7.57% and 19.2% developed incidence of diabetic retinopathy, incidence of referable diabetic retinopathy and diabetic retinopathy progression, respectively. After multivariate adjustment, greater arteriolar simple tortuosity (mean RR [95% CI], 1.34 [1.04, 1.74]), larger venular branching angle (RR 1.26 [1.00, 1.59]) and larger venular branching coefficient (RR 1.26 [1.03, 1.56]) were associated with incidence of diabetic retinopathy. Greater arteriolar simple tortuosity (RR 1.82 [1.32, 2.52]), larger venular branching coefficient (RR 1.46 [1.03, 2.07]), higher arteriolar fractal dimension (RR 1.59 [1.08, 2.36]) and larger arteriolar calibre (RR 1.83 [1.15, 2.90]) were associated with incidence of referable diabetic retinopathy. Greater arteriolar simple tortuosity (RR 1.34 [1.12, 1.61]) was associated with diabetic retinopathy progression. Addition of retinal vascular variables improved discrimination (C-statistic 0.796 vs 0.733, p = 0.031) and overall reclassification (net reclassification improvement 18.8%, p = 0.025) of any diabetic retinopathy risk beyond established risk factors.

CONCLUSIONS/INTERPRETATION

Retinal vascular geometry measured from fundus photographs predicted the incidence and progression of diabetic retinopathy in adults with diabetes, beyond established risk factors.

The Effects of Diabetic Retinopathy Stage and Light Flicker on Inner Retinal Oxygen Extraction Fraction

Purpose

We determined the effects of light flicker and diabetic retinopathy (DR) stage on retinal vascular diameter (D), oxygen saturation (SO2), and inner retinal oxygen extraction fraction (OEF).

Methods

Subjects were categorized as nondiabetic control (NC, n = 42), diabetic with no clinical DR (NDR; n = 32), nonproliferative DR (NPDR; n = 42), or proliferative DR (PDR; n = 14). Our customized optical imaging system simultaneously measured arterial and venous D (DA, DV) and SO2 (SO2A, SO2V) before and during light flicker. Inner retinal OEF was derived from SO2 values. Light flicker-induced ratios of metrics (DAR, DVR, SO2AR, SO2VR, OEFR) were calculated.

Results

Arterial D was larger in NPDR compared to NC (P = 0.01) and PDR (P = 0.002), whereas DV was similar among groups (P ≥ 0.16). Light flicker increased DA and DV (P ≤ 0.004), but DAR and DVR were similar among groups (P ≥ 0.09). Arterial SO2 was higher in all groups compared to NC (P ≤ 0.02) and higher in PDR compared to NDR and NPDR (P<0.001). Arterial SO2 did not change with light flicker (P ≥ 0.1). Venous SO2 was higher in NPDR and PDR compared to NC and NDR (P ≤ 0.02). Light flicker increased SO2V in NC, NDR, and PDR (P ≤ 0.003), and SO2VR was lower in NPDR compared to NC and NDR (P ≤ 0.05). Inner retinal OEF was lower in NPDR compared to NDR and PDR (P ≤ 0.02). Light flicker decreased OEF (P ≤ 0.03), but OEFR was greater in NPDR compared to NC and NDR (P ≤ 0.03).

Conclusions

The findings of alterations in retinal D, SO2, OEF, and their light flicker-induced responses at stages of DR may be useful to elucidate the pathophysiology of DR.

Noninvasive Retinal Markers in Diabetic Retinopathy: Advancing from Bench towards Bedside

The retinal vascular system is the only part of the human body available for direct, in vivo inspection. Noninvasive retinal markers are important to identity patients in risk of sight-threatening diabetic retinopathy. Studies have correlated structural features like retinal vascular caliber and fractals with micro- and macrovascular dysfunction in diabetes. Likewise, the retinal metabolism can be evaluated by retinal oximetry, and higher retinal venular oxygen saturation has been demonstrated in patients with diabetic retinopathy. So far, most studies have been cross-sectional, but these can only disclose associations and are not able to separate cause from effect or to establish the predictive value of retinal vascular dysfunction with respect to long-term complications. Likewise, retinal markers have not been investigated as markers of treatment outcome in patients with proliferative diabetic retinopathy and diabetic macular edema. The Department of Ophthalmology at Odense University Hospital, Denmark, has a strong tradition of studying the retinal microvasculature in diabetic retinopathy. In the present paper, we demonstrate the importance of the retinal vasculature not only as predictors of long-term microvasculopathy but also as markers of treatment outcome in sight-threatening diabetic retinopathy in well-established population-based cohorts of patients with diabetes.

