Abnormalities of retinal microvascular structure and risk of mortality from ischemic heart disease and stroke

Air Pollution and the microvasculature: a cross-sectional assessment of in vivo retinal images in the population-based multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Long- and short-term exposures to air pollution, especially fine particulate matter (PM(2.5)), have been linked to cardiovascular morbidity and mortality. One hypothesized mechanism for these associations involves microvascular effects. Retinal photography provides a novel, in vivo approach to examine the association of air pollution with changes in the human microvasculature.

METHODS AND FINDINGS

Chronic and acute associations between residential air pollution concentrations and retinal vessel diameters, expressed as central retinal arteriolar equivalents (CRAE) and central retinal venular equivalents (CRVE), were examined using digital retinal images taken in Multi-Ethnic Study of Atherosclerosis (MESA) participants between 2002 and 2003. Study participants (46 to 87 years of age) were without clinical cardiovascular disease at the baseline examination (2000-2002). Long-term outdoor concentrations of PM(2.5) were estimated at each participant's home for the 2 years preceding the clinical exam using a spatio-temporal model. Short-term concentrations were assigned using outdoor measurements on the day preceding the clinical exam. Residential proximity to roadways was also used as an indicator of long-term traffic exposures. All associations were examined using linear regression models adjusted for subject-specific age, sex, race/ethnicity, education, income, smoking status, alcohol use, physical activity, body mass index, family history of cardiovascular disease, diabetes status, serum cholesterol, glucose, blood pressure, emphysema, C-reactive protein, medication use, and fellow vessel diameter. Short-term associations were further controlled for weather and seasonality. Among the 4,607 participants with complete data, CRAE were found to be narrower among persons residing in regions with increased long- and short-term levels of PM(2.5). These relationships were observed in a joint exposure model with -0.8 µm (95% confidence interval [CI] -1.1 to -0.5) and -0.4 µm (95% CI -0.8 to 0.1) decreases in CRAE per interquartile increases in long- (3 µg/m(3)) and short-term (9 µg/m(3)) PM(2.5) levels, respectively. These reductions in CRAE are equivalent to 7- and 3-year increases in age in the same cohort. Similarly, living near a major road was also associated with a -0.7 µm decrease (95% CI -1.4 to 0.1) in CRAE. Although the chronic association with CRAE was largely influenced by differences in exposure between cities, this relationship was generally robust to control for city-level covariates and no significant differences were observed between cities. Wider CRVE were associated with living in areas of higher PM(2.5) concentrations, but these findings were less robust and not supported by the presence of consistent acute associations with PM(2.5).

CONCLUSIONS

Residing in regions with higher air pollution concentrations and experiencing daily increases in air pollution were each associated with narrower retinal arteriolar diameters in older individuals. These findings support the hypothesis that important vascular phenomena are associated with small increases in short-term or long-term air pollution exposures, even at current exposure levels, and further corroborate reported associations between air pollution and the development and exacerbation of clinical cardiovascular disease. Please see later in the article for the Editors' Summary.

Lens opacity and refractive influences on the measurement of retinal vascular fractal dimension

PURPOSE

To examine the influence of lens opacity and refraction on the measurement of retinal vascular fractal dimension (Df).

METHODS

  Optic disc photographs (right eyes) of 3654 baseline Blue Mountains Eye Study participants (aged 49-97) were digitized. Retinal vascular Df was quantified using a computer-based program. Summated severity scores for nuclear, cortical and posterior subcapsular (PSC) cataract were assessed from lens photographs. Refraction data were converted to spherical equivalent refraction (SER), as sum spherical plus 0.5 cylinder power. Axial length was measured at 10-year follow-up examinations using an IOL master.

RESULTS

  Mean Df of the retinal vasculature was 1.444±0.023 for 2859 eligible participants. Increasing lens opacity scores were associated with significant reduction in Df (β=-0.0030, p<0.0001). Both cortical and PSC cataract involving central lens area were associated with reduced Df, after controlling for confounding factors (p(trend) ≤0.0105). Increasing myopia severity was associated with reduced Df after adjusting for lens opacity scores and other confounders (p(trend) <0.0001). The slope of Df decrease per SER reduction was 0.0040 in eyes with SER≤-4D, compared to -0.0016 in eyes with SER>-4D. For axial length quintiles, there were no significant differences in mean Df in all groups except a reduction in the fifth quintile (axial length ≥24.15mm) (all p<0.05).

CONCLUSION

  Ocular media opacity independently influenced retinal vascular Df measurement, but we found no evidence supporting any refractive axial magnification effect on this measure. Myopic refraction ≤-4D was associated with a reduction in Df, suggesting rarefaction of retinal vasculature associated with high myopia.

Capillary pressure may predict preclinical changes in the eye

AIMS/HYPOTHESIS

Microvascular dysfunction is associated with end-organ damage. Macular oedema is an important component of diabetic retinopathy. Macular thickness can be accurately quantified by optical coherence tomography (OCT), enabling accurate assessment of the macular prior to clinically apparent abnormalities. We investigated whether macular (fovea) thickness in non-diabetic individuals is related to the microvascular variables controlling fluid filtration across a blood vessel wall, in particular capillary pressure and the microvascular filtration capacity (Kf).

