Regulatory mechanisms in the retinal and choroidal circulation.

The retina receives its nutrients from two separate circulations: retinal and choroidal circulation. This short overview describes the determinants in the regulation of these circulations. Retinal circulation is characterized by a low blood flow while flow in the choroid is high. The choroidal circulation is mainly controlled by sympathetic innervation and is not autoregulated. Retinal circulation lacks autonomic innervation, shows an efficient autoregulation and is mainly influenced by local factors. Local mediators released by endothelial cells and surrounding retinal tissue also have a substantial role in the regulation of retinal circulation.