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We numerically study the fluid dynamics of oil tamponade in models of vitrectomized eyes prompted by a subset of daily activities corresponding to movements on the horizontal plane with the patient in a standing position. Bulk flow features are related to near-wall flow topology and transport at the retinal surface through a wall shear-stress-based analysis. Proliferative VitreoRetinopathy (PVR) is the leading cause of retinal re-detachment occurring in about 20% of all cases due to the accumulation of inflammatory cells in discrete retinal regions. Signalling soluble mediators stimulate inflammatory cells' chemotaxis and studying their distribution across the retinal surface may acquire clinical relevance. In all the investigated cases, persistent and elongated regions along the retina, potentially prone to accumulate chemo-attractants and cells are observed. Gradients of soluble inflammation mediators present in the aqueous are known responsible for the so-called epithelial-mesenchymal transition that initiates PVR and favours recurrent retinal detachment prompting the proliferation of inflammatory cells with collagen matrix deposition and its contraction. The surgical apposition of encircling scleral buckling elements, known for over a century to influence PVR formation and localization, modifies the attracting regions, possibly causing an accumulation of molecules and cells along approximately vertical lines that follow the rising menisci due to the cerclage indentation. The resulting spatial pattern is compatible with clinical observations. This study may open toward rational analyses of near-wall transport to predict PVR pathogenesis by relating biochemical accumulation in certain areas of the retina to clinical conditions. [ABSTRACT FROM AUTHOR]

Aneurysms are abnormal expansion of weakened blood vessels which can be debilitating or fatal upon rupture. Previous studies have shown that hemodynamics play a role in aneurysm formation, growth and rupture. Therefore, the objective of this work is to investigate the impact of flow structures on vortex strength, impinging location, and wall shear stress for two aneurysm models. For this study, experiments were performed on two different, idealized, rigid, and saccular aneurysm models characterized by B F ratios of 1.0 and 1.6. The vortical structures formation and movement were altered by changing peak Reynolds number (R e p ) from 50 and 270 and Womersley number (α) from 2, and 5 on both aneurysm models. Velocity field measurements were performed on the mid-plane location of the aneurysm models using Particle Image Velocimetry (PIV). The results showed presence of vortical structures which formed, grew, and dissipated at different phases in the flow cycle. The behavior of these vortical structures impacted the impinging locations where increased frequency of impingement points at the distal neck could be seen for α = 5 than α = 2 flow scenarios. The wall shear stress results showed that the distal neck experienced elevated stresses during the vortex formation phases of the flow cycle for B F = 1. 0 and 1.6 models. • Reynolds number influences the flow structures in the saccular aneurysm model. • Flow structures play a role in the impinging location. • Flow structures play a role in modifying the wall shear stresses. • For high Reynolds number impinging locations are concentrated near the distal neck. [ABSTRACT FROM AUTHOR]