Determinants of retinal microvascular architecture in normal subjects

Abstract

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.

Figure 1

Retinal microvascular analysis. The figure shows a typical digitized retinal image viewed in the analysis program after tracking and measurement of several arteriolar trees. An enlargement of one region is shown to illustrate the measured parameters. D₀ = parent diameter, D₁ = 1^st offspring diameter, D₂ = 2^nd offspring diameter, ω = branching angle, L = vessel segment length.