Effect of axial length on retinal vascular network geometry

PURPOSE: To explore the association between axial length and retinal vascular network geometry (arterio-venous diameter ratio [AVR], arteriolar branching angles, and junctional exponents). DESIGN: Prospective, cross-sectional study. METHODS: Patients were recruited from a pseudophakic population that had preexisting axial length measurements. Mean arterial blood pressure and previous medical history were recorded. Fundal photographs were taken. Digital image analysis was used to determine the AVR, mean arteriolar bifurcation angle, and junctional exponent for each subject. RESULTS: In total, 52 subjects were analyzed. Axial length had no association with AVR (R = -0.01, P = .941), mean angles at arteriolar bifurcations (R = 134, P = .342), or junctional exponents (R = .003, P = .982). However, increased axial length was associated with a trend for lower measured retinal venular and arteriolar diameters (R = -.28, P = .04 and R = -.23, P = .10, respectively). Junctional exponents correlated with both the AVR (R = .32, P = .019) and vascular bifurcation angles (omega) (R = .317, P = .022). CONCLUSIONS: Increased axial length is associated with narrowing of both arteriolar and venular diameters, but not on the AVR, or vessel junctions. Future studies exploring the influence of systemic disease on retinal vascular topography do not need to consider axial length as a potential confounding variable when utilizing measures such as AVR or vessel junctions. Vascular arterliolar junctional exponents may serve as a good measure of overall altered retinal vascular geometry in cardiovascular disease. (Am J Ophthalmol 2005. (c) 2005 by Elsevier Inc. All rights reserved.)