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

BACKGROUND

The aim of the study was to describe the relationship of retinal arteriolar and venular calibre with vascular risk factors in children and adolescents with type 1 diabetes.

METHODS

In this hospital-based cross-sectional study, the medical files of 483 children and adolescents with type 1 diabetes were audited to collect retinal images and relevant clinical data. Retinal vascular calibre was measured using standardised protocols.

RESULTS

After multivariable adjustments, a vascular risk profile that included: older age, higher serum creatinine, higher systolic blood pressure (SBP), higher body mass index (BMI), abnormal estimated glomerular filtration rate (eGFR), lower high-density lipoproteins (HDL) cholesterol, longer duration of diabetes and higher serum sodium was associated with narrower central retinal artery equivalent (CRAE) (95% CI=-4.10/-0.76, p=0.004). A specific risk profile, including higher total cholesterol level, higher BMI, lower physical activity level, higher HbA1c, higher triglyceride levels, female gender and lower socio-economic status, was associated with wider central retinal vein equivalent (CRVE) (95% CI=1.14/5.62, p=0.003).

CONCLUSIONS

In summary, these findings support evidence that cardiovascular disease may have its origins early in life. Prospective and/or intervention studies are required to confirm whether the observed associations are involved in the causal pathway for retinal vascular calibre.

Retinal changes in diabetic patients without diabetic retinopathy

PURPOSE

The purpose of this study was to measure retinal vessel caliber and to examine early changes in macular thickness using optical coherence tomography (OCT). We evaluated to what extend vascular caliber and macular thickness differed between patients with type 2 diabetes mellitus without diabetic retinopathy compared with healthy individuals.

METHODS

26 diabetic patients without diabetic retinopathy and 26 normal participants without any retinal and optic nerve diseases underwent ophthalmic examination, fundus photography, and OCT imaging. Temporal inferior retinal vessel diameters were measured using OCT. Also, we measured macular thickness in nine ETDRS subfields using Cirrus OCT.

RESULTS

The mean age in the diabetic group was 61.5 years and in the control group, 55.5 years. Wider retinal arterioles and venules were found in patients with diabetes compared with healthy subjects (120 µm versus 96 µm, p<0.005 and 137 µm versus 120.5 µm, p value <0.001, respectively). In patients with type 2 diabetes mellitus, central macular thickness was significantly thinner than that of control eyes (243.5 µm versus 269.9 µm, p value <0.001).

CONCLUSIONS

Our results support the hypothesis that the association between vascular damage and structural changes of the neuroretina is an early indicator of retinal impairment in patients with diabetes without diabetic retinopathy.

Biomarkers of Diabetic Retinopathy

Diabetic retinopathy (DR), a leading cause of acquired vision loss, is a microvascular complication of diabetes. While traditional risk factors for diabetic retinopathy including longer duration of diabetes, poor blood glucose control, and dyslipidemia are helpful in stratifying patient's risk for developing retinopathy, many patients without these traditional risk factors develop DR; furthermore, there are persons with long diabetes duration who do not develop DR. Thus, identifying biomarkers to predict DR or to determine therapeutic response is important. A biomarker can be defined as a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. Incorporation of biomarkers into risk stratification of persons with diabetes would likely aid in early diagnosis and guide treatment methods for those with DR or with worsening DR. Systemic biomarkers of DR include serum measures including genomic, proteomic, and metabolomics biomarkers. Ocular biomarkers including tears and vitreous and retinal vascular structural changes have also been studied extensively to prognosticate the risk of DR development. The current studies on biomarkers are limited by the need for larger sample sizes, cross-validation in different populations and ethnic groups, and time-efficient and cost-effective analytical techniques. Future research is important to explore novel DR biomarkers that are non-invasive, rapid, economical, and accurate to help reduce the incidence and progression of DR in people with diabetes.

