caa a22 4500 606158979 CHVBK 20210128100622.0 cr unu---uuuuu 210128e20150101xx s 000 0 eng 10.1007/s00521-014-1657-2 doi (NATIONALLICENCE)springer-10.1007/s00521-014-1657-2 Impact of retinal vascular tortuosity on retinal circulation [Elektronische Daten] [Jihene Malek, Ahmad Azar, Rached Tourki] The retinal microvasculature is a window to the systemic circulation. Systemic diseases, like diabetes and hypertension, are linked to retinal microvascular structure changes (as width, tortuosity, and branching angle). The latter results in a potentially disadvantageous blood flow. This study has been designed to examine the relationship of a retinal vascular tortuosity to both blood pressure and velocity. The geometrical outlines of realistic retinal vascular trees have been extracted from fundus images. The retinal venular tortuosity has been quantitatively measured. A normal tortuosity value has been found, which has not exceeded 1.2. A computational fluid dynamics study has been conducted to examine the effect of topological changes on the hemodynamics distribution in the retinal circulation. The microvascular diameter effect (i.e., Fahraeus-Lindqvist effect) and the hematocrit have been considered in determining the viscosity of the blood in the retinal vessel segments. The pressure drop and the maximum velocity have been in the order of 15mmHg and 0.032m/s for tortuous vessels, and 13mmHg and 0.054m/s for normal vessels, respectively. For a clinical case, the maximal velocity falls down to 14% due to the tortuosity. The current results have shown a decrease in the blood velocity and an increase in the pressure drop with tortuosity, which are in good agreement with in vivo measurements reported in the literature. The Natural Computing Applications Forum, 2014 Blood flow modeling nationallicence Retinal circulation nationallicence Fundus images nationallicence Retinal venous in health and disease nationallicence k : Matched filter kernel nationallicence L : Length of the vessel segment nationallicence σ : Spread of the intensity profile nationallicence d curve : Distance traversed by the vessel (pixels) nationallicence x i , y i : Coordinates of the ith pixel in the vessel segment nationallicence N : Total number point constituent vessel segment nationallicence d straight : Distance between the first and last points of the vessel (pixels) nationallicence Tortuosity : Tortuosity of blood vessels nationallicence v : Blood velocity (m/s) nationallicence p : Pressure (Pa) nationallicence ρ : Density (kg/m3) nationallicence µ : Dynamic viscosity nationallicence µ rel : Relative viscosity nationallicence µ 0.45 : Relative viscosity for a fixed discharge hematocrit nationallicence D : Vessel diameter nationallicence C : Describes the shape of viscosity dependence on hematocrit nationallicence f : Gravity forces nationallicence Malek Jihene Electronics and Micro-Electronic Laboratory (LEME), Monastir University, Route de Kairouan, 5000, Monastir, Tunisia aut Azar Ahmad Faculty of Computers and Information, Benha University, Benha, Egypt aut Tourki Rached Electronics and Micro-Electronic Laboratory (LEME), Monastir University, Route de Kairouan, 5000, Monastir, Tunisia aut Neural Computing and Applications Springer London 26/1(2015-01-01), 25-40 0941-0643 26:1<25 2015 26 521 https://doi.org/10.1007/s00521-014-1657-2 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00521-014-1657-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Malek Jihene Electronics and Micro-Electronic Laboratory (LEME), Monastir University, Route de Kairouan, 5000, Monastir, Tunisia aut NATIONALLICENCE 700 1- Azar Ahmad Faculty of Computers and Information, Benha University, Benha, Egypt aut NATIONALLICENCE 700 1- Tourki Rached Electronics and Micro-Electronic Laboratory (LEME), Monastir University, Route de Kairouan, 5000, Monastir, Tunisia aut NATIONALLICENCE 773 0- Neural Computing and Applications Springer London 26/1(2015-01-01), 25-40 0941-0643 26:1<25 2015 26 521