The retina is the only tissue in which blood vessels can be visualized non-invasively in vivo. Thus, the study of the retinal hemodynamic has special interest for both physiological and pathological conditions. The aim of this study has been to develop a detailed computational model for a quantitative analysis of the blood flow in physiologically realistic retinal arterial and venous networks. The geometrical outlines of both retinal artery and vein have been extracted from the retinal image acquired from a healthy young adult by a retinal camera Topcon TRC-50EX. The microvascular diameter effect (i.e., Fåhraeus–Lindqvist effect) and the hematocrit have been considered in determining the viscosity of the blood in the retinal vessel segments. The blood moves at a velocity that is 2 times less in the veins (maximum 5.4 cm/s) than the velocity at which it moves in the arteries (maximum 11 cm/s) which are in good agreement with in vivo measurements reported in the literature. The pressure drop has been in the range of 11–14 mmHg between the inlet and outlets for the arterial network, and 13–14 mmHg for the vein network. The developed method can be used as a tool for continuous monitoring of the retinal circulation for clinical assessments as well as experimental studies.