Central Retinal Vein Equivalent Research Articles

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

AimsTo investigate changes in retinal vessel diameter during acute hyperglycemia in patients with type 1 diabetes. MethodsWe 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. ResultsIn 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. ConclusionsWe 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.

A new unified framework for the early detection of the progression to diabetic retinopathy from fundus images

Human retina is a diverse and important tissue, vastly studied for various retinal and other diseases. Diabetic retinopathy (DR), a leading cause of blindness, is one of them. This work proposes a novel and complete framework for the accurate and robust extraction and analysis of a series of retinal vascular geometric features. It focuses on studying the registered bifurcations in successive years of progression from diabetes (no DR) to DR, in order to identify the vascular alterations. Retinal fundus images are utilised, and multiple experimental designs are employed. The framework includes various steps, such as image registration and segmentation, extraction of features, statistical analysis and classification models. Linear mixed models are utilised for making the statistical inferences, alongside the elastic-net logistic regression, boruta algorithm, and regularised random forests for the feature selection and classification phases, in order to evaluate the discriminative potential of the investigated features and also build classification models. A number of geometric features, such as the central retinal artery and vein equivalents, are found to differ significantly across the experiments and also have good discriminative potential. The classification systems yield promising results with the area under the curve values ranging from 0.821 to 0.968, across the four different investigated combinations.

Effects of intravitreal aflibercept and ranibizumab on retinal vessel diameter measured using fluorescein angiography

PurposeTo investigate the effect of intravitreal (IVT) aflibercept and ranibizumab on retinal vessel diameter in patients with neovascular age‐related macular degeneration (N‐AMD).MethodsForty eyes of 40 consecutive participants with treatment‐naïve N‐AMD were included. Two groups of 20 eyes received three consecutive monthly treatments of IVT aflibercept or ranibizumab. Retinal vessel diameter was measured using fluorescein angiography (FA) before the first IVT injection and 1 month after the third injection. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were calculated to represent average retinal vessel diameters.ResultsRetinal vessel diameter significantly decreased in aflibercept‐treated patients; CRAE and CRVE reduced from 106.7 ± 22.9 μm to 96.1 ± 24.1 μm (P = 0.028) and from 148.8 ± 19.6 μm to 140.8 ± 19.6 μm (P = 0.003), respectively. Pre‐injection and post‐injection arteriovenous ratios were 0.71 ± 0.08 and 0.71 ± 0.11, respectively (P = 0.733). However, retinal vessel diameter was not significantly reduced in ranibizumab‐treated patients; CRAE changed from 107.1 ± 23.3 μm to 104.4 ± 22.0 μm (P = 0.073) and CRVE from 139.0 ± 13.8 μm to 139.2 ± 14.2 μm (P = 0.794). Pre‐injection and post‐injection arteriovenous ratios in the ranibizumab‐treated group were 0.74 ± 0.14 and 0.72 ± 0.14, respectively (P = 0.163).ConclusionsIVT aflibercept treatment had a significant vasoconstrictive effect in eyes treated for N‐AMD; on the other hand, IVT ranibizumab did not significantly affect retinal vessel diameter. The aflibercept‐mediated reduction in diameter was not vessel‐specific.

Retrospective analysis of the effect of aflibercept loading dose on the retinal vessel diameters in patients with treatment-naive neovascular AMD

Background: To evaluate the effects of intravitreal aflibercept (IVA) on retinal vessel diameters in patients with neovascular age-related macular degeneration (AMD).Design, setting, and participants: A retrospective study conducted at the Kutahya Dumlupinar University Faculty of Medicine included 15 eyes of 15 patients with treatment naive neovascular AMD.Methods: All eyes received IVA injections once per month for 3 months; untreated contralateral eyes were used as controls. The central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and artery-vein ratio (AVR) values were measured using a computer-based program before the first IVA injection and 30 days after the first, second, and third injections. The main outcome measurements were the central macular thickness (CMT), best-corrected visual acuity (BCVA), choroidal thickness, CRAE, CRVE, and AVR.Results: Significant vasoconstriction of the retinal arterioles was observed in all eyes treated with IVA when compared to baseline (p = 0.009). However, no significant differences were found for CRVE or AVR throughout the study period in treated eyes. In the control group, all parameters measured during each visit were similar to baseline measurements (p > 0.05). The mean BCVA significantly improved at the end of the loading dose of IVA, when compared to baseline (p = 0.006). After the IVA injections, the mean CMT and choroidal thickness were significantly reduced at all visits, compared to baseline (p < 0.001).Conclusions: The current study showed that IVA led to significant retinal arteriolar vasoconstriction and choroidal thinning, which may cause reduced retinal blood flow.

