Retinal Venular Caliber Research Articles

Low serum testosterone and increased diastolic ocular perfusion pressure: a risk for retinal microvasculature.

Low levels of testosterone in men and changes in retinal microvascular calibre are both associated with hypertension and cardiovascular disease risk. Sex hormones are also associated with blood flow in microvascular beds which might be a key intermediate mechanism in the development of hypertension. Whether a direct association between endogenous testosterone and retinal microvascular calibre exists is currently unknown. We aimed to determine whether testosterone is independently associated with ocular perfusion via a possible association with retinal vascular calibre or whether it plays only a secondary role via its effect on blood pressure in a bi-ethnic male cohort. A total of 72 black and 81 white men (28-68 years of age) from the follow-up phase of the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study were included in this sub-study. Ambulatory pulse pressure and intraocular perfusion pressures were obtained, while metabolic variables and testosterone were measured from fasting venous blood samples. Retinal vascular calibre was quantified from digital photographs using standardised protocols. The black men revealed a poorer cardiometabolic profile and higher pulsatile pressure (>50 mm Hg), intraocular pressure and diastolic ocular perfusion pressure than the white men (p≤0.05). Only in the white men was free testosterone positively associated with retinal calibre, i.e. arterio-venular ratio and central retinal arterial calibre and inversely with central retinal venular calibre. These associations were not found in the black men, independent of whether pulse pressure and ocular perfusion pressure were part of the model. These results suggest an independent, protective effect of testosterone on the retinal vasculature where an apparent vasodilatory response in the retinal resistance microvessels was observed in white men.

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?

Suppression of inflammatory disease activity in rheumatoid arthritis is associated with improvements in retinal microvascular health

To investigate the effect of suppressing inflammation on retinal microvascular health in patients with RA. Two groups of patients with RA were recruited and studied concurrently. Group A included patients with moderate to high disease activity [28-joint DAS with CRP (DAS28-CRP) >3.2] requiring treatment escalation, while group B had stable low disease activity (DAS28-CRP ≤3.2) not requiring treatment escalation. Retinal photography was performed at baseline and weeks 6 and 24 in group A and at baseline and week 12 in group B. Group A included 26 patients with a mean age of 50.7 years (s.d. 3.5) and a mean disease duration of 7.1 years (s.d. 8.0). Disease activity significantly improved during follow-up and was accompanied by a significant reduction in retinal venular calibre at week 6 [mean difference (MD) -7.9 μm (95% CI -13.3, -2.5)] and at week 24 [MD -6.8 μm (95% CI -12.2, -1.4)]. No significant change in retinal arteriolar calibre was identified at week 6 [MD -0.6 μm (95% CI -4.5, 3.28)] or week 24 [MD 0.7 μm (95% CI -3.1, 4.5)]. Group B included 27 patients with a mean age of 54.6 years (s.d. 1.8) and a mean disease duration of 14.5 years (s.d. 10.9). Disease activity and therapy remained unchanged during follow-up and no significant changes in retinal venular [MD 1.81 μm (95% CI -2.32, 5.95)] or arteriolar [MD 0.54 μm (95% CI -2.77, 3.86)] calibre were observed. We demonstrated that suppression of inflammation in RA is associated with a reduction of retinal venular calibre, suggesting that therapies targeting inflammation could improve vascular health in RA.

Impact of maternal smoking during pregnancy on microvasculature in childhood. The Generation R Study

BackgroundFetal exposure to maternal smoking is associated with an adverse cardiovascular risk profile in later life. Early microvasculature adaptations might be part of the underlying mechanisms for these associations. AimsThe aim of this study was to examine the influence of maternal smoking during pregnancy on retinal vessel calibers in children. Study designWe performed a population-based prospective cohort study among 3564 school-age children. Maternal smoking patterns during pregnancy were assessed by questionnaires. Outcome measuresAt the median age of 6.0years (95% range 5.8, 8.0years), we measured childhood retinal vessel calibers from retinal photographs. ResultsNo differences were observed in childhood retinal arteriolar and venular calibers among offspring from mothers who smoked in the first trimester and mothers who continued smoking throughout pregnancy, as compared to mothers who did not smoke during pregnancy. Also, no dose-dependent associations of the number of cigarettes smoked during pregnancy with childhood retinal vessel calibers were present. ConclusionMaternal smoking during pregnancy did not influence childhood retinal arteriolar and venular calibers. The mechanisms linking fetal smoke exposure with cardiovascular risk factors in later life may include other mechanisms than structural microvasculature adaptations.

