Impact of size at birth on the microvasculature: the Avon Longitudinal Study of Parents and Children

Computer-assisted evaluation of retinal vessel tortuosity in moderate-to-late preterm children

PURPOSE

Since very preterm children often have increased retinal tortuosity that may indicate decisive architectural changes in the systemic microvascular network, we used a new semi-automatic software to measure retinal vessel tortuosity on fundus digital images of moderate-to-late preterm (MLP) children.

METHODS

In this observational case-control study, the global and local tortuosity parameters of retinal vessels were evaluated on fundus photographs of 36 MLP children and 36 age- and sex-matched controls. The associations between birth parameters and parameters reflecting retinal vessel tortuosity were evaluated using correlation analysis.

RESULTS

Even after incorporation of anatomical factors, the global and local tortuosity parameters were not significantly different between groups. The MLP group showed a smaller arteriolar caliber (0.53  ±  0.2) than the controls (0.56  ±  0.2; p  =  0.013). Other local tortuosity parameters, such as vessel length, distance to fovea, and distance to optic disc, were not significantly different between arteries and veins. Tortuosity in both groups was higher among vessels closer to the fovea (r  =  -0.077, p < 0.001) and the optic disc (r  =  -0.0544, p  =  0.009). Global tortuosity showed a weakly positive correlation with gestational age and a weakly negative correlation with birth weight in both groups.

CONCLUSION

MLP patients did not display increased vessel tortuosity in comparison with the controls; however, the arteriolar caliber in the MLP group was smaller than that in children born full-term. Larger studies should confirm this finding and explore associations between cardiovascular and metabolic status and retinal vessel geometry in MLP children.

Evaluation of a portable retinal imaging device: towards a comparative quantitative analysis for morphological measurements of retinal blood vessels

This study investigated the possibility of using low-cost, handheld, retinal imaging devices for the automatic extraction of quantifiable measures of retinal blood vessels. Initially, the available handheld devices were compared using a Zeiss model eye incorporating a USAF resolution test chart to assess their optical properties. The only suitable camera of the five evaluated was the Horus DEC 200. This device was then subjected to a detailed evaluation in which images in human eyes taken from the handheld camera were compared in a quantitative analysis with those of the same eye from a Canon CR-DGi retinal desktop camera. We found that the Horus DEC 200 exhibited shortcomings in capturing images of human eyes by comparison with the Canon. More images were rejected as being unevaluable or suffering failures in automatic segmentation than with the Canon, and even after exclusion of affected images, the Horus yielded lower measurements of vessel density than the Canon. A number of issues affecting handheld cameras in general and some features of the Horus in particular have been identified that might contribute to the observed differences in performance. Some potential mitigations are discussed which might yield improvements in performance, thus potentially facilitating use of handheld retinal imaging devices for quantitative retinal microvascular measurements.

Retinal vessel diameters and function in cardiovascular risk and disease

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

Impact of Birth Weight and Length on Primary Hypertension in Children

BACKGROUND

A child's birth parameters not only enable assessment of intrauterine growth but are also helpful in identifying children at risk of developmental defects or diseases occurring in adulthood. Studies show that children born with a body weight that is small for their gestational age (SGA) are at a greater risk of hypertension though the inverse relation between excessive birth weight and the risk of primary hypertension in children is discussed less frequently.

PURPOSE

To assess the impact of both birth weight and length on hypertension occurring in children aged 3-15 years.

METHODS

A total of 1000 children attending randomly selected primary schools and kindergartens were examined. Ultimately, the analyses took into account n = 747 children aged 4-15; 52.6% boys and 47.4% girls. The children's body height and weight were measured; their blood pressure was examined using the oscillometric method. Information on perinatal measurements was retrieved from the children's personal health records.

RESULTS

Compared to the children with small for gestational age (SGA) birth weight, the children with appropriate for gestational age birth weight (AGA) (odds ratio (OR) 1.31; 95% confidence interval (CI) 0.64-2.65) present greater risk for primary hypertension. Infants born with excessive body weight >4000 g irrespective of gestational age, compared to infants born with normal body weight, show increased risk of primary hypertension (OR 1.19; 95% CI 0.68-2.06). Higher risk of hypertension is observed in infants born with greater body length (OR 1.03; 95% CI 0.97-1.08).