Comparative Retinal Vessel Size Study of Intravitreal Ranibizumab and Bevacizumab in Eyes with Neovascular Age-Related Macular Degeneration

Purpose: The aim of this paper was to assess and compare the effects of intravitreal ranibizumab and bevacizumab on retinal vessel diameter in eyes with neovascular age-related macular degeneration (AMD). Methods: Patients with neovascular AMD who underwent intravitreal injection of either ranibizumab or bevacizumab were included. Noninjected fellow eyes served as a control. The main outcome measures were central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and the artery-vein ratio (AVR). Results: In the ranibizumab group, the mean CRAE value decreased significantly at 1 week and 1 month (p = 0.002). The AVR value decreased significantly at 1 month (p = 0.028). CRVE values did not change at 1 week and 1 month (p = 0.083). In the bevacizumab group, the preinjection CRAE, CRVE, and AVR values did not change through the study period (p = 0.128, p = 0.600, and p = 0.734, respectively). Conclusion: These results suggest that intravitreal ranibizumab led to significant retinal arteriolar vasoconstriction in eyes with neovascular AMD.

Retinal vessel diameters and reactivity in diabetes mellitus and/or cardiovascular disease

BackgroundRetinal vessel calibre and vascular dilation/constriction in response to flicker light provocation may provide a measure distinguishing patients suffering from diabetes mellitus and/or cardiovascular disease.MethodsOne hundred and sixteen age and sex matched patients with diabetes mellitus (DM), cardiovascular disease (CVD) and both DM and CVD (DM + CVD) underwent systemic and intraocular pressure measurements. Retinal vessel calibres were assessed using a validated computer-based program to compute central retinal artery and vein equivalents (CRVE) from monochromatic retinal images. Vessel dilation and constriction responses to flicker light provocation were assessed by continuous retinal vessel diameter recordings. Plasma endothelial markers von Willebrand factor (vWf) and soluble E selectin (sEsel) were measured by ELISA.ResultsRetinal vessel calibres were comparable across groups but CRVE correlated significantly with disease duration in DM patients (r = 0.57, p < 0.001). Patients suffering DM only exhibited reduced arterial vasomotion at rest and reduced arterial constriction following flicker light induced vessel dilation compared to patients with CVD and those suffering both CVD + DM (p = 0.030). Patients suffering from CVD + DM exhibited significant differences between each flicker cycle in regards to arterial maximum constriction (p = 0.006) and time needed to reach arterial maximum dilation (p = 0.004), whereas the other two groups did not show such inconsistencies between individual flicker cycles. vWf was raised in CVD + DM compared to the other two groups (p ≤ 0.02), whilst sEsel was raised in CVD + DM compared to DM alone (p = 0.044).ConclusionsDynamic retinal vascular calibres as obtained by continuous diameter measurements using flicker light provocation can reveal subtle differences between groups suffering from CVD with and without DM. This difference in reaction pattern and lack of arterial constriction in DM may provide a suitable marker to monitor progression.

Retinal Vascular Morphological Changes in Patients with Extremely Severe Obstructive Sleep Apnea Syndrome.