Retinal microvascular calibre and risk of diabetes mellitus: a systematic review and participant-level meta-analysis.

The calibre of the retinal vessels has been linked to diabetes mellitus but studies have not shown consistent results. We conducted a participant-level meta-analysis to evaluate the association between retinal arteriolar and venular calibre and diabetes. We performed a systematic review on MEDLINE and EMBASE for articles published up to December 2014. We identified five population-based prospective cohort studies that provided individual-level data on 18,771 diabetes-free participants. We used discrete time proportional hazards models to estimate pooled HRs of diabetes associated with 1 SD (20 μm) change in retinal vascular calibre. We identified 2,581 incident cases of diabetes over a median follow-up period of 10 years (interquartile interval of 3.4-15.8 years). After adjustment for demographic, lifestyle and clinical factors, retinal venular calibre was significantly associated with incident diabetes (pooled HR 1.09 [95% CI 1.02, 1.15] per SD increase in venular calibre). This association persisted in analyses excluding individuals with <5 years of follow-up (1.07 [1.0, 1.12]) or those with impaired fasting glucose at baseline (1.10 [1.03, 1.17]); in subgroup analyses, the association was stronger in men than in women but was consistent across subgroups of race/ethnicity, smoking status, hypertension and BMI categories. Retinal arteriolar calibre was not associated with diabetes (0.95 [0.86, 1.06] per SD decrease in arteriolar calibre). Wider retinal venules but not narrower retinal arterioles were associated with a modestly increased risk for diabetes. Knowledge of pathological mechanisms underlying wider retinal venule may provide further insights concerning microvascular alterations in diabetes.

Influence of breastfeeding on retinal vessel calibers in school-age children. The Generation R Study

A shorter breastfeeding duration is associated with an increased risk of cardiovascular disease in adulthood. Early microvasculature structure adaptations may be part of the underlying mechanism. We examined the associations of ever breastfeeding, breastfeeding duration and exclusivity, and the timing of introduction of solid foods with retinal vessel calibers in children. We performed a population-based prospective cohort study from fetal life onwards in the city of Rotterdam, the Netherlands. We obtained information on ever breastfeeding, breastfeeding duration and exclusivity, and age at introduction of solid foods from postal questionnaires at the ages of 2, 6 and 12 months after birth. At the median age of 6.0 years (90% range: 5.7-6.8), we measured retinal arteriolar and venular calibers from digitized retinal photographs among 3220 children. Grader-specific s.d. scores (SDS) for both central retinal and arteriolar equivalents were constructed. We observed that in the models only adjusted for child's age, sex and ethnicity, children who were never breastfed had narrower retinal arteriolar and venular calibers in childhood as compared with children who were breastfed (differences in retinal arteriolar and venular calibers, respectively: -0.16 SDS (95% confidence interval (CI): -0.29, -0.03) and -0.18 SDS (95% CI: -0.32, -0.04)). After additional adjustment for maternal and childhood socio-demographic and lifestyle-related characteristics, never breastfeeding was only associated with narrower retinal venular caliber (difference: -0.15 SDS (95% CI: -0.29, -0.02)). We did not observe associations of breastfeeding duration or exclusivity, or age at introduction of solid foods with retinal vessel calibers. Children who were never breastfed tended to have narrower retinal venular calibers. We did not observe associations of breastfeeding duration with retinal vessel calibers. Family-based socio-demographic factors, maternal lifestyle-related factors and childhood factors only slightly influenced the observed associations. These results should be considered a hypothesis generating for further observational and experimental studies.

Impact of birth parameters and early life growth patterns on retinal microvascular structure in children: The Generation R Study.