CONCLUSIONS

The problem of hypertension may also affect children with birth weight appropriate for gestational age. The prevalence of hypertension in children with AGA birth weight decreases with age. Birth length can be a potential risk factor for hypertension in children and adolescents.

Automatic optic disc detection in colour fundus images by means of multispectral analysis and information content

The optic disc (OD) in retinal fundus images is widely used as a reference in computer-based systems for the measurement of the severity of retinal disease. A number of algorithms have been published in the past 5 years to locate and measure the OD in digital fundus images. Our proposed algorithm, automatically: (i) uses the three channels (RGB) of the digital colour image to locate the region of interest (ROI) where the OD lies, (ii) measures the Shannon information content per channel in the ROI, to decide which channel is most appropriate for searching for the OD centre using the circular Hough transform. A series of evaluations were undertaken to test our hypothesis that using the three channels gives a better performance than a single channel. Three different databases were used for evaluation purposes with a total of 2,371 colour images giving a misdetection error of 3% in the localisation of the centre of the OD. We find that the area determined by our algorithm which assumes that the OD is circular, is similar to that found by other algorithms that detected the shape of the OD. Five metrics were measured for comparison with other recent studies. Combining the two databases where expert delineation of the OD is available (1,240 images), the average results for our multispectral algorithm are: TPR = 0.879, FPR = 0.003, Accuracy = 0.994, Overlap = 80.6% and Dice index = 0.878.

Cardiometabolic Health Among Adult Offspring of Hypertensive Pregnancies: The Cardiovascular Risk in Young Finns Study

Background

Cardiometabolic health among adult offspring of hypertensive disorders of pregnancy (HDP) is relatively unknown. We hypothesized that offspring of HDP would have abnormalities in the retinal microvasculature and cardiac structure by midadulthood.

Methods and Results

The Cardiovascular Risk in Young Finns Study included randomly selected children from 5 Finnish university cities. The mean age of participants was 40 years (range 34–49 years) at the time of retinal photography and cardiac assessment. Offspring born ≥37 weeks of gestation and appropriate for gestational age (n=1006) were included. Offspring of HDP had higher systolic blood pressure (β=4.68, P<0.001), body mass index (β=1.25, P=0.009), and waist circumference (β=0.25, P=0.042), compared with offspring of normotensive pregnancies. However, no differences in fasting glucose, insulin, lipid profile, carotid intima media thickness, or brachial artery flow‐mediated dilatation were shown. Retinal arteriolar diameters were narrower (β=−0.43, P=0.009) and longer (β=32.5, P=0.023) and the arteriolar length‐to‐diameter ratio was higher (β=2.32, P=0.006) among offspring of HDP, after adjustment for age and sex. Left atrial volume indexed to body surface area (β=1.34, P=0.040) was increased. Adjustment for the confounding effects of birth weight, body mass index, smoking and socioeconomic status, and the mediating effect of hypertension had little impact on the associations.

Conclusions

Abnormalities of the retinal microvasculature and cardiac structure are seen in offspring of HDP in midadulthood. These findings may need to be considered in future primary prevention strategies of cardiovascular disease among offspring of HDP.

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

Retinal vascular imaging in early life: insights into processes and risk of cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality globally. In recent years, studies have shown that the origins of CVD may be traced to vascular and metabolic processes in early life. Retinal vascular imaging is a new technology that allows detailed non-invasive in vivo assessment and monitoring of the microvasculature. In this systematic review, we described the application of retinal vascular imaging in children and adolescents, and we examined the use of retinal vascular imaging in understanding CVD risk in early life. We reviewed all publications with quantitative retinal vascular assessment in two databases: PubMed and Scopus. Early life CVD risk factors were classified into four groups: birth risk factors, environmental risk factors, systemic risk factors and conditions linked to future CVD development. Retinal vascular changes were associated with lower birth weight, shorter gestational age, low-fibre and high-sugar diet, lesser physical activity, parental hypertension history, childhood hypertension, childhood overweight/obesity, childhood depression/anxiety and childhood type 1 diabetes mellitus. In summary, there is increasing evidence supporting the view that structural changes in the retinal microvasculature are associated with CVD risk factors in early life. Thus, the retina is a useful site for pre-clinical assessment of microvascular processes that may underlie the future development of CVD in adulthood.