METHODS

We recruited 50 non-diabetic individuals (25 men, 25 women; age range: 26-78 years; BMI range: 20-46 kg/m(2)). Fovea thickness was assessed by OCT. Microvascular assessments included: finger nailfold capillary pressure; Kf; microvascular structural assessments, i.e. skin vasodilatory capacity, minimum vascular resistance (MVR) and microvascular distensibility; and endothelial function.

RESULTS

At 214.6 (19.9) microm (mean [SD]), fovea thickness was within normal range. Capillary pressure, adjusted for BMI, was associated with fovea thickness (standardised beta 0.573, p = 0.006, linear regression). Fovea thickness was not associated with Kf, microvascular structural assessments or endothelial function. Capillary pressure was still associated with fovea thickness when adjusted for microvascular variables (Kf, vasodilatory capacity, MVR, microvascular distensibility or endothelial function), or for risk factors for diabetes (systemic blood pressure, insulin sensitivity, inflammation, glycaemic status and lipids) and age.

CONCLUSIONS/INTERPRETATION

Capillary pressure, a key determinant of movement of fluid across a blood vessel wall, is associated with fovea thickness in non-diabetic individuals. This suggests that with regard to potential preventative or therapeutic targets, attention should be directed at the mechanisms determining retinal microvascular pressure.

Associations between cardiac target organ damage and microvascular dysfunction: the role of blood pressure

BACKGROUND

Microvascular dysfunction may be an early precursor of cardiovascular disease (CVD). Increased left ventricular mass (LVM), concentric left ventricular remodelling and increased left atrial size are the factors that could predict future CVD. We investigated whether microvascular dysfunction was associated with these cardiac measures.

METHODS AND RESULTS

Laser Doppler fluximetry of skin vessels was used to study associations with risk factors and echocardiographic measurements of LVM, relative wall thickness (RWT), and left atrial size in 305 people (aged 40-65 years; 117 with type 2 diabetes). Flow in response to a 3-min arterial occlusion was measured. Postischaemic peak flow responses were categorized into three distinct groups: slow rise to peak (normal), nondominant early peak group (mildly abnormal) and a dominant early peak (abnormal). Those with a dominant early peak had higher blood pressure (P = 0.001), weight (P = 0.001), fasting glucose (P = 0.001) and prevalence of diabetes (P = 0.02). LVM (P = 0.01), RWT (P < 0.001) and left atrial size (P < 0.001) were greater with worsening postischaemic peak flow responses. Differences in LVM between postischaemic response groups were accounted for by blood pressure (BP). However, differences in BP and other CVD risk factors did not account for the greater RWT and left atrial size observed in the more adverse peak response groups [geometric mean of RWT [95% confidence interval (CI)] 0.40 (0.38-0.41) vs. 0.41 (0.40-0.42) vs. 0.43 (0.41-0.45), P = 0.007; left atrial size 36.1 (35.4-36.1) vs. 37.4 (36.8-38.0) vs. 38.7 (37.5-40.0), P = 0.002 for normal vs. mildly abnormal vs. abnormal respectively].

CONCLUSION

An abnormal microcirculatory cutaneous peak flow response following ischaemia is associated with adverse cardiac remodelling, independent of CVD risk factors including blood pressure.

High blood pressure in children: clinical and health policy implications

Hypertension is a global problem, affecting both developed and developing nations. In addition to being a major cause of morbidity and mortality, hypertension places a heavy burden on health care systems, families, and society as a whole. Despite evidence of an increasing prevalence of hypertension among youth, the consequences of early onset are poorly established and often overlooked. Childhood hypertension is often asymptomatic and easily missed, even by health professionals. Target organ damage is detectable in children and adolescents, however, and hypertension continues into adulthood. Additional strategies to improve cardiovascular health among children and adolescents are needed, including methods to achieve healthy lifestyles at home and in school, improved systems for diagnosis, and research on mechanisms and timing of interventions. The burden of hypertension in the young will continue to grow unless it is given the attention it deserves by policy makers, health care providers, schools, parents, and society. This report aims to increase awareness of the problem of hypertension in childhood. Recent reports on prevalence and target organ injury are discussed and health policy initiatives to improve blood pressure control are proposed.

Fractal analysis of retinal vessels suggests that a distinct vasculopathy causes lacunar stroke

OBJECTIVES

Lacunar strokes account for 25% of all ischemic strokes and may represent the cerebral manifestation of a systemic small vessel vasculopathy of unknown etiology. Altered retinal vessel fractal dimensions may act as a surrogate marker for diseased cerebral vessels. We used a cross-sectional study to investigate fractal properties of retinal vessels in lacunar stroke.

METHODS

We recruited patients presenting with lacunar stroke and patients with minor cortical stroke as controls. All patients were examined by a stroke expert and had MRI at presentation. Digital retinal photographs were taken of both eyes. Monofractal and multifractal analyses were performed with custom-written semiautomated software.

RESULTS

We recruited 183 patients. Seventeen were excluded owing to poor photographic quality, leaving 166 patients (86 with lacunar and 80 with cortical stroke). The mean age was 67.3 years (SD 11.5 years). The patients with lacunar stroke were younger but the prevalence of diabetes, hypertension, and white matter hyperintensities did not differ between the groups. The mean Dbox (monofractal dimension) was 1.42 (SD 0.02), the mean D0 (multifractal dimension) 1.67 (SD 0.03). With multivariate analysis, decreased Dbox and D0 (both representing decreased branching complexity) were associated with increasing age and lacunar stroke subtype after correcting for hypertension, diabetes, stroke severity, and white matter hyperintensity scores.