The aim of the study was to examine the associations of birth outcomes and longitudinally measured fetal and infant growth patterns with retinal vessel calibers in childhood. In a population-based prospective cohort study among 4122 children, we measured growth characteristics in second and third trimester of pregnancy, at birth, and at 6, 12, 24, 36, 48, and 72 months. At the age of 6 years, we measured retinal arteriolar and venular calibers from digitized retinal photographs. We observed that compared with term-born children, those born preterm had narrower retinal arteriolar caliber [differences -0.46 standard deviation score (95% confidence interval -0.77 to -0.15) and -0.24 standard deviation score (95% confidence interval -0.42 to -0.05) for children born <34 and 34-37 weeks of gestation, respectively]. Children born with a low birth weight (<2500 g) had narrower retinal arteriolar caliber than children with a normal birth weight, but this association was fully explained by gestational age at birth. Accelerated infant growth until 24 months was associated with narrow retinal arteriolar caliber, especially among preterm-born children (P < 0.05). Early growth measures were not associated with retinal venular caliber. Preterm birth and accelerated infant growth are associated with narrower retinal arteriolar caliber in childhood. Whether these microvascular adaptations explain the well known associations of fetal and infant characteristics with cardiovascular disease in later life should be further studied.

Body fat distribution, metabolic and inflammatory markers and retinal microvasculature in school-age children. The Generation R Study.

To examine the associations of body fatness, metabolic and inflammatory markers with retinal vessel calibers among children. We performed a population-based cohort study among 4145 school-age children. At the median age of 6.0 years (95% range 5.8, 8.0 years), we measured body mass index, total and abdominal fat mass, metabolic and inflammatory markers (blood levels of lipids, insulin and C-peptide and C-reactive protein) and retinal vascular calibers from retinal photographs. We observed that compared with normal weight children, obese children had narrower retinal arteriolar caliber (difference -0.21 s.d. score (SDS; 95% confidence interval (CI) -0.35, -0.06)), but not venular caliber. Continuous analyses showed that higher body mass index and total body fat mass, but not android/gynoid fat mass ratio and pre-peritoneal fat mass, were associated with narrower retinal arteriolar caliber (P<0.05 for body mass index and total body fat mass), but not with retinal venular caliber. Lipid and insulin levels were not associated with retinal vessel calibers. Higher C-reactive protein was associated with only wider retinal venular caliber (difference 0.10 SDS (95% CI 0.06, 0.14) per SDS increase in C-reactive protein). This latter association was not influenced by body mass index. Higher body fatness is associated with narrower retinal arteriolar caliber, whereas increased C-reactive protein levels are associated with wider retinal venular caliber. Increased fat mass and inflammation correlate with microvascular development from school-age onwards.

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Retinal microvasculature and cardiovascular health in childhood.

Alterations in retinal microvasculature are associated with increased risk of cardiovascular disease. We examined the associations of retinal vessel caliber with cardiovascular markers in school-age children. Among 4007 school-age children (median age of 6.0 years), we measured cardiovascular markers and retinal vessel calibers from digitized retinal photographs. Narrower retinal arteriolar caliber was associated with higher systolic and diastolic blood pressure (-0.20 SD score [SDS] [95% confidence interval (CI) -0.24 to -0.18] and -0.14 SDS [-0.17 to -0.11], respectively, per SDS increase in retinal arteriolar caliber), mean arterial pressure, and pulse pressure, but not with carotid-femoral pulse wave velocity, heart rate, cardiac output, or left ventricular mass. A wider retinal venular caliber was associated with lower systolic blood pressure, mean arterial pressure, and pulse pressure and higher carotid-femoral pulse wave velocity (carotid-femoral pulse wave velocity difference = 0.04 SDS [95% CI 0.01 to 0.07] per SDS increase in retinal venular caliber). Both narrower retinal arteriolar and venular calibers were associated with higher risk of hypertension at the age of 6 years, with the strongest association for retinal arteriolar caliber (odds ratio 1.35 [95% CI 1.21 to 1.45] per SDS decrease in arteriolar caliber). Adjustment for parental and infant sociodemographic factors did not influence the observed associations. Both retinal arteriolar and venular calibers are associated with blood pressure in school-age children, whereas retinal venular caliber is associated with carotid-femoral pulse wave velocity. Microvascular adaptations in childhood might influence cardiovascular health and disease from childhood onward.