Impact of blood pressure on retinal microvasculature architecture across the lifespan: the Young Finns Study

OBJECTIVE

The present study examined the impact of BP from childhood to mid-adulthood on retinal microvascular architecture.

METHODS

The Cardiovascular Risk in Young Finns Study included children aged 3-18 years, from five Finnish University cities, with participants chosen randomly from the national population registrar from those areas. The age of participants included in the current analyses in childhood (1980) ranged from three to nine years and in mid-adulthood (2011) ranged from 34 to 40 years (complete data n = 657). Measures of retinal microvasculature architecture measured in adulthood included diameters, tortuosity, lengths, and LDR.

RESULTS

Regression analysis showed a strong negative association between childhood systolic BP and adult arteriolar diameter (standardized regression coefficient [β] -0.300; p < 0.001) and with change in systolic BP from childhood to adulthood (β = -0.249; p < 0.001). For arteriolar tortuosity, there was a strong positive association between childhood systolic BP and adult arteriolar tortuosity (β = 0.154; p < 0.001) and no association with change in systolic BP from childhood to adulthood (β = 0.072; p = 0.110).

CONCLUSIONS

High BP in childhood and increased BP from childhood to adulthood impacts on retinal microvascular architecture in mid-adulthood.

Ophthalmic experience over 10 years in an observational nationwide Danish cohort of Fabry patients with access to enzyme replacement

PURPOSE

Enzyme replacement therapy (ERT) was offered from year 2001 to patients with Fabry disease. The ophthalmic experience was analysed, as part of a general 10-year status.

METHODS

A retrospective observational series comprising 39 patients (25 females, 14 males) closely followed by the endocrinologists, and with regular ophthalmic control. Time of inclusion was when the option of ERT was started, at age 11-60 years. Eye data (standard eye examination, including retinal imaging) were incomplete in five, due to death or non-attendance, and five patients had refused treatment.

RESULTS

Vision was normal throughout, except in two young males with total unilateral central retinal artery occlusion, prior to and during enzyme replacement, respectively. Cornea verticillata and conjunctival vessel ectasies were common. Tortuosity of retinal arterioles and venules was recorded in eight and 18 patients, respectively, and phlebopathy in 22, although generally without evidence of loss of vessel wall integrity. Systemic vascular lesions with or without loss of function were recorded for kidney (n = 23), heart (n = 17) and brain (n = 7), and an association was suggested between nephropathy and abnormal morphology of retinal vessels.

CONCLUSIONS

Thirteen of 32 patients on ERT showed a reduction of corneal deposits over the study period. Abnormal ocular vessel morphology was a frequent finding. In contrast to the function loss related to systemic ischaemic lesions, we found no indication of impairment of visual parameters in 37. Compared to other Fabry series, two of 39 patients with serious unilateral occlusive retinal disease may appear a high number. The presence of retinal tortuosity is discussed, possibly reflecting haemodynamic events related to vessel wall deposits, but could also be 'constitutional', as part of the Fabry inheritance.

Association of parental blood pressure with retinal microcirculatory abnormalities indicative of endothelial dysfunction in children

OBJECTIVE

Microcirculatory abnormalities precede the onset of hypertension and may explain its familial nature. We examined the relationship between parental blood pressure (BP) and offspring retinal microvasculature in Pakistani trios [father, mother, and child (aged 9-14 years)].

METHODS

This is a substudy of a population-based trial of BP reduction. Data were available on 358 normotensive, and 410 offspring of at least one hypertensive parent. Retinal vessel characteristics were measured from digital images. Multivariable linear regression models were built to assess the associations between maternal and paternal BP and offspring retinal microvasculature.

