Purpose: To measure the wall-to-lumen ratio (WLR) and the cross-sectional area of the vascular wall (WCSA) of retinal arterioles by an Adaptive Optics (AO) retinal camera.
Methods: Forty-seven human subjects were examined and their medical history was explored. WLR and WCSA were measured on the basis of retinal arteriolar wall thickness (VW), lumen diameter (LD) and vessel diameter (VD) assessed by rtx1 Adaptive Optics retinal camera. WLR was calculated by the formula [Formula: see text]. Arterio-venous ratio (AVR) and microvascular abnormalities were attained by quantitative and qualitative assessment of fundus photographs. Influence of age, arterial hypertension, body mass index (BMI) and retinal microvascular abnormalities on the WLR was examined. An age-adjusted WLR was created to test influences on WLR independently of age. Considering WLR and WCSA, a distinction between eutrophic and hypertrophic retinal remodeling processes was possible.
Results: The intra-observer variability (IOV) was 6 % ± 0.9 for arteriolar wall thickness and 2 % ± 0.2 for arteriolar wall thickness plus vessel lumen. WLR depended significantly on the wall thickness (r = 0.715; p < 0.01) of retinal arterioles, but was independent of the total vessel diameter (r = 0.052; p = 0.728). WLR correlated significantly with age (r = 0.769; p < 0.01). Arterial hypertension and a higher BMI were significantly associated with an increased age-adjusted WLR. WLR correlated significantly with the stage of microvascular abnormalities. 55 % of the hypertensive subjects and 11 % of the normotensive subjects showed eutrophic remodeling, while hypertrophic remodeling was not detectable. WLR correlated inversely with AVR. AVR was independent of the arteriolar wall thickness, age and arterial hypertension.
Conclusions: The technique of AO retinal imaging allows a direct measurement of the retinal vessel wall and lumen diameter with good intra-observer variability. Age, arterial hypertension and an elevated BMI level are significantly associated with an increased WLR. The wall-to-lumen ratio measured by AO can be used to detect structural retinal microvascular alterations in an early stage of remodeling processes.
Keywords: Adaptive optics; Arterio-venous ratio; Arteriolar remodeling; Cross-sectional area of the vascular wall; Hypertension; Retinal microvascular alterations; Wall-to-lumen ratio.