Choroidal thickness and retinal vascular caliber correlations with internal carotid artery Doppler variables.

Decreased retinal arteriolar caliber and increased retinal venular caliber have been associated with increased cardiovascular mortality. This study aimed to evaluate correlations of choroidal thickness and retinal vascular caliber measurements with internal carotid artery (ICA) Doppler ultrasound variables. In this cross-sectional and observational study, 43 eyes and ICAs of 43 healthy volunteers were examined. Spectral domain optical coherence tomography was used to measure subfoveal choroidal thickness (SFCT) and retinal vascular caliber. The ICA Doppler ultrasonographic parameters were diameter, flow volume, peak-systolic velocity, end-diastolic velocity, resistance index (RI), and pulsatility index (PI). Negative correlations emerged between ICA RI and SFCT (p = 0.017, r = -0.36) as well as between ICA PI and retinal arteriolar caliber (p = 0.015, r = -0.37). A negative linear correlation appeared between ICA diameter and SFCT (p = 0.005, r = -0.42), although ICA diameter and flow volume showed no association with retinal vessel caliber (p > 0.05). Choroidal thickness is negatively correlated with ICA diameter and ICA RI, while retinal arteriolar caliber is inversely related with ICA PI in normal volunteers.

Early risk stratification in pediatric type 1 diabetes.

In the late 1980s all Danish children with type 1 diabetes were invited for a nationwide evaluation of glycemic control. Approximately 75% (n = 720) participated and have later been referred to as The Danish Cohort of Pediatric Diabetes 1987 (DCPD1987). The results were surprisingly poor glycemic control among these young patients which lead to a great emphasis on glycemic control in the Danish Pediatric Departments. In 1995 the participants were invited for yet another evaluation but this time with main focus on early signs of microvascular complications - 339 participated. The mean HbA1c had remained at high levels (9.6%) and 60% of the participants had some level of Diabetic Retinopathy (DR). However, as the patients with DR mostly had the very milder forms it was believed that stricter glycemic control would reverse or at least stop progression of the disease in accordance with results from the large intervention study DCCT. This was investigated further at follow-up in 2011. The first study in the present thesis aimed to describe the 16-year incidence, progression and regression of DR in 185 participants from the DCPD1987 cohort. The 16-year incidence of proliferative retinopathy (PDR), 2-step progression and regression of DR was 31.0, 64.4, and 0.0%, respectively. As expected, the participants with PDR at follow-up had significantly higher HbA1c-values at both baseline and follow-up than those without PDR. However; a significantly larger decrease in HbA1c was also observed in the group with PDR over the study period, which in accordance with DCCT should have prevented the development of PDR to some extent. A surprisingly high incidence of proliferative retinopathy amongst young patients with type 1 diabetes in Denmark was found despite improvements in HbA1c over time. The improvement in HbA1c was either too small or happened too late. This study highlights that sight-threatening diabetic retinopathy remain a major concern in type 1 diabetes and the importance of early glycemic control. Identifying high-risk patients at a very early stage is not only desired for prevention of diabetic retinopathy - neuropathy and nephropathy similarly remain frequent in type 1 diabetes. Early risk stratification will allow for timely implementation of effective interventions and for individualized screening and diabetes care. The second and third studies of this thesis provide the longest prospective studies to date on both retinal vessel calibers and retinal fractal dimensions and their predictive value on diabetic microvascular complications. Semi-automated computer software has been developed to measure smaller changes in the retinal vessels on retinal photographs. Two of the first parameters to be reliably estimated by these programs were retinal vessel calibers and retinal vascular fractal dimensions (a quantitative measure on vascular complexity). There is very limited knowledge on their predictive value on diabetic complications thus far. In the second and third study, a consistent relation between narrower retinal arteriolar calibers, wider retinal venular calibers, lower fractal dimensions and the 16-year incidences of diabetic neuropathy, nephropathy and proliferative retinopathy was found. This has never been shown before. The results on vessel analyzes provides indications of a common pathogenic pathway for diabetic microvascular complications and therefore a possibility of universal risk estimation for development of neuropathy, nephropathy and retinopathy in type 1 diabetes.