RESULTS

Optimality deviation was greatest in offspring of two hypertensive parents, compared with those with one or no hypertensive parent (P=0.030 for trend). Paternal SBP and DBP were each significantly associated with optimality deviation in offspring (P=0.023 and P=0.006, respectively). This relationship persisted after accounting for offspring cardiovascular risk factors [increase in optimality deviation (95% confidence interval, CI) 0.0053 (0.0001-0.0106, P=0.047) and 0.0109 (0.0025-0.0193, P=0.011), for each 10 mmHg increase in paternal SBP and DBP, respectively]. Maternal DBP was inversely associated with offspring arteriovenous ratio -0.0102 (-0.0198 to -0.0007, P=0.035).

CONCLUSION

Microvascular endothelial dysfunction in children is associated with increasing levels of parental hypertension. The association with paternal BP is independent of other cardiovascular risk factors, including the child's BP. Higher maternal DBP is associated with evidence of arteriolar narrowing in offspring. These early microcirculatory changes may help explain familial predisposition to hypertension in people of Pakistani origin at an early age.

VIDEO ABSTRACT

:

Skin capillary density in infants born to normotensive mothers: a comparison between singleton and twin infants

OBJECTIVE

Twin infants tend to have LBW and microvascular alterations but do not appear to have an increase in cardiovascular mortality later in life as singleton infants. We hypothesized that twin infants born to normotensive mothers would not have capillary rarefaction at birth.

METHODS

We studied 26 dizygotic twin infants and compared them with 115 consecutive singleton infants to normotensive mothers. We used orthogonal polarized spectroscopy to measure basal (i.e., functional) and maximal (i.e., structural) skin capillary density according to a well-standardized protocol.

RESULTS

Twin infants have significantly higher BCD (mean difference 4.3 capillaries/mm(2) , 95% CI: 0.4, 8.1, p = 0.03) and have marginally significantly higher MCD (mean difference 3.9 capillaries/mm(2) , 95% CI: -0.6, 8.3, p = 0.086) compared to singleton infants. Birth weight was significantly associated with BCD and MCD (p = 0.003 and 0.006).

CONCLUSIONS

Twin infants with low and NBWs tend to have higher functional and structural capillary densities compared to singleton infants. Further longitudinal studies of skin capillary density and of retinal vascular parameters commencing from birth to various stages in early childhood are essential to identify the dynamics and the exact timing, if any, of the remodeling of microcirculation in these individuals.

Vascular programming in twins: the effects of chorionicity and fetal therapy for twin-to-twin transfusion syndrome

We assessed vascular programming in genetically identical monochorionic twin pairs with twin-to-twin transfusion syndrome (TTTS) treated differently in utero by serial amnioreduction or fetal laser arterial photocoagulation. This case-control study re-assessed four twin groups at median 11 years comprising 20 pairs of monochorionic diamniotic twins: nine treated by amnioreduction (TTTS-amnio) and eleven by laser (TTTS-laser) with seven monochorionic and six dichorionic control pairs. Outcome measures were current blood pressure (BP), brachio-radial arterial stiffness derived from pulse wave velocity (PWV), resting microcirculation (Flux) and response to heating and post-occlusive reactive hyperaemia measured using laser Doppler. Potential confounders [PWV and BP at first study, current height, weight, heart rate and twin type (ex-recipient, ex-donor or heavier/lighter of pair)] were accounted for by Mixed Linear Models statistical methodology. PWV dichorionic > monochorionic (P = 0.024); systolic and diastolic BP dichorionic > TTTS-amnio and TTTS-laser (P = 0.004, P = 0.02 and P = 0.005, P = 0.02, respectively). Within-twin pair pattern of PWV discordance was similar in laser treated and dichorionic controls (heavier-born > lighter), opposite to TTTS-amnio and monochorionic controls. Flux monochorionic > dichorionic (P = 0.044) and heavier > lighter-born (P = 0.024). TTTS-laser and dichorionic diamniotic showed greatest hyperaemic responses (dichorionic > TTTS-amnio or monochorionic controls (P = 0.007, P = 0.025). Hyperaemic responses were slower in heavier-born twins (P = 0.005). In summary, monochorionic twins had lower BP, arterial stiffness and increased resting vasodilatation than dichorionic twins implying shared fetal circulation affects vascular development. Vascular responses in laser-TTTS were similar to dichorionic and opposite to TTTS-amnio suggesting a lasting effect of fetal therapy on vascular health.

