Bronwen Taylor

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 &mgr;m (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 &mgr;m (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 &mgr;m (95% confidence interval: 1.38 to 2.79; P<0.0001) in Sydney children and 1.43 &mgr;m (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.

The Retinal Vasculature as a Fractal: Methodology, Reliability, and Relationship to Blood Pressure

OBJECTIVE Fractals represent a type of derived geometric pattern that permits the characterization of the branching pattern of retinal vessels. We examined a new semiautomated method to measure retinal vessel fractals. DESIGN Methodology study. PARTICIPANTS Three hundred randomly selected participants from the population-based Blue Mountains Eye Study. METHODS We developed a semiautomated computer program to measure the fractal dimension (D(f)) of the retinal vessels from digitized images of disk-centered retinal photographs. Two trained graders masked to participant characteristics measured D(f) of right eye images of participants. Reliability was determined by repeat grading of the images from 60 participants, and association with systolic and diastolic blood pressure was examined in all 300 participants. MAIN OUTCOME MEASURE D(f) of the retinal vessels. RESULTS Mean D(f) was 1.437 with a standard deviation of 0.025. Intragrader and intergrader reliability estimates were high with intraclass correlation ranging from 0.93 to 0.95. D(f) was inversely correlated with age (r = -0.42, P = 0.001) and systolic blood pressure (r = -0.29, P<0.0001). After adjustment for age and sex, mean D(f) was significantly lower in participants with than without hypertension (D(f) difference 0.01, P = 0.02). CONCLUSIONS The D(f) of the retinal vessels can be reliably measured from photographs and shows a strong inverse correlation with blood pressure. These data suggest that the D(f) may be a measure of early microvascular alterations from elevated blood pressure. Further studies to examine the systemic and ocular correlates of the D(f) of the retinal vessels are needed.

Retinal Vessel Diameters and Obesity: A Population-Based Study in Older Persons

Objective: Obesity is linked with large vessel atherosclerosis and diabetes. Its association with microvascular changes is less clear. We investigated the associations among retinal vessel diameters, vessel wall signs, and BMI in an older population.

Prevalence and Risk Factors for Age-Related Macular Degeneration in an Adult Japanese Population : The Funagata Study

OBJECTIVE To describe the prevalence and risk factors for age-related macular degeneration (AMD) in a Japanese population and to compare these with data from a white population. DESIGN Population-based cross-sectional epidemiologic study. PARTICIPANTS A population-based sample of Japanese persons 35 years or older from Funagata, Japan. METHODS The Funagata study is a population-based study of 1758 (43% of eligible) Japanese persons 35 years or older from Funagata, Japan. In 2000 to 2002, 1625 (92.4%) participants had a nonmydriatic fundus photograph of one eye with sufficient quality for grading of AMD lesions, using the Wisconsin protocol. Age-standardized prevalence rates compared with the Blue Mountains Eye Study (BMES) population, odds ratios (ORs), and 95% confidence intervals (CIs) were calculated. Risk factors were assessed by logistic regression. MAIN OUTCOME MEASURES Early and late AMD. RESULTS Of 1625 participants, early AMD and late AMD were present in 3.5% and 0.5%, respectively. Age-standardized early AMD prevalence in right eyes was 4.1%, similar to the corresponding prevalence of 4.4% in the BMES. For men, age-standardized prevalences of late AMD in right eyes were 1.1% and 1.2% in the BMES; for women, the corresponding prevalences were 0.3% and 2.1%, respectively. Increasing age (per 10 years; gender-adjusted OR, 2.27; 95% CI, 1.10-4.67) and current cigarette smoking (age- and gender-adjusted OR, 5.03; 95% CI, 1.00-25.47) were associated with late AMD. CONCLUSIONS In this Japanese population, prevalence of early AMD was similar to that for whites in the BMES. Although the late AMD prevalence was lower in Japanese women, in Japanese men it was similar to that in whites. This could have resulted from the substantially high proportion of Japanese men who are smokers. Cigarette smoking and increasing age were the 2 principal factors found associated with late AMD.

