Arteriolar Caliber Research Articles

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

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

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

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a marker of cardiac dysfunction and has been linked to various indices of large vessel disease. However, it remains unclear whether NT-proBNP also relates to microvascular damage. In a community-dwelling population, we studied the association between NT-proBNP and retinal microvascular damage. From the population-based Rotterdam Study, we included 8437 participants (mean age 64.1 years and 59% women) without a history of cardiovascular disease, with NT-proBNP data and gradable retinal images. NT-proBNP serum levels were measured using an immunoassay. Retinopathy signs, that is, exudates, microaneurysms, cotton wool spots, and dot/blot hemorrhages, present on fundus photographs were graded in the total study population; retinal vascular calibers, that is, arteriolar and venular calibers, were semiautomatically measured in a subsample (n=2763) of the study population. We conducted cross-sectional analyses on the association between NT-proBNP and retinal microvascular damage using logistic and linear regression models, adjusting for age, sex, and cardiovascular risk factors. We found that NT-proBNP was associated with the presence of retinopathy (adjusted odds ratio [95% confidence interval] per SD increase in natural log-transformed NT-proBNP: 1.14 [1.03-1.27]). We also found that higher NT-proBNP was associated with narrower arteriolar calibers (adjusted mean difference in arteriolar caliber per SD increase in natural log-transformed NT-proBNP: -0.89 µm [-1.54 to -0.24]). This association remained unchanged after excluding participants with retinopathy signs. In participants free of clinical cardiovascular disease, higher levels of NT-proBNP are associated with retinal microvascular damage, suggesting a potential role for NT-proBNP as marker for small vessel disease.

New aspect for systemic effects of COPD: eye findings.

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

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

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

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

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

Arteriolar Diameters in Glaucomatous Eyes with Single-Hemifield Damage.

To examine the association between retinal arteriolar caliber and lumen, retinal sensitivity (RS), and retinal nerve fiber layer (RNFL) thickness in glaucomatous eyes with single-hemifield loss. We conducted a prospective, nonrandomized, case-control study of 20 eyes of 20 patients with glaucoma with visual field damage confined to a single hemifield. The control group was composed of 20 eyes of 20 normal subjects. For all the eyes, we performed optical coherence tomography to assess the RNFL and standard automated perimetry to evaluate RS. External and internal arteriolar diameters were assessed in vivo using scanning laser Doppler flowmetry. The RNFL was significantly thinner in glaucomatous eyes than in normal eyes (p < 0.001). In glaucomatous eyes, a positive correlation between sectorial RNFL thickness and the corresponding external and internal arteriolar diameters was found (r = 0.43, p = 0.05; r = 0.63, p = 0.003, respectively). The internal arteriolar diameter significantly correlated with RS in the corresponding abnormal hemifield (r = 0.44, p = 0.04). Compared with the normal hemifield, the internal arteriolar diameter, RNFL thickness, and RS were significantly reduced, whereas the external arteriolar diameter was unchanged in the abnormal hemifield. In glaucomatous eyes with single-hemifield damage, attenuation of retinal vessels was associated with a thinner RNFL and reduced RS. Moreover, a narrower lumen with increased wall-to-lumen ratio was found in the abnormal hemifield, supporting the hypothesis that vessel narrowing is likely secondary to a lower demand for blood flow in the glaucomatous areas of the retina.

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

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

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

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

Effects of longitudinal body mass index variability on microvasculature over 5 years in adult Chinese

To explore the associations of 5-year trend and fluctuation in body mass index (BMI) with retinal vascular caliber in a middle-aged and elderly Chinese population. Participants age ≥40 years were recruited in a prospective study. Baseline BMI data were collected in 2008, and the participants were re-examined annually until 2012. Retinal vascular caliber was measured from fundus photographs collected in 2012. BMI trend was calculated as the slope of BMI against the time of examinations. BMI fluctuation was defined as the root mean square error around the regression line of BMI over time (BMI RMSE) and the coefficient of variation of BMI (BMI CV). Rising BMI trend was associated with narrower retinal arteriolar and wider venular calibers in the overall subjects, especially among persons with overweight and obesity (BMI ≥ 25 kg/m(2) , P = 0.004 and 0.033, respectively). Rising BMI trend was also significantly associated with narrower retinal arteriole even in nonobese individuals with BMI < 25 kg/m(2) (P = 0.017) when eliminating the effects of hypertension and diabetes. Neither BMI RMSE nor BMI CV was statistically associated with retinal vascular caliber (all P > 0.05). Annual rising trending BMI was associated with retinal microvascular alteration. The results suggest that weight gain probably increases the risk of cardiovascular diseases among middle-aged and elderly people.

