Selective S-cone ERGs (elicited by blue flashes delivered on a longer wavelength background) can help confirm the diagnosis of enhanced S-cone syndrome (typically related to bi-allelic variants in NR2E3) and demonstrate S-cone preservation in blue cone monochromacy (helping distinguish it electrophysiologically from achromatopsia) [11]. This evidence concerns the gene NR2E3 and achromatopsia.