It may be interesting to test whether Europeans with SNPs in SLC24A4 (i.e. people with blue/green eyes and blond hair) or those individuals with Amelogenesis Imperfecta, caused by a nonsense SLC24A4 mutation (Herzog et al., 2015), have subtle abnormalities in cone vision, such as altered ERG flicker fusion frequency, confirming the functional importance of NCKX4 in humans. Here, SLC24A4 is linked to amelogenesis imperfecta.