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

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

Retinal vessel diameters in a Japanese population: the Locomotive Syndrome and Health Outcome in Aizu Cohort Study.

To describe the relationship between retinal vascular calibre and cardiovascular risk factors in a Japanese population. The Locomotive Syndrome and Health Outcome in Aizu Cohort Study is a population-based, cross-sectional survey that included 2346 persons (56.1% of the eligible population) aged 40 to 74years old. Retinal vascular calibre was measured from digital retinal photographs using a validated standardized protocol. Data on major cardiovascular risk factors were collected from all participants. Of the 1787 participants with available retinal vascular calibre data, the mean retinal arteriolar calibre (CRAE) was 141.6±18.6μm, the mean venular calibre (CRVE) was 209.3±26.1μm, and the mean arteriole-to-venule ratio was 0.68±0.08. A smaller CRAE was associated with male sex, increasing quartiles of systolic blood pressure and diastolic blood pressure, history of hypertension, current alcohol intake and higher quartiles of serum creatinine. A larger CRAE was associated with increasing quartiles of total cholesterol. A larger CRVE was associated with current cigarette smoking. Multivariate analyses showed that a smaller CRAE was associated with male sex, elevated mean arterial blood pressure and a history of hypertension; and a larger CRVE was associated with cigarette smoking. The results of this study suggest that a narrowed diameter of the retinal arteriole in Japanese people is related to hypertension and sex (male) and that an enlarged retina venular diameter is related to a history of smoking. The pattern of these associations is similar to that in white populations and other Asian populations.

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

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. 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. 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). 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.

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

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

Retinal Vessel Diameter and Chronic Kidney Disease in Rural China: A Cross-Sectional Study.

Few studies have examined the relationship between retinal microvascular abnormalities and chronic kidney disease (CKD). This study aims to examine the association between retinal vessel diameters and CKD in the rural China in order to provide the scientific basis for the early detection and diagnosis for CKD.Participants and data were extracted from the Handan Eye Study, a population-based cross-sectional study performed from 2006 to 2007. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were summarized by the average arteriolar and venular caliber of each eye. The estimated glomerular filtration rate (eGFR) and a urinary albumin to creatinine ratio (ACR) were recorded. Multivariate logistic regression models were used to determine any associations between CRAE, CRVE, arteriole-to-venule ratio (AVR), retinopathy, and CKD in the recruited participants.CKD was found in was 17.3% (892/5158) of this population with a 0.9% (48/5545) rate of reduced renal function and 16.7% (922/5538) rate of albuminuria. Retinopathy was present in 9.6% (571/5925) of participants. Compared to the 4th quartile of AVR, the first group was found to have a higher risk of albuminuria (odds ratio [OR] = 1.261, 95% confidence interval [95%CI]: 1.015–1.567, P = 0.037) and CKD (OR = 1.240, 95%CI: 1.000–1.537, P = 0.049) after adjustment for potential confounding variables. Retinopathy was associated with the occurrence of albuminuria (OR = 1.340, 95%CI: 1.067–1.685, P = 0.012) and CKD (OR = 1.341, 95%CI: 1.071–1.681, P = 0.010). In participants with diabetes, the ORs for the 1st and 4th quartiles of CRAE and CRVE were 2.292 (95%CI: 1.076–4.881, P = 0.032) and 2.113 (95%CI: 1.006–4.438, P = 0.048), respectively. Among the participants with hypertension, retinopathy was also observed to be associated with CKD (OR = 1.306, 95%CI: 1.003–1.699, P = 0.047).The parameters of retinal vessel diameter may be a useful index evaluating the occurrence and development of CKD.

Retinal vessel calibres and haemostasis in black and white South Africans: the SABPA study.

