Association of the Fractal Dimension of Retinal Arteries and Veins with Quantitative Brain MRI Measures in HIV-Infected and Uninfected Women

Abstract

ObjectiveThe fractal dimension of retinal arteries and veins is a measure of the complexity of the vascular tree. We hypothesized that retinal fractal dimension would be associated with brain volume and white matter integrity in HIV-infected women.DesignNested case-control within longitudinal cohort study.MethodsWomen were recruited from the Brooklyn site of the Women’s Interagency HIV study (WIHS); 34 HIV-infected and 21 HIV-uninfected women with analyzable MRIs and retinal photographs were included. Fractal dimension was determined using the SIVA software program on skeletonized retinal images. The relationship between predictors (retinal vascular measures) and outcomes (quantitative MRI measures) were analyzed with linear regression models. All models included age, intracranial volume, and both arterial and venous fractal dimension. Some models were adjusted for blood pressure, race/ethnicity, and HIV-infection.ResultsThe women were 45.6 ± 7.3 years of age. Higher arterial dimension was associated with larger cortical volumes, but higher venous dimension was associated with smaller cortical volumes. In fully adjusted models, venous dimension was significantly associated with fractional anisotropy (standardized β = -0.41, p = 0.009) and total gray matter volume (β = -0.24, p = 0.03), and arterial dimension with mean diffusivity (β = -0.33,.p = 0.04) and fractional anisotropy (β = 0.34, p = 0.03). HIV-infection was not associated with any retinal or MRI measure.ConclusionsHigher venous fractal dimension was associated with smaller cortical volumes and lower fractional anisotropy, whereas higher arterial fractal dimension was associated with the opposite patterns. Longitudinal studies are needed to validate this finding.

Peripheral Retinal Imaging Biomarkers for Alzheimer’s Disease: A Pilot Study

“…Despite the lack of measurable FD differences in zone C, we found a decreased FDa when the analysis was extended to the entire image, i.e., encompassing the peripheral retina (Table 2). Recent studies correlated retinal FD with cerebral cortical volumes and found a positive correlation with FDa [43]. As decreased cortical volume has been associated with AD [44-46], changes in FDa in the peripheral retina might be a new prospective biomarker and a surrogate for AD-associated atrophy.…”

Retinal vascular fractal dimension and cerebral blood flow, a pilot study

“…where DM is the signal intensity mean difference between label and control The central retinal artery/vein equivalent (CRAE and CRVE) summarizes the six largest arteries and veins. We used the revised formulas given in Knudtson et al (Crystal et al 2016). in zone B Curvate tortuosity Integral of the curvature squared along the vessel path, normalized by the total path length.…”

“…A previous study among HIV-infected patients found an association between retinal vessels FD and quantitative brain MRI measures in diffusion tensor imaging (Crystal et al 2016). High venous FD was associated with small cortical volumes and low fractional anisotropy, with high arterial FD associated with the opposite patterns (Crystal et al 2016).…”

Comparison of retinal vascular geometry in obese and non-obese children

“…Based on the optimum design principle, the architecture of the human microvasculature is designed to be energy-efficient, i.e, to provide adequate perfusion with the minimum of energy expenditure [ 21 ]. Retinal vascular geometry not only reflects the complexity of the vascular tree, but also provides insight into the ‘optimality’ of the microcirculation [ 22 ]. Retinal vascular caliber has previously been shown to be abnormal in obese adults [ 23 ].…”