Vascular dysregulation is a condition in which blood flow is not properly distributed to meet the demands of different tissues and could lead to overperfusion or underperfusion. Vascular dysregulation can be primary (occurring alone) or secondary (associated with other disorders, usually autoimmune diseases), and is caused by an imbalance between vasodilator and vasoconstrictor substances produced mainly locally by the vascular endothelium. In most circumstances of vascular dysregulation, the level of endothelin-1 is increased, leading to vasospasm. Vascular dysregulation is present in at least some subgroups of patients with glaucoma, and in these individuals it might have some important therapeutic consequences. In this article we review the evidence linking vascular dysregulation and glaucoma, and evaluate the clinical characteristics that might suggest the presence of vascular dysregulation in the glaucoma patient.