Cerebral malaria in children: using the retina to study the brain

Cerebral malaria is a dangerous complication of Plasmodium falciparum infection, which takes a devastating toll on children in sub-Saharan Africa. Although autopsy studies have improved understanding of cerebral malaria pathology in fatal cases, information about in vivo neurovascular pathogenesis is scarce because brain tissue is inaccessible in life. Surrogate markers may provide insight into pathogenesis and thereby facilitate clinical studies with the ultimate aim of improving the treatment and prognosis of cerebral malaria. The retina is an attractive source of potential surrogate markers for paediatric cerebral malaria because, in this condition, the retina seems to sustain microvascular damage similar to that of the brain. In paediatric cerebral malaria a combination of retinal signs correlates, in fatal cases, with the severity of brain pathology, and has diagnostic and prognostic significance. Unlike the brain, the retina is accessible to high-resolution, non-invasive imaging. We aimed to determine the extent to which paediatric malarial retinopathy reflects cerebrovascular damage by reviewing the literature to compare retinal and cerebral manifestations of retinopathy-positive paediatric cerebral malaria. We then compared retina and brain in terms of anatomical and physiological features that could help to account for similarities and differences in vascular pathology. These comparisons address the question of whether it is biologically plausible to draw conclusions about unseen cerebral vascular pathogenesis from the visible retinal vasculature in retinopathy-positive paediatric cerebral malaria. Our work addresses an important cause of death and neurodisability in sub-Saharan Africa. We critically appraise evidence for associations between retina and brain neurovasculature in health and disease, and in the process we develop new hypotheses about why these vascular beds are susceptible to sequestration of parasitized erythrocytes.

Microcirculatory rarefaction in South Asians - a potential mechanism for increased cardiovascular risk and diabetes

People of South Asian descent have an increased risk of cardiovascular disease (CVD) and diabetes, but little is known about the microcirculation in South Asian people despite evidence that this plays an important role in the aetiology of CVD. We compared the retinal microcirculation in a population-based sample of 287 middle-aged adults (144 European 143 South Asian) matched for age and sex. Retinal photographs were taken and analysed using a validated semi-automated program and microvascular measures were compared. Blood pressure, anthropometry and fasting bloods were also measured. South Asians had significantly fewer arteriolar and venular vessels and bifurcations. Arterioles and venules were longer and venules were also more tortuous in South Asians. These differences were not explained by adjustment for traditional risk factors including blood pressure, body mass index, diabetes or measures of insulin resistance. People of South Asian descent have rarefaction of the retinal microcirculation compared to age-sex matched individuals of European descent. Reduced microvascular density could contribute to the elevated risk of CVD and impaired glucose tolerance in South Asian people.

Can the retinal microvasculature offer clues to cardiovascular risk factors in early life?

Adulthood cardiovascular diseases (CVD) burdening in adulthood have been suggested to have possible predisposition early in life. We aimed to systematically review the literatures on retinal microvasculature among paediatric population in relation to a range of environmental and systemic changes. Papers with quantitative retinal vascular assessment and epidemiological design were reviewed.

CONCLUSION

This review supports the theory that major vascular diseases have pathological predisposition early in life by providing morphological evidence on retinal microcirculation in vivo.

Can field-based mosquito feeding assays be used for evaluating transmission-blocking interventions?

A recent meta-analysis of mosquito feeding assays to determine the Plasmodium falciparum transmission potential of naturally infected gametocyte carriers highlighted considerable variation in transmission efficiency between assay methodologies and between laboratories. This begs the question as to whether mosquito feeding assays should be used for the evaluation of transmission-reducing interventions in the field and whether these field-based mosquito assays are currently standardized sufficiently to enable accurate evaluations. Here, we address biological and methodological reasons for the observed variations, discuss whether these preclude the use of field-based mosquito feeding assays in field evaluations of transmission-blocking interventions, and propose how we can maximize the precision of estimates. Altogether, we underscore the significant advantages of field-based mosquito feeding assays in basic malaria research and field trials.

