Prostaglandins (PG) are known to alter regional ocular blood flow and exhibit vasoactive properties in isolated ocular blood vessels. A variety of animal experiments indicate that endogenous PGs play a role in the regulation of retinal (RBF) and choroidal (ChBF) blood flow. There is also evidence that the prostaglandin pathway is involved in the activation of NO production in humans, however, the mechanisms for interactions between PG and NO in ocular vasculature are still unclear.