Retinal racemose hemangioma is a congenital vascular malformation in which some or all of the retinal vessels are dilated, often to the point that the arterial system cannot be distinguished from the venous system. If the hemangioma is extrafoveal then visual acuity could be normal, but for those with foveal involvement, visual acuity is typically poor. This tumor can be associated with the Wyburn–Mason syndrome in which similar racemose hemangiomas are found in the midbrain, leading to stroke, and in the mandible, leading to profuse bleeding during dental work. These vessels are at risk for venous obstruction, retinal ischemia, and neovascularization.
The term racemose hemangioma describes the occurrence of retinal AV communications without interposed capillaries. This term is partly a misnomer, since the occurrence of hemangiomas, for example, true retinal neoplasms, is not characteristic of these lesions.