CONCLUSIONS

Lacunar stroke subtype and increasing age are associated with decreased fractal dimensions, suggesting a loss of branching complexity. Further studies should concentrate on longitudinal associations with other manifestations of cerebral small vessel disease.

Alterations in retinal microvascular geometry in young type 1 diabetes

OBJECTIVE

To describe retinal microvascular geometric parameters in young patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Patients with type 1 diabetes (aged 12-20 years) had clinical assessments and retinal photography following standardized protocol at a tertiary-care hospital in Sydney. Retinal microvascular geometry, including arteriolar and venular tortuosity, branching angles, optimality deviation, and length-to-diameter ratio (LDR), were measured from digitized photographs. Associations of these geometric characteristics with diabetes duration, A1C level, systolic blood pressure (SBP), and other risk factors were assessed.

RESULTS

Of 1,159 patients enrolled, 944 (81.4%) had gradable photographs and 170 (14.7%) had retinopathy. Older age was associated with decreased arteriolar (P = 0.024) and venular (P = 0.002) tortuosity, and female subjects had larger arteriolar branching angle than male subjects (P = 0.03). After adjusting for age and sex, longer diabetes duration was associated with larger arteriolar branching angle (P <or= 0.001) and increased arteriolar optimality deviation (P = 0.018), higher A1C was associated with increased arteriolar tortuosity (>8.5 vs. <or=8.5%, P = 0.008), higher SBP was associated with decreased arteriolar LDR (P = 0.002), and higher total cholesterol levels were associated with increased arteriolar LDR (P = 0.044) and decreased venular optimality deviation (P = 0.044). These associations remained after controlling for A1C, retinal vessel caliber, and retinopathy status and were seen in subjects without retinopathy.

CONCLUSIONS

Key diabetes-related factors affect retinal microvascular geometry in young type 1 diabetes, even in those without evidence of retinopathy. These early retinal alterations may be markers of diabetes microvascular complications.

The relationship between retinal microvascular abnormalities and coronary heart disease: a review

Heart disease remains the leading cause of death in the United States despite decades of advancement in its diagnosis and treatment. Because of the limitations of traditional risk stratification for heart disease, evaluation of the retinal vasculature has been proposed as an easily and safely measured adjunct to commonly used screening methods. This article provides a comprehensive review of the literature concerning the relationships between retinal microvascular abnormalities and coronary heart disease. We outline details of the most recent large epidemiologic studies and discuss their potential implications for clinical practice. Finally, we propose a change to the current guidelines regarding the screening of "low-risk" women, a group that is often failed by traditional evaluation algorithms.

Automated analysis of retinal vascular network connectivity

This paper describes an algorithm that forms a retinal vessel graph by analysing the potential connectivity of segmented retinal vessels. Self organizing feature maps (SOFMs) are used to model implicit cost functions for the junction geometry. The algorithm uses these cost functions to resolve the configuration of local sets of segment ends, thus determining the network connectivity. The system includes specialized algorithms to handle overlapping vessels. The algorithm is tested on junctions drawn from the public-domain DRIVE database.

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.

Parallel multiscale feature extraction and region growing: application in retinal blood vessel detection

This paper presents a parallel implementation based on insight segmentation and registration toolkit for a multiscale feature extraction and region growing algorithm, applied to retinal blood vessels segmentation. This implementation is capable of achieving an accuracy (Ac) comparable to its serial counterpart (about 92%), but 8 to 10 times faster. In this paper, the Ac of this parallel implementation is evaluated by comparison with expert manual segmentation (obtained from public databases). On the other hand, its performance is compared with previous published serial implementations. Both these characteristics make this parallel implementation feasible for the analysis of a larger amount of high-resolution retinal images, achieving a faster and high-quality segmentation of retinal blood vessels.

Semi-automated evaluation tool for retinal vasculopathy

The ocular fundus is the only area of human body where vascular system is visible using relatively simple instrumentation. Furthermore, there is medical suggestive evidence of a direct relationship between certain measures of vascular characteristics in the ocular fundus (arteriolar and venular calibers and focal arteriolar narrowing) and cardiovascular diseases. In order to establish such relationship on sound statistical basis a method must be provided to measure the needed values in an easy, yet precise and repeatable way. This paper presents a system to assist physicians in signaling and storing the data associated to signs of vascular deterioration and vascular calibers in non-mydriatic ocular fundus images. The system is built around a graphical user interface that, even not fully automatic, guides the practitioner to mark certain anatomic visible features in an easy and precise way. The data are exported in common database formats for further processing and a statistical summary is also presented.