Retinal vessel tortuosity measures and their applications

Structural retinal vascular characteristics, such as vessel calibers, tortuosity and bifurcation angles are increasingly quantified in an objective manner, slowly replacing subjective qualitative disease classification schemes. This paper provides an overview of the current methodologies and calculations used to compute retinal vessel tortuosity. We set out the different parameter calculations and provide an insight into the clinical applications, while critically reviewing its pitfalls and shortcomings.

Relationship between birth weight and retinal microvasculature in newborn infants

OBJECTIVE

The purposes of this study were to determine the normal retinal microvasculature measurements in human infants who are born at term and to determine whether birth weight influences measurements of retinal microvasculature.

STUDY DESIGN

Retinal arteriole and venule measurements were obtained in a cohort of 24 infants who were born at term. Digital images of both the retinas were obtained using a digital retinal camera after pupillary dilation.

RESULT

In all, 24 newborn infants born at term (12 females and 12 males) were analyzed in this study. The measured retinal arteriole diameters were from 66.8 to 147.8 μm (mean, 94.2±19.6 μm), and the venule diameters were from 102.0 to 167.8 μm (mean, 135.2±19.1 μm). Seven babies in the sample had low birth weight (LBW), while 17 babies were born with normal weight. Babies with lower birth weights had larger arteriole (113.1±17.9 μm vs 86.4±14.4 μm; P=0.0009) and venule diameters (151.7±14.9 μm vs 128.4±16.9 μm; P=0.0040).

CONCLUSION

Retinal venules and arterioles in LBW babies are larger compared with those of normal-birth-weight babies. We postulate that the difference observed in our study was due to in utero pathophysiological changes that occurred in the cerebral circulation of growth-restricted fetuses.

Retinal microvascular changes in low-birth-weight babies have a link to future health

BACKGROUND

In utero insults that result in low-birth-weight (LBW) infants are now recognized risk factors for the development of vascular-related diseases in adulthood. Microcirculatory pathologies are believed to form a mechanistic link between fetal insult and the manifestation of illness in adulthood.

OBJECTIVES

The challenge has been to investigate microcirculatory changes in vivo. The objective of this review is to determine whether LBW infants and individuals undergo abnormal microvascular changes and, if so, whether these changes can be objectively identified and measured by investigating retinal vessels.

METHODS

An online publication search was carried out using the following keywords to identify and review relevant articles: retinal microvasculature, retinal vessels, small for gestation age, growth restriction, and intrauterine growth restriction. Articles published from 1980 to 2011 were considered.

CONCLUSIONS

The ability of retinal imaging technology to assess and measure retinal microvasculature makes it a valuable assessment tool. The current tool is, however, unsuitable for non-invasive assessment in infants and young children. Once this hurdle has been overcome, a longitudinal study of LBW individuals from infancy to adulthood, with regular retinal microvascular assessments, would help prove the mechanistic link between LBW and cardiovascular disease in adulthood.

Retinal arteriolar tortuosity is associated with retinopathy and early kidney dysfunction in type 1 diabetes

PURPOSE

To examine the association of retinal vessel tortuosity with diabetic retinopathy and early nephropathy in type 1 diabetes.

DESIGN

Cross-sectional.

METHODS

A total of 1159 participants with type 1 diabetes aged 12 to 20 years, attending diabetes clinics in Children's Hospital at Westmead, Sydney, Australia between 1990 and 2002, were included. Retinal photography and clinical examinations were performed during the baseline visit to assess diabetic retinopathy and albumin excretion rate (AER). Retinal vessel tortuosity was measured from digitized retinal photographs using a semi-automated computer program by a single grader masked to participants' characteristics. Diabetic retinopathy was defined as ETDRS level ≥21 (mild nonproliferative retinopathy) and early kidney dysfunction was defined as AER ≥7.5 μg/min.

RESULTS

Of 944 patients (81.4%), 85 (9.0%) had signs of retinopathy only, 250 (26.5%) had early kidney dysfunction only, and 85 (9.0%) had both retinopathy and early kidney dysfunction. In multivariate analysis, higher arteriolar tortuosity was associated with retinopathy (odds ratio [OR] 2.01, 95% confidence interval [CI] 1.23-3.29, the highest quartile vs the remaining 3 quartiles), early kidney dysfunction (OR 1.56, 95% CI 1.06-2.28, per standard deviation [SD] increase), or coexistence of both complications (OR 1.96, 95% CI 1.21-3.24, the highest quartile vs the remaining 3 quartiles).

