IQCB1 and Leber congenital amaurosis: Therefore, in BCM only the fovea and foveal cone photoreceptor structure would need to be quantified; surrounding extrafoveal retina where rod:cone ratios increase rapidly would not be targeted and, unlike the CEP290 and IQCB1 (NPHP5) forms of LCA previously analyzed, BCM has evidence of normal rod function and structure (Curcio et al., 1990; Cideciyan et al., 2013).