The retinal pigment epithelium (RPE) interacts closely with photoreceptors, an activity that is essential to maintain excitability of photoreceptors. The RPE helps to control the environment of the subretinal space, supplies nutrients and retinal to the photoreceptors, phagocytoses shed photoreceptor outer segments in a renewal process, and secretes a variety of growth factors, helping to maintain the structural integrity of the retina. Some of these functions are coupled to ion fluxes across cell membranes of the RPE. Since movements of charges across the RPE can be monitored in the electroretinogram (ERG) and electro-oculogram (EOG), these methods provide insights into these RPE functions.

In this chapter, RPE functions involving ion fluxes across RPE cell membranes will be described. The first part will describe ion channels and transporters that are present in the RPE. In the second part, the interaction of ion channels and transporters will be put into models of RPE function.