Acts as a receptor for sonic hedgehog (SHH), indian hedgehog (IHH) and desert hedgehog (DHH). Associates with the smoothened protein (SMO) to transduce the hedgehog's proteins signal (By similarity). In the eye, detected in neural retina, iris, retinal pigment epithelium, but not in lens. Activated by Sonic hedgehog. Glycosylation is necessary for SHH binding. Belongs to the patched family.