Thickening of inner retinal layers in the parafovea after bariatric surgery in patients with type 2 diabetes

PURPOSE

Bariatric surgery dramatically improves the metabolic profile in patients with type 2 diabetes (T2D). We have previously reported a thickening of the retina after bariatric surgery and aimed to investigate these subclinical changes in retinal thickness and vessel calibres in more detail.

METHODS

We examined 51 patients with T2D 2 weeks before and 1, 3, 6 and 12 months after bariatric surgery. Retinal thickness was measured with optical coherence tomography and automated segmentation in the fovea, parafovea and perifovea in each retinal layer. Retinal vessels were semiautomatically measured in a zone 0.5-1 disc diameters from the optic disc.

RESULTS

The total macula thickened with a peak after 6 months in both univariate (2.7 ± 0.4 μm, p < 0.001) and multivariate analysis (2.2 ± 0.7 μm, p = 0.001). The thickening was most prominent in the parafoveal ring 1-3 mm from the centre and in the retinal nerve fibre layer and outer nuclear layer. A fall in HbA_1c (p = 0.01) and longer duration of diabetes (p = 0.01) were associated with more thickening. The central retinal artery equivalent widened 22.1 μm (±8.9, p = 0.01) in the multivariate analysis 12 months postoperatively. A reduction in blood pressure was associated with less widening of the arterioles (p = 0.01).

CONCLUSION

Patients with T2D had thickening of the retina after gastric bypass surgery with a peak 6 months postoperatively. The thickening was most pronounced in the retinal nerve fibre layer and the outer nuclear layer of the parafovea. In multivariate analysis, the central retinal artery equivalent increased at 12 months.

Prevalence and risk factors for diabetic retinopathy in a hospital-based population of Australian children and adolescents with type 1 diabetes

BACKGROUND

The aim of this study was to investigate the prevalence of, and traditional and emerging risk factors associated with, retinopathy in a hospital-based population of Australian children and adolescents with type 1 diabetes.

METHODS

This was a cross-sectional study of 483 children and adolescents with type 1 diabetes. Medical files were audited to collect all relevant clinical data. Diabetic retinopathy was assessed from colour retinal images by an ophthalmologist.

RESULTS

Diabetic retinopathy was observed in 11 (2.3%) participants. Logistic regression revealed that the principal components analysis derived risk profile of: higher serum creatinine, older age, higher systolic blood pressures, higher body mass index, abnormal estimated glomerular filtration rate (eGFR) (<59 mL/min), lower high density lipoproteins (HDL) cholesterol, higher serum sodium, longer duration of diabetes and narrower retinal arteriolar calibre was associated with diabetic retinopathy (ExpB=2.60, 95% CI 1.36/4.96, p=0.004).

CONCLUSIONS

These results support the concept that the pathogenesis of diabetic retinopathy is likely due to the combined influence of various risk factors, many already identified.

Retinal vascular geometry and its association to microvascular complications in patients with type 1 diabetes: the Danish Cohort of Pediatric Diabetes 1987 (DCPD1987)

PURPOSE

To examine associations between retinal vascular geometry (tortuosity, branching coefficient [BC] and length-diameter ratio [LDR]) and diabetic proliferative retinopathy (PDR), nephropathy, and peripheral neuropathy in patients with type 1 diabetes mellitus (T1DM).

METHODS

A cohort of patients with T1DM participated in a clinical examination in 2011. Blood and urine analyses were done and retinal images taken. PDR was defined as Early Treatment Diabetic Retinopathy Study level 61 or above, nephropathy as albumin-creatinin ratio ≥300 mg/g, and neuropathy as vibration perception threshold >25 Volt. Retinal vessel parameters were measured using semi-automated software. Multiple logistic regressions were performed to investigate correlations between retinal vascular parameters and outcomes. Models were adjusted for other variables (sex, age, duration of diabetes, systolic and diastolic blood pressure, HbA1c, and presence of microvascular complications). Odds ratios were given per standard deviation in retinal vascular parameter.

RESULTS

Retinal vascular analyses were performed in 181 patients. Mean age and duration of diabetes were 37.0 years and 29.4 years respectively, and 50.8% were male. Prevalence of PDR, nephropathy, and neuropathy were 26.5%, 6.8%, and 10.1% , respectively. Patients with increased arteriolar BC had a higher risk of nephropathy (OR: 3.10, 95% CI: [1.01-9.54]). Patients with increased venular BC had a higher risk of neuropathy (OR: 2.11, 95% CI: [1.11-4.03]). No associations were found in patients with PDR.

