The retina is the primary light detecting tissue in mammals and performs an essential role in vision. The retina is organised into three cellular layers containing six major neuronal cell types, each tasked with performing different functional roles12. Rods and cones of the outer retina detect light, and are modulated by feedback inhibition from horizontal cells. Bipolar cells and amacrine cells of the inner retina modulate and integrate rod and cone driven signals and provide synaptic input to retinal ganglion cells (RGCs) that ultimately project light information to retinorecipient areas of the brain. Müller cells are the major glial cell type of the retina and provide homeostatic and metabolic support for retinal neurons, and may also perform roles in transmission of light to outer retinal photoreceptors34. Like all neuronal tissues, the cells of the retina use changes in membrane potential and intracellular ion concentrations to generate and transmit electrical signals, and ultimately encode visual information. However, the signalling pathways of the retina are highly complex and the precise roles performed by distinct classes of ion channels are currently unknown. Most notably, the K+ ion channels responsible for regulating the resting membrane potential and cellular excitability of retinal ganglion cells (RGCs) remain to be determined. RGCs are the first cells in the visual pathway to encode light as tonic and transient patterns of action potential firing5 and are required to maintain responses over a wide range of light intensities6. The regulation of RGC excitability is therefore fundamental to preventing signal saturation and increasing the dynamic range of the retina. Furthermore, different components of the visual signal are encoded by distinct subtypes of RGC which show characteristically different levels of sustained activity and responses to light (sustained and transient ON, OFF and ON-OFF responses for example)27. However, the mechanisms that set resting membrane potential and regulate these differing levels of tonic and transient activity in RGCs remain to be fully determined89.