To examine the effect of blood pressure (BP) on retinal vascular fractal dimension (Df), a measure of microvascular network complexity and density in a multiethnic cohort.
A population-based study of 3876 Chinese, Malay and Indian participants in Singapore. Retinal Df was measured using a computer-based program from digital retinal photographs. Associations between retinal Df and mean arterial BP (MABP) in the whole cohort and in each racial group were analysed using linear regression analysis. Logistic regression was used to examine the association between retinal Df and hypertension status.
The mean retinal Df of the study population was 1.45 (standard deviation 0.03). After adjustment for age, sex, race, diabetes, BMI, cholesterol and creatinine levels, persons with smaller Df had higher MABP (mean difference MABP was 6.18 mmHg comparing lowest to highest Df quartiles, P < 0.001). This was similar in Chinese, Malay and Indian persons [mean difference 6.40 (P < 0.001), 4.72 (P = 0.011) and 6.62 (P < 0.001) mmHg, respectively]. Persons with smaller retinal Df were more likely to have uncontrolled treated or untreated hypertension [odds ratio 1.79 (P = 0.003) and 2.60 (P = 0.003), respectively, comparing lowest to highest Df quartiles] than those with no hypertension; this relationship was not seen comparing persons with controlled treated hypertension with no hypertension (odds ratio 1.01, P = 0.972).
Hypertension was associated with a sparser retinal vascular network, which was similar across different racial/ethnic groups and most apparent in those with uncontrolled or untreated hypertension. These data suggest that microvascular remodelling can be quantified by measuring retinal vasculature.
aDepartment of Ophthalmology, National University Health System
bSingapore Eye Research Institute, Singapore National Eye Centre
cSaw Swee Hock School of Epidemiology and Public Health, National University of Singapore
dDepartment of Medicine, National University Health System, Singapore, Singapore
Correspondence to Professor Tien Y. Wong, Singapore Eye Research Institute, 11 Third Hospital Avenue, Singapore 168751, Singapore. Tel: +65 6322 4584; fax: +65 6323 1903; e-mail: firstname.lastname@example.org
Abbreviations: BP, blood pressure; Df, fractal dimension; ETDRS, Early Treatment for Diabetic Retinopathy Study; HDL, high-density lipoprotein; IRIS, International Retinal Imaging Software; LDL, low-density lipoprotein; MABP, mean arterial blood pressure
Received 1 November, 2012
Revised 18 April, 2013
Accepted 30 April, 2013