Influence of maternal angiogenic factors during pregnancy on microvascular structure in school-age children.

Reduced placental growth factor (PlGF) levels and higher soluble fms-like tyrosine kinase (sFlt-1) levels in mothers during pregnancy may have persistent effects on vascular structures in their offspring. We examined whether angiogenic factors during pregnancy also affect childhood retinal microvasculature in a population-based prospective cohort study among 3505 mothers and their children. We measured maternal PlGF and sFlt-1 in the first and second trimester of pregnancy. At the age of 6, we measured childhood retinal arteriolar and venular calibers from digitized retinal photographs. We performed multiple linear regression models, taking maternal and childhood sociodemographic and lifestyle-related characteristics, birth characteristics, and childhood current body mass index and blood pressure into account. We observed that first trimester maternal PlGF and sFlt-1 levels were not associated with childhood retinal arteriolar caliber. Lower second trimester maternal PlGF levels, but not sFlt-1 levels, were associated with narrower childhood retinal arteriolar caliber (difference: -0.09 SD score [95% confidence interval, -0.16 to 0.01], per SD score decrease in PlGF). This association was not explained by maternal and childhood sociodemographic and lifestyle-related characteristics, birth characteristics, or childhood current body mass index and blood pressure. Maternal PlGF and sFlt-1 levels in the first or second trimester were not associated with childhood retinal venular caliber. Our results suggest that lower maternal second trimester PlGF levels affect the microvascular development in the offspring, leading to narrower retinal arteriolar caliber in childhood. Further studies are needed to confirm these findings and to explore the underlying mechanisms and long-term cardiovascular consequences.

Retinal microvascular abnormalities and risk of renal failure in Asian populations.

BackgroundRetinal microvascular signs may provide insights into the structure and function of small vessels that are associated with renal disease. We examined the relationship of retinal microvascular signs with both prevalent and incident end-stage renal disease (ESRD) in a multi-ethnic Asian population.MethodsA total of 5763 subjects (aged ≥40 years) from two prospective population-based studies (the Singapore Malay Eye Study and the Singapore Prospective Study) were included for the current analysis. Retinopathy was graded using the modified Airlie House classification system. Retinal vascular parameters were measured using computer-assisted programs to quantify the retinal vessel widths (arteriolar and venular caliber) and retinal vascular network (fractal dimension). Data on ESRD was obtained by record linkage with the ESRD cases registered by National Registry of Diseases Office, Singapore. Multi-variable adjusted regression analyses were performed to assess the associations of baseline retinal vascular parameters and prevalent and incident ESRD.ResultsAt baseline, 21(0.36%) persons had prevalent ESRD. During a median follow-up of 4.3 years, 33 (0.57%) subjects developed ESRD. In our analyses, retinopathy was associated with prevalent ESRD (multi-variable adjusted odds ratio [OR], 3.21, 95% confidence interval [CI]: 1.28–8.05) and incident ESRD (multi-variable adjusted hazard ratio [HR], 2.51, 95%CI: 1.14–5.54). This association was largely seen in person with diabetes (HR, 2.60, 95%CI: 1.01–6.66) and not present in persons without diabetes (HR, 1.65, 95%CI: 0.14–18.98). Retinal arteriolar caliber, retinal venular caliber and retinal vascular fractal dimension were not associated with ESRD.ConclusionRetinopathy signs in persons with diabetes are related to an increased risk of ESRD; however, other microvascular changes in the retina are not associated with ESRD.