Background:Obstructive sleep apnea syndrome (OSAS) has been shown to generate hypertension and endothelial dysfunction. Retinal vessel is the only vessel that can be observed directly and noninvasively; retinal vascular abnormalities can serve as a predictive marker for the occurrence, clinical course, and prognosis of cardiovascular and cerebrovascular diseases. The objective of this study was to identify the effect of OSAS severity on the morphological changes of retinal vessels.Methods:Adult patients complained of snoring were included in this study. The patients’ general information, polysomnography, and fundus photography parameters including central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole-to-venule ratio (AVR) were collected. Patients were divided into four groups according to their apnea-hypopnea index (AHI) results: Group I, AHI ≤5/h; Group II, 5/h < AHI ≤30/h; Group III, 30/h < AHI ≤60/h; and Group IV, AHI >60/h.Results:A total of 133 patients were included in this study with 111 males (83.5%) and 22 females (16.5%). Mean age was 41.6 ± 9.9 years, and the mean body mass index was 28.1 ± 4.0 kg/m2. AHI ranged between 0 and 130.8/h with a mean of 39.1 ± 30.7/h. There were 24, 34, 35, and 40 patients in Group I, Group II, Group III, and Group IV, respectively. Significant differences were found for AHI (F = 388.368, P < 0.001), minimal pulse oxygen saturation (F = 91.902, P < 0.001), and arousal index (F = 31.014, P < 0.001) among four groups; no significant differences were found for CRAE (F = 0.460, P = 0.599) and CRVE (F = 0.404, P = 0.586) among groups; there were significant differences for AVR between Group I and Group IV (63.6 ± 5.1% vs. 67.2 ± 5.5%, P = 0.010) Group II and Group IV (64.5 ± 6.0% vs. 67.2 ± 5.5%, P = 0.030), and Group III and Group IV (64.7 ± 4.1% vs. 67.2 ± 5.5%, P = 0.043). A main group-by-AHI effect was found on the AVR: patients with higher AHI showed higher AVR results (r = 0.225, P = 0.009). Multivariate logistic regression analysis was used for multi-variable factors. A group-by-age effect was found on the AVR: younger patients showed higher AVR results (β = −0.001, P = 0.020).Conclusions:This study indicated that increased AVR of retinal vessel can be observed in extremely severe OSAS patients. For patients with OSAS, retinal vascular abnormalities may become an early indication for further cardiovascular abnormalities.

Vessel diameter study: intravitreal vs posterior subtenon triamcinolone acetonide injection for diabetic macular edema.

PurposeTo detect and compare the vessel diameter effect of intravitreal vs subtenon injection of triamcinolone for diabetic macular edema (DME).MethodsSixty patients with DME who underwent triamcinolone injection either intravitreally (N=30) or under the tenon capsule (N=30) were included. Non-injected fellow eyes served as control. The main outcome measures were central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and artery-vein ratio (AVR).ResultsIn the intravitreal group, pre-injection mean CRAE (147.07 μ) decreased to 141.03 μ at 1 week and to 139.43 μ at 1 month (P<0.001) while baseline CRVE (209.61 μ) decreased initially to 198.85 μ at 1 week then to 198.49 μ at 1 month (P<0.001). In the subtenon group, pre-injection CRAE (152.18 μ) decreased to 149.49 μ at 1 week and to 147.47 μ at 1 month (P=0.017), while baseline CRVE (215.60 μ) decreased initially to 208.69 μ at 1 week then to 207.25 μ at 1 month (P=0.003). Pre-injection AVR values did not change at 1 week and at 1 month in both injection groups (P=0.66 and P=0.196, respectively). In the control group, none of the 3 parameters changed throughout the study period compared to the baseline (P>0.28).ConclusionIn eyes with DME, both intravitreal and subtenon triamcinolone injection led to a significant constriction of retinal arteries and veins.

Retinal vascular changes after vitrectomy for idiopathic epiretinal membrane: a pilot study with dynamic vessel analysis.

To investigate, using the Dynamic Vessel Analyzer (DVA), the retinal vascular changes that may occur after vitrectomy for idiopathic epiretinal membrane (ERM). Twenty-six eyes of 13 patients affected by unilateral idiopathic ERM were prospectively analyzed. 13 fellow eyes were used as control. The static (central retinal artery and vein equivalents) and dynamic (after flicker light stimulus) DVA analysis was performed at baseline (1day before surgery) and 6months after vitrectomy. The static DVA analysis did not highlight any significant change between investigational eyes and controls at baseline and 6months after surgery. The DVA dynamic analysis showed similar arterial flicker response between cases and controls at baseline (p = 0.3396), but disclosed a significant reduction of the arterial flicker response after surgery in the study eyes compared to fellow eyes (p = 0.0024). No significant changes were appreciated in the venous flicker response after surgery between cases and controls, both at baseline (p = 0.3450) and at the follow-up examination (p = 0.4214). The physiological flicker-induced vasoconstriction is reduced after vitrectomy in arteries. The oxygen saturation change occurring after vitrectomy might have a role in the vascular tone modification.

