PRPH2 and central areolar choroidal dystrophy: CACD usually presents as an autosomal-dominant trait.7 Only two genes, PRPH2 and GUCY2D, have been reported to cause CACD, both of which are expressed exclusively in photoreceptors, just like GUCA1A. 8,10,11,12 In addition, significant thinning to complete loss of the outer nuclear layer of photoreceptors has also been observed in the CACD process.8,30 We therefore raise the hypothesis that CACD represents a severe pattern of maculopathy.