Abstract
Purpose::
To examine variables influencing the calibre of retinal vessels in a population-based sample of 6-year old Australian children. These measurements are shown to predict cardiovascular & other systemic diseases in older adults. Understanding the roles of these factors in childhood could provide useful insights into the genesis of microvascular processes in adults.
Methods::
The Sydney Childhood Eye Survey is a random cluster sampled cross-sectional survey of eye conditions in 4,108 children (2 age groups; 6 and 12 years) attending schools across the Sydney metropolitan area. The current analysis includes 1572 (of 1740) 6-year old children with complete data. Digital retinal photographs (Canon 60UVi) were taken & standardised computer-assisted measurements made of vessel calibre (one eye per child), to determine mean arteriolar & venular diameters. The exam also measured height, weight, blood pressure, and took a detailed birth history (with infant health records).
Results::
Higher blood pressure (BP, systolic or diastolic) was associated with significantly narrower retinal arterioles (by BP quartiles, p for trend <0.0001), but not venules (2.0 microns per 10 mmHg increase in BP, after controlling for confounders). Low birth weight was also associated with narrower retinal arterioles (1.1 microns per 500g decrease). Prematurity & maternal smoking independently contributed to this effect. Body-mass effects were observed, particularly wider venular calibre (2.1 microns for BMI levels above cardiovascular risk threshold). Greater BMI, weight & body surface area predicted wider venules while greater BMI & larger waist circumference predicted narrower arterioles. Among ocular parameters, longer axial length (AL) predited narrower arterioles (3.66 microns per SD increase) while darker iris colour (or non-Caucasian ethnicity, ?surrogate for darker fundus colour), led to wider measured calibres, indicating measurement artifact.
Conclusions::
Our findings suggest that the vascular effects of BP may manifest early in life. Other variables also influence retinal vessel calibre, including birth parameters, body-mass & magnification effects, plus fundus pigmentation. These data provide a comprehensive view of the 'physiological' influences on retinal vessel calibre in young children, that may be relevant to ongoing adult studies of these signs.
Keywords: clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • clinical (human) or epidemiologic studies: risk factor assessment