To examine TCS in the absence of retinal degeneration, we measured retinal TCS in a rhodopsin heterozygous mouse model (Rho+/− mice; Lem et al., 1999), which has reduced rod collecting areas (see Table 1) and accelerated rod recovery kinetics but no degeneration before ∼P90–P120 (Fig. 3A–C; Lem et al., 1999; Calvert et al., 2001; Liang et al., 2004). This evidence concerns the gene RHO and retinal degeneration.