EDN1 and retinal degeneration: Conversely, the reduction in oxygen demand of the degenerating photoreceptors will subsequently result in reduced blood flow to the retina and the choroid, which is called primary vascular dysregulation in RP patients.[20,21] Additionally, RP has been associated with an imbalance in oxidant/antioxidant status and subclinical inflammatory processes that may stimulate the excessive production of endothelin-1 (ET-1).[16,19] Therefore, retinal degeneration and choroidal thinning in patients with RP seem to interact with each other.