Comparison of the retinal microvasculature in European and African-Caribbean people with diabetes

Diabetes aggravates the impact of elevated BP (blood pressure) on the microcirculation, and people of African ancestry with diabetes are more susceptible to microvascular damage than Europeans. In the present study, we investigated possible differences in the retinal microcirculation in people of European and African-Caribbean ethnicity with diabetes that might account for this. A total of 51 subjects with Type 2 diabetes (age 40–65 years; 25 male; 29 African-Caribbean) were studied. Clinic and 24 h ambulatory BP, and fasting glucose, insulin and lipids were measured. Digital retinal images were analysed using custom-written semi-automatic software to determine: LDR (length/diameter ratio) and AVR (arteriolar/venular diameter ratio), branching angles, vessel tortuosity and NT (number of terminal vessel branches). Arterioles were narrower in European people with diabetes than in African-Caribbean people with diabetes [mean (S.D.) arteriolar diameter, 76 (7) compared with 82 (11) μm respectively (P=0.03); arteriolar LDR, 28.1 (8.5) compared with 23.7 (7.0) respectively (P=0.046); and AVR, 0.66 (0.21) compared with 0.90 (0.36) respectively (P=0.028)]. Ethnic differences in arteriolar LDR, arteriolar diameter and AVR were not explained by differences in BP, but were attenuated by adjustment for the duration of diabetes. There was no significant relationship between BP and arteriolar narrowing in the group as a whole, although the relationship between arteriolar LDR and systolic BP was stronger in Europeans than African-Caribbeans [β=0.08 (0.07) compared with β=0.03 (0.06); P=0.03]. In conclusion, in the presence of diabetes, a relationship between BP and retinal arteriolar diameter was not evident and implies impaired small artery remodelling in the presence of diabetes. African-Caribbean people with diabetes have wider retinal arterioles and this could contribute to enhanced microvascular damage in this ethnic group.

Retinal vascular changes and diabetic retinopathy

Recent studies support the concept that the retinal vasculature may provide a summary measure of lifetime exposure to the effects of hyperglycemia. Advances in retinal photographic techniques and in image analysis have allowed objective and precise in vivo measurement of retinal vascular changes. In particular, quantitative assessment of retinopathy signs and measurement of retinal vascular caliber have greatly increased our knowledge of early microcirculatory alterations in prediabetes, diabetes, and diabetic micro- and macrovascular complications. Data from recent population-based studies suggest that retinal arteriolar and venular caliber changes reflect different pathophysiologic processes. Retinal arteriolar narrowing, for example, is associated with risk of diabetes and coronary artery disease, whereas retinal venular widening is associated with development and progression of diabetic retinopathy and risk of stroke. Studying these changes offers the potential to improve our understanding of the early pathophysiologic pathways of diabetes development and its complications. Future research will assess the ability of retinal vascular imaging to provide clinically useful prognostic information for patients with diabetes.

Serum amyloid A, C-reactive protein, and retinal microvascular changes in hypertensive diabetic and nondiabetic individuals: an Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) substudy

OBJECTIVE

To study the association of the inflammatory markers serum amyloid A (SAA) and C-reactive protein (CRP) with retinal microvascular parameters in hypertensive individuals with and without type 2 diabetes.

RESEARCH DESIGN AND METHODS

This cross-sectional analysis was a substudy in 711 patients (159 with and 552 without diabetes) of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) based on digital 30-degree images of superior and inferior temporal retinal fields.

RESULTS

SAA was associated with arteriolar length-to-diameter ratio positively in nondiabetic patients (P(trend)= 0.028) but negatively in diabetic patients (P(trend)= 0.005). The difference was unlikely to be a chance finding (P = 0.007 for interaction). Similar results were found for the association of SAA with arteriolar tortuosity (P = 0.05 for interaction). Associations were less pronounced for CRP and retinal parameters.

CONCLUSIONS

Inflammatory processes are differentially involved in retinal microvascular disease in diabetic compared with nondiabetic hypertensive individuals.

Determinants of retinal microvascular architecture in normal subjects

BACKGROUND

Recent studies have shown that changes in the retinal microvasculature predict cardiovascular disease (CVD); however, little is known regarding influences on the retinal microvasculature in healthy people without overt cardiovascular or metabolic disease.

METHODS

We used a semiautomated computerized technique to analyze digitized retinal photographs from a total of 167 healthy people (age range, 45-75 years; 83 female), without clinical CVD, diabetes, or hypertension, randomly sampled from the population-based Beaver Dam Eye Study. We assessed arteriolar and venular narrowing, arteriolar optimality deviation, and other quantitative aspects of the retinal microvasculature.

RESULTS

Arterioles were significantly narrower and longer, had wider branching angles, and were more tortuous than venules. Increased arteriolar length to diameter ratio (an index of ratio arteriolar narrowing) was positively and independently associated with older age and elevated systolic blood pressure. Arteriolar optimality deviation (an index of microvascular endothelial dysfunction) increased with greater body mass index. Current smoking and increased white blood cell (WBC) count was associated with wider venules. After controlling for smoking, WBC was no longer a significant predictor of venular diameter.

CONCLUSIONS

CVD risk factors are associated with retinal microvascular changes in healthy individuals without evidence of CVD, diabetes, or hypertension. CVD risk factors have different influences on the arteriolar and venular bed.

Capillary rarefaction in treated and untreated hypertensive subjects

This study aimed to determine if capillary rarefaction is detectable and associated with endothelial dysfunction in persons with mild systolic blood pressure (SBP) elevation. Capillary density and endothelial function were quantified for 150 nondiabetic participants, grouped by blood pressure (BP) as normotensive, untreated high BP, and treated high BP. Structural capillary rarefaction measures were not different between the three groups. Functional capillary rarefaction measures were significantly lower in both high BP groups compared to normotensives, and correlated inversely with endothelial function. The study findings indicate that the hypertensive vascular pathologic process is already underway at modest levels of blood pressure elevation.

