Hemodynamics in the retinal vasculature during the progression of diabetic retinopathy

Purpose: Several studies have established, using various measurement modalities, that progression from diabetes to diabetic retinopathy (DR) is associated with changes in hemodynamics or measurable vascular geometry. In this study, we take vessel measurements from standard fundus images and estimate hemodynamic parameters (which are not directly observable) using a simple hemodynamic model. We show that there are statistically significant changes in some estimated hemodynamic parameters associated with the development of DR.
Methods: A longitudinal study of 24 subjects was conducted. For each subject, four fundus images were used, taken annually during the three years before the appearance of DR and in the first year of DR. A venous and arterial vascular bifurcation, consisting each of a parent vessel and two child branches, was extracted and at the branching nodes a zero dimensional model estimated the fluid dynamic conditions in terms of volumetric blood flow, blood flow velocity, nodal pressure, wall shear stress, and Reynolds number. These features were statistically analyzed using linear mixed models.
Results: A number of parameters, primarily venous, showed significant change with the development of DR, including early change two years before the onset of DR. A large proportion of overall variance is accounted for by individual patient differences, making progressive study essential.
Conclusion: This is the first paper to demonstrate that hemodynamic feature estimates extracted from standard fundus images are sensitive to progression from diabetes to DR. In our future work, we aim to test whether the variations in hemodynamic conditions are predictive of progression prior to the appearance of retinal lesions.