Influence of refractive error and axial length on retinal vessel geometric characteristics.

PURPOSE To evaluate the influence of refractive error and axial length (AL) on retinal vascular network geometry measurements in an adult Asian population. METHODS This was a population-based, cross-sectional study on 2882 persons with diabetes in the Singapore Malay Eye Study. Spherical equivalent refraction was assessed using an autokeratorefractometer and subjective refraction. AL retinal vascular caliber, tortuosity, and branching characteristics were quantified from retinal fundus photographs using a semiautomated computer-assisted program according to a standardized protocol. RESULTS In multivariate analyses adjusting for age, sex, education, smoking, blood pressure, diabetes status, and antihypertensive medication use, longer AL and more myopic refraction were associated with narrower retinal arterioles and venules (P ≤ 0.001 for all) and less tortuous (straighter) arterioles (P < 0.001 for both). Longer AL and more myopic refraction were also associated with increased branching coefficients in both arterioles (P < 0.001 for both) and venules (P = 0.02 and P < 0.001, respectively). Longer AL and more myopic refraction were associated with more acute branching angles in arterioles (P < 0.001 for both) but not venules. CONCLUSIONS Myopic refractive errors and longer AL are associated with narrower retinal arterioles and venules, less tortuous arterioles, and increased branching coefficients in both arterioles and venules. These findings provide insights into ocular blood flow in myopia and also suggest that future studies evaluating these retinal parameters should account for the influence of AL and refractive error.