Calcium, potassium:sodium antiporter that transports 1 Ca(2+) and 1 K(+) in exchange for 4 Na(+) (PubMed:26631410). Critical component of the visual transduction cascade, controlling the calcium concentration of outer segments during light and darkness (PubMed:20850105). Light causes a rapid lowering of cytosolic free calcium in the outer segment of both retinal rod and cone photoreceptors and the light-induced lowering of calcium is caused by extrusion via this protein which plays a key role in the process of light adaptation (PubMed:20850105). Ca(2+)(out) + K(+)(out) + 4 Na(+)(in) = Ca(2+)(in) + K(+)(in) + 4 Na(+)(out) Expressed in the retina, particularly in the inner segment, outer and inner nuclear layers, and ganglion cell layer. The uncleaved signal sequence is required for efficient membrane targeting and proper membrane integration. The disease is caused by variants affecting the gene represented in this entry. Belongs to the Ca(2+):cation antiporter (CaCA) (TC 2.A.19) family. SLC24A subfamily.