Abstract
Light allows us to see. Seeing begins with photoreceptors in the retina where light is absorbed, converted into an electrical response and transmitted to the brain. Photoreception is highly conserved, and in animals, almost exclusively based on a single class of proteins, the opsins. Image-forming information goes to the lateral geniculate nucleus and eventual processing into visual images, sight. What may not be immediately apparent is the transmission of non-image information. However, cells in the skin contain the full set of opsins and their phototransduction cascades which are active, cover the whole solar spectrum and appear to participate in the skin’s protective mechanisms. This is obviously related to collection of non-image information. Why is this system of photoreception and transmission duplicated in the skin and what is its function?