Recently, central serous chorioretinopathy has been understood to be part of the pachychoroid spectrum. In pachychoroid spectrum disorders, of which CSR represents stage II, the choroid, the highly vascularized layer below the retina, is thickened and congested with increased blood vessel diameter, especially in the deep choroid (the so-called Haller's layer). This results in increased pressure from the deep choroid against the superficial choroid close to the retina, damaging the fine blood vessels (capillaries) needed to supply oxygen and nutrients to the retinal pigment epithelium and retina. Additionally, fluid can leak from these damaged vessels and accumulate under the retina.