Quantitative assessment of early diabetic retinopathy using fractal analysis

OBJECTIVE

Fractal analysis can quantify the geometric complexity of the retinal vascular branching pattern and may therefore offer a new method to quantify early diabetic microvascular damage. In this study, we examined the relationship between retinal fractal dimension and retinopathy in young individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional study of 729 patients with type 1 diabetes (aged 12-20 years) who had seven-field stereoscopic retinal photographs taken of both eyes. From these photographs, retinopathy was graded according to the modified Airlie House classification, and fractal dimension was quantified using a computer-based program following a standardized protocol.

RESULTS

In this study, 137 patients (18.8%) had diabetic retinopathy signs; of these, 105 had mild retinopathy. Median (interquartile range) retinal fractal dimension was 1.46214 (1.45023-1.47217). After adjustment for age, sex, diabetes duration, A1C, blood pressure, and total cholesterol, increasing retinal vascular fractal dimension was significantly associated with increasing odds of retinopathy (odds ratio 3.92 [95% CI 2.02-7.61] for fourth versus first quartile of fractal dimension). In multivariate analysis, each 0.01 increase in retinal vascular fractal dimension was associated with a nearly 40% increased odds of retinopathy (1.37 [1.21-1.56]). This association remained after additional adjustment for retinal vascular caliber.

CONCLUSIONS

Greater retinal fractal dimension, representing increased geometric complexity of the retinal vasculature, is independently associated with early diabetic retinopathy signs in type 1 diabetes. Fractal analysis of fundus photographs may allow quantitative measurement of early diabetic microvascular damage.

Analysis of retinal arteriolar structure in never-treated patients with essential hypertension

OBJECTIVE

Increased wall-to-lumen ratio of small arteries is a predictor of adverse cardiovascular prognosis. We aimed to analyze retinal arteriolar structure in never-treated patients with essential hypertension and to test whether elevated blood pressure is associated with an increased wall-to-lumen ratio of retinal arterioles.

METHODS

The study cohort comprised 21 untreated male patients with essential hypertension (mean age 39.1 +/- 5.4 years) and 29 untreated normotensive men (mean age 36.7 +/- 5.9 years). Wall-to-lumen ratio of retinal arterioles was assessed in vivo using scanning laser Doppler flowmetry.

RESULTS

Patients with essential hypertension had a higher wall-to-lumen ratio of retinal arterioles than normotensive individuals (0.36 +/- 0.1 vs. 0.28 +/- 0.1, P = 0.028). Wall cross-sectional area of retinal arterioles did not differ between the study groups. The growth index, indicating the percentage of difference in average wall cross-sectional area of retinal arterioles between both groups, was 18%. Both systolic (r = 0.360, P = 0.010) and diastolic (r = 0.536, P < 0.001) blood pressures were related to wall-to-lumen ratio of retinal arterioles. Multiple regression analysis including a variety of known cardiovascular risk factors revealed that blood pressure is independently associated with an increased wall-to-lumen ratio of retinal arterioles (systolic blood pressure: beta = 0.417, P = 0.012; diastolic blood pressure: beta = 0.548, P = 0.001).

CONCLUSION

The changes in arteriolar structure of retinal vessels in our study cohort revealed a similar pattern to that observed previously by other investigators in subcutaneous small arteries in essential hypertension. Blood pressure emerged as an important and independent determinant of wall-to-lumen ratio of retinal arterioles.

Retinal Vascular Imaging

The microcirculation is relatively inaccessible to direct visualization and investigation. Recent methods have been developed which use advanced retinal photographic imaging techniques and computer-assisted image analysis to characterize, measure and quantify subtle variations and abnormalities in the retinal vasculature. These quantitative and qualitative assessments demonstrate a close association of retinal vascular signs to both clinical and subclinical cerebrovascular, cardiovascular and metabolic outcomes. Retinal vascular imaging may thus offer potential as a noninvasive research tool to probe the role and pathophysiology of the microvasculature, and as a cardiovascular risk prediction tool. Key areas where retinal vascular imaging has contributed to increased understanding of microvascular pathology and major areas of current and new research are discussed in this review.

Ethnic differences in retinal microvascular structure

AIMS/HYPOTHESIS

People of African origin have increased risk of stroke and retinal microvascular disease compared with populations of European origin. We compared quantitative measures of retinal microvasculature in British white Europeans and African Caribbeans.

METHODS

Population-based study of 215 (45% male) British African-Caribbean migrants and 323 (48% male) white Europeans aged 40-69 years. Digitised retinal images were analysed using a validated semi-automated system.

RESULTS

Arteriolar optimality deviation, an indicator of endothelial dysfunction, was greater in African Caribbeans (age- and sex-adjusted means [95% CIs]: 0.06 [0.05-0.06] vs 0.04 [0.04-0.05], p = 0.004); this was unexplained by conventional risk factors. Arteriolar diameters were narrower in African Caribbeans (age- and sex-adjusted means [95% CIs]: 18.4 [18.1-18.6] vs 17.9 [17.6-18.2], p = 0.011). These ethnic differences in diameters were attenuated on adjustment for systolic BP (SBP) (adjusted means: 18.2 vs 18.1, p = 0.31). However, there was a significant interaction (p = 0.011) between diabetes and SBP, such that SBP was strongly associated with arteriolar diameter in people without diabetes, but not in those with diabetes (adjusted beta-coefficients for SBP: Europeans: -0.42, p = 0.002 vs 0.17, p = 0.69, African Caribbeans: -0.35, p = 0.023 vs 0.01, p = 0.96). Other measures of retinal vasculature did not differ by ethnicity.