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

Diabetic macular ischaemia (DMI) is an important cause of visual loss in patients with diabetes, but its relationship to the larger retinal vessels is unknown. We examined whether retinal vessel calibre is related to DMI. Clinic-based case-control study of patients with type 2 diabetes. The presence and severity of DMI was assessed using Early Treatment Diabetic Retinopathy Study (ETDRS) protocols from fundus fluorescein angiographic (FFA) images. Custom software was used to quantify the greatest linear dimension and area of the foveal avascular zone (FAZ). Retinal vessel calibre was measured using a semi-automated software on fundus fluorescein images. Of 53 patients examined, 18 (34%), 18 (34%) and 17 (32%) had no/mild, moderate and severe DMI, respectively. Persons with moderate or severe DMI had narrower mean retinal arteriolar calibre than persons with no/mild DMI (140.6 μm 95% confidence interval (CI) 134.7, 146.4 versus 150.7 μm, 95% CI 142.5, 158, p = 0.04). The association remained after multivariate adjustment for age, gender, previous panretinal photocoagulation, neovascularization at the disc and elsewhere and diabetic retinopathy severity. Increased FAZ size was also associated with narrower arteriolar calibre. Retinal venular calibre and arteriole to venule ratio (AVR) were not associated with DMI. Retinal arteriolar narrowing was associated with moderate-to-severe macular ischaemia in eyes with diabetic retinopathy. This suggests that larger vessels other than capillaries may also be associated with DMI.

Retinal arteriolar narrowing and incidence of knee replacement for osteoarthritis: a prospective cohort study

The role of the microcirculation in the pathogenesis of osteoarthritis (OA) remains unclear. This prospective cohort study examined the association between retinal vascular calibre and incidence of knee replacement for OA. 1838 participants of the Australian Diabetes, Obesity and Lifestyle (AusDiab) Study had retinal vascular calibre measured using a nonmydriatic digital fundus camera in 1999-2000 and were aged ≥ 40 years at joint replacement data collection commencement. The incidence of knee replacement for OA during 2002-2011 was determined by linking cohort records to the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). 77 participants underwent knee replacement for OA. They had narrower retinal arteriolar calibre compared with those without knee replacement (166.1 ± 24.8 μm vs 174.3 ± 24.5 μm, P = 0.004). For every one standard deviation reduction in retinal arteriolar calibre, the incidence of knee replacement increased by 25% (HR 1.25, 95% confidence interval (CI) 1.00-1.56). Participants in the narrower two-thirds of arteriolar calibre had twice the risk of knee replacement compared with those in the widest one-third (HR 2.00, 95% CI 1.07-3.74, P = 0.03) after adjustment for sex, body mass index (BMI), physical activity and HbA1c. There was no association for retinal venular calibre. Retinal arteriolar narrowing is associated with increased risk of knee replacement for OA suggesting that further work is warranted to determine the role of the microcirculation in the pathogenesis of knee OA.

Analysis of retinal vessels in eyes with retinitis pigmentosa by retinal oximeter.

To study changes in the oxygen saturation and calibre of retinal vessels in the eyes of patients with retinitis pigmentosa (RP). In this cross-sectional study, 63 eyes of 63 patients with RP and 14 eyes of 14 healthy subjects were enrolled and examined at Toyama University Hospital. Retinal oximetry measurements were performed using a spectrophotometric oximetry unit (Oxymap T1, Reykjavik, Iceland), which is coupled to a fundus camera base (TRC-50DX; Topcon Corporation, Tokyo, Japan). Retinal arterioles of 28 eyes and retinal venules of 35 eyes with adequate image quality were selected for analyses. We calculated the residual areas of visual field (I-4e and V-4e isopters) in each eye and determined the correlations between the data of retinal vessels and the areas of visual field in the RP eyes. The mean oxygen saturation of the venules in the RP eyes (60.2 ± 6.5%) was significantly higher than that in healthy eyes (54.6 ± 6.3%, p = 0.0089). The oxygen saturation of the venules in the RP eyes correlated significantly with the residual areas of the visual field of V-4e (r = -0.50; p = 0.0030). The mean calibres of the retinal arterioles (91.1 ± 9.1 μm) and retinal venules (116 ± 13 μm) of the RP eyes were significantly narrower than those of the healthy eyes (115 ± 11 μm and 152 ± 15 μm, respectively, p < 0.01). The retinal arteriolar and venular calibres in the RP eyes correlated with the residual areas of the visual field of V-4e (r = 0.43; p = 0.033 and r = 0.45; p = 0.011, respectively). The severity of RP was correlated with increased oxygen saturations in the retinal venules and decreased retinal vessel calibres.

