Response families of transretinal ERG recordings from wild type (A), Grk1−/− (B), Rpe65−/− (C and E) and Rpe65−/−Grk1−/− (D and F) mice. Responses in E and F were recorded after application of 11-cis retinal. Flashes of white light were delivered at time 0 in 0.5 log incremental steps except for the last three traces in (C) which were delivered in two-fold increments by doubling the flash duration. The dimmest flashes were delivered at -1.5 log (C and D), and -4.5 log (A, B, E, and F) unit attenuation.