The events following a venous obstruction are poorly known, at the fundamental as well as at the clinical level. Experimental studies are poorly contributive, due to the questionable pertinence relative to the clinical situation. Despite numerous epidemiological studies, there is no strong consensus on the risk factors of RVO, especially the role of coagulation abnormalities, which appear to be modest at best. High blood pressure and glaucoma appears to be involved, however their pathophysiological role remains obscure. Controversies regarding the role of diabetes may be due to the fact that diabetics do more severe forms of RVO, hence a recruitment bias. The natural history of RVO is highly unpredictable at an individual level. Such poor predictibility may arouse from the intertwining of several parameters such as degree and duration of flow obstruction, blood pressure, intensity of microvascular remodelling… The aim of this SIS is to adress some still unanswered questions about RVOs, to point controversies, and to propose new pathways for a better understanding and clinical management of these patients.