CONCLUSIONS

Greater retinal arteriolar tortuosity was independently associated with retinopathy and early stage of nephropathy in type 1 diabetes. These findings may offer the potential of quantitative measurement of retinal vessel tortuosity for diabetic complication risk assessment.

Low Birth Weight Infants Do Not Have Capillary Rarefaction at Birth

Low birth weight predicts adult essential hypertension and is linked to increased cardiovascular mortality in adult life. A reduction in capillary density (ie, rarefaction) is a hallmark of essential hypertension, and evidence suggests that rarefaction precedes the onset of the rise in blood pressure, because it is found in normotensive individuals at high risk of developing hypertension, suggesting that rarefaction is likely to be a primary structural abnormality. We hypothesized that low birth weight infants would have significant capillary rarefaction at birth. We studied 44 low birth weight infants born to normotensive mothers (33 were born preterm, birth weight: 1823±446 g; and 11 were born at term, birth weight: 2339±177 g) and compared them with 71 infants born at term with normal weight (birth weight: 3333±519 g). We used orthogonal polarized spectroscopy to measure basal (ie, functional) and maximal (ie, structural) skin capillary densities. Low birth weight infants, whether born preterm or at term, had significantly higher functional capillary density (mean difference of 10.5 capillaries per millimeter squared; 95% CI: 6.6–14.4 capillaries per millimeter squared; P <0.0001) and higher structural capillary density (mean difference of 11.1 capillaries per millimeter squared; 95% CI: 7.6–14.5 capillaries per millimeter squared; P <0.0001) when compared with normal weight term infants. We conclude that low birth weight infants born to normotensive mothers do not have capillary rarefaction at birth. These results contradict what might have been predicted from the concept of the intrauterine origins of adult disease and suggest that microcirculatory abnormalities observed in individuals of low birth weight occur in postnatal life rather than during their intrauterine existence.

Retinal vascular tortuosity in persons with diabetes and diabetic retinopathy

AIM/HYPOTHESIS

The aim of this hypothesis was to examine the association of retinal vessel tortuosity with diabetes and diabetic retinopathy (DR).

METHODS

A clinic-based study of 327 participants (224 with diabetes and 103 non-diabetic controls) aged ≥ 18 years. DR was graded from fundus photographs according to the modified Airlie House Classification system and categorised into mild non-proliferative DR (NPDR), moderate NPDR and vision-threatening DR (VTDR). Retinal vessel tortuosity was measured from disc-centred retinal photographs. Measurements were taken, using a semi-automated computer program by a single grader, of arterioles and venules within 0.5 to 2 disc diameters away from the optic disc.

RESULTS

There were 114 (44%) participants with DR. In the multivariate analysis, retinal arteriolar and venular tortuosity were increased in participants with diabetes without DR (mean difference 12.4 × 10(-5) and 13.3 × 10(-5), respectively; both p < 0.05) and in those with DR (mean difference 15.4 × 10(-5) and 15.0 × 10(-5), respectively; both p < 0.01) compared with non-diabetic participants. Among participants with diabetes, increased arteriolar tortuosity was significantly associated with mild NPDR (OR 1.53, 95% CI 1.03-2.05, per SD increase in arteriolar tortuosity) and moderate NPDR (OR 1.67, 95% CI 1.10-2.55) but not VTDR (OR 0.91, 95% CI 0.54-1.54). No association with DR was found for venular tortuosity.

CONCLUSIONS/INTERPRETATION

Persons with diabetes had more tortuous retinal vasculature than persons without diabetes. In persons with diabetes, increased arteriolar tortuosity was associated with mild and moderate stages of DR. This suggests that retinal vascular tortuosity might be an early indicator of microvascular damage in diabetes; thus, further investigation is indicated.

Retinal arteriolar tortuosity and cardiovascular risk factors in a multi-ethnic population study of 10-year-old children; the Child Heart and Health Study in England (CHASE)

OBJECTIVE

To examine the association between cardiovascular risk factors and retinal arteriolar tortuosity in a multi-ethnic child population.

