Retinal Vascular Fractal Dimension and Its Relationship With Cardiovascular and Ocular Risk Factors

PURPOSE: To examine the influence of a range of cardiovascular risk factors and ocular conditions on retinal vascular fractal dimension in the Singapore Malay Eye Study. DESIGN: Population-based cross-sectional study. METHODS: Fractal analysis of the retinal vessels is a method to quantify the global geometric complexity of the retinal vasculature. Retinal vascular fractal dimension (D-f) and caliber were measured from retinal photographs using a computer-assisted program. D-f and arteriolar caliber were combined to form a retinal vascular optimality score (ranging from 0 to 3). Data on cardiovascular and ocular factors were collected from all participants based on a standardized protocol. RESULTS: Two thousand nine hundred thirteen (88.8% of 3280 participants) persons had retinal photographs of sufficient quality for the measurement. The mean D-f was 1.405 (standard deviation, 0.046; inter-quartile range, 1.243 to 1.542). In the multiple linear regression analysis, after controlling for gender, serum glucose, intraocular pressure, anterior chamber depth, and retinal vascular caliber, smaller Df was associated independently with older age (standardized regression coefficient [s beta] = -0.311; P < .001), higher mean arterial blood pressure (s beta = -0.085; P < .001), a more myopic spherical equivalent (s beta = 0.152; P < .001), and presence of cataract (s beta = -0.107; P < .001). Retinal vascular optimality score was associated significantly with higher mean arterial blood pressure (P > .001 for trend).