CONCLUSIONS/INTERPRETATION

British African Caribbeans appear to have poorer retinal arteriolar endothelial function than white Europeans. Higher BPs explained the narrower arterioles in African Caribbeans; however, patterns of association between arteriolar narrowing and BP suggest the possibility that cerebral autoregulation and/or remodelling might be adversely affected by diabetes in both ethnic groups.

Diabetes and the tortuosity of vessels of the bulbar conjunctiva

OBJECTIVES

Diabetes is associated with loss of capillaries and macrovessel dilation in the conjunctiva, similar to well-known vessel changes in the retina. However, little is known about the effect of diabetes on the tortuosity of vessels of the conjunctiva. The authors examined the tortuosity of conjunctival vessels in participants with and without diabetes.

DESIGN

Case-control study.

PARTICIPANTS AND CONTROLS

Fifty-three patients with diabetes (17 with type 1 diabetes, 36 with type 2 diabetes) and 60 controls (all aged 20-94 years).

METHODS

Digital red-free images of conjunctivae were analyzed using an automated computer algorithm to identify vessel axes and to quantify vessel tortuosity. Differences in vessel tortuosity were adjusted for age, gender, blood pressure, and smoking status.

MAIN OUTCOME MEASURES

Tortuosity was expressed in units of curve energy (the square of the radian angular change between subsequent locations identified by the algorithm, standardized by vessel length).

RESULTS

A longer duration of diabetes was associated with a reduction in overall vessel tortuosity (-2.8%; 95% confidence interval [CI], -4.3% to -1.3% per decade). This inverse association was driven by changes in larger vessels (40 microm in width or more), whereas increased tortuosity was observed in capillary sized vessels (<25 microm, 4.0%; 95% CI, -0.2% to 8.2% per decade). Compared with controls, those with type 1 diabetes (median duration of disease, 26 years) showed a 17.9% increase (95% CI, 4.7% to -31.0%) in capillary tortuosity. Conversely, those with type 1 diabetes showed a 7% decrease (95% CI, -11.8% to -2.3%) in tortuosity among vessels 40 to 80 microm or less in size and a 26.8% decrease (95% CI, -66.2% to 12.7%) in the fewer number of vessels more than 80 microm in size compared with controls. Similar, but smaller differences were seen in those with type 2 diabetes with shorter duration of diabetes (median, 7 years).

CONCLUSIONS

Macrovessel dilation associated with diabetes may result in vessel engorgement and straightening, especially among those with longer durations of disease. Increased tortuosity associated with diabetes among conjunctival capillaries mirrors established vessel changes observed in the retina. Conjunctival angiopathy associated with diabetes may contribute to susceptibility to anterior eye disease among patients with diabetes.

Usefulness of optic fundus examination with retinography in initial evaluation of hypertensive patients

BACKGROUND

Although international guidelines for management of hypertension recommend optic fundus examination in the initial evaluation of hypertensive patients, there have been no studies to evaluate the usefulness of retinography in this application.

METHODS

Two hundred and fifty consecutive new patients with hypertension but without known cardiovascular disease were studied. The average age was 57.2 years (s.d. 12.9) and 56% were men. The study was conducted in 14 primary care centers. Measurements included target organ damage (TOD) evaluation (electrocardiography, retinography, microalbuminuria, and serum creatinine) and blood pressure (BP) measurements. Outcome measurements were made to risk stratification according to 2003 World Health Organization and International Society of Hypertension (WHO-ISH) and 2007 European Society of Hypertension and European Society of Cardiology (ESH-ESC) guidelines, analyzed first without incorporating the retinography results and then reclassified using the retinography data.

RESULTS

Advanced retinopathy was detected in 10.8%. The risk stratification arrived at as per the WHO-ISH guidelines, and without the retinography data was: 11.4% low risk, 62.4% moderate risk, and 26.2% high risk. When retinography results were taken into account, 8% from the moderate-risk group were reclassified to the high-risk group (11.4, 54.4, and 34.2%, respectively; P < 0.001). Using ESH-ESC guidelines, the risk stratification without the retinography data was 0.9% reference, 11.3% low, 58.8% moderate, 21.7% high, and 7.3% very high risk. With retinography, 10% were reclassified from a lower to a higher risk group (0.9, 10.4, 51.1, 20.4, and 17.2%, respectively; P < 0.001).

CONCLUSIONS

As an alternative to optic fundus examination, retinography enables a more accurate cardiovascular risk stratification in the first evaluation after diagnosis of hypertension. When retinography is included in the assessment of cardiovascular risk, approximately 10% of patients are reclassified to a higher risk group.

Improvement of a retinal blood vessel segmentation method using the Insight Segmentation and Registration Toolkit (ITK)

We describe an improved implementation of a segmentation method for retinal blood vessels based on a multi-scale approach and region growing employing modules from the Insight Segmentation and Registration Toolkit (ITK). We present the results of segmentation of retinal blood vessels using this improved method and compare these with results obtained using the original implementation in Matlab, as well as with expert manual segmentations obtained from a public database. We show that the ITK implementation achieves high quality segmentations with markedly improved computational efficiency. The ITK version has greater segmentation accuracy, from 0.94 to 0.96, than the Matlab version due to a decrease in FPR values and it is between 8 and 12 times faster than the original version. Furthermore, the ITK implementation is able to segment high-resolution images in an acceptable timescale.