CONCLUSIONS

By analyzing the retinal vascular tree in patients with T1DM, we found a higher risk of complications in kidneys and nerves when BC was increased. This might indicate a suboptimal construction of the vascular tree in these patients.

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.

Correlation between Retinal Vessel Calibre and Neurodegeneration in Patients with Type 2 Diabetes Mellitus in the European Consortium for the Early Treatment of Diabetic Retinopathy (EUROCONDOR)

PURPOSE

To investigate the correlation between retinal vessel calibre and measurements of neurodegeneration in patients with type 2 diabetes (T2D) and no or early diabetic retinopathy (DR).

METHODS

Baseline data on 440 patients with T2D from the EUROCONDOR clinical trial were used. DR was graded according to the Early Treatment of Diabetic Retinopathy Study (ETDRS) scale, and patients with ETDRS levels 10-35 were included. Retinal vessel diameters were measured by semi-automatic software. Calibres were summarized into central retinal artery and vein equivalents (CRAE and CRVE).

RESULTS

Median age and diabetes duration were 64.0 and 10.3 years, respectively. ETDRS levels were 10 (42.3%), 20 (27.5%) and 35 (30.2%). The median CRAE and CRVE were 146.7 and 215.3 µm, respectively. CRAE did not differ according to ETRDS level (p = 0.12), but wider CRVE were found in patients with higher ETDRS levels (p = 0.04). In a multivariable linear regression model, CRAE was associated with macular ganglion cell layer thickness (coefficient 0.27 per micrometre, p < 0.01), and CRVE was correlated with macular retinal thickness (coefficient -0.07 per micrometre, p = 0.04) and retinal nerve fibre layer thickness at the optic disc (coefficient 0.32 per micrometre, p < 0.01).

CONCLUSION

Retinal vessel calibre was independently associated with structural changes of the neuroretina in patients with no or early DR.

Retinal ganglion cell neuronal damage in diabetes and diabetic retinopathy

BACKGROUND

To examine the association of diabetes and diabetic retinopathy (DR) with retinal ganglion cell (RGC) loss.

DESIGN

Observational case-control study.

PARTICIPANTS

Type 2 diabetes cases and age-gender matched controls without diabetes.

METHODS

Spectral-domain optical coherence tomography (OCT) parameters of RGCs were calculated after automated segmentation of macular scans. DR severity was graded on fundus photographs using the modified Airlie House Classification system. Generalized estimating equation was used to compare OCT parameters between cases and controls, adjusted for covariates.

MAIN OUTCOME MEASURES

Average ganglion cell-inner plexiform layer (GC-IPL) and average retinal nerve fibre layer (RNFL) thicknesses.

RESULTS

We analyzed 227 cases and 227 controls. The mean age (years) of cases was 58.3 and controls was 58.1 (P = 0.13). Among cases, 101 had none, 25 had mild and 101 had moderate or severe DR. Compared with controls, GC-IPL and RNFL were thinner in all cases [mean difference (95% confidence interval [CI]): GC-IPL -4.49 µm (-2.92; -6.06), RNFL -0.93 µm (-0.09; -1.85)], including cases with no DR [mean difference (95% CI), GC-IPL -4.37 µm (-2.72; -6.02), RNFL -1.06 µm (-0.10; -2.02)]. Cases with any DR had thinner GC-IPL than controls [mean difference (95% CI): GC-IPL -4.81 µm (-2.12; -7.50)]. Among cases, subjects with moderate or severe DR had thinner GC-IPL than subjects with no DR [mean difference (95% CI): GC-IPL -2.07 µm (-0.08; -4.07)].

CONCLUSIONS

RGC loss is present in subjects with diabetes and no DR, and is progressive in moderate or severe DR. RGC neuronal damage in diabetes and DR can be clinically detected using OCT.

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.

