Treatment here with low dose AAV-M3.M5H.RHOM3/5R by contrast resulted in a significant slowing of retinal degeneration in the Nrl.GFP/+, RhoP23H/+ mouse as recorded by SD-OCT (Fig. 6a, b), cSLO fluorescence imaging (Fig. 6c) and ERG (Fig. 6d, e), an effect which was not observed when the equivalent but mirtronless AAV-RHO vector was injected at the same dose (Fig. 6f). The gene discussed is NRL; the disease is retinal degeneration.