The data show key roles for endogenous Dhh signalling in maintenance and regeneration of the corneal epithelium, demonstrate an interaction between Pax6 and Hh signalling in the corneal epithelium, and show that failure of Hh signalling pathways is a feature of Pax6+/- corneal disease that cannot be remedied pharmacologically by addition of the ligands. The gene discussed is DHH; the disease is corneal disorder.