Measuring the quality of public open space using Google Earth.

BACKGROUND Proximity to public open space, such as parks and other green spaces, has considerable health benefits, and people have been shown to be more likely to use such space for physical activity if it is of high quality. This paper describes a new remote-assessment approach that makes use of Google Earth Pro (the free version of this program is Google Earth) to provide rapid and inexpensive measurement of the quality of public open space. PURPOSE The aim of the study was to assess the correlation between assessments of the quality of public open space using (1) the remote method (making use of Google Earth Pro) and (2) direct observation with a well-established measure of quality, the Public Open Space Tool (POST). METHODS Fifty parks selected from the southwest part of Sydney, Australia, were assessed in 2009 with the remote method (using Google Earth Pro), and scores were compared with those obtained from direct observation of the same parks using POST. The time taken to conduct the assessments using each method was also recorded. Raters for each method were blind to scores obtained from using the other method. Analyses were conducted in 2009. RESULTS The Spearman correlation coefficient between the quality scores obtained for the 50 parks using the remote method and direct observation was 0.9 (p<0.0001). The remote method took 4 hours, whereas direct observation took 42 hours, showing the remote method to be much faster and more resource efficient for the measurement of the quality of physical activity-related environments. CONCLUSIONS The remote-assessment method provides, for the first time, the capacity to assess the quality of large numbers of parks and other green spaces without the need for in-person visits, dramatically reducing the time required for environmental audits of public open space.

Body mass index and its effects on retinal vessel diameter in 6-year-old children

Purpose:To examine the relationship between body mass index (BMI) and other anthropometric measures with retinal vessel diameter in children.Methods:A random cluster sample of 34 schools was selected in the Sydney metropolitan area during 2003–04, and 1740 children aged 6 years participated in The Sydney Childhood Eye Study. Retinal images were taken and vessel diameter was measured using a computer-imaging program. Anthropometric measures, including weight, height, waist circumference, BMI and body surface area (BSA), were obtained and defined using standardized protocols. Data on confounders, including ocular parameters, ethnicity, birth parameters and blood pressure, were similarly collected.Results:Mean BMI was 16.2 kg/m2 (±2.1 s.d.) in 1608 (92.4%) children with complete data. After controlling for age, sex, ethnicity, axial length of the eyeball, birth weight and mean arterial blood pressure, children with BMI above the cardiovascular risk threshold (defined as BMI>16.1 kg/m2 in boys and BMI>15.9 kg/m2 in girls) had mean retinal venular diameter 2.1 μm larger than those with BMI below this threshold (P=0.026). Increasing weight and BSA were also positively associated with wider retinal venules. Children in the highest quartile of BMI had mean retinal arteriolar diameter 2.2 μm smaller than those in the lowest quartile. Increasing waist circumference and shorter height were also associated with narrower retinal arterioles.Conclusions:In this sample of 6-year-old children, greater BMI, weight and BSA were associated with wider retinal venules, while greater BMI and larger waist circumference were associated with narrower retinal arterioles. These findings suggest a possible effect of increased body mass and adiposity on early microvascular structural alterations in childhood, long before the development of cardiovascular disease.

Ethnic variability in retinal vessel caliber: a potential source of measurement error from ocular pigmentation?--the Sydney Childhood Eye Study.

