PDE6B and retinal degeneration: Finally, while neurochemical changes have been described both at early and late stages of degeneration in the rd1 mouse, as well as in other models of retinal degeneration (Fletcher and Kalloniatis, 1996, 1997; Marc et al., 2003; Jones and Marc, 2005; Gibson et al., 2013), the underlying cause and relationship between the different forms of inner retinal change is not clear.