Evidence is accumulating that pericyte-containing microvessels, which constitute the largest component of the circulatory system, actively regulate capillary perfusion. Because the retinal vasculature is highly specialized for the local control of blood flow, experimental study of its microvessels is proving useful in the quest to elucidate the mechanisms by which local perfusion is regulated. The microcirculation of the retina is also a focus of considerable attention due to its vulnerability to diabetes, which is a leading cause of vision loss. Based on the premise that the transmembrane movement of ions plays a critical role in regulating the function of pericytes, investigators are using the patch-clamp technique to study these contractile mural cells. This review highlights recent progress made in understanding how ion channels and transporters mediate responses of the retinal microvasculature to vasoactive signals.