Retinal vascular calibre changes after intravitreal bevacizumab or dexamethasone implant treatment for diabetic macular oedema

PurposeTo compare changes in retinal vascular calibre after 2 years of treatment with intravitreal bevacizumab (BVZ) or dexamethasone implant (DEX) in patients with centre-involving diabetic macular oedema (DMO).MethodsAt baseline, 88...

Ocular Image and Haemodynamic Features Associated with Different Gradings of Ipsilateral Internal Carotid Artery Stenosis.

Objectives To analyse the changes of ocular haemodynamics and morphology in Chinese patients with internal carotid artery (ICA) stenosis in the current study. Methods A retrospective case-control study was conducted with 219 patients. The haemodynamic characteristics, the calibre of retinal vessels, and the subfoveal choroidal thickness (SFChT) were compared. We analysed the correlations with the degree of ipsilateral ICA stenosis. Results There were no significant differences among the groups in the central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and AVR (p = 0.073, p = 0.188, and p = 0.738, resp.). The peak systolic velocity (PSV) and end diastolic velocity (EDV) in the central retinal artery (CRA) and the posterior ciliary artery (PCA) were significantly lower than normal eyes (p < 0.001). The outer retinal layer thickness and SFChT values of the ICA stenosis groups were significantly lower than normal eyes (p = 0.030 and p < 0.001, resp.). Conclusion The PSV and EDV in CRA and PCA and the SFChT and outer retinal layer thickness of ICA eyes were significantly lower than normal eyes. ICA stenosis may impact choroidal haemodynamics, and decreased choroidal circulation might affect the discordance of the SFChT and the outer retinal layer thickness.

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

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. 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. 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). 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 vessels caliber changes after strabismus surgery: results of 6mo follow-up.

To evaluate the effect of strabismus surgery on retinal vessels calibers with digital color fundus photographs. Two hundred consecutive strabismus patients underwent surgery, and 118 patients (female/male, 55/63) who finished 6-month follow-up were finally included in this study. Optic disc-centered digital color fundus photographs of both eyes of all patients were taken prior to surgery and 6mo post surgery. The retinal vascular caliber of 116 operated eyes were measured using the computer program IVAN. The operated eyes were divided into 3 groups according to the surgical methods, recession of one muscle, one muscle recession and one muscle folding, one muscle resection and one muscle recession. The effect of number of altered muscles on retinal vessels was analyzed using statistic software SPSS 16.0. The mean age was 12.4±8.6y. Averaged central retinal artery equivalent (CRAE) of all patients was 120.31±23.02 µm preoperatively, and 122.87±15.93 µm six months after surgery. Averaged central retinal vein equivalent (CRVE) was 171.11±31.73 µm preoperatively and 175.02±21.00 µm postoperatively. There was no significant difference of averaged CRAE (P=0.22) or CRVE (P=0.19) before and after operation. Averaged arteriole to venule ratio (AVR) was 0.71±0.07 before surgery and 0.70±0.07 after surgery. Comparison of preoperative and postoperative retinal vessels calibers among different surgical groups did not show significant differences. Also, there was no advantage of rectus muscle folding to muscle resection. Up to 6mo after strabismus surgery, the retinal vascular calibers were not altered. No more than two muscles in one surgery are safe for retinal perfusion.

Alterations of retinal vessel size after single injection of intravitreal anti‐VEGF for diabetic macular edema