Retinal arteriolar narrowing associates with hypertension development and indicates increased cardiovascular risk. Evidence on whether the retinal vessel calibres are related to the haemostatic system is limited, especially in the black hypertension-prone population with a high stroke incidence. We therefore investigated the relationships between haemostatic markers and retinal vessel calibres. We performed a cross-sectional study involving 170 black (mean age, 58 years; 44% women) and 189 white (mean age, 49 years; 52% women) teachers, and determined ambulatory blood pressure, haemostatic factors (fibrinogen, von Willebrand factor, D-dimer, plasminogen activator inhibitor-1 and clot lysis time) and retinal vessel calibres (central retinal artery and vein equivalent). The black and white groups were stratified by median split of the retinal arteriolar calibre. Both ethnic groups with a smaller arteriolar calibre had higher SBP and narrower venular calibres. In the black population, the central retinal vein equivalent was positively (β = 0.293; P = 0.024) associated with fibrinogen, whereas in the white population, the central retinal artery equivalent (β = -0.256; P = 0.016) was negatively and central retinal vein equivalent (β = 0.234; P = 0.021) positively associated with von Willebrand factor. Furthermore, clot lysis time was negatively associated with the central retinal artery equivalent (β = -0.390; P = 0.014) in the black group and positively associated with the central retinal vein equivalent (β = 0.275; P = 0.008) in the white group. Relationships between markers of haemostasis and the retinal vessel calibres exist, and vary between ethnicities. Haemostatic alterations are linked to early retinal microvascular changes, and future studies should investigate whether it translates into an elevated stroke risk.

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

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

Ambulatory aortic stiffness, independently of static, associates with narrower retinal arteriolar calibers in hypertensives: The SAFAR study

Ambulatory aortic stiffness, independently of static, associates with narrower retinal arteriolar calibers in hypertensives: The SAFAR study

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

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

Regarding: Diabetic macular ischaemia is associated with narrower retinal arterioles in patients with type 2 diabetes

I read with great interest the article ‘Diabetic macular ischaemia is associated with narrower retinal arterioles in patients with type 2 diabetes’ by Liew et al. (2015). The authors should be congratulated on this important article regarding diabetic macular ischaemia (DMI) which is a severe vision-threatening condition, even in the anti-VEGF era. The main finding of the article was an independent association between central retinal arteriolar narrowing and DMI. Retinal vascular calibres are important non-invasive biomarkers which are predictive of early-stage (Cheung et al. 2008) as well as end-stage diabetic retinopathy (Broe et al. 2014). However, observations regarding retinal vascular calibres and diabetic macular oedema (DMO) or DMI are still limited. In a retrospective study of 69 eyes from patients with DMO, we found a decrement in macular retinal arteriolar and venular calibres 6 months after focal/grid laser treatment (Lundberg et al. 2013). On the other hand, we did not find a statistically significant change in central retinal arteriolar or venular diameter. Liew et al. (2015) elegantly demonstrated an inverse association between DMI severity and central retinal arteriolar diameter, but this was no longer statistically significant when patients who had panretinal photocoagulation (PRP) were excluded. Panretinal photocoagulation is considered an important confounder because it has been demonstrated that patients who had PRP were more likely to have central retinal arteriolar narrowing (Grauslund et al. 2009). Given that central retinal arteriolar vessel calibres are measured around the optic disc, these might be considered a more ‘global’ measurement of retinal function. Did the authors consider expanding the observations to macular calibre measurements given that this could be a more sensitive marker of macular perfusion?

Are Retinal Vessels Calibers Influenced by Blood Pressure Measured at the Time of Retinography Acquisition?

BackgroundRetinal arterial narrowing is associated with higher office blood pressure (BP) and ambulatory blood pressure monitoring, and increased incidence of cardiovascular disease, but it is still unknown if the vessel caliber is associated with BP measured at the time of retinography acquisition.MethodsRetinal arteriolar and venular calibers were measured by the microdensitometric method in 448 patients with hypertension. Participants underwent 24-hours ambulatory blood pressure (24-h ABP) monitoring simultaneously with the retinography acquisition. Association between arteriolar and venular calibers with increase of 10 mmHg in the mean 24-hours, daily, and nightly BP, and with BP measured at the time of retinography, was evaluated by ANOVA and multivariate analyses.ResultsMean 24-hours, daytime and nighttime systolic and diastolic BP were inversely associated with the arteriolar caliber, but not with the venular caliber. Arteriolar caliber decreased -0.8 (95% CI -1.4 to -0.2) μm per 10-mmHg increase in 24-hours mean systolic BP, adjusted for age, gender, fellow vessel, and duration of hypertension (P = 0.01). The corresponding decreasing in arteriolar caliber by 10 mmHg of increasing in mean diastolic BP was -1.1 μm (-2.0 to -0.2, P = 0.02). The decrease of arteriolar caliber by the same increasing of BP measured at the time of retinography was lower and not statistically significant, particularly for mean diastolic BP and outer arterioles calibers: -1.0 (-1.8 to -0.2) μm in the daytime BP average versus -0.3 (-0.9 to 0.3) at the moment of retinography acquisition.ConclusionsThese findings suggest that the caliber of arteriolar retinal vessels in patients with uncontrolled hypertension are not significantly influenced by blood pressure measured at the time of retinography acquisition.