The progress in understanding and treatment of diabetic retinopathy

Diabetic retinopathy is the most frequently occurring complication of diabetes mellitus and remains a leading cause of vision loss globally. Its aetiology and pathology have been extensively studied for half a century, yet there are disappointingly few therapeutic options. Although some new treatments have been introduced for diabetic macular oedema (DMO) (e.g. intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') and new steroids), up to 50% of patients fail to respond. Furthermore, for people with proliferative diabetic retinopathy (PDR), laser photocoagulation remains a mainstay therapy, even though it is an inherently destructive procedure. This review summarises the clinical features of diabetic retinopathy and its risk factors. It describes details of retinal pathology and how advances in our understanding of pathogenesis have led to identification of new therapeutic targets. We emphasise that although there have been significant advances, there is still a pressing need for a better understanding basic mechanisms enable development of reliable and robust means to identify patients at highest risk, and to intervene effectively before vision loss occurs.

Biomarkers in Diabetic Retinopathy

There is a global diabetes epidemic correlating with an increase in obesity. This coincidence may lead to a rise in the prevalence of type 2 diabetes. There is also an as yet unexplained increase in the incidence of type 1 diabetes, which is not related to adiposity. Whilst improved diabetes care has substantially improved diabetes outcomes, the disease remains a common cause of working age adult-onset blindness. Diabetic retinopathy is the most frequently occurring complication of diabetes; it is greatly feared by many diabetes patients. There are multiple risk factors and markers for the onset and progression of diabetic retinopathy, yet residual risk remains. Screening for diabetic retinopathy is recommended to facilitate early detection and treatment. Common biomarkers of diabetic retinopathy and its risk in clinical practice today relate to the visualization of the retinal vasculature and measures of glycemia, lipids, blood pressure, body weight, smoking, and pregnancy status. Greater knowledge of novel biomarkers and mediators of diabetic retinopathy, such as those related to inflammation and angiogenesis, has contributed to the development of additional therapeutics, in particular for late-stage retinopathy, including intra-ocular corticosteroids and intravitreal vascular endothelial growth factor inhibitors ('anti-VEGFs') agents. Unfortunately, in spite of a range of treatments (including laser photocoagulation, intraocular steroids, and anti-VEGF agents, and more recently oral fenofibrate, a PPAR-alpha agonist lipid-lowering drug), many patients with diabetic retinopathy do not respond well to current therapeutics. Therefore, more effective treatments for diabetic retinopathy are necessary. New analytical techniques, in particular those related to molecular markers, are accelerating progress in diabetic retinopathy research. Given the increasing incidence and prevalence of diabetes, and the limited capacity of healthcare systems to screen and treat diabetic retinopathy, there is need to reliably identify and triage people with diabetes. Biomarkers may facilitate a better understanding of diabetic retinopathy, and contribute to the development of novel treatments and new clinical strategies to prevent vision loss in people with diabetes. This article reviews key aspects related to biomarker research, and focuses on some specific biomarkers relevant to diabetic retinopathy.

Design and feasibility of "PREMATurity as predictor of children's Cardiovascular-renal Health" (PREMATCH): A pilot study

The microvasculature and macrovasculature undergo extensive, organ-specific perinatal maturation. Multiple studies show associations between low birth weight and subsequent cardiovascular dysfunction in adulthood, suggesting that extreme preterm birth interferes with this maturation process. Therefore, we designed PREMATCH (PREMATurity as predictor of Cardiovascular–renal Health) to phenotype the microcirculation and macrocirculation during childhood in former preterm infants. A well-characterized cohort of former extreme preterm birth survivors and gender- and age-matched controls (aged 8–13 years) will be investigated for microvascular and macrovascular structure and function. In addition to cognitive performance and anthropometrics, we will investigate (i) the microvascular structure and function by endothelial function (photoplethysmography), sublingual capillary glycocalyx function (sidestream dark field imaging) and retinal structure (diameters of arterioles and venules); and (ii) the macrovascular phenotype by cardiac and renal ultrasound, repeated blood pressure measurements and arterial pulse-wave recordings. The PREMATCH study is unique in its design, and ongoing recruitment demonstrates excellent feasibility. The expectation is that the results of this study will identify risk factors during childhood for subsequent cardiovascular–renal disease in the adult life of former preterm infants, while further analysis on mediators in neonatal life of this cardiovascular–renal outcome may provide new information on perinatal risk factors.