Peculiar features of Tvrm4 mice are that a) being generated by mutagenesis, they are not transgenics and have normal levels of rhodopsin; and b) they do not show retinal abnormalities if grown in normal ambient light but undergo RP-like retinal degeneration when exposed briefly to strong, white light, which is otherwise innocuous for wild type (wt) controls. Here, RHO is linked to retinal degeneration.