METHODS AND RESULTS

Cross sectional study of 986 UK primary school children of South Asian, black African Caribbean, and white European origin aged 10 to 11 years. Anthropometric measurements and retinal imaging were carried out and a fasting blood sample collected. Digital images of retinal arterioles were analyzed using a validated semiautomated measure of tortuosity. Associations between tortuosity and cardiometabolic risk factors were analyzed using multi-level linear regression, adjusted for gender, age, ethnicity, arteriole branch status, month, and school. Levels of arteriolar tortuosity were similar in boys and girls and in different ethnic groups. Retinal arteriolar tortuosity was positively associated with levels of triglyceride, total and LDL cholesterol, and systolic and diastolic blood pressure. One standard deviation increases in these risk factors were associated with 3.7% (95% CI: 1.2%, 6.4%), 3.3% (0.9%, 5.8%), 3.1% (0.6%, 5.6%), 2.0% (-0.3%, 4.2%), and 2.3% (0.1%, 4.6%) increases in tortuosity, respectively. Adiposity, insulin resistance, and blood glucose showed no associations with tortuosity.

CONCLUSIONS

Established cardiovascular risk factors, strongly linked to coronary heart disease in adulthood, may influence retinal arteriolar tortuosity at the end of the first decade of life.

Branching patterns for arterioles and venules of the human cerebral cortex

Branching patterns of microvascular networks influence vascular resistance and allow control of peripheral flow distribution. The aim of this paper was to analyze these branching patterns in human cerebral cortex. Digital three-dimensional images of the microvascular network were obtained from thick sections of India ink-injected human brain by confocal laser microscopy covering a large zone of secondary cortex. A novel segmentation method was used to extract the skeletons of 228 vascular trees (152 arterioles and 76 venules) and measure the diameter at every vertex. The branching patterns (area ratios and angles of bifurcations) of nearly 10,000 bifurcations of cortical vascular trees were analyzed, establishing their statistical properties and structural variations as a function of the vessel nature (arterioles versus venules), the parent vessel topological order or the bifurcation type. We also describe their connectivity and discuss the relevance of the assumed optimal design of vascular branching to account for the complex nature of microvascular architecture. The functional implications of some of these structural variations are considered. The branching patterns established from a large database of a human organ contributes to a better understanding of the bifurcation design and provides an essential reference both for diagnosis and for a future large reconstruction of cerebral microvascular network.

Effect of birth parameters on retinal vascular caliber: the Twins Eye Study in Tasmania

Recent studies reported an association between smaller birth size and narrower retinal vascular caliber, but it remains unclear whether this association is attributed to confounding by shared environment or genetic factors. At a mean age of 9.3 years, 266 twins (49 monozygotic and 84 dizygotic pairs) in the Twins Eye Study in Tasmania underwent an ophthalmic examination including retinal photography. Retinal vascular caliber was measured using a validated protocol. The majority of these twins were also in the Tasmanian Infant Health Study, which prospectively collected data on birth parameters and antenatal maternal factors. We conducted the main analysis using linear mixed models, accounting for birth set clustering. Both the within-pair (-9.73; 95% CI: -14.68 to -4.77 microm per 5-cm decrease in birth length) and between-pair associations (-7.15; 95% CI: -11.54 to -3.01) with retinal arteriolar caliber were significant and of similar magnitude (difference in effect, P=0.61), after adjusting for age, sex, maternal smoking, mean arterial blood pressure, and other confounders. These associations remained within dizygotic and monozygotic pairs. Analyses of head circumference and retinal arteriolar caliber were similar to those of birth length (within-pair regression coefficient: -2.41; 95% CI: -5.09 to 0.28; between-pair regression coefficient: -2.60; 95% CI: -5.00 to -0.19). For birth weight, only a between-pair association was evident (-7.28; 95% CI: -13.07 to -1.48). This study demonstrates a consistent association between smaller birth size and narrower retinal arterioles in twins. The independent effect of shorter birth length on retinal arteriolar caliber supports a role for twin-specific supply line factors affecting fetal growth on vascular structure.