The Relationship between Changes in Body Mass Index and Retinal Vascular Caliber in Children

To examine the longitudinal relationship between changes in childhood body mass index (BMI) and retinal vascular caliber. A prospective study of 421 healthy children aged 7-9 years in 2001 who returned for follow-up in 2006. At both visits, retinal photographs and anthropometric measurements were taken following standardized protocols. Retinal arteriolar and venular calibers were measured using a computer-based program and summarized as central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE). At follow-up, mean weight, height, and BMI increased significantly (P < .001). Mean CRVE increased by 3.4 μm (P < .001) but mean CRAE did not alter significantly (P = .340). On multivariate analysis, greater BMI was cross-sectionally associated with narrower CRAE (P < .01) and wider CRVE (P < .01). On longitudinal analysis, increasing BMI was associated with increasing CRVE (P = .04) over the 5-year period. Baseline BMI was associated with increased venular caliber and decreased arteriolar caliber at follow-up, and vice versa (P < .05). Increasing BMI is associated with increasing retinal venular caliber over time in children, and baseline retinal vascular caliber changes increase the risk of higher BMI at follow-up. As both widened retinal venular caliber and greater BMI are associated with risk of cardiovascular events in adults, progressive retinal venular widening could be a manifestation of an adverse microvascular effect of obesity early in life.

Complete blood count and retinal vessel calibers.

ObjectiveThe influence of hematological indices such as complete blood count on microcirculation is poorly understood. Retinal microvasculature can be directly visualized and vessel calibers are associated with a range of ocular and systemic diseases. We examined the association of complete blood count with retinal vessel calibers.MethodsCross-sectional population-based Blue Mountains Eye Study, n = 3009, aged 49+ years. Complete blood count was measured from fasting blood samples taken at baseline examination, 1992–4. Retinal arteriolar and venular calibers were measured from digitized retinal photographs using a validated semi-automated computer program.ResultsAll analyses adjusted for age, sex, systolic blood pressure, diabetes, smoking and fellow vessel caliber. Higher hematocrit, white cell count and platelet count were associated with narrower arteriolar caliber (p = 0.02, 0.03 and 0.001 respectively), while higher hemoglobin, hematocrit, red cell count, white cell count and platelet count were associated with wider venular caliber (p<0.0001 for all). Each quintile increase in hematocrit, white cell count and platelet count was associated with approximately 0.5 µm narrower arteriolar caliber; whereas each quintile increase in all of the complete blood count components was associated with approximately 1–2 µm wider venular caliber.ConclusionsThese associations show that elevated levels of hematological indices can have adverse effects on the microcirculation.

Associations between retinal microvascular structure and the severity and extent of coronary artery disease

ObjectiveMicrovascular mechanisms are increasingly recognized as being involved in a significant proportion of coronary artery disease (CAD) cases, but their exact contribution or role is unclear. We aimed to define the association between retinal microvascular signs and both CAD extent and severity. Methods1120 participants of the Australian Heart Eye Study were included. Retinal vessel caliber was measured from digital retinal images. Extent and severity of CAD was assessed using several approaches. First, a simple scoring classifying participants as having one-vessel, two-vessel, and three-vessel disease was used. Gensini and Extent scores were calculated using angiography findings. ResultsAfter multivariable adjustment, significantly narrower retinal arteriolar caliber in women (comparing lowest versus highest quartile or reference) and wider venular caliber in men (comparing highest versus lowest quartile or reference) were associated with 2-fold and 54% higher odds of having at least one stenosis ≥50% in the epicardial coronary arteries, respectively. Women in the third versus first tertile of retinal venular caliber had 92% and ∼2-fold higher likelihood of having higher Gensini and Extent scores, respectively. Women in the lowest versus highest tertile of retinal arteriolar caliber had greater odds of having higher Extent scores, OR 2.99 (95% CI 1.45–6.16). In men, non-significant associations were observed between retinal vascular caliber and Gensini and Extent scores. ConclusionsAn unhealthy retinal microvascular profile, namely, narrower retinal arterioles and wider venules was associated with more diffuse and severe CAD among women.