A new possible strategy of prevention and preventive treatment of age-related macular degeneration

Az időskori maculadegeneratio (AMD) létrejöttében és későbbi alakulásában az endothel-diszfunkciónak (ED) kulcsszerepe van. Az endothelfunkció-zavarra, illetve annak következményes kóros működésbeli, strukturális és anyagcsere-elváltozásaira különböző gyógyszerek (ACE-inhibitorok, AR-blokkolók, statinok, acetilszalicilsav, trimetazidin) kedvező hatással vannak. Az ED kedvező befolyásolásának, sikeres kezelésének jótékony hatása, az idült vascularis, cardiovascularis betegségekben mára már evidencia: az ACE-gátlók, az AR-blokkolók és a statinok helyreállítják az oxidatív stressz (OS) indukálta ED-ban a felborult egyensúlyt a vasoconstrictorok és vasodilatatorok, a növekedési faktorok és azok gátlói, a proinflammatorok és antiinflammatorok, valamint a prothromboticus és fibrinolyticus tényezők között, gátolják az OS kifejlődését, illetve káros hatásainak kialakulását; a thrombocyta-antiaggregatiós pleiotrop aspirin az endothel nyugalmi állapotának helyreállításában működik hatásosan közre, a trimetazidin pedig segít normalizálni, helyreállítani az elégtelenül funkcionáló szervszövet kóros anyagcserestátuszát. Mivel a humán érrendszer egységes, konszubsztanciális, ezért az ED-ban kedvezően ható gyógyszerek a szem, illetve a retina ereiben is előnyösen hatnak. A fentiek alapján logikus a feltevés, hogy elsődleges és másodlagos prevenciós tevékenység részeként adjunk ilyen gyógyszereket 1) azoknak, akiknek ugyan nincsen maculopathiájuk, de fennállnak az ED-t indukáló AMD-rizikótényezők, és 50 évesek elmúltak; 2) azoknak a betegeknek – a másik szem maculadegeneratiós károsodásának kialakulását megelőzendő –, akiken egyoldali maculopathiát állapítottak meg; 3) végül azoknak – a rosszabbodás kivédése és az esetleges javulás reményében –, akiknél mindkét szemen maculadegeneratiót diagnosztizáltak. – Természetesen emellett törekedjünk az OS-t és konszekutív ED-t indukáló maculadegeneratiós rizikótényezők teljes kiiktatására. – Dolgozatomban a fenti, indirekt bizonyítékokon is alapuló következtetéseket tárgyalom meg.

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

BACKGROUND

The impact of early life factors on the microvasculature is relatively unknown.

OBJECTIVES

We hypothesized that small birth size may be associated with structural variations in the retinal vasculature in children.

METHODS

The Avon Longitudinal Study of Parents and Children followed a cohort of children born in 1991-1992 from birth. The current study included the first 263 children who were systematically screened in the year-12 follow-up. Complete data were available for 166 children with a gestation of > or = 37 weeks. Retinal circulatory measures were evaluated, including retinal microvascular tortuosity and bifurcation optimality deviance, an indicator of abnormal endothelial function.

RESULTS

Optimality deviance and retinal tortuosity were higher among those with lower birth weight. Linear regression modeling was used to assess the association of retinal microvascular measures with birth weight. The standardized beta coefficient between optimality deviance and birth weight was -.182 adjusted for gender and age in weeks; additional adjustment for systolic blood pressure and heart rate had little impact on the beta coefficient. A similar association was observed for retinal tortuosity.

CONCLUSION

The findings of this study suggest that early life factors may have an important impact on retinal vascular structure, possibly through an adverse effect on endothelial function.

Increased Wall:Lumen Ratio of Retinal Arterioles in Male Patients With a History of a Cerebrovascular Event

Arterial hypertension is a major risk factor for stroke, and retinal vessels can be regarded as a mirror of the cerebral vasculature. Whether vascular remodeling of retinal arterioles with ageing and hypertension plays a role in cerebrovascular risk stratification has not yet been adequately addressed. In study 1, retinal arteriolar structure was assessed in 182 normotensive volunteers and 117 patients with essential hypertension. In study 2, we compared retinal arteriolar structure among 74 normotensive volunteers, 47 patients with treated essential hypertension, and 18 subjects with a history of a cerebrovascular event. Retinal arteriolar structure was assessed using scanning laser Doppler flowmetry and automatic full-field perfusion imaging analysis. In study 1, wall:lumen ratio of retinal arterioles revealed a significant correlation with age (r=0.198; P=0.001). In study 2, wall:lumen ratio was highest in patients with a history of a cerebrovascular event compared with treated hypertensive and normotensive subjects (0.46+/-0.08, 0.36+/-0.14, and 0.35+/-0.12; P=0.007). When the treated group with hypertension was divided into 2 subgroups according to the quality of blood pressure control, patients with poor blood pressure control showed higher wall:lumen ratio than subjects with good blood pressure control (0.40+/-0.13 versus 0.31+/-0.13; P=0.025). Thus, assessment of wall:lumen ratio of retinal arterioles emerged as an attractive tool to identify treated patients with hypertension with increased cerebrovascular risk.

