To better determine the pathogenesis of GUCA1A p.R120L and to explain the phenotypic diversity caused by GUCA1A mutations, we introduced another previously reported mutation, p.D100E, which was reported to be correlated with cone dystrophy.22,23 This mutation, situated in the calcium-binding loop of the third EF hand, was conserved among all tested species (Figure 3a,b). The gene discussed is GUCA1A; the disease is cone dystrophy.