PurposeTo determine the affect of single injection of intravitreal anti‐vascular endothelial growth factor on the retinal vessel caliber in eyes with diabetic macular edema.MethodsOverall 32 patients were enrolled in ranibizumab group, 30 patients were included in bevacizumab group. Each of these groups also was divided into two others consisting of study group and control group. The study groups were composed of injected eyes while the non‐injected fellow eyes served as control group. The patients underwent complete ophthalmic examinations including optical coherence tomography and fundus fluorescein angiography. The primary outcome measures were central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE) and artery‐to‐vein ratio (AVR).ResultsIn ranibizumab study group (n = 32), pre‐injection mean CRAE (175.42 μm) decreased to 169.01 μm at one week and to 167.47 μm at one month (p &lt; 0.001) while baseline CRVE (235.29 μm) decreased initially to 219.90 μm at one week then to 218.36 μm at one month (p &lt; 0.001). In bevacizumab study group (n = 30), pre‐injection CRAE (150.21 μm) decreased to 146.25 μm at one week and to 145.89 μm at one month (p &lt; 0.001) while baseline CRVE (211.87 μm) decreased initially to 204.59 μm at one week then to 205.24 μm at one month (p &lt; 0.001). Pre‐injection AVR values changed significantly (p = 0.001) at one week and at one month in ranibizumab group, but no significant alteration of AVR was observed in bevacizumab group (p = 0.433). In the control groups of both ranibizumab (n = 32) and bevacizumab (n = 30), none of the three parameters altered throughout the study period compared to the baseline (p &gt; 0.05).ConclusionsBoth ranibizumab and bevacizumab injection significantly constricted retinal vessel diameters in eyes with diabetic macular edema.

Vessel diameter study: intravitreal versus posterior subtenon triamcinolone acetonide injection for diabetic macular edema

PurposeTo detect and compare the vessel diameter effect of intravitreal versus subtenon injection of triamcinolone for diabetic macular edema (DME).MethodsSixty patients with DME who underwent triamcinolone injection either intravitreally (N = 30) or under the tenon capsule (N = 30) were included. Non‐injected fellow eyes served as control. The main outcome measures were central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and artery‐vein ratio (AVR).ResultsIn the intravitreal group, pre‐injection mean CRAE (147.07μ) decreased to 141.03 μ at 1 week and to 139.43 μ at 1 month (p &lt; 0.001) while baseline CRVE (209.61 μ) decreased initially to 198.85 μ at 1 week then to 198.49 μ at 1 month (p &lt; 0.001). In the subtenon group, pre‐injection CRAE (152.18 μ) decreased to 149.49 μ at 1 week and to 147.47 μ at 1 month (p = 0.017) while baseline CRVE (215.60 μ) decreased initially to 208.69 μ at 1 week then to 207.25 μ at 1 month (p = 0.003). Pre‐injection AVR values did not change at 1 week and at 1 month in both injection groups (p = 0.66 and p = 0.196, respectively). In the control group, none of the 3 parameters changed throughout the study period compared to the baseline (p &gt; 0.28).ConclusionsIn eyes with DME, both intravitreal and subtenon triamcinolone injection led to a significant constriction of retinal arteries and veins

Static retinal vessel analysis in routine optometric practice

PurposeTo evaluate the use of objective retinal vessel calibre measurements in optometric practice and its utility in clinical decision making.MethodsA sub‐sample [n = 56] was extracted from a prospective study including patients booked for routine eye examinations in optometric practice. All participants underwent a standard examination including subjective refraction and slit lamp biomicroscopy. Undilated fundus photography and/or optical coherence tomography (OCT) was also performed. Optic nerve‐centred (camera angle: 50 degrees), red‐free photographs were analysed using VesselMap software (Imedos, Germany) to give objective vessel calibre measurements (central retinal artery and vein equivalents (CRAE / CRVE)).ResultsMean age of the cohort was 56 years (range: 21–82 years; consisting of 32 women and 24 men). Univariate analysis showed a significant association between systolic blood pressure and CRAE which was lost in multivariate analysis (p = 0.02). Stepwise forward multiple regression analysis found age to be significantly, negatively associated with CRAE (CRAE: 157au (SD ± 20); β = −0.54; p &lt; 0.001) and CRVE (β = −0.56; p &lt; 0.001), whereas BMI was positively associated with CRVE (198au (SD ± 20) au; β = 1.84; p = 0.005) only. Two patients were measured twice: on initial presentation, one with a significant retinal haemorrhage and one with unilateral papilloedema; both showed normalisation of vessel diameters on follow up.ConclusionsParticipants with the largest CRVE had the highest BMI and/or were diabetic. Cross‐sectional results from this sample are in agreement with results published from large cohort studies, including the negative association with age and CRAE. Retinal vessel calibres can help provide information on a patient's vascular system and systemic health, and therefore be a useful tool to refine optometric referrals and aid patient monitoring.

