Arteriovenous malformations

Primary vascular malformations of the retina are still a challenge for most retinal clinicians. They conform to a heterogenous group of alterations in the arterial or venous retinal circulation. These morphological changes are decisive in their evolution and clinical manifestations, as well as the location and extension of the vascular malformation. Most of these conditions result from abnormal embryogenesis and could be associated with systemic diseases. Their etiopathogenesis remains unclear. These vascular conditions are usually benign and characterized by mature and competent vessels, but in some cases, a disturbance of homeostasis can cause different alterations, such as retinal hemorrhages. The aim of this chapter is to assess the main characteristics of congenital retinal macrovessels, preretinal vascular loops, familial retinal arteriolar tortuosity and retinal arteriovenous malformations, their pathogenesis, main features in multimodal imaging, and their ocular and systemic associations, which may be life threatening in some cases. This knowledge is essential as they have different management, prognosis, associations, and a wide differential diagnosis. For this purpose, multimodal imaging has a crucial role to understand these pathologies.