PURPOSE To describe the effects of ethnicity and iris color on measurement of retinal vascular caliber. METHODS The Sydney Childhood Eye Study (SCES) examined 1740 6-year-old children from 34 randomly selected Sydney schools during 2003 and 2004. Retinal arteriolar and venular calibers (central retinal arteriolar [CRAE] and central retinal venular [CRVE] equivalents) were measured from retinal photographs by a standardized computer-assisted METHOD Associations of retinal vascular caliber with ethnicity and iris color were analyzed. RESULTS Of the total participants, 1612 (92.6%) had gradable retinal photographs. CRAE and CRVE were normally distributed, with means (SD) of 163.2 (14.0) and 227.3 (18.3) microm, respectively. Both arteriolar and venular calibers were substantially wider in the East Asian than in the Caucasian children (CRAE, 171.5 mum vs. 160.5 mum; and CRVE, 240.5 microm vs. 222.4 microm; P < 0.0001 for both comparisons). Among the Caucasian children, darker iris color was associated with wider arteriolar and venular caliber: CRAE increased from 157.5 microm in blue eyes to 169.2 microm in dark brown eyes (P for trend < 0.0001), and CRVE increased from 218.4 microm in blue eyes to 230.0 microm in dark brown eyes (P for trend < 0.0001). Among the children with dark brown eyes, there was no significant difference in CRAE between the Caucasian and the East Asian children, although mean CRVE was still approximately 10 mum wider in the East Asian than in the Caucasian children. CONCLUSIONS Retinal vessel caliber was wider in the children of East Asian ethnicity. This difference was explained principally by darker iris color. Retinal pigmentation, as approximated by iris color, could be an important source of error in the measurement of retinal vessel caliber. If confirmed, this may affect comparisons of retinal vessel caliber between subjects with different ethnic backgrounds.

Relationships of retinal vessel diameters with optic disc, macular and retinal nerve fiber layer parameters in 6-year-old children

PURPOSE To describe the normal anatomic relationships of retinal vessel diameters with optic disc, macula, and retinal nerve fiber layer parameters in young children. METHODS This was a population-based, cross-sectional study of 1204 healthy children 6 years of age who were participating in the Sydney Childhood Eye Study. Retinal arteriolar and venular diameters were measured from fundus photographs using standardized computer-based methods. Optical coherence tomography was performed to obtain measurements of the optic disc, macula, and retinal nerve fiber layer parameters. RESULTS In multivariate analyses, each standard deviation (SD) decrease in optic disc area was associated with a 0.14-pixel decrease (P = 0.05) in arteriolar diameter and a 0.31-pixel decrease (P < 0.01) in venular diameter. Each SD decrease in optic cup area was associated with a 0.15-pixel decrease (P = 0.05) in arteriolar diameter and a 0.43-pixel decrease (P < 0.01) in venular diameter. Each SD decrease in macular (inner/outer) thickness or volume was associated with a 0.25- to 0.39-pixel decrease (P < 0.01) in arteriolar diameter and a 0.36- to 0.71-pixel decrease (P < 0.01) in venular diameter, and each SD decrease in retinal nerve fiber layer thickness was associated with a 0.62-pixel decrease (P < 0.01) in arteriolar diameter and a 0.99-pixel decrease (P < 0.01) in venular diameter. CONCLUSIONS Childrens eyes with a smaller optic disc, thinner macula, and thinner retinal nerve fiber layer have narrower retinal vessels. These anatomic relationships may provide new insights into the vascular etiology of various ocular diseases.

Coronary catheterisation does not lead to retinal artery emboli in short-term follow-up of cardiac patients.

Background and Purpose— There is emerging evidence that coronary catheterization can cause cerebrovascular embolization. We aimed to assess the proportion of cardiac patients with retinal emboli before coronary catheterization and the proportion with newly developed retinal embolism shortly after coronary catheterization. Methods— Ninety-seven patients attending Westmead Hospital for coronary catheterization between December 2005 and February 2006 were recruited. Medical history, physical examination, and pre- and postcatheterization photography of 5 retinal fields was performed. The proportion of patients with new retinal emboli was assessed by comparing post- and precatheterization retinal photographs. Results— Before catheterization, retinal emboli were observed in 5 patients (5.2%) and were significantly associated with higher body mass index (P=0.007). The presence of angiographic coronary artery disease was not significantly associated with preexisting retinal emboli. In 97 patients, we found no new emboli within the 16-hour (median: range 4 to 45 hours) postcoronary catheterization period. Conclusions— Asymptomatic retinal emboli are relatively common in patients being assessed for coronary artery disease. We found no evidence suggesting coronary catheterization contributes to retinal embolism shortly after the procedure.