Retinal vessel caliber and microvascular and macrovascular disease in type 2 diabetes: XXI: the Wisconsin Epidemiologic Study of Diabetic Retinopathy

OBJECTIVE

To describe the relationship of retinal arteriolar and venular calibers to the long-term incidence of microvascular and macrovascular complications in people with type 2 diabetes.

DESIGN

Population-based prospective study.

PARTICIPANTS

One thousand three hundred seventy persons diagnosed to have diabetes at > or =30 years of age in south central Wisconsin participated in the baseline examination from 1980 to 1982, 987 in the 4-year follow-up, and 533 in the 10-year follow-up.

METHODS

Computer-assisted grading was used to determine the average caliber of retinal arterioles (central retinal arteriolar equivalent [CRAE]) and retinal venules (central retinal venular equivalent [CRVE]) at all examinations.

MAIN OUTCOME MEASURES

Incidence and progression of diabetic retinopathy; incidence of proliferative diabetic retinopathy and macular edema; incidence of nephropathy, neuropathy, and lower extremity amputation; and ischemic heart disease, stroke, and overall mortality.

RESULTS

While adjusting for other factors, smaller CRAE was associated with the 14-year cumulative incidence of lower extremity amputation (odds ratio [OR], first vs. second to fourth quartiles, 2.20; 95% confidence interval [CI], 1.14-4.24; P = 0.02), 22-year all-cause mortality (hazard ratio [HR], 1.18; 95% CI, 1.02-1.38; P = 0.03), and 22-year stroke mortality (HR, 1.47; 95% CI, 1.04-2.07; P = 0.03) but not with the other end points. Larger CRVE was associated with the 14-year incidence of diabetic nephropathy (OR, fourth vs. first to third quartiles, 2.08; 95% CI, 1.47-2.94; P<0.001) and 22-year stroke mortality (HR, 1.71; 95% CI, 1.20-2.44; P = 0.003) but with none of the other end points.

CONCLUSIONS

Retinal vessel caliber is independently associated with risk of incident nephropathy, lower extremity amputation, and stroke mortality in persons with type 2 diabetes. Measurement of retinal vessel caliber from photographs may provide additional information for the prediction of these events.

The clinical assessment of retinal microvascular structure and therapeutic implications

Examination of the retinal microvasculature is widely used to assess diabetic eye disease and as an indicator of target organ damage in hypertension. The diagnostic value of grading of hypertensive retinopathy is dubious; however, many recent studies have demonstrated that hypertensive retinopathy is associated with a range of risk factors for cardiovascular disease and may predict cardiovascular events independently of blood pressure. Developments in digital imaging and computer-assisted analysis have facilitated the quantitative assessment of microvascular changes in cardiovascular disease. These approaches may be useful for assessing cardiovascular risk and targeting therapeutic intervention.

Blood pressure and retinal arteriolar narrowing in children

Retinal arteriolar narrowing is a known response of hypertension and independently predicts cardiovascular mortality in adults. Whether elevated blood pressure leads to retinal arteriolar narrowing in young children is unknown. We examined the relationship of retinal vascular caliber and blood pressure levels in 2 population-based cohorts among children aged 6 to 8 years in Sydney, Australia (1572 children) and Singapore (380 children). Participants had digital retinal photographs and measurement of retinal arteriolar (or small artery) and venular (or small vein) caliber. Children with higher quartiles of blood pressure had significantly narrower retinal arterioles than those with lower blood pressure (retinal arteriolar caliber 162.8, 161.0, 157.8, and 157.1 microm (P for trend<0.001), comparing increasing quartiles of systolic blood pressure in Sydney, and 164.9.5, 164.0, 159.1, and 159.4 microm (P for trend=0.0024 in Singapore). After controlling for age, sex, race, body mass index, refraction, and birth parameters, each 10-mm Hg increase in systolic blood pressure was associated with narrowing of the retinal arterioles by 2.08 microm (95% confidence interval: 1.38 to 2.79; P<0.0001) in Sydney children and 1.43 microm (95% confidence interval: 0.27 to 2.59; P=0.016) in Singapore children. These associations were consistent across age, sex, body mass index, and birth parameters. Retinal venules were not affected by blood pressure. We conclude that higher childhood blood pressure is associated with retinal arteriolar narrowing. Our data provide evidence that the effects of elevated blood pressure may manifest early in life.

[Patient education in chronic polyarthritis. 3. Intermediate results of a prospective, controlled study of the effectiveness and side effects of patient seminars for polyarthritis patients]

Efficacy and possible negative side effects of a patient education program for rheumatoid arthritis were evaluated in a controlled, prospective study over 3 months. 34 outpatients were educated over a total of 8 h in three groups within a patient-centred design. Before the program the knowledge of the disease depended only on the formal grade of education but not on disease-related variables such as disease duration or disability. Probably due to its individualizing method, the program improved the knowledge of all patients to the same extent, regardless of their intellectual and social prerequisites. The increased cognitive knowledge did not result in negative side effects like increased pain or depression. The pain score remained unchanged. Depression decreased after the education. The group sessions made us suppose that the participants may have represented a selected group of active, psychologically stable patients, who cope well with rheumatoid arthritis. In contrast, we felt that non-participation was the response of the inactive, fatalistic patients with rheumatoid arthritis, who live in social isolation and especially need our care. Therefore, future efforts must particularly focus on the problem of motivation and on an increase in the rate of participation.