Relationship of retinal vascular caliber variation with intracranial arterial stenosis

Background & purposeTo investigate the associations of retinal vessel parameters with intracranial arterial stenosis (ICAS) assessed by Transcranial Doppler ultrasonography. MethodData on transcranial Doppler ultrasonography and quantitative retinal vessel parameters from 627 participants in a health screening program were included in this study. ICAS was defined as >50% intracranial arterial stenosis (ICAS) based on criteria modified from the stroke outcomes and neuroimaging of intracranial atherosclerosis (SONIA) trial assessed by transcranial Doppler (TCD) ultrasonography. A semi-automated computer-assisted program (Singapore I Vessel Assessment) was used to measure the retinal vascular parameters from the photographs. Multivariate analysis was performed to identify which retinal vessel parameters were associated with increased risk of ICAS. ResultsAmong 627 participants, 24 (3.8%) had ICAS diagnosed by TCD. Subjects with ICAS had eyes with wider mean central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) in comparison to subjects without ICAS. Men (odds ratio [OR]:13.1, 95% confidence interval: 3.13–33.33) and a large standard deviation of mean arterial width (STDWa) were associated with ICAS (first vs. third tertile: OR ratio: 14.04, 95% confidence interval: 1.71–115.32; first vs. third tertile: OR ratio: 22.1, 95% confidence interval: 2.56–190.97) after adjusting for possible confounders. ConclusionA large variation in retinal arteriolar diameter is associated with ICAS. This study suggests the possible relationship between retina vessel and early changes within the cerebrovascular network.

Retinal vessel caliber and its relationship with nocturnal blood pressure dipping status: the SABPA study.

Adverse changes in retinal microvasculature caliber are associated with incident hypertension, coronary heart disease and stroke. The absence of a nocturnal dipping in arterial pressure may induce changes throughout the vascular tree, including the retinal microvasculature, but the later link is not sufficiently studied. We explored the relationship between retinal vessel caliber and dipping status in a group of black and white teachers. The study included black (n=68) and white (n=81) men (24-66 years) from the SABPA study. We measured 24 h ambulatory blood pressure and the percentage mean arterial pressure dipping(%MAPdip) was calculated as (diurnal MAP-nocturnal MAP)/diurnal MAP × 100. Retinal images were captured and the central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) calculated. Black men demonstrated higher diurnal and nocturnal MAP (P⩽0.001) and a lesser %MAPdip compared with white men (P=0.047). When stratified by dipping status, black non-dippers (n=33) revealed an increased CRVE (P<0.001) compared with their dipper counterparts (n=35). In black men, CRVE was negatively (R2=0.38, β=-0.47, P<0.001) associated with %MAPdip independent of 24 h MAP or nocturnal MAP. CRVE also associated negatively with dipping status as a dichotomized variable (R2=0.29, β=-0.32, P=0.006), independent of 24 h MAP. These associations were absent in the white men. In conclusion, in this group of black men, a non-dipping blood pressure profile was associated with a larger CRVE, suggesting microvascular deterioration due to the absence of nocturnal dipping in blood pressure. This may add to our understanding of the stroke risk in black populations.

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

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. This was a hospital-based cross-sectional study. 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. 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. 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.

Summarising the retinal vascular calibres in healthy, diabetic and diabetic retinopathy eyes

Retinal vessel calibre has been found to be an important biomarker of several retinal diseases, including diabetic retinopathy (DR). Quantifying the retinal vessel calibres is an important step for estimating the central retinal artery and vein equivalents. In this study, an alternative method to the already established branching coefficient (BC) is proposed for summarising the vessel calibres in retinal junctions. This new method combines the mean diameter ratio with an alternative to Murray׳s cube law exponent, derived by the fractal dimension,experimentally, and the branch exponent of cerebral vessels, as has been suggested in previous studies with blood flow modelling. For the above calculations, retinal images from healthy, diabetic and DR subjects were used. In addition, the above method was compared with the BC and was also applied to the evaluation of arteriovenous ratio as a biomarker of progression from diabetes to DR in four consecutive years, i.e. three/two/one years before the onset of DR and the first year of DR. Moreover, the retinal arteries and veins around the optic nerve head were also evaluated. The new approach quantifies the vessels more accurately. The decrease in terms of the mean absolute percentage error was between 0.24% and 0.49%, extending at the same time the quantification beyond healthy subjects.