Indeed, more than twenty mutations in the gene GUCA1A encoding for GCAP1 have been associated with autosomal dominant cones or cone-rod dystrophies (CORD) [19,20,21,22,23,24,25,26,27,28,29,30,31,32], while a relatively rare missense mutation found in GUCA1B, encoding for GCAP2, has been associated with retinitis pigmentosa (RP), in some cases with macular involvement [33,34]. Here, GUCA1B is linked to retinitis pigmentosa.